Negative electrode sheet, solid-state battery, electric device

Abstract

The application relates to the technical field of batteries, in particular to a negative electrode sheet, a solid-state battery and a power utilization device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer comprises silicon-carbon material particles, first silicon particles and second silicon particles; the particle size D50 of the silicon-carbon material particles is greater than the particle size D50 of the first silicon particles, and the particle size D50 of the first silicon particles is greater than the particle size D50 of the second silicon particles; and the first silicon particles have a porous structure. Through the synergistic effect of the particle size gradient compounding and the porous structure of the first silicon particles, the volume expansion of silicon during the charging and discharging process can be inhibited without sacrificing the capacity, a continuous ion transmission channel is formed, and the capacity performance, the rate performance and the cycle performance of the battery are simultaneously improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a negative electrode sheet, a solid-state battery, and an electrical device. Background Technology

[0002] In recent years, due to increasingly stringent safety requirements for lithium-ion batteries, the use of solid electrolytes to replace traditional liquid electrolytes has become an important development direction.

[0003] Silicon is considered a highly promising anode material for all-solid-state batteries due to its excellent theoretical specific capacity. However, silicon undergoes dramatic volume expansion during charge and discharge, affecting the cycle stability of the battery.

[0004] In traditional technologies, methods to suppress silicon expansion often come at the cost of capacity. For example, while introducing carbon materials to prepare silicon-carbon materials can buffer expansion, it reduces the overall specific capacity of the negative electrode. Using nano-silicon particles can alleviate expansion stress, but their extremely high specific surface area requires a large amount of binder, which also reduces the content of active material in the negative electrode and hinders lithium-ion conduction. Furthermore, if silicon-carbon materials and nano-silicon are combined in the negative electrode, the difference in particle size leads to loose particle packing, forming numerous pores inside the negative electrode, affecting the continuous conduction of lithium ions and consequently impacting the battery's rate performance. To ensure good lithium-ion conduction, a larger amount of solid electrolyte needs to be introduced, resulting in a decrease in battery capacity. Summary of the Invention

[0005] Therefore, it is necessary to provide a negative electrode, a solid-state battery, and an electrical device that, without sacrificing capacity, suppresses the volume expansion of silicon during charging and discharging, forms a continuous ion transport channel, and thus simultaneously improves the battery's capacity performance, rate performance, and cycle performance.

[0006] In a first aspect, this application provides a negative electrode sheet, the negative electrode sheet comprising: a negative current collector; and a negative active material layer disposed on at least one side surface of the negative current collector, the negative active material layer comprising silicon-carbon material particles, a first silicon particle, and a second silicon particle; the particle size D50 of the silicon-carbon material particles is greater than the particle size D50 of the first silicon particle, and the particle size D50 of the first silicon particle is greater than the particle size D50 of the second silicon particle; the first silicon particle has a porous structure.

[0007] In some embodiments, the ratio of the particle size D50 of the silicon carbide material particles to the particle size D50 of the first silicon particle is in the range of (5~15):1.

[0008] In some embodiments, the ratio of the particle size D50 of the silicon carbide material particles to the particle size D50 of the second silicon particles is in the range of (50~500):1.

[0009] In some embodiments, the particle size D50 of the silicon carbide material particles is 4 μm to 10 μm.

[0010] In some embodiments, the particle size D50 of the first silicon particle is 300 nm to 2 μm.

[0011] In some embodiments, the particle size D50 of the second silicon particle is 20 nm to 70 nm.

[0012] In some embodiments, the porosity of the first silicon particle is 10% to 50%.

[0013] In some embodiments, the mass ratio of silicon carbide material particles, first silicon particles, and second silicon particles is (50~70):(5~35):(5~30).

[0014] In some embodiments, the silicon-carbon material particles include: a porous carbon framework; and silicon material disposed within the pores of the porous carbon framework.

[0015] In some embodiments, the silicon-carbon material particles further include a silicon layer disposed on the surface of the porous carbon framework.

[0016] In some embodiments, the negative electrode active material layer further includes a binder, wherein the mass percentage of the binder in the negative electrode active material layer is ≤1%;

[0017] In some embodiments, the negative electrode active material layer further includes a solid electrolyte, wherein the mass percentage of the solid electrolyte in the negative electrode active material layer is ≤10%.

[0018] A second aspect of this application provides a solid-state battery, which includes the negative electrode provided in the first aspect above.

[0019] A third aspect of this application provides an electrical device comprising the solid-state battery provided in the second aspect above.

[0020] Compared with traditional technologies, this application has at least the following beneficial effects:

[0021] The negative electrode sheet provided in some embodiments of this application achieves dense packing of particles inside the negative electrode by compounding silicon-carbon material particles, first silicon particles, and second silicon particles with successively decreasing particle sizes. This utilizes the space-filling effect between multi-scale particles, eliminating the need to introduce large amounts of inactive materials (such as solid electrolytes or binders) to construct a highly efficient and continuous lithium-ion transport channel, with all three contributing to the capacity. Therefore, the dense packing structure formed by the particle size gradient compounding can increase the proportion of active material in the negative electrode, effectively improving the battery's capacity and rate performance.

[0022] The applicant's further research revealed that in the aforementioned densely packed structure, the medium-sized first silicon particle, as the main filling phase between the large-sized silicon-carbon material particles, undergoes volume expansion during charging and discharging, which is the main source of destructive stress in the entire densely packed structure, thereby limiting the cycle life of the battery.

[0023] Therefore, by utilizing the porous structure of the first silicon particle to provide space for its own volume expansion, the expansion stress is dissipated inward rather than being squeezed outward and damaged by the surrounding particles, effectively suppressing overall expansion and improving the cycle performance of the battery.

[0024] In summary, this application, through the synergistic effect of particle size gradient compounding and the porous structure of the first silicon particles, can suppress the volume expansion of silicon during charging and discharging without sacrificing capacity, forming continuous ion transport channels, thereby simultaneously improving the battery's capacity performance, rate performance, and cycle performance. Detailed Implementation

[0025] Reference will now be made to detailed embodiments of this application, one or more of which are described below. Each example is provided for explanation and not for limitation of this application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0026] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0027] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0028] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0033] A first aspect of this application provides a negative electrode sheet, comprising a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one surface of the negative current collector, and includes silicon-carbon material particles, first silicon particles, and second silicon particles. The particle size D50 of the silicon-carbon material particles is larger than the particle size D50 of the first silicon particles, and the particle size D50 of the first silicon particles is larger than the particle size D50 of the second silicon particles. The first silicon particles have a porous structure.

[0034] The negative electrode sheet provided in some embodiments of this application achieves dense packing of particles inside the negative electrode by compounding silicon-carbon material particles, first silicon particles, and second silicon particles with successively decreasing particle sizes. This utilizes the space-filling effect between multi-scale particles, eliminating the need to introduce large amounts of inactive materials (such as solid electrolytes or binders) to construct a highly efficient and continuous lithium-ion transport channel, with all three contributing to the capacity. Therefore, the dense packing structure formed by the particle size gradient compounding can increase the proportion of active material in the negative electrode, effectively improving the battery's capacity and rate performance.

[0035] The applicant's further research revealed that in the aforementioned densely packed structure, the medium-sized first silicon particle, as the main filling phase between the large-sized silicon-carbon material particles, undergoes volume expansion during charging and discharging, which is the main source of destructive stress in the entire densely packed structure, thereby limiting the cycle life of the battery.

[0036] Therefore, by utilizing the porous structure of the first silicon particle to provide space for its own volume expansion, the expansion stress is dissipated inward rather than being squeezed outward and damaged by the surrounding particles, effectively suppressing overall expansion and improving the cycle performance of the battery.

[0037] In summary, this application, through the synergistic effect of particle size gradient compounding and the porous structure of the first silicon particles, can suppress the volume expansion of silicon during charging and discharging without sacrificing capacity, forming continuous ion transport channels, thereby simultaneously improving the battery's capacity performance, rate performance, and cycle performance.

[0038] In this article, "silicon-carbon material particles" refers to composite material particles containing both carbon and silicon materials. The carbon material can buffer the volume expansion of silicon during charging and discharging, thereby improving electrode conductivity.

[0039] In this article, "first silicon particle", "second silicon particle", "silicon material" and "silicon layer" all refer to elemental silicon.

[0040] In this article, "particle size D50" refers to the particle size value corresponding to a cumulative particle size distribution percentage of 50%. Particle size D50 can be measured using test methods known in the art. As an example, the national standard GB / T19077-2016 can be referenced for characterization testing using a Malvern laser particle size analyzer.

[0041] In this article, "porosity" refers to the ratio of the volume of pores within a particle to the total volume of the particle. Porosity can be measured using methods known in the art. As an example, it can be measured using a fully automated true density analyzer, referring to the national standard GB / T 24586-2009. Specifically, porosity = (V1-V2) / V1*100%, where V1 refers to the apparent volume of the material, and V2 refers to the actual volume of the material. V1 can be tested using the mercury porosimetry method, and V2 can be tested using the nitrogen gas adsorption method.

[0042] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particle ranges from (5 to 15):1. For example, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the first silicon particle can be, but is not limited to, 5:1, 7:1, 9:1, 10:1, 13:1, and 15:1. Thus, by controlling the particle size ratio of the silicon-carbon material particles to the first silicon particle, the first silicon particle can be formed in the pores created by the accumulation of silicon-carbon material particles, significantly increasing the particle packing density inside the negative electrode, increasing the content of active material per unit volume, forming a more efficient and continuous lithium-ion transport channel, and thereby effectively improving the battery's capacity and rate performance.

[0043] In some embodiments, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles ranges from (50 to 500):1. Exemplarily, the ratio of the particle size D50 of the silicon-carbon material particles to the particle size D50 of the second silicon particles can be, but is not limited to, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, and 500:1. Thus, by controlling the particle size ratio of the silicon-carbon material particles to the second silicon particles, the second silicon particles can adhere to the surface of the silicon-carbon material particles, increasing the effective contact points between the particles and forming a more efficient and continuous lithium-ion transport channel, thereby effectively improving the rate performance of the battery.

[0044] In some embodiments, the particle size D50 of the silicon-carbon material particles is 4 μm to 10 μm. Exemplarily, the particle size D50 of the silicon-carbon material particles can be, but is not limited to, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm. Within the above particle size range, the silicon-carbon material particles can serve as the structural framework of the negative electrode, providing sufficient mechanical support for the entire electrode and improving the cycle performance of the battery.

[0045] In some embodiments, the particle size D50 of the first silicon particle is 300 nm to 2 μm. Exemplarily, the particle size D50 of the first silicon particle can be, but is not limited to, 300 nm, 600 nm, 1 μm, or 2 μm. Within the above particle size range, the first silicon particle can effectively fill the gaps formed by the accumulation of silicon-carbon material particles, and can also suppress its own volume expansion to a certain extent.

[0046] In some embodiments, the particle size D50 of the second silicon particle is 20 nm to 70 nm. Exemplarily, the particle size D50 of the second silicon particle can be, but is not limited to, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or 70 nm. Within the above particle size range, the second silicon particle, due to its nanoscale effect, can significantly reduce its volume expansion and improve the cycle performance of the battery.

[0047] Furthermore, by simultaneously controlling the particle size of silicon-carbon material particles, first silicon particles, and second silicon particles, a composite material is formed in which the second silicon particles are attached to the surface of silicon-carbon material particles, and the first silicon particles are distributed in the gaps formed by adjacent composite materials. This fully leverages the hierarchical filling effect, significantly increases the packing density of particles inside the negative electrode, increases the content of active material per unit volume, and simultaneously forms an efficient and continuous lithium-ion transport channel, thereby effectively improving the battery's capacity and rate performance.

[0048] In some embodiments, the porosity of the first silicon particle is 10% to 50%. Exemplarily, the porosity of the first silicon particle can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%. In this way, by controlling the porosity of the first silicon particle, its own volume expansion can be fully absorbed while ensuring the structural stability of the first silicon particle.

[0049] In some embodiments, the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is (50~70):(5~35):(5~30). Exemplarily, the mass ratio can be, but is not limited to, 50:20:30, 50:35:15, 60:10:30, 60:20:20, 70:10:20, or 70:25:5. Thus, by controlling the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles, the capacity performance, rate performance, and cycle performance of the battery are synergistically improved. Within the above mass ratio range, the silicon-carbon material particles, as the structural framework, dominate, providing excellent structural stability and an ion-conducting network foundation for the negative electrode. Simultaneously, the first and second silicon particles, as fillers, occupy a considerable mass, effectively improving the overall specific capacity of the negative electrode. Furthermore, this mass ratio range ensures that while forming a densely packed structure, it prevents a decrease in cycle stability due to an imbalance in the proportion of any component.

[0050] In some embodiments, the silicon-carbon material particles comprise a porous carbon framework and a silicon material. The silicon material is disposed within the pores of the porous carbon framework. Thus, the porous carbon framework provides space for the expansion of the silicon material, while simultaneously improving the electronic contact of the internal silicon material by utilizing the excellent conductivity of the carbon framework itself.

[0051] In some embodiments, the silicon-carbon material particles further include a silicon layer. The silicon layer is disposed on the surface of the porous carbon framework. In this way, the silicon layer enhances the contact between the silicon material in the silicon-carbon material particles and the first and second silicon particles, forming a continuous ion-conducting pathway and further improving the rate performance of the battery.

[0052] In some embodiments, the silicon carbide material particles are irregularly shaped or spherical. Furthermore, the spherical shape of the silicon carbide material particles is advantageous for stacking.

[0053] In some embodiments, the negative electrode active material layer may optionally include a binder, wherein the binder comprises ≤1% by mass in the negative electrode active material layer. As an example, the binder may include at least one of vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0054] In some embodiments, the negative electrode active material layer may optionally include a solid electrolyte, wherein the mass percentage of the solid electrolyte in the negative electrode active material layer is ≤10%. Thus, by performing a silicon material particle size gradient compounding in the negative electrode, the amount of solid electrolyte used can be effectively reduced, the energy density of the battery can be improved, and the side reactions between the solid electrolyte and silicon material can be reduced, which is beneficial to further improving the cycle performance of the battery.

[0055] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, conductive carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0056] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0057] A second aspect of this application provides a solid-state battery, which includes the negative electrode provided in the first aspect above.

[0058] Solid-state batteries consist of a positive electrode, a negative electrode, and a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode.

[0059] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector.

[0060] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0061] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0063] In some embodiments, the positive electrode active material layer may optionally include a binder. As examples, the binder may include at least one of vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0064] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, conductive carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0065] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto the positive current collector, and obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0066] In some embodiments, the solid electrolyte membrane comprises a solid electrolyte and a binder. As an example, the binder may include at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polypropylene, polyethylene, and polyimide.

[0067] In some embodiments, the solid electrolyte is an inorganic solid electrolyte, including one or more of oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, hydride solid electrolytes, boride solid electrolytes, and nitride solid electrolytes.

[0068] Oxide solid electrolytes include one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and perovskite-type ceramics. For example, one or more garnet ceramics include, but are not limited to, Li. 6.5 La3Zr 1.75 Te 0.25 O 12 Li7La3Zr2O 12 Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 Li 6.85 La 2.9 Ca 0.1 Zr1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 one or more of those in. One or more LISICON-type oxides include, but are not limited to, Li 14 Zn(GeO4)4, Li 3+x (P 1-x Si x )O4 (where 0 < x < 1), Li 3+x Ge x V 1-x O4 (where 0 < x < 1). One or more NASICON-type oxides can be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, one or more NASICON-type oxides include, but are not limited to, Li 1+x Al x Ge 2-x (PO4)3 (LAGP) (where 0 ≤ x ≤ 2), Li 1+x Al x Ti 2-x (PO4)3 (LATP) (where 0 ≤ x ≤ 2), Li 1+ x Y x Zr 2-x (PO4)3 (LYZP) (where 0 ≤ x ≤ 2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3. One or more perovskite-type ceramics include, but are not limited to, Li 0.33 La 0.56 TiO3, LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x = 0.75y and 0.60 < y < 0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3, Li3x La (2 / 3-x) one or more of TiO3 (where 0 < x < 0.25).

[0069] Sulfide solid electrolytes include, but are not limited to, Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3, Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li 10 (Ge 0.5 Sn 0.5 )P2S 12 、Li 10 (Si 0.5 Sn 0.5 )P2S 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is selected from Cl, Br, or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0070] Halide solid electrolytes include, but are not limited to, one or more of Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Br x (where 0 < x < 1).

[0071] Boride solid electrolytes include, but are not limited to, one or more of Li2B4O7, Li2O-(B2O3)-(P2O5).

[0072] Nitride solid electrolytes include, but are not limited to, one or more of Li3N, Li7PN4, LiSi2N3, LiPON.

[0073] Hydride solid electrolytes include, but are not limited to, one or more of Li3AlH6, LiBH4, LiBH4-LiX (where X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2.

[0074] In some embodiments, the inorganic solid electrolyte can also be one or more metal oxide particles or lithium-containing compounds, including, but not limited to, one or more of Al2O3, SiO2, TiO2, LiNbO3, Li4Ti5O4, Li3PO4.

[0075] In some embodiments, the solid electrolyte further includes a partial polymer solid electrolyte, a composite solid electrolyte composed of the polymer solid electrolyte and the inorganic solid electrolyte. In the embodiments of the present application, there is no special requirement for the mass ratio of the inorganic solid electrolyte and the polymer solid electrolyte in the composite solid electrolyte, and the user can design according to actual needs. Among them, the polymer solid electrolyte can be at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0076] In a third aspect of the present application, an electrical device is provided, and the electrical device includes the solid-state battery provided in the second aspect above. The solid-state battery provides power for the electrical device.

[0077] The electrical device used in this application is not particularly limited and can be any electrical device known in the prior art. For example, the electrical device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

[0078] The present application will be further described below with reference to specific embodiments and comparative examples.

[0079] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0080] Example 1

[0081] Negative electrode plate:

[0082] (1) Add silicon carbon material particles, first silicon particles and second silicon particles to N-methylpyrrolidone solvent containing binder PVDF in a mass ratio of 70:10:20, mix them with a homogenizer to prepare negative electrode slurry.

[0083] The silicon-carbon material particles include a porous carbon framework, silicon material disposed within the pores of the porous carbon framework, and a silicon layer disposed on the surface of the porous carbon framework. The particle size D50 of the silicon-carbon material particles is 6 μm. The first silicon particle has a particle size D50 of 1 μm and has a porous structure with a porosity of 20%. The second silicon particle has a particle size D50 of 35 nm. Based on a solid content of 100% for the negative electrode slurry, the mass percentage of PVDF is 1%.

[0084] (2) The negative electrode slurry is coated onto a 10 μm thick copper film using a scraper, and then vacuum dried overnight at 80°C to remove the solvent, forming a negative electrode active material layer. The material is then cut into a disc shape to prepare the negative electrode sheet.

[0085] Solid-state batteries:

[0086] A solid-state battery is obtained by sequentially stacking and assembling the positive electrode, the solid electrolyte membrane, and the aforementioned negative electrode.

[0087] The positive electrode sheet is prepared by the following method: LiNi 0.8 Co 0.1 Mn0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and then fiberized before being rolled to obtain the positive electrode.

[0088] The solid electrolyte membrane was prepared by mixing sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene at a mass ratio of 96:4 to obtain a mixture, grinding for 30 min to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0089] Example 2

[0090] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0091] In step (1), the porosity of the first silicon particle is 10%.

[0092] Example 3

[0093] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0094] In step (1), the porosity of the first silicon particle is 50%.

[0095] Example 4

[0096] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0097] In step (1), the particle size D50 of the first silicon particle is 1.5 μm.

[0098] Example 5

[0099] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0100] In step (1), the particle size D50 of the first silicon particle is 600 nm.

[0101] Example 6

[0102] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0103] In step (1), the particle size D50 of the first silicon particle is 4 μm.

[0104] Example 7

[0105] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0106] In step (1), the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is 60:20:20.

[0107] Example 8

[0108] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0109] In step (1), the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is 60:10:30.

[0110] Example 9

[0111] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0112] In step (1), the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is 50:35:15.

[0113] Example 10

[0114] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0115] In step (1), the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is 50:20:30.

[0116] Example 11

[0117] The preparation methods of the negative electrode sheet and solid-state battery in this embodiment are basically the same as those in Example 1, except that:

[0118] In step (1), the mass ratio of silicon-carbon material particles, first silicon particles, and second silicon particles is 40:30:30.

[0119] Comparative Example 1

[0120] Negative electrode plate:

[0121] (1) Add silicon carbon material particles and second silicon particles to N-methylpyrrolidone solvent containing binder PVDF at a mass ratio of 70:30, mix using a homogenizer to prepare negative electrode slurry.

[0122] The silicon-carbon material particles include a porous carbon skeleton, silicon material disposed in the pores of the porous carbon skeleton, and a silicon layer disposed on the surface of the porous carbon skeleton. The particle size D50 of the silicon-carbon material particles is 6 μm; the particle size D50 of the second silicon particles is 35 nm; and the mass ratio of PVDF is 1% based on the solid content of the negative electrode slurry being 100%.

[0123] (2) The negative electrode slurry is coated onto a 10 μm thick copper film using a scraper, and then vacuum dried overnight at 80°C to remove the solvent, forming a negative electrode active material layer. The material is then cut into a disc shape to prepare the negative electrode sheet.

[0124] Solid-state batteries:

[0125] A solid-state battery is obtained by sequentially stacking and assembling the positive electrode, the solid electrolyte membrane, and the aforementioned negative electrode.

[0126] The positive electrode sheet is prepared by the following method: LiNi 0.8 Co 0.1 Mn 0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and then fiberized before being rolled to obtain the positive electrode.

[0127] The solid electrolyte membrane was prepared by mixing sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene at a mass ratio of 96:4 to obtain a mixture, grinding for 30 min to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0128] Comparative Example 2

[0129] Negative electrode plate:

[0130] (1) Add silicon carbon material particles, first silicon particles and second silicon particles to N-methylpyrrolidone solvent containing binder PVDF in a mass ratio of 70:10:20, mix them with a homogenizer to prepare negative electrode slurry.

[0131] The silicon-carbon material particles include a porous carbon skeleton, silicon material disposed in the pores of the porous carbon skeleton, and a silicon layer disposed on the surface of the porous carbon skeleton. The particle size D50 of the silicon-carbon material particles is 6 μm. The particle size D50 of the first silicon particle is 1 μm. The first silicon particle is a solid silicon particle with a porosity close to 0. The particle size D50 of the second silicon particle is 35 nm. Based on the solid content of the negative electrode slurry being 100%, the mass ratio of PVDF is 1%.

[0132] (2) The negative electrode slurry is coated onto a 10 μm thick copper film using a scraper, and then vacuum dried overnight at 80°C to remove the solvent, forming a negative electrode active material layer. The material is then cut into a disc shape to prepare the negative electrode sheet.

[0133] Solid-state batteries:

[0134] A solid-state battery is obtained by sequentially stacking and assembling the positive electrode, the solid electrolyte membrane, and the aforementioned negative electrode.

[0135] The positive electrode sheet is prepared by the following method: LiNi 0.8 Co 0.1 Mn 0.1 O2, Li6PS5Cl, polyaniline and polytetrafluoroethylene (PTFE) were mixed in a weight ratio of 78:19.5:2:0.5 and then fiberized before being rolled to obtain the positive electrode.

[0136] The solid electrolyte membrane was prepared by mixing sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene at a mass ratio of 96:4 to obtain a mixture, grinding for 30 min to obtain a sulfide solid electrolyte sheet, and hot rolling the obtained sulfide solid electrolyte sheet to prepare a solid electrolyte membrane.

[0137] Performance testing

[0138] Electrochemical tests were performed on the solid-state batteries of the above embodiments and comparative examples:

[0139] (1) Ratio performance test

[0140] At 25°C, a fully charged battery is discharged at a current of 0.1C to a cutoff voltage of 3.0V, and the measured capacity is C0. At 25°C, a fully charged battery is discharged at a current of 1C to a cutoff voltage of 3.0V, and the measured capacity is C1. C1 / C0 is the capacity retention rate at 1C.

[0141] (2) Cyclic performance test

[0142] Charge to 4.25V at a charging current of 0.33C, then charge at a constant voltage until the cutoff current is 0.05C. Then discharge to 3.0V at 0.33C, cycling until the capacity decays to 80% of the initial capacity, and record the number of cycles.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145]

[0146] As shown in Table 1, comparing Examples 1-11 and Comparative Examples 1-2, it can be seen that the negative electrode sheets provided in some embodiments of this application improve the rate performance and cycle performance of the battery.

[0147] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A negative electrode sheet, characterized by, Comprise: a negative current collector; and a negative active material layer disposed on at least one side surface of the negative current collector, the negative active material layer comprising silicon-carbon material particles, first silicon particles, and second silicon particles; a particle size D50 of the silicon-carbon material particles is greater than a particle size D50 of the first silicon particles, the particle size D50 of the first silicon particles is greater than a particle size D50 of the second silicon particles, the particle size D50 of the silicon-carbon material particles is 4 μm to 10 μm, the particle size D50 of the first silicon particles is 300 nm to 2 μm, and the particle size D50 of the second silicon particles is 20 nm to 70 nm; the first silicon particles have a porous structure, and a porosity of the first silicon particles is 10% to 50%.

2. The negative electrode sheet according to claim 1, characterized by a mass ratio of the silicon-carbon material particles, the first silicon particles, and the second silicon particles is (50 to 70):(5 to 35):(5 to 30).

3. The negative electrode sheet according to claim 1, characterized by the silicon-carbon material particles comprise: a porous carbon skeleton; and a silicon material disposed in pores of the porous carbon skeleton.

4. The negative electrode sheet according to claim 3, characterized by the silicon-carbon material particles further comprise: a silicon layer disposed on a surface of the porous carbon skeleton.

5. The negative electrode sheet according to claim 1, wherein At least one of the following conditions is satisfied: (1) the negative active material layer further comprises a binder, and a mass percentage of the binder in the negative active material layer is ≤1%; (2) the negative active material layer further comprises a solid-state electrolyte, and a mass percentage of the solid-state electrolyte in the negative active material layer is ≤10%.

6. A solid state battery, characterized by comprise the negative electrode sheet according to any one of claims 1 to 5.

7. An electrical device, characterized by comprise the solid-state battery according to claim 6.

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