Key technology for coating anode of lithium ion capacitor

Abstract

The invention relates to a key technology for coating a positive electrode of a lithium ion capacitor. Commercial activated carbon and hard carbon (HC) are respectively used as positive and positive electrode active materials to assemble the lithium ion capacitor. The invention relates to a key technology for coating a positive electrode, namely selection of a binder system. Specifically, the positive electrode material is composed of the following components in percentage by mass: 88-92% of a positive electrode main material, 5-7% of a conductive agent, 1-2% of water-based green pollution-free sodium carboxymethyl cellulose (CMCC) serving as a binder and 2-3% of styrene butadiene rubber emulsion (SBR). By adjusting the ratio of the positive electrode main material to the sodium carboxymethyl cellulose and adding the butadiene styrene rubber emulsion in a proper ratio into the positive electrode slurry after the ratio of the positive electrode main material to the sodium carboxymethyl cellulose is adjusted, the performance of the positive electrode plate is effectively improved, and the electrochemical performance of the lithium ion capacitor is effectively improved.

Description

Technical Field

[0001] The present invention provides a method for preparing a lithium ion capacitor, and in particular relates to a key technology for coating a positive electrode of a lithium ion capacitor. Background Art

[0002] With the continuous development and progress of science and technology, various portable electronic devices, such as smart phones and laptops, have been widely used, and people are increasingly dependent on electronic products. At the same time, these electronic devices have increasingly stringent requirements for the performance of chemical power sources. Lithium-ion capacitors are widely used in electronic products for their advantages such as high energy density, stable voltage, no memory effect and green environmental protection. With the continuous expansion of the application field of lithium-ion capacitors, people have higher and higher requirements for their electrochemical performance. There are many factors that affect the electrochemical performance of lithium-ion capacitors, such as positive and negative electrode materials, positive and negative electrode capacity matching in the design, charging and discharging mode, and electrolyte volume. However, in the production process of lithium-ion lithium-ion capacitors, the bonding strength of the binder in the positive electrode sheet to the active material and the selection of the appropriate ratio of the two will also have a huge impact on the electrochemical performance of lithium-ion capacitors. When the amount of binder is small, the active material load will be unstable and the material will fall off. When the amount of binder is large, it will affect the conductivity of the capacitor and the problem of low energy density. On the other hand, at present, a water-based binder for lithium-ion batteries has been used in production. Water-based adhesives have the following advantages: low material cost, no pollution, no need to treat waste gas; low heating temperature and low energy consumption compared to oil-based adhesives; no explosion hazard when water vapor is mixed with air, which is conducive to the cyclic heating of the electrode drying process. At present, most manufacturers have used water-based adhesive systems for the negative electrode, but oil-based adhesive systems are still used for the positive electrode. The reason is that the battery made with the water-based adhesive system has poor stability and the cycle performance is not as good as the oil-based system. However, judging from the effects of the water-based adhesives that have been used, finding a more suitable adhesive system and studying the better matching performance of battery materials with it are still the current research hotspots. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a key technology for coating the positive electrode of a lithium ion capacitor to solve the problem raised in the above background technology. The lithium ion capacitor comprises a shell, a battery cell placed inside and an electrolyte impregnated in the battery cell, and the battery cell is obtained by winding or laminating a positive electrode sheet, a positive electrode sheet and a separator placed between the positive electrodes.

[0004] Step 1: Prepare positive electrode slurry, the aqueous positive electrode slurry includes positive electrode active material, conductive agent, positive electrode binder and solvent. According to the material ratio, the positive electrode active material, conductive agent, positive electrode binder and solvent are mixed and stirred to form positive electrode slurry.

[0005] Step 2: The positive electrode sheet comprises a positive electrode coating layer and a positive electrode current collector, characterized in that the content of the binder used is 1-2% CMCC and 2-3% SBR.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: Preferably, the conductive agent is KS-6, and the positive electrode active material is HC.

[0007] The preferred electrolyte is LiPF6 or LiClO4.

[0008] The preferred content of the conductive agent is 5%-7%, the content of the binder used is 1-2% sodium carboxymethyl cellulose and 2-3% styrene-butadiene rubber latex, and the content of the slurry is 88%-92%.

[0009] Beneficial Effects of the Invention

[0010] (1) A high-capacitance, high-rate lithium-ion capacitor was prepared.

[0011] (2) Provides a key technology for positive electrode coating.

[0012] (3) The capacitor prepared by the present invention has a simple process and is easy to realize industrial production. DETAILED DESCRIPTION

[0013] The present invention is further described below in conjunction with embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its contents. Example

[0014] This embodiment provides a method for preparing a lithium ion capacitor, and the process of a pole piece is described below by taking it as an example.

[0015] The specific steps are as follows: Step 1: Add 1% sodium carboxymethyl cellulose and 2% styrene-butadiene rubber latex into a certain amount of deionized water, and stir with a vacuum mixer until they are evenly dispersed. The content is 3%.

[0016] Step 2: Weigh a certain amount of conductive agent, add it with a glass rod while stirring until it is completely immersed in water, mix it with a vacuum mixer for 4 hours, and disperse it in a disperser for a certain period of time; its content accounts for 5% Step 3: Weigh the corresponding amount of activated carbon, add it while stirring with a glass rod, stir until it is completely immersed in water, stir it with a vacuum stirrer for a certain period of time, then stir it with a high shear disperser for a certain period of time, and then stir it with a vacuum stirrer for a certain period of time until the slurry is uniform; its content accounts for 92%.

[0017] Step 4: After obtaining the positive electrode slurry for making the positive electrode sheet, coating is started on an automatic coating machine. The coating speed is 0.2 m / min, and the coating method is roller type. The temperature of the oven is set to 120° C.

[0018] Step 5: Use a roller press to roll the pole piece.

[0019] Step 6: Cut into shapes with the same area, dry in a dryer, use a laminating machine to cross-laminate the positive and negative electrodes, separate them with a diaphragm in the middle, connect the positive and negative electrodes, and drain at one end. Then add 40% of the mass of metallic lithium according to the positive electrode active material, and then embed the calculated metallic lithium into the surface of the positive electrode fluid by rolling on the surface of the positive electrode fluid to achieve lithium embedding on the surface of the negative electrode.

[0020] Step 7: The tabs are welded, electrolyte is added into the glove box, vacuum-sealed and left to stand, and the lithium-ion capacitor is obtained.

[0021] Example

[0022] Step 1: Add 2% sodium carboxymethyl cellulose and 2% styrene-butadiene rubber latex into a certain amount of deionized water, and stir with a vacuum mixer until they are evenly dispersed. The content is 4%.

[0023] Step 2: Weigh a certain amount of conductive agent, add it with a glass rod while stirring until it is completely immersed in water, mix it with a vacuum mixer for 4 hours, and disperse it in a disperser for a certain period of time; its content accounts for 5% Step 3: Weigh the corresponding amount of activated carbon, add it while stirring with a glass rod, stir until it is completely immersed in water, stir it with a vacuum stirrer for a certain period of time, then stir it with a high shear disperser for a certain period of time, and then stir it with a vacuum stirrer for a certain period of time until the slurry is uniform; its content accounts for 91%.

[0024] Step 4: After obtaining the positive electrode slurry for making the positive electrode sheet, coating is started on an automatic coating machine. The coating speed is 0.2 m / min, and the coating method is roller type. The temperature of the oven is set to 120° C.

[0025] Step 5: Use a roller press to roll the pole piece.

[0026] Step 6: Cut into shapes with the same area, dry in a dryer, use a laminating machine to cross-laminate the positive and negative electrodes, separate them with a diaphragm in the middle, connect the positive and negative electrodes, and drain at one end. Then add 50% of the mass of metallic lithium according to the positive electrode active material, and then embed the calculated metallic lithium into the surface of the positive electrode fluid by rolling on the surface of the positive electrode fluid to achieve lithium embedding on the surface of the negative electrode.

[0027] Step 7: The tabs are welded, electrolyte is added into the glove box, vacuum-sealed and left to stand, and the lithium-ion capacitor is obtained. Example

[0028] Step 1: Add 2% sodium carboxymethyl cellulose and 3% styrene-butadiene rubber latex into a certain amount of deionized water, and stir with a vacuum mixer until they are evenly dispersed. The content is 5%.

[0029] Step 2: Weigh a certain amount of conductive agent, add it with a glass rod while stirring until it is completely immersed in water, mix it with a vacuum mixer for 4 hours, and disperse it in a disperser for a certain period of time; its content accounts for 5% Step 3: Weigh the corresponding mass of activated carbon HC, add it while stirring with a glass rod, stir until it is completely immersed in water, stir it with a vacuum stirrer for a certain time, then stir it with a high shear disperser for a certain time, and then stir it with a vacuum stirrer for a certain time until the slurry is uniform; its content accounts for 90%.

[0030] Step 4: After obtaining the positive electrode slurry for making the positive electrode sheet, coating is started on an automatic coating machine. The coating speed is 0.2 m / min, and the coating method is roller type. The temperature of the oven is set to 120° C.

[0031] Step 5: Use a roller press to roll the pole piece.

[0032] Step 6: Cut into shapes with the same area, dry in a dryer, use a laminating machine to cross-laminate the positive and negative electrodes, separate them with a diaphragm in the middle, connect the positive and negative electrodes, and drain at one end. Then add 60% of the mass of metallic lithium according to the positive electrode active material, and then embed the calculated metallic lithium into the surface of the positive electrode fluid by rolling on the surface of the positive electrode fluid to achieve lithium embedding on the surface of the negative electrode.

[0033] Step 7: The tabs are welded, electrolyte is added into the glove box, vacuum-sealed and left to stand, and the lithium-ion capacitor is obtained.

[0034] The present invention improves the material shedding phenomenon of the prepared pole piece by adjusting the type and proportion of the binder used, thereby improving the pole piece quality. The capacitor made of the pole piece is tested for its electrochemical properties, and the results show that the internal resistance is low, the chemical properties are stable, and the capacity is high.

[0035] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to perform equivalent replacements on parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A key technology for positive electrode coating of lithium ion capacitors.

2. The large-capacity lithium-ion capacitor as claimed in claim 1 comprises a shell, a battery cell placed inside and an electrolyte impregnated in the battery cell, wherein the battery cell is obtained by winding or laminating a positive electrode sheet, a positive electrode sheet and a separator placed between the positive electrodes.

3. As claimed in claim 1, the key technology of positive electrode coating is characterized by : Choice of binder system.

4. As claimed in claim 2, the electrolyte is a type of LiPF6, LiClO4, the conductive agent is KS-6, and the binder is sodium methyl cellulose (CMCC) and styrene-butadiene rubber latex.

5. As claimed in claim 3, the main material and the binder are in suitable proportions, namely, 88-92% of the main material, 5-7% of the conductive agent, 1-2% of sodium carboxymethyl cellulose (CMCC) and 2-3% of styrene-butadiene rubber latex (SBR).