KR20250005916A - Manufacturing method of the CFx composite for lithium batteries - Google Patents

Abstract

The present invention relates to a method for manufacturing a fluorocarbon composite material for a lithium battery, and more specifically, to a method for manufacturing a fluorocarbon composite material comprising a step of adding fluorocarbon to an aqueous graphene oxide solution, wherein the fluorocarbon composite material includes a spherical three-dimensional structure. The fluorocarbon composite material for a lithium battery manufactured according to the present invention can control cohesive force between particles and provide high output characteristics.

Description

{Manufacturing method of the CFx composite for lithium batteries}

The present invention relates to a method for producing a fluorocarbon composite material for a lithium battery, and relates to a method for producing a fluorocarbon composite material including a step of adding fluorocarbon to an aqueous graphene oxide solution, wherein the fluorocarbon composite material includes a spherical three-dimensional structure.

The fluorocarbon composite material for lithium batteries manufactured according to the present invention can control cohesion between particles and provide high output characteristics.

Recently, portable devices are being developed with the trend toward higher performance, multi-functionality, and miniaturization, and in line with this development trend, batteries included in portable devices are also becoming smaller, higher capacity, and higher density.

Meanwhile, these portable devices are mainly equipped with batteries that use lithium or a lithium-based mixture as electrodes, but even if they are the same lithium-based batteries, batteries with different usage forms and different compounds are used depending on the purpose and use of the device.

Lithium (Li) batteries are evaluated as suitable as power sources for portable electronic devices due to their superior capacity and reliability compared to other primary batteries, secondary batteries, and electric double layer capacitors.

In particular, lithium primary batteries have the advantages of high energy density, light weight, high output while maintaining stable discharge characteristics, and stability over a wide range of temperatures, and are therefore widely used in small home appliances and precision equipment.

For example, disposable batteries (primary batteries) such as manganese dioxide lithium batteries (Li/ _MnO2 ), lithium fluoride graphite batteries (LiCFn), and lithium sulfur dioxide batteries (Li/ _SO2 ) are used in military equipment and general households, while recyclable, reusable batteries (secondary batteries) such as lithium-ion batteries (Li-Ion Batteries) and lithium-ion polymer batteries (Li-Ion Polymer Batteries) are used in mobile phone devices that require multiple charging.

Meanwhile, lithium primary batteries use metallic lithium as an anode active material, and are classified into several types depending on the type of cathode active material used, electrolyte, electrode, and battery type, and each type has different characteristics such as operating voltage, usage limit current, energy density, operating temperature, storage life, and safety.

Specifically, at low-rate discharge, more than 90% of the capacity can be used and the capacity deviation is small, but at medium and high-rate discharge, the resistance due to the cathode increases, resulting in a significant decrease in capacity depending on the current size.

Accordingly, various studies are being conducted to manufacture cathodes with improved battery capacity, and one method of applying carbon fluoride (CFx) to lithium primary batteries is being studied.

Meanwhile, in the case of CFx materials for lithium primary batteries, when the material is nano/micronized to increase reactivity, it tends to enlarge again due to cohesion caused by the van der Waals force between the materials. This indiscriminate cohesion not only hinders the uniformity of the particles, but also causes limitations in performance enhancement. This leads to significant efficiency loss in the capacity and energy density of the entire system. Therefore, the development of technology that reduces cohesion between particles or can control cohesion between particles is required.

The CFx material, which is enlarged by the van der Waals force, not only grows to an irregular size inside the battery, but also has a problem in that the capacity of the battery system decreases due to the uneven distribution of the particles, and the energy output efficiency decreases due to the low electrical conductivity of the CFx material. As a result, not only the performance of the battery system, but also the device in which the battery system is worn becomes impossible to use smoothly.

In addition, in accordance with the development direction of portable devices, batteries included in portable devices must also be miniaturized, have high capacity, high output, and high density. However, due to the low electrical conductivity of CFx materials and the agglomeration and enlargement that occur during the nano/micro process of CFx, batteries using CFx materials have problems in implementing high-rate discharge characteristics.

Prior literature KR10-1882975 discloses a method for increasing the capacity of a lithium primary battery cathode by applying fluorocarbon, but does not disclose the problem of the material becoming larger again due to cohesion resulting from nano/micro CFx.

Accordingly, the inventors of the present invention developed a fluorocarbon capable of preventing agglomeration on the positive electrode of a lithium primary battery by complexing the fluorocarbon with graphene.

Korean Patent Registration No. 10-1882975 (Announcement Date 2018.07.27.)

The present invention has been created to solve the problems of the prior art as described above, and more specifically, it aims at providing a method for manufacturing a fluorocarbon composite material for a lithium battery having high output characteristics, which has a three-dimensional structure, thereby improving the electrical conductivity of the composite by complexing non-fluorinated carbon, and preventing re-agglomeration or enlargement of fluorocarbon particles through a coating of graphene, and enabling the fluorocarbon particles to be uniformly dispersed.

According to a preferred embodiment of the present invention, a method for producing a fluorocarbon composite material for a lithium battery comprises the steps of: 1) preparing an aqueous graphene oxide solution at a concentration of 1 mg/ml; 2) adding fluorocarbon to the aqueous graphene oxide solution; 3) spray-drying the resultant of step 2) at 180 to 220°C; 4) heat-treating the resultant of step 3) at 270 to 330°C for 90 to 150 minutes; and 5) milling the resultant of step 4) to produce a powder sample. The fluorocarbon composite material is characterized in that it includes a spherical three-dimensional structure.

In addition, the diameter of the spherical three-dimensional structure is characterized by having a diameter of 1 to 4 μm.

The fluorocarbon composite material of the present invention has a three-dimensional structure, so that non-fluorinated carbon is composited to improve the electrical conductivity of the composite, and the coating of graphene prevents the fluorocarbon particles from re-agglomerating or becoming enlarged, and enables the fluorocarbon particles to be uniformly dispersed.

Meanwhile, the effects obtainable from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

Figure 1 is an image of the composite material of the present invention taken using a scanning electron microscope.
Figure 2 shows a photograph of a fluorocarbon composite material of the present invention analyzed using an energy dispersive spectrometer (EDS) attached to a scanning electron microscope.
Figure 3 shows the results of analyzing the electrochemical characteristics of the composite material of the present invention.
Figure 4 shows an XRD analysis graph of (a) planar fluorocarbon and (b) composite material of the present invention.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments thereof.

One embodiment of the present invention

1) Step of preparing a graphene oxide aqueous solution at a concentration of 1 mg/ml;

2) Step of adding fluorocarbon to the graphene oxide aqueous solution;

3) A step of spray drying the result of step 2 at 180 to 220℃;

4) A step of heat-treating the result of step 3 at 270 to 330°C for 90 to 150 minutes; and

5) A step of milling the result of step 4 and manufacturing it into a powder sample;

A method for manufacturing a fluorocarbon composite material for a lithium battery, the method comprising:

The present invention is described in detail below.

The above step 1) is a step for preparing a graphene oxide aqueous solution at a concentration of 1 mg/ml, and is a step for preparing the graphene oxide to be dispersed in the solution using a circulatory ultrasonic wave, etc. so that it can be mixed with deionized water.

The above step 2) is a step of adding carbon fluorocarbon to the graphene oxide aqueous solution, and it is preferable that the added graphene oxide and carbon fluorocarbon are each added in the same weight. If the added graphene oxide and carbon fluorocarbon are not each added in the same weight, the unreacted material may not have a three-dimensional structure, and thus may re-agglomerate when applied to a lithium primary battery, resulting in a decrease in electrical conductivity.

The above-described added fluorocarbon is represented by the chemical formula of CFx, and x may be from 0.5 to 3. The x may have any range from 0.5 to 3. In a preferred example, the x is from 0.5 to 1.5. In another preferred example, the x is from 1 to 3.

The above step 3) is a step of spray drying the result of step 2) at 180 to 220℃, and through the spray drying process, graphene oxide and carbon fluoride primarily react to form a complex.

The above step 4) is a step of heat-treating the resultant product of step 4) 3) at 270 to 330°C for 90 to 150 minutes, and through step 4), graphene oxide is reduced and secondarily reacts with carbon fluoride.

The composite material manufactured above may be for use in a lithium primary battery, but is not limited thereto.

Another embodiment of the present invention to achieve the above purpose is

It is a fluorocarbon composite material with high output characteristics manufactured by a manufacturing method.

The above-mentioned manufactured fluorocarbon composite material may include a spherical three-dimensional structure. The spherical three-dimensional structure may have an increased surface area compared to planar fluorocarbon, particularly since fluorocarbon is combined in a three-dimensional state, and thus the electrical conductivity and electrochemical properties may be enhanced.

The diameter of the above three-dimensional structure may be 1 to 4 μm. If the diameter is out of the above range, the stability of the three-dimensional structure may be reduced and re-aggregation may occur. Preferably, the diameter of the above three-dimensional structure may be 2 to 3 μm.

Another embodiment of the present invention to achieve the above purpose is

The present invention provides a method for manufacturing a cathode of a lithium primary battery, comprising the steps of: preparing a slurry by mixing the above-described fluorocarbon composite material, a metal oxide, a conductive material, an organic solvent, and a binder; forming an electrode by coating the slurry on a current collector and then performing a first heat treatment; performing a second heat treatment on the electrode at a temperature higher than the first heat treatment; and cold rolling the second heat-treated electrode.

The above slurry is for manufacturing an electrode and contains a fluorocarbon composite material, a metal oxide, a conductive material, an organic solvent, and a binder, and may additionally contain an aqueous dispersant or an organic dispersant such as N-methyl-2-pyrrolidone, if necessary.

The above fluorocarbon composite material may be included in an amount of 8 to 15 parts by weight based on 100 parts by weight of the slurry. If the fluorocarbon composite material is included in an amount of less than 8 parts by weight, there is a concern that the battery capacity may be reduced due to low electrical conductivity, and if it exceeds 15 parts by weight, the volume becomes too large compared to other materials in the slurry, which may result in a problem of reduced electrochemical activity.

In addition, the above-mentioned fluorocarbon composite material and the metal oxide may be included in a weight ratio of 1:2 to 1:5, more preferably 1:2.5 to 1:3. When manufacturing an electrode with a slurry satisfying the above ratio, excellent electrolyte impregnation property is exhibited, and surface cracks are minimized during drying, thereby improving electrode durability.

Specifically, the metal oxide may be MnO ₂ .

The binder comprises polyvinyl alcohol (PVA) and may further comprise one selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), and combinations thereof.

The binder is added to provide flexibility and high mechanical strength to the electrode, and may be included in an amount of 40 to 70 parts by weight per 100 parts by weight of the slurry.

Specifically, polyvinyl alcohol is added to physically attach fluorocarbon, metal oxide, and conductive material during the manufacture of electrode slurry, but there is a problem that the discharge capacity decreases when it is contained in large amounts in the finished electrode.

Accordingly, the present invention aims to provide an electrode having a high discharge capacity by removing polyvinyl alcohol by treating a slurry of the above composition at a specific temperature.

Additionally, the conductive agent may be one selected from carbon black, acetylene black, Ketjen black, furnace black, carbon fibers, carbon nanotubes, fullerenes, and combinations thereof that do not cause chemical changes in fluorinated carbon and metal oxides included in the slurry.

Although not particularly limited, it is preferable to use acetylene black alone or a mixture of acetylene black and ketjen black in a weight ratio of 6:4 to 9.9:0.1.

The above organic solvent may be, but is not limited to, ethanol (EtOH), acetone, isopropyl alcohol, methyl pyrrolidone (NMP), propylene glycol, and the like.

A slurry having such a composition is coated on a collector and then subjected to a primary heat treatment to form an electrode. At this time, the primary heat treatment can be performed at a temperature of 60 to 100° C. for 20 to 40 minutes.

By performing heat treatment under temperature conditions within the above range before secondary heat treatment, the surface of the slurry can be dried, thereby reducing the occurrence of cracks.

Thereafter, the electrode is subjected to a second heat treatment at a temperature higher than the first heat treatment. The second heat treatment can be performed at a temperature of 200 to 300° C., more preferably at a temperature of 220 to 250° C., for 5 to 7 hours.

In general, in order to manufacture a cathode of a primary battery, it is common to coat an electrode slurry on a current collector, heat-treat and dry at a temperature of less than 150°C, and then roll. However, in the case of a slurry containing polyvinyl alcohol as a binder, the specific gravity of polyvinyl alcohol in the dried electrode was too large, resulting in a decrease in discharge capacity. In other words, there was a problem that a voltage drop occurred when an electrode was manufactured with a large amount of PVA contained.

Accordingly, the method for manufacturing a positive electrode of a lithium primary battery according to the present invention can improve the discharge capacity of the completed electrode by burning off polyvinyl alcohol by performing a secondary heat treatment at a temperature of 200°C or higher.

Specifically, if the secondary heat treatment is performed at a temperature below 200°C, it is difficult for the polyvinyl alcohol to evaporate, and if it is performed at a temperature exceeding 300°C, there is a concern that the properties of other active materials in the slurry may change. Therefore, when the secondary heat treatment is performed under conditions satisfying the above range, the discharge capacity and the energy density of the battery are the best.

With respect to 100 parts by weight of the above slurry, 40 to 60 parts by weight of polyvinyl alcohol may be included as a binder, and after the secondary heat treatment, with respect to 100 parts by weight of the above electrode, 10 parts by weight or less of polyvinyl alcohol may be included.

This is because the polyvinyl alcohol is removed from the electrode slurry by combustion through the secondary heat treatment, and a relatively large amount of polyvinyl alcohol is included as a binder in the slurry state to help the fusion of the active material, and is evaporated through the secondary heat treatment during electrode coating, so that the battery capacity and electrode output characteristics can be improved.

In addition, the second heat-treated electrode is cold rolled, and the cold rolling can be performed at a compression ratio of 25 to 40%. This can reduce unnecessary pores and improve the bonding strength between materials.

It is most preferable that the thickness of the above cold rolled electrode be 250 to 300 μm.

Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are only intended to specifically illustrate or explain the present invention, and the present invention should not be limited thereto.

Example 1. Method for producing fluorocarbon composite material for lithium battery

Deionized water and graphene oxide were mixed at a concentration of 1 mg/ml, and then dispersed through sonication for 1 hour while cooling at 5°C using a circulator. The same weight of carbon fluorocarbon as the added graphene oxide was added. The mixture was spray dried at 200°C to produce a composite.

After that, the above graphene oxide-fluorocarbon composite was heat treated at 300°C for 2 hours to produce a graphene oxide-fluorocarbon composite, during which the graphene oxide reacts to reduced graphene oxide (rGO). The resultant was produced as a powder sample using a milling device.

Example 2. Characteristics of fluorocarbon composite materials with high output characteristics

An image of the composite material of the present invention taken by a scanning electron microscope is shown in Fig. 1. It was confirmed that the composite material of the present invention exhibits a spherical three-dimensional structure with a diameter of 2-3 ㎛, in which graphene and fluorocarbon are combined.

The image of the fluorocarbon composite material analyzed by an energy dispersive spectrometer (EDS) attached to a scanning electron microscope is shown in Fig. 2. It can be confirmed that C and F are detected. It can be confirmed that fluorocarbon (CFx) is uniformly complexed within the graphene flake composite.

The results of analyzing the electrochemical characteristics of the composite material of the present invention are shown in Fig. 3. The electrode manufactured with fluorocarbon showed a specific storage capacity per area of 3 mAh/cm2, and the electrode manufactured with the graphene flake composite showed a specific storage capacity per area of 28 mAh/cm2. It was confirmed that the corresponding figures have a performance 24% higher than that of conventional primary battery electrode manufacturing conditions.

Accordingly, it was confirmed that the electrode manufactured with the graphene flake composite had improved electrochemical properties that could prevent excellent electrical conductivity and particle aggregation characteristics compared to the electrode manufactured with fluorocarbon. The maximum expressed battery capacity per unit area (cm ² ) was 28 mAh, which was approximately 7 times higher than that of aluminum foil (Al Foil) with a battery capacity of 4 to 4.4 mAh.

(a) Bare carbon fluorocarbon (b) XRD analysis graphs of the composite material of the present invention are shown in Fig. 4. Fig. 4 (a) is an XRD analysis graph of bare carbon fluorocarbon (CFx), and Fig. 4 (b) is an XRD analysis graph of a graphene flake composite (CFx/r-GO).

In this regard, Fig. 4 (a) shows peaks at 13° and 41°, while Fig. 4 (b) showed peaks at 13°, 24°, 38°, 41°, and 43°. That is, when Figs. 4 (a) and (b) are compared, Fig. 4 (b) shows the same peaks as Fig. 4 (a) at 13° and 41°, while new peaks were observed at 24° (r-GO) and 38° and 43° (formation of Unfluorinated Phase, unfluorinated carbon). This can be judged to be because the crystal and composition of the parent material, fluorocarbon (CF x), do not change during the synthesis of the graphene flake composite, and the electrical conductivity of the composite is improved by complexing the graphene flake (r-GO) with the unfluorinated carbon having a three-dimensional structure.

In summary, it was confirmed that the coating of the graphene flake composite prevented the fluorocarbon particles from re-agglomerating or becoming enlarged, and that the fluorocarbon particles were uniformly dispersed.

Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims (2)

The method for manufacturing a fluorocarbon composite material is as follows:
1) Step of preparing a graphene oxide aqueous solution at a concentration of 1 mg/ml;
2) Step of adding fluorocarbon to the graphene oxide aqueous solution;
3) A step of spray drying the result of step 2 at 180 to 220℃;
4) A step of heat-treating the result of step 3 at 270 to 330°C for 90 to 150 minutes; and
5) A step of milling the result of step 4 and manufacturing it into a powder sample;
Including,
A method for manufacturing a fluorocarbon composite material for a lithium battery, wherein the fluorocarbon composite material comprises a spherical three-dimensional structure.
In the first paragraph,
A method for manufacturing a fluorocarbon composite material for a lithium battery, wherein the diameter of the above spherical three-dimensional structure has a diameter of 1 to 4 μm.