CN106972197A - A kind of anti-overcharge lithium battery electrolytes and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of anti-overcharge lithium battery electrolytes and preparation method thereof, belong to lithium battery material technical field.The present invention is made up of lithium salts, double solvents and additive；It is characterized in that：The lithium salts is at least one of inorganic lithium salt, organic boronic lithium, lithium salts of sulfonimide；The double solvents is at least two solvents in carbonate-based solvent；The additive is at least one of sulfurous esters compound, carbonats compound, sulfonates compounds and the DfBP of 2', 4' dimethyl 2,4；The quality of the additive accounts for 1% the 15% of electrolyte.The present invention prepares anti-overcharge lithium battery electrolytes, and oxidation Decomposition can occur when lithium battery is overcharged prior to electrolyte, and contact of the cut-off electrolyte with electrode surface lifts security performance.

Description

A kind of anti-overcharge lithium battery electrolyte and preparation method thereof

technical field

The invention relates to the technical field of lithium battery materials, in particular to an electrolyte solution for preventing overcharge lithium batteries and a preparation method thereof.

Background technique

Lithium-ion battery is the rechargeable battery with the highest specific energy at present. It replaces metallic lithium as the anode with a lithium-intercalated compound, thereby overcoming the passivation and lithium dendrite problems of the anode in traditional lithium batteries, and the lithium-ion battery has a working voltage High, high energy density, high power density and other advantages have been widely used in digital, mobile communications and other fields, and gradually applied in national defense and military. In recent years, with the rapid development of electric bicycles and electric vehicles, lithium-ion batteries It is considered to be the vehicle power battery with the most potential development at present. However, the electrolyte used in most lithium batteries is a flammable carbonate mixed solvent system. If the lithium battery is charged incorrectly and causes overcharging, the potential of the electrode is high, which is likely to cause a solvent decomposition reaction, which will increase the temperature of the battery and cause The rupture, combustion or explosion of the battery cell causes safety problems and is a bottleneck restricting the development of lithium batteries in the direction of large-scale and high-energy.

In response to this problem, researchers have optimized the composition of the electrolyte and introduced a small amount of functional substances to establish an electrochemical self-protection mechanism to prevent overcharging inside the battery. For example, U.S. Patent US5776627 discloses an anti-overcharge additive biphenyl. When the battery is overcharged, the gas-producing additive biphenyl will polymerize on the surface of the electrode to form an SEI film, which prevents the migration of lithium ions, increases the internal resistance of the battery, and makes it break. Electricity improves the safety performance of the battery, but this kind of additive produces a lot of gas, which is easy to cause the explosion of the battery cell and cause a safety accident. Therefore, it is an urgent technical problem to find a suitable overcharge protection additive so that the SEI film can avoid the safety problems caused by overcharge without affecting the charge and discharge performance of the battery.

Contents of the invention

In order to make up for the deficiencies of the prior art, the invention provides an electrolyte solution for preventing overcharging lithium batteries and a preparation method thereof.

Technical scheme of the present invention is:

An electrolyte solution for an anti-overcharge lithium battery, consisting of a lithium salt, a composite solvent and an additive; the lithium salt is at least one of inorganic lithium salts, lithium organic borates, and sulfonimide lithium salts; the composite solvent It is at least two solvents in carbonate solvents; the additive is at least one of sulfite compounds, carbonate compounds, sulfonate compounds and 2',4'-dimethyl-2, 4-difluorobiphenyl; the mass of the additive accounts for 1%-15% of the electrolyte.

As a preferred version, the concentration of the inorganic lithium salt is 0.5-2mol/L, the concentration of the sulfonimide lithium salt is 0.1-0.5mol/L, and the concentration of the organic lithium borate is 0.1-0.5mol/L L.

As a preferred solution, the inorganic lithium salt is LiPF ₆ or LiBF ₄ ; the lithium organic borate is lithium dioxalate borate, lithium difluorooxalate borate, and the lithium sulfonimide salt is bistrifluoromethanesulfonate Lithium imide, lithium bisfluorosulfonyl imide.

As a preferred solution, the carbonate-based solvent consists of cyclic carbonates and linear carbonates.

Further, the cyclic carbonate is ethylene carbonate and/or propylene carbonate.

As a preferred embodiment, the linear carbonate is one or more of diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

As a preferred solution, the mass ratio of cyclic carbonate to linear carbonate is 1:1-4.

As a preferred version, the sulfite compound is vinyl sulfite, propylene sulfite; the carbonate compound is vinylene carbonate and/or fluoroethylene carbonate; the sulfonate compound is 1,3-propane sultone.

Further, the additive is a mixture of carbonate compounds, sulfonate compounds and 2',4'-dimethyl-2,4-difluorobiphenyl.

The preparation method of the anti-overcharge lithium battery electrolyte comprises the steps of:

1) Take the solvent and mix it evenly, and cool down to below 10°C;

2) Add lithium salt under the condition that the temperature is not higher than 10°C, and stir until the lithium salt dissolves;

3) Add additives and continue to stir until a uniform solution is formed to obtain the overcharge-proof lithium battery electrolyte.

The electrolyte of the overcharged lithium battery meets the following requirements: impurity ≤ 0.1% (GC), moisture ≤ 15ppm, heavy metal ≤ 1ppm, chloride ≤ 1ppm, sulfate ≤ 5ppm, color ≤ 50APHA; other metal impurities Na, K, Fe , K, Mg, etc. ≤ 1ppm.

The beneficial effects of the present invention are:

Compared with prior art, the beneficial effect of the present invention is:

1. When overcharging occurs, other components will react first, and the gas production will be less, which can effectively prevent the occurrence of safety problems such as fire and explosion caused by overcharging of lithium batteries, and increase the safety of the battery;

2. It has little effect on the conductivity of the electrolyte, high charge and discharge efficiency, can meet the charge and discharge requirements of more than 85% for 500 times, and can especially improve the high temperature cycle performance of lithium batteries;

3. Strong applicability, can be used in various electrochemical lithium battery systems such as graphite/lithium cobalt oxide, graphite/lithium manganese oxide and other systems.

The anti-overcharge lithium battery electrolyte of the present invention effectively prevents the occurrence of safety problems such as fire and explosion caused by overcharging of the lithium battery without affecting the capacity and cycle performance of the lithium battery, greatly improves the safety performance of the lithium battery, and broadens the Its scope of application can be used in various electrochemical lithium battery systems.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the electrochemical cyclic voltammogram of the electrolyte solution prepared by using Example 1 (blank) and Example 4.

detailed description

Example 1:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear, and then fully Stir and transfer to a bottle filled with inert gas for storage.

Example 2:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 1% vinylene carbonate and 2% 1,3-propane sultone, then fully stirred, and transferred to a packaging bottle filled with inert gas for storage until use.

Example 3:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 2% 1,3-propane sultone, then fully stirred, and transferred to a packaging bottle filled with inert gas for storage until use.

Example 4:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 2% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, then fully stirred, and transferred to a bottle filled with inert gas for storage until use.

Example 5:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 1% vinylene carbonate and 2% 1,3-propane sultone, then fully stirred, and transferred to a packaging bottle filled with inert gas for storage until use.

Embodiment 6:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow Calculate the total mass of the electrolyte by adding 1% vinylene carbonate and 2% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, then fully stir, and transfer to a bottle filled with inert gas for storage. use.

Embodiment 7:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow Calculate the total mass of the electrolyte by adding 2% 1,3-propane sultone and 2% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, then fully stir, and turn into an inert Gas packaging bottles are stored for later use.

Embodiment 8:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 1% vinylene carbonate, 2% 1,3-propane sultone, and 2% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, and then Stir well and transfer to a bottle filled with inert gas for storage.

Embodiment 9:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 1% vinylene carbonate, 2% 1,3-propane sultone, and 3% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, and then Stir well and transfer to a bottle filled with inert gas for storage.

Example 10:

Add dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in sequence according to the mass ratio of 1:1:1, and when the temperature drops to 10°C, ensure that the temperature is not higher than 10°C Slowly add lithium salt under low pressure to prepare an electrolyte solution with a lithium hexafluorophosphate concentration of 1mol/L, a lithium difluorooxalate borate concentration of 0.2mol/L, and a lithium bisfluorosulfonyl imide concentration of 0.1mol/L, and keep stirring until the solution is clear; then follow The total mass of the electrolyte is calculated by adding 1% vinylene carbonate, 2% 1,3-propane sultone, 5% anti-overcharge 2',4'-dimethyl-2,4-difluorobiphenyl, and then Stir well and transfer to a bottle filled with inert gas for storage.

The electrolytic solutions in the above 10 examples were tested for their electrical conductivity, and the data are shown in Table 1. It can be seen from Table 1 that the preparation of the anti-overcharge lithium battery electrolyte by the present invention has basically no effect on the conductivity of the electrolyte.

In addition, a cyclic voltammetry test was carried out for Example 1 and Example 4. The open circuit voltage was scanned forward to 5.5V at a scan rate of 1mv/s, and then retraced to 3.0V. The data are shown in FIG. 1 . It can be seen from Figure 1 that the anti-overcharge lithium battery electrolyte prepared by the present invention can oxidize and decompose preferentially over the electrolyte when the lithium battery is overcharged, cut off the contact between the electrolyte and the electrode surface, and improve safety performance.

In addition, the electrolyte solutions of the above-mentioned 10 examples were respectively filled into pouch batteries with a design capacity of 2Ah and overcharged to 6.3V at a rate of 1C. After that, acupuncture and short circuit tests were performed. The test results are shown in Table 2. It can be seen from Table 2 that the preparation of the anti-overcharge lithium battery electrolyte in the present invention can greatly improve the safety performance of the lithium battery.

Finally, the electrolyte solutions of the above 10 examples were respectively filled into pouch batteries with a design capacity of 2Ah, and were charged and discharged at 55°C for 500 cycles at a rate of 1C. The test results are shown in Table 3. It can be seen from Table 3 that the anti-overcharge lithium battery electrolyte prepared by the present invention can improve the cycle performance of the lithium battery and increase the service life of the lithium battery.

Table 1

Table 2

table 3

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. The embodiments are applied to other fields, but any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solutions of the present invention without departing from the content of the technical solutions of the present invention.

Claims (10)

1. a kind of anti-overcharge lithium battery electrolytes, are made up of lithium salts, double solvents and additive；It is characterized in that：The lithium salts For at least one of inorganic lithium salt, organic boronic lithium, lithium salts of sulfonimide；The double solvents is in carbonate-based solvent At least two solvents；The additive is in sulfurous esters compound, carbonats compound, sulfonates compounds At least one and 2', 4'- dimethyl -2,4- DfBPs；The quality of the additive accounts for the 1%-15% of electrolyte.

2. anti-overcharge lithium battery electrolytes as claimed in claim 1, it is characterised in that：The concentration of the inorganic lithium salt is 0.5- 2mol/L, the concentration of the lithium salts of sulfonimide is 0.1-0.5mol/L, and the concentration of the organic boronic lithium is 0.1- 0.5mol/L。

3. anti-overcharge lithium battery electrolytes as claimed in claim 1 or 2, it is characterised in that：The inorganic lithium salt is LiPF₆Or LiBF₄；Described organic boronic lithium is dioxalic acid lithium borate, difluorine oxalic acid boracic acid lithium, and described lithium salts of sulfonimide is double Trifluoromethanesulfonimide lithium, double fluorine sulfimide lithiums.

4. anti-overcharge lithium battery electrolytes as claimed in claim 1 or 2, it is characterised in that：The carbonate-based solvent is by ring-type Carbonic ester and linear carbonates composition.

5. anti-overcharge lithium battery electrolytes as claimed in claim 4, it is characterised in that：The cyclic carbonate is ethylene carbonate And/or propene carbonate.

6. anti-overcharge lithium battery electrolytes as claimed in claim 4, it is characterised in that：The linear carbonates are carbonic acid diethyl One or more in ester, dimethyl carbonate, methyl ethyl carbonate.

7. anti-overcharge lithium battery electrolytes as claimed in claim 4, it is characterised in that：The matter of cyclic carbonate and linear carbonates Amount is than being 1:1-4.

8. anti-overcharge lithium battery electrolytes as claimed in claim 1 or 2, it is characterised in that：The sulfurous esters compound is Ethylene sulfite, propylene sulfite；The carbonats compound is vinylene carbonate and/or fluoro ethylene carbonate Ester；The sulfonates compounds are 1,3- propane sulphur lactones.

9. anti-overcharge lithium battery electrolytes as claimed in claim 8, it is characterised in that：The additive is carbonates chemical combination The mixture of thing, sulfonates compounds and 2', 4'- dimethyl -2,4- DfBPs.

10. the preparation method of anti-overcharge lithium battery electrolytes as claimed in claim 1, it is characterised in that including step：

1）Take solvent and be well mixed, be cooled to less than 10 DEG C；

2）Lithium salts is added under conditions of temperature is not higher than 10 DEG C, and is stirred to lithium salts dissolving；

3）Additive is added, continues to stir to uniform solution is formed, obtains the anti-overcharge lithium battery electrolytes.