A negative electrode sheet, a full solid-state battery, and an electric device

Abstract

This invention provides a negative electrode sheet, an all-solid-state battery, and an electrical device, specifically relating to the field of battery technology. The negative electrode sheet includes a negative current collector, a first active material layer, and a second active material layer. The first active material layer is disposed on at least one side of the negative current collector and includes a silicon-based material, a first conductive agent, and a binder. The second active material layer is disposed on the side of the first active material layer opposite to the negative current collector and includes a silicon-based material, a second conductive agent, a binder, and a high-entropy sulfide solid electrolyte. The negative electrode sheet of this invention can effectively improve the cycle performance and fast-charging performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to a negative electrode sheet, an all-solid-state battery, and an electrical device. Background Technology

[0002] With the rapid iteration of new energy vehicles and portable electronic devices, the market has placed increasingly stringent demands on the energy density and fast-charging performance of lithium-ion batteries. The theoretical specific capacity of traditional graphite anodes (372 mAh / g) is gradually becoming insufficient to meet the development requirements of next-generation batteries. Silicon-based anode materials, with a theoretical specific capacity as high as 4200 mAh / g, are widely recognized as highly promising candidates for next-generation lithium-ion battery anode materials.

[0003] However, silicon-based anodes experience dramatic volume expansion exceeding 300% during charging and discharging, which can easily lead to pulverization and cracking of the electrode structure, damaging the overall integrity of the electrode. This causes the solid electrolyte interphase (SEI) film to repeatedly rupture and regenerate, not only consuming electrolytes and active materials but also exacerbating the increase in interfacial impedance, resulting in poor battery cycle stability and rate performance, which severely restricts the industrial application of silicon-based anodes.

[0004] To improve the electrochemical performance of silicon-based anodes, various optimization strategies have been proposed in existing technologies, including: composite structure design, which involves combining silicon with carbon materials such as graphite, carbon nanotubes, or graphene to mitigate volume expansion through the buffering effect of the carbon phase, while simultaneously improving the electronic conductivity of the electrode; binder system optimization, which employs highly elastic or self-healing binders to enhance the bonding force between the various components of the electrode and maintain the stability of the electrode structure during cycling; electrolyte modification, which introduces solid or quasi-solid electrolytes to replace traditional liquid electrolytes, thereby strengthening the stability of the electrode-electrolyte interface; and electrode structure engineering, which involves constructing porous, core-shell, or gradient electrode structures to reserve buffer space for volume expansion while optimizing ion transport pathways.

[0005] While the aforementioned strategies have mitigated some of the individual performance defects of silicon-based anodes, current technologies still struggle to achieve a harmonious balance between high specific capacity, long cycle life, and excellent fast-charging capability. This is especially true under high-rate charge-discharge conditions, where issues such as sluggish ion / electron transport kinetics, persistently high interface impedance, and susceptibility to electrode structural failure become more pronounced in silicon-based anodes. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a negative electrode sheet, an all-solid-state battery and an electrical device to improve the technical problems of poor cycle stability and poor rate performance of silicon-based negative electrodes.

[0007] To achieve the above and other related objectives, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector, a first active material layer and a second active material layer, the first active material layer being disposed on at least one side of the negative current collector, the first active material layer comprising a silicon-based material, a first conductive agent and a binder; the second active material layer being disposed on the side of the first active material layer opposite to the negative current collector, the second active material layer comprising a silicon-based material, a second conductive agent, a binder and a high-entropy sulfide solid electrolyte.

[0008] In one embodiment of the present invention, the chemical formula of the high-entropy sulfide solid electrolyte is: Li 4±x-y A y (M1 a M2 b M3 c S4 δ X δ In the formula, 0≤x≤1.5, 0≤y≤1.5, and y≤4±x; 0.4≤a≤0.8, 0.1≤b≤0.4, 0.1≤c≤0.3, a+b+c=1, 0≤δ≤1; A is selected from one or two of Na and K; M1 is selected from one or more of Ge, Sn, Si, P, As, and B; M2 is selected from one or more of Sb, Nb, Ta, V, Mo, W, Ti, Zr, Hf, and Re; M3 is selected from one or more of Al, Ga, In, Bi, Pb, Mg, Ca, Zn, Cd, Y, Sc, La, Ba, Sr, Ce, and Sm; X is selected from one or more of O, Se, and Te.

[0009] In one embodiment of the present invention, the first active material layer further includes a high-entropy sulfide solid electrolyte, wherein the mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, first conductive agent and binder in the first active material layer is (85~98):(0~10):(0.1~3):(1~5); and the mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, second conductive agent and binder in the second active material layer is (45~84):(10~30):(5~20):(1~5).

[0010] In one embodiment of the present invention, the D50 of the high-entropy sulfide solid electrolyte is 500nm≤D50≤5μm.

[0011] In one embodiment of the present invention, the D50 of the high-entropy sulfide solid electrolyte is 1μm≤D50≤3μm.

[0012] In one embodiment of the present invention, the compaction density of the first active material layer is 1 g / cm³. 3 ~1.3g / cm 3The compaction density of the second active material layer is 0.7 g / cm³. 3 ~1g / cm 3 .

[0013] In one embodiment of the present invention, the first conductive agent includes one or more of carbon black, graphite, carbon fiber and carbon nanotube; the second conductive agent includes one or more of graphene, graphite and MXene.

[0014] In one embodiment of the present invention, the second conductive agent is a composition of graphite and graphene, or a composition of graphite and MXene.

[0015] In one embodiment of the present invention, the silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite material, and silicon alloy.

[0016] In one embodiment of the present invention, the D50 of the silicon-based material in the first active material layer is 30 nm to 10 μm; the D50 of the silicon-based material in the second active material layer is 10 nm to 12 μm.

[0017] The present invention also provides an all-solid-state battery, the all-solid-state battery comprising: a positive electrode, a solid electrolyte layer and a negative electrode of any one of the above.

[0018] The present invention also provides an electrical device comprising the above-described all-solid-state battery.

[0019] The beneficial effects of the present invention are as follows: The negative electrode sheet provided by the present invention adopts a double-layer silicon-based negative electrode material and introduces a high-entropy sulfide solid electrolyte with high ionic conductivity, excellent interfacial compatibility and structural stability in the second active material layer (surface layer). This can effectively solve the problems of high ion transport impedance, structural failure caused by volume expansion and poor contact with electrolyte interface in traditional silicon-based negative electrodes during fast charging. Thus, the battery can achieve excellent performance of high efficiency fast charging, high first efficiency and long cycle stability under low stacking pressure (≤5MPa).

[0020] Soft high-entropy sulfide solid electrolytes exhibit excellent interfacial wettability with silicon-based materials, effectively filling the gaps between active particles to form a continuous solid-solid ion conduction network, thereby significantly reducing interfacial impedance. Simultaneously, the high-entropy sulfide solid electrolytes, through multi-metal site modulation of their electronic structure, can significantly improve their reduction stability at 0.01V vs. Li. + The Li-type electrode maintains interface stability at its potential, preventing continuous interface degradation and thus improving the initial coulombic efficiency of the battery, laying the foundation for a long cycle life. Furthermore, its multi-metal composition can undergo slight surface remodeling or form a flexible interface layer in the early stages of electrochemical cycling, adaptively encapsulating silicon particles to achieve dynamic wetting and further reducing initial interfacial contact resistance.

[0021] Furthermore, this invention forms a negative electrode active material layer with gradient porosity by adjusting the compaction density of the first and second active material layers. This gradient porosity structure works synergistically with the high-entropy sulfide electrolyte with high ionic conductivity in the active material layer, enabling the battery to achieve high-efficiency fast charging of 4C or higher even under low stacking pressure conditions of ≤5MPa (which is much lower than the >10MPa required by traditional solid-state batteries), and the fast charging capacity retention rate is ≥60%, effectively breaking through the bottleneck of traditional silicon-based negative electrode fast charging performance being limited by stacking pressure.

[0022] Furthermore, the second active material layer of the negative electrode sheet of this invention maintains a highly efficient ion and electron transport network by reducing silicon content and increasing electrolyte and conductive agent content. At the same time, the high-entropy sulfide electrolyte itself has excellent structural stability. During the repeated expansion / contraction of the silicon negative electrode, it is not prone to cracking or pulverization due to local stress concentration, and can always maintain the continuity of ion channels, ultimately achieving a long battery cycle life, with a capacity retention rate of >80% after 500 cycles. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] In the attached diagram:

[0025] Figure 1 This is a schematic diagram of the structure of a negative electrode sheet provided in an embodiment of the present invention.

[0026] Figure label: 1. Negative electrode current collector; 2. First active material layer; 3. Second active material layer. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0028] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0030] In this article, the terms "multiple," "various," and "multiple times" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0031] In this document, terms such as “preferred,” “ideal,” “further,” “even more,” and “particularly” are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0032] In this document, when referring to numerical ranges, unless otherwise specified, the distribution of selectable values ​​within a numerical range is considered continuous, including the two endpoints of the range (i.e., the minimum and maximum values), and every value between these two endpoints. When multiple numerical ranges are provided to describe a feature or property, these numerical ranges can be combined.

[0033] The terms or phrases used in this article have the following meanings: D50, also known as median particle size, means: In the particle size distribution of a volume-based particle group, the particle size corresponding to a cumulative distribution percentage of 50% is that half of the particles in the sample have a particle size less than or equal to this value, and the other half have a particle size greater than or equal to this value.

[0034] Currently, silicon-based anodes face multiple bottlenecks: a single silicon-carbon composite structure struggles to balance high capacity and fast-charging performance; while high silicon content significantly improves the specific capacity of the anode, it exacerbates volume expansion during charge and discharge, leading to a substantial decrease in cycle stability; conversely, reducing silicon content, while contributing to structural stability, sacrifices battery energy density. Meanwhile, the conductive network constructed from traditional graphite exhibits particularly prominent issues of long lithium-ion diffusion paths and high interfacial impedance under high-rate charge and discharge conditions, severely limiting the battery's fast-charging capability and creating a stark contradiction with the high-power characteristics sought in silicon-based anodes. Furthermore, existing binder systems are insufficiently adaptable to the significant volume changes in silicon materials, making it difficult to firmly bind the active material during long-term cycling and maintain the mechanical integrity of the electrode, further exacerbating the deterioration of cycle performance. More importantly, the silicon-electrolyte interface lacks efficient ion transport channels and has low interfacial ion conductivity, which can easily lead to severe polarization, especially under fast charging conditions, resulting in a decrease in charge and discharge efficiency. If a solid electrolyte is introduced, it often suffers from poor contact with the silicon-based electrode, resulting in high interfacial ion transport resistance and difficulty in effective integration into traditional liquid battery systems, further limiting its practical application.

[0035] The aforementioned multiple bottlenecks are intertwined, making it impossible for existing silicon-based anodes to simultaneously meet the practical application requirements of high energy density, high fast charging performance, and long cycle stability, thus becoming a key bottleneck restricting the upgrading of lithium-ion batteries to high-end applications.

[0036] Based on this, this application provides a negative electrode sheet, an all-solid-state battery, and a power device. The negative electrode sheet adopts a double-layer silicon-based negative electrode material, and introduces a high-entropy sulfide electrolyte with high ionic conductivity, excellent interfacial compatibility, and structural stability into the second active material layer (surface layer). This can effectively solve the problems of high ion transport impedance, structural failure due to volume expansion, and poor contact with the electrolyte interface in traditional silicon-based negative electrodes during fast charging. Thus, the battery can achieve excellent performance of high-efficiency fast charging, high initial efficiency, and long cycle stability under low stacking pressure (≤5MPa).

[0037] Please see Figure 1The negative electrode sheet provided by this invention includes a negative current collector 1, a first active material layer 2, and a second active material layer 3. The negative current collector 1 serves as the electrode sheet substrate and can be any conductive material capable of supporting and carrying the negative active material layer, such as copper foil, carbon-coated copper foil, copper foam, or a composite current collector composed of a metal layer (copper) and a polymer substrate. The first active material layer 2 and the second active material layer 3 together constitute the negative active material layer. The first active material layer 2 is disposed on at least one side of the negative current collector 1, and the second active material layer 3 is disposed on the side of the first active material layer 2 opposite to the negative current collector 1. That is, the negative current collector 1 has a first surface and a second surface disposed opposite to each other along its thickness direction, and the first active material layer 2 can be disposed on either the first surface or the second surface (e.g., ...). Figure 1 As shown in the figure, it can also be provided on both the first and second surfaces (not shown in the figure); the second active material layer 3 is provided on the first active material layer 2. In other words, along the thickness direction of the negative electrode sheet, the first active material layer 2 is provided close to the negative electrode current collector 1, and the second active material layer 3 is provided away from the negative electrode current collector 1.

[0038] The first active material layer 2 comprises a silicon-based material, a first conductive agent, and a binder. The second active material layer 3 comprises a silicon-based material, a second conductive agent, a binder, and a high-entropy sulfide solid electrolyte. The soft high-entropy sulfide solid electrolyte exhibits good interfacial wettability with the silicon-based material, effectively filling the gaps between active particles to form a continuous solid-solid ion conduction network, thereby significantly reducing interfacial impedance. Simultaneously, the high-entropy sulfide solid electrolyte, through multi-metal site modulation of its electronic structure, can significantly improve its reduction stability at 0.01V vs. Li. + The Li / Li potential maintains interface stability, preventing continuous interface degradation and thus improving the battery's initial coulombic efficiency (up to 88% or more), laying the foundation for long cycle life. Furthermore, its multi-metal composition can undergo slight surface remodeling or form a flexible interface layer in the early stages of electrochemical cycling, adaptively encapsulating silicon particles to achieve dynamic wetting and further reducing initial interfacial contact resistance.

[0039] In some alternative embodiments, the high-entropy sulfide solid electrolyte has the general chemical formula Li. 4±x-y A y (M1 a M2 b M3 c S4 δ X δIn the formula, 0≤x≤1.5, 0≤y≤1.5; 0.4≤a≤0.8, 0.1≤b≤0.4, 0.1≤c≤0.3, a+b+c=1, 0≤δ≤1; A is selected from one or two of Na and K; M1 is selected from one or more of Ge, Sn, Si, P, As, and B; M2 is selected from one or more of Sb, Nb, Ta, V, Mo, W, Ti, Zr, Hf, and Re; M3 is selected from one or more of Al, Ga, In, Bi, Pb, Mg, Ca, Zn, Cd, Y, Sc, La, Ba, Sr, Ce, and Sm; X is selected from one or more of O, Se, and Te.

[0040] Those skilled in the art should understand that: 4±xy in the above chemical formula represents the stoichiometric ratio of Li, where "4" represents the theoretical reference molar number of Li, "±x" represents the "non-stoichiometric floating term" of Li, x is the adjustment amount, such as intentionally adding excess Li during preparation to compensate for subsequent interface loss, or slight loss of Li during sintering, etc., x can be any value from 0 to 1.5, for example, it can be 0, 0.5, 1.0 or 1.5, etc.; y is the substitution amount of A for Li, where A can be Na, or K, or a combination of Na and K, and the value of y can be 0, 0.5, 1.0 or 1.5, etc. M1, M2, and M3 represent cations. M1 can be any one of Ge, Sn, Si, P, As, and B, such as Ge, Sn, or Si, etc. M1 can also be any combination of two or more of Ge, Sn, Si, P, As, and B, such as Ge and Sn, or P, As, and B, etc. 'a' represents the stoichiometric ratio of M1, which can be 0.4, 0.5, 0.6, 0.7, or 0.8, etc. M2 can be any one of Sb, Nb, Ta, V, Mo, W, Ti, Zr, Hf, and Re, such as Sb, Nb, or Mo, etc. M2 can also be any combination of two or more of the elements listed above, such as Sb and Ta, or W, Ti, and Zr, etc. 'b' represents the stoichiometric ratio of M2, which can be 0.1, 0.2, 0.3, or 0.4, etc. M3 can be any one of Al, Ga, In, Bi, Pb, Mg, Ca, Zn, Cd, Y, Sc, La, Ba, Sr, Ce, and Sm, for example, Al, Ga, Bi, or Mg, etc. M3 can also be any combination of two or more of the elements listed above, such as Al and Ga, or a combination of Ba, Sr, and Sm, etc. c represents the stoichiometric ratio of M3, which can be 0.1, 0.2, or 0.3, etc. It should be noted that the values ​​of a, b, and c must ensure that a + b + c = 1. X represents the position of the substituted S, and δ represents the amount of substitution of X. X can be any one of O, Se, and Te, or any combination of two or three, for example, X can be O, Se, a combination of Te and Se, or a combination of O, Se, and Te, etc. The value of δ can be 0, 0.5, or 1, etc.

[0041] The high-entropy sulfide solid electrolyte of this invention, compared with conventional sulfide solid electrolytes (such as Li3PS4, Li...), 10 GeP2S 12(etc.), which not only expands the lithium-ion transport channels and reduces the lithium-ion migration energy barrier through the lattice distortion caused by the disordered solid solution of polymetallic cations, significantly improving the room temperature ionic conductivity, can efficiently adapt to the rapid lithium-ion transport requirements in silicon-carbon anodes, alleviate local polarization and improve battery rate performance, but also enhances structural stability and mechanical strength through high-entropy thermodynamic stabilization effect and element doping optimization, adapting to the volume expansion and contraction during the charging and discharging process of silicon-carbon anodes and avoiding electrolyte particle breakage and pulverization; at the same time, by multi-element synergistic regulation of surface electronic structure, it reduces interfacial side reactions with silicon substrate, broadens the electrochemical stability window, and improves water and oxygen stability to extend battery cycle life.

[0042] The aforementioned high-entropy sulfide solid electrolyte can be prepared using the following method: First, according to the chemical formula Li 4±x-y A y (M1 a M2 b M3 c S4 δ X δ Li source, A source, M1 source, M2 source, M3 source, S source, and X source are mixed evenly according to a stoichiometric ratio, and then added to a ball mill jar for ball milling to obtain precursor powder. The ball-to-material mass ratio in the ball mill jar is 1:1 to 100:1, the ball milling time is 1 to 48 hours, and the ball milling speed is 50 to 1500 rpm. In some optional embodiments, the ball-to-material mass ratio can be 1:1, 50:1, 80:1, or 100:1, etc.; the ball milling time can be 1 hour, 12 hours, 24 hours, 36 hours, or 48 hours, etc.; and the ball milling speed can be 50 rpm, 500 rpm, 1000 rpm, or 1500 rpm, etc.

[0043] The precursor powder obtained by ball milling is then sintered at 150~500℃ for 1~12h, followed by cooling at a rate of 1~10℃ / s to obtain a high-entropy sulfide solid electrolyte. In some optional embodiments, the sintering temperature can be 150℃, 300℃, 400℃, or 500℃, etc.; the sintering time can be 1h, 6h, 10h, or 12h, etc.

[0044] The preparation method of high-entropy sulfide solid electrolytes is not limited to this; other conventional methods for preparing sulfide solid electrolytes can also be used.

[0045] The applicant's research found that the D50 particle size of the high-entropy sulfide solid electrolyte has a significant impact on the electrode pore structure: when the D50 particle size is too large, the electrode pore structure tends to be coarse, leading to a longer ion transport path and a smaller interfacial contact area between the electrode and the electrolyte. This ultimately results in a significant decrease in battery capacity retention and a significant increase in DCR (DC resistance) under fast charging conditions. Conversely, when the D50 particle size is too small, although it can improve particle packing density and interfacial contact between the electrode and the electrolyte, the significantly increased particle specific surface area and the increased number of exposed active sites will exacerbate side reactions with the silicon anode surface (such as interfacial decomposition and excessive SEI film growth). At the same time, excessively small particle size can also easily lead to slurry agglomeration and uneven dispersion, destroying the uniformity of the conductive network inside the electrode, ultimately weakening the battery's cycle stability and rate performance. In some optional embodiments, the D50 particle size of the high-entropy sulfide solid electrolyte is 500 nm to 5 μm, specifically 500 nm, 2 μm, 4 μm, or 5 μm, etc. Furthermore, the D50 particle size of the high-entropy sulfide solid electrolyte is 1μm~3μm, specifically selectable as 1μm, 2μm or 3μm, etc.

[0046] Furthermore, the first active material layer 2 also includes a high-entropy sulfide solid electrolyte. In the first active material layer 2, the mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, first conductive agent and binder is (85~98):(0~10):(0.1~3):(1~5). For example, it can be 85:10:2:3, or 98:0:1:1, or 90:5:3:2, etc. It should be noted that when the mass percentage of high-entropy sulfide solid electrolyte in the first active material layer 2 is 0, it means that the first active material layer 2 does not contain high-entropy sulfide solid electrolyte.

[0047] In the second active material layer 3, the mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, second conductive agent, and binder is (45~84):(10~30):(5~20):(1~5). For example, it can be 45:30:20:5, 84:10:5:1, or 65:20:12:3, etc. The first active material layer 2 of the negative electrode sheet of this invention maintains a high silicon-based material content. The second active material layer 3, by reducing the silicon-based material content and increasing the content of high-entropy sulfide solid electrolyte and conductive agent, can provide sufficient and efficient ion transport channels and a continuous electron transport network while maintaining a high active material load.

[0048] In some optional embodiments, the first conductive agent in the first active material layer 2 can be a type of conductive agent conventional in the art, including but not limited to one or more of carbon black, graphite, carbon fiber, and carbon nanotubes. For example, the first conductive agent is carbon black, or graphite, or a combination of carbon fiber and graphite, etc. The first active material layer 2 is located close to the negative electrode current collector 1. The current collector itself has high mechanical strength and rigidity, and can directly provide stable support for the first active material layer 2, dispersing and bearing most of the expansion stress generated during the charging and discharging of the silicon-based material. The first active material layer 2 uses conventional conductive agents with small particle size and excellent dispersibility, which can uniformly fill between high-content silicon-based material particles to form a dense and uniform three-dimensional conductive network, effectively solving the problem of poor electrode conductivity under high silicon content; at the same time, its volume ratio is small, not occupying too much space, ensuring the loading requirements of high silicon content while taking into account energy density.

[0049] The second conductive agent in the second active material layer 3 is a sheet-like conductive agent, including but not limited to one or more of graphene, graphite, and MXene. That is, the second conductive agent can be any one of the above materials, or any combination of two or more. For example, the second conductive agent can be graphene alone, or graphite alone, or MXene alone, or a combination of graphene and MXene, a combination of graphite and graphene, or a combination of graphene, graphite, and MXene. Further, the second conductive agent is preferably a combination of graphite and graphene, or a combination of graphite and MXene. The second active material layer 3 is far from the negative electrode current collector 1 and lacks the rigid support of the current collector. It is the part of the electrode structure most susceptible to expansion stress and most prone to cracking and peeling. The second active material layer 3 uses sheet-like conductive agents such as graphene, graphite, and MXene. The layered flexible structure of the sheet-like conductive agent can act as a flexible buffer layer, effectively absorbing and mitigating the expansion stress generated by the silicon-based material during charging and discharging, preventing cracking and peeling of the electrode surface, and ensuring the integrity of the electrode structure. At the same time, its sheet-like structure can form a continuous conductive path, making up for the problem of insufficient conductive sites under low silicon content, and taking into account conductivity. Moreover, under low silicon content, the volume ratio of the sheet-like conductive agent will not affect the overall active material loading, and can achieve the dual functions of conductivity and buffering at the same time.

[0050] The silicon-based materials and binders in the first active material layer 2 and the second active material layer 3 can be materials conventional in the art. In some embodiments, the silicon-based materials include elemental silicon, silicon oxides (SiO2), etc. x(0 < x ≤ 2)), at least one of a silicon-carbon composite material and a silicon alloy. That is, the silicon-based material can be selected from any of the materials listed above. For example, elemental silicon, or a silicon oxide compound, or a silicon-carbon composite material, or a silicon alloy. The silicon-based material can also be a combination of any two or more of the materials listed above. For example, a composition of elemental silicon and a silicon oxide compound, or a composition of elemental silicon and a silicon alloy, etc. The silicon-based materials in the first and second active material layers can be the same or different, and there is no limitation here.

[0051] In some embodiments, the binder includes one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-chlorotrifluoroethylene copolymer. That is, the binder can be selected from any of the materials listed above, or a combination of any two or more of the materials listed above. Exemplarily, the binder is polyvinylidene fluoride (PVDF), or polymethyl methacrylate (PMMA), or polyvinylpyrrolidone (PVP), or a composition of polyacrylic acid (PAA) and styrene-butadiene rubber (SBR), etc. The binders in the first and second active material layers can be the same or different, and there is no limitation here.

[0052] In some embodiments, the D50 of the silicon-based material in the first active material layer 2 is 30 nm to 10 μm. Further, it can be 1 μm to 7 μm, and specifically can be 1 μm, 3 μm, 5 μm, or 7 μm, etc.; the D50 of the silicon-based material in the second active material layer is 10 nm to 12 μm. Further, it can be 1 μm to 10 μm, and specifically can be 2 μm, 4 μm, 6 μm, 8 μm, or 10 μm, etc.

[0053] In some embodiments, the tap density of the first active material layer 2 is 1 g / cm 3 ~1.3 g / cm 3 Exemplarily, it can be 1 g / cm 3 、1.2 g / cm 3 、1.2 g / cm 3Or 1.3g / cm 3 The compaction density of the first active material layer 2 is controlled within this range to ensure the compactness of the electrode structure while retaining appropriate porosity, thereby effectively accommodating the volume expansion of the silicon-based material and maintaining unobstructed ion transport channels. If the compaction density of the first active material layer 2 is too high, although it can improve the contact performance between particles and the electron conduction efficiency, excessive densification will compress the pore space, which will not only inhibit the diffusion kinetics of lithium ions, but also aggravate the stress concentration caused by silicon expansion, leading to electrode interface cracking, a significant increase in impedance, and ultimately a decrease in battery cycle stability and rate performance. Conversely, if the compaction density of the first active material layer 2 is too low, the excessive porosity will cause loose particle contact, resulting in discontinuity in the electron and ion transport network, leading to increased interface impedance, and making it difficult to effectively buffer the volume change of silicon, ultimately causing the active material to fall off and accelerating the battery capacity decay rate. The compaction density of the first active material layer can be controlled by adjusting the particle size of the silicon-based material in the first active material layer, the particle size of the sulfide solid electrolyte, and the composition of the silicon-based material.

[0054] The compaction density of the second active material layer 3 is lower than that of the first active material layer 2, resulting in an active material layer with high porosity, forming a gradient pore structure with the first active material layer 2. This gradient pore design works synergistically with the high-entropy sulfide electrolyte with high ionic conductivity, enabling the battery to achieve high-efficiency fast charging of over 4C even under low stacking pressure conditions of ≤5MPa, effectively overcoming the technical bottleneck of traditional silicon-based anode fast charging performance being limited by stacking pressure.

[0055] In some embodiments, the compaction density of the second active material layer 3 is 0.7 g / cm³. 3 ~1g / cm 3 Specifically, 0.7g / cm³ can be selected. 3 0.8g / cm 3 0.9g / cm 3 Or 1g / cm 3The compaction density of the second active material layer 3, within this range, ensures sufficient porosity to buffer the volume expansion of silicon while allowing the high-entropy sulfide electrolyte to form a tight and continuous interfacial contact with the adjacent solid electrolyte layer, constructing an efficient lithium-ion transport channel, thus exhibiting low DC resistance (DCR) and excellent fast-charging performance. If the compaction density of the second active material layer 3 is too low, the active material layer structure will be too loose, resulting in poor contact between particles and between the electrode and the electrolyte layer, thereby increasing the interfacial impedance and impairing fast-charging performance. If the compaction density of the second active material layer 3 is too high, it will reduce the number of pores in the active material layer, weakening its buffering capacity against silicon volume expansion, leading to a decrease in battery cycle stability. The compaction density of the second active material layer can be controlled by adjusting the particle size of the silicon-based material, the particle size of the sulfide solid electrolyte, and the composition of the silicon-based material.

[0056] The compaction density of the first active material layer 2 and the second active material layer 3 can be characterized by the following method: A vertical cross-section of the electrode is prepared, and the morphology of the bilayer interface and the thickness of each layer are observed using a scanning electron microscope (SEM); non-destructive three-dimensional reconstruction is performed using X-ray microtomography (X-ray CT) to obtain the pore structure of each layer. The local volumetric porosity of the surface layer (second active material layer) and the bottom layer (first active material layer) are calculated respectively, and the gradient compaction density is obtained by converting it according to the true density of the active material. Wherein, volumetric porosity = number of pore volumetric elements / total number of volumetric elements, and local compaction density = (1 - porosity) × true density of the material.

[0057] The present invention also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps: S1. Prepare the first negative electrode slurry.

[0058] First, silicon-based materials, high-entropy sulfide solid electrolyte, and first conductive agent are mixed evenly according to a set ratio. Then, a set ratio of binder is added and mixed evenly. Finally, a solvent is added, and after stirring, mixing, sieving, and defoaming, the first negative electrode slurry is obtained.

[0059] The selection of silicon-based materials, high-entropy sulfide solid electrolytes, the first conductive agent, and the binder in this step is described above and will not be repeated here. Conventional organic solvents in the art, such as xylene, can be used. The amount of organic solvent added is adjusted according to actual production needs and is not limited here.

[0060] S2. Prepare the second negative electrode slurry.

[0061] First, silicon-based materials, high-entropy sulfide solid electrolyte, and second conductive agent are mixed evenly according to a preset ratio. Then, a set ratio of binder is added and mixed evenly. Finally, a solvent is added, and after stirring, mixing, sieving, and defoaming, the second negative electrode slurry is obtained.

[0062] The selection of silicon-based materials, high-entropy sulfide solid electrolytes, the second conductive agent, and the binder in this step is described above and will not be repeated here. The solvent can be a conventional organic solvent in the art, such as xylene. The amount of organic solvent added can be adjusted according to actual production needs and is not limited here. Steps S1 and S2 are not sequential; S1 can be performed first, S2 can be performed first, or S1 and S2 can be performed simultaneously.

[0063] S3. Coat the first negative electrode slurry and the second negative electrode slurry onto the negative electrode current collector.

[0064] The coating method for the negative electrode slurry in this step includes any one of the following: slot extrusion coating, comma roller transfer coating, sliding multilayer coating, curtain multilayer coating, and die extrusion multilayer coating. For example, the first and second negative electrode slurries can be simultaneously coated onto the negative electrode current collector using die extrusion multilayer coating, or the first and second negative electrode slurries can be simultaneously coated onto the negative electrode current collector using sliding multilayer coating, etc. The coating amounts of the first and second negative electrode slurries are set according to actual needs and are not limited here. After coating, a double-layer negative electrode sheet is obtained through processes such as baking and rolling.

[0065] The present invention also provides an all-solid-state battery, which includes a positive electrode, a solid electrolyte layer and the negative electrode described above. The solid electrolyte layer is disposed between the positive electrode and the negative electrode to provide a channel for ion transport between the positive and negative electrodes, while blocking electron transport, thereby avoiding short circuits.

[0066] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive current collector is, for example, aluminum foil or carbon-coated aluminum foil, and has two surfaces disposed opposite to each other along its thickness direction. The positive active material layer can be disposed on one surface of the positive current collector or simultaneously on both surfaces. The positive active material layer includes a positive active material, a solid electrolyte, a conductive agent, and a binder. The positive active material includes, but is not limited to, one or more of lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium cobalt oxide (LCO), and lithium nickel cobalt aluminum oxide (NCA). That is, the positive active material can be a single material, such as lithium cobalt oxide, or lithium nickel cobalt manganese oxide, or lithium nickel manganese oxide, etc.; or it can be a combination of multiple materials, such as a combination of lithium cobalt oxide and lithium nickel oxide, a combination of lithium nickel cobalt aluminum oxide, lithium-rich oxide, and lithium nickel cobalt manganese oxide, etc. The solid electrolyte is the high-entropy sulfide solid electrolyte provided in this application, but conventional solid electrolytes such as oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes can also be used. The conductive agent includes one or more of graphite, graphene, carbon black, carbon fiber, and carbon nanotubes, such as graphite, or a combination of carbon black and carbon fiber, etc. The adhesives include one or more of the following: hydrogenated nitrile rubber, polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer.

[0067] The preparation method of the positive electrode sheet is as follows: the positive active material, solid electrolyte, conductive agent and binder are thoroughly mixed in a solvent such as xylene according to a set ratio, and then coated on the positive current collector. After drying and cold pressing, the positive electrode sheet is obtained.

[0068] The solid electrolyte layer includes a solid electrolyte, which is the aforementioned high-entropy sulfide solid electrolyte. In other optional embodiments, the solid electrolyte may also be an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, etc. The solid electrolyte layer is obtained by cold pressing the solid electrolyte.

[0069] All-solid-state battery assembly: The positive and negative electrode plates are placed on both sides of the solid electrolyte layer, pressed together, and sealed to obtain an all-solid-state battery. The assembly process is completed in a glove box under an inert atmosphere.

[0070] It should be noted that the structures not described in detail in the above batteries can be set up with reference to conventional techniques in this field, and will not be elaborated here.

[0071] The present invention also provides an electrical device comprising the above-mentioned all-solid-state battery, wherein the all-solid-state battery may be used in the form of a single cell, a battery module, or a battery pack to power the electrical device.

[0072] In some embodiments, the electrical device includes mobile phones, tablets, laptops, electric toys, electric vehicles, new energy vehicles, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc., but are not limited to these.

[0073] The technical solution of the present invention will be described in detail below through several specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the embodiments are all commercially available.

[0074] Example 1 This embodiment provides a negative electrode sheet, which includes a negative electrode current collector, a first active material layer disposed on the negative electrode current collector, and a second active material layer disposed on the first active material layer. The negative electrode current collector is copper foil, and the first active material layer includes 90 wt% silicon-carbon negative electrode (80% 6μm SiC particles + 20% 1μm SiC particles) and 5% Li. 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2S4, 2% carbon nanotubes and 3% SBR binder; the second active material layer includes 62wt% silicon-carbon anode (100% 6μm SiC particles), 20% Li 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 S4, 15% (98.5% graphite + 1.5% graphene), and 3% SBR binder. The specific preparation process is as follows: (1) Preparation of high-entropy sulfide solid electrolyte: Under an argon atmosphere, 1.73 mol Li₂S, 0.06 mol SnS₂, 0.21 mol SiS₂, 0.33 mol P₂S₅, 0.1 mol Sb₂S₅, and 0.1 mol Al₂S₃ were placed in a ball mill jar, and grinding balls were added at a ball-to-material mass ratio of 30:1. The mixture was ball-milled at 100 rpm for 10 minutes, and then ball-milled at 600 rpm for 16 hours to obtain a uniformly mixed precursor material. The precursor material was placed in a crucible and sintered at 200 °C for 20 hours. After cooling at a rate of 5 °C / s, Li₂S₅ was obtained. 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 S4 electrolyte material, and Li with a D50 of 1 μm was obtained by sieving. 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 S4 electrolyte material.

[0075] (2) Preparation of the first negative electrode slurry: 90 wt% silicon-carbon (80% 6μm SiC particles + 20% 1μm SiC particles) negative electrode, 5% Li 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 After S4 and 2% carbon nanotubes are mixed evenly, 3% SBR binder and xylene solvent are added. After stirring, mixing, sieving and defoaming, the first negative electrode slurry is obtained, wherein the solid content of the first negative electrode slurry is 30%.

[0076] (3) Preparation of the second negative electrode slurry: 62wt% silicon-carbon (100% 6μm SiC particles) negative electrode, 20% Li 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 S4 and 15% of conductive agent (98.5% graphite + 1.5% graphene) are mixed evenly, then 3% of SBR binder is added, along with xylene solvent. After stirring, mixing, sieving, and defoaming, the second negative electrode slurry is obtained, wherein the solid content of the second negative electrode slurry is 30%.

[0077] (4) Coating: The first and second negative electrode slurries are coated onto copper foil using a multi-layer coating method with a die extrusion. After baking and rolling, a double-layer silicon-based negative electrode sheet is obtained. Specifically, the areal capacity of the first active material layer is controlled to be 1.9 mAh / cm². 2 The areal capacity of the second active material layer is 2.5 mAh / cm³. 2 This results in a total electrode surface capacity of 4.4 mAh / cm². 2 .

[0078] This embodiment also provides an all-solid-state battery including the above-mentioned negative electrode sheet, the specific composition of which is as follows: Preparation of positive electrode: LiNi 0.8 Co 0.1 Mn 0.1 O2, the aforementioned high-entropy sulfide solid electrolyte Li 3.46 (Sn 0.1 Si 0.35 P 0.55 ) 0.6 Sb 0.2 Al 0.2 S4, conductive agent carbon fiber, and binder hydrogenated nitrile rubber are thoroughly mixed in a xylene solvent system at a mass ratio of 70:25:2:3. The mixture is then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. The areal capacity of the positive electrode sheet is 4 mAh / cm². 2 And cut it into round pieces with a diameter of 10mm.

[0079] Negative electrode preparation: The negative electrode obtained in step (4) is cut into a circular piece with a diameter of 10 mm.

[0080] Solid electrolyte layer: 50 mg of the high-entropy sulfide solid electrolyte material prepared above was cold-pressed at 360 MPa to prepare an electrolyte layer with a thickness of 300 μm and a diameter of 10 mm.

[0081] Battery assembly: The positive and negative electrode sheets were placed at both ends of the solid electrolyte layer, pressed at 500 MPa, and then sealed to obtain an all-solid-state battery. The assembly process of the all-solid-state battery was completed in a glove box with an inert atmosphere.

[0082] Example 2 The difference between this embodiment and Embodiment 1 is that the high-entropy sulfide solid electrolyte is Li. 3.9 Si 0.6 (Sb 0.5 Mo 0.2 W 0.3 ) 0.2 Al 0.2 S4; The electrolyte Li was prepared by using 1.95 mol Li₂S, 0.6 mol SiS₂, 0.05 mol Sb₂S₅, 0.04 mol MoS₃, 0.06 mol WS₃, and 0.1 mol Al₂S₃. 3.9 Si 0.6 (Sb 0.5 Mo 0.2 W 0.3 ) 0.2 Al 0.2 S4.

[0083] Example 3 The difference between this embodiment and Embodiment 1 is that the high-entropy sulfide solid electrolyte is Li. 4.04 Si 0.6 Sb 0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4; The electrolyte Li was prepared by using 2.02 mol Li₂S, 0.6 mol SiS₂, 0.1 mol Sb₂S₅, 0.03 mol Al₂S₃, 0.05 mol In₂S₃, and 0.04 mol SrS. 4.04 Si 0.6 Sb 0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4.

[0084] Example 4 The difference between this embodiment and Embodiment 1 is that the high-entropy sulfide solid electrolyte is Li. 3.8 Na 0.1 K 0.1 Si 0.6 Sb 0.2 Al0.2 S4; The electrolyte Li was prepared by using 1.9 mol Li₂S, 0.05 mol Na₂S, 0.05 mol K₂S, 0.6 mol SiS₂, 0.1 mol Sb₂S₅, and 0.1 mol Al₂S₃. 3.8 Na 0.1 K 0.1 Si 0.6 Sb 0.2 Al 0.2 S4.

[0085] Example 5 The difference between this embodiment and Embodiment 1 is that the high-entropy sulfide solid electrolyte is Li4Si. 0.6 Sb 0.2 Al 0.2 S 3.7 O 0.2 Te 0.1 ; The electrolyte Li4Si was prepared by using 1.7 mol Li2S, 0.6 mol SiS2, 0.1 mol Sb2S5, 0.1 mol Al2S3, 0.2 mol Li2O, and 0.1 mol Li2Te. 0.6 Sb 0.2 Al 0.2 S 3.7 O 0.2 Te 0.1 .

[0086] Example 6 The difference between this embodiment and Embodiment 3 is that the D50 particle size of the high-entropy sulfide solid electrolyte is 500 nm.

[0087] Example 7 The difference between this embodiment and Embodiment 3 is that the D50 particle size of the high-entropy sulfide solid electrolyte is 2 μm.

[0088] Example 8 The difference between this embodiment and Embodiment 3 is that the D50 particle size of the high-entropy sulfide solid electrolyte is 3 μm.

[0089] Example 9 The difference between this embodiment and Embodiment 3 is that the D50 particle size of the high-entropy sulfide solid electrolyte is 5 μm.

[0090] Example 10 The difference between this embodiment and Embodiment 3 is that the composition ratio of the first active material layer is 85wt% silicon-carbon anode and 10% Li. 4.04 Si 0.6 Sb0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4, 2% carbon nanotubes and 3% SBR.

[0091] Example 11 The difference between this embodiment and Embodiment 3 is that the composition of the first active material layer is 95wt% silicon-carbon anode, 2% carbon nanotubes and 3% SBR.

[0092] Example 12 The difference between this embodiment and Embodiment 3 is that the silicon-carbon anode in the first active material layer consists of 95% 6μm SiC particles + 5% 1μm SiC particles.

[0093] Example 13 The difference between this embodiment and Embodiment 3 is that the silicon-carbon anode in the first active material layer consists of 70% 10μm SiC particles + 30% 2μm SiC particles.

[0094] Example 14 The difference between this embodiment and Embodiment 3 is that the composition ratio of the second active material layer is 47wt% silicon-carbon anode and 30% Li. 4.04 Si 0.6 Sb 0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4, 20% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0095] Example 15 The difference between this embodiment and Embodiment 3 is that the composition ratio of the second active material layer is 52wt% silicon-carbon anode and 30% Li. 4.04 Si 0.6 Sb 0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4, 15% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0096] Example 16 The difference between this embodiment and Embodiment 3 is that the composition ratio of the second active material layer is 72wt% silicon-carbon anode and 10% Li. 4.04 Si 0.6 Sb 0.2 (In0.5 Al 0.3 Sr 0.2 ) 0.2 S4, 15% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0097] Example 17 The difference between this embodiment and Embodiment 3 is that the composition ratio of the second active material layer is 82wt% silicon-carbon anode and 10% Li. 4.04 Si 0.6 Sb 0.2 (In 0.5 Al 0.3 Sr 0.2 ) 0.2 S4, 5% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0098] Example 18 The difference between this embodiment and Embodiment 3 is that the silicon-carbon negative electrode in the second active material layer is 100% 12μm SiC particles.

[0099] Example 19 The difference between this embodiment and Embodiment 3 is that in the second active material layer, the silicon-carbon negative electrode is composed of 95% 6μm SiC particles and 5% 1μm SiC particles.

[0100] Example 20 The difference between this embodiment and Embodiment 3 is that the D50 of the sulfide solid electrolyte is 6 μm.

[0101] Example 21 The difference between this embodiment and Embodiment 3 is that in the first active material layer, the silicon-carbon negative electrode is composed of 99% 6μm SiC particles and 1% 1μm SiC particles.

[0102] Example 22 The difference between this embodiment and Embodiment 3 is that in the second active material layer, the silicon-carbon negative electrode is composed of 80% 6μm SiC particles and 20% 1μm SiC particles.

[0103] Comparative Example 1 The difference between this comparative example and Example 3 is that the sulfide electrolyte is Li4SnS4; The electrolyte Li4SnS4 was prepared by using 2 mol Li2S and 1 mol SnS2.

[0104] Comparative Example 2 The difference between this comparative example and Example 3 is that the negative electrode sheet only contains the first active material layer.

[0105] Comparative Example 3 The difference between this comparative example and Example 3 is that the composition of the second active material layer is 82 wt% silicon-carbon anode, 15% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0106] Comparative Example 4 The difference between this comparative example and Example 11 is that the composition of the second active material layer is 82 wt% silicon-carbon anode, 15% conductive agent (98.5% graphite + 1.5% graphene) and 3% SBR.

[0107] Table 1: Chemical formulas and particle sizes of sulfide solid electrolytes in the negative electrode sheets of Examples 1-22 and Comparative Examples 1-4

[0108] Table 2: Composition of the negative electrode sheets in Examples 1-22 and Comparative Examples 1-4

[0109] Table 3: Battery performance of Examples 1-22 and Comparative Examples 1-4

[0110] Test methods (1) D50 particle size test: The D50 particle size of the sulfide solid electrolyte was tested using a HELOS-RODOS dry laser particle size analyzer. The test results are recorded in Table 1.

[0111] (2) Room temperature cycling performance test: At 25°C, the all-solid-state batteries assembled in each embodiment and comparative example were subjected to a low pressure of 3 MPa, activated for 2 cycles at a rate of 0.05C within an operating voltage range of 2.5~4.3V, and then charged and discharged at a rate of 1C / 1C (1C rated current density is 4 mA / cm²). 2 Record the discharge capacity Q0 of the battery in the first 1C cycle after activation. Cycle the battery for 500 full charge and discharge cycles and record the discharge capacity Q1 after 500 cycles. Calculate the capacity retention rate after 500 cycles at 1C / 1C at room temperature using the following formula: 500-cycle capacity retention rate = (Q1 / Q0) × 100%.

[0112] (3) DCR test at 50% SOC: The chamber temperature was kept constant at 25℃. After resting for 10 minutes, the battery was charged at a constant current rate of 0.33 C to 4.3 V, then charged at a constant voltage rate of 0.05 C. After resting for 10 minutes, it was discharged at 0.33 C to 2.5 V, obtaining the battery's 100% SOC capacity C1. Then, it was charged again at a constant current rate of 0.33 C1 to 4.3 V, then charged at a constant voltage rate of 0.05 C1. After resting for 10 minutes, it was discharged at a rate of 0.33 C1 to adjust the capacity to 50% SOC. After resting for 1 hour, the initial battery voltage V1 was recorded. The battery was then discharged at a current of 4 C1 I0 for 30 seconds, and the battery voltage V2 after discharge was recorded. The DCR at 50% SOC was calculated using the following formula: DCR(Ω)=(V1-V2) / I0.

[0113] (4) Rate performance (fast charging capacity retention rate) At 25°C, the all-solid-state batteries assembled in each embodiment and comparative example were subjected to a low pressure of 3 MPa, operating at a voltage of 2.5–4.3 V, and at a current density of 0.05C (1C rated current density is 4 mA / cm²). 2 Activate the battery at the specified rate for 2 cycles. Charge the solid-state battery in constant current / constant voltage mode at a constant rate of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant rate of 0.33C; repeat the above steps for three charge-discharge cycles, and record the discharge capacity C in the third cycle. 0.33 Charge the solid-state battery at a constant current and constant voltage (DCV) mode with a constant current rate of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage with a constant current rate of 0.5C; repeat the above steps for three charge-discharge cycles. Charge the solid-state battery at a constant current and constant voltage (DCV) mode with a constant current rate of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage with a constant current rate of 1C; repeat the above steps for three charge-discharge cycles. Charge the solid-state battery at a constant current and constant voltage (DCV) mode with a constant current rate of 0.33C; after resting for 5 minutes, discharge the battery to the lower limit of the operating cutoff voltage with a constant current rate of 4C; repeat the above steps for three charge-discharge cycles, and record the discharge capacity C4 in the third cycle.

[0114] The capacity retention rate of high-rate 4C fast charging was calculated using the following formula, and the test results are recorded in Table 2: Fast charging capacity retention rate (%) = (C4 / C) 0.33 )×100%.

[0115] Please refer to Tables 1 to 3. The following conclusions can be drawn from the test data in the tables: Examples 1-5 and Comparative Example 1 were compared under the same conditions, with only the type of sulfide solid electrolyte being adjusted. The test results showed that the electrochemical performance of Examples 1-5 was significantly better than that of Comparative Example 1. The fundamental reason for this is that the high-entropy sulfide solid electrolyte used in Examples 1-5 possesses both low Young's modulus and high ionic conductivity. This material not only effectively reduces interfacial impedance and improves lithium-ion transport efficiency, but also, due to its excellent flexibility and structural stability, better adapts to the huge volume expansion during the charging and discharging process of the silicon-based anode under low stacking pressure, thus maintaining the integrity of the electrode structure and the stability of the interfacial contact. Simultaneously, combined with the gradient pore design of the first and second active material layers and the optimized conductive network, the system further optimized the electron / ion transport dynamics, ultimately achieving high capacity retention and long-cycle stability under fast charging conditions. In contrast, the conventional sulfide electrolyte used in Comparative Example 1, due to its high Young's modulus and relatively low ionic conductivity, could neither effectively buffer the volume changes of the silicon-based anode nor form a stable interfacial contact, ultimately leading to a significant deterioration in electrochemical performance.

[0116] Examples 3, 6, 7, 8, 9, and 20, with all other conditions kept constant, only the D50 of the high-entropy sulfide solid electrolyte was adjusted. The test results show that when the D50 of the high-entropy sulfide solid electrolyte gradually increases from 1 μm to 6 μm, the electrode pore structure gradually coarsens, directly leading to an extended ion transport path, a significant reduction in the solid-solid interface contact area, a substantial decrease in capacity retention under fast charging conditions, and a simultaneous deterioration in DC internal resistance (DCR). When the D50 decreases to 500 nm, although it can effectively improve particle packing density and interfacial contact, the specific surface area increases significantly, resulting in excessive exposure of active sites and exacerbating side reactions on the silicon anode surface (including interfacial decomposition and excessive SEI film growth). At the same time, it easily causes slurry agglomeration and uneven dispersion, destroying the uniformity of the conductive network, ultimately deteriorating the cycle stability and rate performance of the electrode. In Example 20, the D50 of the high-entropy sulfide solid electrolyte is too large, and the large particle size leads to severe insufficient interfacial contact and a sharp increase in ion diffusion resistance, resulting in a significant deterioration in first-efficiency performance, DCR, and capacity retention.

[0117] Examples 3, 10, and 11, under the premise of keeping other conditions consistent, adjust the composition ratio of the first active material layer. The test results show that when the first active material layer maintains a suitable ratio of active material, high-entropy sulfide solid electrolyte, and conductive agent, sufficient ion transport channels and good interfacial contact conditions can be simultaneously constructed while ensuring a high silicon-based active material loading, achieving an optimal balance between active material utilization and ion conduction efficiency, thus ensuring stable overall battery performance. If the proportion of active material in the first active material layer is reduced while the proportion of high-entropy sulfide solid electrolyte is simultaneously increased, although ion conduction efficiency is slightly enhanced, the excessive solid electrolyte dilutes the active material loading, directly leading to a decrease in battery energy density. Simultaneously, excessive electrolyte accumulation can easily cause local pore blockage, even blocking electron conduction pathways, ultimately resulting in simultaneous degradation of the battery's initial efficiency and rate performance. If the proportion of silicon-based active material in the first active material layer is increased while the proportion of high-entropy sulfide solid electrolyte is reduced (even to 0%), the first active material layer will lack ion conductors, forming "electron conductor islands," preventing effective ion penetration, drastically increasing interfacial impedance, and significantly reducing the battery's initial efficiency and fast-charging performance.

[0118] Examples 3, 12, 13, and 21, under the premise of keeping other conditions consistent, controlled the compaction density of the first active material layer by adjusting the particle size and composition of the silicon-carbon anode. The test results show that when the compaction density of the first active material layer is controlled within a suitable range, it can maintain a moderate porosity while ensuring the compactness of the electrode structure. This provides space for the volume expansion of the silicon-based active material and maintains a continuous ion transport channel, ultimately achieving stable electrochemical performance. If the compaction density is too high, although it can improve the interparticle contact strength and electron conduction efficiency, excessive compaction will significantly compress the pore space: on the one hand, it inhibits lithium-ion diffusion kinetics, and on the other hand, it exacerbates the stress concentration of the silicon-based active material expansion, ultimately leading to interface cracking, increased interface impedance, and a simultaneous decrease in cycle stability and rate performance. If the compaction density is too low, the high porosity results in loose interparticle contact, making it difficult to construct a continuous electron-ion transport network, significantly increasing the interface impedance. Simultaneously, the electrode cannot effectively buffer volume changes, easily causing active material detachment, thereby accelerating capacity decay and significantly degrading the overall electrochemical performance.

[0119] Examples 3, 14, 15, 16, 17 and Comparative Example 3, under the premise of keeping other conditions consistent, the composition ratio of the second active material layer was adjusted. The test results show that when the second active material layer maintains a suitable ratio of active material, high-entropy sulfide solid electrolyte and conductive agent, sufficient lithium-ion transport channels and continuous electronic conductivity network can be constructed simultaneously while ensuring the high active material loading, ultimately enabling the battery to exhibit better comprehensive electrochemical performance. Reducing the proportion of active materials in the second active material layer while simultaneously increasing the proportion of electrolyte and conductive agent can enhance ion / electron conduction efficiency, but the significant reduction in active material loading will directly lead to a substantial decrease in the overall battery capacity and energy density. Furthermore, the introduction of excessive sulfide electrolyte and conductive agent will exacerbate side reactions, further increasing interfacial impedance and ultimately causing a deterioration in electrochemical performance. Conversely, increasing the proportion of silicon-based active materials in the second active material layer while reducing the proportion of high-entropy sulfide solid electrolyte and / or conductive agent will trigger two types of performance degradation: first, insufficient ion conductors lead to increased interfacial impedance, hindering lithium-ion diffusion under fast charging conditions and significantly reducing capacity retention; second, the weakening of the electronic conductivity network directly causes an increase in DC internal resistance (DCR), resulting in simultaneous degradation of cycle stability and rate performance. In Comparative Example 3, the second active material layer contains no high-entropy sulfide solid electrolyte. It relies solely on 82% silicon material and 15% conductive agent to form a film, completely lacking a solid ion conduction medium. This design not only severely hinders lithium-ion transport but also results in extremely poor contact between the electrode and the solid electrolyte layer. This further verifies the irreplaceable role of the high-entropy sulfide solid electrolyte in the second active material layer in constructing a continuous ion pathway and stabilizing the electrode interface.

[0120] In Examples 3, 18, 19, and 22, while maintaining other consistent conditions, the compaction density of the second active material layer was adjusted by controlling the particle size and composition of the silicon-carbon anode in the second active material layer. The test results show that when the compaction density of the second active material layer is controlled within a suitable range, sufficient porosity is retained to effectively buffer the volume expansion of the silicon-based active material, while also promoting a tight and continuous interfacial contact between the high-entropy sulfide solid electrolyte and adjacent solid electrolyte layers. This leads to the construction of an efficient lithium-ion transport channel, ultimately achieving low DC internal resistance (DCR) and excellent 4C fast charging performance. If the compaction density of the second active material layer is too low, the internal structure is loose, resulting in poor contact between particles and between the electrode and the solid electrolyte layer, significantly increasing the interfacial impedance, decreasing lithium-ion transport efficiency, and deteriorating fast charging performance. If the compaction density is too high, the porosity is excessively compressed, severely weakening the silicon expansion buffering capacity, and continuously decreasing the electrode cycle stability. In Example 22, the compaction density of the second active material layer is too high. Although the electrode density is improved, the excessive compression directly leads to pore collapse and interface embrittlement. During cycling, stress concentration can easily cause the active material layer to debond from the solid electrolyte layer. At the same time, the lithium ion diffusion path is severely blocked, ultimately resulting in a significant deterioration of the overall electrode performance.

[0121] The test results from Examples 3, 11, Comparative Examples 2, and 4 show that in Example 3, the introduction of 5% high-entropy sulfide solid electrolyte in the first active material layer and 20% high-entropy sulfide solid electrolyte in the second active material layer not only constructs a continuous ion transport channel throughout the electrode thickness but also forms excellent interfacial contact with the solid electrolyte layer, exhibiting excellent comprehensive electrochemical performance. Although Example 11 retains the bilayer structure, the absence of high-entropy sulfide solid electrolyte in the first active material layer results in a lack of ion conduction medium on the current collector side, forming an "ion transport bottleneck." This not only hinders the uniform insertion of lithium ions, causing intensified local polarization, but also leads to an increase in DC internal resistance (DCR) and a decrease in fast-charging performance. Comparative Example 2 only has a single first active material layer, lacking both the gradient pore structure of the second active material layer and the dual advantages of interface buffering and rapid ion conduction provided by the high-content high-entropy sulfide solid electrolyte. Simultaneously, the insufficient overall solid electrolyte content results in excessive electrode structural rigidity and poor interfacial contact, ultimately leading to significant degradation in both cycle stability and rate performance. Comparative Example 4 contains no high-entropy sulfide solid electrolyte in either the first or second active material layers; the electrode relies solely on conductive agents and binders for film formation, completely lacking a solid ion conduction medium. This severely hinders lithium-ion transport, causing a sharp increase in interfacial impedance and almost complete loss of fast-charging capability. In summary, introducing an appropriate amount of high-entropy sulfide solid electrolyte, especially in the second active material layer, is crucial for constructing a continuous ion network, reducing interfacial impedance, and improving fast-charging and cycle performance. Conversely, the complete or partial absence of high-entropy sulfide solid electrolyte will lead to significant degradation of the battery's electrochemical performance.

[0122] The negative electrode provided by this invention employs a double-layer silicon-based negative electrode material and introduces a high-entropy sulfide electrolyte with high ionic conductivity, excellent interfacial compatibility, and structural stability into the second active material layer (surface layer). This effectively solves the problems of high ion transport impedance, structural failure due to volume expansion, and poor contact with the electrolyte interface that exist in traditional silicon-based negative electrodes during fast charging. Thus, the battery achieves excellent performance in low stacking pressure (≤5MPa), simultaneously possessing high-efficiency fast charging, high initial efficiency, and long-cycle stability. Therefore, this invention effectively overcomes some practical problems in the prior art, thus having high utilization value and practical significance.

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A negative electrode sheet, characterized in that, include: Negative electrode current collector; A first active material layer is disposed on at least one side of the negative electrode current collector, and the first active material layer includes a silicon-based material, a first conductive agent, and a binder; The second active material layer is disposed on the side of the first active material layer away from the negative electrode current collector. The second active material layer includes a silicon-based material, a second conductive agent, a binder, and a high-entropy sulfide solid electrolyte.

2. The negative electrode sheet according to claim 1, characterized in that, The general chemical formula of the high-entropy sulfide solid electrolyte is: Li 4±x-y A y (M1 a M2 b M3 c S4 δ X δ In the formula, 0≤x≤1.5, 0≤y≤1.5, and y≤4±x; 0.4≤a≤0.8, 0.1≤b≤0.4, 0.1≤c≤0.3, a+b+c=1, 0≤δ≤1; A is selected from one or both of Na and K; M1 is selected from one or more of Ge, Sn, Si, P, As, and B; M2 is selected from one or more of Sb, Nb, Ta, V, Mo, W, Ti, Zr, Hf, and Re; M3 is selected from one or more of Al, Ga, In, Bi, Pb, Mg, Ca, Zn, Cd, Y, Sc, La, Ba, Sr, Ce, and Sm; X is selected from one or more of O, Se, and Te.

3. The negative electrode sheet according to claim 1, characterized in that, The first active material layer also includes a high-entropy sulfide solid electrolyte, and the mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, first conductive agent and binder in the first active material layer is (85~98):(0~10):(0.1~3):(1~5); The mass ratio of silicon-based material, high-entropy sulfide solid electrolyte, second conductive agent and binder in the second active material layer is (45~84):(10~30):(5~20):(1~5).

4. The negative electrode sheet according to claim 1, characterized in that, The D50 of the high-entropy sulfide solid electrolyte is 500nm≤D50≤5μm.

5. The negative electrode sheet according to claim 4, characterized in that, The D50 of the high-entropy sulfide solid electrolyte is 1μm≤D50≤3μm.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that, The compaction density of the first active material layer is 1 g / cm³. 3 ~1.3g / cm 3 The compaction density of the second active material layer is 0.7 g / cm³. 3 ~1g / cm 3 .

7. The negative electrode sheet according to claim 1, characterized in that, The first conductive agent includes one or more of carbon black, graphite, carbon fiber, and carbon nanotubes; The second conductive agent includes one or more of graphene, graphite, and MXene.

8. The negative electrode sheet according to claim 1, characterized in that, The silicon-based material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon composite materials, and silicon alloys; The D50 of the silicon-based material in the first active material layer is 30nm~10μm; the D50 of the silicon-based material in the second active material layer is 10nm~12μm.

9. An all-solid-state battery, characterized in that, The all-solid-state battery includes a positive electrode, a solid electrolyte layer, and a negative electrode as described in any one of claims 1 to 8.

10. An electrical appliance, characterized in that, Including the all-solid-state battery as described in claim 9.

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