Negative plate, preparation method thereof and battery

Abstract

The invention relates to a negative plate, a preparation method thereof and a battery. The negative plate comprises a negative current collector and an active material layer coated on at least one side of the negative current collector through rolling, the active material layer comprises a silicon-carbon material, the specific surface area of the silicon-carbon material is Sm < 2 > / g, S is greater than or equal to 1 and less than or equal to 3.5, the particle size distribution Dv10 of the silicon-carbon material is D [mu] m, D is greater than or equal to 4.5 and less than or equal to 15, the negative plate meets the condition that P is greater than or equal to k1 * D-k2 * S + k3, P is the compressive strength of the negative plate, and the unit is Mpa; k1 is 4 to 6, k2 is 1.5 to 2.5, and k3 is 3 to 7. According to the scheme provided by the invention, the specific surface area of the negative electrode silicon carbon material can be reduced and the Dv10 can be increased by regulating and controlling the microstructure, so that the compressive strength and the cycle performance of the battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to negative electrode sheets, their preparation methods, and batteries. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and lack of memory effect, have become the primary energy storage technology in consumer electronics and electric vehicles. Silicon, with its extremely high theoretical specific capacity, abundant crustal reserves, and low lithium potential, is considered the most promising next-generation lithium battery anode material. However, silicon anodes experience significant volume expansion (~300%) during charging and discharging, leading to electrode structure pulverization, detachment of active materials from the conductive network, and repeated rupture and regeneration of the solid electrolyte interphase (SEI) film. These problems ultimately manifest as rapid capacity decay, low initial efficiency, and insufficient cycle life.

[0003] In related technologies, the thickness and areal density of the electrode are controlled by a rolling process to improve electrode density and particle contact. However, this control cannot precisely regulate the microstructure of the electrode, which can easily lead to two extremes: if the rolling is insufficient, the electrode porosity is high, the particle contact is poor, and the compressive strength is poor, making it impossible to effectively constrain the expansion of silicon; if the rolling is excessive, it may crush the active particles, damage the conductive network, or even generate microcracks, which will also impair the structural integrity and electrochemical performance of the electrode.

[0004] Therefore, it is urgent to study the relationship between microstructure and macroscopic mechanical properties during electrode fabrication, and to improve the compressive strength and cycle performance of electrodes by controlling the microstructure. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this application provides a negative electrode sheet, its preparation method, and a battery, which can improve the battery's compressive strength and cycle performance by adjusting the microstructure, reducing the specific surface area of ​​the negative electrode silicon-carbon material, and increasing Dv10.

[0006] A first aspect of this application provides a negative electrode sheet, comprising a negative electrode current collector and an active material layer rolled onto at least one side of the negative electrode current collector, the active material layer comprising a silicon-carbon material, the specific surface area of ​​the silicon-carbon material being Sm 2 / g, 1≤S≤3.5, the particle size distribution Dv10 of the silicon-carbon material is Dμm, 4.5≤D≤15, and the negative electrode sheet satisfies: P≥k1×D-k2×S+k3 Wherein, P is the compressive strength of the negative electrode sheet, in MPa; k1 is 4~6, k2 is 1.5~2.5, and k3 is 3~7.

[0007] As an optional embodiment, the battery prepared by this negative electrode satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 15 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the silicon lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode does not deviate by more than 10mV compared with the first cycle.

[0008] As an optional embodiment, 1.5 ≤ D / S ≤ 10.

[0009] As an optional embodiment, 1.8 ≤ D / S ≤ 10.

[0010] As an optional embodiment, the battery prepared by this negative electrode satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 10 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the silicon lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode sheet shifts by no more than 8mV compared with the first cycle.

[0011] As an optional embodiment, 1 ≤ S ≤ 3.

[0012] As an alternative embodiment, 4.8 ≤ D ≤ 15.

[0013] A second aspect of this application provides a method for preparing the aforementioned negative electrode sheet, comprising: Preparation of anode active slurry containing silicon-carbon materials; The negative electrode active slurry is coated on at least one side of the negative electrode current collector to form an active material layer; The active material layer is rolled using a roll forming process to obtain the negative electrode sheet.

[0014] As an optional embodiment, the rolling process includes: a pressure of 40T~80T, and / or a rolling speed of 3m / min~15m / min.

[0015] A third aspect of this application provides a battery comprising the aforementioned negative electrode sheet, or a negative electrode sheet prepared by the aforementioned method.

[0016] The technical solution provided in this application may include the following beneficial results: This application correlates and defines the microstructural parameters (specific surface area S and Dv10 particle size D) of the rolled silicon-carbon anode with its macroscopic mechanical properties (compressive strength P) using the quantitative formula P≥k1×D-k2×S+k3. By controlling the rolling process, while ensuring ion transport (S≥1), the specific surface area can be synergistically reduced (S≤3.5) to suppress side reactions, and the Dv10 particle size can be increased (4.5≤D≤15) to construct a coarse-particle stable framework. This directly and predictably improves the electrode's compressive strength, structural stability, and cycle life, transforming electrode manufacturing from an empirical operation into a quantifiable and controllable scientific process. This brings significant performance and manufacturing advantages: in terms of performance, it breaks the traditional contradiction between "high capacity" and "long cycle life" of silicon-carbon materials. While allowing the use of higher capacity silicon materials, it achieves a balance between high energy density, long cycle life, and high safety by suppressing expansion damage with a robust electrode structure and reducing side reactions with a stable interface. In terms of manufacturing, this solution provides clear microstructure control targets (S and D ranges) and associated process windows, transforming electrode manufacturing from vague "experience-based operations" into precise and controllable "scientific processes." It not only has a wide process window and strong operability, making it easy to control quality online, but its core concept is also highly universal and can be adapted to different types of silicon-carbon materials and binder systems, possessing excellent technology transfer and iteration capabilities.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0018] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0019] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0021] In related technologies, the thickness and areal density of the electrode are controlled by a rolling process to improve electrode density and particle contact. However, this control cannot precisely regulate the microstructure of the electrode, which can easily lead to two extremes: if the rolling is insufficient, the electrode porosity is high, the particle contact is poor, and the compressive strength is poor, making it impossible to effectively constrain the expansion of silicon; if the rolling is excessive, it may crush the active particles, damage the conductive network, or even generate microcracks, which will also impair the structural integrity and electrochemical performance of the electrode.

[0022] Therefore, it is urgent to study the relationship between microstructure and macroscopic mechanical properties during electrode fabrication, and to improve the compressive strength and cycle life of electrodes by controlling the microstructure.

[0023] To address the aforementioned issues, this application provides a negative electrode sheet that can reduce the specific surface area of ​​the negative electrode silicon-carbon material and increase Dv10 by adjusting the microstructure, thereby improving the battery's compressive strength and cycle performance.

[0024] This application provides a negative electrode sheet, including a negative electrode current collector and an active material layer rolled onto at least one side of the negative electrode current collector. The active material layer includes a silicon-carbon material with a specific surface area of ​​Sm. 2 / g, 1≤S≤3.5, the particle size distribution Dv10 of the silicon-carbon material is Dμm, 4.5≤D≤15, and the negative electrode sheet satisfies: P≥k1×D-k2×S+k3 Where P is the compressive strength of the negative electrode, in MPa; k1 is 4~6, k2 is 1.5~2.5, and k3 is 3~7.

[0025] In this embodiment, the specific surface area of ​​silicon-carbon material refers to the specific surface area of ​​the active material layer powder scraped from the negative electrode after rolling, and the unit is square meters per gram (m²). 2S (saturation area) represents the sum of the inner and outer surfaces of material particles, including the outer surface of the particles and the internal pore surface. For example, the specific surface area can be measured using the gas adsorption method (BET method), typically low-temperature nitrogen adsorption. S can be controlled through a rolling process. For instance, higher rolling pressure and / or lower rolling speed can cause plastic deformation in soft materials (such as silicon), filling the voids between particles and potentially closing some surface micropores, thus significantly reducing the overall specific surface area.

[0026] Setting S≥1 ensures that the material retains necessary ion transport channels and a suitable interface with the electrolyte, preventing excessive compaction from affecting reaction kinetics. If S is too low (e.g., S<1), it may lead to a sharp increase in lithium-ion diffusion resistance and a deterioration in battery rate performance.

[0027] Setting S ≤ 3.5, a lower surface area means a significant reduction in active sites that come into contact with the electrolyte and undergo decomposition reactions (forming an unstable SEI film). This directly improves the initial coulombic efficiency and reduces the continuous consumption of electrolyte and active lithium during cycling. Low S is generally associated with high particle packing density and tight particle-particle contacts, which are the basis for high mechanical strength. Furthermore, conventional wisdom might suggest that a high specific surface area is beneficial for the reaction. However, this application explicitly states that for silicon-carbon systems with significant volume expansion, ensuring interfacial stability and structural robustness is more important than providing more reaction interfaces.

[0028] In this embodiment, the particle size distribution Dv10 of the silicon-carbon material can refer to a statistical diameter in the particle size distribution, indicating that 10% of the volume of particles in the sample are smaller than this size. An increase in the D value means a relative decrease in the content of fine powder in the system. For example, the particle size distribution of powder scraped after rolling can be measured using laser diffraction (laser particle size analyzer). The D value can be controlled through the rolling process. For instance, higher rolling pressure and / or lower rolling speed may cause fine particles to embed or be encapsulated between larger particles, or cause softer silicon to undergo plastic deformation and encapsulate around harder carbon, resulting in a rightward shift of the particle size distribution curve, i.e., an increase in the Dv10 value.

[0029] Setting Dv10 ≥ 4.5 μm allows for the control of excessively fine particles in the electrode to a low level. Too many excessively fine particles lead to a large specific surface area, exacerbating side reactions. Furthermore, they are more prone to stress concentration during volume expansion, resulting in particle pulverization and structural collapse. The embodiments of this application, by using Dv10 ≥ 4.5 μm, are essentially constructing an electrode structure with a stable framework of larger particles.

[0030] Setting Dv10≤15μm can prevent excessively large particles from causing poor coating uniformity and excessively long ion electron transport paths. Moreover, excessively large particles may also cause cracks during rolling due to uneven stress.

[0031] Furthermore, in this embodiment, P ≥ k1×D - k2×S + k3 is set. This directly correlates the offline measurable microscopic parameters (D, S) with the key macroscopic mechanical properties (compressive strength P) that determine the electrode's lifespan.

[0032] The compressive strength P refers to the electrode's ability to resist silicon expansion stress, which can be obtained by directly measuring the electrode sheet using a micromechanical compression testing machine.

[0033] k1 is the positive weighting coefficient of D. The large coefficient indicates that increasing Dv10 makes a very significant contribution to improving the strength P, confirming the importance of constructing a coarse-grained stable framework.

[0034] k2 is the negative weighting coefficient of S. The negative coefficient indicates that reducing S also makes a significant and direct contribution to increasing the strength P, confirming the strategy of reducing specific surface area to enhance density.

[0035] k3 is the intercept constant, which covers the contribution of other intrinsic material properties (such as binder strength, carbon matrix hardness, etc.) to the base strength, excluding D and S.

[0036] In production, only samples of the rolled electrode sheets need to be tested for D and S. This formula allows for a rapid prediction of whether the mechanical strength meets the standards, eliminating the need for destructive mechanical testing on each batch. This formula defines the microstructural spatial boundary of a qualified electrode. The electrode is considered to have sufficient pressure resistance if the combination of D and S results in the calculated value k1×D-k2×S+k3 being less than or equal to the measured value P.

[0037] Therefore, in this embodiment, the microstructural parameters (specific surface area S and Dv10 particle size D) of the rolled silicon-carbon anode are correlated and defined with the macroscopic mechanical properties (compressive strength P) using the quantitative formula P≥k1×D-k2×S+k3. By controlling the rolling process, while ensuring ion transport (S≥1), the specific surface area can be synergistically reduced (S≤3.5) to suppress side reactions, and the Dv10 particle size can be increased (4.5≤D≤15) to construct a coarse-particle stable framework. This directly and predictably improves the compressive strength, structural stability, and cycle life of the electrode, transforming electrode manufacturing from an empirical operation into a quantifiable and controllable scientific process. This brings significant performance and manufacturing advantages: in terms of performance, it breaks the traditional contradiction between "high capacity" and "long cycle life" of silicon-carbon materials. While allowing the use of higher capacity silicon materials, it achieves a balance of high energy density, long cycle life, and high safety by suppressing expansion damage with a robust electrode structure and reducing side reactions with a stable interface. In terms of manufacturing, this solution provides clear microstructure control targets (S and D ranges) and associated process windows, transforming electrode manufacturing from vague "experience-based operations" into precise and controllable "scientific processes." It not only has a wide process window and strong operability, making it easy to control quality online, but its core concept is also highly universal and can be adapted to different types of silicon-carbon materials and binder systems, possessing excellent technology transfer and iteration capabilities.

[0038] As an optional embodiment, the battery prepared by this negative electrode satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 15 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode is not more than 10mV off from that of the first cycle.

[0039] In this embodiment, the dQ / dV curve refers to the spectrum obtained by differentiating the charge-discharge curve (voltage V - capacity Q) by (dQ / dV). It can amplify and clearly reveal the precise potential and reaction intensity of the electrochemical reaction, and is known as the electrochemical fingerprint of the battery.

[0040] The meaning of condition (1) is as follows: The significance of the 0.7V-0.9V range: For silicon-carbon anodes, the initial lithium intercalation process below 1.0V has a main reaction peak at approximately 0.45V for silicon-lithium alloying. However, in the higher potential range of 0.7V-0.9V, the lithiation reaction between silicon and graphite has not yet begun or is very weak. The current signal here mainly comes from irreversible side reactions such as electrolyte decomposition and the formation of the solid electrolyte interphase (SEI) film. Therefore, the average absolute value of the current within the 0.7V to 0.9V potential range is a direct and quantitative indicator of the severity of side reactions. The lower the current value, the milder the side reactions per unit capacity. Setting the threshold to 15μA / mAh means that the anode sheet of this embodiment can suppress harmful side reactions to an extremely low level, improve the initial coulombic efficiency, and maintain a high and stable coulombic efficiency during cycling. This also means that more active lithium is used for reversible energy storage.

[0041] For example, high-precision voltage-capacity data can be recorded by assembling a half-cell (for lithium metal) or a full cell and performing an initial charge-discharge cycle with a sufficiently small current (e.g., 0.05C or 0.1C). The dQ / dV curve is obtained through mathematical differentiation, and the absolute value of the current is integrated and averaged over the 0.7V-0.9V range.

[0042] The meaning of condition (2) is as follows: The lithiation reduction peak refers to the sharp peak at approximately 0.45 V on the dQ / dV curve, corresponding to the transformation of silicon from a crystalline state to an amorphous LixSi alloy. The peak potential of this peak is a sensitive indicator of reaction kinetics.

[0043] A significant positive shift in peak potential after cycling (towards higher potentials) indicates that the lithiation reaction has become more difficult and polarization has increased significantly. This is usually caused by increased internal resistance due to electrode structure damage, excessive SEI film thickness, or poor contact between active materials. Keeping the shift within 10mV is evidence that the electrode structure remains highly stable during long-term cycling.

[0044] For example, the same battery can be tested again under the same low-current conditions after 100 standard cycles, and the dQ / dV curve can be obtained. The peak potentials of the silicon reduction peak in the first and 100th curves are accurately calibrated, and their difference is calculated (usually the absolute value).

[0045] A closed loop from "structural indicators" to "performance verification": Weight 1 defines the "physical condition" (microstructure and mechanical strength) of the electrode, while Weight 2 defines its "health status" (electrochemical performance). The combination of the two constitutes a complete logical chain from manufacturing to end-user performance.

[0046] The embodiments of this application define the electrochemical performance of the negative electrode through conditions (1) and (2), and combine them with the characterization of microstructure and mechanical strength to form a complete life chain for characterizing the negative electrode from manufacturing to end-use performance. Moreover, the dQ / dV data are the raw results of electrochemical testing. Meeting these two conditions can demonstrate the superior performance of the negative electrode in reducing irreversible capacity loss (improving first-efficiency) and maintaining long-term cycle stability.

[0047] As an optional embodiment, 1.5 ≤ D / S ≤ 10.

[0048] In this embodiment, D / S is a dimensionless number that relates particle size to specific surface area. It measures the particle size per unit specific surface area.

[0049] If the D / S value is low (e.g., D / S < 1.5), it means that the specific surface area (S) is too large relative to the particle size (D). This usually corresponds to two situations: ① the particles themselves are very fine (small D); ② the particles are not small but have porous or rough surfaces (large S). Both situations indicate a fragile electrode structure and high side reaction activity.

[0050] Therefore, setting D / S ≥ 1.5 can ensure that the electrode has basic structural stability and interface stability.

[0051] If the D / S value is high (e.g., D / S > 10), an excessively high D / S may mean that D is too large or S is too small. The former will affect the uniformity of slurry coating and ion transport, while the latter may mean that excessive rolling pressure will cause the pores to close completely, which will also impair performance. Therefore, setting D / S ≤ 10 can ensure that the optimization of the structure is carried out within a reasonable window.

[0052] In the embodiments of this application, D / S can be 1.5, 2, 4, 6, 8, 10, or any value within the above-mentioned range, and this application does not limit it in this regard.

[0053] As a preferred embodiment, 1.8 ≤ D / S ≤ 10.

[0054] In the embodiments of this application, when the D / S ratio reaches 1.8 or higher, the microstructure of the electrode undergoes a qualitative change, for example: (1) the average absolute value of the current is less than 10 μA / mAh in the potential range of 0.7V to 0.9V; (2) after 100 charge-discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the battery prepared by this negative electrode is no more than 8mV off from that of the first cycle. A higher D / S ratio usually corresponds to a coarser and denser particle packing network, and the compressive strength (P) is more likely to satisfy P≥k1×D-k2×S+k3.

[0055] As a preferred embodiment, the battery prepared by this negative electrode sheet satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 10 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode does not deviate by more than 8mV compared with the first cycle.

[0056] In the embodiments of this application, when 1.5≤D / S≤10, or even 1.8≤D / S≤10, on the dQ / dV curve of the first charge and discharge, in the potential range of 0.7V to 0.9V, the average absolute value of the current decreases from 15μA / mAh to 10μA / mAh, indicating that the level of side reaction is suppressed to an extremely low degree, which foreshadows a high first coulombic efficiency close to the theoretical limit and an extremely low active lithium consumption rate.

[0057] After 100 charge-discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the battery prepared by this negative electrode decreased from 10mV to 8mV compared with the first cycle. This indicates that the stability of the electrode structure has been further improved and the polarization growth is negligible. This means that the conductive network and ion channels are almost the same after 100 cycles, which is a key prerequisite for ultra-long cycle life.

[0058] As an optional embodiment, 1 ≤ S ≤ 3.

[0059] The embodiments of this application further control the specific surface area of ​​the electrode after rolling to no more than 3 m². 2 The lower / g level means less lithium and electrolyte are consumed in SEI film formation, resulting in higher first-efficiency. Furthermore, less fresh surface is available for continued side reactions in subsequent cycles, leading to better cycle stability. The electrodes are also more dense, providing stronger constraints on volume expansion.

[0060] In the embodiments of this application, S can be 1, 1.5, 2.0, 2.2, 2.8, 3, or any value within the above-mentioned range, and this application does not limit it in this regard.

[0061] As an alternative embodiment, 4.8 ≤ D ≤ 15.

[0062] This application further raises the lower limit of D from 4.5 μm to 4.8 μm, ensuring that after rolling, the content of excessively small fine powder in the electrode is compressed to a lower level. This results in a higher proportion of coarse particles, which better maintains the overall framework without deformation when subjected to silicon expansion stress. Reducing stress concentration points such as fine powder prevents local collapse from triggering a chain reaction. Under rolling action, the increase in D and the decrease in S often occur simultaneously. Raising the lower limit of D also indirectly promotes the decrease in S, making it easier to achieve a high D / S value.

[0063] In the embodiments of this application, D can be 4.8, 6.0, 8.8, 10.2, 12.5, 14.8, 15, or any value within the above-mentioned range, and this application does not limit it in this regard.

[0064] Corresponding to the aforementioned application function implementation method embodiments, this application also provides a method for preparing the aforementioned negative electrode sheet and corresponding embodiments.

[0065] This application provides a method for preparing the aforementioned negative electrode sheet, including: S1. Prepare a negative electrode active slurry containing silicon-carbon materials.

[0066] For example, silicon-carbon composite anode material, conductive agent (such as conductive carbon black, carbon nanotubes), binder (such as CMC / SBR, polyacrylate) and solvent (usually deionized water or N-methylpyrrolidone NMP) are mixed in a specific ratio and a uniform and stable slurry is prepared by stirring, dispersing and other processes.

[0067] S2. The negative electrode active slurry is coated on at least one side of the negative electrode current collector to form an active material layer; For example, the above slurry is uniformly coated on one or both sides of the negative electrode current collector (usually copper foil) by means of transfer coating, slot extrusion coating, etc. Then it is dried in a multi-stage oven to remove the solvent and form an uncompressed active material layer precursor with a certain porosity structure.

[0068] S3. The active material layer is rolled using a roll forming process to obtain the negative electrode sheet.

[0069] S1. Preparation of negative electrode active slurry containing silicon-carbon materials: For example, a twin-roll calender or similar rolling equipment is used to roll the dried electrode sheet. This step is a key process for achieving the core microstructure control of this patent. By precisely controlling the rolling parameters, the active material layer undergoes the expected plastic deformation and particle rearrangement, ultimately obtaining a negative electrode sheet that meets the requirements of microstructure (S, D) and performance (P).

[0070] In this embodiment, rolling is not merely for reducing thickness, but rather a tool for actively shaping the electrode's microstructure. Rolling reduces porosity, increases interparticle contact, and thus reduces the specific surface area (S). It also causes fine powder to embed or encapsulate, undergoing plastic deformation, thereby increasing the Dv10 particle size (D). Through this process, the compressive strength (P) of the electrode is directly improved.

[0071] As an optional embodiment, the rolling process includes a pressure of 40T to 80T.

[0072] In this embodiment of the application, the rolling pressure can refer to the total pressure applied to the rolls of the rolling mill.

[0073] Setting the pressure to be no less than 20T ensures that the applied pressure is sufficient to initiate the plastic deformation and rearrangement of the active material particles (especially the silicon phase). If the pressure is lower than this value (such as 20T), the rolling effect will be insufficient, failing to effectively reduce S and increase D, making it difficult to achieve the required structural strength and microstructure.

[0074] Setting the pressure to no more than 80T can prevent destructive consequences caused by excessive pressure. For example: a. crushing brittle carbon skeletons or conductive agent networks. b. causing microcracks invisible to the naked eye in the electrode. c. over-compacting pores, severely hindering lithium-ion transport. d. although lower S and higher D may be obtained, the integrity of the electrode is sacrificed, resulting in a decrease in compressive strength P and cycle performance.

[0075] As an optional embodiment, the rolling process includes a rolling speed of 3m / min to 15m / min.

[0076] In this embodiment, the roller speed can refer to the linear velocity of the electrode sheet passing through the roller gap. It determines the time for the material to deform and relax under high pressure.

[0077] Setting the roller speed to no less than 1 m / min allows the material more time for plastic flow and particle rearrangement, which is beneficial for forming a uniform and dense structure. However, excessively slow speeds negatively impact production efficiency.

[0078] Setting the roller speed to no more than 15 m / min ensures that the material can still achieve effective compression within the reasonable efficiency of industrial production. Excessive speed and insufficient compression time can lead to inadequate deformation, poor microstructure control, and may cause electrode warping or uneven thickness.

[0079] Corresponding to the aforementioned application function implementation method embodiments, this application also provides a battery and corresponding embodiments.

[0080] This application also provides a battery, including the aforementioned negative electrode sheet, or a negative electrode sheet prepared by the aforementioned method.

[0081] In this embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material coated on at least one side of the negative electrode current collector.

[0082] This application does not limit the selection of the negative electrode current collector; it can be selected according to actual needs, such as copper foil. The negative electrode active material layer of this application includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The negative electrode active material includes silicon-carbon / graphite composite negative electrode materials, which include silicon-carbon composite materials and surface-modified graphite materials. Silicon-carbon composite materials include silicon and carbon materials. This application does not limit the selection of carbon materials; it can be selected according to actual needs, such as graphite, carbon black, hard carbon, soft carbon, etc. This application does not limit the selection of silicon materials; it can be selected according to actual needs, such as silicon oxide, pre-lithiated silicon oxide, pre-magnesiated silicon oxide materials, silicon-carbon composite materials, elemental silicon, etc. The negative electrode binder of this application includes one or more of polyacrylic acid, polydopamine, and carboxymethyl cellulose. Polypropylene compounds refer to polypropylene derivatives, such as polyacrylic acid, polyacrylonitrile, polyacrylamide, and polymethyl methacrylate. The negative electrode conductive agent includes one or more of carbon nanotubes, graphene, and vapor-grown carbon fibers.

[0083] This application does not impose any particular limitation on the specific type of battery; it can be a secondary battery, a power battery, an energy storage battery, etc. The battery casing can be used to encapsulate the battery cell and electrolyte. The battery casing can be a hard casing, such as a hard plastic casing, an aluminum casing, or a steel casing. It can also be a pouch battery, such as a pouch-type pouch. The material of the pouch can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate. This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape.

[0084] The battery cell in this application embodiment can be formed by winding a positive electrode sheet, a negative electrode sheet, and a separator. Specifically, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, the stacked electrode sheets and the separator are wound together to obtain the battery cell.

[0085] The electrolyte in this embodiment includes an organic solvent, a lithium salt, and a first additive. The first additive includes a compound having an unsaturated hydrocarbon group. Using a compound having an unsaturated hydrocarbon group as the first additive can coordinate with lithium ions, promote the dissociation of lithium salt, and enhance the conduction of lithium ions in the polymer electrolyte.

[0086] In one specific embodiment, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, which include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0087] In this embodiment, the positive electrode sheet includes a positive current collector and a positive active material coated on at least one side of the positive current collector.

[0088] This application does not limit the selection of the positive electrode current collector, which can be selected according to actual needs, such as copper foil. The positive electrode active material layer in this application embodiment can be coated on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, which is selected from one or more of transition metal lithium oxides, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate. The chemical formula of the transition metal lithium oxide is Li1+xNiyCozM(1-yz)O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; and M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0089] In one specific embodiment, the positive electrode active material layer further includes a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0090] The liquid electrolyte in this application embodiment includes an electrolyte salt, an organic solvent, and additives. In this application embodiment, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiODFB), lithium bis(oxalate borate) (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorophosphate (LiPOF2), and the concentration of the electrolyte salt can be from 0.4 mol / L to 2.2 mol / L.

[0091] In the embodiments of this application, the organic solvent includes at least one selected from ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, ethyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0092] In the embodiments of this application, the electrolyte additive also includes other additives, including but not limited to several of the following: vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), succinate (SN), adiponitrile (ADN), 1,3,6-hexanetrionitrile (HTCN), propenesulfonate lactone (PST), methylene disulfonate (MMDS), ethylene glycol bis(propionitrile) ether (EGBE), pentafluoroethoxyphosphazene, dicyclohexylcarbonyl, trimethyl imide phosphate, and hexamethylene diisocyanate.

[0093] Corresponding to the aforementioned application function implementation method embodiments, this application also provides an electronic device and corresponding embodiments.

[0094] This application also provides an electronic device, including the aforementioned battery.

[0095] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0096] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0097] Example 1 I. Battery Preparation 1. Preparation of negative electrode sheet S1. Prepare a negative electrode active slurry containing silicon-carbon materials.

[0098] A uniform and stable slurry is prepared by mixing silicon-carbon composite anode material, conductive agent (such as conductive carbon black, carbon nanotubes), binder (such as CMC / SBR, polyacrylates) and solvent (usually deionized water or N-methylpyrrolidone NMP) in a specific ratio and then through processes such as stirring and dispersion.

[0099] S2. The negative electrode active slurry is coated on at least one side of the negative electrode current collector to form an active material layer.

[0100] The above slurry is uniformly coated on one or both sides of the negative electrode current collector (usually copper foil) using methods such as transfer coating or slot extrusion coating. It is then dried in a multi-stage oven to remove the solvent, forming an uncompressed active material layer precursor with a certain porous structure.

[0101] S3. The active material layer is rolled using a roll forming process to obtain the negative electrode sheet.

[0102] The dried electrode sheet is rolled using a twin-roll calender or similar rolling equipment. This step is the key process for achieving the core microstructure control of this patent. By precisely controlling the rolling parameters, the active material layer undergoes the expected plastic deformation and particle rearrangement, ultimately obtaining a negative electrode sheet that meets the requirements of microstructure (S, D) and performance (P).

[0103] 2. Microstructure parameters and mechanical property testing a. Sampling: Carefully scrape the active material layer powder from the negative electrode sheet after each roller pressing.

[0104] b. Specific surface area (S) test: The specific surface area of ​​the scraped powder was measured using the BET nitrogen adsorption method (according to standard ISO 9277).

[0105] c. Particle size Dv10 (D) test: The particle size distribution of the scraped powder was measured using a laser particle size analyzer, and the Dv10 value was recorded.

[0106] d. Compressive strength (P) test: Using a micromechanical testing instrument, the cut electrode sheet sample is subjected to a compression test, and its compressive strength is recorded.

[0107] The specific formulation, preparation parameters, microstructure parameters and mechanical property tests are shown in Table 1.

[0108] 3. Preparation of positive electrode sheet The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent acetylene black SuperP, and the binder polyvinylidene fluoride PVDF are mixed evenly at a mass ratio of 97:1.5:1.5, and then evenly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry. The mixed slurry is coated on both sides of the aluminum foil current collector, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0109] 4. Preparation of electrolyte Commercially available electrolyte.

[0110] 5. Manufacturing of lithium-ion batteries The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets. After winding and welding the tabs, a bare cell is obtained. The bare cell is then placed in an aluminum-plastic film for electrolyte injection and encapsulation to obtain a lithium-ion battery. The preparation of lithium-ion batteries in each embodiment and comparative example is completed.

[0111] Table 1. Formulation, preparation parameters, microstructure parameters, and mechanical property test results.

[0112] II. Electrochemical Performance Testing The batteries prepared in each embodiment and comparative example were subjected to the following performance tests, and the test results are shown in Table 2.

[0113] 1. Method for testing the average value of absolute current (1) First charge and discharge test After the assembled battery was left to stand at a constant temperature of 25°C for 2 hours, the first charge-discharge test was conducted. The test conditions were as follows: Charge and discharge regime: discharge first (lithium ions are extracted from the positive electrode and inserted into the silicon-carbon negative electrode, corresponding to the "lithiation" or "lithiation" process of the negative electrode) and then charge.

[0114] Discharge cutoff voltage: 0.005V (vs. Li + / Li) Charging cutoff voltage: 1.5V (vs. Li + / Li) Current density: A small current of 0.05C (or C / 20) is used, specifically the current value calculated based on the theoretical specific capacity of the negative electrode active material (silicon-carbon material) (e.g., taking the average specific capacity of silicon-carbon composite material as 1000 mAh / g). The purpose of using a small current is to obtain high-resolution voltage-capacity data, making the differential curve (dQ / dV) smooth and the characteristic peaks obvious.

[0115] Data recording density: The test system records voltage (V) and cumulative capacity (Q) data at voltage intervals of not less than 1mV or 0.1% of capacity intervals.

[0116] (2) Obtaining the dQ / dV curve and calculating the target interval current value Import the high-precision voltage (V)-capacity (Q) data recorded during the first discharge (lithium intercalation) process into data processing software (such as Origin or a self-developed MATLAB program).

[0117] Differential calculation: The Q of the discharge curve is numerically differentiated with respect to V to obtain the dQ / dV-V curve. The differential window typically uses the Savitzky-Golay filtering method to smooth noise.

[0118] Target range definition: On the dQ / dV curve, determine 0.70V to 0.90V (vs. Li). + The potential range of / Li).

[0119] Current absolute value extraction and averaging: Within this interval, N data points (N≥20) are taken at equal intervals, and the corresponding dQ / dV value (usually in mAh / V or C / V) is recorded for each point. Since dQ / dV is numerically equivalent to the product of the reciprocal of the instantaneous current and the rate of change of voltage, it can directly reflect the relative intensity of the reaction current under certain conditions.

[0120] To standardize it to a current per unit capacity, the |dQ / dV| value of each data point is multiplied by the current density used during the test (I_test, in mA / g), and then divided by the areal loading of the active material (or directly using the conversion based on specific mass capacity).

[0121] 2. Test method for the shift of silicon lithiation reduction peak (1) Obtaining the dQ / dV curve in the first cycle Test conditions: The battery is first charged and discharged at a very low current density (e.g., 0.05C or C / 20) under constant temperature (e.g., 25°C). The low current is used to obtain high-resolution voltage-capacity data and to smooth the differential curve.

[0122] Voltage window: for example, discharge (lithium intercalation) to 0.005V (vs. Li) + / Li), charge to 1.5V (vs. Li) + / Li).

[0123] Data logging: Records voltage (V) and cumulative capacity (Q) data at high density.

[0124] Differential processing: The initial discharge curve (voltage V vs. capacity Q) is numerically differentiated (dQ / dV) to obtain the dQ / dV curve for the first cycle.

[0125] Peak position determination: On the initial dQ / dV curve, identify and precisely record the peak potential (V_initial) of the lithiation reduction peak. This peak is typically located at ~0.45V (vs. Lithium). + The area near / Li corresponds to the main reaction where amorphous silicon (a-Si) reacts with lithium to form a LixSi alloy.

[0126] (2) Obtaining the dQ / dV curve for the Nth cycle (e.g., the 100th cycle) Cyclic aging: The same battery is subjected to N cycles (specified as 100 cycles in the patent) under standard charge and discharge regimes (e.g., charge and discharge cycles at 0.5C or 1C).

[0127] Test again: After the Nth cycle, perform a charge-discharge test again under the exact same low current conditions (same current density, voltage window, and temperature) as the first cycle.

[0128] Differential processing: Similarly, differentiate the discharge curve for this (Nth cycle) to obtain the dQ / dV curve for the Nth cycle.

[0129] Peak position determination: On the Nth dQ / dV curve, identify and accurately record the peak potential (V_N) of the same lithiation reduction peak.

[0130] (3) Offset calculation Calculation formula: Offset (ΔV) = |V_N - V_initial| That is: Offset = Peak potential of lithiation reduction in week 100 - Peak potential of lithiation reduction in the first cycle 3. First Coulomb efficiency (1) Let the prepared battery stand for a period of time (e.g., 2 hours) to allow the electrolyte to fully wet it, and then proceed with the following steps: a. Initial discharge (lithium intercalation): Set the cutoff voltage: typically discharge to 0.005V or 0.01V (vs. Li + / Li). This lower voltage limit needs to be strictly controlled; if it is too low, lithium plating may occur, and if it is too high, lithium intercalation will be incomplete.

[0131] Set the current density: Use a smaller current, such as 0.1C or 0.05C. A smaller current is beneficial for the full diffusion and insertion of lithium ions, resulting in a capacity closer to thermodynamic equilibrium, and reducing the impact of polarization on efficiency calculations.

[0132] Record the first discharge capacity (C_discharge, 1st).

[0133] b. Resting: After the first discharge, a short resting step (such as 5-10 minutes) can be set to allow the voltage to relax.

[0134] c. First charge (lithium removal): Set the cutoff voltage: typically charge to 1.5V or 2.0V (vs. Li). + / Li).

[0135] Set the current density: usually the same as the discharge current (0.1C or 0.05C).

[0136] Record the initial charge capacity (C_charge, 1st).

[0137] (2) Data calculation First Coulomb efficiency (ICE,%) = [C_charge,1st / C_discharge,1st] × 100%.

[0138] 4. Cyclic performance (1) Initial benchmarking Initialize the battery by performing 1-3 charge-discharge cycles at 25±2°C using a small current (e.g., 0.1C) to form a stable SEI film. Charge the battery at a constant current and constant voltage of 1C (or an applicable rate) to the upper limit voltage cutoff current of 0.05C. Let it rest for 5 minutes. Discharge the battery at a constant current of 1C to the lower limit voltage. Record the discharge capacity as the initial capacity C0.

[0139] (2) Cyclic stability test Charge at a constant current of 1C to the upper limit voltage, then switch to constant voltage charging until the current is ≤0.05C, and let stand for 5 minutes; discharge at a constant current of 1C to the lower limit voltage, and let stand for 5 minutes. This is one complete cycle.

[0140] After every 50 cycles, perform a standard capacity test and a cell thickness test (the same procedure as the initial capacity calibration), and record the capacity C. n Continue until the predetermined number of cycles (e.g., 400 cycles) is reached, and calculate the capacity retention rate = (C... n / C0)×100%, when the capacity retention rate is 80%, record this cycle number as the cycle life.

[0141] 5. Cyclic Coulomb Efficiency At the end of each charge-discharge step during the test cycle performance, the system measures and records with high precision: a) Charging capacity (C_charge, N, unit: mAh or mAh / g) b) Discharge capacity (C_discharge, N, unit: mAh or mAh / g) The system automatically calculates: Based on the above data, the testing software will calculate and save the coulombic efficiency (CE_N) for the Nth cycle, for example, 400 cycles, in real time: CE_N(%) = (C_discharge,N / C_charge,N) × 100% Table 2 Test Results

[0142] Note: The average absolute value of the current refers to the average absolute value of the current in the potential range of 0.7V to 0.9V on the dQ / dV curve during the first charge and discharge cycle; the shift of the lithiation reduction peak refers to the shift of the peak potential of the lithiation reduction peak in the dQ / dV curve of the 100th cycle after the battery prepared by this negative electrode has undergone 100 charge and discharge cycles, compared with the first cycle.

[0143] By combining Tables 1 and 2 and comparing all the embodiments and all the comparative examples, it can be seen that when the specific surface area of ​​the silicon-carbon material is Sm 2 / g, 1≤S≤3.5, the particle size distribution of silicon-carbon material Dv10 is Dμm, 4.5≤D≤15, and when the negative electrode meets P≥k1×D-k2×S+k3, it is possible to reduce the specific surface area (S≤3.5) to suppress side reactions and increase the Dv10 particle size (4.5≤D≤15) to build a coarse particle stable skeleton by adjusting the rolling process, under the premise of ensuring ion transport (S≥1), thereby making the battery prepared by the negative electrode meet the conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average value of the absolute value of the current is less than 15μA / mAh in the potential range of 0.7V to 0.9V; (2) After the battery prepared by the negative electrode has undergone 100 charge and discharge cycles, the peak potential of the silicon lithiation reduction peak in the dQ / dV curve of the 100th cycle does not deviate by more than 10mV compared with the first cycle. Moreover, it can greatly improve the battery's initial coulombic efficiency, cycle life, and coulombic efficiency during cycling.

[0144] Further combining Examples 2 to 6, Examples 9 to 16, and Examples 1, 7, 8, 17, and 18, it can be seen that when 1.5 ≤ D / S ≤ 10 is satisfied, the battery prepared by the negative electrode can meet conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 10 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge and discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the 100th cycle of the battery prepared by the negative electrode is shifted by no more than 8mV compared with the first cycle. Furthermore, it can further improve the battery's initial coulombic efficiency, cycle life, and coulombic efficiency during cycling.

[0145] Further combining Examples 2 and 14, as well as Examples 3 to 6, 9 to 13, 15 and 16, it can be seen that when 1.8≤D / S≤10 is further satisfied, the average absolute value of the current in the dQ / dV curve of the battery prepared by the negative electrode sheet is further reduced in the potential range of 0.7V to 0.9V during the first charge and discharge cycle. After 100 charge and discharge cycles, the peak potential of the lithiation reduction peak in the dQ / dV curve of the 100th cycle is also further reduced compared with the first cycle, and the initial coulombic efficiency, cycle life and coulombic efficiency during the cycle can be further improved.

[0146] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.

[0147] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.

[0148] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A negative electrode sheet, characterized in that, The assembly includes a negative electrode current collector and an active material layer rolled onto at least one side of the negative electrode current collector, the active material layer comprising a silicon-carbon material having a specific surface area of ​​Sm. 2 / g, 1≤S≤3.5, the particle size distribution Dv10 of the silicon-carbon material is Dμm, 4.5≤D≤15, and the negative electrode sheet satisfies: P≥k1×D-k2×S+k3 Wherein, P is the compressive strength of the negative electrode sheet, in MPa; k1 is 4~6, k2 is 1.5~2.5, and k3 is 3~7.

2. The negative electrode sheet according to claim 1, characterized in that, The battery prepared using this negative electrode satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 15 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the silicon lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode does not deviate by more than 10mV compared with the first cycle.

3. The negative electrode sheet according to claim 1, characterized in that, 1.5≤D / S≤10.

4. The negative electrode sheet according to claim 3, characterized in that, 1.8≤D / S≤10.

5. The negative electrode sheet according to claim 3 or 4, characterized in that, The battery prepared using this negative electrode satisfies at least one of conditions (1) and (2): (1) On the dQ / dV curve of the first charge and discharge, the average absolute value of the current is less than 10 μA / mAh in the potential range of 0.7V to 0.9V; (2) After 100 charge-discharge cycles, the peak potential of the silicon lithiation reduction peak in the dQ / dV curve of the battery prepared by the negative electrode sheet shifts by no more than 8mV compared with the first cycle.

6. The negative electrode sheet according to claim 1, characterized in that, 1≤S≤3。 7. The negative electrode sheet according to claim 1, characterized in that, 4.8≤D≤15。 8. A method for preparing a negative electrode sheet as described in any one of claims 1 to 7, characterized in that, include: Preparation of anode active slurry containing silicon-carbon materials; The negative electrode active slurry is coated on at least one side of the negative electrode current collector to form an active material layer; The active material layer is rolled using a roll forming process to obtain the negative electrode sheet.

9. The method according to claim 8, characterized in that, The rolling process includes: a pressure of 40T~80T, and / or a rolling speed of 3m / min~15m / min.

10. A battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1 to 7, or the negative electrode sheet prepared by the method as described in claim 8 or 9.

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