Battery negative electrode slurry, negative electrode sheet and its preparation method and battery

Abstract

This application discloses a battery negative electrode slurry, a negative electrode sheet, a method for preparing the same, and a battery. The negative electrode slurry comprises a negative electrode active material, a conductive agent, a binder, a solvent, and a surfactant. The surfactant is composed of nonionic and anionic surfactants, with a weight percentage of 5%–15% and 85%–95%, respectively. The surfactant accounts for 0.01–2 wt% of the battery negative electrode slurry. This application adds a specific proportion of mixed surfactants to the slurry to improve the slurry's leveling properties, viscosity, and thixotropy during electrode coating, resulting in better dispersibility and leveling properties during electrode coating. This controls edge thickness, improving electrode thickness uniformity and achieving edge thinning. This method is low-cost, simple to operate, and requires no further edge treatment, avoiding damage to the electrode from edge residues and improving battery consistency and stability.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery negative electrode slurry, a negative electrode sheet, a method for preparing the same, and a battery. Background Technology

[0002] During the charge-discharge cycle of lithium batteries, the active material at the electrode edges experiences significant stress, which can reduce battery capacity and lifespan. To mitigate this issue, it is typically necessary to thin the edges of the active coating to minimize the negative impact of edge stress on battery performance. External thinning primarily involves cutting, grinding, or compressing during the coating process to reduce the thickness of the active coating. While simple and easy to implement, this method may leave residues at the edges of the active coating, reducing its uniformity and consistency, thus affecting overall battery performance. Another approach is to use chemical agents to thin the active coating. This method involves chemically etching the material at the battery coating edges using spraying or immersion to achieve thinning. Chemical thinning allows for more precise control, but requires careful control of the agent concentration and etching time to avoid serious damage to the battery. Therefore, researching a method that achieves good thinning results without damaging the electrodes is crucial. Summary of the Invention

[0003] The main objective of this application is to provide a battery negative electrode slurry, a negative electrode sheet, a method for preparing the same, and a battery, in order to solve the problems in the prior art where the effect of thinning the edge thickness of the active coating of the battery electrode sheet is limited, the operation method is difficult, and the electrode sheet is easily damaged.

[0004] To achieve the above objectives, according to one aspect of this application, a battery negative electrode slurry is provided: comprising a negative electrode active material, a conductive agent, a binder, a surfactant, and a solvent; wherein the surfactant is composed of a nonionic surfactant and anionic surfactant, the nonionic surfactant accounting for 5% to 15% by weight of the surfactant; the anionic surfactant accounting for 85% to 95% by weight of the surfactant; and the surfactant accounting for 0.01 to 2 wt% by weight of the battery negative electrode slurry.

[0005] Furthermore, nonionic surfactants account for 8% to 15% of the total surfactant weight, while anionic surfactants account for 85% to 92% of the total surfactant weight.

[0006] Furthermore, the surfactant accounts for 0.05–1.5 wt% of the weight of the battery negative electrode slurry; further, 0.05–1 wt%; further, 0.08–0.5 wt%; and even further, 0.08–0.2 wt%.

[0007] Furthermore, the nonionic surfactant is selected from at least one of ethylhexanol polyoxypropylene polyoxyethylene ether, nonylphenol polyoxyethylene ether, polyoxyethylene polyoxypropylene hexadecyl ether, polyoxyethylene hexadecyl ether, and polyoxypropylene hexadecyl ether.

[0008] Furthermore, the anionic surfactant is selected from one or more of the following: disodium dodecyl polyoxyethylene ether sulfosuccinate, sodium dioctyl succinate sulfonate, sodium dodecylbenzene sulfonate, ammonium dodecyl polyoxyethylene ether sulfate, and ammonium dodecyl polyacrylate.

[0009] Furthermore, the surfactant is composed of disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether.

[0010] Furthermore, the viscosity of the battery negative electrode slurry is 3500–4500 mPa·S;

[0011] Furthermore, the solid content of the battery negative electrode slurry is 60% to 70%.

[0012] Furthermore, the weight ratio of the negative electrode active material, conductive agent, binder, and surfactant is (90-95):(1.5-6):(1-3):(0.01-2).

[0013] Furthermore, the negative electrode active material is selected from natural graphite.

[0014] Furthermore, the conductive agent is selected from conductive carbon black.

[0015] Furthermore, the adhesive is selected from polyacrylic acid.

[0016] Furthermore, the solvent is selected from deionized water.

[0017] According to a second aspect of this application, a method for preparing the above-mentioned battery negative electrode slurry is provided, comprising the following steps: mixing raw materials of negative electrode active material, conductive agent, binder, solvent and surfactant according to the proportion of each raw material, stirring, and obtaining battery negative electrode slurry.

[0018] Furthermore, the preparation method specifically includes the following steps:

[0019] Step S1: Mix the adhesive and solvent to form an adhesive solution; mix the conductive agent and solvent to form a conductive liquid; mix the surfactant and solvent to form a surfactant solution;

[0020] Step S2: Add the negative electrode active material to the adhesive and conductive liquid, add solvent for the first viscosity adjustment, add surfactant solution, add solvent for the second viscosity adjustment until the viscosity of the slurry reaches the preset viscosity;

[0021] Furthermore, the mass concentration of the adhesive solution is 8% to 20%.

[0022] Furthermore, the mass concentration of the conductive liquid is 10% to 12%.

[0023] Furthermore, the mass concentration of the surfactant solution is 0.8% to 1.5%.

[0024] Furthermore, the preset viscosity is 4000–5000 mPa·s.

[0025] According to a third aspect of this application, a battery negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active coating attached to the surface of the negative electrode current collector; the slurry for preparing the negative electrode active coating is the aforementioned battery negative electrode slurry.

[0026] According to a fourth aspect of this application, a battery is provided, including a negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet of the aforementioned battery.

[0027] This application provides a battery negative electrode slurry. By introducing a certain proportion of composite surfactant into the main slurry, the surfactant can interact with the active materials, binders, and conductive agents in the slurry. This optimizes the viscosity, flowability, and thixotropy of the slurry during coating on the electrode, and also adjusts the surface tension of the slurry, ensuring good dispersion uniformity and flowability during coating. This effectively reduces the edge thickness of the active coating on the electrode. This method not only improves the uniformity of the active coating thickness but also effectively eliminates the thick edge phenomenon. Furthermore, this technology has low production costs, is simple to operate, and easy to control. It eliminates the need for other complex edge treatments, avoiding the impact of edge residues on battery performance, thereby improving the consistency and stability of the battery. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is a side view of the active coating thickness in different regions of the positive electrode sheet in an embodiment of this application.

[0030] Figure label:

[0031] 1. Current collector; 2. Coating thickness in the thinned area on one side; 3. Coating thickness in the normal area on one side. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] As mentioned in the background technology, the active coating of the electrode has a thick edge phenomenon. The thickness of the active coating of the electrode is usually reduced by cutting, grinding or compression. This method will leave residues at the edge of the electrode. Another method is to use chemical etching to etch the edge. This method requires precise control of the amount of chemical and the etching time, and the operation is not easy to control, which can easily damage the electrode.

[0034] According to one aspect of this application, a battery negative electrode slurry is provided, comprising a negative electrode active material, a conductive agent, a binder, a surfactant, and a solvent; wherein the surfactant is composed of a nonionic surfactant and anionic surfactant, the nonionic surfactant accounting for 5% to 15% of the total surfactant by weight; the anionic surfactant accounting for 85% to 95% of the total surfactant by weight; and the surfactant accounting for 0.01 to 2 wt% of the total surfactant in the battery negative electrode slurry.

[0035] The anionic surfactant used in this application has several polar functional groups embedded in its molecular structure. These functional groups can stabilize the solid particles suspended in the slurry by adsorbing them, thereby giving the slurry excellent dispersion and flow properties. In addition, this surfactant can effectively reduce the surface tension of the slurry and optimize the uniformity of the edge thickness of the active coating.

[0036] The nonionic surfactant selected in this application exhibits nonionic properties in aqueous media, possesses excellent stability, and demonstrates good solubility in water and organic solvents. This surfactant can be applied to both aqueous and oil-based slurry systems, effectively promoting the uniform distribution of active materials in different media, thereby imparting superior rheological properties to the dispersion system; this characteristic helps improve the uniformity of the edge thickness of the active coating on battery electrodes.

[0037] The novel slurry developed in this application incorporates a special mixture of nonionic and anionic surfactants. By fully utilizing their hydrophilic and oleophilic properties, a stable network can be formed between slurry particles, thereby improving particle dispersibility and uniformity. Furthermore, this special ratio of surfactants is well miscible with binders and conductive agents in the slurry, each playing its own role. This improves the slurry's viscosity, leveling properties, thixotropy, and surface energy during coating, ensuring good dispersion stability and leveling properties. It also effectively improves the edge thickness of the active coating, reducing thick edges.

[0038] This application controls the addition of anionic surfactants at a weight ratio of 85% to 95%, for example, any value or a range between any two of 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, and 95%; and controls the addition of nonionic surfactants at a weight ratio of 5% to 15%, for example, any value or a range between any two of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%.

[0039] The proportion of surfactant added to the electrode slurry in this application can be adjusted according to actual conditions, for example, selecting any value or a range between any two of 0.01%, 0.05%, 0.08%, 0.10%, 0.12%, 0.15%, 0.18%, 0.20%, 0.23%, 0.25%, 0.28%, 0.3%, 0.35%, 0.4%, 0.45%, 0.50%, 0.55%, 0.6%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.9%, 0.95%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2.0%.

[0040] In some embodiments, the nonionic surfactant accounts for 8% to 15% of the total surfactant weight, and the anionic surfactant accounts for 85% to 92% of the total surfactant weight.

[0041] In order to achieve a good synergistic effect with the negative electrode active material, conductive agent, binder and solvent, this application controls the weight ratio of nonionic surfactant and anionic surfactant to 8% to 15% and 85% to 92%, respectively. The resulting slurry coating of the negative electrode sheet has better leveling, dispersibility and uniformity, which can help improve the problem of thick edge of the electrode sheet.

[0042] In some embodiments, the amount of surfactant added is 0.05 to 1.5 wt% of the total amount of electrode slurry; for example, 0.05 to 1 wt%; further for example, 0.08 to 0.5 wt%; further for example, 0.08 to 0.2 wt%; and still for example, 0.1 wt%.

[0043] This application ensures good miscibility between the surfactant, conductive agent, binder, and solvent in the slurry, with a limited amount of added surfactant. Each component can fully exert its own function, and the mixed slurry has suitable viscosity, leveling properties, thixotropy, and surface energy. It can control the edge thickness of the active coating and improve the uniformity of electrode thickness and the phenomenon of thick edges.

[0044] The anionic surfactant selected in this application has a hydrophobic group of alkane and a hydrophilic group such as carboxyl, sulfate, sulfonic acid, phosphate, amino, hydroxy, ketone, sulfonamide [R-CO-N-SO2-R']-, iodate, aldehyde, or a coordinated anion [ROCe(NO3)5]. - Amino acid ions R-CHNH2COO - At least one of the following: an enol group.

[0045] In some embodiments, the anionic surfactant is selected from one or more of the following: disodium dodecyl polyoxyethylene ether sulfosuccinate, sodium dioctyl succinate sulfonate, sodium dodecylbenzene sulfonate, ammonium dodecyl polyacrylate, and ammonium dodecyl polyoxyethylene ether sulfate.

[0046] The anionic surfactant selected in this application has a suitable amount of polar functional groups in its molecular structure; these functional groups can stabilize the solid particles in the slurry by adsorbing them, thereby giving the slurry excellent dispersion and flow properties; in addition, this surfactant can effectively reduce the surface tension of the slurry and optimize the uniformity of the edge thickness of the active coating.

[0047] In some embodiments, the nonionic surfactant is selected from at least one of ethylhexanol polyoxypropylene polyoxyethylene ether, nonylphenol polyoxyethylene ether, polyoxyethylene hexadecyl ether, polyoxypropylene hexadecyl ether, and polyoxyethylene polyoxypropylene hexadecyl ether.

[0048] The nonionic surfactant selected in this application exhibits nonionic properties in aqueous media, possesses excellent stability, and demonstrates good solubility in water and organic solvents. This surfactant can be applied to both aqueous and oil-based slurry systems, effectively promoting the uniform distribution of active materials in different media, thereby imparting superior rheological properties to the dispersion system; this characteristic helps improve the uniformity of the edge thickness of the active coating on battery electrodes.

[0049] In some embodiments, the surfactant of this application may specifically be a combination of disodium dodecyl polyoxyethylene ether sulfosuccinate and ethylhexyl polyoxypropylene polyoxyethylene ether, which has a better effect on slurry dispersibility and leveling. When the two are added to the slurry in a weight ratio of 88:12, the effect of thinning the edge thickness of the active coating of the electrode sheet can be achieved to a greater extent.

[0050] In some embodiments, the viscosity of the battery negative electrode slurry is 3500 to 4500 mPa·s; for example, the viscosity of the negative electrode slurry is any value or a range between any two of 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, and 4500 mPa·s.

[0051] This application controls the viscosity of the negative electrode slurry to be between 3500 and 4500 mPa·s. Appropriate viscosity is crucial for uniform slurry coating, helping to maintain a consistent thickness at the edges of the electrode active material coating, thus preventing excessively thick edges. If the viscosity is unsuitable, whether too high or too low, it can lead to uneven coating, consequently affecting the consistency and overall performance of the battery. Furthermore, suitable viscosity can improve the slurry's fluidity, which is beneficial for increasing the battery's energy density, conductivity, filler density, stability, and extending battery life.

[0052] In some embodiments, the solid content of the battery negative electrode slurry is 60% to 70%, for example, 68%. This application controls the solid content of the negative electrode slurry to be 60% to 70%, which means that the proportion of negative electrode active material is relatively appropriate, which is beneficial to improving the battery cycle stability, charge and discharge performance, energy density and safety.

[0053] In some embodiments, the weight ratio of the negative electrode active material, conductive agent, binder, and surfactant is (90-95):(1.5-6):(1-3):(0.01-2); for example, (90-95):(1.5-6):(1-3):(0.05-1); further, (90-95):(1.5-6):(1-3):(0.05-0.5); and even further, (90-95):(1.5-6):(1-3):(0.05-0.2). The addition ratio of each component in the negative electrode slurry of this application can be adjusted according to the actual situation.

[0054] In some embodiments, the negative electrode active material is selected from natural graphite; the conductive agent is selected from conductive carbon black; the binder is selected from polyacrylic acid; and the solvent is selected from deionized water. The negative electrode active material, conductive agent, binder, solvent, etc., used in this application can be selected from the prior art according to actual conditions.

[0055] According to a second aspect of this application, a method for preparing the above-mentioned battery negative electrode slurry is provided, comprising the following steps: mixing raw materials of negative electrode active material, conductive agent, binder, solvent and surfactant according to the proportion of each raw material, stirring, and obtaining battery negative electrode slurry.

[0056] In some embodiments, the preparation method specifically includes the following steps:

[0057] Step S1: Mix the adhesive and solvent to form an adhesive solution; mix the conductive agent and solvent to form a conductive liquid; mix the surfactant and solvent to form a surfactant solution;

[0058] Step S2: Add the negative electrode active material to the adhesive and conductive liquid, add solvent for the first viscosity adjustment, add surfactant solution, add solvent for the second viscosity adjustment until the viscosity of the slurry reaches the preset viscosity;

[0059] In some embodiments, the mass concentration of the adhesive solution is 8%–20%; the mass concentration of the conductive liquid is 10%–12%; the mass concentration of the surfactant solution is 0.8%–1.5%; and the preset viscosity is 3500–4500 mPa·s. The stepwise mixing of the raw material components in this application is beneficial for the uniform dispersion of the slurry.

[0060] According to a third aspect of this application, a battery negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active coating attached to the surface of the negative electrode current collector; the slurry for preparing the negative electrode active coating is the aforementioned battery negative electrode slurry.

[0061] The negative electrode sheet prepared by coating with the negative electrode slurry with good leveling properties, viscosity and surface energy as described in this application has a small thin area thickness and a consistent and uniform active coating thickness; there is no obvious thick edge phenomenon.

[0062] According to a fourth aspect of this application, a battery is provided, including a negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet of the aforementioned battery.

[0063] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0064] Example 1

[0065] (1) Prepare each raw material according to the following weight ratio: natural graphite: SP conductive agent: PAA binder: surfactant is 95:3:1.95:0.05; wherein, the surfactant is formed by compounding dodecyl alcohol polyoxyethylene ether sulfosuccinate disodium salt and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0066] (2) The binder was uniformly dispersed in NMP solvent to obtain a 10% (w / w) adhesive solution; the conductive agent was uniformly dispersed in solvent to obtain a 12% (w / w) conductive liquid; the surfactant was dispersed in solvent to obtain a 1.2% (w / w) surfactant solution; natural graphite, adhesive solution (10 wt.%), and conductive solution (12 wt.%) were added sequentially to a mixing tank, and after high-speed dispersion, solvent was added to adjust the viscosity to 6000 mPa·s, and 0.05 wt% (w / w) of surfactant solution (1.2 wt.%) was added and dispersed at low speed for 30 min; solvent was added again to ensure that the final slurry viscosity was 4000 mPa·s and the slurry solid content was 68%; then, the copper foil was coated, rolled, and slit sequentially to obtain a negative electrode sheet, the edge of which did not have obvious thick edges; Figure 1 The coating thickness in the normal zone is 3 and the coating thickness in the thinned zone is 2.

[0067] Example 2

[0068] The difference between Example 2 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0069] The composition of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.92:0.08; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0070] Example 3

[0071] The difference between Example 3 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0072] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0073] Example 4

[0074] The difference between Example 4 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0075] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.88:0.12; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0076] Example 5

[0077] The difference between Example 5 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0078] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.99:0.01; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0079] Example 6

[0080] The difference between Example 6 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0081] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.85:0.15; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0082] Example 7

[0083] The difference between Example 7 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0084] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.8:0.2; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0085] Example 8

[0086] The difference between Example 8 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0087] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.7:0.3; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0088] Example 9

[0089] The difference between Example 9 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0090] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.5:0.5; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0091] Example 10

[0092] The difference between Example 10 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0093] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.2:0.8; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0094] Example 11

[0095] The difference between Example 11 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0096] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.0:1.0; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0097] Example 12

[0098] The difference between Example 12 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0099] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:2.5:1.0:1.5; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0100] Example 13

[0101] The difference between Example 13 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0102] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:1.5:1.5:2.0; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 95:5.

[0103] Example 14

[0104] The difference between Example 14 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0105] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 92:8.

[0106] Example 15

[0107] The difference between Example 15 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0108] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 88:12.

[0109] Example 16

[0110] The difference between Example 16 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0111] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 85:15.

[0112] Example 17

[0113] The difference between Example 17 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0114] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding sodium dodecylbenzene sulfonate and polyoxyethylene hexadecyl ether in a weight ratio of 88:12.

[0115] Example 18

[0116] The difference between Example 18 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0117] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding sodium dioctyl succinate and polyoxyethylene polyoxypropylene hexadecyl ether in a weight ratio of 88:12.

[0118] Example 19

[0119] The difference between Example 19 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0120] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding dodecyl polyacrylate ammonium and ethylhexanol polyoxypropylene polyoxyethylene ether in a weight ratio of 88:12.

[0121] Example 20

[0122] The difference between Example 20 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0123] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate, sodium dioctyl succinate sulfonate, nonylphenol polyoxyethylene ether, and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 44:44:6:6.

[0124] Comparative Example 1

[0125] The difference between Comparative Example 1 and Example 1 is that no surfactant is added to the slurry.

[0126] The ratio of natural graphite, SP conductive agent, and PAA binder is 95:3:2.

[0127] Comparative Example 2

[0128] The difference between Comparative Example 2 and Example 1 is that the surfactant added to the slurry is an anionic surfactant; the ratio of natural graphite:SP conductive agent:PAA binder:anionic surfactant is 95:3:1.9:0.1; wherein, the anionic surfactant is disodium dodecyl polyoxyethylene ether sulfosuccinate.

[0129] Comparative Example 3

[0130] The difference between Comparative Example 3 and Example 1 is that the surfactant added to the slurry is a nonionic surfactant; the ratio of natural graphite: SP conductive agent: PAA binder: nonionic surfactant is 95:3:1.9:0.1; wherein, the nonionic surfactant is ethylhexyl alcohol polyoxypropylene polyoxyethylene ether.

[0131] Comparative Example 4

[0132] The difference between Comparative Example 4 and Example 1 is that the proportion of surfactant added to the slurry is different; the ratio of natural graphite: SP conductive agent: PAA binder: surfactant is 95:1.5:1.3:2.2.

[0133] Comparative Example 5

[0134] The difference between Comparative Example 6 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0135] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl alcohol polyoxyethylene ether sulfosuccinate and ethylhexyl alcohol polyoxypropylene polyoxyethylene ether in a weight ratio of 97:3.

[0136] Comparative Example 6

[0137] The difference between Comparative Example 6 and Example 1 is that the formulations of the raw materials in the slurry are different;

[0138] The ratio of natural graphite, SP conductive agent, PAA binder, and surfactant is 95:3:1.9:0.1; wherein the surfactant is formed by compounding disodium dodecyl polyoxyethylene ether sulfosuccinate and ethylhexyl polyoxypropylene polyoxyethylene ether in a weight ratio of 10:90.

[0139] Comparative Example 7

[0140] The difference between Comparative Example 7 and Example 1 is that the surfactant added to the slurry is different; the ratio of natural graphite:SP conductive agent:PAA binder:surfactant is 95:3:1.9:0.1; the surfactant is formed by compounding ammonium dodecyl sulfate and polyoxyethylene dodecyl ether in a weight ratio of 5:5.

[0141] The thickness of the thinned area of ​​the negative electrode sheet in Examples 1-20 and Comparative Examples 1-7 was tested.

[0142] Table 1

[0143]

[0144]

[0145] As shown in Table 1, the coating thickness in the normal area of ​​the negative electrode sheet coated in Examples 1-20 of this application is 92.5 μm, and the coating thickness in the thinned area is concentrated between 83.9 and 88.6 μm. It can be seen that when the surfactant addition is 0.1% and the ratio of anionic surfactant to nonionic surfactant is (85-92):(8-15), the coating thickness in the thinned area of ​​the negative electrode sheet is smaller, concentrated between 83.9 and 85.4 μm, and the thickness improvement effect is better. When the compounding ratio is (85-88):(12-15), the coating thickness in the thinned area is concentrated between 83.9 and 84.7 μm, and the coating thickness improvement effect is further improved. When the compounding ratio is 88:12, the coating thickness in the thinned area is 83.9 μm, and the thickness improvement effect is the best.

[0146] In Comparative Example 1, no surfactant was added to the negative electrode slurry; the coating thickness in the thinned area was 98.8 μm, which is about 10-15 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This shows that by adding a specially formulated surfactant in a specific ratio to the negative electrode slurry, this application can significantly reduce the coating thickness in the thinned area, resulting in better uniformity of the negative electrode sheet coating thickness, which can promote the stability and consistency of battery performance.

[0147] In Comparative Example 2, only anionic surfactants were added to the negative electrode slurry; the coating thickness in the thinned area was 90.6 μm, which is approximately 2–7 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This indicates that although the surfactants are mainly anionic surfactants with nonionic surfactants as a supplement, adding only anionic surfactants to the negative electrode slurry has limited effect on improving the edge thickness of the negative electrode sheet coating. Combining the two surfactants in a specific ratio can further improve the coating thickness.

[0148] In Comparative Example 3, only a nonionic surfactant was added to the negative electrode slurry; the coating thickness in the thinned area was 92.0 μm, which is about 6-8 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This shows that simply adding a nonionic surfactant to the negative electrode slurry has no significant effect on improving the edge thickness of the negative electrode sheet coating.

[0149] In Comparative Example 4, the surfactant content in the negative electrode slurry was 2.2%; the coating thickness in the thinned area was 89.0 μm, which is approximately 0.4–5 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This illustrates that adding the specific proportion of the composite surfactant of this application, if the amount added is too large, is also not conducive to improving the edge thickness of the negative electrode sheet coating.

[0150] In Comparative Example 5, the ratio of anionic to nonionic surfactant added to the negative electrode slurry was 97:3; the coating thickness in the thinned area was 89.2 μm, which is approximately 0.6–5 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This indicates that even with an excessive amount of anionic surfactant, the special ratio of surfactants used in this application cannot effectively improve the problem of thick edges on the negative electrode sheet coating due to the unsuitable mixing ratio of anionic and nonionic surfactants.

[0151] In Comparative Example 6, the ratio of anionic to nonionic surfactant added to the negative electrode slurry was 10:90; the coating thickness in the thinned area was 90.9 μm, which is approximately 2–7 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This demonstrates that when using the mixed surfactants of this application, if the ratio of anionic to nonionic surfactants is inappropriate, and the anionic surfactant is used as a supplement while the nonionic surfactant is the main agent, the problem of thick edges in the negative electrode sheet coating cannot be effectively improved.

[0152] Comparative Example 7 added different types of anionic and nonionic surfactants to the negative electrode slurry in a 5:5 ratio; the measured coating thickness in the thinned area was 90.0 μm, which is approximately 1–6 μm thicker than the coating thickness in the thinned area of ​​the electrode sheet in the embodiments of this application. This indicates that selecting other types of surfactants and inappropriate mixing ratios are less effective in improving the edge thickness problem of the negative electrode sheet coating.

[0153] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0154] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery negative electrode slurry, characterized in that, The battery negative electrode slurry comprises negative electrode active material, conductive agent, binder, surfactant, and solvent; wherein the surfactant is composed of nonionic surfactant and anionic surfactant, the nonionic surfactant accounting for 5%~15% of the total surfactant by weight; the anionic surfactant accounting for 85%~95% of the total surfactant by weight; and the surfactant accounting for 0.01%~2% of the total surfactant in the battery negative electrode slurry by weight. The anionic surfactant is selected from one or more of the following: disodium dodecyl polyoxyethylene ether sulfosuccinate, sodium dioctyl succinate sulfonate, sodium dodecylbenzene sulfonate, ammonium dodecyl alcohol polyoxyethylene ether sulfate, and ammonium dodecyl polyacrylate. The nonionic surfactant is selected from at least one of ethylhexanol polyoxypropylene polyoxyethylene ether, nonylphenol polyoxyethylene ether, polyoxyethylene polyoxypropylene hexadecyl ether, polyoxyethylene hexadecyl ether, and polyoxypropylene hexadecyl ether.

2. The battery negative electrode slurry according to claim 1, characterized in that, The nonionic surfactant accounts for 8% to 15% of the total surfactant by weight; the anionic surfactant accounts for 85% to 92% of the total surfactant by weight.

3. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The surfactant accounts for 0.05~1.5 wt% of the weight of the negative electrode slurry in the battery.

4. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The surfactant accounts for 0.05~1wt% of the weight of the negative electrode slurry in the battery.

5. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The surfactant accounts for 0.08~0.5 wt% of the weight of the negative electrode slurry in the battery.

6. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The surfactant accounts for 0.08~0.2wt% of the weight of the negative electrode slurry in the battery.

7. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The surfactant is composed of disodium dodecyl polyoxyethylene ether sulfosuccinate and ethylhexyl polyoxypropylene polyoxyethylene ether. And / or, the viscosity of the battery negative electrode slurry is 3500~4500 mPa·S; And / or, the solid content of the battery negative electrode slurry is 60%~70%.

8. The battery negative electrode slurry according to claim 1 or 2, characterized in that, The weight ratio of the negative electrode active material, the conductive agent, the binder, and the surfactant is (90~95):(1.5~6):(1~3):(0.01~2). And / or, the negative electrode active material is selected from natural graphite; And / or, the conductive agent is selected from conductive carbon black; And / or, the adhesive is selected from polyacrylic acid; And / or, the solvent is selected from deionized water.

9. A method for preparing the battery negative electrode slurry according to any one of claims 1 to 8, characterized in that, The preparation method includes the following steps: mixing raw materials such as negative electrode active material, conductive agent, binder, solvent and surfactant according to the proportion of each raw material, stirring, and obtaining the battery negative electrode slurry.

10. The method for preparing the battery negative electrode slurry according to claim 9, characterized in that, The preparation method specifically includes the following steps: Step S1: Mix the adhesive and the solvent to form an adhesive solution; mix the conductive agent and the solvent to form a conductive liquid; mix the surfactant and the solvent to form a surfactant solution; Step S2: Add the negative electrode active material to the adhesive and the conductive liquid, add the solvent for the first viscosity adjustment, add the surfactant solution, add the solvent for the second viscosity adjustment until the viscosity of the slurry reaches the preset viscosity.

11. The method for preparing the battery negative electrode slurry according to claim 10, characterized in that, The mass concentration of the adhesive solution is 8%~20%; And / or, the mass concentration of the conductive liquid is 10%~12%; And / or, the mass concentration of the surfactant solution is 0.8%~1.5%; And / or, the preset viscosity is 3500~4500 mPa·S.

12. A battery negative electrode sheet, comprising a negative electrode current collector and a negative electrode active coating attached to the surface of the negative electrode current collector; characterized in that, The slurry for preparing the negative electrode active coating is the battery negative electrode slurry according to any one of claims 1 to 8.

13. A battery comprising a negative electrode, characterized in that, The negative electrode sheet is the battery negative electrode sheet as described in claim 12.

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