Preparation process of lithium battery negative plate formula

Abstract

The invention discloses a preparation process of a lithium battery negative electrode plate formula, which comprises the following steps: respectively preparing three tanks of negative electrode slurry by using a 5L stirring tank, respectively adding 3000g of graphite, 16.6 g of sodium carboxymethyl cellulose and 24.9 g of a conductive agent into the stirring tank, carrying out dry mixing, carrying out rotation at 300r and revolution at 15r, and carrying out dry mixing for 45 minutes; adding 800g of deionized water, carrying out autorotation at 300r and revolution at 15r, and stirring for 30 minutes; 405 g of polyacrylic acid and 300 g of deionized water are added, rotation is conducted at the speed of 300 r, revolution is conducted at the speed of 15 r, and stirring is conducted for 30 min; then adding 270g of polyacrylic acid and 200g of deionized water, rotating at 300r and revolving at 15r, and stirring for 30 minutes; and adding a certain amount of deionized water to adjust the viscosity, adding 54.52 g of butadiene styrene rubber, rotating at 500r and revolving at 10r, and stirring for 30 minutes to complete the preparation of the slurry of the negative electrode formula. According to the preparation process of the lithium battery negative electrode plate formula, the negative electrode formula is improved, the stability of the slurry and the cycle performance of the battery are improved, and the battery capacity is better.

Description

Technical Field

[0001] This invention belongs to the field of lithium batteries, and particularly relates to a preparation process for a lithium battery negative electrode formulation. Background Technology

[0002] Currently, during battery cycling, the structure of the electrode changes due to the insertion and extraction of lithium-ion batteries. If the bonding strength is too weak, the active material of the electrode may fall off after a period of cycling, resulting in a sharp drop in cycle life. Therefore, it is necessary to ensure a certain bonding strength.

[0003] In practical applications, CMC (sodium carboxymethyl cellulose) and SBR (styrene-butadiene rubber) are generally used together as the negative electrode. Currently, a certain amount of PAA (polyacrylic acid) is usually added to the negative electrode formulation to replace part of the SBR, which reduces costs and improves battery performance. However, because PAA is highly rigid and the electrode sheet is prone to brittleness, it is usually used in combination with CMC / SBR.

[0004] Therefore, it is urgent to design a preparation process for lithium battery anode sheet formulations to solve the problems mentioned above. Summary of the Invention

[0005] To address the technical problem mentioned in the background art of adding a certain amount of PAA to replace part of SBR, which results in PAA having high rigidity and making the electrode sheet prone to brittleness, thus usually being used in combination with CMC / SBR, a preparation process for a lithium battery negative electrode sheet formulation is provided to solve the problems of poor stability of negative electrode slurry, low battery capacity utilization, and poor battery cycle performance.

[0006] To achieve the above objectives, the specific technical solution for the preparation process of the lithium battery negative electrode formulation of the present invention is as follows: A process for preparing a lithium-ion battery negative electrode formulation, using a 5L stirring tank to prepare three negative electrode slurries, includes the following steps: S1. Add 3000g of graphite, 16.6g of sodium carboxymethyl cellulose and 24.9g of conductive agent to the mixing tank and dry mix them at 300r rotation and 15r revolution for 45 minutes. S2. Add 800g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S3. Add 405g of polyacrylic acid and 300g of deionized water, and stir for 30 minutes at a rotation speed of 300r and a revolution speed of 15r. S4. Add 270g of polyacrylic acid and 200g of deionized water, and stir for 30 minutes at 300r rotation and 15r revolution. S5. Add 600g of deionized water and 12.5g of plasticizer. First, rotate the mixture at 1500r and then rotate it around the sun at 20r. Stir for 30 minutes and then scrape the mixture. S6. Then rotate at 1500 r and revolve at 20 r for 90 min, and test the viscosity, fineness and solid content. S7. Add a certain amount of deionized water to adjust the viscosity, add 54.52g of styrene-butadiene rubber, and stir for 30 minutes at a rotation speed of 500r and a revolution speed of 10r to complete the preparation of the negative electrode slurry.

[0007] Furthermore, the prepared negative electrode slurry is coated, and copper foil is used as the negative electrode current collector to prepare the negative electrode sheet.

[0008] Furthermore, the coated negative electrode sheet is rolled, and the rolled negative electrode sheet is then cut, brushed, and picked to complete the sheet production.

[0009] Furthermore, the selected negative electrode sheet is baked at 85℃ under vacuum for 8-12 hours.

[0010] Furthermore, the baked negative electrode sheet and separator are stacked and coated with adhesive, with the negative electrode sheet completely covering the positive electrode sheet and the separator completely covering the negative electrode sheet to avoid short circuits.

[0011] Furthermore, the stacked battery cells undergo ultrasonic welding of the tabs, high-temperature adhesive covering of the welding positions, and stamping and top / side sealing of the aluminum-plastic film packaging bags.

[0012] Furthermore, the encapsulated battery cells are hot-pressed with the following parameters: 85℃, 0.5MPa, and 2min.

[0013] Furthermore, after hot pressing, a short-circuit test and battery drying are performed. The battery is baked at 85°C for 24 hours to remove all the moisture in the battery, so that the moisture content of the negative electrode, positive electrode, and separator is less than 300 ppm.

[0014] Further, the cells undergo formation, aging, secondary sealing, and capacity testing, followed by inspection of the finished cells to complete the cell manufacturing process.

[0015] The preparation process of the lithium battery negative electrode formulation of the present invention has the following advantages: The negative electrode slurry is prepared by dry mixing and stirring graphite, sodium carboxymethyl cellulose, and a conductive agent, followed by the addition of polyacrylic acid and deionized water in two batches to achieve a more uniform overall mixing. Plasticizers and styrene-butadiene rubber are then added. This application improves the negative electrode formulation, enhancing the slurry's stability and battery cycle performance, and allowing for better battery capacity utilization. Attached Figure Description

[0016] Figure 1 Process flow diagram for preparing the new negative electrode slurry; Figure 2 This is a process flow diagram for preparing the positive electrode slurry. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0019] The following is a reference to the appendix. Figures 1 to 2 The preparation process of the lithium battery negative electrode formulation of the present invention is described.

[0020] Example 1: like Figure 2 As shown, the preparation process of the lithium battery negative electrode formulation in this invention includes the preparation of the positive electrode slurry, stirring the positive electrode with the formulation parameters in Table 1, using a 35L stirring tank, and mainly includes the following steps: S1. First, add 6300.5g of NMP (N-methylpyrrolidone), then add 331.6g of PVDF (polyvinylidene fluoride). Pre-stir for 10 minutes at 500r rotation and 10r revolution respectively. After stirring, scrape the material and then stir rapidly for 360 minutes at 2000r rotation and 20r revolution to complete the glue preparation. N-methylpyrrolidone is the positive electrode solvent, and polyvinylidene fluoride is the positive electrode binder for lithium batteries.

[0021] S2. Add 165.8g of SP and 1658g of CNTs (conductive paste), rotate at 2000r and revolve at 25r for 120 minutes to complete the preparation of conductive adhesive. S3. Add 8000g of lithium iron phosphate, rotate at 500r and revolve at 20r, and pre-stir for 10 minutes. During this process, start the cooling water. S4. Add 500g of NMP, and pre-stir for 10 minutes at 500 rpm and 20 rpm. Finally, add 8000g of lithium iron phosphate, and pre-stir for 10 minutes at 500 rpm and 20 rpm. S5. Then, rotate at 2500 rpm and revolve at 25 rpm for 180 minutes. Finally, add 2000g of NMP and rotate at 2500 rpm and revolve at 25 rpm for 30 minutes. Test the viscosity, fineness, and solid content. S6. Add a certain amount of NMP to adjust the viscosity and complete the preparation of the positive electrode slurry. Table 1 Example 2: The conventional negative electrode formulation A was prepared using the formulation parameters in Table 1. Three negative electrode slurries were prepared in 5L mixing tanks, mainly including the following steps: S1. Add 3000g of graphite, 16.6g of CMC (sodium carboxymethyl cellulose), and 24.9g of SP (conductive agent) and dry mix for 45 minutes with a rotation of 300r and a revolution of 15r. S2. Add 800g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S3. Add 280g of PAA (polyacrylic acid) and 300g of deionized water, and stir for 30 minutes at 300r rotation and 15r revolution. S4. Add 187g of PAA (polyacrylic acid) and 200g of deionized water, and stir for 30 minutes at 300r rotation and 15r revolution. S5. Add 600g of deionized water and 12.5g of plasticizer. First, rotate the mixture at 1500r and then rotate it around the sun at 20r. Stir for 30 minutes and then scrape the mixture. S6. Then rotate at 1500 r and revolve at 20 r for 90 min, and test the viscosity, fineness and solid content. S7. Add a certain amount of deionized water to adjust the viscosity, add 85.67g of SBR, and stir for 30 minutes at a rotation speed of 500r and a revolution speed of 10r to complete the preparation of the slurry of the conventional negative electrode formulation A.

[0022] Example 3: The conventional negative electrode formulation B was prepared using the formulation parameters in Table 1. Three negative electrode slurries were prepared in 5L mixing tanks, mainly including the following steps: S1. First, add 3000g of graphite, 16.6g of CMC, and 24.9g of SP and dry mix them at 300r rotation and 15r revolution for 45 minutes. S2. Add 800g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S3. Add 343g of PAA and 300g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S4. Add 228g of PAA and 200g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S5. Add 600g of deionized water and 12.5g of plasticizer. First, rotate the mixture at 1500r and then rotate it around the sun at 20r. Stir for 30 minutes and then scrape the mixture. S6. Then rotate at 1500 r and revolve at 20 r for 90 min, and test the viscosity, fineness and solid content. S7. Add a certain amount of deionized water to adjust the viscosity, add 70.09g of SBR, and stir for 30 minutes at a rotation speed of 500r and a revolution speed of 10r to complete the preparation of the slurry of the conventional negative electrode formula B.

[0023] like Figure 1 As shown, Example 4 is a preferred embodiment: To prepare the new negative electrode formulation C, the negative electrode was stirred according to the formulation parameters in Table 1. Three negative electrode slurries were prepared using 5L stirring tanks. The main steps included: S1. Add 3000g of graphite, 16.6g of CMC, and 24.9g of SP and dry mix at 300r rotation and 15r revolution for 45 minutes. S2. Add 800g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S3. Add 405g of PAA and 300g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S4. Add 270g of PAA (polyacrylic acid) and 200g of deionized water, and stir for 30 minutes at 300 rpm rotation and 15 rpm revolution. S5. Add 600g of deionized water and 12.5g of plasticizer. First, rotate the mixture at 1500r and then rotate it around the sun at 20r. Stir for 30 minutes and then scrape the mixture. S6. Then rotate at 1500 r and revolve at 20 r for 90 min, and test the viscosity, fineness and solid content. S7. Add a certain amount of deionized water to adjust the viscosity, add 54.52g of SBR, and stir for 30 minutes at a rotation speed of 500r and a revolution speed of 10r to complete the preparation of the slurry of the new negative electrode formula C.

[0024] The prepared positive electrode slurry was subjected to the following operations with negative electrode slurries prepared by conventional formula A, conventional formula B, and new formula C, respectively, mainly including: S1. Coat the prepared positive electrode slurry with the negative electrode slurry prepared by conventional formula A, conventional formula B and new formula C according to the areal density in Table 1. Aluminum foil is used for the positive electrode current collector and copper foil is used for the negative electrode current collector to prepare the coated positive and negative electrode sheets that meet the requirements. S2. Roll the prepared coated electrode sheet with the compaction density in Table 1 to prepare the roll-pressed positive and negative electrode sheets that meet the requirements. S3. After rolling, the positive and negative electrode sheets are cut, brushed, and picked to complete the sheet making process. S4. Bake the selected electrode sheets: vacuum bake the positive electrode at 110℃ for 8-12 hours and the negative electrode at 85℃ for 8-12 hours. S5. Stack and coat the baked positive and negative electrode sheets with the separator. The negative electrode sheet must completely cover the positive electrode sheet, and the separator must completely cover the negative electrode sheet to avoid short circuits. S6. After the cells are stacked, ultrasonic welding of the tabs is performed, high-temperature adhesive is applied to the welding positions, and aluminum-plastic film packaging bags are punched and sealed from top to side. S7. Perform hot pressing on the packaged battery cell. The hot pressing parameters are set to 85℃, 0.5MPa, and 2min. S8. After hot pressing, perform a short-circuit test (select short-circuited cells) and dry the battery. Use 85℃ and bake for 24 hours to remove all the moisture from the battery. Requirements: The moisture content of both the positive and negative electrode plates and the separator must be less than 300 ppm; S9. Perform cell formation, aging, secondary sealing and capacity testing, and then inspect the finished cells to complete the cell preparation.

[0025] Finally, the performance of conventional formula A, conventional formula B, and new formula C are compared in various aspects: Table 2 Table 3 Based on Tables 2 and 3, the following results were obtained: Formula C exhibited the highest viscosity and the best stability. Furthermore, the trend of solid content variation indicated that Formula C had a low sedimentation rate. Table 4 According to Table 4, the peel strength of the electrode before rolling is increased when using the new formulation C; the peel strength after rolling is decreased. Table 5 According to Table 5, the resistivity of the electrode before rolling is similar to that of group B; the resistivity decreases after rolling. Table 6 According to Table 6, the gas production of batteries using the new formula C is significantly reduced. Table 7 According to Table 7, the internal resistance of each stage is basically the same as that of the conventional formula. Table 8 According to Table 8, the capacity performance of batteries using the new formula C is significantly improved at high rates. Table 9 According to Table 9, the DC internal resistance of the battery using the new formula C is increased to a certain extent. Table 10 According to Table 10, the rate retention rate of the battery using the new formula C is basically the same as that of the conventional formula. Table 11 According to Table 11, the charge retention and recovery rates are as follows: the rate retention rate of the battery using the new formula C is basically the same as that of the conventional formula. Table 12 According to Table 12, the room temperature cycling performance of the battery using the new formula C is better than that of the conventional formula. Table 13 According to Table 13, the high-temperature cycling performance of batteries using the new formulation C is better than that of conventional formulations.

[0026] Therefore, the preparation process based on the lithium battery anode sheet formulation improves the stability of the slurry and the battery cycle performance by modifying the anode formulation, thus enabling the battery capacity to be better utilized.

[0027] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A preparation process for a lithium battery negative electrode formulation, characterized in that, Three negative electrode slurries were prepared using a 5L mixing tank, including the following steps: S1. Add 3000g of graphite, 16.6g of sodium carboxymethyl cellulose and 24.9g of conductive agent to the mixing tank and dry mix them at 300r rotation and 15r revolution for 45 minutes. S2. Add 800g of deionized water, rotate at 300r and revolve at 15r for 30 minutes; S3. Add 405g of polyacrylic acid and 300g of deionized water, and stir for 30 minutes at a rotation speed of 300r and a revolution speed of 15r. S4. Add 270g of polyacrylic acid and 200g of deionized water, and stir for 30 minutes at 300r rotation and 15r revolution. S5. Add 600g of deionized water and 12.5g of plasticizer. First, rotate the mixture at 1500r and then rotate it around the sun at 20r. Stir for 30 minutes and then scrape the mixture. S6. Then rotate at 1500 r and revolve at 20 r for 90 min, and test the viscosity, fineness and solid content. S7. Add a certain amount of deionized water to adjust the viscosity, add 54.52g of styrene-butadiene rubber, and stir for 30 minutes at a rotation speed of 500r and a revolution speed of 10r to complete the preparation of the negative electrode slurry.

2. The preparation process of the lithium battery negative electrode formulation according to claim 1, characterized in that, The prepared negative electrode slurry is coated, and copper foil is used as the negative electrode current collector to prepare the negative electrode sheet.

3. The preparation process of the lithium battery negative electrode formulation according to claim 2, characterized in that, The coated negative electrode sheet is rolled, and then the rolled negative electrode sheet is cut, brushed, and picked to complete the sheet production.

4. The preparation process of the lithium battery negative electrode formulation according to claim 3, characterized in that, The selected negative electrode sheet is baked at 85℃ under vacuum for 8-12 hours.

5. The preparation process of the lithium battery negative electrode formulation according to claim 4, characterized in that, The baked negative electrode sheet and separator are stacked and coated with adhesive, with the negative electrode sheet completely covering the positive electrode sheet and the separator completely covering the negative electrode sheet to avoid short circuits.

6. The preparation process of the lithium battery negative electrode formulation according to claim 5, characterized in that, After the cells are stacked, ultrasonic welding of the electrode tabs is performed, high-temperature adhesive is applied to the welding positions, and aluminum-plastic film packaging bags are punched and sealed from top to side.

7. The preparation process of the lithium battery negative electrode formulation according to claim 6, characterized in that, The encapsulated battery cells are then subjected to hot pressing with the following parameters: 85℃, 0.5MPa, and 2min.

8. The preparation process of the lithium battery negative electrode formulation according to claim 7, characterized in that, After hot pressing, a short-circuit test and battery drying are performed. The battery is baked at 85°C for 24 hours to remove all the moisture in the battery, so that the moisture content of the negative electrode, positive electrode, and separator is less than 300 ppm.

9. The preparation process of the lithium battery negative electrode formulation according to claim 8, characterized in that, The process involves cell formation, aging, secondary sealing, and capacity testing, followed by finished cell inspection to complete cell manufacturing.

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