A negative electrode slurry, a negative electrode sheet, and a method for manufacturing the same

Abstract

The application discloses a kind of negative electrode slurry, negative electrode sheet and preparation method thereof, belong to negative electrode slurry technical field;The negative electrode slurry includes: negative electrode active material 84.5~99 parts, water 80~140 parts, dispersing agent 0.1~1.5 parts, conductive agent 0.1~4 parts, binder 0.1~4 parts, electrolyte reserve storehouse emulsion 0.01~4 parts, the high molecular particle of core-shell structure is contained in the electrolyte reserve storehouse emulsion, the inner core of high molecular particle is acrylate, butadiene and styrene copolymer, shell is the copolymer of acrylic acid and acrylonitrile.In the present application, electrolyte reserve storehouse emulsion is added in negative electrode slurry, the inner core of high molecular particle contained therein can effectively adsorb electrolyte, can play the role of liquid preservation;And shell has certain rigidity, avoid the volume expansion of inner core after adsorbing electrolyte and then affect the performance of negative electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of negative electrode slurry technology, specifically relating to a negative electrode slurry, a negative electrode sheet, and a method for preparing the same. Background Technology

[0002] During lithium-ion battery cycling, the electrolyte is consumed, weakening its ability to transfer lithium ions and ultimately reducing the battery's lifespan. To improve cycle life, various technologies have emerged, such as opening the battery seal for secondary electrolyte replenishment at the end of the cycle. However, this method is uncontrollable, making it difficult to accurately determine the optimal timing. Furthermore, since most batteries are already in the hands of customers, the feasibility and high operating costs limit its large-scale application. Therefore, there is an urgent need to develop more convenient and faster methods to increase electrolyte retention and thus improve battery cycle life. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a negative electrode slurry, a negative electrode sheet, and a method for preparing the same.

[0004] In a first aspect, the present invention provides a negative electrode slurry comprising 84.5-99 parts of a negative electrode active material, 80-140 parts of water, 0.1-1.5 parts of a dispersant, 0.1-4 parts of a conductive agent, 0.1-4 parts of a binder, and an electrolyte storage emulsion. The electrolyte storage emulsion contains solid materials, which include polymer particles with a core-shell structure. The core of the polymer particles is a copolymer of acrylate, butadiene, and styrene, and the outer shell is a copolymer of acrylic acid and acrylonitrile. The solid materials contained in the negative electrode slurry are 0.01-4 parts.

[0005] Secondly, the present invention provides a method for preparing a negative electrode slurry, comprising the following steps: The dispersant is dispersed in water to form mixture 1; then the active material and conductive agent are dispersed in mixture 1 to form mixture 2; then the binder is dispersed in mixture 2 to form mixture 3; the electrolyte storage emulsion is added to mixture 3 to obtain the negative electrode slurry.

[0006] Thirdly, the present invention provides a negative electrode sheet prepared using the aforementioned negative electrode slurry.

[0007] Fourthly, the present invention provides a method for preparing a negative electrode sheet, comprising the following steps: coating a negative electrode slurry into a sheet, drying it, and rolling it to a set thickness to obtain the sheet.

[0008] Fifthly, the present invention provides a lithium-ion battery, including the aforementioned negative electrode.

[0009] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: In this invention, an electrolyte storage emulsion is added to the negative electrode slurry. The core of the polymer particles contained therein can effectively adsorb the electrolyte and play a role in retaining the electrolyte. The outer shell has a certain rigidity to prevent the core from expanding in volume after adsorbing the electrolyte, thus affecting the performance of the negative electrode sheet.

[0010] The negative electrode sheet prepared by the negative electrode slurry of the present invention can improve the liquid retention, reduce battery polarization and impedance, and improve the cycle life of the battery. 。

[0011] The negative electrode sheet prepared by the negative electrode slurry in this invention can accelerate the wetting rate of the electrolyte and improve the electrochemical performance of the battery. Detailed Implementation

[0012] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0013] All molecular weights mentioned in this invention are number average molecular weights.

[0014] As mentioned above, in a first aspect, the present invention provides a negative electrode slurry, comprising, by mass fraction: The negative electrode active material comprises 84.5 to 99 parts, more preferably 90 to 99 parts, including but not limited to: 84.5 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, etc. The water content is 80-140 parts, more preferably 95-105 parts, including but not limited to: 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, etc. The dispersant is used in amounts of 0.1 to 1.5 parts, more preferably 0.4 to 1.2 parts, including but not limited to: 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1.0 parts, 1.3 parts, 1.5 parts, etc.; The conductive agent is 0.1 to 4 parts, more preferably 0.5 to 2 parts, including but not limited to: 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, etc.; The adhesive is 0.1 to 4 parts, more preferably 1.5 to 3.7 parts, including but not limited to: 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, etc.; The electrolyte storage emulsion contains solid materials, including core-shell polymer particles. The core of the polymer particles is a copolymer of acrylate, butadiene, and styrene, and the outer shell is a copolymer of acrylic acid and acrylonitrile. The negative electrode slurry contains 0.01 to 4 parts of solid materials, more preferably 0.1 to 1 part, including but not limited to: 0.01 parts, 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, 3.5 parts, 4.0 parts, etc.

[0015] In this invention, by introducing an electrolyte reservoir emulsion into the aqueous negative electrode slurry, a liquid retention function can be achieved, thereby improving the electrochemical performance of the negative electrode, reducing battery polarization and impedance, and increasing the battery's cycle life. 。

[0016] Preferably, the molecular weight of the copolymer of acrylate, butadiene and styrene is 5000~20000 Da, including but not limited to: 5000 Da, 7000 Da, 9000 Da, 10000 Da, 12000 Da, 14000 Da, 15000 Da, 17000 Da, 19000 Da, 20000 Da, etc.

[0017] When the molecular weight of the core is below 5000 Da, the polymer molecular chains are short and there is little inter-chain entanglement. This may prevent the formation of a stable three-dimensional network structure to "lock" in the electrolyte, resulting in poor electrolyte retention and thus limited improvement in the performance of the negative electrode.

[0018] Preferably, the molecular weight of the polymer particles is 20,000~100,000 Da, more preferably 40,000~60,000 Da, including but not limited to: 20,000 Da, 30,000 Da, 40,000 Da, 45,000 Da, 50,000 Da, 55,000 Da, 60,000 Da, 65,000 Da, 70,000 Da, 75,000 Da, 80,000 Da, 85,000 Da, 90,000 Da, 95,000 Da, 100,000 Da, etc.

[0019] In this invention, it is necessary to further control the molecular weight of the copolymer of acrylic acid and acrylonitrile in the outer shell. If the molecular weight is too low, the rigidity of the outer shell will be insufficient, which will not be able to effectively alleviate the volume expansion of the core, resulting in poor electrolyte retention. If the molecular weight is too high, the density of the outer shell layer will be too high, which will not be conducive to the electrolyte entering the core, and will also lead to poor electrolyte retention.

[0020] Preferably, the particle size of the polymer particles is 400~1000nm, including but not limited to: 400nm, 500nm, 700nm, 800nm, 900nm, and 1000nm.

[0021] Preferably, the solid content of the emulsion in the electrolyte storage tank is 10~20wt%, including but not limited to: 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, etc.

[0022] Preferably, the method for preparing the electrolyte storage emulsion includes the following steps: S1: After mixing the emulsifier, acrylate, butadiene, styrene and water evenly, stir and react to form a reaction solution containing solubilized micelles I; then add the initiator to carry out the polymerization reaction to obtain a reaction solution containing acrylate-butadiene-styrene core emulsion particles; S2: Add emulsifier, water, acrylic acid and acrylonitrile to the reaction solution containing acrylate-butadiene-styrene core latex particles and stir to obtain a reaction solution containing solubilizing micelles II; then add an initiator to carry out a polymerization reaction to obtain a reaction solution containing polymer particles; S3: Add a neutralizing agent to the reaction solution containing polymer particles, continue the reaction, cool down after the reaction is complete, filter, and the filtrate is the electrolyte storage emulsion.

[0023] The present invention uses emulsion polymerization to prepare an electrolyte storage emulsion containing core-shell structured polymer particles. The preparation process is relatively simple, and the core-shell structured polymer particles can be uniformly dispersed in the emulsion. The prepared emulsion can be directly added to the negative electrode slurry.

[0024] Preferably, in step S1, the acrylate is one or more selected from methyl acrylate, ethyl acrylate, butyl acrylate, phenyl acrylate, and octyl acrylate; the mass ratio of acrylate, butadiene, and styrene is (20~30):(5~10):(1~10), more preferably (20~30):(5~8):(3~7), including but not limited to: 20:6:7, 25:6:7, 30:6:7, 20: 10:7, 25:10:7, 30:10:7, 20:15:7, 25:15:7, 30:15:7, 20:6:10, 25:6:10, 30:6:10, 20:10:10, 25:10:10, 30:10:10, 20:15:10, 25:15:10, 30:15:10, 20:15:15, 25:15:15, 30:15:15, etc.

[0025] Preferably, in step S1, the mass ratio of the emulsifier, acrylate, and water is (0.1~2):(20~30):(60~80), more preferably (0.3~1):(20~30):(60~70), including but not limited to: 0.1:20:60, 0.5:20:60, 1.0:20:60, 2.0:20:60, 0.1:25:60, 0.5:25 :60, 1.0:25:60, 2.0:25:60, 0.1:30:65, 0.5:30:65, 1.0:30:65, 2.0:30:65, 0.1:30:70, 0.5:30:70, 1.0:35:70, 2.0:35:70, 0.1:30:80, 0.5:30:80, 1.0:30:80, 2.0:30:80.

[0026] Preferably, in step S1, the mass ratio of the initiator to the acrylate is (0.1~0.8):(10~30), more preferably (0.15~0.4):(10~30), including but not limited to: 0.1:10, 0.1:15, 0.1:20, 0.1:25, 0.1:30, 0.2:10, 0.2:15, 0.2:20, 0.2:25, 0.2:30, 0.3:10, 0.3:15, 0.3:20, 0.3:25, 0.3:30, 0.5:10, 0.5:15, 0.5:20, 0.5:25, 0.5:30, 0.8:10, 0.8:15, 0.8:20, 0.8:25, 0.8:30, etc.

[0027] Preferably, in step S1, the stirring reaction time is 30-50 min, including but not limited to: 30 min, 35 min, 40 min, 45 min, 50 min, etc.; the stirring reaction and polymerization reaction temperatures are each independently 70-90℃, including but not limited to: 70℃, 75℃, 80℃, 85℃, 90℃, etc.; the polymerization reaction time is 80-200 min, more preferably 120-150 min, including but not limited to: 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, etc.

[0028] Preferably, in step S2, the mass ratio of acrylic acid to acrylate in step S1 is (10~30):(20~30), more preferably (10~20):(20~30), including but not limited to: 10:20, 10:25, 10:30, 15:20, 15:25, 15:30, 20:20, 20:25, 20:30, 25:20, 25:25, 25:30, 30:20, 30:25, 30 The mass ratio of water, acrylic acid, and acrylonitrile is (60~80):(10~30):(20~40), more preferably (60~70):(10~20):(20~30), including but not limited to: 60:10:20, 65:10:20, 70:10:20, 75:10:20, 80:10:20, 60:15:20, 65:15:20, 70:15:20, 75:15:20, 8 0:15:20, 60:20:20, 65:20:20, 70:20:20, 75:20:20, 80:20:20, 60:25:20, 65:25:20, 70:25:20, 75:25:20, 80:25:20, 60:30:20, 65:30:20, 70:30:20, 75:30:20, 80:30:20, 60:30:25, 65:30:25, 7 0:30:25, 75:30:25, 80:30:25, 60:30:30, 65:30:30, 70:30:30, 75:30:30, 80:30:30, 60:30:35, 65:30:35, 70:30:35, 75:30:35, 80:30:35, 60:30:40, 65:30:40, 70:30:40, 75:30:40, 80:30:40, etc.

[0029] Preferably, in step S2, the mass ratio of the initiator to acrylic acid is (0.1~0.8):(10~30), more preferably (0.15~0.4):(10~20), including but not limited to: 0.1:10, 0.25:10, 0.4:10, 0.8:10, 0.1:20, 0.25:20, 0.4:20, 0.8:20, 0.1:25, 0.25:25, 0.4:25, 0.8:25, 0.1:30, 0.25:30, 0.4:30, 0.8:30, etc.

[0030] Preferably, in step S2, the stirring reaction time is 30-50 min, including but not limited to: 30 min, 35 min, 40 min, 45 min, 50 min, etc.; the stirring reaction and polymerization reaction temperatures are each independently 70-90℃, including but not limited to: 70℃, 75℃, 80℃, 85℃, 90℃, etc.; the polymerization reaction time is 80-240 min, more preferably 120-150 min, including but not limited to: 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, 210 min, 220 min, 230 min, 240 min, etc.

[0031] Preferably, in step S3, the neutralizing agent is one or both of sodium hydroxide and ammonia water; the mass ratio of the neutralizing agent to the acrylic acid in step S2 is (0.1~1.0):(10~30), including but not limited to: 0.1:10, 0.45:10, 0.6:10, 1.0:10, 0.1:15, 0.45:15, 0.6:15, 1.0:15, 0.1:20, 0.45:20, 0.6:20, 1.0:20, 0.1:30, 0.45:30, 0.6:30, 1.0:30, etc.

[0032] Preferably, in step S3, the reaction temperature continues at 70~90℃, including but not limited to: 70℃, 75℃, 80℃, 85℃, 90℃, etc.; the reaction time continues at 60~80min, including but not limited to: 60min, 65min, 70min, 75min, 80min, etc.; the temperature is then reduced to 35~40℃ for filtration.

[0033] Preferably, in steps S1 to S2, the emulsifier is one or more of rosin soap liquid, fatty acid soap, sodium dodecyl sulfate, and dodecylbenzene sulfonic acid; the initiator is potassium persulfate or ammonium persulfate.

[0034] Preferably, the negative electrode active material is one or more of artificial graphite, natural graphite, silicon carbide, and silicon suboxide.

[0035] Preferably, the dispersant is one or more of sodium carboxymethyl cellulose, polyacrylate, sodium polyacrylate, lithium polyacrylate, polyamide, and polyoxyethylene.

[0036] Preferably, the conductive agent is one or more of conductive carbon black, superconducting carbon black, Ketjen black, carbon nanotubes, graphene, and flake graphite.

[0037] Preferably, the adhesive is one or more of the following: polyacrylate, sodium polyacrylate, lithium polyacrylate, polyamide, polyoxyethylene, styrene-butadiene rubber latex, and polymethacrylate.

[0038] Secondly, the present invention provides a method for preparing a negative electrode slurry, comprising the following steps: The dispersant is dispersed in water to form mixture 1; then the active material and conductive agent are dispersed in mixture 1 to form mixture 2; then the binder is dispersed in mixture 2 to form mixture 3; the electrolyte storage emulsion is added to mixture 3 to obtain the negative electrode slurry.

[0039] Thirdly, the present invention provides a negative electrode sheet prepared using the aforementioned negative electrode slurry.

[0040] Fourthly, the present invention provides a method for preparing a negative electrode sheet, comprising the following steps: coating a negative electrode slurry into a sheet, drying it, and rolling it to a set thickness to obtain the sheet.

[0041] Fifthly, the present invention provides a lithium-ion battery, including the aforementioned negative electrode.

[0042] The present invention provides the following examples of preparing electrolyte storage emulsion.

[0043] Preparation Example 1: S1: Add 60g water, 0.3g rosin soap, 20g methyl acrylate, 5g butadiene, and 3g styrene to the reactor and heat to 80℃ and stir for 40min to obtain a reaction solution containing solubilized micelles I; then add 0.25g ammonium persulfate and carry out a polymerization reaction for 130min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing a methyl acrylate-butadiene-styrene copolymer core. The molecular weight of the methyl acrylate-butadiene-styrene copolymer core was measured to be approximately 10000Da.

[0044] S2: Add 60g of water, 10g of acrylic acid and 20g of acrylonitrile to the emulsion containing the core of methyl acrylate-butadiene-styrene copolymer and stir at 80℃ for 40min to obtain a reaction solution containing solubilizing micelles II; then add 0.25g of ammonium persulfate and carry out a polymerization reaction for 140min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0045] S3: At 80℃, 0.3g of ammonia (28wt%) was added to the emulsion containing polymer particles and the reaction continued for 70min. After the reaction was complete, the mixture was allowed to cool naturally to 40℃ and then filtered (to remove impurities from the emulsion; the filter cloth had a pore size of 3μm, so the polymer particles were not filtered out). The resulting filtrate was the electrolyte storage emulsion. Tests showed that the molecular weight of the polymer particles in the electrolyte storage emulsion was approximately 50,000Da, the average particle size was approximately 700nm, and the solid content of the electrolyte storage emulsion was approximately 15wt%.

[0046] Comparative Preparation Example 1 This method is basically the same as Example 1, except that step S2 is omitted. The specific method is as follows: S1: Add 60g water, 0.3g rosin soap, 20g methyl acrylate, 5g butadiene, and 3g styrene to the reactor, and heat to 80℃ and stir for 40min to obtain a reaction solution containing solubilized micelles I; then add 0.25g ammonium persulfate to it and carry out a polymerization reaction for 130min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing a methyl acrylate-butadiene-styrene copolymer core. The molecular weight of the methyl acrylate-butadiene-styrene copolymer core was measured to be approximately 10000Da.

[0047] S3: At 80℃, ammonia was added to the emulsion containing the methyl acrylate-butadiene-styrene copolymer core and the reaction continued for 70 minutes. After the reaction was complete, the temperature was naturally lowered to 40℃ for filtration (to remove impurities from the emulsion; the filter cloth pore size is 3μm, and the polymer particles will not be filtered out). The filtrate obtained was the electrolyte storage emulsion. According to the test, the molecular weight of the polymer particles in the electrolyte storage emulsion was about 10000Da, the average particle size of the polymer particles was about 300nm, and the solid content of the electrolyte storage emulsion was about 14wt%.

[0048] Comparative Preparation Example 2 This method is basically the same as Example 1, except that step S1 is omitted. The specific method is as follows: S2: 60g water, 10g acrylic acid and 20g acrylonitrile were stirred at 80℃ for 40min to obtain a reaction solution containing solubilized micelles II; then 0.25g ammonium persulfate was added to it and a polymerization reaction was carried out for 140min (the reaction temperature was maintained at 80℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0049] S3: At 80℃, 0.3g of ammonia (28wt%) was added to the emulsion containing polymer particles and the reaction continued for 70min. After the reaction was complete, the mixture was allowed to cool naturally to 40℃ and then filtered (to remove impurities from the emulsion; the filter cloth had a pore size of 3μm, so the polymer particles were not filtered out). The filtrate obtained was the electrolyte storage emulsion. According to the test, the molecular weight of the polymer particles in the electrolyte storage emulsion was approximately 39000Da, the average particle size was approximately 400nm, and the solid content of the electrolyte storage emulsion was approximately 16wt%.

[0050] Preparation Example 2 The preparation method is basically the same as in Example 1, except that in step S1, the amount of ammonium persulfate added is 0.4 g; step S1 is as follows: S1: Add 60g water, 0.3g rosin soap, 20g methyl acrylate, 5g butadiene, and 3g styrene to the reactor and heat to 80℃ and stir for 40min to obtain a reaction solution containing solubilized micelles I; then add 0.4g ammonium persulfate and carry out a polymerization reaction for 80min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing a methyl acrylate-butadiene-styrene copolymer core. The molecular weight of the methyl acrylate-butadiene-styrene copolymer core was measured to be approximately 5500Da.

[0051] In step S3, the molecular weight of the polymer particles in the emulsion in the electrolyte storage tank is approximately 45,000 Da. The average particle size of the polymer particles is about 500 nm, and the solid content of the electrolyte storage emulsion is about 15 wt%.

[0052] Preparation Example 3 The preparation method is basically the same as in Example 1, except that in step S1, the amount of ammonium persulfate added is 0.05 g. Step S1 is as follows: S1: Add 60g water, 0.3g rosin soap, 20g methyl acrylate, 5g butadiene, and 3g styrene to the reactor and heat to 80℃ and stir for 40min to obtain a reaction solution containing solubilized micelles I; then add 0.05g ammonium persulfate and carry out a polymerization reaction for 200min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing a methyl acrylate-butadiene-styrene copolymer core. The molecular weight of the methyl acrylate-butadiene-styrene copolymer core was measured to be approximately 18000Da.

[0053] In step S3, the molecular weight of the polymer particles in the emulsion in the electrolyte storage tank is approximately 69,000 Da. The average particle size of the polymer particles is about 900 nm, and the solid content of the electrolyte storage emulsion is about 15 wt%.

[0054] Preparation Example 4 The preparation method is basically the same as in Example 1, except that in step S2, the amount of ammonium persulfate added is 0.8 g. Step S2 is as follows: S2: Add 60g of water, 10g of acrylic acid and 20g of acrylonitrile to the emulsion containing the core of methyl acrylate-butadiene-styrene copolymer and stir at 80℃ for 40min to obtain a reaction solution containing solubilizing micelles II; then add 0.8g of ammonium persulfate to it and carry out a polymerization reaction for 80min (maintain the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0055] In step S3, the molecular weight of the polymer particles in the prepared electrolyte storage emulsion is about 20,000 Da, the average particle size of the polymer particles is about 550 nm, and the solid content of the electrolyte storage emulsion is about 15 wt%.

[0056] Preparation Example 5 The preparation method is basically the same as in Example 1, except that in step S2, the amount of ammonium persulfate added is 0.03 g. Step S2 is as follows: S2: Add 60g of water, 10g of acrylic acid and 20g of acrylonitrile to the emulsion containing the core of methyl acrylate-butadiene-styrene copolymer and stir at 80℃ for 40min to obtain a reaction solution containing solubilizing micelles II; then add 0.03g of ammonium persulfate and carry out a polymerization reaction for 240min (maintaining the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0057] In step S3, the molecular weight of the polymer particles in the prepared electrolyte storage emulsion is approximately 11,000 Da; the average particle size of the polymer particles is approximately 1,000 nm; and the solid content of the electrolyte storage emulsion is approximately 15 wt%.

[0058] Preparation Example 6 S1: Add 70g water, 1g sodium dodecyl sulfate, 25g butyl acrylate, 6g butadiene, and 10g styrene to the reactor, and heat to 90℃ and stir for 30min to obtain a reaction solution containing solubilized micelles I; then add 0.15g potassium persulfate to it and carry out a polymerization reaction for 150min (maintain the reaction temperature at 80℃ during the polymerization reaction) to obtain an emulsion containing a butyl acrylate-butadiene-styrene copolymer core. The molecular weight of the butyl acrylate-butadiene-styrene copolymer core was measured to be approximately 12000Da.

[0059] S2: Add 65g of water, 15g of acrylic acid and 30g of acrylonitrile to the emulsion containing the core of butyl acrylate-butadiene-styrene copolymer and stir at 90℃ for 30min to obtain a reaction solution containing solubilizing micelles II; then add 0.15g of potassium persulfate and carry out a polymerization reaction for 150min (maintaining the reaction temperature at 90℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0060] S3: At 90℃, 0.5g of ammonia (28wt%) was added to the emulsion containing polymer particles and the reaction continued for 60min. After the reaction was complete, the mixture was allowed to cool naturally to 40℃ and then filtered (to remove impurities from the emulsion; the filter cloth had a pore size of 3μm, so the polymer particles were not filtered out). The resulting filtrate was the electrolyte storage emulsion. Tests showed that the molecular weight of the polymer particles in the electrolyte storage emulsion was approximately 57000Da, the average particle size was approximately 900nm, and the solid content of the electrolyte storage emulsion was approximately 19wt%.

[0061] Preparation Example 7 S1: Add 70g water, 1.0g fatty acid soap, 30g ethyl acrylate, 8g butadiene, and 7g styrene to the reactor, and heat to 70℃ and stir for 50min to obtain a reaction solution containing solubilized micelles I; then add 0.4g potassium persulfate to it and carry out a polymerization reaction for 120min (maintaining the reaction temperature at 70℃ during the polymerization reaction) to obtain an emulsion containing a butyl acrylate-butadiene-styrene copolymer core. The molecular weight of the butyl acrylate-butadiene-styrene copolymer core was measured to be approximately 8000Da.

[0062] S2: Add 70g of water, 20g of acrylic acid and 30g of acrylonitrile to the emulsion containing the core of butyl acrylate-butadiene-styrene copolymer and stir at 70℃ for 50min to obtain a reaction solution containing solubilizing micelles II; then add 0.4g of potassium persulfate and carry out a polymerization reaction for 120min (maintaining the reaction temperature at 70℃ during the polymerization reaction) to obtain an emulsion containing polymer particles.

[0063] S3: At 70℃, 1g of ammonia (28wt%) was added to the emulsion containing polymer particles and the reaction continued for 80min. After the reaction was complete, the mixture was allowed to cool naturally to 40℃ and then filtered (to remove impurities from the emulsion; the filter cloth had a pore size of 3μm, so the polymer particles were not filtered out). The filtrate obtained was the electrolyte storage emulsion. According to the test, the molecular weight of the polymer particles in the electrolyte storage emulsion was about 40000Da, the average particle size of the polymer particles was about 600nm, and the solid content of the electrolyte storage emulsion was about 12wt%.

[0064] Example 1 In this embodiment, the composition of the negative electrode slurry is as follows: 6g sodium carboxymethyl cellulose, 1000g deionized water, 8g conductive agent SP, 969g artificial graphite, 37.5g styrene-butadiene rubber latex (solid content 40wt%), and 13.33g electrolyte storage tank latex (prepared in Preparation Example 1, solid content 15wt%) (the amount of solid material added is 2g).

[0065] The specific preparation method is as follows: Sodium carboxymethyl cellulose is added to deionized water and dissolved completely to form mixture 1; conductive agent SP and artificial graphite are added to mixture 1 and stirred thoroughly to form mixture 2; styrene-butadiene rubber latex is added to mixture 2 and stirred thoroughly to form mixture 3; 13.33g of electrolyte storage emulsion is added to mixture 3 and stirred thoroughly to form negative electrode slurry.

[0066] The negative electrode sheet is prepared as follows: after coating the negative electrode slurry into a sheet, it is dried and then rolled to a thickness of 117μm; thus, the negative electrode sheet is obtained.

[0067] Comparative Example 1 It is basically the same as Example 1, except that the electrolyte storage emulsion is not added.

[0068] Comparative Example 2 The process is basically the same as in Example 1, except that the electrolyte storage emulsion was prepared in Comparative Preparation Example 1, in which the solid content of the electrolyte storage emulsion was 14 wt% and the amount added was 14.28 g (the amount of solid material added was 2 g).

[0069] Comparative Example 3 This is essentially the same as Example 1, except that the electrolyte storage emulsion was prepared in Comparative Preparation Example 2. In Comparative Preparation Example 2, the solid content of the electrolyte storage emulsion was 16 wt%, and the amount added was 12.5 g (the amount of solid material added was 2 g).

[0070] Example 2 It is basically the same as Example 1, except that the electrolyte storage emulsion was prepared in Preparation Example 2.

[0071] Example 3 The process is basically the same as in Example 1, except that the electrolyte storage emulsion was prepared in Preparation Example 3.

[0072] Example 4 The process is basically the same as in Example 1, except that the electrolyte storage emulsion was prepared in Example 4.

[0073] Example 5 The process is basically the same as in Example 1, except that the electrolyte storage emulsion was prepared in Preparation Example 5.

[0074] Example 6 It is basically the same as Example 1, except that: the amount of emulsion added to the electrolyte storage tank is 66.66g (the amount of solid material added is 10g).

[0075] Example 7 It is basically the same as Example 1, except that: the amount of emulsion added to the electrolyte storage tank is 6.66g (the amount of solid material added is 1g).

[0076] Example 8 In this embodiment, the composition of the negative electrode slurry is as follows: 12g of polyacrylate, 950g of deionized water, 5g of Ketjen black, 900g of natural graphite, 15.1g of polymethyl methacrylate, and 36.84g of electrolyte storage emulsion (prepared in Preparation Example 6, with a solid content of 19wt%) (7g of solid material).

[0077] The specific preparation method is as follows: polyacrylate is added to deionized water and dissolved completely to form mixture 1; Ketjen black and natural graphite are added to mixture 1 and stirred thoroughly to form mixture 2; polymethyl methacrylate is added to mixture 2 and stirred thoroughly to form mixture 3; electrolyte storage emulsion is added to mixture 3 and stirred thoroughly to form negative electrode slurry.

[0078] The negative electrode sheet is prepared as follows: after coating the negative electrode slurry into a sheet, it is dried and then rolled to a thickness of 117μm; thus, the negative electrode sheet is obtained.

[0079] Example 9 In this embodiment, the composition of the negative electrode slurry is as follows: 4g of sodium polyacrylate, 1050g of deionized water, 20g of superconducting carbon black, 1000g of silicon carbide, 30g of polymethyl methacrylate, and 25g of electrolyte storage emulsion (prepared in Preparation Example 7, with a solid content of 12wt%) (3g of solid material).

[0080] The specific preparation method is as follows: Sodium polyacrylate is added to deionized water and dissolved completely to form mixture 1; superconducting carbon black and silicon carbide are added to mixture 1 and stirred thoroughly to form mixture 2; polymethyl methacrylate is added to mixture 2 and stirred thoroughly to form mixture 3; electrolyte storage emulsion is added to mixture 3 and stirred thoroughly to form negative electrode slurry.

[0081] The negative electrode sheet is prepared as follows: after coating the negative electrode slurry into a sheet, it is dried and then rolled to a thickness of 117μm; thus, the negative electrode sheet is obtained.

[0082] The negative electrode sheets prepared in Examples 1-9 and Comparative Examples 1-3 were slit and then wound together with the positive electrode sheet (the positive electrode active material was a 6-series ternary material) and a separator to form a battery cell. The battery cell was then encapsulated with an electrolyte (1 mol / L LiPF6; solvent composition: EMC:DEC:DMC volume ratio of 1:1:1, with an additional 1% (volume) EC) to obtain the battery. Performance tests were performed on the negative electrode sheets and the assembled battery; the test results are shown in Tables 1-4.

[0083] The liquid absorption rate of the negative electrode sheet, the wetting time of the cell, and the liquid retention coefficient were tested, and the results are shown in Table 1.

[0084] Table 1 As can be seen from the data in Table 1, the negative electrode sheet prepared with the negative electrode slurry in Example 1 has a high liquid absorption rate and a high cell liquid retention coefficient, and the cell wetting time is short. In Comparative Example 1, the negative electrode slurry does not contain an electrolyte reservoir emulsion, resulting in a significant decrease in the liquid absorption rate and cell liquid retention coefficient of the prepared negative electrode sheet compared to Example 1, and a longer cell wetting time. The electrolyte reservoir emulsion in Comparative Example 2 lacks a shell structure, and the negative electrode sheet prepared accordingly shows a slight increase in liquid absorption rate and liquid retention coefficient compared to Comparative Example 1, but the increase is very small. The electrolyte reservoir emulsion in Comparative Example 3 lacks a core structure, and the negative electrode sheet prepared accordingly shows a slight increase in liquid absorption rate compared to Comparative Example 1, but the liquid retention coefficient remains largely unchanged. Compared to Example 1, Examples 2 and 3 adjusted the molecular weight of the core of the polymer particles in the electrolyte storage emulsion. In Example 2, the core molecular weight was reduced, the molecular chains were shorter, and there was less interchain entanglement, which may prevent the formation of a stable three-dimensional network structure to "lock" in the electrolyte, resulting in a decrease in the liquid absorption rate and liquid retention coefficient compared to Example 1. In Example 3, the core molecular weight was further increased, and the liquid absorption rate and liquid retention coefficient of the core were further improved compared to Example 1. Compared to Example 1, Examples 4 and 5 adjusted the molecular weight of the outer shell of the polymer particles in the electrolyte storage emulsion. In Example 4, the outer shell molecular weight was reduced, possibly because the shell layer was not rigid enough. After the core absorbed the electrolyte and expanded, the shell layer may crack or break, resulting in a decrease in the liquid absorption rate and liquid retention coefficient compared to Example 1. In Example 5, the outer shell molecular weight was increased, and the liquid absorption rate and liquid retention coefficient were reduced compared to Example 1, possibly because the outer shell layer was too dense, which was not conducive to the electrolyte entering the core and also led to a poorer liquid retention effect. Compared to Example 1, Examples 6 and 7 mainly involved adjusting the amount of emulsion added to the electrolyte storage tank. In Example 6, as the amount of emulsion added to the electrolyte storage tank increased, the liquid absorption rate and liquid retention coefficient slightly improved, but the improvement was not significant. In Example 7, the decrease in the amount added resulted in a slight decrease in the liquid absorption rate of the electrode and the liquid retention coefficient of the cell. In Examples 8 and 9, the preparation process parameters of the negative electrode were adjusted, and the performance of the corresponding negative electrode may fluctuate to some extent, but the overall performance remains good.

[0085] The internal resistance and DC impedance of the battery were tested, and the results are shown in Table 2.

[0086] Table 2 As can be seen from the data in Table 2, the battery assembled from the negative electrode sheet prepared with the negative electrode slurry in Example 1 has lower internal resistance and DC internal resistance. In Comparative Example 1, the negative electrode slurry without an electrolyte reservoir emulsion shows a significant increase in both internal resistance and DC internal resistance compared to Example 1. In Comparative Example 2, the electrolyte reservoir emulsion lacks a shell structure, resulting in a slight increase in both internal resistance and DC internal resistance compared to Comparative Example 1, but the increase is not significant. This may be because a single core cannot effectively store the electrolyte, leading to electrode instability and increased internal resistance and DC internal resistance. In Comparative Example 3, the electrolyte reservoir emulsion lacks a core structure, resulting in a slight increase in both internal resistance and DC internal resistance compared to Comparative Example 1, but the increase is not significant. This may be because a single outer shell for electrolyte storage affects the electrode performance. Compared to Example 1, Examples 2 and 3 adjusted the molecular weight of the core of the polymer particles in the electrolyte storage emulsion. The decrease in core molecular weight in Example 2 may be due to a reduction in liquid retention and the liquid retention coefficient, resulting in an increase in battery internal resistance and DC internal resistance compared to Example 1. The further increase in core molecular weight in Example 3 may also be due to a decrease in core molecular weight, leading to an increase in liquid retention and the liquid retention coefficient, resulting in a further decrease in battery internal resistance and DC internal resistance compared to Example 1. Compared to Example 1, Examples 4 and 5 adjusted the molecular weight of the outer shell of the polymer particles in the electrolyte storage emulsion. The decrease in outer shell molecular weight in Example 4 may be due to insufficient shell strength, making the polymer particles prone to breakage, reducing liquid retention and the liquid retention coefficient, thus increasing battery internal resistance and DC internal resistance compared to Example 1. The further increase in outer shell molecular weight in Example 5, resulting in a further increase in battery internal resistance and DC internal resistance compared to Example 1, may be due to a decrease in liquid retention, leading to a certain increase in internal resistance. Compared to Example 1, Examples 6 and 7 mainly involved adjusting the amount of emulsion added to the electrolyte storage tank. In Example 6, the increased amount of emulsion slightly reduced the battery internal resistance and DC internal resistance compared to Example 1, but the reduction was not significant. In Example 7, the decreased amount of emulsion increased the battery internal resistance and DC internal resistance to a certain extent compared to Example 1. In Examples 8 and 9, the process parameters for preparing the negative electrode sheet were adjusted, resulting in some fluctuation in the battery internal resistance and DC internal resistance of the prepared batteries, but overall, they maintained good performance.

[0087] The battery cycle life was tested, and the results are shown in Table 3.

[0088] Table 3 As can be seen from the data in Table 3, the negative electrode sheet prepared by the negative electrode slurry in Example 1 has a longer cycle life at both 0.5C and 1C rates. In Comparative Example 1, the negative electrode slurry does not contain an electrolyte reservoir emulsion, and the cycle life of the corresponding battery is significantly lower than that of Example 1. The electrolyte reservoir emulsion in Comparative Example 2 does not have a shell structure, and the cycle life of the corresponding battery is slightly improved compared to Comparative Example 1, but the improvement is not significant. The electrolyte reservoir emulsion in Comparative Example 3 does not have a core structure, and the cycle life of the corresponding battery is slightly improved compared to Comparative Example 1, but the improvement is not significant. In Examples 2 and 3, the molecular weight of the polymer particles in the electrolyte reservoir emulsion was adjusted compared to Example 1. In Example 2, the decrease in core molecular weight resulted in a lower cycle life compared to Example 1; in Example 3, the increase in core molecular weight further improved the cycle life compared to Example 1. Compared to Example 1, Examples 4 and 5 adjusted the molecular weight of the polymer particles in the electrolyte reservoir emulsion. In Example 4, the molecular weight of the shell decreased, resulting in a lower cycle life compared to Example 1. In Example 5, the molecular weight of the shell increased to a certain extent, possibly due to excessive shell density leading to insufficient overall electrolyte retention, resulting in a significantly lower cycle life compared to Example 1. Examples 6 and 7, compared to Example 1, mainly adjusted the amount of electrolyte reservoir emulsion added. In Example 6, the increased amount added increased the cycle life compared to Example 1; in Example 7, the decreased amount added slightly reduced the cycle life compared to Example 1. In Examples 8 and 9, the preparation process parameters of the negative electrode sheet were adjusted, resulting in some fluctuation in the cycle life of the prepared batteries, but overall, they maintained good performance.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A negative electrode slurry, characterized in that, The negative electrode slurry comprises: 84.5-99 parts of negative electrode active material, 80-140 parts of water, 0.1-1.5 parts of dispersant, 0.1-4 parts of conductive agent, 0.1-4 parts of binder, and an electrolyte storage emulsion. The electrolyte storage emulsion contains solid materials, including core-shell polymer particles. The core of the polymer particles is a copolymer of acrylate, butadiene, and styrene, and the outer shell is a copolymer of acrylic acid and acrylonitrile. The amount of solid materials in the negative electrode slurry is 0.01-4 parts. The molecular weight of the copolymer of acrylate, butadiene and styrene is 5000~20000 Da; The molecular weight of the polymer particles is 20,000 to 100,000 Da.

2. The negative electrode slurry according to claim 1, characterized in that, The particle size of the polymer particles is 400~1000nm; And / or: The solid content of the emulsion in the electrolyte storage tank is 10~20wt%.

3. The negative electrode slurry according to claim 1 or 2, characterized in that, The method for preparing the electrolyte storage emulsion includes the following steps: S1: After the emulsifier, acrylate, butadiene, styrene and water are mixed evenly, the mixture is stirred and reacted to form a reaction solution containing solubilized micelles I; then the initiator is added to carry out the polymerization reaction to obtain a reaction solution containing acrylate-butadiene-styrene core emulsion particles. S2: Add emulsifier, water, acrylic acid and acrylonitrile to the reaction solution containing acrylate-butadiene-styrene core emulsion particles and stir to obtain a reaction solution containing solubilizing micelles II; then add an initiator to carry out a polymerization reaction to obtain a reaction solution containing polymer particles; S3: Add a neutralizing agent to the reaction solution containing polymer particles, continue the reaction, cool down after the reaction is complete, filter, and the filtrate is the electrolyte storage emulsion.

4. The negative electrode slurry according to claim 3, characterized in that, In step S1, the acrylate is one or more of methyl acrylate, ethyl acrylate, butyl acrylate, phenyl acrylate, and octyl acrylate; the mass ratio of acrylate, butadiene, and styrene is (20~30):(5~10):(1~10); And / or: The mass ratio of the emulsifier, acrylate, and water is (0.1~2):(20~30):(60~80); And / or: The mass ratio of the initiator to the acrylate is (0.1~0.8):(20~30).

5. The negative electrode slurry according to claim 3, characterized in that, In step S2, the mass ratio of acrylic acid to acrylate in step S1 is (10~30):(20~30); the mass ratio of water, acrylic acid and acrylonitrile is (60~80):(10~30):(20~40). And / or: The mass ratio of the initiator to acrylic acid is (0.1~0.8):(10~30).

6. The negative electrode slurry according to claim 3, characterized in that, In step S3, the neutralizing agent is one or both of sodium hydroxide and ammonia water; the mass ratio of the neutralizing agent to the acrylic acid in step S2 is (0.1~1.0):(10~30).

7. The negative electrode slurry according to claim 1 or 2, characterized in that, The negative electrode active material is one or more of artificial graphite, natural graphite, silicon carbide, and silicon suboxide. And / or: The dispersant is one or more of sodium carboxymethyl cellulose, polyacrylate, sodium polyacrylate, lithium polyacrylate, polyamide, and polyoxyethylene. And / or: The conductive agent is one or more of the following: conductive carbon black, superconducting carbon black, Ketjen black, carbon nanotubes, graphene, and flake graphite. And / or: The adhesive is one or more of the following: polyacrylate, sodium polyacrylate, lithium polyacrylate, polyamide, polyoxyethylene, styrene-butadiene rubber latex, and polymethacrylate.

8. A method for preparing negative electrode slurry according to any one of claims 1 to 7, comprising the following steps: dispersing a dispersant in water to form mixture 1; then dispersing an active material and a conductive agent in mixture 1 to form mixture 2; then dispersing a binder in mixture 2 to form mixture 3; and adding an electrolyte storage emulsion to mixture 3 to obtain negative electrode slurry.

9. A negative electrode sheet, characterized in that, It is prepared using the negative electrode slurry described in any one of claims 1 to 7.

10. A lithium-ion battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

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