Preparation method of anti-gel lithium supplementing positive electrode slurry and lithium supplementing positive electrode sheet

Abstract

The application discloses an anti-gel lithium supplementing positive electrode paste and a preparation method of a lithium supplementing positive electrode sheet, which comprises a positive electrode active material, a conductive agent, a binder composition and a lithium supplementing additive, wherein the binder composition is composed of a polymer with a first molecular weight and a polymer with a second molecular weight, the first molecular weight is greater than the second molecular weight, and the mass ratio is 4-9.5:6-0.5. Through the use of the double-component positive electrode binder with different molecular weights, the viscosity of the overall paste is reduced while the high adhesive force is ensured, and the flow performance is improved. The alkali source is released from the lithium supplementing material, and the uneven distribution can be alleviated by the good flowability, the problem of excessively high local alkali concentration can be solved, the defluorination reaction kinetics is reduced, and then the crosslinking degree is reduced. Meanwhile, the spatial distribution of the interpenetration of the high-molecular-weight molecules and the low-molecular-weight molecules reduces the probability of the reaction between the high-molecular-weight molecules, reduces the molecular weight increasing speed of the crosslinking network, delays the arrival of the gel point, and improves the lithium supplementing paste uniformity and the quality of the positive electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries and relates to a lithium replenishing slurry and a positive electrode sheet, particularly to a method for preparing an anti-gelling lithium replenishing positive electrode slurry and a lithium replenishing positive electrode sheet. Background Technology

[0002] During the first charge and discharge cycle of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the surface of the electrode material and at the solid-liquid interface of the electrolyte. The formation of the SEI film inevitably consumes some active lithium, leading to a decrease in initial charge and discharge efficiency and an increase in initial irreversible capacity. Lithium replenishment technology effectively solves the problem of decreased capacity during the first charge and discharge cycle by replenishing the active lithium consumed in the formation of the SEI film. Currently, cathode lithium replenishment additive technology has attracted much attention due to its advantages such as high safety, high compatibility with existing processes, and low investment cost. However, cathode lithium replenishment materials are sensitive to moisture and have high levels of residual alkali (lithium hydroxide LiOH, lithium carbonate LiCO3), posing significant challenges to the slurry preparation process. In particular, polyvinylidene fluoride (PVDF) cathode binders are widely used in cathodes and are highly susceptible to attack by alkaline groups, undergoing dehydrofluorination reactions to form carbon-carbon double bonds. The unsaturated double bonds between polymer chains react to form crosslinks, leading to gelation of the slurry. Gelated slurries exhibit reduced fluidity, leading to uneven material distribution and problems such as pinholes and particles in the electrode coating, thus degrading the electrode quality. Based on this background, the present invention provides an anti-gelling positive electrode lithium-filling slurry and a method for preparing the electrode.

[0003] CN110137433A discloses a method for replenishing lithium on the positive electrode of a lithium-ion battery. First, a positive electrode slurry is coated on the surface of the positive electrode, and then a positive electrode lithium replenishing additive is immediately sprayed on the surface of the positive electrode. This avoids the negative impact of the lithium replenishing additive on the positive electrode active material, greatly improves the first efficiency of the battery, thereby increasing the energy density of the battery and significantly improving the cycle performance of the battery.

[0004] CN111916752A provides a positive electrode sheet, its manufacturing method, and a secondary battery. The positive electrode sheet includes: a current collector and a first material layer coated on the current collector, and a second material layer coated on the first material layer. The first material layer includes a lithium-supplementing material, a first positive electrode active material, a first conductive agent, and a first binder. The second material layer includes a second positive electrode active material, a second conductive agent, and a second binder. By sequentially coating the first and second material layers onto the current collector, the second material layer can cover the first material layer, isolating air from the first positive electrode active material. This reduces the contact area between air and the lithium-supplementing material in the first material layer during manufacturing, reducing the corrosion of the lithium-supplementing material by air. Furthermore, the first material layer can supplement the second material layer with metal elements, improving the performance of the secondary battery prepared with this positive electrode sheet.

[0005] The aforementioned existing technologies all reduce the contact between the lithium replenishment material and the cathode slurry and shorten the exposure time of the lithium replenishment material to the environment through multiple coating processes, thereby reducing the impact of the lithium replenishment material on the stability of the slurry. However, multiple coatings increase the complexity of the coating process and raise production costs. In addition, multiple coatings cause uneven distribution of the lithium replenishment material in the electrode, leading to uneven lithiation of the active material in the subsequent formation stage.

[0006] CN113937254A discloses a lithium-ion additive for battery positive electrodes, a positive electrode sheet, its preparation method, and a method for preparing a lithium-ion battery. The method for preparing the lithium-ion additive for battery positive electrodes includes: mixing a lithium source and a nickel source and calcining them to obtain a lithium-rich material; mixing the lithium-rich material with water and washing it; and then drying it to obtain the lithium-ion additive for battery positive electrodes. By adding a water washing process, the residual alkali value of the positive electrode lithium-ion additive material is significantly reduced, and by adjusting the water washing process parameters, the residual alkali value of the positive electrode lithium-ion additive material can be further reduced. Simultaneously, the low-alkali positive electrode lithium-ion additive effectively alleviates the damage to the binder caused by residual alkali during the preparation of the positive electrode slurry, improves the fluidity of the positive electrode slurry, thereby achieving uniform coating and improving the manufacturing quality of the positive electrode sheet. Furthermore, under high-temperature conditions, the low-alkali positive electrode lithium-ion additive provided by this invention is not easily decomposed or reacts with the electrolyte solution, thereby effectively avoiding a decrease in battery performance.

[0007] The aforementioned technology adds additional washing and drying processes to reduce residual alkali and stabilize the slurry. However, the introduced water treatment process increases the complexity of the homogenization process and raises production costs. Furthermore, the exposure of the lithium-replenishing material to water leads to increased water content in subsequent slurries and electrodes, exacerbating side reactions in subsequent electrochemical reactions.

[0008] CN113745459A discloses a positive electrode slurry, its preparation method, and its application. The positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, a solvent, additives, and a lithium-supplementing material, wherein the additives are weak acids and / or weak acid anhydrides. This invention, by co-incorporating the weak acid or weak acid anhydride during the preparation of the positive electrode slurry, can neutralize residual alkali in the lithium-supplementing material, reduce the viscosity of the prepared slurry, and make the surface density distribution of the coated layer more uniform, which is beneficial for rolling and subsequent battery processing and use.

[0009] The aforementioned technology stabilizes the slurry by neutralizing the residual alkali from the lithium-filling materials through the introduction of acidic additives. However, the addition of additives reduces the proportion of active material, thus lowering the battery's energy density. Furthermore, the effects of acidic additives on the electrochemical system of lithium batteries are unclear, posing potential risks to battery cycle performance and other aspects.

[0010] Lithium-replenishing additives for positive electrodes are an effective technology for replenishing lithium in lithium-ion batteries. However, existing lithium-replenishing additives have a high residual alkali content on their surface, which can react with widely used PVDF binders, causing chemical gelation of the slurry, affecting the quality of the positive electrode sheet, and thus degrading battery performance.

[0011] CN110137433A, CN111916752A, and CN113937254A reduce the contact between the lithium-filling material and the positive electrode slurry, shorten the exposure time of the lithium-filling material in the environment, and reduce the residual alkali content on the surface of the lithium-filling material through step-by-step coating and water treatment processes, thereby mitigating the gelation process of the slurry. However, these technologies all overturn the conventional electrode homogenization coating process, greatly increasing the complexity of the electrode preparation process and raising production costs.

[0012] CN113745459A stabilizes the slurry by introducing acidic additives to neutralize the alkaline substances introduced by the lithium-ion battery supplementation material. However, the addition of additives reduces the proportion of active material, thereby lowering the battery's energy density. Furthermore, the effect of acidic additives on the electrochemical system of lithium-ion batteries is unclear, posing potential risks to battery cycle performance and other aspects. Summary of the Invention

[0013] To address the aforementioned issues, this invention provides an anti-gelling lithium-supplementing cathode slurry and a method for preparing lithium-supplementing cathode sheets. By using two-component cathode binders with different molecular weights, high adhesion (contributed by the high molecular weight component) is maintained while the overall viscosity of the slurry is reduced (contributed by the low molecular weight component), thus improving flow performance.

[0014] Since the alkali source in the slurry originates from the slow release of lithium-supplementing materials and is unevenly distributed, good fluidity can alleviate the problem of excessively high local alkali concentration, reduce the kinetics of the defluorination reaction, and thus reduce the degree of crosslinking. Simultaneously, the spatial distribution of high and low molecular weight molecules interpenetrates reduces the probability of reactions between high molecular weight molecules, slows the molecular weight growth rate of the crosslinking network, delays the arrival of the gel point, and improves the uniformity of the lithium-supplementing slurry and the quality of the electrode. This invention is simple to operate and fully compatible with existing electrode preparation processes. Furthermore, the binders used are all widely used positive electrode binders, ensuring high product safety and technological maturity.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] An anti-gel lithium-supplementing cathode slurry, comprising a cathode active material, a conductive agent, a binder composition, and a lithium-supplementing additive, wherein the mass ratio of the cathode active material, conductive agent, binder composition, and lithium-supplementing additive is 82.0–99.0 : 0–4.0 (excluding 0) : 1.0–4.0 : 0–10.0 (excluding 0), wherein the binder composition is composed of a polymer of a first molecular weight and a polymer of a second molecular weight, the first molecular weight being greater than the second molecular weight, and the mass ratio of the first molecular weight polymer to the second molecular weight polymer is 4–9.5 : 6–0.5.

[0017] As a preferred embodiment of the present invention, the polymer with the first molecular weight is a homopolymer or copolymer of vinylidene fluoride, and the polymer molecular weight is between 800,000 and 1,400,000.

[0018] As a preferred embodiment of the present invention, the polymer with the second molecular weight is a homopolymer or copolymer of vinylidene fluoride, and the polymer molecular weight is between 300,000 and 600,000.

[0019] As a preferred embodiment of the present invention, the polymer crystallinity is ≤50%, and more preferably, the polymer crystallinity is ≤35%.

[0020] As a preferred embodiment of the present invention, the polymer raw materials include vinylidene fluoride monomer, initiator, dispersant, emulsifier, solvent, chain transfer agent, chain terminator, as well as modified monomer and auxiliaries, and the polymerization process is one of suspension polymerization or emulsion polymerization.

[0021] In a preferred embodiment of the present invention, the conductive agent is at least one of conductive carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, and graphene.

[0022] As a preferred embodiment of the present invention, the positive electrode active material is selected from any one or a combination of at least two of lithium iron phosphate, nickel cobalt manganese positive electrode material, nickel cobalt aluminum positive electrode material, cobalt-free positive electrode material or lithium iron manganese phosphate positive electrode material.

[0023] As a preferred embodiment of the present invention, the positive electrode lithium supplementation additive is selected from Li3N, LiN3, Li2O2, Li2O, LiF, Li2S2, Li2S, Li2CO3, Li2C2O4, Li2S2O3, Li2S2O4, Li2S2O5, Li2S2O6, Li2S4O6, Li2M1O2, Li2M2O3, Li5M3O4, or Li6MnxM 4(1-x) At least one of O4, wherein M1 contains at least one of Ni, Mn, Cu, Fe, Cr or Mo; wherein M2 contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr or Ru; wherein M3 contains at least one of Ni, Mn, Fe, Mo, Cu or Ru; wherein M4 contains at least one of Ni, Fe, Cu or Ru; wherein 0 ≤ x ≤ 1.

[0024] As a preferred embodiment of the present invention, the positive electrode lithium supplementation additive D50 is in the range of 0.1 to 50 μm, and more preferably, the positive electrode lithium supplementation additive D50 is in the range of 3 to 15 μm.

[0025] This invention also provides a method for preparing a lithium-supplemented positive electrode sheet comprising the above-mentioned anti-gel lithium-supplemented positive electrode slurry, wherein the preparation method is as follows:

[0026] S1. Mix the polymer with the first molecular weight and the polymer with the second molecular weight with the solvent evenly to obtain a bimodal molecular weight distribution polymer positive electrode solution.

[0027] S2. Add the conductive agent to the bimodal molecular weight distribution polymer positive electrode solution obtained in S1 and mix evenly to obtain the conductive solution;

[0028] S3. Add the positive electrode active material to the conductive adhesive solution obtained in S2 in two or more portions, stir evenly, and obtain the positive electrode slurry;

[0029] S4. Add the positive electrode lithium supplementation additive to the positive electrode slurry obtained in S3, stir evenly, and then obtain the positive electrode lithium supplementation slurry;

[0030] S5. The positive lithium replenishment slurry obtained in S4 is coated, baked and dried to obtain a lithium replenishment positive electrode sheet;

[0031] The solid content of the bimodal molecular weight distribution polymer cathode solution is 6.0–10.0 wt%, preferably 7–8 wt%; the solid content of the cathode lithium replenishment slurry is 50–75 wt%, preferably 62–68%; the viscosity of the cathode lithium replenishment slurry is 1000–10000 mPa·s, preferably 3000–6000 mPa·s.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) This invention proposes a method for preparing an anti-gel lithium-supplementing cathode slurry and cathode sheet. It innovatively utilizes a cathode binder system with a bimodal molecular weight distribution. While ensuring high adhesion (contributed by the high molecular weight component), it reduces the overall slurry viscosity (contributed by the low molecular weight component), improving flow properties. Since the alkali source in the slurry originates from the slow release of the lithium-supplementing material, its distribution is uneven. Good flowability alleviates the problem of excessively high local alkali concentration, reduces the defluorination reaction kinetics, and thus reduces the degree of crosslinking. Simultaneously, the spatial distribution of high and low molecular weight molecules interpenetrates, reducing the probability of reactions between high molecular weight molecules, slowing the molecular weight growth rate of the crosslinking network, delaying the arrival of the gel point, and improving the uniformity of the lithium-supplementing slurry and the quality of the cathode sheet.

[0034] 2) The preparation method of this invention is simple to operate and fully compatible with existing electrode preparation processes. Furthermore, the binders used are all widely used positive electrode binders, ensuring high product safety and technological maturity.

[0035] 3) This invention aims to optimize the preparation of lithium-added positive electrode sheets. By utilizing a positive electrode binder system with a bimodal molecular weight distribution, the viscosity of the slurry is reduced while ensuring high adhesion, which greatly reduces the degree of defluorination reaction, alleviates the formation of cross-linked conjugated polyene, and improves the fluidity of the slurry and the quality of the electrode sheet. Detailed Implementation

[0036] To facilitate understanding of the technical means, creative features, objectives, and effects of this invention, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the scope of protection of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0037] Example 1

[0038] This embodiment provides a method for preparing a lithium-supplementing additive for a lithium-supplementing positive electrode sheet, wherein the mass ratio of the positive electrode active main material: bimodal molecular weight distribution positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium-supplementing material is 2:93.5:1:0.5:3.

[0039] Specifically, the steps include the following:

[0040] S1: Add 50g of the first PVDF binder with a weight average molecular weight of 1.2 million and 50g of the second PVDF binder with a weight average molecular weight of 300,000 to 1430g of N-methylpyrrolidone (NMP) and mix. Add the mixture to a dual-system stirring device, set the low-speed impeller to 30rpm / min and the high-speed impeller to 2000rpm / min, and stir and disperse for 6 hours to obtain the adhesive solution.

[0041] S2: Add 50g of the first conductive agent carbon black and 25kg of the second conductive agent carbon nanotubes to the adhesive solution and mix. Stir and disperse at 3000rpm / min for 1 hour to obtain the conductive adhesive.

[0042] S3: Add 2375g of positive electrode active material lithium iron phosphate positive electrode material to conductive adhesive and stir for 1 hour at a speed of 3000 rpm / min. After stirring once, add the remaining 2300g of positive electrode active material lithium iron phosphate, 150g of positive electrode lithium supplementation additive Li5FeO4 and 1500g of NMP. Stir under vacuum for 3 hours at a speed of 3000 rpm / min to obtain positive electrode lithium supplementation slurry.

[0043] S4: The positive electrode lithium replenishment slurry is coated on the surface of aluminum foil at a speed of 3m / min and dried at 110°C to obtain the lithium replenishment positive electrode sheet.

[0044] Example 2

[0045] The difference from Example 0 is that in S1, 65g of a first PVDF binder with a weight average molecular weight of 900,000 and 35g of a second PVDF binder with a weight average molecular weight of 300,000 are mixed in 1430g of N-methylpyrrolidone (NMP).

[0046] Everything else is the same as in Example 1.

[0047] Example 3

[0048] The difference from Example 1 is that in S1, 55g of a first PVDF binder with a weight average molecular weight of 900,000 and 45g of a second PVDF binder with a weight average molecular weight of 500,000 are mixed in 1430g of N-methylpyrrolidone (NMP).

[0049] Everything else is the same as in Example 1.

[0050] Example 4

[0051] The difference from Example 1 is that in S1, 55g of a first PVDF binder with a weight average molecular weight of 1.2 million and 45g of a second PVDF binder with a weight average molecular weight of 500,000 are mixed in 1430g of N-methylpyrrolidone (NMP).

[0052] Everything else is the same as in Example 1.

[0053] Example 5

[0054] The difference from Example 1 is that the mass ratio of positive electrode active material: high and low molecular weight positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium replenishment material is 2:94.5:1:0.5:2.

[0055] Everything else is the same as in Example 1.

[0056] Example 6

[0057] The difference from Example 1 is that the mass ratio of positive electrode active material: high and low molecular weight positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium supplementation material is 2:95:1:0.5:1.5.

[0058] Everything else is the same as in Example 1.

[0059] Example 7

[0060] The difference from Example 1 is that the mass ratio of positive electrode active material: high and low molecular weight positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium replenishment material is 2:95.5:1:0.5:1.

[0061] Everything else is the same as in Example 1.

[0062] Example 7

[0063] The difference from Example 2 is that the mass ratio of positive electrode active material: high and low molecular weight positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium replenishment material is 2:92.5:1:0.5:4.

[0064] Everything else is the same as in Example 2.

[0065] Example 8

[0066] The difference from Example 2 is that the mass ratio of positive electrode active material: high and low molecular weight positive electrode binder: first conductive agent: second conductive agent: positive electrode lithium replenishment material is 2:91.5:1:0.5:5.

[0067] Everything else is the same as in Example 2.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that in S1, 100g of conventional battery-grade PVDF (Sol 5130) and 1430g of NMP are mixed and stirred evenly to obtain a gel solution.

[0070] Everything else is the same as in Example 1.

[0071] Comparative Example 2

[0072] The difference from Comparative Example 1 is that in S1, 100g of conventional battery-grade PVDF (HSV900) and 1430g of NMP were mixed and stirred evenly to obtain a gel solution.

[0073] Everything else is the same as in Comparative Example 1.

[0074] Comparative Example 3

[0075] The difference from Comparative Example 1 is that in S1, 100g of conventional battery-grade PVDF (W9700) and 1430g of NMP were mixed and stirred evenly to obtain a gel solution.

[0076] Everything else is the same as in Comparative Example 1.

[0077] Performance testing:

[0078] Table 1: Slurry viscosity test and electrode peel strength test

[0079] project Discharge viscosity (mPa·s) 24-hour viscosity change rate (%) Peel force mN / mm Example 1 3163 76.05 18.12 Example 2 3304 63.10 18.49 Example 3 3316 61.16 20.51 Example 4 3882 40.06 19.91 Example 5 3825 77.81 18.72 Example 6 3405 63.85 17.41 Example 7 3230 98.89 20.16 Example 8 3326 73.78 19.49 Comparative Example 1 3250 314.25 8.58 Comparative Example 2 3016 419.10 5.62 Comparative Example 3 3044 253.92 10.64

[0080] Table 1 shows that the viscosity changes in Examples 1 to 8 were relatively stable, and the slurry retained fluidity after 24 hours without significant agglomeration. Comparative Examples 1 to 3, however, exhibited significant viscosity changes, with viscosity increases exceeding 253% after 24 hours, and lost fluidity, showing obvious agglomeration. Furthermore, the peel strength of the positive electrode sheets in the examples was greater than 18 mN / mm, which was higher than that in the comparative examples. Comparing the examples with the comparative examples, it is clear that the lithium-supplemented positive electrode slurry in the examples has better anti-gelling effects, resulting in a higher peel strength and better quality positive electrode sheets.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An anti-gelling lithium-supplementing cathode slurry, characterized in that, The anti-gel lithium-supplementing positive electrode slurry comprises a positive electrode active material, a conductive agent, a binder composition, and a lithium-supplementing additive. The mass ratio of the positive electrode active material, conductive agent, binder composition, and lithium-supplementing additive is 82.0–99.0: 0–4.0: 1.0–4.0: 0–10.

0. The binder composition is composed of a polymer with a first molecular weight and a polymer with a second molecular weight, wherein the first molecular weight is greater than the second molecular weight, and the mass ratio of the first molecular weight polymer to the second molecular weight polymer is 4–9.5: 6–0.

5. The polymer with the highest molecular weight is a homopolymer or copolymer of vinylidene fluoride, with a molecular weight of 800,000 to 1,400,000. The second molecular weight polymer is a homopolymer or copolymer of vinylidene fluoride, with a molecular weight of 300,000 to 600,000. The lithium supplement additive is selected from Li3N, LiN3, Li2O2, Li2O, LiF, Li2S2, Li2S, Li2CO3, Li2C2O4, Li2S2O3, Li2S2O4, Li2S2O5, Li2S2O6, Li2S4O6, Li2M1O2, Li2M2O3, Li5M3O4, or Li6Mn. x M 4(1-x) At least one of O4, wherein M1 contains at least one of Ni, Mn, Cu, Fe, Cr or Mo; wherein M2 contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr or Ru; wherein M3 contains at least one of Ni, Mn, Fe, Mo, Cu or Ru; wherein M4 contains at least one of Ni, Fe, Cu or Ru; wherein 0 ≤ x ≤ 1.

2. The anti-gel lithium-supplementing cathode slurry according to claim 1, characterized in that, The polymer crystallinity is ≤50%.

3. The anti-gel lithium-supplementing cathode slurry according to claim 2, characterized in that, The polymer raw materials include vinylidene fluoride monomer, initiator, dispersant, emulsifier, solvent, chain transfer agent, chain terminator, as well as modified monomers and additives. The polymerization process is either suspension polymerization or emulsion polymerization.

4. The anti-gel lithium-supplementing cathode slurry according to claim 1, characterized in that, The conductive agent is at least one of conductive carbon black, carbon fiber, carbon nanotubes, and graphene.

5. The anti-gel lithium-supplementing cathode slurry according to claim 1, characterized in that, The positive electrode active material is selected from any one or a combination of at least two of lithium iron phosphate, nickel cobalt manganese positive electrode materials, nickel cobalt aluminum positive electrode materials, cobalt-free positive electrode materials, or lithium iron manganese phosphate positive electrode materials.

6. The anti-gel lithium-supplementing cathode slurry according to claim 1, characterized in that, The positive electrode lithium supplement additive D50 is in the range of 0.1 to 50 μm.

7. A method for preparing a lithium-added positive electrode sheet, characterized in that, The preparation method of the anti-gel lithium-supplementing cathode slurry according to any one of claims 1-6 is as follows: S1. Mix the polymer with the first molecular weight and the polymer with the second molecular weight with the solvent evenly to obtain a bimodal molecular weight distribution polymer positive electrode solution. S2. Add the conductive agent to the bimodal molecular weight distribution polymer positive electrode solution obtained in S1 and mix evenly to obtain the conductive solution; S3. Add the positive electrode active material to the conductive adhesive solution obtained in S2 in two or more portions, stir evenly, and obtain the positive electrode slurry; S4. Add the positive electrode lithium supplementation additive to the positive electrode slurry obtained in S3, stir evenly, and then obtain the positive electrode lithium supplementation slurry; S5. The positive lithium replenishment slurry obtained in S4 is coated, baked and dried to obtain a lithium replenishment positive electrode sheet; The solid content of the bimodal molecular weight distribution polymer cathode solution is 6.0–10.0 wt%, the solid content of the cathode lithium replenishment slurry is 50–75 wt%, and the viscosity of the cathode lithium replenishment slurry is 1000–10000 mPa·s.