A negative electrode sheet, a method for manufacturing the negative electrode sheet, a battery, a battery pack, and an electrical device

Abstract

This application relates to the field of negative electrode technology, and provides a negative electrode, a method for preparing the negative electrode, a battery, a battery pack, and an electrical device. The negative electrode includes a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer has a porous structure. The physical specific surface area (SSA) of the negative active material layer is compared with the electrochemical specific surface area (C) of the negative electrode. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g. This can solve the problem of poor electrode kinetics in graphite-containing negative electrode active material layers, leading to lower initial efficiency, specific capacity, and 1C capacity retention in the battery.

Description

Technical Field

[0001] This application relates to the field of negative electrode technology, specifically to a negative electrode, a method for preparing the negative electrode, a battery, a battery pack, and an electrical device. Background Technology

[0002] A battery is a device that directly converts chemical energy into electrical energy and is widely used in various electronic devices, vehicles, energy storage systems and other fields.

[0003] A battery has a positive electrode and a negative electrode. During discharge, the positive electrode is where electrons flow into the battery, and the negative electrode is where electrons flow out of the battery. The negative electrode includes a layer of graphite-containing negative electrode active material.

[0004] In related technologies, graphite-containing negative electrode active material layers have poor electrode kinetic performance, resulting in lower initial efficiency, specific capacity, and 1C capacity retention of the battery. Summary of the Invention

[0005] This application provides a negative electrode sheet, a method for preparing the negative electrode sheet, a battery, a battery pack, and an electrical device, which can solve the problem that the negative electrode active material layer containing graphite has poor electrode dynamic performance, resulting in low initial efficiency, specific capacity, and 1C capacity retention of the battery.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a negative electrode sheet, including a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer has a porous structure.

[0008] The physical specific surface area SSA of the negative electrode active material layer and the electrochemical specific surface area Cdl of the negative electrode sheet satisfy the following relationship: 8 < C dl / SSA < 35, SSA units are in meters 2 / g, Cdl is in mF / g.

[0009] In some embodiments, the physical specific surface area (SSA) of the negative electrode active material layer satisfies: 0.5 m² / s². 2 / g<SSA<3m 2 / g.

[0010] In some embodiments, the electrochemical specific surface area Cdl of the negative electrode sheet satisfies: 4mF / g < Cdl < 100mF / g.

[0011] In some embodiments, the negative electrode active material layer includes a binder, and the mass ratio of the carbon-based active material in the negative electrode active material layer to the binder is 100:(2-8);

[0012] And / or, the negative electrode active material layer also includes a conductive agent, and the mass ratio of carbon-based active material to conductive agent in the negative electrode active material layer is 100:(0.5~1.5).

[0013] In some embodiments, the carbon-based active material includes one or a combination of two of artificial graphite and natural graphite.

[0014] In some embodiments, the conductive agent includes one or more of acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.

[0015] In some embodiments, the adhesive includes one or more of the following: polytetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers, polyethers and their copolymers, polyphenylene ethers and their copolymers, polysiloxanes and their copolymers, polyesters and their copolymers, polyethylene oxide, polyethylene glycol block copolymers, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber, polyethylene ester, polyvinyl acetate, and polyacrylate.

[0016] And / or, the adhesive includes one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0017] In some embodiments, the areal density of the negative electrode sheet is 160 g / m². 2 -240 g / m 2 ;

[0018] And / or, the compaction density of the negative electrode sheet is 1.4 g / cc-1.65 g / cc.

[0019] Secondly, this application provides a method for preparing a negative electrode sheet, comprising the following steps:

[0020] The negative electrode active material is coated onto the negative electrode current collector to form a negative electrode active material layer connected to the negative electrode current collector;

[0021] Compact the negative electrode current collector and the negative electrode active material layer to obtain the negative electrode sheet;

[0022] The physical specific surface area SSA of the negative electrode active material layer, and the electrochemical specific surface area C of the negative electrode sheet. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g.

[0023] In some implementations, the following steps are also included:

[0024] The carbon-based active material, binder, conductive agent, and solvent are mixed and stirred evenly to obtain a slurry;

[0025] The slurry is dried and granulated into powder to form the negative electrode active material.

[0026] In some embodiments, the mass ratio of carbon-based active material to binder is 100:(2-8);

[0027] And / or, the mass ratio of carbon-based active material to conductive agent is 100:(0.5~1.5);

[0028] And / or, the mass ratio of carbon-based active material to solvent is 100:(100-120).

[0029] In some embodiments, the particle size of the powder ranges from 20 μm to 120 μm.

[0030] In some implementations, the slurry is dried by spray drying.

[0031] In some embodiments, the air inlet rate for spray drying is 50 mL / h to 5000 mL / h;

[0032] And / or, the inlet air temperature for spray drying is 30℃~300℃;

[0033] And / or, the outlet air temperature of the spray dryer is 30℃~140℃.

[0034] In some implementations, compaction may be either hot pressing or cold pressing.

[0035] In some embodiments, the pressure of hot pressing is 0.2T to 2T;

[0036] And / or, the hot pressing temperature is 100℃~250℃.

[0037] Thirdly, this application provides a battery including a negative electrode.

[0038] Fourthly, this application provides a battery pack, including a battery.

[0039] Fifthly, this application provides an electrical device including a battery pack.

[0040] This negative electrode structure, by incorporating a negative current collector, collects and conducts electrons from the negative electrode active material layer to the external circuit, thus enabling the battery's current output. The porous structure of the negative electrode active material layer allows the battery's electrolyte to permeate into its pores, increasing the rate and efficiency of the electrochemical reaction. Furthermore, the porous structure facilitates the penetration and diffusion of electrolyte ions into the negative electrode active material layer, enhancing ion transport rates and improving the battery's rapid charge and discharge rates. The physical specific surface area (SSA) of the negative electrode active material layer is related to the electrochemical specific surface area (C) of the negative electrode. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g, which can improve the kinetic mass transfer capability of the negative electrode sheet, and can also improve the first efficiency, specific capacity and 1C capacity retention of the battery.

[0041] Therefore, the negative electrode sheet provided in this application can solve the problem of poor electrode dynamics performance in the negative electrode active material layer, which leads to low initial efficiency, specific capacity and 1C capacity retention of the battery. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A schematic diagram of the main structure of the negative electrode sheet provided in the embodiments of this application;

[0044] Figure 2 Cyclic voltammetry (CV) curves of the negative electrode provided in this application embodiment at scan rates of 10mV / s, 40mV / s, 80mV / s, 120mV / s, 160mV / s, and 200mV / s;

[0045] Figure 3 Linear graphs of the current density difference at 0V versus the scan rate at scan rates of 10mV / s, 40mV / s, 80mV / s, 120mV / s, 160mV / s, and 200mV / s for the negative electrode provided in the embodiments of this application;

[0046] Figure 4 SEM image of the negative electrode sheet provided in the embodiments of this application;

[0047] Figure 5 SEM image of a negative electrode sheet processed by traditional wet process.

[0048] Explanation of reference numerals in the attached figures:

[0049] 100-Negative current collector;

[0050] 200 - Negative electrode active material layer. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. 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. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0052] In existing technologies, the negative electrode of a battery includes a negative current collector and a layer of negative active material disposed on the current collector. Different physical specific surface areas of the negative active material layer lead to different electrochemical performance of the negative electrode. Typically, the physical specific surface area of ​​the negative active material layer cannot be directly used to control the battery's initial efficiency, specific capacity, and rate performance. The fundamental reason is that the physical specific surface area of ​​the negative active material layer is determined solely by its microstructure and pore structure. In actual battery use, not all of the specific surface area participates in the energy storage process.

[0053] The physical specific surface area of ​​the negative electrode active material layer refers to the ratio of the total surface area of ​​the negative electrode active material layer to its mass or volume.

[0054] It should be noted that the battery's first efficiency refers to the battery's performance during the first charge-discharge cycle, especially the ratio of the first charge capacity to the first discharge capacity.

[0055] It should be noted that the specific capacity of a battery refers to the electrical energy that can be stored per unit mass of active material.

[0056] It should be noted that the electrochemical specific surface area of ​​the negative electrode refers to the specific surface area of ​​the negative electrode that actually participates in the electrochemical reaction.

[0057] To overcome the shortcomings of existing technologies, a negative electrode current collector is incorporated to collect and conduct electrons from the negative electrode active material layer in the negative electrode sheet to the external circuit, thereby completing the battery's current output. By incorporating a porous negative electrode active material layer, the battery's electrolyte can permeate into the pores of the layer, thus improving the rate and efficiency of the electrochemical reaction. Furthermore, the porous structure allows electrolyte ions to more easily penetrate and diffuse into the negative electrode active material layer, thereby increasing the ion transport rate and improving the battery's rapid charge and discharge rate. The physical specific surface area SSA of the negative electrode active material layer and the electrochemical specific surface area Cdl of the negative electrode sheet satisfy the following relationship: 8 < Cdl. dl / SSA < 35, SSA units are in meters 2 The unit of Cdl is mF / g. It can improve the kinetic mass transfer capability of the negative electrode sheet and improve the first efficiency, specific capacity and 1C capacity retention of the battery.

[0058] Therefore, the negative electrode sheet provided in this application can solve the problem that the negative electrode active material layer containing carbon-based active material has poor electrode dynamic performance, resulting in low initial efficiency, specific capacity and 1C capacity retention of the battery.

[0059] The contents of this application will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can have a clearer and more detailed understanding of the contents of this application.

[0060] The specific structure of the negative electrode and various possible implementation methods are described in detail below.

[0061] like Figure 1 As shown, an embodiment of this application provides a negative electrode sheet, including a negative electrode current collector 100 and a negative electrode active material layer 200 disposed on the negative electrode current collector 100. The negative electrode active material layer 200 has a porous structure; the physical specific surface area SSA of the negative electrode active material layer 200 is related to the electrochemical specific surface area C of the negative electrode sheet. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g.

[0062] It should be noted that if the physical specific surface area SSA of the negative electrode active material layer 200 is different from the electrochemical specific surface area C of the negative electrode sheet... dl The following condition must be met: 8 < C dl / SSA will result in lower initial efficiency, specific capacity and 1C capacity retention of the battery.

[0063] It should be noted that if the physical specific surface area SSA of the negative electrode active material layer 200 is different from the electrochemical specific surface area C of the negative electrode sheet...dl The following conditions must be met between them: C dl / SSA < 35 will result in low initial efficiency, specific capacity and 1C capacity retention of the battery.

[0064] It is understandable that the physical specific surface area SSA of the negative electrode active material layer 200 is similar to the electrochemical specific surface area C of the negative electrode sheet. dl The following condition must be met: 8 < C dl / SSA < 35 can improve the battery's initial efficiency, specific capacity, and 1C capacity retention.

[0065] It should be noted that the physical specific surface area SSA of the negative electrode active material layer 200 is different from the electrochemical specific surface area C of the negative electrode sheet. dl The ratio C between them dl / SSA can be 9, 12, 15, 18, 21, 23, 26, 29, 31, 33 or other values ​​in the range of 8 to 35. There are no restrictions here, and you can select according to the actual needs of use.

[0066] Understandably, C dl A value of / SSA of 9, 12, 15, 18, 21, 23, 26, 29, 31, 33 or other values ​​in the range of 8 to 35 can improve the battery's initial efficiency, specific capacity and 1C capacity retention.

[0067] The physical specific surface area (SSA) of the negative electrode active material layer 200 can be measured using the N2 adsorption-desorption BET method or the mercury porosimetry method.

[0068] It should be noted that the N2 adsorption-desorption BET method is as follows: the negative electrode active material layer 200 on the negative electrode sheet is scraped off from the negative electrode current collector 100, placed in a sealed container, and nitrogen gas is introduced at a low temperature (usually liquid nitrogen temperature, about 77K). The pressure of the nitrogen gas is gradually increased, and the adsorption amount of the negative electrode active material layer 200 at each pressure is measured. Adsorption isotherms are plotted, and then the adsorption isotherms are linearly fitted using the Brownian-Hermet-Taylor equation (i.e., the BET equation). The physical specific surface area is then calculated from the monolayer adsorption amount obtained from the fitting.

[0069] It should be noted that the mercury intrusion porosimetry method is as follows: the negative electrode active material layer 200 on the negative electrode sheet is scraped off from the negative electrode current collector 100 and placed into the mercury intrusion porosimetry instrument. The pressure is gradually increased, and the volume of mercury entering the sample is recorded. Based on the applied pressure and the change in mercury volume, the physical specific surface area is calculated using the Washburn equation.

[0070] It should be noted that the electrochemical specific surface area C of the negative electrode plate dl The measurement can be performed using cyclic voltammetry (CV method).

[0071] It should be noted that the above negative electrode sheet was cut into negative electrode sheet samples of 43mm×56mm, and a symmetrical cell was assembled using a 14μm thick polypropylene (PP) separator and electrolyte (i.e., a symmetrical cell composed of two identical above negative electrode sheet samples as working electrode and counter electrode).

[0072] Furthermore, the electrolyte is prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), diethyl carbonate (DEC), and diethyl carbonate (DEC) in a mass ratio of 12:26:60:2.

[0073] Furthermore, the electrochemical specific surface area of ​​the negative electrode used in the test was calculated by cyclic voltammetry (CV) using an electrochemical workstation.

[0074] The CV test scan rates were 10 mV / s, 40 mV / s, 80 mV / s, 120 mV / s, 160 mV / s, and 200 mV / s, with a voltage range of -0.1 to 0.1 V. CV curves were measured at different scan rates, and the current density at 0 V was statistically analyzed. The difference between the oxidation and reduction current densities was calculated, and a linear relationship between the current density difference j and the scan rate v was fitted. The slope of this linear relationship represents the electrochemical specific surface area of ​​the negative electrode.

[0075] The physical specific surface area SSA of the negative electrode active material layer 200 provided in the embodiments of this application satisfies: 0.5m². 2 / g<SSA<3m 2 / g.

[0076] It should be noted that the physical specific surface area SSA of the negative electrode active material layer 200 satisfies: 0.5m². 2 / g<SSA<3m 2 / g can improve the battery's initial efficiency, specific capacity, and 1C capacity retention.

[0077] It should be noted that the physical specific surface area SSA of the negative electrode active material layer 200 can be 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, or any value between 0.5 and 3. There are no restrictions here, and it can be selected according to the actual use requirements.

[0078] It is understandable that the physical specific surface area SSA of the negative electrode active material layer 200 can be 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, or any value between 0.5 and 3, which can improve the battery's initial efficiency, specific capacity, and 1C capacity retention rate.

[0079] The electrochemical specific surface area C of the negative electrode provided in the embodiments of this application dlSatisfy: 4mF / g < C dl <100mF / g.

[0080] It is understandable that the electrochemical specific surface area C of the negative electrode plate... dl Satisfy: 4mF / g < C dl A value of <100mF / g can improve the rate performance of the battery and increase its energy density. In addition, it can reduce the occurrence of battery structural collapse or material loss, thereby improving the battery's stability, and can also improve the battery's initial efficiency, specific capacity, and 1C capacity retention rate.

[0081] It should be noted that the electrochemical specific surface area C of the negative electrode plate dl The value can be 10, 40, 60, 80, 100 or any value between 4 and 1020. There are no restrictions here, and you can choose according to the actual use needs.

[0082] It is understandable that the electrochemical specific surface area C of the negative electrode plate... dl The value can be 10, 40, 60, 80, 100 or any value between 4 and 100. It can improve the rate performance of the battery and increase the energy density of the battery. In addition, it can reduce the occurrence of battery structure collapse or material loss, thereby improving the stability of the battery. It can also improve the battery's first efficiency, specific capacity and 1C capacity retention rate.

[0083] The negative electrode active material layer 200 provided in the embodiments of this application includes: carbon-based active material, binder and / or conductive agent.

[0084] Understandably, by setting up carbon-based active materials, the layered structure of the carbon-based active materials allows lithium ions to be inserted and extracted during charging and discharging, thereby realizing the energy storage and release of the battery.

[0085] Understandably, by using a binder, the carbon-based active material and / or conductive agent in the negative electrode active material layer 200 can be tightly bonded to the negative electrode current collector 100 to form a stable negative electrode sheet. Furthermore, the binder can improve the detachment and pulverization of the carbon-based active material and conductive agent, thereby increasing the cycle life of the battery.

[0086] It is understandable that by adding a conductive agent, the conductivity of the negative electrode can be improved. The conductive agent forms a conductive network, ensuring the effective transport of electrons in the electrode material, thereby optimizing the overall performance of the battery.

[0087] It should be noted that the carbon-based active material, binder and / or conductive agent provided in the embodiments of this application have a variety of different mass ratios. The mass ratios between the carbon-based active material, binder and conductive agent are illustrated below.

[0088] In one feasible implementation, the negative electrode active material layer 200 provided in the embodiments of this application further includes a binder, and the mass ratio of the carbon-based active material in the negative electrode active material layer 200 to the binder is 100:(2-8).

[0089] It is understandable that the mass ratio of carbon-based active material to binder in the negative electrode active material layer 200 is 100:(2~8), which can improve the connection strength between the negative electrode active material layer 200 and the negative electrode current collector 100, and can improve the space occupation of the binder, thereby reducing the internal resistance of the negative electrode sheet. In addition, it can improve the energy density of the battery after the negative electrode sheet is formed into a battery.

[0090] In another feasible implementation, the negative electrode active material layer 200 provided in the embodiments of this application further includes a conductive agent, and the mass ratio of carbon-based active material to conductive agent in the negative electrode active material layer 200 is 100:(0.5~1.5).

[0091] It is understandable that the negative electrode active material layer 200 also includes a conductive agent. The mass ratio of carbon-based active material to conductive agent in the negative electrode active material layer 200 is 100:(0.5~1.5), which can improve the conductivity of the negative electrode sheet and thus improve the overall performance of the battery.

[0092] In addition, in other feasible embodiments, the negative electrode active material layer 200 provided in the embodiments of this application further includes a binder and a conductive agent, and the mass ratio of carbon-based active material, binder and conductive agent in the negative electrode active material layer 200 is 100:(2~8):(0.5~1.5).

[0093] It is understandable that the mass ratio of carbon-based active material, binder, and conductive agent in the negative electrode active material layer 200 is 100:(2-8):(0.5-1.5). This can improve the connection strength between the negative electrode active material layer 200 and the negative electrode current collector 100, and reduce the internal resistance of the negative electrode sheet. Furthermore, it can increase the energy density of the battery after the negative electrode sheet is formed. It can also improve the conductivity of the negative electrode sheet, thereby improving the overall performance of the battery.

[0094] Understandably, there are no restrictions on the specific mass ratio of carbon-based active materials, binders, and conductive agents; the ratio can be selected based on actual usage requirements.

[0095] The carbon-based active materials provided in the embodiments of this application include one or a combination of two of artificial graphite and natural graphite.

[0096] It should be noted that carbon-based active materials include one or a combination of artificial graphite and natural graphite, which can improve the conductivity of the negative electrode active material layer 200. Furthermore, carbon-based active materials can affect the wettability of the electrolyte in the battery, thereby increasing the ion transport rate of the battery and improving the charge and discharge performance of the battery.

[0097] The conductive agents provided in the embodiments of this application include one or more of acetylene black, Ketjen black, superconducting carbon black (i.e., Super-P), carbon nanotubes, carbon nanofibers, activated carbon, and graphene.

[0098] It should be noted that the conductive agent includes one or more of acetylene black, Ketjen black, superconducting carbon black (Super-P), carbon nanotubes, carbon nanofibers, activated carbon, and graphene, which can effectively improve the overall electron transport capability of the negative electrode sheet and reduce the internal resistance of the battery, thereby increasing the power density of the battery.

[0099] The adhesives provided in the embodiments of this application have a variety of different configuration methods, which will be illustrated below with examples.

[0100] In one feasible embodiment, the adhesive includes one or more of the following: polytetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers, polyethers and their copolymers, polyphenylene ethers and their copolymers, polysiloxanes and their copolymers, polyesters and their copolymers, polyethylene oxide, polyethylene glycol block copolymers, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber, polyethylene ester, polyvinyl acetate, and polyacrylate.

[0101] It should be noted that polyolefins include one or more of polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / vinylidene fluoride copolymer, and propylene / vinylidene fluoride copolymer; polytetrafluoroethylene and its copolymers may be one or more of tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / ether copolymer, tetrafluoroethylene / siloxane copolymer, tetrafluoroethylene / branched polyether copolymer, tetrafluoroethylene / vinyl ether copolymer, and tetrafluoroethylene / branched polyether / vinyl ether copolymer.

[0102] It is understandable that the binder, using the aforementioned materials, can effectively bond the carbon-based active material and the conductive agent together and connect them to the negative electrode current collector 100 to form a stable negative electrode sheet. It can also alleviate the volume change of the negative electrode sheet during charging and discharging, thereby improving the occurrence of cracking and delamination of the negative electrode sheet.

[0103] In another feasible implementation, the binder includes one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0104] Understandably, the binder, including one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber, can effectively bond the carbon-based active material and conductive agent together and connect them to the negative electrode current collector 100 to form a stable negative electrode sheet. It can also mitigate the volume changes of the negative electrode sheet during charging and discharging, thereby improving the occurrence of cracking and delamination of the negative electrode sheet. Sodium carboxymethyl cellulose and styrene-butadiene rubber can also be used as thickeners to improve the shedding and pulverization of carbon-based active materials and conductive agents, thereby increasing the cycle life of the battery.

[0105] In another feasible embodiment, the adhesive includes one or more of polytetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers, polyethers and their copolymers, polyphenylene ethers and their copolymers, polysiloxanes and their copolymers, polyesters and their copolymers, polyethylene oxide, polyethylene glycol block copolymers, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber, polyethylene ester, polyvinyl acetate, polyacrylate, and a mixture of one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0106] It is understandable that the binder, using the aforementioned materials, can effectively bond the carbon-based active material and conductive agent together and connect them to the negative electrode current collector 100 to form a stable negative electrode sheet. It can also alleviate the volume change of the negative electrode sheet during charging and discharging, thereby improving the occurrence of cracking and delamination of the negative electrode sheet. Furthermore, sodium carboxymethyl cellulose and styrene-butadiene rubber can be used as thickeners to improve the shedding and pulverization of carbon-based active materials and conductive agents, thereby improving the cycle life of the battery.

[0107] Understandably, there are no restrictions on the way the adhesive is applied; it can be selected according to actual usage requirements.

[0108] It should be noted that the areal density of the negative electrode sheet provided in the embodiments of this application is 160 g / m². 2 -240g / m 2 .

[0109] It is understandable that the areal density of the negative electrode sheet is 160 g / m². 2 -240 g / m 2 This can improve the energy density of the battery and help optimize the battery capacity.

[0110] It should be noted that the areal density of the negative electrode sheet can be obtained by cutting a rectangular sample from the negative electrode sheet, measuring the length and width of the rectangular sample using calipers or a laser measuring instrument, and then multiplying the length by the width to obtain the area of ​​the rectangular sample. The weight of the rectangular sample is then measured using a balance. The negative electrode sheet is then immersed in deionized water, rinsed to remove the surface dressing, and then dried. The weight of the negative electrode current collector 100 is measured. The weight of the negative electrode current collector 100 is then subtracted from the weight of the rectangular sample to obtain the weight of the negative electrode active material layer 200. Finally, the areal density of the negative electrode sheet is obtained by dividing the weight of the negative electrode active material layer 200 by its area.

[0111] It should be noted that the areal density of the negative electrode sheet provided in the embodiments of this application can be any value within the range of 160, 170, 180, 190, 200, 210, 220, 230, 240 or 160 to 240, and is not limited here. It can be selected according to actual usage requirements.

[0112] Understandably, setting the areal density of the negative electrode to the values ​​mentioned above can improve the energy density of the battery and help optimize its capacity.

[0113] The compaction density of the negative electrode sheet provided in the embodiments of this application is 1.4 g / cc-1.65 g / cc.

[0114] Understandably, a compaction density of 1.4 g / cc to 1.65 g / cc for the negative electrode sheet can give it better mechanical strength and structural integrity, enabling it to better maintain its shape and structure during charge and discharge cycles, and optimizing the shedding and pulverization of the negative electrode active material layer 200.

[0115] It should be noted that the areal density of the negative electrode sheet can be obtained by cutting a rectangular sample from the negative electrode sheet, measuring the length, width, and thickness of the rectangular sample using calipers or a laser measuring instrument, and then multiplying the length by the width to obtain the area of ​​the rectangular sample. The weight of the rectangular sample is then measured using a balance. The negative electrode sheet is then immersed in deionized water, rinsed to remove the surface dressing, and the negative electrode current collector 100 is dried and weighed. The weight of the negative electrode current collector 100 is then subtracted from the weight of the rectangular sample to obtain the weight of the negative electrode active material layer 200. Finally, the areal density of the negative electrode sheet is obtained by dividing the weight of the negative electrode active material layer 200 by its area.

[0116] Then, the thickness of the negative electrode current collector 100 is measured using a thickness gauge. The thickness of the negative electrode current collector 100 is subtracted from the thickness of the negative electrode sheet to obtain the thickness of the negative electrode active material layer 200. Then, the compaction density of the negative electrode sheet is obtained by dividing the areal density of the negative electrode sheet by the thickness of the negative electrode active material layer 200.

[0117] It should be noted that the compaction density of the negative electrode sheet provided in the embodiments of this application can be any value within the range of 1.4, 1.5, 1.6, 1.65 or 1.4 to 1.65, and is not limited here. It can be selected according to actual usage requirements.

[0118] It is understandable that the compaction density of the negative electrode sheet is as described above, which can make the negative electrode sheet have better mechanical strength and structural integrity, and can better maintain its shape and structure during charge and discharge cycles, thus optimizing the shedding and pulverization of the negative electrode active material layer 200.

[0119] Embodiments of this application provide a battery including the negative electrode sheet provided in any of the above embodiments.

[0120] Embodiments of this application provide a battery pack including the battery provided in any of the above embodiments.

[0121] The battery pack includes at least two batteries as described above that are interconnected, and the battery pack has advantages corresponding to the batteries described above, which will not be elaborated further.

[0122] Furthermore, the battery pack includes multiple of the aforementioned batteries, which are connected as individual cells to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a hybrid connection including these methods, without particular limitation.

[0123] This application also provides an electrical device, including an electrical appliance and a battery pack or battery as described in any of the above embodiments, wherein the battery pack is used to provide electrical energy to the electrical appliance.

[0124] The electrical equipment in this application embodiment can be a vehicle, such as a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle, and a new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. Accordingly, the electrical device can be the vehicle's drive mechanism or the vehicle's control system.

[0125] In addition, electrical equipment can also serve as other energy storage devices, such as mobile phones, portable devices, laptops, electric toys, power tools, ships, and spacecraft. Among these, spacecraft can include airplanes, rockets, space shuttles, or spacecraft.

[0126] Since the electrical device in this embodiment includes the battery described in any of the above embodiments, the electrical device includes the battery structure and beneficial effects, which will not be described in detail here.

[0127] The embodiments of this application provide a method for preparing a negative electrode sheet, applicable to the negative electrode sheet provided in any of the above embodiments. The method for preparing the negative electrode sheet includes the following steps:

[0128] The negative electrode active material layer 200 is coated on the negative electrode current collector 100;

[0129] Compact the negative electrode current collector 100 and the negative electrode active material layer 200 to obtain the negative electrode sheet;

[0130] The physical specific surface area SSA of the negative electrode active material layer 200 is compared with the electrochemical specific surface area C of the negative electrode sheet. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g.

[0131] It is understood that, through the above embodiments, a negative electrode sheet can be obtained by compacting the negative electrode current collector 100 and the negative electrode active material layer 200. Through the above embodiments, the physical specific surface area SSA of the negative electrode active material layer 200 can be made similar to the electrochemical specific surface area C of the negative electrode sheet. dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is expressed in mF / g, which allows the negative electrode to improve the battery's initial efficiency, specific capacity, and 1C capacity retention rate when forming the battery.

[0132] The method for preparing the negative electrode sheet, applied to the negative electrode sheet provided in any of the above embodiments, further includes the following steps:

[0133] The carbon-based active material, binder, conductive agent, and solvent are mixed and stirred evenly to obtain a slurry;

[0134] The slurry is dried and granulated into powder to form the negative electrode active material layer 200.

[0135] It is understood that the above-described embodiments can help to uniformly distribute carbon-based active materials, binders, and conductive agents, thereby improving the uniformity of the negative electrode active material layer 200.

[0136] In some embodiments, the carbon-based active material is graphite, the binder is sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber latex (SBR uniformly dispersed in water with a solid content of 40%), the conductive agent is carbon black, and the solvent is deionized water.

[0137] Furthermore, graphite, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber latex (SBR), carbon black, and deionized water are mixed in a mass ratio of 100:1.6:3.2:1:110 and stirred evenly to obtain a slurry.

[0138] In the above-mentioned method for preparing the negative electrode sheet, the mass ratio of carbon-based active material to binder (a combination of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber emulsion (SBR)) is 100:(2-8).

[0139] It is understood that, through the above-described embodiments, the layered structure of the carbon-based active material allows lithium ions to be inserted and extracted during charging and discharging, thereby achieving energy storage and release in the battery. Furthermore, it allows the carbon-based active material and / or conductive agent in the negative electrode active material layer 200 to be tightly bonded to the negative electrode current collector 100, forming a stable negative electrode sheet. The addition of a binder can improve the detachment and pulverization of the carbon-based active material and conductive agent, thereby increasing the battery's cycle life.

[0140] In the above method for preparing the negative electrode sheet, the mass ratio of carbon-based active material to conductive agent is 100:(0.5~1.5).

[0141] It is understandable that the above implementation method can improve the conductivity of the negative electrode sheet. The conductive agent, by forming a conductive network, ensures the effective transport of electrons in the electrode material, thereby optimizing the overall performance of the battery.

[0142] In the above method for preparing the negative electrode sheet, the mass ratio of carbon-based active material to solvent is 100:(100-120).

[0143] It is understood that the above-described embodiments can help to uniformly disperse carbon-based active materials, conductive agents and / or binders in the slurry to form a stable suspension.

[0144] In the above-mentioned method for preparing the negative electrode sheet, the particle size range of the mixed powder is 20μm to 120μm.

[0145] It is understandable that the microstructure of the negative electrode sheet can be optimized through the above implementation method, which helps to improve the conductivity and ion transport performance of the negative electrode sheet.

[0146] In the above-mentioned method for preparing the negative electrode sheet, the slurry is dried by spray drying.

[0147] Understandably, spray drying allows for more precise temperature control of the slurry during the drying process, reducing thermal degradation or chemical reactions caused by temperature fluctuations. This improves the mixing uniformity and electrochemical stability of the carbon-based active materials, conductive agents, and binders in the powder. Furthermore, it avoids the binder floating problem that occurs during the drying process in traditional wet coating processes.

[0148] In the above-mentioned method for preparing the negative electrode sheet, the air inlet rate for spray drying is 50 mL / h to 5000 mL / h.

[0149] It is understandable that the above-described implementation method allows for more effective control of the quality of the negative electrode active material during the spray drying process.

[0150] In the above-mentioned method for preparing the negative electrode sheet, the inlet air temperature for spray drying is 30℃~300℃.

[0151] It is understandable that the above-described implementation method allows for more effective control of the quality of the negative electrode active material during the spray drying process.

[0152] In the above-mentioned method for preparing the negative electrode sheet, the outlet air temperature of the spray drying is 30℃~140℃.

[0153] It is understandable that the above-described implementation method allows for more effective control of the quality of the negative electrode active material during the spray drying process.

[0154] In the above-mentioned method for preparing the negative electrode sheet, the compaction can be either hot pressing or cold pressing.

[0155] Understandably, the above-described implementation method enables the negative electrode sheet to possess better mechanical strength and structural integrity, better maintaining its shape and structure during charge-discharge cycles, and optimizing the shedding and pulverization of the negative electrode active material layer 200. Furthermore, the compacted electrode sheet reduces the electrode thickness, thereby reducing the battery volume and further improving energy density.

[0156] In the above-mentioned method for preparing the negative electrode sheet, the hot pressing pressure is 0.2T to 2T.

[0157] It is understandable that the above implementation method allows for more effective control of the quality of the negative electrode sheet during the hot pressing process.

[0158] In the above-mentioned method for preparing the negative electrode sheet, the hot pressing temperature is 100℃~250℃.

[0159] It is understandable that the above implementation method allows for more effective control of the quality of the negative electrode sheet during the hot pressing process.

[0160] In the above-mentioned method for preparing the negative electrode sheet, the cold pressing pressure is 5T-25T.

[0161] It is understandable that the above implementation method allows for more effective control of the compaction of the negative electrode sheet during the cold pressing process.

[0162] In the above-mentioned method for preparing the negative electrode sheet, the cold pressing temperature is room temperature (25°C).

[0163] It is understandable that the above implementation method allows for more effective control of the compaction of the negative electrode sheet during the cold pressing process.

[0164] The following is a detailed description of a negative electrode sheet provided by the present invention through specific embodiments.

[0165] Example 1

[0166] The method for preparing the negative electrode sheet in this embodiment includes the following steps:

[0167] (1) Mix graphite, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber latex (SBR), carbon black, and deionized water in a predetermined ratio and stir until homogeneous. By mass, the mass of graphite is 100 parts, sodium carboxymethyl cellulose (CMC) is 1.6 parts, styrene-butadiene rubber latex (SBR) is 3.2 parts, carbon black is 1 part, and deionized water is 110 parts.

[0168] (2) The mixed slurry is quickly dried by spray drying. The air inlet rate is set to 500 mL / h, the air inlet temperature is 100℃, and the air outlet temperature is 90℃. The spray drying parameters are adjusted, and at the same time, granulation is carried out to form a uniform powder with a particle size of 100 μm.

[0169] (3) The dried and granulated mixed powder is pressed onto the negative electrode current collector 100 by a hot roller. The hot roller pressure is 1T and the temperature is 150℃. After secondary compaction, the desired C is obtained. dl The negative electrode sheet has an SSA ratio and a surface density of 200 g / m³. 2 The compaction density of the negative electrode sheet is 1.5 g / cc.

[0170] Example 2

[0171] The difference between this embodiment and Embodiment 1 is that in step (1), the mass fraction of sodium carboxymethyl cellulose (CMC) is 1 part, the mass fraction of styrene-butadiene rubber latex (SBR) is 2 parts, the mass fraction of carbon black is 0.5 parts, and the mass fraction of deionized water is 100 parts.

[0172] Example 3

[0173] The difference between this embodiment and Embodiment 1 is that in step (1), the mass fraction of sodium carboxymethyl cellulose (CMC) is 2 parts, the mass fraction of styrene-butadiene rubber latex (SBR) is 4 parts, the mass fraction of carbon black is 1.5 parts, and the mass fraction of deionized water is 120 parts.

[0174] Example 4

[0175] The difference between this embodiment and Embodiment 1 is that in step (1), the mass fraction of sodium carboxymethyl cellulose (CMC) is 3 parts, the mass fraction of styrene-butadiene rubber latex (SBR) is 6 parts, the mass fraction of carbon black is 3 parts, and the mass fraction of deionized water is 140 parts.

[0176] Example 5

[0177] The difference between this embodiment and Embodiment 1 is that the areal density of the negative electrode sheet in step (3) is 160 g / m². 2 The compaction density of the negative electrode sheet is 1.4 g / cc.

[0178] Example 6

[0179] The difference between this embodiment and Embodiment 1 is that the areal density of the negative electrode sheet in step (3) is 240 g / m². 2 The compaction density of the negative electrode sheet is 1.65 g / cc.

[0180] Example 7

[0181] The difference between this embodiment and Embodiment 1 is that the areal density of the negative electrode sheet in step (3) is 300 g / m². 2 The compaction density of the negative electrode sheet is 2.1 g / cc.

[0182] Example 8

[0183] The difference between this embodiment and embodiment 1 is that the particle size of the powder in step (2) is 20 μm.

[0184] Example 9

[0185] The difference between this embodiment and Embodiment 1 is that the particle size of the powder in step (2) is 120 μm.

[0186] Example 10

[0187] The difference between this embodiment and Embodiment 1 is that the particle size of the powder in step (2) is 180 μm.

[0188] Example 11

[0189] The difference between this embodiment and embodiment 1 is that in step (2), the air intake rate of spray drying is 50 mL / h, the air intake temperature is 30°C, and the air outlet temperature is 30°C.

[0190] Example 12

[0191] The difference between this embodiment and embodiment 1 is that in step (2), the air intake rate of the spray drying is 5000 mL / h, the air intake temperature is 300℃, and the air outlet temperature is 140℃.

[0192] Example 13

[0193] The difference between this embodiment and embodiment 1 is that in step (2), the air intake rate of the spray drying is 6500 mL / h, the air intake temperature is 410℃, and the air outlet temperature is 185℃.

[0194] Example 14

[0195] The difference between this embodiment and embodiment 1 is that the pressure of the hot roller in step (3) is 0.2T and the temperature is 100℃.

[0196] Example 15

[0197] The difference between this embodiment and embodiment 1 is that the pressure of the hot roller in step (3) is 2T and the temperature is 250℃.

[0198] Example 16

[0199] The difference between this embodiment and embodiment 1 is that the pressure of the hot roller in step (3) is 2.7T and the temperature is 290℃.

[0200] Comparative Example 1

[0201] The negative electrode sheet in this comparative example is prepared using a traditional coating process, including the following steps:

[0202] (1) Mix graphite, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber latex (SBR uniformly dispersed in water with a solid content of 40%), carbon black, and deionized water in a predetermined ratio and stir until homogeneous. The mass fraction of graphite is 100 parts, the mass fraction of sodium carboxymethyl cellulose (CMC) is 1.6 parts, the mass fraction of styrene-butadiene rubber (SBR) is 3.2 parts, the mass fraction of carbon black is 1 part, and the mass fraction of deionized water is 110 parts.

[0203] (2) The uniformly mixed slurry is coated onto the negative current collector 100 (the same negative current collector 100 used in the example) by a coating machine to ensure that the surface density is the same as that of the negative electrode sheet in Example 1, and then dried in an oven at 105°C.

[0204] (3) Roll the dried negative electrode sheet to ensure that the compaction density is consistent with that of the negative electrode sheet in Example 1, and obtain the desired negative electrode sheet.

[0205] Comparative Example 2

[0206] The difference between this comparative example and comparative example 1 is that the drying temperature of the oven in step (2) is 130℃.

[0207] Comparative Example 3

[0208] The difference between this comparative example and Comparative Example 1 is that in step (1), the mass fraction of graphite is 100 parts, the mass fraction of sodium carboxymethyl cellulose (CMC) is 2 parts, the mass fraction of styrene-butadiene rubber latex (SBR) is 4 parts, the mass fraction of carbon black is 1.5 parts, and the mass fraction of deionized water is 120 parts.

[0209] Comparative Example 4

[0210] The difference between this comparative example and Comparative Example 1 is that in step (1), porous activated carbon (with a physical specific surface area of ​​1500 m²) is used as the carbon black. 2 / g, particle size 10~20μm), mass fraction is 1.5 parts.

[0211] Comparative Example 5

[0212] The difference between this comparative example and Comparative Example 1 is that in step (1), the mass fraction of sodium carboxymethyl cellulose (CMC) is 0.8 parts, the mass fraction of styrene-butadiene rubber latex (SBR) is 1.6 parts, and carbon black is carbon nanotubes (the physical specific surface area of ​​carbon nanotubes is 400 m²). 2 / g, length-to-diameter ratio 200:1), with a mass fraction of 1.5 parts.

[0213] Taking Example 1 as an example, the assembled symmetrical battery was tested using cyclic voltammetry (CV method) with an electrochemical workstation, and the electrochemical specific surface area of ​​the negative electrode sample used in Example 1 was calculated. The specific testing and calculation process is as follows:

[0214] The CV test scan rates were 10mV / s, 40mV / s, 80mV / s, 120mV / s, 160mV / s, and 200mV / s, with a voltage range of -0.1 to 0.1V. The CV curves at different scan rates are shown below. Figure 2 As shown, voltage refers to voltage in volts (V), and current density refers to current density in mA / m². 2 The SACN rate refers to the scanning rate, which is 10-200 mV / s.

[0215] For further information, please refer to [link / reference]. Figure 2 Along the vertical axis of the coordinate system, with current densities ranging from 0 to 1500 mA / m 2In the direction shown, the CV curves are displayed sequentially at scan rates of 10mV / s, 40mV / s, 80mV / s, 120mV / s, 160mV / s, and 200mV / s, along the vertical axis of the coordinate system, with current densities ranging from 0 to -1500mA / m. 2 In the direction shown, the CV curves are displayed sequentially at scan rates of 10mV / s, 40mV / s, 80mV / s, 120mV / s, 160mV / s, and 200mV / s.

[0216] The current density at 0V is statistically analyzed, the difference between the oxidation and reduction current densities is calculated, and a linear relationship between the current density difference j and the scan rate v is fitted, as shown below. Figure 3 As shown, its slope is 29.37 mF / g, which is the electrochemical specific surface area of ​​the negative electrode sheet in Example 1.

[0217] Furthermore, the electrochemical specific surface area of ​​the negative electrode sheet was obtained using the same method in Examples 2 to 16 and Comparative Examples 1 to 3, and will not be described in detail here.

[0218] The negative electrode sheets of the above embodiments and comparative examples were cut into slices using a slicer. Electrode sheets were weighed and their mass recorded. Battery assembly was completed in an argon-filled glove box (oxygen content <0.1ppm, water vapor content <0.1ppm), using a CR2016 coin cell. The negative electrode shell, negative electrode sheet, separator (polyethylene / polypropylene composite membrane), lithium metal sheet, nickel foam, and positive electrode cap were stacked and assembled sequentially. Appropriate amounts of electrolyte were dripped onto both sides of the separator. Finally, a hydraulic sealing machine was used to seal the assembly, completing the battery assembly for testing.

[0219] It should be noted that the electrolyte is prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), diethyl carbonate (DEC), and diethyl carbonate (DEC) in a mass ratio of 12:26:60:2.

[0220] Electrode first efficiency, specific capacity, and 1C capacity retention were obtained using the following test methods.

[0221] Battery initial efficiency and specific capacity tests: The assembled batteries were tested in the Blue Battery Test Cabinet. Constant current discharge was performed continuously at 0.1C / 0.05C / 0.01C to 0.005V (the graphite lithium intercalation process in coin cells). After resting for 10 minutes, the batteries were then continuously charged continuously at 0.1C / 0.05C / 0.01C to 1.5V. The charging and discharging capacities C were recorded. 充 and C 放 Electrode first effect = C 充 / C 放 Mass of active material in the electrode (M) 活) represents the mass of graphite, and the electrode specific capacity = C 放 / M 活

[0222] 1C Capacity Retention Rate Test: The discharge capacity of each battery was tested at different discharge rates (0.1C, 0.33C, 0.5C, and 1C) at 25℃, with a voltage range of 0.005V-1.5V. The ratio of the discharge capacity at 1C to that at 0.1C is the 1C capacity retention rate.

[0223] The physical specific surface area of ​​the negative electrode active material layer 200 was obtained according to the following test method.

[0224] After obtaining the finished battery, the clean negative electrode sheet is obtained by disassembly and cleaning. The negative electrode active material layer 200 on the negative electrode current collector 100 is scraped off with a utility knife and dispersed in water. After centrifugation at 6000 rpm, the sediment is removed, washed 6 times, and baked to obtain the negative electrode active material layer 200. A certain mass of the negative electrode active material layer 200 is weighed and placed in a specific surface area analyzer (model TristarII3020). The physical specific surface area of ​​the negative electrode active material layer 200 is tested according to the national standard GB / T19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0225] The proportions of the above materials are shown in Table 1.

[0226] Table 1

[0227]

[0228] The above preparation process is shown in Table 2.

[0229] Table 2

[0230]

[0231] The test results are shown in Table 3.

[0232] Table 3

[0233]

[0234] As shown in Tables 1, 2, and 3, please refer to the following for further information. Figure 4 and Figure 5 Compared to the traditional wet process in Examples 1-3, the battery's initial efficiency is better, but its C... dl The SSA remains below 8, indicating a low 1C capacity retention rate, meaning the electrode's kinetic performance is flawed. (Comparative Examples 4-5 show the negative electrode C...) dlWith an SSA value above 35, the initial efficiency, specific capacity, and 1C capacity retention are all relatively low. However, the negative electrode sheets prepared in Examples 1 to 16 of this application, compared to Comparative Examples 1 to 5, show a significant improvement in initial efficiency and specific capacity, and a superior 1C capacity retention. This is mainly due to the negative electrode sheet preparation method of this application, which, under suitable parameter conditions, achieves rapid and uniform drying, avoids the uneven distribution problem caused by binder floating in traditional coating processes, has good conductivity, and a superior ion pathway, thereby enabling control of C... dl / SSA meets performance requirements. Furthermore, when the negative electrode C... dl When both SSA are controlled within the range more recommended in the embodiments of this application (Examples 1, 2, 3, 5, 6, 8, 9, 11, 12, 14, 15), the 1C capacity retention rate can be optimized while improving the first efficiency and specific capacity of the battery.

[0235] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0236] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0237] It should be readily understood that the terms “on,” “above,” and “on top of” in this application should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0238] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90° or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0239] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A negative electrode sheet, characterized in that, It includes a negative electrode current collector (100) and a negative electrode active material layer (200) disposed on the negative electrode current collector (100), wherein the negative electrode active material layer (200) has a porous structure; The physical specific surface area SSA of the negative electrode active material layer (200) and the electrochemical specific surface area C of the negative electrode sheet are... dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g.

2. The negative electrode sheet according to claim 1, characterized in that, The physical specific surface area SSA of the negative electrode active material layer (200) satisfies: 0.5m² 2 / g<SSA<3m 2 / g.

3. The negative electrode sheet according to claim 1, characterized in that, The electrochemical specific surface area C of the negative electrode sheet dl Satisfy: 4mF / g < C dl <100mF / g.

4. A negative electrode sheet according to claim 1, characterized in that, The negative electrode active material layer (200) includes a binder, and the mass ratio of the carbon-based active material in the negative electrode active material layer (200) to the binder is 100:(2-8); And / or, the negative electrode active material layer (200) further includes a conductive agent, and the mass ratio of the carbon-based active material in the negative electrode active material layer (200) to the conductive agent is 100:(0.5~1.5).

5. A negative electrode sheet according to claim 4, characterized in that, The carbon-based active material includes one or a combination of two of artificial graphite and natural graphite.

6. A negative electrode sheet according to claim 4, characterized in that, The conductive agent includes one or more of acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.

7. A negative electrode sheet according to claim 4, characterized in that, The adhesive comprises one or more of the following: polytetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers, polyethers and their copolymers, polyphenylene ethers and their copolymers, polysiloxanes and their copolymers, polyesters and their copolymers, polyethylene oxide, polyethylene glycol block copolymers, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber, polyethylene ester, polyvinyl acetate, and polyacrylate. And / or, the adhesive includes one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber.

8. A negative electrode sheet according to any one of claims 1-7, characterized in that, The areal density of the negative electrode sheet is 160 g / m³. 2 -240 g / m 2 ; And / or, the compaction density of the negative electrode sheet is 1.4 g / cc to 1.65 g / cc.

9. A method for preparing a negative electrode sheet, characterized in that, Includes the following steps: The negative electrode active material layer (200) is coated on the negative electrode current collector (100); The negative electrode current collector (100) and the negative electrode active material layer (200) are compacted to obtain the negative electrode sheet; The physical specific surface area SSA of the negative electrode active material layer (200) and the electrochemical specific surface area C of the negative electrode sheet are... dl The following condition must be met: 8 < C dl / SSA < 35, SSA units are in meters 2 / g calculation, C dl The unit is mF / g.

10. A method for preparing a negative electrode sheet according to claim 9, characterized in that, It also includes the following steps: The carbon-based active material, binder, conductive agent, and solvent are mixed and stirred evenly to obtain a slurry; The slurry is dried and granulated into powder to form the negative electrode active material layer (200).

11. The method for preparing a negative electrode sheet according to claim 10, characterized in that, The mass ratio of the carbon-based active material to the binder is 100:(2-8); And / or, the mass ratio of the carbon-based active material to the conductive agent is 100:(0.5~1.5); And / or, the mass ratio of the carbon-based active material to the solvent is 100:(100-120).

12. The method for preparing a negative electrode sheet according to claim 10, characterized in that, The particle size of the powder ranges from 20 μm to 120 μm.

13. The method for preparing a negative electrode sheet according to claim 10, characterized in that, The slurry is dried by spray drying.

14. The method for preparing a negative electrode sheet according to claim 13, characterized in that, The air inlet rate for the spray drying is 50 mL / h to 5000 mL / h; And / or, the inlet air temperature of the spray dryer is 30°C to 300°C; And / or, the outlet air temperature of the spray dryer is 30℃~140℃.

15. The method for preparing a negative electrode sheet according to claim 9, characterized in that, The compaction can be either hot pressing or cold pressing.

16. The method for preparing a negative electrode sheet according to claim 15, characterized in that, The pressure of the hot pressing is 0.2T to 2T; And / or, the temperature of the hot pressing is 100℃~250℃.

17. A battery, characterized in that, Includes a negative electrode sheet according to any one of claims 1-8.

18. A battery pack, characterized in that, Includes the battery described in claim 17.

19. An electrical appliance, characterized in that, Includes a battery pack as described in claim 18.

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