Dry-method negative pole piece as well as preparation method and application thereof

Abstract

The invention provides a dry-method negative pole piece as well as a preparation method and application thereof. The dry-method negative pole piece at least comprises a negative pole current collector, a positive pole piece and a negative pole piece, the dry-method negative electrode active layer is at least arranged on the surface of one side in the thickness direction of the negative electrode current collector, the dry-method negative electrode active layer comprises a negative electrode active material, a conductive agent and a binder, and the uniformity of the binder in the dry-method negative electrode active layer is 85%-96%; the negative electrode active material comprises a silicon material, and the silicon material comprises but is not limited to silicon, a silicon carbon material and a silicon oxygen negative electrode material. According to the dry-method negative pole piece as well as the preparation method and the application thereof provided by the invention, the expansion of the negative active material can be inhibited, and the safety performance can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a dry-process negative electrode sheet and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries offer numerous advantages, including high voltage, high capacity, long cycle life, low self-discharge efficiency, and excellent safety. They are widely used in 3C / digital products, electric vehicles, energy storage, and other fields. The negative electrode is a crucial component of lithium-ion batteries, and its composition and structure have a decisive influence on their electrochemical performance.

[0003] Among many factors, the negative electrode active material, as an important component of lithium-ion batteries, has a particularly significant impact on the performance of lithium-ion batteries. During the charge and discharge cycle of the battery, as lithium ions are inserted and removed, the negative electrode active material will undergo volume changes. In particular, silicon materials often undergo volume changes of 120% to 300% or even more than 300%, which will worsen the interface contact and lead to a decline in battery performance. When preparing the negative electrode sheet by dry method, the volume expansion of the negative electrode active material will cause interfacial debonding with conductive agents, binders and other materials, resulting in failure of the electrode structure during the charge and discharge process. By increasing the content of binder between the negative electrode active materials, the adverse effects caused by the expansion of the negative electrode active material can be improved to a certain extent, but it will affect the charge and discharge performance, capacity attenuation, etc. of the battery. Summary of the Invention

[0004] The present invention proposes a dry-process negative electrode plate, a preparation method and an application thereof. Through the dry-process negative electrode plate, a preparation method and an application thereof provided by the present invention, by controlling the uniformity of the binder in the dry-process negative electrode active layer, the expansion of the negative electrode active material can be suppressed, the effective transmission of lithium ions and electrons can be promoted, the risk of shedding and short circuit of the dry-process negative electrode active layer can be reduced, and the safety performance can be improved.

[0005] In order to solve the above technical problems, the present invention provides a dry-process negative electrode sheet, comprising at least: negative electrode current collector; A dry-process negative electrode active layer is provided on at least one surface along the thickness direction of the negative electrode current collector, wherein the dry-process negative electrode active layer comprises a negative electrode active material, a conductive agent, and a binder, wherein the uniformity of the binder in the dry-process negative electrode active layer is 85%-96%; The negative electrode active material includes silicon material, which includes but is not limited to silicon, silicon-carbon material and silicon-oxygen negative electrode material.

[0006] In one embodiment of the present invention, the binder exists in the dry-process negative electrode active layer in the form of nanofibers, and the diameter of the nanofibers is d 5010nm-50nm, d 90 / d 10 ≤1.5, where d 50 is the diameter of the nanofibers when the number of nanofibers increases from small to large to 50%, d 10 is the diameter of the nanofibers when the number of nanofibers from small to large accumulates to 10%, d 90 It is the diameter when the cumulative number of the nanofiber diameters from small to large reaches 90%.

[0007] In one embodiment of the present invention, the silicon content of the negative electrode active material is A wt%; the nanofibers of the binder cover the surface of the negative electrode active material, and the area coverage of the nanofibers on the negative electrode active material is B%, and the dry-process negative electrode active layer satisfies the following relationship: -55≤0.45AB≤-45.

[0008] In one embodiment of the present invention, the content of the binder in the dry-process negative electrode active layer is 0.5 wt %-5 wt %.

[0009] In one embodiment of the present invention, the negative electrode active material further includes a graphite material, and the graphite material includes at least one of natural graphite and artificial graphite.

[0010] In one embodiment of the present invention, the mass percentage of the silicon material to the negative electrode active material is 0-100 wt %.

[0011] In one embodiment of the present invention, the binder comprises one or more combinations of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, ethylene-vinyl acetate copolymer, polypropylene, polyethylene, ethylene-octene copolymer or polyimide; And / or, the conductive agent is selected from at least one of graphite, graphene, carbon black, carbon fiber and carbon nanotubes.

[0012] The present invention also provides a method for preparing a dry-process negative electrode sheet, which comprises at least the following steps: Sieving binder particles with a preset median particle size; mixing the negative electrode active material, the conductive agent and the binder particles to obtain a mixed material; performing a fibrillation treatment on the mixed material to obtain a fibrillated material; Cooling the fibrillated material to a target temperature at a preset rate while applying shear to obtain an intermediate product; Crushing and granulating the intermediate product to obtain a dry-process negative electrode material; The dry-process negative electrode material is formed into a film by continuous rolling with multiple rollers to obtain a dry-process negative electrode active layer; The dry-process negative electrode active layer is compounded with the negative electrode current collector to obtain a dry-process negative electrode sheet.

[0013] In one embodiment of the present invention, the preset median particle size of the binder particles is X1 μm, and the diameter d of the nanofibers in the dry-process negative electrode active layer is 50 is X2nm, satisfying the following relationship: -5≤0.2X1-X2≤5; The binder particles have a predetermined median particle size of 20-250 μm.

[0014] In one embodiment of the present invention, the uniformity of the binder in the dry-process negative electrode active layer is X3%, satisfying the following relationship: 96≤0.054X1+X3≤100.

[0015] In one embodiment of the present invention, when the negative electrode active material is pure silicon, the median particle size of the binder particles is 40 μm-60 μm, and the content of the binder in the dry-process negative electrode active layer is 2 wt %-4 wt %.

[0016] In one embodiment of the present invention, the binder particles are sieved at a preset temperature, wherein the preset temperature is 5° C.-20° C.; The fibrillation includes a first stage, a second stage and a third stage. In the first stage, the treatment temperature is 20°C-40°C, the stirring linear speed is 20m / s-30m / s, and the stirring time is 10min-30min; in the second stage, the treatment temperature is 60°C-80°C, the stirring linear speed is 40m / s-60m / s, and the stirring time is 10min-30min; in the third stage, the treatment temperature is 90°C-120°C, the stirring linear speed is 60m / s-70m / s, and the stirring time is 60min-120min; The preset rate is 10°C / min-15°C / min, and the target temperature is 25°C-40°C; During the cooling process, pulse shearing is applied, wherein one pulse shearing comprises shearing at 8 m / s-10 m / s for 4 s-6 s and shearing at 3 m / s-5 m / s for 8 s-12 s.

[0017] The present invention also provides an all-solid-state lithium-ion battery, comprising at least: Positive electrode; A negative electrode sheet, selected from the dry-process negative electrode sheet described above, or a dry-process negative electrode sheet obtained by the preparation method described above; The solid electrolyte layer is arranged between the positive electrode sheet and the negative electrode sheet.

[0018] In one embodiment of the present invention, the negative electrode plate further includes a solid electrolyte, and the solid electrolyte is selected from at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte.

[0019] The present invention also provides an electronic device comprising the above-mentioned all-solid-state lithium-ion battery.

[0020] In summary, the present invention proposes a dry-process negative electrode plate and its preparation method and application. By improving the uniformity of the binder in the dry-process negative electrode active layer, the expansion of the negative electrode active material can be suppressed. On the premise of ensuring the mechanical stability of the negative electrode plate, the effective transmission of lithium ions and electrons can be promoted, the performance of the negative electrode plate can be improved, the risk of shedding and short circuit of the dry-process negative electrode active layer can be reduced, and the safety performance can be improved. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0022] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0023] The technical solutions of the present invention are further described in detail below with reference to the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] The present invention proposes a dry-process negative electrode sheet, comprising at least a negative electrode current collector and a dry-process negative electrode active layer. The dry-process negative electrode active layer is disposed on at least one surface along the thickness direction of the negative electrode current collector. The dry-process negative electrode active layer comprises a negative electrode active material, a conductive agent, and a binder. The uniformity of the binder in the dry-process negative electrode active layer is, for example, 85%-96%. The negative electrode active material comprises a silicon material, including but not limited to silicon, silicon-carbon material, and silicon-oxygen negative electrode material (SiO x, (0 < x < 2), etc. Among them, the silicon-carbon material is, for example, a structure in which silicon is embedded in a porous carbon material. The binder is used to connect the negative electrode active materials to each other or substances such as the negative electrode active material and the conductive agent. However, the binder is an insulating substance. If the distribution of the binder is uneven, it will lead to increased powder shedding or insulating regions, resulting in a reduction in ion conduction paths. Among them, the uniformity is defined as the degree of dispersion of the binder distribution in multiple detection regions of the negative electrode sheet, and the degree of dispersion and the uniformity are negatively correlated. In the dry-process negative electrode sheet provided by the present invention, by improving the uniformity of the binder in the dry-process negative electrode active layer, the expansion of the negative electrode active material can be inhibited. On the premise of ensuring the mechanical stability of the negative electrode sheet, the effective transmission of lithium ions and electrons can be promoted, the performance of the negative electrode sheet can be improved, the risk of shedding and short circuit of the dry-process negative electrode active layer can be reduced, and the safety performance can be improved.

[0025] In an embodiment of the present invention, the existing form of the binder in the dry-process negative electrode active layer is nanofibers, forming a three-dimensional nanofiber network structure. The diameter d of the nanofibers 50 is 10 nm - 50 nm, d 90 / d 10 ≤ 1.5. Among them, d 50 is the diameter when the cumulative number of nanofibers from small to large reaches 50%, and d 10 is the diameter when the cumulative number of nanofibers from small to large reaches 10%, and d 90 is the diameter when the cumulative number of nanofibers from small to large reaches 90%. If the diameter of the nanofibers is too small, the cohesive force will be too low. If the cohesive force is too low, the expansion problem of the negative electrode active material cannot be inhibited, resulting in problems such as particle pulverization, collapse of the conductive network, electrode shedding or interface contact failure. On the contrary, if the diameter of the nanofibers is too large, although the strength of the nanofibers increases, the insulating regions between the negative electrode active materials will increase, and the ion conduction paths will decrease. Therefore, it is necessary to select an appropriate nanofiber diameter of the binder, which can not only ensure the strength of the three-dimensional nanofiber network structure, ensure sufficient cohesive force, inhibit the expansion problem of the negative electrode active material, and avoid the dry-process negative electrode sheet from being too fragile, but also make the conduction paths more and more smooth, improving the ion transmission ability. At the same time, d 90 / d 10 ≤ 1.5, that is, the thickness uniformity of the nanofiber diameter is high and the distribution is uniform, which is beneficial to improving the uniformity of the binder in the dry-process negative electrode active layer, can avoid the ion transmission being blocked due to locally too thick fibers, and can also avoid the insufficient local mechanical strength caused by locally too thin fibers, thereby improving the performance of the dry-process negative electrode sheet.

[0026] In one embodiment of the present invention, the binder includes one or more of polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), ethylene-vinyl acetate (EVA), polypropylene (PP), polyethylene (PE), ethylene-octene copolymer, or polyimide (PI). The molecular weight of the binder is, for example, 6000 kg / mol to 8000 kg / mol, to improve the adhesive properties of the binder and the strength of the formed nanofibers. The binder content in the dry-process negative electrode active layer is, for example, 0.5 wt% to 5 wt%. When the binder content is low, the cohesive force of the dry-process negative electrode sheet is low. When the binder content is high, the binder content is too high for insulation within the dry-process negative electrode active layer, resulting in an increase in nanofiber diameter and a decrease in nanofiber distribution uniformity, thereby reducing the number of ion pathways. Therefore, by controlling the content of the binder, the strength and conductivity of the negative electrode sheet can be improved.

[0027] In one embodiment of the present invention, the negative electrode active material further comprises a graphite material. The graphite material comprises, for example, at least one of natural graphite or artificial graphite. Natural graphite comprises at least one of block graphite, flake graphite, or earthy graphite. Artificial graphite comprises at least one of single crystal graphite, polycrystalline graphite, pyrolytic graphite, or graphite fiber. The mass percentage of the silicon material in the negative electrode active material is, for example, 0-100 wt%, and further, for example, 0, 10 wt%, 13 wt%, 26 wt%, 50 wt%, or 100 wt%.

[0028] In one embodiment of the present invention, the silicon content of the negative electrode active material is A wt%, and the binder nanofibers are wrapped around the surface of the negative electrode active material, with the nanofiber area coverage of the negative electrode active material being B%. The dry-process negative electrode active layer satisfies the following relationship: -55 ≤ 0.45 AB ≤ -45. As the silicon content increases, the expansion of the negative electrode active material increases. By increasing the nanofiber area coverage of the negative electrode active material, the expansion suppression effect is enhanced. Therefore, by controlling the relationship between the silicon content of the negative electrode active material and the nanofiber area coverage of the negative electrode active material, the electrode sheet strength can be improved while suppressing expansion.

[0029] In one embodiment of the present invention, the conductive agent is selected from at least one of graphite, graphene, carbon black, carbon fiber, or carbon nanotubes, and the content of the conductive agent in the dry-process negative electrode active layer is, for example, 1wt%-5wt%. The carbon black is, for example, conductive carbon black (Super P), and the carbon fiber includes, for example, at least one of carbon nanofibers (CNF), vapor-grown carbon fiber (VGCF), or vapor-grown carbon nanofibers (VGCNF). In one embodiment of the present invention, the conductive agent includes, for example, carbon black and carbon fiber, and the mass ratio of carbon black to carbon fiber is, for example, 1:(0.2-1.5), or, for example, 1:1.

[0030] In one embodiment of the present invention, the dry-process negative electrode active layer further includes a solid electrolyte, which is selected from at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte, and is further selected from Li7La3Zr2O 12 、Li 13 Al3Ti 17 (PO4)3、Li 10 GeP2S 12 , Li6PS5Cl, Li3InCl6 or Li3YCl6, etc. When the dry-process negative electrode active layer includes a solid electrolyte, the mass ratio of the negative electrode active material, solid electrolyte, conductive agent and binder is, for example, (60-93): (5.5-30): (1-5): (0.5-5). In one embodiment of the present invention, the areal capacity of the dry-process negative electrode sheet is, for example, 1 mAh / cm 2 -10mAh / cm 2 , areal capacity refers to the amount of charge that can be stored per unit area of the electrode, usually expressed as the area carrying capacity per unit area (mAh / cm 2 )express.

[0031] In one embodiment of the present invention, the negative electrode current collector is, for example, carbon-coated copper foil. The carbon coating layer is primarily composed of a conductive carbon material and a binder. The conductive carbon material includes one or more of conductive carbon black, acetylene black, or carbon nanotubes. The binder includes one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), or ethylene-vinyl acetate copolymer. The mass ratio of the conductive carbon material to the binder is, for example, 60-95:5-40. The thickness of the carbon coating layer is, for example, 1 μm to 3 μm, to improve the conductivity between the dry-process negative electrode active layer and the negative electrode current collector. In other embodiments, the current collector may also use other negative electrode current collectors commonly used in the art.

[0032] Based on the above-mentioned dry-process negative electrode sheet, the present invention also proposes a preparation method of a dry-process negative electrode sheet, which at least includes: screening binder particles with a preset median particle size; mixing the negative electrode active material, the conductive agent, and the binder particles to obtain a mixture; fibrillating the mixture to obtain a fibrillated material; cooling the fibrillated material to a target temperature at a preset rate, and applying shear at the same time to obtain an intermediate product; crushing and granulating the intermediate product to obtain a dry-process negative electrode material; forming the dry-process negative electrode material into a film through multi-roll continuous rolling to obtain a dry-process negative electrode active layer; and compounding the dry-process negative electrode active layer with the negative electrode current collector to obtain a dry-process negative electrode sheet.

[0033] In one embodiment of the present invention, the binder is cooled to a brittle point of -40°C and ground using a closed-circuit temperature pulverizing device to obtain a ground binder. The ground binder is sieved through sieves of different apertures to obtain PTFE particles with a preset median particle size. The median particle size D50 refers to the particle size value corresponding to the cumulative volume distribution percentage reaching 50% in the volume distribution curve. In this embodiment, the sieve aperture is, for example, 20μm-270μm, and the preset temperature is, for example, 5°C-20°C. Sieving at a preset temperature can prevent the binder from agglomerating due to excessively high temperature, thereby obtaining solid binder particles, and the preset median particle size of the obtained binder particles is, for example, 20μm-250μm.

[0034] In one embodiment of the present invention, when obtaining a mixture, the negative electrode active material and the conductive agent are first mixed to obtain a premix. Optionally, when the premix also includes a solid electrolyte, at this time, the negative electrode active material, the solid electrolyte and the conductive agent are mixed to obtain a premix, and then the premix and the binder particles are mixed to obtain a mixture. Wherein, when obtaining the premix, the components of the premix are mixed more evenly by stirring, such as the linear speed of stirring can be controlled to be 20m / s-40m / s, the stirring time can be 20min-60min, and the processing temperature can be 5℃-60℃. When obtaining the mixture, the components of the mixture are mixed more evenly by stirring, such as the linear speed of stirring can be controlled to be 5m / s-20m / s, the stirring time can be 20min-60min, and the processing temperature can be 5℃-20℃. When obtaining the premix, the uniform mixing of components other than the binder is improved by increasing the line speed. When obtaining the mixture, the processing temperature (such as the temperature of the mixture during stirring is lower than the stirring temperature of the premix) and the line speed are controlled to avoid problems such as agglomeration or local overheating of the binder particles due to excessively high temperature, thereby avoiding uneven dispersion of the binder particles in the mixture.

[0035] In one embodiment of the present invention, the mixed material is subjected to fibrillation treatment to obtain a fibrillated material. In this embodiment, the fibrillation includes a first stage, a second stage and a third stage. In the first stage, the treatment temperature is, for example, 20°C-40°C, the stirring linear speed is, for example, 20m / s-30m / s, and the stirring time is, for example, 10min-30min; in the second stage, the treatment temperature is, for example, 60°C-80°C, the stirring linear speed is, for example, 40m / s-60m / s, and the stirring time is, for example, 10min-30min; in the third stage, the treatment temperature is, for example, 90°C-120°C, the stirring linear speed is, for example, 60m / s-70m / s, and the stirring time is, for example, 60min-120min. Through the three-stage fibrillation treatment, the step-by-step temperature increase and segmented speed-up shearing of the fibrillation are controlled to prevent excessive breakage or agglomeration of the binder. The high linear speed and time of the third stage are used to maximize the uniformity of the binder, thereby converting the binder particles into nanofibers. The nanofibers form a uniform and dense three-dimensional network structure, thereby improving the strength of the negative electrode sheet obtained later. In this embodiment, due to the limitations of the production process, the d 90 / d 10 ≥1.2.

[0036] In one embodiment of the present invention, after the fibrillation treatment step, the fibrillated material is cooled to a target temperature at a preset rate, for example, the preset rate is 10°C / min-15°C / min, and the target temperature is, for example, 25°C-40°C. During the cooling process, shearing is applied simultaneously to obtain an intermediate product. In this embodiment, the shearing is, for example, pulse shearing, and one pulse shearing includes shearing at 8m / s-10m / s for 4s-6s and shearing at 3m / s-5m / s for 8s-12s. Through rapid cooling and pulse shearing, the fiber structure can be locked to avoid fiber shrinkage caused by natural cooling, thereby stabilizing the size and distribution state of the nanofibers and obtaining a highly uniform binder distribution. At the same time, the d of the nanofibers formed by the binder can be reduced by step-by-step heating, segmented speed-up shearing, rapid cooling and pulse shearing. 90 / d 10 , improving the uniformity of nanofiber diameter.

[0037] In one embodiment of the present invention, the intermediate product is crushed and granulated to obtain a dry negative electrode material, and the dry negative electrode material is formed into a film by multi-roll continuous rolling and thinned to a set surface capacity, for example, 1 mAh / cm 2 -10mAh / cm 2, obtaining a dry-process negative electrode active layer. The dry-process negative electrode active layer is then composited with the negative electrode current collector to form a dry-process negative electrode sheet. For example, the dry-process negative electrode active layer is bonded to the carbon-coated layer of the negative electrode current collector and composited at a temperature of, for example, 20°C to 100°C and a pressure of, for example, 0.8 tons to 1.2 tons. By manipulating the parameters used in preparing the dry-process negative electrode sheet, the components in the dry-process negative electrode active layer are more evenly distributed, and the binder fibrillation effect is enhanced, resulting in a dry-process negative electrode sheet with superior performance, thereby increasing the battery capacity.

[0038] In one embodiment of the present invention, the median particle size of the binder particles is X1 μm, and the diameter d of the nanofibers in the dry-process negative electrode active layer is 50 is X2nm, satisfying the relationship: -5≤0.2X1-X2≤5. That is, when the median particle size of the binder particles is smaller, the diameter of the binder nanofibers in the dry-process negative electrode active layer is finer, the nanofibers are fragile, resulting in reduced cohesion and the inability to suppress the expansion of silicon. When the median particle size of the binder particles is larger, the diameter of the obtained binder nanofibers is larger, the ion path is reduced, and it is not conducive to ion transmission. The fiber network formed by the large-particle binder during the fiberization process is coarser, and there is less physical entanglement between the fibers, which may lead to weaker cohesion. That is, the cohesion first increases and then decreases with the increase of the fiber diameter. The particle size value where the median particle size of the binder particles is less than 50μm is the inflection point of the change in cohesion of the dry-process negative electrode sheet. At the same time, the large-particle binder has poor dispersibility, which easily leads to uneven distribution of the binder. Therefore, by controlling the particle size of the binder particles and allowing the diameter of the binder nanofibers distributed between the negative electrode active materials to be within a set range, it is possible to provide appropriate cohesive force and inhibit the expansion of the negative electrode active materials. Appropriate nanofiber diameters can provide more ion pathways, thereby improving the performance of dry-process negative electrode sheets. At the same time, by controlling the particle size and content of the binder to meet a certain range, dry-process negative electrode sheets with excellent performance can be prepared, which can inhibit the expansion of the negative electrode active materials, reduce problems such as sheet powdering, cracking, and electrode shedding, thereby improving the capacity and cycle performance of all-solid-state batteries.

[0039] In one embodiment of the present invention, the area coverage of the negative electrode active material by the nanofibers is related to the diameter d of the nanofibers in the dry-process negative electrode active layer. 50 The area coverage of the nanofibers on the negative electrode active material decreases with the diameter d of the nanofibers. 50The area coverage of the negative electrode active material by the nanofibers increases with the decrease of the binder content, and the area coverage of the negative electrode active material by the nanofibers is positively correlated with the binder content in the dry negative electrode active layer, that is, when the preparation method and other conditions are consistent, as the binder content increases, the area coverage of the negative electrode active material by the nanofibers increases. When the median particle size D50 of the binder particles is ≥50μm, as the area coverage of the negative electrode active material by the nanofibers increases, the expansion rate is better suppressed. However, when the median particle size D50 of the binder particles is <50μm, the strength and cohesion of the nanofibers need to be considered. As the area coverage of the negative electrode active material by the nanofibers decreases, the expansion rate increases. However, if the strength of the nanofibers is too small, the expansion may not be suppressed. Therefore, it is necessary to combine the uniformity and the d of the nanofibers. 50 and multiple factors such as area coverage to ensure the effect of suppressing expansion.

[0040] In one embodiment of the present invention, the uniformity of the binder in the dry-process negative electrode active layer is, for example, X3%, and the following relationship is satisfied: 96≤0.054X1+X3≤100. This means that the smaller the binder particle size, the finer the diameter of the resulting binder nanofibers, and the higher the uniformity of the binder in the dry-process negative electrode active layer, which can improve ion conductivity. Furthermore, when the binder nanofibers are finer, the specific surface area of the ultrafine nanofiber network is significantly increased, increasing the surface area of the negative electrode active material that can be covered by the binder per unit mass by several times, thereby achieving improved surface coverage of the negative electrode active material. However, the strength of individual nanofibers is weakened, making them susceptible to breakage due to expansion of the negative electrode active material. Therefore, by comprehensively considering the requirements for negative electrode silicon content, binder particle size, nanofiber diameter, and uniformity, the diameter and distribution uniformity of the binder nanofibers can be precisely controlled according to the different silicon contents of the negative electrode active materials, thereby suppressing the expansion of the negative electrode active material and achieving a balance between the strength and performance of the negative electrode sheet.

[0041] In one embodiment of the present invention, when the negative electrode active material is pure silicon, the median particle size of the binder particles is, for example, 40 μm to 60 μm, and the binder content in the dry-process negative electrode active layer is, for example, 2 wt% to 4 wt%. When the negative electrode active material is pure silicon, selecting binder particles with a median particle size of 40 μm to 60 μm can control the diameter of the formed nanofibers, improve cohesion, and increase the uniformity of the binder. Furthermore, by adjusting the binder content, a corresponding area coverage rate can be achieved on the surface of the negative electrode active material, thereby increasing the strength of the nanofibers, improving the cohesion of the dry-process negative electrode sheet, suppressing the expansion of the silicon material, and improving the performance of the negative electrode sheet.

[0042] The present invention also provides an all-solid-state lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, and a solid electrolyte layer, wherein the solid electrolyte layer is disposed between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet is selected from the dry-process negative electrode sheet described above. In the present invention, the all-solid-state battery is, for example, a primary battery or a secondary battery, and the secondary battery is, for example, a pouch cell, a prismatic cell, or a cylindrical cell. The present invention does not impose any specific restrictions on the type or type of the all-solid-state battery.

[0043] In one embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer coated on at least one surface of the positive electrode current collector. The positive electrode current collector is, for example, a surface-treated foil of nickel, titanium, aluminum, silver, stainless steel, or carbon. In addition to foil, the positive electrode current collector may also be in the form of a film, mesh, porous material, foam, or non-woven fabric, among other forms, or any combination thereof.

[0044] In one embodiment of the present invention, the positive electrode active layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder can be selected based on actual needs. In this embodiment, the positive electrode active material includes, for example, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or a lithium-rich manganese-based oxide. The positive electrode conductive agent is, for example, selected from at least one of conductive carbon black, acetylene black, carbon nanotubes, or graphene. The positive electrode binder is, for example, selected from at least one of polyvinylidene fluoride, polyethylene oxide (PEO), polyamide (PA), polyacrylonitrile (PAN), polyacrylate, polyethylene ether, polymethyl methacrylate (PMMA), ethylene-propylene-diene terpolymer (EPDM), or polyhexafluoropropylene.

[0045] In one embodiment of the present invention, the positive electrode active layer further includes a solid electrolyte, which is selected from at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte, and is further selected from Li7La3Zr2O 12 、Li 13 Al3Ti 17 (PO4)3、Li 10 GeP2S 12, Li6PS5Cl, Li3InCl6, or Li3YCl6. The mass ratio of the positive electrode active material, solid electrolyte, positive electrode conductive agent, and positive electrode binder is, for example, (64-93.9): (5-30): (1-5): (0.1-1). The positive electrode active layer can be prepared by a dry process or a wet process, which is not specifically limited in this application.

[0046] In one embodiment of the present invention, the solid electrolyte layer includes a solid electrolyte, and the solid electrolyte is selected from at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte, and is selected from Li7La3Zr2O 12 、Li 13 Al3Ti 17 (PO4)3、Li 10 GeP2S 12 , Li6PS5Cl, Li3InCl6 or Li3YCl6, etc. The solid electrolyte is pressed, for example, at 90MPa-150MPa to obtain a solid electrolyte layer. The dry-process negative electrode sheet, the solid electrolyte layer and the positive electrode sheet are sequentially placed into a mold for assembly. After assembly, the pressure is applied to 100 MPa and the nut at the top of the column is tightened to a constant pressure to obtain an all-solid-state lithium-ion battery. The assembly process is completed under an argon atmosphere or in a vacuum. In this embodiment, when assembling an all-solid-state lithium-ion battery, for example, an alloy comprising indium, lithium, aluminum or at least two of the above metals is used as a counter electrode to test the performance of the negative electrode sheet.

[0047] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0048] Example 1 Screening of binder particles: PTFE was cooled to its brittle point of -40°C and ground using a closed-circuit, temperature-controlled pulverization device. The D50 value after grinding was controlled to ≤250μm to obtain the ground PTFE. The PTFE was screened through a 60μm sieve, and the PTFE particles that passed through the sieve were collected. The PTFE particles that passed through the sieve were then screened through a 40μm sieve, and the PTFE particles that did not pass through the sieve were collected. The median particle size of the PTFE was 50μm. The screening temperature was 10°C. The PTFE was sourced from Daikin Fluorochemicals (China) Co., Ltd., model F106C, with a molecular weight of 6000 kg / mol.

[0049] Preparation of dry-process negative electrode sheets: Pure silicon, Li6PS5Cl, Super p, and VGCF were mixed to obtain a premix, stirred at a linear speed of 30 m / s for 30 minutes, and treated at a temperature of 25°C to obtain a premix. The premix was then mixed with binder particles to obtain a mixture, stirred at a linear speed of 15 m / s for 30 minutes, and treated at a temperature of 10°C to obtain a mixture. The mixture was subjected to a fiberization treatment to obtain a fibrillated material. The first stage was treated at a temperature of 25°C, a linear speed of 20 m / s, and a stirring time of 10 minutes; the second stage was treated at a temperature of 80°C, a linear speed of 50 m / s, and a stirring time of 10 minutes; and the third stage was treated at a temperature of 120°C, a linear speed of 70 m / s, and a stirring time of 90 minutes. After the fibrillation is completed, the material is quenched to 25°C at a rate of 15°C / min and pulse shear is applied at the same time. One pulse cycle is 10m / s shear for 5s and 5m / s shear for 10s. The fibrillated material is crushed and granulated to obtain a dry negative electrode material. The dry negative electrode material is formed into a film by multi-roll continuous rolling and thinned to 4mAh / cm 2 The surface capacity is obtained to obtain a dry-process negative electrode active layer, and the dry-process negative electrode active layer is compounded with a carbon-coated aluminum foil to obtain the high-performance dry-process negative electrode plate, and the uniformity of the binder in the dry-process negative electrode active layer is 94%.

[0050] The pure silicon is sourced from Guangzhou Hongwu Materials Technology Co., Ltd., model A212. The solid electrolyte is Li6PS5Cl, sourced from Shandong Xinjieneng Lithium Battery Co., Ltd., model LPSCl. The conductive agent is a 1:1 ratio of Super P and VGCF. Super P is sourced from Tianjin Youmeng Chemical Technology Co., Ltd., and VGCF is sourced from Showa Denko Co., Ltd., model VGCF-H. The carbon-coated copper foil is coated with a 1μm thick carbon layer composed of conductive carbon black and polyacrylic acid in a mass ratio of 8:2. The negative electrode active material, Li6PS5Cl, Super P, VGCF, and PTFE are in a mass ratio of 70:24:1.5:1.5:3.

[0051] Counter electrode: Lithium indium alloy sheet was selected as the counter electrode.

[0052] Preparation of solid electrolyte layer: 1000 mg of Li6PS5Cl powder was placed in a mold with a diameter of 10 mm and pressurized to 100 MPa to obtain a solid electrolyte layer.

[0053] Battery Preparation: The dry-process anode electrode, solid electrolyte layer, and counter electrode are sequentially placed into a mold for assembly. After assembly, the pressure is applied to 100 MPa and the nuts at the top of the columns are tightened to maintain constant pressure, resulting in an all-solid-state lithium-ion battery. The assembly process is completed in an argon-filled glove box. The diameter of the dry-process anode electrode and counter electrode is 10 mm.

[0054] Example 2 The binder screening process was adjusted to obtain a PTFE median particle size of 75 μm. The negative electrode active material was a silicon-carbon material with a silicon content of 50%, sourced from Changzhou Silicon Source New Energy Materials Co., Ltd., model number NSC9100. The remaining battery preparation steps (including the solid electrolyte layer preparation process and the counter electrode) were the same as in Example 1.

[0055] Example 3 The PTFE obtained by adjusting the screening process of the binder is 100 μm in median particle size, and the negative electrode active material is a silicon-carbon material with a silicon content of 26%, which is sourced from Guangdong Candlelight New Energy Technology Co., Ltd., and the model is silicon-carbon material 1200. The other preparation steps of the battery are the same as those in Example 1.

[0056] Example 4 The PTFE obtained by adjusting the screening process of the binder has a median particle size of 155 μm, and the negative electrode active material is a silicon-carbon material with a silicon content of 13%, which is sourced from Guangdong Candlelight New Energy Technology Co., Ltd. and is model silicon-carbon material 650. The other battery preparation steps are the same as those in Example 1.

[0057] Example 5 The sieving process of the binder was adjusted to obtain a PTFE with a median particle size of 250 μm, and the negative electrode active material was graphite, which was obtained from BTR New Materials Group Co., Ltd., model AGP-9. The other battery preparation steps were the same as in Example 1.

[0058] Example 6 The negative electrode active material is a silicon-carbon material with a silicon content of 50%, sourced from Changzhou Silicon Source New Energy Materials Co., Ltd., model NSC9100. The other battery preparation steps (including the solid electrolyte layer preparation process and the counter electrode, etc.) are the same as in Example 1.

[0059] Example 7 The content of the binder in the dry-process negative electrode active layer was adjusted to 2 wt %, and the proportions of the other components remained unchanged. The other steps in preparing the battery were the same as those in Example 4.

[0060] Example 8 The content of the binder in the dry-process negative electrode active layer was adjusted to 4 wt %, and the proportions of the other components remained unchanged. The other steps in preparing the battery were the same as those in Example 4.

[0061] Example 9 The binder screening process was adjusted to obtain a PTFE median particle size of 75 μm, and the binder content in the dry-process negative electrode active layer was adjusted to 5 wt %, while the proportions of the other components remained unchanged. The other battery preparation steps were the same as in Example 1.

[0062] Example 10 The screening process of the binder was adjusted to obtain a PTFE with a median particle size of 100 μm. The other preparation steps of the battery were the same as those in Example 1.

[0063] Example 11 The binder has a molecular weight of 8000 kg / mol and is sourced from Daikin Fluorochemical, model F121. The other steps in preparing the battery are the same as those in Example 4.

[0064] Example 12 The binder was replaced with ethylene-vinyl acetate copolymer, which was sourced from DuPont, USA, and was model Elvax 40W. The other steps in preparing the battery were the same as those in Example 4.

[0065] Comparative Example 1 Adjust the screening process of the binder, and the median particle size of the PTFE obtained is 50μm, and the negative electrode active material is a silicon-carbon material with a silicon content of 13%, which is sourced from Guangdong Candlelight New Energy Technology Co., Ltd., and the model is silicon-carbon material 650. When obtaining the premix, the linear velocity of stirring is 30m / s, the stirring time is 30min, and the processing temperature is 25°C. When obtaining the mixture, the linear velocity of stirring is 15m / s, the stirring time is 30min, the processing temperature is 10°C, and a mixture is obtained. The mixture is subjected to fiberization to obtain a fibrillated material, with a linear velocity of stirring of 50m / s, a stirring time of 20min, and a third-stage processing temperature of 100°C. After the fiberization is completed, it is naturally cooled to 25°C, and during the cooling process, no pulse shear is applied. The preparation steps of other batteries are the same as those in Example 1.

[0066] Comparative Example 2 The screening process of the binder was adjusted to obtain a PTFE with a median particle size of 75 μm. The other preparation steps of the battery were the same as those in Comparative Example 1.

[0067] Comparative Example 3 The screening process of the binder was adjusted to obtain a PTFE with a median particle size of 250 μm. The other preparation steps of the battery were the same as those in Comparative Example 1.

[0068] Comparative Example 4 The binder was not subjected to screening, the median particle size of PTFE was 400 μm, and the other preparation steps of the battery were the same as those of Comparative Example 1.

[0069] Comparative Example 5 The binder was not subjected to screening, the median particle size of PTFE was 400 μm, and the negative electrode active material was pure silicon, which was sourced from Guangzhou Hongwu Material Technology Co., Ltd., model A212. Other battery preparation steps were the same as those in Comparative Example 1.

[0070] Comparative Example 6 The content of the binder in the dry-process negative electrode active layer was adjusted to 10 wt %, and the proportions of the other components remained unchanged. The other steps in preparing the battery were the same as those in Comparative Example 5.

[0071] Comparative Example 7 The binder has a molecular weight of 2000 kg / mol and is sourced from Daikin Fluorochemical, model F104. The other steps in preparing the battery are the same as those in Example 4.

[0072] In the present invention, all unlabeled reagents and raw materials used in Examples 1-12 and Comparative Examples 1-7 are commercially available. Performance tests were performed on the dry-process negative electrode sheets and all-solid-state lithium-ion batteries in Examples 1-12 and Comparative Examples 1-7, and the test results were recorded.

[0073] In one embodiment of the present invention, to determine the uniformity of the binder in the dry-process negative electrode active layer, Fourier transform infrared spectroscopy (FTIR) can be used to confirm the specific type of binder in the electrode. For example, the binder type can be determined by directly examining the electrode surface or scraping a powder sample based on the peak positions of characteristic functional groups. After determining the binder type, the characteristic chemical bonds of the binder are selected as the target for characterization. Energy dispersive X-ray spectroscopy (EDS) is used to observe the uniformity of the binder on the surface of the dry-process negative electrode. Specifically, increasing the magnification to 5000x allows for optimal observation of the uniformity of the binder distribution. The specific process involves first selecting the central area of the electrode as the observation target. Five 50μm x 50μm areas are randomly selected, arranged along the same line with a center-to-center spacing of 500μm. EDS surface scanning is used to determine the proportions of different elements, and the characteristic element of the binder is selected as the result for that area, such as F for PTFE. Obtain the ratio of the mean difference of the F element content in these five regions to the average, and subtract this ratio from 1. The result obtained is used as the uniformity of the binder within the dry-process negative electrode sheet of a sample. Five dry-process negative electrode sheets obtained from the same embodiment or comparative example are selected as parallel samples. The binder uniformity data for these five parallel samples is obtained, and the average value is recorded as the binder uniformity for that embodiment or comparative example.

[0074] In one embodiment of the present invention, the binder content is obtained by testing the characteristic element absorption peak of the binder by Fourier transform infrared spectroscopy. For example, PTFE has a unique infrared absorption peak (such as 1200 cm -1 -1300cm -1FTIR can be used to quantitatively analyze the PTFE content, specifically the C-F bond vibration peak at the center of the FTIR spectrum. Procedure: Grind the dry-process anode active layer sample into a powder, mix the powder with KBr, and press the pellet. Alternatively, directly use ATR (attenuated total reflectance) mode to collect the sample's infrared spectrum and quantitatively analyze the PTFE content in the dry-process anode active layer using a calibration curve or peak area integration.

[0075] In one embodiment of the present invention, the binder exists in the form of nanofibers in the dry-process negative electrode sheet, and the diameter of the nanofibers is tested by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). The negative electrode sheet is placed in a test device, and at a maximum magnification of 50,000, fibers with a length greater than 5 μm are taken. A point value width is taken every 200 nm along the fiber axis, and the average value of the width of each point value is obtained as the diameter of the fiber. 100 fibers are randomly selected and arranged from small to large in diameter to obtain the diameters at the 10th, 50th, and 90th positions, which are recorded as d 10 d 50 d 90 .

[0076] Five dry-process negative electrode sheets obtained in the same embodiment or comparative example were selected as parallel samples. The d value of the nanofiber binder of each parallel sample was obtained as above. 10 d 50 and d 90 , and obtain d for 5 parallel samples 50 and d 90 / d 10 The average value is taken as the d value of this embodiment or comparative example. 50 and d 90 / d 10 Numeric value.

[0077] In one embodiment of the present invention, after dry-process preparation and fibrillation of the binder, the area coverage of the negative electrode active material by nanofibers is primarily measured using microscopic imaging combined with elemental analysis techniques: Five 50 μm × 50 μm observation areas with a spacing of ≥100 μm are randomly selected from the center of the negative electrode plate. SEM topography imaging and EDS elemental surface scanning (for characteristic elements of the binder, such as F in PTFE) are simultaneously performed on each area. Image processing software is used to measure the total projected area of all active material particles within the area and the area covered by the characteristic element signal on the surface. The coverage of each area is calculated as (binder coverage area / total active material area × 100%). The arithmetic average of the coverage rates of the five areas is ultimately used as the nanofiber area coverage of the electrode plate. The average of the nanofiber area coverage of the negative electrode active material in the five parallel sample test areas is the area coverage of the nanofibers on the negative electrode active material for that electrode plate.

[0078] In one embodiment of the present invention, in order to obtain normal temperature cycle performance, the all-solid-state lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1-7 were subjected to long-cycle charge and discharge after constant capacity at 25°C, and the number of normal temperature cycle laps was measured. The test conditions are as follows: a long-cycle charge and discharge test is performed after the battery is constant capacity is set, and the first cycle constant capacity discharge specific capacity is recorded during the process. The test is terminated when the battery capacity reaches 80% (80% State of Health, 80% SOH) of the first cycle capacity, and the normal temperature cycle laps are obtained. The test voltage range is -0.615V-1.4V, the constant capacity current is 0.6mA, and the normal temperature cycle test rate is 0.3C.

[0079] Table 1. Parameters of dry-process negative electrode sheets and battery performance in Examples 1-10 and Comparative Examples 1-6

[0080] As shown in Table 1, it can be seen from the comparison of Examples 1-5 that when the silicon content of the negative electrode active material is different, under the same preparation conditions, the binder particles of different particle sizes are matched, and as the particle size of the binder particles increases, the d 50 As the diameter of the nanofiber increases, the uniformity decreases, and the area coverage of the negative electrode active material by the nanofiber decreases as the nanofiber diameter increases. Specifically, the smaller the nanofiber diameter, the lower the nanofiber strength and the higher the coverage. The coverage is positively correlated with the ability to inhibit silicon expansion. Therefore, when the silicon content changes, by controlling the D50 of the binder particles, the cohesion and coverage of the nanofiber diameter are balanced, thus suppressing the expansion of the negative electrode active material and ensuring the battery's cycling performance while improving the first-cycle charge capacity.

[0081] Please refer to Table 1. By comparing Examples 2 and 6, it can be seen that when the silicon content is 50%, under the same preparation conditions, when the median particle size D50 of the binder particles is reduced to 50 μm, the diameter of the nanofibers can be reduced, the uniformity and the area coverage of the nanofibers on the negative electrode active material can be increased, and the cohesive force of the nanofibers obtained at this time is sufficient, thereby improving the cycle stability, achieving high uniformity, and improving the capacity to a certain extent.

[0082] As shown in Table 1, by comparing Examples 4, 7-8, it can be seen that when the silicon content in the negative electrode active material is the same, under the same preparation conditions, only the binder content is changed. As the binder content increases, the d 50 Increase, thereby the uniformity of binder fiber dispersion decreases, and the uniformity of the binder in the negative electrode sheet is reduced, but the area coverage of the nanofibers on the negative electrode active material increases, resulting in a decrease in the first-cycle charge capacity, but an increase in the cycle performance. Therefore, under the premise of the same silicon content, the binder content is controlled to achieve a balance between the first-cycle charge capacity and the cycle performance.

[0083] As shown in Table 1, a comparison of Examples 1, 9, and 10 shows that, under identical preparation conditions, while maintaining consistent silicon content in the negative electrode active material, varying both the median particle size (D50) and content of the binder particles simultaneously yielded similar binder uniformity. However, this resulted in an increase in the diameter of the binder nanofibers, a decrease in the nanofiber area coverage of the negative electrode active material, and failure to meet the requirement of -55 ≤ 0.45 AB ≤ -45. This weakened expansion suppression capability and, consequently, a rapid decline in cycling performance. Therefore, a balance of nanofiber diameter, uniformity, and coverage was crucial to improving battery cycling performance.

[0084] As shown in Table 1, by comparing Example 4 with Comparative Examples 1-4, it can be seen that when the silicon content and the binder content in the negative electrode active material are the same, and the preparation method does not adopt the preparation method provided by the present application, even if the median particle size D50 of the binder particles is reduced, the d 50 d 90 / d 10 The larger the value, the lower the uniformity of the binder is, and the smaller the value, the lower the area coverage of the negative electrode active material by the nanofibers is, and the smaller the value, the lower the area coverage of the negative electrode active material is, and the smaller the value, the lower the area coverage of the negative electrode active material is, and the smaller the value, the lower the area coverage of the negative electrode active material is, which deteriorates the performance of the battery. As the median particle size of the binder particles increases, the battery performance will further deteriorate.

[0085] As shown in Table 1, by comparing Example 1 with Comparative Examples 5-6, it can be seen that when the silicon content in the negative electrode active material is the same, the median particle size of the binder particles is a conventional particle size and the preparation method does not adopt the preparation method provided by this application, when the binder content is low, the area coverage of the nanofibers on the negative electrode active material is low and does not meet the requirement of -55≤0.45AB≤-45, and the battery cycle performance plummets. Increasing the binder content increases the d 50 The increase in the uniformity of the nanofibers resulted in a decrease in the first-cycle charge capacity. The area coverage of the nanofibers on the negative electrode active material increased compared to Comparative Example 5, resulting in a slight improvement in the cycling performance, but overall it was poor. Therefore, by controlling the median particle size of the binder particles and the preparation process, while ensuring the mechanical stability of the negative electrode sheet, the efficient transport of lithium ions and electrons was promoted, thereby improving the performance of the negative electrode sheet.

[0086] Table 2. Dry-process negative electrode plate parameters and battery performance in Examples 4, 11 and Comparative Example 7

[0087] As shown in Table 2, by comparing Examples 4, 11 and Comparative Example 7, it can be seen that under the same preparation process, when the D50 and content of the binder particles are the same, only the molecular weight of the binder is changed, the binder nanofiber d50 d 90 / d 10 As the molecular weight of the binder increases, the strength of the obtained nanofibers increases, thereby improving the performance of the negative electrode sheet and, therefore, the performance of the battery.

[0088] Table 3. Some parameters of dry-process negative electrode sheets and battery performance in Examples 4 and 12

[0089] Please refer to Table 3. By comparing Example 4 and Example 12, it can be seen that when different binders are selected, the particle size, content and preparation method of the binders are the same, the nanofiber d 50 d 90 / d 10 The first-cycle discharge specific capacity and cycle performance of batteries with similar uniformity are not much different, indicating that when selecting different binders, by controlling the particle size and content of the binder, a negative electrode sheet with higher uniformity can be obtained, thereby improving the performance of the battery.

[0090] The present invention also provides an electronic device, which includes at least one of the above-mentioned all-solid-state lithium-ion batteries, and the all-solid-state lithium-ion battery is used to provide electrical energy. The electronic device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and an electric tool. In one embodiment of the present invention, the vehicle is, for example, a new energy vehicle, which may be a pure electric vehicle, a hybrid electric vehicle, or an extended-range vehicle. The spacecraft includes airplanes, rockets, space shuttles, and spacecrafts, and the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys. The electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The electronic device includes the above-mentioned all-solid-state lithium-ion battery, and therefore includes the advantages of the above-mentioned all-solid-state lithium-ion battery, which will not be elaborated on here.

[0091] In summary, the present invention proposes a dry-process negative electrode sheet and its preparation method and application. By improving the uniformity of the binder in the dry-process negative electrode active layer, the expansion of the negative electrode active material can be suppressed. Under the premise of ensuring the mechanical stability of the negative electrode sheet, the effective transmission of lithium ions and electrons can be promoted, the performance of the negative electrode sheet can be improved, the risk of shedding and short circuit of the dry-process negative electrode active layer can be reduced, and the safety performance can be improved. The diameter of the binder nanofibers can be controlled, and the thickness distribution of the nanofiber diameter can be controlled to ensure the strength and sufficient cohesion of the three-dimensional nano-network structure, which can suppress the expansion problem of the negative electrode active material and improve the ion transmission capacity. By controlling the particle size and content of the binder to meet a certain range, the expansion problem of the negative electrode active material can be suppressed, and the problems of sheet de-powdering, cracking, and electrode shedding can be reduced, thereby improving the capacity and cycle performance of the all-solid-state battery. It can comprehensively consider the requirements of negative electrode silicon content, binder particle size, nanofiber diameter and uniformity, and accurately regulate the diameter and distribution uniformity of the binder nanofiber according to the negative electrode active materials with different silicon contents, thereby inhibiting the expansion of the negative electrode active materials and achieving a balance between the strength and performance of the negative electrode sheet.

[0092] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as the technical solutions formed by the mutual replacement of the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0093] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A dry-process negative electrode sheet, characterized in that: At least: negative electrode current collector; A dry-process negative electrode active layer is provided on at least one surface along the thickness direction of the negative electrode current collector, wherein the dry-process negative electrode active layer comprises a negative electrode active material, a conductive agent, and a binder, wherein the uniformity of the binder in the dry-process negative electrode active layer is 85%-96%; The negative electrode active material includes silicon material, which includes but is not limited to silicon, silicon-carbon material and silicon-oxygen negative electrode material.

2. The dry-process negative electrode sheet according to claim 1, characterized in that: The binder exists in the dry-process negative electrode active layer in the form of nanofibers, and the diameter of the nanofibers is d 50 10nm-50nm, d 90 / d 10 ≤1.5, where d 50 is the diameter of the nanofibers when the number of nanofibers increases from small to large to 50%, d 10 is the diameter of the nanofibers when the number of nanofibers from small to large accumulates to 10%, d 90 It is the diameter when the cumulative number of the nanofiber diameters from small to large reaches 90%.

3. The dry-process negative electrode sheet according to claim 2, characterized in that: The silicon content of the negative electrode active material is Awt%; the nanofibers of the binder cover the surface of the negative electrode active material, and the area coverage of the nanofibers on the negative electrode active material is B%. The dry-process negative electrode active layer satisfies the following relationship: -55≤0.45AB≤-45.

4. The dry-process negative electrode sheet according to claim 1, characterized in that: The content of the binder in the dry-process negative electrode active layer is 0.5 wt % to 5 wt %.

5. The dry-process negative electrode sheet according to claim 1, characterized in that: The negative electrode active material further includes a graphite material, and the graphite material includes at least one of natural graphite and artificial graphite.

6. The dry-process negative electrode sheet according to claim 5, characterized in that: The mass percentage of the silicon material to the negative electrode active material is 0-100 wt %.

7. The dry-process negative electrode sheet according to claim 1, characterized in that: The binder comprises one or more combinations of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, ethylene-vinyl acetate copolymer, polypropylene, polyethylene, ethylene-octene copolymer or polyimide; And / or, the conductive agent is selected from at least one of graphite, graphene, carbon black, carbon fiber and carbon nanotubes.

8. A method for preparing a dry-process negative electrode sheet, characterized in that: At least the following steps are included: Sieving binder particles with a preset median particle size; mixing the negative electrode active material, the conductive agent and the binder particles to obtain a mixed material; performing a fibrillation treatment on the mixed material to obtain a fibrillated material; Cooling the fibrillated material to a target temperature at a preset rate while applying shear to obtain an intermediate product; Crushing and granulating the intermediate product to obtain a dry-process negative electrode material; The dry-process negative electrode material is formed into a film by continuous rolling with multiple rollers to obtain a dry-process negative electrode active layer; The dry-process negative electrode active layer is compounded with the negative electrode current collector to obtain a dry-process negative electrode sheet.

9. The method for preparing a dry-process negative electrode sheet according to claim 8, characterized in that: The preset median particle size of the binder particles is X1 μm, and the diameter d of the nanofibers in the dry-process negative electrode active layer is 50 is X2 nm, satisfying the following relationship: -5≤0.2X1-X2≤5; The binder particles have a preset median particle size of 20 μm to 250 μm.

10. The method for preparing a dry-process negative electrode sheet according to claim 9, characterized in that: The uniformity of the binder in the dry-process negative electrode active layer is X3%, satisfying the following relationship: 96≤0.054X1+X3≤100.

11. The method for preparing a dry-process negative electrode sheet according to claim 8, characterized in that: When the negative electrode active material is pure silicon, the median particle size of the binder particles is 40 μm-60 μm, and the content of the binder in the dry-process negative electrode active layer is 2 wt %-4 wt %.

12. The method for preparing a dry-process negative electrode sheet according to claim 8, characterized in that: Sieving the binder particles at a preset temperature, wherein the preset temperature is 5° C.-20° C.; The fibrillation includes a first stage, a second stage and a third stage. In the first stage, the treatment temperature is 20°C-40°C, the stirring linear speed is 20m / s-30m / s, and the stirring time is 10min-30min; in the second stage, the treatment temperature is 60°C-80°C, the stirring linear speed is 40m / s-60m / s, and the stirring time is 10min-30min; in the third stage, the treatment temperature is 90°C-120°C, the stirring linear speed is 60m / s-70m / s, and the stirring time is 60min-120min; The preset rate is 10°C / min-15°C / min, and the target temperature is 25°C-40°C; During the cooling process, pulse shearing is applied, wherein one pulse shearing comprises shearing at 8 m / s-10 m / s for 4 s-6 s and shearing at 3 m / s-5 m / s for 8 s-12 s.

13. An all-solid-state lithium-ion battery, characterized in that: At least: Positive electrode; A negative electrode sheet, selected from the dry-process negative electrode sheet according to any one of claims 1 to 7, or a dry-process negative electrode sheet obtained by the preparation method according to any one of claims 8 to 12; The solid electrolyte layer is arranged between the positive electrode sheet and the negative electrode sheet.

14. The all-solid-state lithium-ion battery according to claim 13, wherein: The negative electrode plate further includes a solid electrolyte, which is selected from at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte.

15. An electronic device, characterized in that: An all-solid-state lithium-ion battery comprising the all-solid-state lithium-ion battery according to any one of claims 13 to 14.

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