CN100433447C - Power storage system, regenerative power storage system and automobile - Google Patents

Abstract

The present invention provides a regenerative power storage system that reduces battery expansion during rapid charging in a high-temperature environment, such as regenerative charging in a high-temperature environment. It is characterized in that it includes: a battery pack (3) that uses a non-aqueous electrolyte storage battery as a unit unit and is charged by regenerative power, and the non-aqueous electrolyte storage battery has a negative electrode layer containing a lithium-titanium composite oxide; The negative electrode of the electric body; when the temperature _of the above-mentioned battery pack is greater than or equal to 45°C and less than or equal to 90°C, the charge control device (4 ), where V ₀ represents the maximum end-of-charge voltage (V) of the unit cell when the battery pack is fully charged at 25°C, 0.85×V ₀ ≤V ₁ ≤0.96×V ₀ (1).

Description

Power storage system, regenerative power storage system and automobile

technical field

The present invention relates to a battery system suitable for regenerative power storage systems used in automobiles (motor vehicles), motorcycles, trains, elevators, wind power generation, etc. for the purpose of improving energy efficiency.

Background technique

In recent years, in order to effectively utilize energy and effectively utilize renewable energy in accordance with environmental measures, hybrid vehicles (automobiles), two-wheeled vehicles, trains, elevators, wind power generation, etc. equipped with batteries have been studied and some of them have been put into practical use. . Batteries that have been put into practical use and installed so far are lead storage batteries and nickel metal hydride batteries.

However, nickel metal hydride batteries used for hybrid vehicles, for example, have a problem that they generate heat rapidly at high output or during rapid charging (regeneration), and cause significant thermal deterioration.

Therefore, studies are being made on nickel-metal hydride batteries to install lithium-ion batteries that are less thermally degraded and can reduce the weight and thickness of battery packs. However, there is a problem of battery expansion and deformation in high-temperature environments such as summer.

Patent Document 1 describes a charge and discharge control device including a device that controls charge and discharge power so as not to exceed a predetermined upper limit of charge and discharge power that changes in accordance with the temperature when the temperature of the storage battery is equal to or higher than a predetermined temperature. value.

Patent Document 1: JP-A-2003-219510

Contents of the invention

An object of the present invention is to provide a regenerative power storage system and a power storage system that reduce battery expansion during rapid charging in a high-temperature environment such as regenerative charging in a high-temperature environment, and a power storage system comprising the above-mentioned regenerative power storage system or the above-mentioned power storage system. A car (automatic car) with an electric storage system.

The power storage system for regeneration of the present invention is characterized in that it includes: a battery pack that uses a non-aqueous electrolyte storage battery as a unit cell and is charged by regenerative power. The non-aqueous electrolyte storage battery has a negative electrode layer containing lithium titanium composite The negative electrode of the current collector of the above-mentioned negative electrode layer; when the temperature of the above-mentioned battery pack is greater than or equal to 45°C and less than or equal to 90°C, the maximum charge termination voltage V ₁ (V) of the above-mentioned unit unit is controlled within the range of the following formula (1) charge control unit,

0.85×V ₀ ≤V ₁ ≤0.96×V ₀ (1)

Here, V ₀ represents the maximum end-of-charge voltage (V) of the unit cell when the battery pack is fully charged at 25°C.

The power storage system of the present invention is characterized in that it includes a unit cell battery pack composed of a non-aqueous electrolyte storage battery including a negative electrode layer containing a lithium-titanium composite oxide, and a current collector on which the negative electrode layer is placed. negative electrode, positive electrode, and nonaqueous electrolyte; a temperature sensor for measuring the temperature of the above-mentioned battery pack; a voltmeter for measuring the voltage of the above-mentioned unit unit; when the temperature of the above-mentioned battery pack is greater than or equal to 45°C and less than or equal to 90°C, the A charge control device in which the maximum charge termination voltage V ₁ (V) of the unit cell is controlled within the range of the following formula (1),

0.85×V ₀ ≤V ₁ ≤0.96×V ₀ (1)

Here, V ₀ represents the maximum end-of-charge voltage (V) of the unit cell when the battery pack is fully charged at 25°C.

An automobile (automobile) according to the present invention is characterized by comprising the above-mentioned power storage system for regeneration or the above-mentioned power storage system.

In the above-mentioned regenerative power storage system or the above-mentioned power storage system, it is preferable that the charging control device terminates the maximum charging while controlling the charging capacity of the battery when the temperature of the battery pack is 45°C or higher and 90°C or lower. The voltage V ₁ (V) is controlled within the range of the above formula (1).

In addition, according to the present invention, there is provided a power storage system for regeneration, which is characterized in that it includes: a battery pack that uses a non-aqueous electrolyte storage battery as a unit cell and is charged by regenerative power, and the non-aqueous electrolyte storage battery has a Negative electrode layer, a negative electrode including a current collector carrying the above-mentioned negative electrode layer; when the temperature of the above-mentioned battery pack is greater than or equal to 45° C. and less than or equal to 90° C., the amount of charge is controlled so that the charge termination voltage V ₁ (V) of the above-mentioned unit unit satisfies the following The charging control device of formula (1),

0.85×V ₀ ≤V ₁ ≤0.96×V ₀ (1)

Here, V ₀ represents the end-of-charge voltage (V) of the unit cell when the battery pack is fully charged at 25°C.

According to the present invention, it is possible to provide a regenerative power storage system and a power storage system that reduce battery expansion during rapid charging in a high-temperature environment such as regenerative charging in a high-temperature environment, a power storage system including the above-mentioned regenerative power storage system, or the above-mentioned power storage system. system car.

Description of drawings

FIG. 1 is a schematic diagram showing a regenerative storage system according to an embodiment of the present invention.

Fig. 2 is a partially sectional perspective view showing unit cells constituting the battery pack in Fig. 1 .

Fig. 3 is a flowchart showing the operation of the power storage system for regeneration in Fig. 1 .

Fig. 4 is a block diagram showing the detailed relationship between the battery pack and the battery control unit of Fig. 1 .

FIG. 5 is an exploded perspective view of a battery pack used in the storage battery systems of Embodiments 1 and 2. FIG.

FIG. 6 is a block diagram showing an electrical circuit of the battery pack of FIG. 5 .

Fig. 7 is a partially sectional perspective view schematically showing another example of a flat non-aqueous electrolyte secondary battery used in the battery pack of Fig. 5 .

FIG. 8 is an enlarged cross-sectional view of part A of FIG. 7 .

Detailed ways

(Example 1)

The inventors of the present invention have studied the problem that, when regenerative charging is performed on a battery pack of a non-aqueous electrolyte storage battery having a negative electrode containing a lithium-titanium composite oxide in the negative electrode active material, if the depth of charge continues to increase at a high temperature, the battery pack will be damaged. The reason for the expansion is that the lithium-containing unit of the lithium-titanium composite oxide is displaced to the side, and at the same time the reduction and decomposition unit of the non-aqueous solvent in the non-aqueous electrolyte is displaced to the main side, and the potential difference between the two sides is reduced. The reaction of titanium composite oxide produces gas.

Therefore, it has been found that the maximum charge termination voltage V1 (V) in the closed circuit of the above-mentioned unit cell satisfies the following formula (1) by controlling the charge amount when the temperature of the battery pack is 45° C. or more and 90° C. or less. , thereby reducing the battery pack expansion of the regenerative power storage system.

0.85×V ₀ ≤V ₁ ≤0.96×V ₀ (1)

Here, V ₀ represents the maximum end-of-charge voltage (V) in the closed circuit of the unit cell when the battery pack is fully charged at 25°C. Here, the fully charged state refers to charging to the rated capacity of the battery pack. The rated capacity of the battery pack refers to the discharge capacity that is discharged at a current value equivalent to the designed charge capacity of 0.2CmA.

Both the maximum end-of-charge voltage V1 and the maximum end-of-charge voltage V0 are voltage values of a unit cell representing the maximum end-of-charge voltage among all the unit cells constituting the battery pack.

Since the capacity and resistance of the unit cells constituting the battery pack described above are distributed, there is a difference in the charging voltage of the unit cells when the battery pack is fully charged. Therefore, the charge voltage of a unit cell with a small capacity or a large resistance tends to become the maximum end-of-charge voltage. Therefore, in order to maintain the high life performance of the storage battery system, it is important to control at the maximum end-of-charge voltage of the unit cell.

When the maximum end-of-charge voltage V1 (V) exceeds 0.96×V0, the difference between the lithium-containing unit of the lithium-titanium composite oxide and the reduction-decomposition unit of the non-aqueous solvent decreases, a large amount of gas is generated, and the battery pack swells. On the other hand, if the maximum end-of-charge voltage V1 (V) is less than 0.85×V0, the charging capacity will be insufficient and the output characteristics of the battery pack will decrease. For the above reasons, the maximum end-of-charge voltage V1 (V) is defined within the range of the above formula (1). A more desirable range is 0.9×V0≦V1≦0.96×V0.

By using aluminum foil or aluminum alloy foil as the negative electrode current collector, the heat dissipation of the negative electrode can be improved, and the uniformity of temperature distribution in the unit cell can be improved, so the temperature dispersion within the unit cell and the temperature dispersion between the unit cells can be reduced , can improve the charge-discharge cycle life of the battery pack. If the rated capacity of the unit cell increases, the distribution of heat tends to deviate, so in this case, it is more effective to use an aluminum foil or an aluminum alloy foil.

In addition, by using an aluminum foil with an average crystal particle diameter of 50 μm or less or an aluminum alloy foil with an average crystal particle diameter of 50 μm or less as the negative electrode current collector, the exothermic properties and chemical stability of the negative electrode can be improved, thereby further reducing the The amount of gas generated during regenerative charging.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 .

Fig. 1 is a schematic view showing a regenerative power storage system 1, a power storage system 101, and an automobile (automobile) 102 according to an embodiment of the present invention, and Fig. 2 is a partial sectional perspective view showing unit cells constituting the battery pack in Fig. 1 , FIG. 3 is a flowchart showing the operation of the regenerative power storage system in FIG. 1, and FIG. 4 is a block diagram showing the detailed relationship between the battery pack and the battery control unit in FIG. 1.

This regenerative power storage system 1 is mainly composed of a power storage system 101 , and a motor and generator 5 , and the motor and generator 5 are connected to wheels 103 of an automobile 102 via axles 104 and the like. In addition, to drive the wheels 103 of the automobile 102, the electric motor and the electric motor part of the generator 5 may be used for driving, or the internal combustion engine 105 may be used for driving simultaneously as in a hybrid vehicle. The power storage system 101 includes a boost mechanism 2 , a battery pack 3 connected to the boost mechanism 2 , and a battery control unit (BMU) 4 connected to the battery pack 3 . The battery pack 3 uses a thin non-aqueous electrolyte storage battery as a unit cell, and includes a module in which a plurality of unit cells are connected in series or in parallel. Fig. 2 shows an example of a thin non-aqueous electrolyte storage battery. The electrode group 1 has a helically convoluted structure such that the positive electrode 12 and the negative electrode 13 have a flat shape with a separator 14 interposed therebetween. For example, the electrode group 11 is fabricated by applying heat and pressure after the positive electrode 12 and the negative electrode 13 are helically turned into a flat shape with the separator 14 interposed therebetween. The positive electrode 12, the negative electrode 13, and the separator 14 of the electrode group 11 may be integrated by an adhesive polymer. The strip-shaped positive terminal 15 is electrically connected to the positive electrode 12 . On the other hand, the strip-shaped negative terminal 16 is electrically connected to the negative electrode 13 . This electrode group 11 is housed in a container 17 made of a laminated film with the ends of the positive terminal 15 and the negative terminal 16 protruding from the container 17 . In addition, the laminated film container 17 is sealed by heat sealing.

As shown in FIG. 4, the battery control unit (BMU) 4 is provided with: a temperature sensor (for example, a thermocouple, a thermistor, etc.) 6 for measuring the temperature of the battery pack 3; Voltmeter 7; Ammeter 8 for measuring the current of the battery pack; Charge and discharge control circuit 9a; Charge cutoff circuit 9b; Discharge cutoff circuit 9c.

The charge and discharge control circuit 9 a receives the respective measurement results of the temperature sensor 6 , the voltmeter 7 and the ammeter 8 . Based on this input signal, a signal can be input to the charging cutoff circuit 9b and the discharge cutoff circuit 9c, and charge and discharge of the battery pack 3 can be controlled. Specifically, the charge and discharge control circuit 9a sets the state of charge (SOC) based on the measurement result, and sends the result to the charge cutoff circuit 9b and the discharge cutoff circuit 9c. The charging cutoff circuit 9b or the discharge cutoff circuit 9c can calculate the charging capacity necessary to obtain the set SOC. In the case of FIG. 1, the calculation is performed by the charging cutoff circuit 9b. The calculation result is sent to the charge and discharge control circuit 9a. When the charging capacity of the battery pack 3 reaches a predetermined value, a signal is input from the charge and discharge control circuit 9a to the charge cutoff circuit 9b and the discharge cutoff circuit 9c, charging and discharging are stopped, and the SOC can be controlled to a predetermined value. value.

Such a regenerative power storage system 1 is connected to a DC motor and a generator 5 of an automobile (automobile) as loads. Examples of automobiles include two-wheel to four-wheel hybrid cars, electric cars, and the like. The generator connected to the DC motor is connected to the booster mechanism 2 of the regenerative power storage system. The booster mechanism 2 functions as a charger that supplies regenerative power to the battery pack 3 . On the other hand, the DC motor is connected to the BMU4 of the regenerative storage system. Accordingly, the output from the assembled battery 3 to the DC motor can be controlled in accordance with the signals from the charging cutoff circuit 9b and the discharge cutoff circuit 9c.

The operation of the regenerative power storage system 1 will be described with reference to FIG. 3 .

Electric power generated by a generator by driving a DC motor of a hybrid vehicle or the like is boosted by a voltage boosting mechanism 2 and supplied to a battery pack 3 . When the battery pack 3 is charged (input), the temperature sensor 6 of the BMU 4 of the regenerative power storage system 1 monitors the temperature of the battery pack 3 (S1), and sends the result to the charge and discharge control circuit 9a at any time. In the charging and discharging control circuit 9a, if the temperature of the battery pack 3 is less than 45° C., charging is performed until it is fully charged or reaches a predetermined state of charge (SOC), and the charging is terminated (S2). Also, when the temperature of the battery pack 3 exceeds 90° C., a signal is sent to the charging cutoff circuit 9 b and the discharge cutoff circuit 9 c, and charging (input) and discharging (output) are in a standby (stop) state ( S3 ). As a result, the battery stopped generating heat, and the battery temperature cooled down to less than 45°C. Ideally, the battery pack 3 is cooled to 30° C. or less.

On the other hand, when the temperature of battery pack 3 is 45° C. or higher and 90° C. or lower ( S4 ), a signal to start charging (input) or discharging (output) is sent from BMU 4 to battery pack 3 . Thereby, it is possible to control to a predetermined state of charge (SOC) while keeping V1 within the range of the above-mentioned formula (1). Ideally, the specified state of charge (SOC) is 60-90% of full charge.

In the BMU 4, the voltage and current of the battery pack 3 and the unit cells are monitored (S6). In the charging and discharging control circuit 9a, the maximum charging termination voltage V1 in the closed circuit of the unit cell is compared with the maximum charging termination voltage V1 previously input to the BMU4, and the maximum charging termination voltage V1 reaches the range of the above formula (1). A signal is output to the charging cut-off circuit 9a at the time of 1 (S7), and the charging is terminated (S8).

According to the above system, the maximum end-of-charge voltage V1 of the unit cell can be kept within the range of the above formula (1), and the temperature rise of the battery pack being charged can be suppressed, so that expansion of the battery pack being charged can be suppressed. In addition, since the charging capacity is controlled by discharging, the system is not complicated, and the maximum end-of-charge voltage V1 can be reliably maintained within the range of the above-mentioned formula (1).

In addition, although a cooling fan is not installed in the regenerative power storage system shown in FIG. 1 above, a cooling fan or the like may be introduced to cool the battery pack. In this case, it is more desirable to control to a predetermined state of charge (SOC) such that the temperature of the battery pack 3 is not less than 45° C. and not more than 60° C. and V1 is within the range of the formula (1). When the temperature of the battery pack exceeds 60°C, it is desirable to put the charging and discharging into a standby (stopped) state and cool the battery pack to 30°C or less. Through this control, it is possible to further improve the life performance of the battery pack while suppressing a decrease in output performance.

In addition, instead of the DC motor, an AC motor may be used. However, a rectifier is required in this case.

Next, the negative electrode, positive electrode, separator, nonaqueous electrolyte, and container of the thin nonaqueous electrolyte secondary battery will be described.

(1) Negative electrode

The negative electrode has a negative electrode current collector; the negative electrode layer is placed on one or both sides of the negative electrode current collector and contains a negative electrode active material, a conductive agent and a binder.

As the negative electrode active material, a material containing a lithium-titanium composite oxide was used. Examples of lithium-titanium composite oxides include lithium titanate (for example, spinel-type Li _4+x Ti ₅ O ₁₂ , where x is -1≤x≤3, ideally 0<x<1) and the like. In terms of cycle performance, lithium titanate is particularly preferable. This is because lithium titanate has a lithium content unit of about 1.5 V, and is an electrochemically very stable material for an aluminum foil current collector or an aluminum alloy foil current collector.

As the lithium-titanium composite oxide, in addition to the above-mentioned spinel-type lithium titanate, for example, orthorhombic-type lithium titanate such as Li _2+x Ti ₃ O ₇ (x is -1≤x≤3) can also be used. . Spinel-type lithium titanate and orthorhombic-type lithium titanate are collectively referred to as lithium titanium oxide. As the lithium-titanium composite oxide, besides the lithium-titanium oxide, a titanium-based oxide not containing lithium can also be used. Examples of titanium-based oxides include metal composite oxides containing at least one element selected from the group consisting of TiO ₂ , Ti, and P, V, Sn, Cu, Ni, and Fe. Ideally, TiO ₂ is an anatase-type low-crystallinity material whose heat treatment temperature is 300 to 500°C. Examples of metal composite oxides containing at least one element selected from the group consisting of TiO ₂ , Ti, and P, V, Sn, Cu, Ni, and Fe include TiO ₂ -P ₂ O ₅ , TiO ₂ -V ₂ O ₅ , TiO ₂ -P ₂ O ₅ , -SnO ₂ , TiO ₂ -P ₂ O ₅ -MeO (Me is at least one element selected from the group consisting of Cu, Ni, and Fe), etc. . It is desirable that the metal composite oxide has a microstructure with low crystallinity, coexistence of a crystalline phase and an amorphous phase, or the presence of an amorphous phase alone. With such a microstructure, the cycle performance can be greatly improved. Among them, metal composite oxides containing at least one element selected from the group consisting of lithium titanium oxide, Ti, and P, V, Sn, Cu, Ni, and Fe are desirable.

For the negative electrode active material, other types of negative electrode active materials may be included in addition to the lithium-titanium composite oxide. Examples of other negative electrode active materials include carbon materials that contain and release lithium.

It is desirable that the average particle diameter of the negative electrode active material is 1 μm or less. By using a negative electrode active material having an average particle diameter of 1 μm or less, cycle performance can be improved. It is particularly effective during rapid charging and high output discharge. This is because, for example, for a negative electrode active material that contains and releases lithium, the smaller the particle diameter is, the shorter the diffusion distance of lithium ions inside the active material is, and the larger the proportional surface area is. More desirably, the average particle diameter is equal to or less than 0.3 μm. However, if the average particle diameter is small, the particles are likely to aggregate and the uniformity of the negative electrode may decrease, so the lower limit is preferably 0.001 μm or more.

Ideally, by reacting and synthesizing the raw material of the active material, a powder of 1 μm or less is produced as an active material precursor, and the powder after firing is pulverized to a size of 1 μm or less using a pulverizer such as a ball mill or a jet mill. , so as to obtain a negative electrode active material with an average particle diameter less than or equal to 1 μm.

The particle diameter of the negative electrode active material is measured by the following method: using a laser diffraction particle distribution measuring device (Shimadzu SALD-300), first add about 0.1g of the sample, surfactant, 1 to 2mL of distilled water to the beaker and fully stir After that, it was poured into a stirring water tank, and the return light intensity distribution was measured at 2-second intervals to analyze the particle distribution data.

It is desirable to form the negative electrode current collector with aluminum foil or aluminum alloy foil. In addition, it is desirable that the average crystal grain diameter of the aluminum foil or aluminum alloy foil is 50 μm or less. More desirably, the average crystal particle diameter is equal to or less than 10 μm. In order to obtain superior electrical conductivity in which the chemical-physical strength of the negative electrode current collector increases as the average crystal particle diameter decreases, it is desirable that the microstructure is crystalline, so the lower limit of the average crystal particle diameter is preferably 0.01 μm.

By setting the average crystal particle diameter to 50 μm or less, the strength of the aluminum foil or the aluminum alloy foil can be dramatically improved. By increasing the strength of the negative electrode current collector, physical and chemical resistance is enhanced, and breakage of the negative electrode current collector can be reduced. In particular, it is possible to prevent deterioration due to significant dissolution and corrosion of the negative electrode current collector during a long-term overdischarge cycle in a high-temperature environment (40° C. or higher), and to suppress an increase in electrode resistance. Furthermore, by suppressing an increase in electrode resistance, Joule heat is reduced, and heat generation of the electrode can be suppressed.

In addition, by increasing the size of the negative electrode current collector, even if a high pressure is applied to the negative electrode, the current collector does not break. As a result, the density of the anode can be increased to a high level, and the capacity density can be increased.

Generally, when pressure is applied to the electrode, the smaller the average particle diameter of the negative electrode active material, the greater the load on the negative electrode current collector. By using an aluminum foil with an average particle diameter of 50 μm or less or an aluminum alloy foil with an average particle diameter of 50 μm or less as the negative electrode current collector, the negative electrode current collector can withstand the impact caused by the negative electrode active material with an average particle diameter of 1 μm or less. Since the electrode is subjected to a strong load when pressure is applied, breakage of the negative electrode current collector during pressure application can be avoided.

In addition, by increasing the density of the negative electrode, the thermal conductivity increases and the heat dissipation of the electrode can be improved. Furthermore, the increase in battery temperature can be suppressed by the cumulative effect of suppressing the heat generation of the electrode and improving the heat dissipation of the electrode.

Aluminum foil or aluminum alloy foil with an average particle diameter of less than or equal to 50 μm is complicated by many factors such as material composition, impurities, processing conditions, heat treatment history, and firing heating and cooling conditions. In the manufacturing process, organically combine the above The above-mentioned crystal particle diameter is adjusted for each factor. In addition, the negative electrode current collector can be produced by using PACAL21 made of foil made in Japan.

Specifically, an aluminum foil having an average particle diameter of 50 μm or less can be produced by annealing an aluminum foil having an average particle diameter of 90 μm at 50° C. to 250° C. and then cooling to room temperature. On the other hand, an aluminum alloy foil having an average particle diameter of 50 μm or less can be produced by annealing an aluminum alloy foil having an average particle diameter of 90 μm at 50° C. to 250° C. and then cooling to room temperature.

The average particle diameter of the aluminum foil and the aluminum alloy foil was measured by the method described below. The surface structure of the negative electrode current collector was observed with a metal microscope, and the number n of crystal grains existing in a field of view of 1 mm×1 mm was measured, and the average grain area S (μm ² ) was calculated by the following formula (2).

S=(1×10 ⁶ )/n (2)

Here, the value represented by (1×10 ⁶ ) is the viewing area (μm ² ) of 1 mm×1 mm, and n is the average number of particles.

Using the obtained average particle area S, the average particle diameter d (μm) was calculated according to the following formula (3). Such calculation of the average particle diameter d was performed for five positions (five fields of view), and the average value thereof was taken as the average particle diameter. An error of about 5% is assumed.

d=2(S/π) ^1/2 (3)

It is desirable that the thickness of the negative electrode current collector is 20 μm or less. Ideally, the purity of the aluminum foil is greater than or equal to 99.99%. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, manganese, and silicon is desirable. On the other hand, it is desirable that the amount of transition metals such as iron, copper, nickel, and chromium is equal to or less than 100 ppm.

A carbon material can be used as the conductive agent. For example, acetylene black, carbon black, coke, carbon fiber, graphite, etc. are mentioned.

Examples of the adhesive include polytetrafluoroacetylene fiber (PTFE), polyfluorinated acetylene (PVdF), fluorine-based rubber, and styrene-butadiene rubber.

Ideally, the compounding ratio of the active material of the negative electrode, the conductive agent and the binder is within the range of 80 to 95% by weight of the negative electrode active material, 3 to 18% by weight of the conductive agent, and 2 to 7% by weight of the binder.

For example, a negative electrode is produced by suspending a negative electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a current collector of aluminum foil or aluminum alloy foil, drying, and applying pressure.

The thickness of the negative electrode active material layer is preferably 5 to 100 μm per one side of the negative electrode current collector. In particular, if the thickness is in the range of 5 to 50 μm, the thermal conductivity of the negative electrode during charge and discharge at a large current can be improved, and thus rapid heat generation can be suppressed.

(2) Positive electrode

The positive electrode has: a positive electrode current collector; and a positive electrode layer that is placed on one or both surfaces of the positive electrode current collector and includes a positive electrode active material, a conductive agent, and a binder.

Examples of the positive electrode current collector include aluminum foil or aluminum alloy foil, and like the negative electrode current collector, it is desirable that the average crystal particle diameter is 50 μm or less. More desirably, it is equal to or less than 10 μm. By setting the range of the average particle diameter to 50 μm or less, the strength of the aluminum foil and the aluminum alloy foil can be dramatically increased, the cathode can be densified under high pressure, and the capacity density can be increased. The smaller the average particle diameter, the more the generation of pores and cracks can be reduced, and the chemical strength and physical strength of the positive electrode current collector can be improved. In order to ensure moderate hardness as a fine structure of a crystalline current collector, it is desirable to set the lower limit of the average particle diameter to 0.01 μm.

It is desirable that the thickness of the positive electrode current collector is 20 μm or less.

Examples of the positive electrode active material include oxides, sulfides, polymers, and the like.

For example, oxides include manganese dioxide such as _{MnO2 ,} iron oxide, _copper oxide, nickel oxide, lithium manganese composite oxides such as _LixMnO2O4 or _{LixMnO2 ,} lithium manganese composite oxides such as _{LixNiO2 ,} etc. Nickel composite oxides, lithium-cobalt composite oxides such as _LixCoO2 , _lithium -nickel-cobalt _composite oxides such as LiNi1 _{- yCoyO2} , lithium-manganese _- cobalt composite oxides such as _{LiMnyCo1 -yO2} , such as LiMn _2-y Ni _y O ₄ and other spinel lithium manganese cobalt composite oxides, such as Li _x FePO ₄ , Li _x Fe _1-y Mn _y PO ₄ , Li _x CoPO ₄ and other lithium with olivine structure Phosphorus oxides, iron sulfate such as Fe ₂ (SO ₄ ) ₃ , vanadium oxides such as V ₂ O ₅ , and the like. In addition, x and y are not particularly described, but are preferably in the range of 0-1.

For example, examples of the polymer include conductive polymer materials such as polyaniline and polypyrrole, disulfide-based polymer materials, and the like. In addition, sulfur (S), fluorocarbon, and the like can be used.

As an ideal positive electrode active material, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, spinel lithium manganese nickel composite oxide, lithium manganese cobalt composite oxide substances, lithium iron phosphate, etc. They can get high positive voltage. Among them, if lithium-manganese composite oxide, lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-nickel-cobalt composite oxide, lithium-manganese-cobalt composite oxide is used, it is possible to suppress the interaction between the positive electrode active material and the negative electrode active material in a high temperature environment. The reaction of non-aqueous electrolyte can greatly improve battery life.

In addition, it is desirable to use a lithium nickel manganese cobalt composite represented by Li _a Ni _b Co _c Mn _d O ₂ (wherein the molar ratios a, b, c and d are 0≤a≤1.1, b+c+d=1) oxide. By using the lithium nickel manganese cobalt composite oxide, a high battery voltage can be obtained. More desirable ranges of the molar ratios a, b, c, and d are 0≤a≤1.1, 0.1≤b≤0.5, 0≤c≤0.9, 1≤d≤0.5.

As a conductive agent, acetylene black, carbon black, graphite etc. are mentioned, for example.

Examples of the adhesive include polytetrafluoroacetylene fiber (PTFE), polyfluorinated acetylene (PVdF), fluorine-based rubber, and the like.

Preferably, the compounding ratio of the positive electrode active material, the conductive agent and the binder is within the range of 80 to 95% by weight of the positive electrode active material, 3 to 18% by weight of the conductive agent, and 2 to 7% by weight of the binder.

For example, a positive electrode is fabricated by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to an aluminum foil or aluminum alloy foil current collector, drying, and applying pressure.

The thickness of the positive electrode active material layer is preferably 5 to 100 μm per one side of the positive electrode current collector. In particular, if the thickness is in the range of 5 to 50 μm, the thermal conductivity of the positive electrode during charge and discharge at a large current can be improved, and thus rapid heat generation can be suppressed.

(3) Spacers

Examples of the separator include a synthetic resin nonwoven fabric, a polyethylene porous film, a polypropylene porous film, and the like.

(4) Non-aqueous electrolyte

Examples of the nonaqueous electrolyte include a liquid nonaqueous electrolyte prepared by dissolving the electrolyte in an organic solvent, a gel nonaqueous electrolyte obtained by combining the liquid electrolyte and a polymer material, or a lithium salt electrolyte and a polymer material. Solid non-aqueous electrolyte after material composite. In addition, a room temperature molten salt (ionic melt) containing lithium ions can also be used.

A liquid nonaqueous electrolyte is prepared by dissolving the electrolyte in an organic solvent at a concentration of 0.5 to 2 mol/L.

Examples of electrolytes include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ So ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , Li(CF ₃ SO ₂ ) ₃ C, LiB[(OCO) ₂ ] ₂ and so on. The type of electrolyte used may be one type or two or more types.

Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC) and acetylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate, etc. Lock-shaped carbonates such as esters (MEC), lock-shaped ethers such as dimethoxyacetylene (DME) and acetal acetylene (DEE), cyclic ethers such as tetrahydrofuran (THF), and dioxolane, and γ-butyrolactone ( GBL), acetonitrile cyanomethane (AN), sulfone (SL), etc. alone or mixed solvents. If a non-aqueous electrolyte containing GBL is used, the amount of gas generated during charging can be further reduced. In addition to GBL, it is more preferable if at least one selected from the group consisting of PC and EC is included.

Examples of polymer materials include polyfluorinated acetylene (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), and the like.

In addition, the normal-temperature molten salt (ionic melt) is composed of lithium ions, organic cations, and organic anions, and is liquid at 100° C. or lower, preferably lower than room temperature.

(5) container

As the container, in addition to the container made of laminated film shown in FIG. 2 above, a container made of metal can also be used. Examples of the shape include a flat shape, a rectangular shape, a cylindrical shape, a coin shape, a button shape, a film shape, a laminated shape, and a large battery mounted in an electric vehicle or the like.

As a laminated film, the multilayer film which consists of a metal layer and the resin layer which covers a metal layer is mentioned, for example. For weight reduction, it is desirable that the metal layer is aluminum foil or aluminum alloy foil. The resin layer is used to reinforce the metal layer, and may be formed of polymers such as polypropylene (PP), polyethylene (PE), polyamide, and polyethylene terephthalate (PET).

For example, the laminated film can be bonded by hot-melt bonding to obtain a laminated film container.

The desirable range of the thickness of the laminated film is 0.5 mm or less. In addition, it is desirable that the lower limit of the thickness of the laminated film is 0.01 mm.

Preferably, the metal container is formed of aluminum or an aluminum alloy. It is desirable that each average particle diameter of aluminum or aluminum alloy is 50 μm or less. By setting the average particle diameter to 50 μm or less, the strength of a metal container made of aluminum or an aluminum alloy can be increased, the thickness of the container can be reduced, and sufficient mechanical strength can be secured. Thereby, the heat dissipation of the container can be improved, so that the increase in battery temperature can be suppressed. In addition, by increasing the energy density, it is possible to reduce the weight and size of the battery. In addition, it is more desirably equal to or less than 10 μm. In order to obtain superior electrical conductivity in which the chemical-physical strength of the container increases as the average particle diameter decreases, it is desirable that the microstructure is crystalline, and therefore the lower limit of the average particle diameter is desirably 0.01 μm.

These characteristics are suitable for batteries requiring high-temperature conditions, high energy density, etc., such as storage batteries for vehicles.

The ideal range of the plate thickness of the metal container is 50 mm or less. In addition, it is desirable that the lower limit of the plate thickness of the metal container is 0.05 mm.

Ideally, the above-mentioned aluminum foil has a purity of 99.99% or higher. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, manganese, and silicon is desirable. On the other hand, it is desirable that the amount of transition metals such as iron, copper, nickel, and chromium is equal to or less than 100 ppm.

Metal containers can be sealed by laser. Therefore, compared with a container made of a laminated film, the volume of the sealing portion can be reduced, and the energy density can be improved.

(Example 2)

The storage battery system of the first embodiment is not limited to the case of charging by regenerative electric power, but may also be suitable for rapid charging in a high-temperature environment of 45° C. or higher. Examples of such applications include power supplies for digital cameras, power supplies for light vehicles such as bicycles, backup power supplies for personal computers and factories (UPS uninterruptible power supply units), vacuum cleaners, and the like.

The storage battery system of Embodiment 2 may have the same configuration as the storage battery system of Embodiment 1 described above, except that regenerative power is not used for charging. Ideally, the charging rate is greater than or equal to 2C and less than or equal to 120C. Here, 1C refers to the current value required to discharge the unit cell for one hour, and the value of the metric capacity of the unit cell can be replaced with the current value of 1C for convenience.

In the storage battery systems of Embodiment 1 and Embodiment 2, a battery pack in which a battery pack 3 and a battery control unit (BMU) 4 are housed in one case can be used. In the storage battery system of Embodiment 2, since input by regenerative electric power is not required, the battery pack itself can be used as the storage battery system. A structural example of the battery pack will be described with reference to FIGS. 5 and 6 . 5 is an exploded perspective view of a battery pack used in the storage battery systems of Embodiments 1 and 2, and FIG. 6 is a block diagram showing an electrical circuit of the battery pack in FIG. 5 .

The unit cell 21 of the battery pack shown in FIG. 5 is composed of the flat nonaqueous electrolyte storage battery shown in FIG. 2 . A plurality of unit cells 21 are stacked in the thickness direction so that the protruding directions of the positive electrode terminal 15 and the negative electrode terminal 16 are unified into one. As shown in FIG. 6 , unit cells 21 are connected in series to form battery pack 3 . The battery pack 3 is integrated with an adhesive tape 23 as shown in FIG. 5 .

Ideally, the rated capacity of the unit cell 21 is equal to or greater than 2Ah and equal to or less than 100Ah. A more ideal range of rated capacity is greater than or equal to 3Ah and less than or equal to 40Ah. Furthermore, for hybrid vehicles, it is desirable to have a rated capacity of 3Ah or more and 15Ah or less, and for electric vehicles and UPSs, it is desirable to have a rated capacity of 15Ah or more and 40Ah or less. Here, the rated capacity refers to the capacity when discharged at a rate of 0.2C.

The number of unit cells 21 is ideally greater than or equal to 5 and less than or equal to 500, and a more ideal range of the number is greater than or equal to 5 and less than or equal to 200. Furthermore, for a hybrid vehicle or an electric vehicle, it is preferably 5 or more and 200 or more, and for a UPS, it is preferably 5 or more and 1,000 or more. In addition, for vehicle use, it is desirable to connect the unit cells 21 in series in order to obtain a high voltage.

The printed wiring board 24 is disposed on the side faces protruding from the positive terminal 15 and the negative terminal 16 . As shown in FIG. 5 , a thermistor measuring part 25 a , a protection circuit 26 , and terminals 27 for energizing external devices are mounted on a printed circuit board 24 .

The thermistor measuring means 25 b may be arranged for all of the plurality of unit cells 21 , or may be arranged for any one of the plurality of unit cells 21 . In the case where the thermistor measuring means 25 b is arranged in some of the unit cells 21 , it is necessary to provide the unit cells 21 located in the middle of the battery pack 3 . The maximum detected temperature is the temperature of the battery pack 3 when the thermistor measuring means 25 b is arranged for all of the unit cells 21 or only for a part of them. In addition, it is desirable that the installation position of the measurement part 25 b of the thermistor is the center of the planar part of the unit cell 21 . As a detection signal, the measurement result of the thermistor is sent to the protection circuit 26 .

As shown in FIGS. 5 and 6 , the positive electrode side wiring 28 of the battery pack 3 is electrically connected to the positive electrode side connector 29 of the protection circuit 26 of the printed circuit board 24 . The negative-side wiring 30 of the battery pack 3 is electrically connected to the negative-side connector 31 of the protection circuit 26 of the printed wiring board 24 .

The protection circuit 26 includes a charge and discharge control circuit, a charge cutoff circuit, a discharge cutoff circuit, a voltmeter, and an ammeter. The unit cells 21 are each connected to wirings 32 for detecting voltage and current, and transmit detection signals to the protection circuit 26 through these wirings 32 . A charger and an external load are connected to a terminal 27 for energizing external equipment.

The protection circuit 26 not only functions as a battery control unit, but also plays the following role: under specified conditions, cut off the positive side wiring 31a and the negative side wiring 31b between the protection circuit 26 and the power supply terminal 27 of the external device to ensure safety. The predetermined condition is, for example, when the detected temperature of the thermistor becomes equal to or higher than a predetermined temperature, when overcharge, overdischarge, or overcurrent of the unit cell 21 is detected. This detection method is performed for each unit cell 21 or for the entire unit cell 21 . When detecting each unit cell 21 , the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 21 .

In the battery pack 3 , protective films 33 made of rubber or resin are arranged on three side surfaces other than the sides where the positive terminal 15 and the negative terminal 16 protrude. A block-shaped protective block 34 made of rubber or resin is disposed between the protruding side surfaces of the positive terminal 15 and the negative terminal 16 and the printed circuit board 24 .

In the battery pack 3 , each protective film 33 , protective block 34 , and printed wiring board 24 are housed in a housing container 35 at the same time. That is, the protective film 33 is arranged on both inner surfaces in the longitudinal direction and the inner surface in the lateral direction of the housing container 35 , and the printed circuit board 24 is arranged on the inner surface on the opposite side in the lateral direction. The battery pack 3 is located in a space surrounded by the protective film 33 and the printed wiring board 24 . A cover 36 is mounted on the housing container 35 .

In addition, for fixing the battery pack 3 , a heat-shrinkable tape may be used instead of the adhesive tape 23 . In this case, the protective film is arranged on both sides of the battery pack, and the heat shrinkable tape is wrapped around the heat shrinkable tape, and then the heat shrinkable tape is thermally shrunk to complete the battery pack.

In addition, the unit cells 21 shown in FIGS. 5 and 6 are connected in series, but they may be connected in parallel in order to increase the battery capacity. Of course, the assembled battery modules may also be connected in series or in parallel.

In addition, the flat non-aqueous electrolyte storage battery used in the battery pack is not limited to the structure shown in FIG. 2 above, and may have the structures shown in FIGS. 7 and 8, for example. 7 is a partial sectional perspective view schematically showing another example of a flat non-aqueous electrolyte secondary battery used in the battery pack of FIG. 5 , and FIG. 8 is an enlarged sectional view of part A of FIG. 7 .

As shown in FIG. 7 , a laminated electrode group 18 is accommodated in a container 17 made of a laminated film. The stacked electrode group 18 has a structure in which positive electrodes 12 and negative electrodes 18 are alternately stacked with separators 14 interposed therebetween, as shown in FIG. 8 . There are a plurality of positive electrodes 12 , and each includes a positive electrode current collector 12 a and a positive electrode active material-containing layer 12 b placed on both surfaces of the positive electrode current collector 12 a. There are a plurality of negative electrodes 13 , and each includes a negative electrode current collector 13 a and a positive electrode active material containing layer 13 b placed on both surfaces of the positive electrode current collector 13 a. One side of the negative electrode current collector 13 a of each negative electrode 13 protrudes from the positive electrode 12 . A negative electrode current collector 13 a protruding from the positive electrode 12 is electrically connected to a strip-shaped negative electrode terminal 16 . The front end of the strip-shaped negative electrode terminal 16 protrudes from the container 17 to the outside. In addition, not shown here, the side of the positive electrode current collector 12 of the positive electrode 12 that is located on the opposite side to the protruding side of the negative electrode current collector 13 a protrudes from the negative electrode 13 . A positive electrode current collector 12 a protruding from the negative electrode 13 is electrically connected to a strip-shaped positive electrode terminal 15 . The front end of the strip-shaped positive terminal 15 is located on the opposite side to the negative terminal 16 and protrudes from the side of the container 17 to the outside.

[Example]

Hereinafter, embodiments of the present invention will be described in detail with reference to the above-mentioned drawings. In addition, the present invention is not limited to the embodiments disclosed below unless the gist of the present invention is exceeded.

(Example 1)

The method for producing the negative electrode will be described. Lithium titanate (Li ₄ Ti ₅ O ₁₂ ) with an average particle diameter of 0.3 μm as an active material, carbon powder with an average particle diameter of 0.4 μm as a conductive agent, and polyfluorinated acetylene (PVdF) as a binder It was blended in a weight ratio of 90:7:3, dispersed in n-methylpyrrolidone (NMP) solvent, prepared a paste, and applied to an aluminum alloy foil with a thickness of 12 μm and an average particle diameter of 50 μm (purity is 99.4%), dried and subjected to a pressurization process to produce a negative electrode with an electrode density of 2.4 g/cm ³ . In addition, an aluminum alloy foil (purity: 99.4%) with a thickness of 12 μm and an average particle diameter of 90 μm was annealed at 200° C., and then cooled to room temperature to produce a negative electrode current collector.

A method for producing a positive electrode will be described. Lithium cobalt oxide (LiCoO ₂ ) with an average particle diameter of 3 μm as an active material, graphite powder as a conductive material, and polyfluorinated acetylene (PVdF) as a binder were carried out so that the weight ratio was 87:8:5. Mix and disperse in n-methylpyrrolidone (NMP) solvent, prepare paste, apply to aluminum foil (purity: 99.99%) with an average particle diameter of 15 μm, dry and pressurize, and produce A positive electrode with an electrode density of 3.5g/cm ³ . In addition, an aluminum foil (purity: 99.99%) having a thickness of 15 μm and an average particle diameter of 90 μm was annealed at 140° C., and then cooled to room temperature to produce a positive electrode current collector.

A laminated film containing aluminum with a thickness of 0.1 mm was used for the container. The aluminum layer of the aluminum-containing laminated film had a thickness of about 0.03 mm and an average particle diameter of 100 µm. Polypropylene was used as the resin for reinforcing the aluminum layer. The laminated film is sealed by heat fusion bonding to process the container.

Next, the strip-shaped positive terminal is electrically connected to the positive electrode, and the strip-shaped negative terminal is electrically connected to the negative electrode. A separator made of a polyethylene porous film with a thickness of 12 μm was tightly covered on the positive electrode. The negative electrode was superimposed on the positive electrode covered with the separator so that it faced. Wind them in a helical shape to make an electrode group. This electrode group is pressurized and formed into a flat shape. Insert the flat electrode group into the container.

A liquid non-aqueous electrolyte was prepared by mixing LiBF ₄ as a lithium salt at 1.5 mol/L in an organic solvent in which EC and GBL were mixed at a volume ratio (EC:GBL) of 1:2. The obtained non-aqueous electrolyte was poured into the container, and a thin non-aqueous electrolyte storage battery having the structure shown in FIG. 2 above, with a thickness of 6.5 mm, a width of 70 mm, and a height of 100 mm was fabricated. The battery weighs 90g and has a metric capacity of 3000mAh.

Three thin lithium-ion batteries are connected in series to the positive plate to form a module. Twenty-eight of these modules are connected in series to create a battery pack for a regenerative power storage system. Using this battery pack, battery control unit (BMU), and booster unit, the power storage system for regeneration shown in FIG. 1 above was manufactured.

The power storage system for regeneration is placed in an environment of 55°C, and the surface temperature of the battery is monitored with a temperature sensor, and the battery is charged with the regenerative current (input) from the DC motor at the same time. Since the battery temperature is 60°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the state of charge (SOC (State Of Charge), the state of being fully charged to the rated capacity as 100%) becomes 85%. Charging is performed up to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 is 2.65 V (closed circuit), which corresponds to 0.946×V0 (V). In addition, when fully charged at 25° C., the maximum end-of-charge voltage V0 among the end-of-charge voltages of the unit cells constituting one module is 2.8 (V). Under this temperature environment, carry out the cycle test of input and output.

(Example 2)

The power storage system for regeneration was placed in an environment of 75°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. Since the battery temperature is 80°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 65%. Charging is performed up to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 is 2.45 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(Example 3)

The power storage system for regeneration was placed in an environment of 40°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. Since the battery temperature is 45°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 90%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 was 2.68 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(Example 4)

The power storage system for regeneration is placed in an environment of 65°C, and the surface temperature of the battery is monitored, while the battery is charged with the regenerative current (input) from the DC motor. Since the battery temperature is 70°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 70%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 is 2.50 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(Example 5)

The power storage system for regeneration is placed in an environment of 50°C, and the surface temperature of the battery is monitored, while the battery is charged with the regenerative current (input) from the DC motor. Since the battery temperature is 55°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 88%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 was 2.66 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(Example 6)

The power storage system for regeneration was placed in an environment of 45°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. Since the battery temperature is 65°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 85%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 is 2.38 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(comparative example 1)

The power storage system for regeneration was placed in an environment of 55°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. When the battery temperature is 60°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 105%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage was 2.80 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(comparative example 2)

The power storage system for regeneration was placed in an environment of 75°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. When the battery temperature is 80°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 110%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage was 2.80 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(comparative example 3)

The power storage system for regeneration was placed in an environment of 40°C, and the surface temperature of the battery was monitored, while the battery was charged with the regenerative current (input) from the DC motor. When the battery temperature is 45°C, the charging capacity is automatically calculated by the BMU so that the maximum value of the SOC becomes 102%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage was 2.80 V (closed circuit). In addition, except that the cycle test of input and output was performed in this temperature environment, it was the same power storage system for regeneration as Example 1.

(comparative example 4)

It is the same power storage system for regeneration as in Example 1, except that the carbon fiber of the metho face pitch is used in the negative electrode active material.

(comparative example 5)

It was the same power storage system for regeneration as in Comparative Example 1, except that the interplanar spacing type carbon fiber was used as the negative electrode active material.

The following input/output cycle tests were implemented with respect to the obtained power storage systems for regeneration of Examples 1 to 6 and Comparative Examples 1 to 5. After outputting to SOC 20% (constant current 5C rate), the regenerative power from the DC motor is input (maximum 10C rate) to charge up to each maximum charge end voltage V1 to reach each predetermined SOC value. The input and output were cycled, and the output density (10 seconds) and the expansion rate of the unit cell (based on the thickness of the unit cell before the cycle test) were measured after 1000 cycles in the charged state of SOC50%. Its values are summarized in Table 1. In addition, in Table 1, the relationship between the maximum end-of-charge voltage V1 and the maximum end-of-charge voltage V0 at the time of full charge at 25° C. is described together.

Table 1

According to the results in Table 1, compared with Comparative Examples 1 to 3, the regenerative power storage systems of Examples 1 to 6 maintain extremely high output density at a battery temperature of 45°C or higher, while suppressing the expansion of the unit cell. . In particular, in the regenerative power storage systems of Examples 1, 3, and 5 satisfying 0.9×V0≦V1≦0.96×V0, both the output density after 1000 cycles and the rate of increase in unit cell thickness were excellent.

In the regenerative power storage systems of Comparative Examples 4 and 5, a carbon element material was used as the negative electrode active material. Therefore, not only the maximum end-of-charge voltage V1 but also the amount of gas generated was large, the rate of increase in unit cell thickness after 1000 cycles was large, and the output density was low.

(Example 7)

The method for producing the negative electrode will be described. Spinel-type lithium titanate (Li ₄ Ti ₅ O ₁₂ ) with an average particle diameter of 0.9 μm as an active material, carbon powder with an average particle diameter of 0.4 μm as a conductive agent, and polyfluorinated acetylene as a binder Fork (PVdF) was blended at a weight ratio of 90:7:3, dispersed in n-methylpyrrolidone (NMP) solvent, prepared a paste, and applied to aluminum with a thickness of 12 μm and an average particle diameter of 50 μm. Alloy foil (99.4% pure, containing 5% Si and Fe) was dried and subjected to a pressing process to produce a negative electrode with an electrode density of 2.4 g/cm ³ . In addition, negative electrode active material layers were formed on both surfaces of the negative electrode current collector, and the total thickness of the negative electrode active material layers was 60 μm. In addition, the thickness of the negative electrode active material layer on one side of the negative electrode current collector was 30 μm.

A method for producing a positive electrode will be described. As the positive electrode active material, a lithium nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) with an average particle diameter of 1 μm was prepared, and 8% by weight of graphite powder was mixed with respect to the entire positive electrode as a conductive material. . As a binder, 5% by weight of PVdF was blended with respect to the entire positive electrode, and dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a paste. The paste is applied to both sides of an aluminum alloy foil (purity: 99.4%, containing 0.5% Si and Fe) with a thickness of 15 μm and an average particle diameter of 12 μm, dried and pressed to produce an electrode density of 3.5 g/cm ³ positive pole. In addition, positive electrode active material layers were formed on both surfaces of the positive electrode current collector, and the total thickness of the positive electrode active material layers was 60 μm. In addition, the thickness of the positive electrode active material layer on one side of the positive electrode current collector was 30 μm.

The same aluminum-containing laminated film as in Example 1 was used for the container.

Next, the strip-shaped positive terminal is electrically connected to the positive electrode, and the strip-shaped negative terminal is electrically connected to the negative electrode. A separator made of a polyethylene porous film with a thickness of 12 μm was tightly covered on the positive electrode. The negative electrode was superimposed on the positive electrode covered with the separator so that it faced. Wind them in a helical shape to make an electrode group. This electrode group is pressurized and formed into a flat shape. Insert the flat electrode group into the container.

A liquid non-aqueous electrolyte was prepared by dissolving 1.5 mol/L of lithium salt LiBF ₄ in an organic solvent in which EC and GBL were mixed at a volume ratio (EC:GBL) of 1:2. The obtained non-aqueous electrolyte was poured into the container to produce a flat non-aqueous electrolyte storage battery having the structure shown in FIG. 2 above and having a rated capacity of 6 Ah, a thickness of 4 mm, a width of 100 mm, and a height of 170 mm.

After connecting ten of the obtained storage batteries in series, they were integrated with an adhesive tape to obtain a battery pack. Using this battery pack, a battery pack having the structure shown in FIGS. 5 and 6 was produced to obtain a storage battery system. In addition, the temperature measurement of the thermistor was carried out for the storage battery constituting the outermost layers on both sides of the battery pack and the storage battery constituting the intermediate layer.

The power storage system is placed in an environment of 45°C, and the temperature of the battery pack is monitored with a thermistor, and at the same time, it is rapidly charged at a rate of 20°C. Since the battery temperature is 60° C., the protection circuit 26 automatically calculates the charging capacity so that the maximum value of the SOC becomes 80%. Charge to the target charging capacity while measuring the voltage. When comparing the end-of-charge voltages in the closed circuits of the unit cells constituting one module, the maximum end-of-charge voltage V1 is 2.55 V (closed circuit), which corresponds to 0.85×V0 (V). In addition, the maximum end-of-charge voltage V0 at the time of full charge at 25° C. was 3.0 (V). Under this temperature environment, carry out the cycle test of input and output. The conditions of the cycle test are described below.

After outputting (constant current 5C rate) to SOC 20%, input is performed at 20C rate, and charging is performed up to a predetermined SOC value and maximum charge end voltage V1. The input and output were cycled, and the output density (10 seconds) and the expansion rate of the unit cell in the charged state of SOC 50% after 1000 cycles were measured. In addition, the expansion ratio of the unit cell is based on the thickness of the unit cell before the cycle test.

As a result, the expansion rate of the unit cell after 1000 cycles was 1.0%, and the output density after 1000 cycles was 1500 W/kg (10 seconds).

In addition, the present invention is not limited to the above-described embodiments, and the constituent elements can be modified and embodied within a range not departing from the gist at the stage of implementation. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-mentioned embodiments. For example, some structural elements may be deleted from all the structural elements shown in the embodiments. Furthermore, constituent elements in different embodiments may be appropriately combined. In addition, the input/output rate is not limited to the above rate, and may be set to any value within the range of 2C to 120C. In addition, input and output may be performed continuously, or input and output may be performed in pulses. The pulse time can be in the range of 0.1 second to 30 seconds.

Claims (18)

1. accumulating system is characterized in that comprising:

The battery pack that possesses the unit cell that is made of non-aqueous electrolyte battery, this non-aqueous electrolyte battery possess the negative electrode layer that comprises lithium-titanium composite oxide, the negative pole that comprises the collector body of the above-mentioned negative electrode layer of mounting, positive pole and nonaqueous electrolyte;

Be used to measure the temperature sensor of the temperature of above-mentioned battery pack;

Be used to measure the potentiometer of the voltage of above-mentioned unit cell;

In the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 90 ℃, with the maximum charge final voltage V of above-mentioned unit cell ₁Be controlled at the interior battery charge controller of scope of following formula (1),

0.85×V ₀≤V ₁≤0.96×V ₀(1)

Wherein, V ₀Be illustrated in the maximum charge final voltage of 25 ℃ of above-mentioned unit cells when above-mentioned battery pack is full of electricity, wherein above-mentioned V ₀, V ₁Unit be V.

2. accumulating system according to claim 1 is characterized in that:

The collector body of above-mentioned negative pole is formed by aluminium foil or alloy foil.

3. accumulating system according to claim 1 is characterized in that:

Above-mentioned non-aqueous electrolyte battery has the input and output speed of 2C～120C separately.

4. accumulating system according to claim 1 is characterized in that:

The average particulate diameter of the powder particle of above-mentioned lithium-titanium composite oxide is smaller or equal to 1 μ m.

5. accumulating system according to claim 1 is characterized in that:

Above-mentioned battery charge controller in the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 60 ℃, with the maximum charge final voltage V of above-mentioned unit cell ₁Be controlled to be in the scope of above-mentioned formula (1).

6. accumulating system according to claim 1 is characterized in that:

The powder particle of above-mentioned lithium-titanium composite oxide comprises spinel type lithium ti powder particle.

7. accumulating system according to claim 1 is characterized in that:

Above-mentioned positive pole comprises uses Li _aNi _bCo _cMn _dO ₂The lithium nickel cobalt manganese composite oxides of expression, the molal quantity of wherein representing this element is 0≤a≤1.1, b+c+d=1 with respect to mol ratio a, b, c and the d of the ratio of the total mole number of compound.

8. accumulating system according to claim 1 is characterized in that:

Above-mentioned nonaqueous electrolyte comprises at least a solvent of selecting in the group that is made of gamma-butyrolacton, trimethylene carbonic ester, vinyl carbonate.

9. accumulating system according to claim 1 is characterized in that:

In the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 90 ℃, the maximum charge final voltage V of above-mentioned non-aqueous electrolyte battery ₁In the scope for following formula (2),

0.9×V ₀≤V ₁≤0.96×V ₀(2)

Wherein, V ₀Be illustrated in the maximum charge final voltage of 25 ℃ of above-mentioned unit cells when above-mentioned battery pack is full of electricity.

10. regeneration storage battery system is characterized in that comprising:

With the non-aqueous electrolyte battery is the battery pack of unit cell, and this non-aqueous electrolyte battery possesses the negative electrode layer that comprises lithium-titanium composite oxide, the negative pole that comprises the collector body of the above-mentioned negative electrode layer of mounting;

Be used to send the generator of the regenerated electric power that above-mentioned battery pack is charged;

In the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 90 ℃, with the maximum charge final voltage V of above-mentioned unit cell ₁Be controlled at the interior battery charge controller of scope of following formula (1),

0.85×V ₀≤V ₁≤0.96×V ₀(1)

Wherein, V ₀Be illustrated in the maximum charge final voltage of 25 ℃ of above-mentioned unit cells when above-mentioned battery pack is full of electricity, wherein above-mentioned V ₀, V ₁Unit be V.

11. regeneration storage battery system according to claim 10 is characterized in that:

The collector body of above-mentioned negative pole is formed by aluminium foil or alloy foil.

12. regeneration storage battery system according to claim 10 is characterized in that:

Above-mentioned non-aqueous electrolyte battery has the input and output speed of 2C～120C separately.

13. regeneration storage battery system according to claim 10 is characterized in that:

The average particulate diameter of the powder particle of above-mentioned lithium-titanium composite oxide is smaller or equal to 1 μ m.

14. regeneration storage battery system according to claim 10 is characterized in that:

Above-mentioned battery charge controller in the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 60 ℃, with the maximum charge final voltage V of above-mentioned unit cell ₁Be controlled to be in the scope of above-mentioned formula (1).

15. regeneration storage battery system according to claim 10 is characterized in that:

The powder particle of above-mentioned lithium-titanium composite oxide comprises spinel type lithium ti powder particle.

16. regeneration storage battery system according to claim 10 is characterized in that:

Above-mentioned positive pole comprises uses Li _aNi _bCo _cMn _dO ₂The lithium nickel cobalt manganese composite oxides of expression, the molal quantity of wherein representing this element is 0≤a≤1.1, b+c+d=1 with respect to mol ratio a, b, c and the d of the ratio of the total mole number of compound.

17. regeneration storage battery system according to claim 10 is characterized in that:

In the temperature of above-mentioned battery pack more than or equal to 45 ℃ during smaller or equal to 90 ℃, the maximum charge final voltage V of above-mentioned non-aqueous electrolyte battery ₁In the scope for following formula (2),

0.9×V ₀≤V ₁≤0.96×V ₀(2)

Wherein, V ₀Be illustrated in the maximum charge final voltage of 25 ℃ of above-mentioned unit cells when above-mentioned battery pack is full of electricity.

18. an automobile is characterized in that: the regeneration storage battery system that possesses claim 10 record.

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