Negative electrode sheet and preparation method therefor, battery, battery pack, and electric device

Abstract

A negative electrode sheet and a preparation method therefor, a battery, a battery pack, and an electric device. The negative electrode sheet comprises a negative electrode active layer, and the Zeta potential of the negative electrode active layer is less than or equal to -53 mV. In the negative electrode sheet provided in the present application, the Zeta potential of the negative electrode active layer is limited to be less than or equal to -53 mV, so that electrostatic repulsion between particles can be enhanced, thereby preventing particle aggregation, improving dispersion uniformity and stability of a negative electrode active material in the negative electrode sheet, avoiding black spots or dark streaks on the negative electrode sheet, and reducing the risk of local lithium precipitation of a battery during charging.

Description

A negative electrode sheet and its preparation method, a battery, a battery pack, and an electrical device thereof.

[0001] This application claims priority to Chinese Patent Application No. 202510121446.8, filed on January 24, 2025, entitled “A negative electrode sheet and its preparation method, a battery, a battery pack and an electrical device thereof”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery technology, and in particular relates to a negative electrode sheet and its preparation method, a battery, a battery pack and an electrical device. Background Technology

[0003] Lithium-ion rechargeable batteries are widely used in electronic products, electric vehicles, and energy storage devices due to their advantages such as high energy density, long cycle life, and high operating voltage. With the rapid development of portable electronic products and electric vehicles, there are higher requirements for the fast-charging performance and safety of lithium-ion rechargeable batteries.

[0004] During fast charging, lithium-ion batteries are prone to lithium metal deposition on the negative electrode, leading to capacity loss and safety hazards. This is especially true when the active material in the negative electrode is unevenly distributed, making localized lithium deposition highly likely. Therefore, reducing the risk of lithium deposition on the negative electrode in lithium-ion batteries is a pressing issue that needs to be addressed in this field. Summary of the Invention

[0005] The main objective of this application is to provide a negative electrode that can reduce the risk of lithium plating.

[0006] This application also provides a method for preparing a negative electrode sheet, which can prepare the above-mentioned negative electrode sheet, and the process is simple and low in cost.

[0007] This application also provides a battery including the above-mentioned negative electrode, thereby reducing the risk of lithium plating.

[0008] This application also provides a battery pack including the above-described battery, thereby reducing the risk of lithium plating.

[0009] This application also provides an electrical device including the aforementioned battery or battery pack, thus the battery performance of the electrical device is superior.

[0010] In a first aspect, this application provides a negative electrode sheet, the negative electrode sheet including a negative electrode active layer, the zeta potential of the negative electrode active layer being less than or equal to -53mV.

[0011] As described above, the zeta potential of the negative electrode active layer is -75mV to -63mV.

[0012] As described above, the negative electrode active layer comprises a negative electrode active material and a dispersant, wherein the sum of the zeta potential of the dispersant and the zeta potential of the negative electrode active material is -125mV to -90mV.

[0013] In the negative electrode sheet described above, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV.

[0014] As described above, the zeta potential of the negative electrode active material is less than or equal to -33mV.

[0015] As described above, the zeta potential of the negative electrode active material is -55mV to -40mV.

[0016] As described above, in the negative electrode, the zeta potential of the dispersant is less than or equal to -50mV.

[0017] As described above, the zeta potential of the dispersant in the negative electrode is -70mV to -58mV.

[0018] As described above, the negative electrode active material comprises at least one of natural graphite, artificial graphite, hard carbon, mesophase carbon microspheres, silicon dioxide, and silicon-carbon; and / or, the D50 particle size of the negative electrode active material is 6.5 μm to 14 μm; and / or, the specific surface area of ​​the negative electrode active material is 0.5 g / cm³. 3 ~4g / cm 3 .

[0019] The negative electrode sheet as described above, wherein the dispersant comprises at least one of carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, sodium alginate, polymethacrylic acid and carboxymethyl chitosan; and / or, the degree of substitution of the dispersant is 0.5 to 1.1.

[0020] As described above, the negative electrode active layer further includes a binder and a conductive agent.

[0021] Secondly, this application provides a method for preparing the negative electrode sheet as described above, comprising the following steps:

[0022] A negative electrode slurry, comprising a negative electrode active material, dispersant, conductive agent, binder, and solvent, is coated onto a negative electrode current collector, dried, and rolled to form a negative electrode active layer with a zeta potential less than or equal to -53mV, thus obtaining the negative electrode sheet.

[0023] In the above-described method for preparing the negative electrode, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -125mV to -90mV.

[0024] And / or, the Zeta potential of the negative electrode active material is less than or equal to -33mV;

[0025] And / or, the Zeta potential of the dispersant is less than or equal to -50mV.

[0026] In the above-described method for preparing the negative electrode, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV;

[0027] And / or, the Zeta potential of the negative electrode active material is -55mV to -40mV;

[0028] And / or, the Zeta potential of the dispersant is -70mV to -58mV.

[0029] Thirdly, this application provides a battery, including the negative electrode sheet as described above or the negative electrode sheet prepared by the method described above.

[0030] Fourthly, this application provides a battery pack including the battery as described above.

[0031] Fifthly, this application provides an electrical device, including the battery or battery pack described above.

[0032] The negative electrode sheet provided in this application, by limiting the Zeta potential of the negative electrode active layer to less than or equal to -53mV, can enhance the electrostatic repulsion between particles, prevent particle aggregation, improve the dispersion uniformity and stability of the negative electrode active material in the negative electrode sheet, avoid the appearance of black spots or dark streaks on the negative electrode sheet, and reduce the risk of local lithium plating during battery charging. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 is a Zeta potential test spectrum of the negative electrode active material in Example 1 of this application;

[0035] Figure 2 is a Zeta potential test spectrum of the negative electrode active material in Example 8 of this application;

[0036] Figure 3 shows the Zeta potential test spectrum of the negative electrode active material in Comparative Example 2 of this application;

[0037] Figure 4 is a schematic diagram of the structure of a negative electrode sheet provided in this application;

[0038] Figure 5 is a schematic diagram of a battery pack provided in this application;

[0039] Figure 6 is a schematic diagram of the structure of an electronic device provided in this application.

[0040] Figure label:

[0041] 100 - Negative electrode sheet; 110 - Negative electrode current collector; 120 - Negative electrode active layer; 2 - Battery; 3 - Battery pack; 4 - Electrical equipment. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Lithium-ion rechargeable batteries, as highly efficient energy storage devices, have become core components of modern electronic products, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and high operating voltage. However, with the rapid popularization of portable electronic products and electric vehicles, users have placed higher demands on the fast-charging performance and safety of batteries. The application of fast-charging technology can significantly shorten charging time and improve the efficiency of device use, but it also brings new technical challenges.

[0044] In lithium-ion batteries, the design and material selection of the negative electrode have a crucial impact on the overall battery performance. The negative electrode typically comprises a negative electrode active material, a dispersant, and a binder, and is loaded onto a negative electrode current collector. During fast charging, the electrochemical reactions within the battery intensify, significantly increasing the electrochemical polarization of the negative electrode. This polarization leads to the direct deposition of lithium ions on the negative electrode surface, forming lithium metal deposition. This not only causes rapid capacity decay but may also trigger safety hazards such as short circuits and thermal runaway. In particular, when the distribution of the negative electrode active material is uneven, the increase in local current density exacerbates localized lithium deposition. Therefore, how to reduce the risk of lithium metal deposition by improving the material properties and structural design of the negative electrode has become an urgent problem to be solved in the current lithium battery technology field. This application reduces the lithium deposition problem in lithium-ion batteries by adjusting the Zeta potential of the negative electrode active layer to improve the dispersion uniformity and stability of the negative electrode active material in the negative electrode.

[0045] In a first aspect, this application provides a negative electrode 100, which includes a negative electrode active layer 120. The zeta potential of the negative electrode active layer is less than or equal to -53mV, for example, it can be a range of -90mV, -80mV, -75mV, -71mV, -65mV, -63mV, -60mV, -53mV or any two of these.

[0046] It is understood that the Zeta potential of the negative electrode active layer can reflect the interaction between particles in the negative electrode active layer. In this application, the Zeta potential of the negative electrode active layer is less than or equal to -53mV, which can enhance the electrostatic repulsion between particles in the negative electrode active layer, prevent particle agglomeration, and allow the negative electrode active material to be uniformly and stably distributed in the negative electrode sheet. This effectively reduces the risk of lithium plating in lithium-ion batteries under fast charging conditions, avoids the appearance of black spots or dark streaks on the negative electrode sheet, and improves the safety and lifespan of the battery.

[0047] In one embodiment of this application, the Zeta potential of the negative electrode active layer is -75mV to -63mV, for example, it can be a range of -75mV, -74mV, -73mV, -72mV, -71mV, -70mV, -69mV, -68mV, -67mV, -66mV, -65mV, -64mV, -63mV, or any combination thereof. As an optional embodiment, this can further improve the dispersion uniformity and stability of the negative electrode active material in the negative electrode sheet, effectively reduce lithium metal deposition, reduce the risk of lithium plating in the battery, and improve the overall performance and safety of the battery.

[0048] In one embodiment of this application, the negative electrode active layer includes a negative electrode active material and a dispersant. The sum of the zeta potential of the dispersant and the zeta potential of the negative electrode active material is -125mV to -90mV. For example, it can be a range of -125mV, -120mV, -115mV, -110mV, -105mV, -100mV, -95mV, -90mV, or any combination thereof.

[0049] It is understood that the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material reflects the interaction between the negative electrode active material and the dispersant. The negative electrode sheet of this application includes a negative electrode active layer, which comprises a negative electrode active material and a dispersant. The sum of the Zeta potentials of the dispersant and the negative electrode active material is -125mV to -90mV, which allows for an appropriate charge on both the dispersant and the negative electrode active material, facilitating material dispersion in solution and resulting in a more uniform negative electrode sheet. Furthermore, it enhances the electrostatic repulsion between particles formed by the interaction between the negative electrode active material and the dispersant, preventing particle aggregation. This improves the dispersion uniformity and stability of the negative electrode active material and dispersant in the negative electrode sheet, effectively reducing the risk of lithium plating under fast charging conditions, avoiding black spots or dark streaks on the negative electrode sheet, and improving battery safety and lifespan.

[0050] In some embodiments of this application, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV, for example, it can be a range of -112mV, -111mV, -110mV, -109mV, -108mV, -107mV, -106mV, -105mV, -104mV, -103mV, -102mV, -101mV, -100mV, or any combination thereof. As an optional embodiment, this can further improve the dispersion uniformity and stability of the negative electrode active material and dispersant in the negative electrode sheet, effectively reduce lithium metal deposition, reduce the risk of lithium plating in the battery, and improve the overall performance and safety of the battery.

[0051] In some embodiments of this application, the Zeta potential of the negative electrode active material is less than or equal to -33mV, for example, it can be a range of -100mV, -95mV, -90mV, -85mV, -80mV, -75mV, -70mV, -65mV, -60mV, -50mV, -40mV, -35mV, -33mV or any combination thereof.

[0052] It is understandable that the zeta potential of the negative electrode active material reflects the charge state of its surface and affects its interaction with the dispersant. The zeta potential of the negative electrode active material can be adjusted by simultaneously changing its D50 particle size and specific surface area. Negative electrode active materials with zeta potentials within this range can better bind with the dispersant and be uniformly and stably dispersed in the negative electrode sheet, avoiding black spots or dark streaks and reducing the risk of localized lithium plating during battery charging.

[0053] In some embodiments, the D50 particle size of the negative electrode active material is 6.5 μm to 14 μm, for example, it can be a range of 6.5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or any combination thereof.

[0054] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.5 g / cm³. 3 ~4g / cm 3 For example, it can be 0.5 g / cm³. 3 1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.5g / cm 3 2g / cm 3 2.5g / cm 3 3g / cm 3 3.5g / cm 3 4g / cm 3 or a range consisting of any two of them.

[0055] In some embodiments of this application, the Zeta potential of the negative electrode active material is -55mV to -40mV, for example, it can be a range of -55mV, -50mV, -48mV, -47mV, -45mV, -42mV, -40mV, or any combination thereof. As an optional embodiment, the negative electrode active material can be further better combined with the dispersant, uniformly and stably dispersed in the negative electrode sheet, avoiding black spots or dark streaks on the negative electrode sheet, and reducing the risk of localized lithium plating during battery charging.

[0056] In some embodiments of this application, the Zeta potential of the dispersant is less than or equal to -50mV, for example, it can be a range of -80mV, -75mV, -70mV, -65mV, -60mV, -55mV, -50mV or any two of these.

[0057] This application allows adjustment of the zeta potential of the dispersant by altering its molecular structure. For example, the degree of substitution of carboxymethyl cellulose (CMC), i.e., the average number of hydroxyl groups substituted in each monomer, can be changed; or the type of dispersant can be altered by using different polymerizable monomers. In this application, the zeta potential of the dispersant is within the aforementioned range, enabling the negative electrode active material to exhibit good dispersibility and stability within the negative electrode sheet. This facilitates the formation of a uniform electrode structure. This uniformity reduces current density fluctuations within the electrode, thereby lowering the risk of localized overpotential and lithium metal deposition. It effectively reduces the risk of localized lithium deposition during fast charging, thus improving battery safety.

[0058] In some embodiments, the degree of substitution of the dispersant is 0.5 to 1.1, for example, it can be a range of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or any two of these.

[0059] In this application, the degree of substitution of the dispersant can be adjusted by conventional methods, and there are no restrictions on this.

[0060] In some embodiments of this application, the zeta potential of the dispersant is -70mV to -58mV, for example, it can be a range of -70mV, -68mV, -64mV, -62mV, -60mV, -58mV, or any combination thereof. As an optional embodiment, the dispersibility and stability of the negative electrode active material can be further improved, thereby reducing the risk of local overpotential and lithium metal deposition, effectively reducing the risk of local lithium deposition during fast charging, and thus improving battery safety.

[0061] In some embodiments of this application, the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, mesophase carbon microspheres, silicon oxide, and silicon-carbon.

[0062] One embodiment of this application provides an example where the negative electrode active material is artificial graphite. Alternatively, the artificial graphite can be primary granules or secondary granulated granules, or it can be granules with amorphous carbon coating on their surface.

[0063] The aforementioned negative electrode active material can be well combined with the dispersant and uniformly and stably dispersed in the negative electrode sheet, avoiding black spots or dark streaks on the negative electrode sheet and reducing the risk of local lithium plating during battery charging.

[0064] In some embodiments of this application, the dispersant includes at least one of carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0065] One embodiment of this application provides an example in which the dispersant is carboxymethyl cellulose (CMC).

[0066] The aforementioned dispersant can effectively disperse the negative electrode active material particles, prevent particle agglomeration, facilitate the formation of a uniform electrode structure, reduce fluctuations in current density inside the electrode, thereby reducing the risk of local lithium plating during fast charging and improving battery safety.

[0067] In some embodiments of this application, the negative electrode active layer further includes a binder and a conductive agent, wherein the binder includes at least one of styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM), fluororubber (FKM), modified styrene-butadiene rubber, modified acrylonitrile-butadiene rubber, modified acrylic rubber, and modified fluororubber.

[0068] One embodiment of this application provides an example where the adhesive is styrene-butadiene rubber (SBR).

[0069] In some embodiments, the conductive agent includes at least one of conductive carbon black, Ketjen black, graphene, conductive carbon fiber, and conductive carbon nanotubes.

[0070] In some embodiments, the conductive agent includes one or more of conductive carbon black and conductive carbon nanotubes.

[0071] The binder in this application can improve the mechanical strength of the negative electrode, prevent material detachment due to volume changes during charge-discharge cycles, improve the stability of the negative electrode during electrochemical cycles, reduce material peeling and damage to the electrode structure, thereby extending the battery's service life.

[0072] The addition of conductive agents can improve the conductivity of the negative electrode, ensuring that electrons can be quickly transferred to the negative electrode active material particles, which is conducive to achieving uniform current distribution and reducing overpotential and lithium plating caused by excessive local current density.

[0073] In some embodiments of this application, the mass percentage of the negative electrode active material in the negative electrode active layer is greater than or equal to 50%, for example, it can be a range of 50%, 55%, 60%, 65%, 70%, 80%, 90%, 95%, 97%, 99% or any two of these.

[0074] In some embodiments, the mass percentage of the negative electrode active material in the negative electrode active layer is 90% to 99%.

[0075] In some embodiments, the mass percentage of the dispersant in the negative electrode active layer is 0.1% to 10%, for example, it can be a range of 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0076] In some embodiments, the mass percentage of the dispersant in the negative electrode active layer is 0.3% to 1.5%.

[0077] In some embodiments, the mass percentage of the binder in the negative electrode active layer is 0.1% to 10%, for example, it can be a range of 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0078] In some embodiments, the mass percentage of the binder in the negative electrode active layer is 0.5% to 2.5%.

[0079] In some embodiments, the mass percentage of the conductive agent in the negative electrode active layer is 0.2% to 20%, for example, it can be a range of 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, or any combination thereof.

[0080] In some embodiments, the mass percentage of the conductive agent in the negative electrode active layer is 0.5% to 1.5%.

[0081] Secondly, this application provides a method for preparing the negative electrode 100 as described above, comprising the following steps:

[0082] A negative electrode slurry, comprising negative electrode active material, dispersant, conductive agent, binder, and solvent, is coated onto a negative electrode current collector 110, dried, and rolled to form a negative electrode active layer 120 with a zeta potential less than or equal to -53mV, thus obtaining a negative electrode sheet 100.

[0083] Specifically, the preparation method of the negative electrode 100 of this application may include the following steps:

[0084] 1) Anode slurry is prepared by mixing negative electrode active material, dispersant, binder, conductive agent, solvent, and other components using dry and / or wet mixing methods. For example, the dispersant is first dissolved in a solvent to obtain a dispersion solution; then, the negative electrode active material and conductive agent dry powder are mixed, and then a portion of the dispersion solution is added and kneaded. The remaining dispersion solution and an appropriate amount of solvent are then added for dilution and stirring. Finally, the binder is added and stirred until homogeneous to obtain the corresponding negative electrode slurry.

[0085] 2) Transfer the uniformly mixed negative electrode slurry obtained above to a coating machine, and coat the negative electrode slurry onto the negative electrode current collector 110 using the coating machine. The coating can be applied to either side or both sides of the negative electrode current collector. The negative electrode current collector is typically a conductive structure made of a metal with good conductivity that does not react with the active material (such as copper, nickel, titanium, and stainless steel). This application does not limit the shape of the negative electrode current collector; for example, it can be foil, sheet, mesh, etc.

[0086] As an optional implementation, the negative electrode current collector 110 is a copper foil. When the negative electrode current collector is a copper foil, its thickness is not particularly limited and can be between 6 μm and 20 μm. Furthermore, the negative electrode slurry can be coated on only one side of the negative electrode current collector or on both sides; as an optional implementation, the negative electrode slurry can be coated on both sides of the negative electrode current collector. The areal density of the negative electrode active material on the negative electrode sheet can be controlled through the coating process.

[0087] As shown in Figure 4, the negative electrode 100 includes a negative electrode current collector 110 and a negative electrode active layer 120 present on both sides of the negative electrode current collector.

[0088] 3) The negative electrode current collector loaded with negative electrode slurry is dried in an oven to obtain a negative electrode sheet 100 with a negative electrode active material layer 120. The drying temperature and time are appropriately selected according to the solvent used and the solid content of the slurry. For example, the drying temperature can be between 70℃ and 110℃, and the drying time can be between 10s and 300s.

[0089] 4) After the negative electrode sheet is dried, it can be rolled. Rolling can control the thickness of the negative electrode sheet and the compaction density of the negative electrode active material.

[0090] It should be noted that in step 1), the solid content of the negative electrode slurry can be above 40%, and can be between 45% and 60%. When the solid content of the negative electrode slurry is within the above range, it can not only effectively improve the drying efficiency in the preparation process of the negative electrode sheet, but also improve the stability and fluidity of the negative electrode slurry, making the coating process more uniform and the distribution of active materials and dispersants on the obtained negative electrode sheet more uniform.

[0091] The negative electrode sheet prepared by the above method is less prone to local lithium plating. This is because the above method can avoid the agglomeration of negative electrode active material in the slurry and the black spots and dark streaks formed during the coating process, so that the negative electrode active material, dispersant, binder and conductive agent are uniformly dispersed in the negative electrode sheet.

[0092] In some embodiments of this application, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -125mV to -90mV, for example, it can be a range of -125mV, -120mV, -115mV, -112mV, -110mV, -105mV, -100mV, -95mV, -90mV or any combination thereof.

[0093] In some embodiments of this application, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV.

[0094] In some embodiments, the Zeta potential of the negative electrode active material is less than or equal to -33mV, for example, it can be a range of -100mV, -95mV, -90mV, -85mV, -80mV, -75mV, -70mV, -65mV, -60mV, -50mV, -40mV, -35mV, -33mV or any combination thereof.

[0095] In some embodiments, the Zeta potential of the negative electrode active material is -55mV to -40mV.

[0096] In some embodiments, the Zeta potential of the dispersant is less than or equal to -50mV, for example, it can be a range of -80mV, -75mV, -70mV, -65mV, -60mV, -55mV, -50mV or any two of these.

[0097] In some embodiments, the Zeta potential of the dispersant is -70mV to -58mV.

[0098] In this application, the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material, the Zeta potential of the negative electrode active material, and the Zeta potential of the dispersant are all within the above-mentioned range. This is beneficial to improve the dispersion uniformity and stability of the negative electrode active material in the negative electrode sheet, effectively reduce lithium metal deposition, reduce the risk of lithium deposition in the battery, and improve the overall performance and safety of the battery.

[0099] In the preparation process of the negative electrode sheet provided in this application, the Zeta potential of the negative electrode active material, the Zeta potential of the dispersant, the sum of the Zeta potentials of the dispersant and the negative electrode active material, and the Zeta potential of the negative electrode active layer may deviate from the Zeta potentials of the negative electrode active material, the dispersant, the sum of the Zeta potentials of the dispersant and the negative electrode active material, and the negative electrode active layer obtained from the negative electrode sheet obtained after disassembly from the battery. However, the deviation is within the error range. Therefore, the Zeta potentials of the negative electrode active material, the dispersant, the sum of the Zeta potentials of the dispersant and the negative electrode active material, and the negative electrode active layer in the preparation process of the negative electrode sheet are basically consistent with the Zeta potentials of the negative electrode active material, the dispersant, the dispersant, the sum of the Zeta potentials of the dispersant and the negative electrode active material, and the negative electrode active layer in the negative electrode sheet.

[0100] The parameters of this application can be obtained from the negative electrode sheet obtained after disassembling the battery as follows: After obtaining the negative electrode sheet, the negative electrode active layer on the negative electrode sheet can be scraped off and ultrasonically dispersed in water at 70℃~80℃. After centrifugation, the supernatant and precipitate are vacuum dried at 80℃. After drying the supernatant, a dispersant is obtained; after drying the precipitate, it is heated to 700℃ in a N2 atmosphere and kept at that temperature for 5 hours to remove the binder, and then cooled to obtain the negative electrode active material. The final negative electrode active material may contain some binder and conductive agent residues, but these have no significant impact on the Zeta potential test of the negative electrode active material.

[0101] Test of the zeta potential of the negative electrode active layer: After scraping off the negative electrode active layer from the negative electrode sheet, it is mixed with water at a mass ratio of 1:200, ultrasonically dispersed for 30 minutes to form a solution, and the zeta potential of the solution is tested using an electrophoretic light scattering instrument.

[0102] Test of Zeta potential of negative electrode active material: The negative electrode active material and ethanol were mixed at a mass ratio of 1:1000 and ultrasonically dispersed for 10 min to form a solution. The Zeta potential of the solution was then tested using an electrophoretic light scattering instrument.

[0103] Test of Zeta potential of dispersant: Disperse the dispersant in water to form a solution with a mass fraction of 0.01 wt%, and test the solution Zeta potential using an electrophoretic light scattering instrument.

[0104] The sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material: the sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material.

[0105] Thirdly, this application provides a battery 2, including the negative electrode 100 as described above. This battery has advantages corresponding to the negative electrode described above, which will not be repeated here.

[0106] In addition to the negative electrode 100, the battery 2 of this application also includes a separator, a positive electrode, and an electrolyte. The composition of the positive electrode can refer to conventional positive electrode sheets in the art, and the separator can also be a separator commonly used in the art, such as PP film, PE film, etc.

[0107] The battery 2 of this application can be prepared using conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and the cell can be obtained by stacking or winding. Then, the battery can be obtained by baking, liquid injection, formation and packaging.

[0108] Fourthly, this application provides a battery pack 3, as shown in FIG5, which includes the battery 2 as described above. This battery pack has advantages corresponding to the negative electrode 100 described above, which will not be repeated here.

[0109] Fifthly, this application provides an electrical device 4, as shown in FIG6, which includes the battery 2 as described above or the battery pack 3 as described above. This electrical device has advantages corresponding to the negative electrode 100 described above, which will not be elaborated further.

[0110] The electrical equipment 3 in this application can be a conventional electrical equipment in the field, including not only batteries but also controllers, transformers, motors, etc. Examples of electrical equipment include power equipment (such as electric vehicles), electronic equipment (such as computers, mobile phones, digital cameras, printers, fax machines, etc.), wearable devices (such as watches, wristbands, VR glasses, etc.), and home appliances (such as air conditioners, refrigerators, washing machines, microwave ovens, etc.), without particular limitation.

[0111] The technical solution of this application will be further described below with reference to specific embodiments.

[0112] Example 1

[0113] The method for preparing the negative electrode 100 in this embodiment includes the following steps:

[0114] Artificial graphite was selected as the negative electrode active material, with a D50 particle size of 8.70 μm and a specific surface area of ​​1.41 g / cm³. 3 The zeta potential is -42 mV. Carboxymethyl cellulose (CMC) is used as a dispersant with a degree of substitution of 0.92 and a zeta potential of -63 mV. The sum of the zeta potentials of the dispersant and the negative electrode active material is -105 mV. Commercially available styrene-butadiene rubber (SBR) and conductive carbon black are used as binders and conductive agents, respectively. The mass ratio of artificial graphite:CMC:SBR:conductive carbon black is 100:1.2:1.9:1.2.

[0115] First, CMC is dissolved in water to obtain a CMC dispersion. Then, artificial graphite and conductive carbon black powder are mixed evenly, and a portion of the CMC dispersion is added and kneaded. Next, the remaining dispersion is added, and an appropriate amount of water is added to dilute and stir until homogeneous. Finally, SBR is added and stirred evenly to obtain the negative electrode slurry.

[0116] The negative electrode slurry is coated onto both sides of a Cu foil using a coating machine. After drying, it is rolled to obtain a negative electrode sheet 100. The areal density of the negative electrode sheet is 172 g·m³. -2 The compacted density is 1.5 g·cm³. -3 The negative electrode includes a negative electrode active layer 120.

[0117] Example 2

[0118] The preparation method of the negative electrode sheet in Example 2 is basically the same as that in Example 1, except that the degree of substitution of the dispersant CMC is changed to 0.77.

[0119] Example 3

[0120] The preparation method of the negative electrode sheet in Example 3 is basically the same as that in Example 1, except that the degree of substitution of the dispersant CMC is changed to 0.89.

[0121] Example 4

[0122] The preparation method of the negative electrode sheet in Example 4 is basically the same as that in Example 1, except that the degree of substitution of the dispersant CMC is changed to 1.03.

[0123] Example 5

[0124] The preparation method of the negative electrode sheet in Example 5 is basically the same as that in Example 1, except that the type of dispersant is changed to PAA. PAA is obtained by polymerizing acrylonitrile, acrylamide and acrylic acid, wherein the molar ratio of acrylonitrile:acrylamide:acrylic acid is 58:13:32.

[0125] Example 6

[0126] The preparation method of the negative electrode sheet in Example 6 is basically the same as that in Example 1, except that the D50 particle size of the artificial graphite active material is changed to 11.31 μm and the specific surface area is changed to 0.76 g / cm³. 3 .

[0127] Example 7

[0128] The preparation method of the negative electrode sheet in Example 7 is basically the same as that in Example 1, except that the D50 particle size of the artificial graphite active material is changed to 13.55 μm and the specific surface area is changed to 1.30 g / cm³. 3 .

[0129] Example 8

[0130] The preparation method of the negative electrode sheet in Example 8 is basically the same as that in Example 1, except that the D50 particle size of the artificial graphite active material is changed to 11.50 μm and the specific surface area is changed to 1.25 g / cm³. 3 .

[0131] Example 9

[0132] The preparation method of the negative electrode sheet in Example 9 is basically the same as that in Example 1, except that the D50 particle size of the artificial graphite active material is changed to 11.34 μm and the specific surface area is changed to 1.32 g / cm³. 3 .

[0133] Example 10

[0134] The preparation method of the negative electrode sheet in Example 10 is basically the same as that in Example 1, except that the negative electrode active material is changed to natural graphite with a D50 particle size of 10.79 μm and a specific surface area of ​​3.23 g / cm³. 3 .

[0135] Example 11

[0136] The preparation method of the negative electrode sheet in Example 11 is basically the same as that in Example 1, except that the negative electrode active material is changed to hard carbon, with a D50 particle size of 6.96 μm and a specific surface area of ​​3.58 g / cm³. 3 .

[0137] Example 12

[0138] The preparation methods of the negative electrode sheet in Example 12 and Example 7 are basically the same, except that the degree of substitution of the dispersant CMC is changed to 0.77.

[0139] Example 13

[0140] The preparation methods of the negative electrode sheet in Example 13 and Example 9 are basically the same, except that the degree of substitution of the dispersant CMC is changed to 1.03.

[0141] Example 14

[0142] The preparation methods of the negative electrode sheet in Example 14 and Example 9 are basically the same, except that the degree of substitution of the dispersant CMC is changed to 0.68.

[0143] Example 15

[0144] The preparation methods of the negative electrode sheet in Example 15 and Example 10 are basically the same, except that the degree of substitution of the dispersant CMC is changed to 1.03.

[0145] Comparative Example 1

[0146] The preparation method of the negative electrode sheet of Comparative Example 1 is basically the same as that of Example 1, except that the degree of substitution of the dispersant CMC is changed to 0.68.

[0147] Comparative Example 2

[0148] The preparation methods of the negative electrode sheets in Comparative Example 2 and Example 6 are basically the same, except that the degree of substitution of the dispersant CMC is changed to 0.68.

[0149] Comparative Example 3

[0150] The preparation methods of the negative electrode sheets in Comparative Example 3 and Example 5 are basically the same, except that the negative electrode active material is changed to hard carbon, with a D50 particle size of 6.96 μm and a specific surface area of ​​3.58 g / cm³. 3 .

[0151] Experimental example:

[0152] 1. Observation of the appearance of the negative electrode: Place the negative electrode under strong light and observe whether there are black spots, dark scratches, cracks or other defects on the surface.

[0153] 2. Lithium Plasma Kinetics Test: Ten discs were cut from the same negative electrode sheet and assembled into coin-type lithium-ion batteries with lithium metal sheets. The batteries were discharged at 3C to 0.01V, then charged at 1C to 2V, cycled 20 times, and then discharged again at 3C to 0.01V. Subsequently, the batteries were disassembled to observe the lithium plating on the surface of each negative electrode disc, and the number of discs with different degrees of lithium plating was counted. Discs with less than 5% lithium plating were classified as having slight lithium plating, 5%–30% as having moderate lithium plating, and more than 30% as having severe lithium plating.

[0154] 3. Zeta potential of negative electrode active layer: After scraping off the negative electrode active layer from the negative electrode sheet, mix it with water at a mass ratio of 1:200, and ultrasonically disperse it for 30 minutes to form a solution. The zeta potential of the solution is then tested using an electrophoretic light scattering instrument.

[0155] Figure 1 shows the Zeta potential test spectrum of the negative electrode active material in Example 1. From the figure, it can be seen that the Zeta potential of the negative electrode active material is -42mV.

[0156] Figure 2 shows the Zeta potential test spectrum of the negative electrode active material in Example 8. From the figure, it can be seen that the Zeta potential of the negative electrode active material is -54mV.

[0157] Figure 3 shows the Zeta potential test spectrum of the negative electrode active material in Comparative Example 2. From the figure, it can be seen that the Zeta potential of the negative electrode active material is -27mV.

[0158] In Figures 1, 2, and 3, the horizontal axis represents Zeta Potential, and the vertical axis represents Intensity.

[0159] Table 1

[0160] As shown in Table 1, compared with the comparative example, the negative electrode sheet provided in this application can enhance the electrostatic repulsion between particles by limiting the Zeta potential of the negative electrode active layer to less than or equal to -53mV, prevent particle aggregation, improve the dispersion uniformity and stability of the negative electrode active material in the negative electrode sheet, avoid the appearance of black spots or dark lines on the negative electrode sheet, and reduce the risk of local lithium plating during battery charging.

[0161] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A negative electrode (100), characterized in that, The negative electrode (100) includes a negative electrode active layer (120), the zeta potential of which is less than or equal to -53mV.

2. The negative electrode (100) according to claim 1, characterized in that, The zeta potential of the negative electrode active layer (120) is -75mV to -63mV.

3. The negative electrode (100) according to claim 1 or 2, characterized in that, The negative electrode active layer (120) includes a negative electrode active material and a dispersant, wherein the sum of the zeta potential of the dispersant and the zeta potential of the negative electrode active material is -125mV to -90mV.

4. The negative electrode sheet (100) according to claim 3, characterized in that, The sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV.

5. The negative electrode (100) according to claim 3 or 4, characterized in that, The zeta potential of the negative electrode active material is less than or equal to -33mV.

6. The negative electrode (100) according to any one of claims 3-5, characterized in that, The zeta potential of the negative electrode active material is -55mV to -40mV.

7. The negative electrode (100) according to any one of claims 3-6, characterized in that, The zeta potential of the dispersant is less than or equal to -50mV.

8. The negative electrode (100) according to any one of claims 3-7, characterized in that, The zeta potential of the dispersant is -70mV to -58mV.

9. The negative electrode sheet according to any one of claims 3-8, characterized in that, The negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, mesophase carbon microspheres, silicon dioxide, and silicon-carbon. And / or, the D50 particle size of the negative electrode active material is 6.5 μm to 14 μm; And / or, the specific surface area of ​​the negative electrode active material is 0.5 g / cm³. 3 ~4g / cm 3 .

10. The negative electrode (100) according to any one of claims 3-9, characterized in that, The dispersant includes at least one of carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan; And / or, the degree of substitution of the dispersant is 0.5 to 1.

1.

11. The negative electrode (100) according to any one of claims 1-10, characterized in that, The negative electrode active layer (120) also includes a binder and a conductive agent.

12. A method for preparing the negative electrode sheet (100) according to any one of claims 1-11, characterized in that, Includes the following steps: A negative electrode slurry comprising a negative electrode active material, dispersant, conductive agent, binder and solvent is coated onto a negative electrode current collector (110), dried and rolled to form a negative electrode active layer (120) with a zeta potential less than or equal to -53mV, thereby obtaining the negative electrode sheet (100).

13. The method for preparing the negative electrode (100) according to claim 12, characterized in that, The sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -125mV to -90mV; And / or, the Zeta potential of the negative electrode active material is less than or equal to -33mV; And / or, the Zeta potential of the dispersant is less than or equal to -50mV.

14. The method for preparing the negative electrode sheet (100) according to claim 12 or 13, characterized in that, The sum of the Zeta potential of the dispersant and the Zeta potential of the negative electrode active material is -112mV to -100mV; And / or, the Zeta potential of the negative electrode active material is -55mV to -40mV; And / or, the Zeta potential of the dispersant is -70mV to -58mV.

15. A battery (2), characterized in that, The negative electrode (100) includes the negative electrode (100) as described in any one of claims 1-11 or the negative electrode (100) as described in any one of claims 12-14.

16. A battery pack (3), characterized in that, Includes the battery (2) as described in claim 15.

17. An electrical appliance (4), characterized in that, Includes the battery (2) of claim 15 or the battery pack (3) of claim 16.

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