TWI690113B - Method for manufacturing ternary cathode material - Google Patents

Abstract

The invention provides a method for manufacturing a ternary cathode material, comprising: performing a mixing process and an air pressure process on a nickel-cobalt-manganese composite oxide and a graphene to form a ternary cathode material, wherein the graphene The sheet diameter is between 10 and 100 μm.

Description

Method for manufacturing ternary cathode material

The invention is a method for manufacturing a lithium ion cathode material, and particularly relates to a method for manufacturing a graphene-coated lithium ion ternary cathode material.

Lithium-ion batteries are widely used in portable electronic products such as mobile phones and notebooks because they have the advantages of high energy density, high operating voltage, large operating temperature range, no memory effect, long life, and can undergo countless charge and discharge. Computers, digital cameras, etc. have expanded into the automotive field in recent years.

The positive electrode material of lithium ion battery mainly affects the energy density, safety, cycle times and charge-discharge characteristics of lithium ion battery, and it is the most important material in lithium ion battery. The high-nickel ternary cathode material (LiNixCoyMnzO ₂ , NMC for short) is a layered structure, which is one of the potential applications for high-energy-density electric vehicles. However, the loop performance and safety performance of the material vary with the nickel content. Increase and gradually deteriorate. The total alkali content of the high nickel cathode material is high, that is, there is more residual lithium on the surface; as the nickel content is higher, the total alkali content is also higher. When the material contacts air, the structure, morphology and composition of the powder material change, and the electrochemical performance gradually declines, especially when exposed to humid air. This phenomenon is most obvious.

The surface-coated stable nano-layer is an effective method to improve the performance of high-nickel cathode materials. The electrochemically inert substances used for surface coating mainly include metal oxides, phosphates, fluorides and high-molecular polymers.

It is the most common method to coat the electrochemical inert protective layer on the surface, that is, the body before the inert layer is dissolved in an organic solvent to uniformly coat the surface of the ternary positive electrode material (NMC), and finally the heat treatment is performed to turn the precursor into inert For the protective layer, the heat treatment step at this time not only consumes energy but also sacrifices the discharge capacity of the positive electrode material, and the inert protective layer also increases the internal resistance of the NMC, again reducing the discharge specific capacity of the ternary positive electrode material (NMC).

In view of the shortcomings of the above-mentioned prior art, the main purpose of the present invention is to perform the coating process with ternary positive electrode powder, and no organic solvent is added in the process to prevent the ternary positive electrode powder from being damaged by moisture or acid and alkali, for manufacturing A high-performance ternary cathode material is produced.

Another object of the present invention is to use the ternary positive electrode powder for the coating process to prevent the ternary positive electrode material from being coated with the body before the inert layer to reduce the discharge specific capacity of the ternary positive electrode material due to heat treatment. A ternary cathode material with high discharge specific capacity is provided.

In order to achieve the above object, a method for manufacturing a ternary cathode material according to the present invention includes: performing a mixed process of a nickel-cobalt-manganese composite oxide and a graphene and an air pressurized process to form a ternary cathode Material, wherein the graphene sheet diameter is between 10 and 100 μm.

In the above, the mixing process is a ternary cathode material with 0.5 to 5 wt% of multi-layer graphene, mechanically ground for 30 to 300 minutes, wherein the grinding method is dry ball milling, wet ball milling, planetary mixing or dry grinding. Any one or combination thereof.

In the above, the graphene is graphitized multilayer graphene, and the heat treatment temperature of the graphene is between 1500 and 2300°C.

In the manufacturing method of the above ternary cathode material, the air pressurization process is to lay the ternary cathode material on a stainless steel square vessel and pressurize the gas with air, wherein the pressure of air pressurization is 5~15kg/m ² between.

In the method for manufacturing the ternary cathode material, the mixing process and the air pressurization process are performed simultaneously. In the method for manufacturing the ternary cathode material, the air pressurization process is started only after the mixing process is completed.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the ways, means and effects of this creation to achieve its intended purpose. The other purposes and advantages of this creation will be explained in the subsequent description and drawings.

The first picture is the SEM (scan electron microscope) picture of the NMC/MLG in the first embodiment of the present invention; the second picture is the SEM (scan electron microscope) picture of the 3P-G-MLG/NMC in the present invention; The third diagram is a SEM (scan electron microscope) diagram of the NMC of Comparative Example 1 of the present invention; the fourth diagram is a long-cycle charge-discharge test diagram of half-cells of Examples 1 to 3 and Comparative Example 1 of the present invention.

The following is a description of the embodiments of the present invention by specific specific examples. Those skilled in the art can easily understand the advantages and effects of the present invention from the contents disclosed in this specification.

The manufacturing method of the ternary cathode material of the present invention is to use multi-layer graphene to coat the outer layer of the nickel-cobalt-manganese composite oxide. One of the advantages is the dry grinding and air pressure process to make the multi-layer graphene coat the nickel-cobalt-manganese composite oxidation The upper and lower layers of the material reduce the direct contact between the positive electrode material and the electrolyte and slow down the occurrence of side reactions between them. Second, the graphene-treated multilayer graphene itself has excellent conductivity and enhances the conductivity of the nickel-cobalt-manganese composite oxide And the transferability of electrons in the pole piece, to achieve the extension of the cycle life of the nickel-cobalt-manganese composite oxide.

The invention provides a method for manufacturing a ternary cathode material. The method includes: performing a mixing process and an air pressurization process on a nickel-cobalt-manganese composite oxide and a graphene to form a ternary cathode material. The film diameter is between 10~100um.

In an embodiment, the ternary positive electrode material (NMC) is any one of NMC442, NMC111, NMC622, NMC701515, NMCB11 Nickel-cobalt-manganese ternary cathode materials with different proportions or combinations thereof, but not limited to this.

In one embodiment, the mixing process is a ternary cathode material with 0.5 to 5 wt% of multi-layer graphene, mechanically ground for 30 to 300 minutes, wherein the grinding method is dry ball milling, wet ball milling, planetary mixing or Any one or combination of dry grinding.

In one embodiment, the graphene is graphitized multi-layer graphene, the heat treatment temperature of the graphene is between 1500 and 2300°C, and the sheet diameter of the graphene is between 10 and 100 um, preferably Between 30~50um.

In one embodiment, the air pressurization process is to lay the ternary positive electrode material on a stainless steel square vessel and pressurize the air with air. The pressure of the air pressurization is between 5 and 15 kg/m ² .

In one embodiment, the mixing process and the air pressurization process are performed simultaneously.

In one embodiment, the mixing process and the air pressurization process are performed simultaneously.

Example 1: MLG (graphene) equivalent to 1.0 wt% (weight percent) of NMC (ternary positive electrode material) and NMC are ground for 30 minutes, and the resulting MLG/NMC/MLG active material powder is proportional to the active material ：Guidant: The adhesive is mixed at 100:5:3. In the process, the adhesive PVDF is first dissolved with the solvent NMP, and then the active material and the guiding agent are mixed in a dry blending mode, and then the solution of the adhesive is added. This slurry was applied on aluminum foil by doctor blade coating method, this sample became MLG/NMC/MLG 1.0wt%.

Example 2: MLG and MNC equivalent to 1.0 wt% of NMC were ground for 30 minutes, and then MLG/NMC coating was performed with an air pressure of 10 kg/m ² . The obtained P-MLG/NMC active material powder is mixed according to the proportion of active material: guide agent: adhesive: 100:5:3. In the process, the adhesive PVDF is first dissolved with the solvent NMP, and then the active material and auxiliary After the admixture is mixed by dry blending, the solution of the adhesive is added, and the slurry is coated on the aluminum foil by knife coating. This sample becomes P-MLG/NMC 1.0wt%.

Example 3: MLG and NMC graphitized at 2300°C equivalent to MCN 1.0Wt% were ground for 30 minutes, and then MLG/NMC/MLG coated with an air pressure of 10 kg/m ² . The obtained G-MLG/NMC active material powder is mixed according to the proportion of active material: guide agent: adhesive: 100:5:3. In the process, the adhesive PVDF is first dissolved with the solvent NMP, and then the active material and auxiliary After the admixture is mixed by dry mixing, the solution of the adhesive is added, and the slurry is coated on the aluminum foil by doctor blade coating. This sample becomes PG-MLG/NMC 1.0wt%.

Comparative Example 1: Active material: guide agent: adhesive: 100:5:3 for mixing. In the process, the PVDF adhesive first dissolves with the solvent NMP, and then the active material and the guide agent are mixed by dry mixing Then add the solution of the adhesive, and apply the slurry to the aluminum foil by knife coating. This sample becomes NMC.

The PG-MLG/NMC positive electrode material of the present invention is mixed with a binder and a conductive additive into a slurry according to a certain ratio, and it is coated on a 15 μm thick aluminum foil, the solvent is first dried at 80 ℃, and then enter the oven to Vacuum baking at 110°C for 24 hours to completely remove the solvent. The completed plate is cut with a circle (12Φ) with a diameter of 12mm Next, make a CR2032 button-type lithium ion secondary battery, and conduct a half-cell (counter electrode lithium metal (15mm diameter, 15Φ)) capacity test, using 1.0M LiPF6 in EC (ethylene carbonate): DEC (diethylene carbonate):=1:1 electrolyte in solvent, use equipment brand model BAT-750B for measuring capacitance.

Please refer to the first picture, the second picture and the third picture, the first picture is the SEM (scan electron microscope) picture of the embodiment 1 NMC/MLG of the present invention, and the second picture is the 3P-G-MLG/NMC embodiment of the present invention SEM (scan electron microscope) picture, the third picture is the SEM (scan electron microscope) picture of the comparative example 1NMC of the present invention. From the picture 1, it can be observed that the MLG only exists beside the NMC, and the picture 2 can be observed to be processed by the air pressurization method. After that, G-MLG covered the upper and lower layers of NMC in a curved shape, which was closer to the ternary cathode material.

Please refer to the fourth graph and Table 1. The fourth graph is the half-cycle long-cycle charge and discharge test chart of the embodiments 1 to 3 and the comparative example 1 of the present invention. The fourth graph is the charging and discharging of 0.1 C for each implementation and comparative example 10-turn discharge capacity map, operating voltage range is 2.7~4.25V, charge-discharge cycle rate is 0.1C, (1C=180mA g-1), Table 1 is the half-cell power of Examples 1~3 and Comparative Example 1. According to the results of the fourth figure and Table 1, the capacitance of the samples added with MLG is slightly higher than that in Comparative Example 1, which means that the addition of MLG contributes to the conductivity of the positive electrode material; the sample of Example 3 Either the capacitance or the retention is the best, which represents that the multi-layer graphene process by air pressure coating graphitization is helpful to improve the capacitance and cycle life of the cathode material.

Although the theoretical capacity of nickel-cobalt-manganese composite oxide is about 275mAh g ^-1 , which is much higher than other types of cathode materials, the cycle life of this material is lower than other types of cathode materials, making the use of this material greatly challenge. The higher the proportion of nickel (Ni _x ) in the nickel-cobalt-manganese composite oxide (LiNixMn _y Co _z O ₂ , NMC), the higher the capacitance of the material, but the inevitable lattice misalignment of nickel and lithium ions occurs in the first cycle , Reducing the electric capacity by about 10%, and the subsequent side reaction may continue to occur due to the contact of the electrolyte, causing the battery to decline. Graphene has excellent flexibility, and because of its excellent conductivity, it can improve the conductivity of the positive electrode material. The ternary cathode material manufactured by the manufacturing method of the present invention can slow down the side reaction of the ternary cathode material. The outermost layer of graphene can isolate the direct contact of the electrolyte, and can also improve the contact between the NMC and the conductive agent, and enhance the overall pole piece. Conductive network.

During the charge-discharge cycle of the high-nickel ternary cathode material, Ni ⁴⁺ comes into contact with the electrolyte to produce side reactions, causing the material structure to be destroyed. The surface-coated stable nano-layer is an effective method to improve the high-nickel ternary cathode material. This surface modification layer can be divided into an inert coating layer and an electrochemically active coating layer. The coated multi-layer graphene is an electrochemically active coating layer, which not only effectively slows down the side reaction caused by the contact between the electrolyte and the NCM, increases its stability, but also acts as a path for lithium ion intercalation and desorption, improving the electrochemical performance of the nickel-cobalt-manganese composite oxide characteristic.

The above-mentioned embodiments are only illustrative of the characteristics and effects of this creation, and are not intended to limit the scope of the substantive technical content of this creation. Anyone who is familiar with this skill can modify and change the above embodiments without violating the spirit and scope of creation. Therefore, the scope of protection of the rights of this creation should be as listed below in the scope of patent application.

Claims (7)

A method for manufacturing a ternary cathode material includes: performing a mixing process and an air pressure process on a nickel-cobalt-manganese composite oxide and a graphene to form a graphene-coated ternary cathode material, wherein the graphene The sheet diameter is between 10 and 100 μm, and the pressure of the air pressurization process is between 5 and 15 kg/m ² . The method for manufacturing a ternary positive electrode material as described in item 1 of the patent application scope, wherein the mixing process is dry ball milling, wet ball milling, planetary mixing or dry grinding. The method for manufacturing a ternary positive electrode material as described in item 1 of the patent application scope, wherein the mixing process is based on the graphene and the nickel-cobalt with a weight percentage of nickel-cobalt-manganese composite oxide of 0.5-5 Manganese composite oxide mixed. The method for manufacturing a ternary positive electrode material as described in item 1 of the patent application scope, wherein the graphene is graphitized multilayer graphene, and the heat treatment temperature of the graphene is between 1500 and 2300°C. The method for manufacturing a ternary positive electrode material as described in item 1 of the patent application scope, wherein the mixing process and the air pressurization process are performed simultaneously. The method for manufacturing a ternary positive electrode material as described in item 1 of the scope of the patent application, wherein the air pressurization process is started after the completion of the mixing process. The method for manufacturing a ternary positive electrode material as described in item 1 of the patent application scope, wherein the mixing process is dry grinding, and the grinding time is between 30 and 100 minutes.

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