Negative pole piece, solid-state battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative pole piece, a solid-state battery and an electric device. The negative pole piece comprises a negative current collector; the negative electrode active material layer is arranged on the surface of at least one side of the negative electrode current collector, and the negative electrode active material layer comprises silicon carbon material particles and silicon particles; wherein the silicon-carbon material particles are of spherical structures, and the sphericity degree of the silicon-carbon material particles is larger than or equal to 96%. According to the negative pole piece provided by some embodiments of the invention, the spherical silicon-carbon material particles with high sphericity (gt; 96%) and the silicon particles are compounded to serve as the negative active material, so that the rate performance, the capacity performance and the cycle performance of the battery are effectively 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 requirements for the safety performance of secondary batteries, solid electrolytes are now often chosen to replace liquid electrolytes in the preparation of all-solid-state batteries.

[0003] In traditional technologies, the interface between the negative electrode and the solid electrolyte membrane in solid-state batteries often has defects. Due to the poor surface flatness of the electrode, contact voids are formed between the negative electrode and the solid electrolyte membrane in local areas, hindering the effective transport of ions. This not only reduces the utilization rate of the negative electrode active material but also significantly increases the interfacial impedance, thereby affecting the rate performance, capacity performance, and cycle performance of the battery. Summary of the Invention

[0004] Therefore, it is necessary to provide a negative electrode sheet, a solid-state battery, and an electrical device to improve the flatness of the electrode surface, reduce the contact void area between the electrode sheet and the solid electrolyte membrane, and improve the cycle performance, capacity performance, and cycle life of the battery.

[0005] 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 and silicon particles; wherein the silicon carbon material particles have a spherical structure and the sphericity of the silicon carbon material particles is ≥96%.

[0006] In some embodiments, the silicon-carbon particulate material includes: a porous carbon framework; and a silicon material disposed within the pores of the porous carbon framework, wherein the porous carbon framework has a spherical structure.

[0007] In some embodiments, the particle size D50 of the silicon carbide material particles is 1 μm to 10 μm.

[0008] In some embodiments, the particle size D50 of the silicon carbide material particles is 2 μm to 3 μm.

[0009] In some embodiments, the mass ratio of silicon carbide material particles to silicon particles is (1.5~9):1.

[0010] In some embodiments, the particle size D50 of the silicon nanoparticles is 20 nm to 70 nm.

[0011] In some embodiments, the compaction density of the negative electrode active material layer is 0.5 g / cm³. 3 ~1 g / cm 3 .

[0012] In some embodiments, the thickness of the negative electrode active material layer is 25 μm to 30 μm.

[0013] In some implementations, the surface roughness of the negative electrode active material layer is <6 μm.

[0014] A second aspect of this application provides a solid-state battery, the solid-state battery comprising: a positive electrode; a negative electrode provided in the first aspect; and a solid electrolyte membrane disposed between the positive electrode and the negative electrode.

[0015] A third aspect of this application provides an electrical device comprising the solid-state battery provided in the second aspect above.

[0016] Compared with traditional technologies, this application has at least the following beneficial effects:

[0017] The negative electrode provided in some embodiments of this application uses spherical silicon-carbon material particles with high sphericity (≥96%). Compared with the irregular and angular silicon-carbon material particles in the traditional technology, the silicon-carbon material particles with high sphericity have regular shapes and can form a low-roughness surface when stacked, which improves the flatness of the electrode surface, reduces the contact void between the electrode and the solid electrolyte membrane, provides an efficient transport channel for lithium ions, reduces the interface impedance, and thus improves the rate performance and cycle performance of the battery.

[0018] Furthermore, due to the improved interfacial contact, not only the spherical silicon-carbon particles themselves, but also the silicon particles in contact with them, which are the main contributors to capacity, can fully participate in the electrochemical reaction, thereby improving the utilization rate of active materials in the negative electrode and thus improving the capacity performance of the battery.

[0019] In summary, the negative electrode sheets provided in some embodiments of this application effectively improve the rate performance, capacity performance and cycle performance of the battery by using spherical silicon-carbon material particles with high sphericity (>96%) combined with silicon particles as the negative electrode active material. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In this article, "silicon particles", "silicon materials" and "silicon layers" all refer to elemental silicon.

[0030] A first aspect of this application provides a negative electrode sheet, which includes 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 the negative active material layer includes silicon carbon material particles and silicon particles. The silicon carbon material particles have a spherical structure, and the sphericity of the silicon carbon material particles is ≥96%.

[0031] The negative electrode provided in some embodiments of this application uses spherical silicon-carbon material particles with high sphericity (≥96%). Compared with the irregular and angular silicon-carbon material particles in the traditional technology, the silicon-carbon material particles with high sphericity have regular shapes and can form a low-roughness surface when stacked, which improves the flatness of the electrode surface, reduces the contact void between the electrode and the solid electrolyte membrane, provides an efficient transport channel for lithium ions, reduces the interface impedance, and thus improves the rate performance and cycle performance of the battery.

[0032] Furthermore, due to the improved interfacial contact, not only the spherical silicon-carbon particles themselves, but also the silicon particles in contact with them, which are the main contributors to capacity, can fully participate in the electrochemical reaction, thereby improving the utilization rate of active materials in the negative electrode and thus improving the capacity performance of the battery.

[0033] In summary, the negative electrode sheets provided in some embodiments of this application effectively improve the rate performance, capacity performance and cycle performance of the battery by using spherical silicon-carbon material particles with high sphericity (>96%) combined with silicon particles as the negative electrode active material.

[0034] In some embodiments, the silicon-carbon particulate material includes 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.

[0035] In some of these embodiments, the porous carbon framework is a spherical structure.

[0036] In some embodiments, the silicon material is amorphous silicon. Thus, using amorphous silicon to fill the pores of the porous carbon framework improves the uniformity of silicon material filling, further enhances the sphericity of the silicon-carbon particles, forms a negative electrode active material layer with lower surface roughness, improves the flatness of the electrode surface, further reduces interfacial impedance, and improves the rate performance and cycle performance of the battery.

[0037] In some embodiments, the silicon-carbon material particles further include a silicon layer. The silicon layer is disposed on the outer surface of the porous carbon framework. Thus, the silicon layer enhances the contact between silicon materials and silicon particles within the silicon-carbon material particles, forming a continuous ion-conducting pathway and further improving the rate performance of the battery.

[0038] In some embodiments, the particle size D50 of the silicon-carbon material particles is 1 μm to 10 μm. Exemplarily, the particle size D50 of the silicon-carbon material can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm. Further, the particle size D50 of the silicon-carbon material particles is 2 μm to 3 μm. Within the above particle size range, the silicon-carbon material particles are smaller and have a more uniform particle size distribution, which helps to form a smoother surface, resulting in a negative electrode active material layer with lower surface roughness, improving the flatness of the electrode surface, further reducing interfacial impedance, and improving the rate performance and cycle performance of the battery.

[0039] In some embodiments, silicon-carbon material particles are prepared using the following steps:

[0040] S1. Disperse carbon fine powder in a mother liquor containing organic carbon precursor, heat and polymerize, and then perform solid-liquid separation to prepare spherical carbon precursor.

[0041] S2. Carbonize the spherical carbon precursor to prepare spherical carbon particles.

[0042] S3. Activate and create pores in spherical carbon particles to prepare a spherical porous carbon framework.

[0043] S4. Silicon source is deposited into the pores of a spherical porous carbon framework to prepare silicon-carbon material particles.

[0044] In some specific embodiments, the carbon fine powder includes one or more carbonized products of resin, asphalt, and coconut shell; the organic carbon precursor includes one or more of polyacrylonitrile and resin; and the heating polymerization temperature is 150°C to 450°C.

[0045] In some embodiments, the silicon particles are nano-silicon particles. These nano-silicon particles can fill the gaps between silicon-carbon material particles or adhere to the surface of the silicon-carbon material particles, maximizing the use of the limited space inside the electrode, increasing the compaction density of the negative electrode active material layer, and forming a more continuous ion-conducting pathway. Lithium ions can be transported within the negative electrode via the nano-silicon particles, further enhancing the lithium-ion transport rate. Simultaneously, due to their nanoscale effect, the nano-silicon particles can effectively release internal stress, and combined with the external constraints provided by the silicon-carbon material particles, jointly suppress the damage to the overall electrode structure caused by volume expansion, thereby improving the battery's cycle performance.

[0046] In some embodiments, the particle size D50 of the silicon nanoparticles is 20 nm to 70 nm. Exemplarily, the particle size of the silicon nanoparticles can be, but is not limited to, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, and 70 nm.

[0047] In some embodiments, the compaction density of the negative electrode active material layer is 0.5 g / cm³. 3 ~1 g / cm 3 For example, the compaction density of the negative electrode active material layer can be, but is not limited to, 0.5 g / cm³. 3 0.6 g / cm 3 0.7 g / cm 3 0.8g / cm 3 0.9 g / cm 3 1 g / cm 3 Because this application uses silicon-carbon material particles with high sphericity, they can be densely packed in the negative electrode, increasing the compaction density of the negative electrode active material layer, thereby improving the energy density and long-term cycle stability of the battery.

[0048] In some embodiments, the thickness of the negative electrode active material layer is 25 μm to 30 μm. Exemplarily, the thickness of the negative electrode active material layer can be, but is not limited to, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, or 30 μm.

[0049] In some embodiments, the surface roughness of the negative electrode active material layer is <6 μm. Exemplarily, the surface roughness of the negative electrode active material layer can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or 5.5 μm. Thus, a surface roughness of <6 μm allows for tight adhesion with the solid electrolyte membrane, reducing the contact void between the electrode and the solid electrolyte membrane, providing an efficient transport channel for lithium ions, reducing interfacial impedance, and thereby improving the rate performance and cycle performance of the battery.

[0050] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper 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 (copper, copper 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.).

[0051] In some embodiments, the negative 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.

[0052] 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.

[0053] 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)).

[0054] A second aspect of this application provides a solid-state battery, comprising a positive electrode, a negative electrode as described in the first aspect, and a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode.

[0055] 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.

[0056] 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.

[0057] 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.).

[0058] 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.

[0059] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of 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), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0060] 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.

[0061] In some embodiments, the positive electrode active material layer may optionally include a solid electrolyte.

[0062] 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.

[0063] In some embodiments, the solid electrolyte membrane includes a solid electrolyte and a binder.

[0064] 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.

[0065] 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 Zr 1.75 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 the following. One or more LISICON-type oxides, including but not limited to Li. 14 Zn(GeO4)4, Li 3+x (P 1-x Six )O4 (where 0 < x < 1), Li 3+x Ge x V 1-x O4 (where 0 < x < 1), or one or more of them. 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, or one or more of them. 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, Li 3x La (2 / 3-x) TiO3 (where 0 < x < 0.25), or one or more of them.

[0066] 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 S 12 , Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 , Li 10 SiP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , (1-x) P2S 5-x Li2S (where 0.5 ≤ x ≤ 0.7) or more of them.

[0067] Halide solid electrolytes include but are not limited to Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Br x (where 0 < x < 1) or more of them.

[0068] Boride solid electrolytes include but are not limited to Li2B4O7, Li2O-(B2O3)-(P2O5) or more of them.

[0069] Nitride solid electrolytes include, but are not limited to, one or more of Li3N, Li7PN4, LiSi2N3, and LiPON.

[0070] 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, and LiBH4-LiNH2.

[0071] In some embodiments, the inorganic solid electrolyte may 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, and Li3PO4.

[0072] In some embodiments, the solid electrolyte further includes a portion of a polymer solid electrolyte, or a composite solid electrolyte composed of a polymer solid electrolyte and an inorganic solid electrolyte. In the embodiments of this application, the mass ratio of the inorganic solid electrolyte to the polymer solid electrolyte in the composite solid electrolyte is not particularly required; users can design it according to actual needs. The polymer solid electrolyte can be at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0073] A third aspect of this application provides an electrical device that includes the solid-state battery provided in the second aspect above. The solid-state battery provides power to the electrical device.

[0074] 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.

[0075] The present application will be further described below with reference to specific embodiments and comparative examples.

[0076] 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.

[0077] Example 1

[0078] Silicon-carbon material particles:

[0079] (1) 50g of carbon fine powder obtained from the carbonization product of phenolic resin was uniformly dispersed in 500g of N,N-dimethylformamide mother liquor containing 40wt% polyacrylonitrile, and the mixture was heated and polymerized at 280℃ for 6 h. Then, solid-liquid separation was carried out to obtain spherical carbon precursor.

[0080] (2) The spherical carbon precursor was carbonized at 500℃ for 1 h to prepare spherical carbon particles.

[0081] (3) Use KOH as an activating pore-forming agent to activate and form pores in spherical carbon particles, and then wash with acid to prepare a spherical porous carbon skeleton.

[0082] (4) Using porous carbon as a substrate, silane is introduced as the silicon source gas and deposition is carried out to prepare silicon carbon material particles with spherical structure.

[0083] Tests showed that the sphericity of the silicon-carbon material particles was 98%, and the particle size D50 was 8 μm.

[0084] Negative electrode plate:

[0085] Spherical silicon-carbon material particles and silicon material particles are dry-mixed at a mass ratio of 2.5:1 to form a mixture. The mixture is then mixed evenly with binder PVDF and solvent NMP to form a negative electrode slurry. The negative electrode slurry is coated onto copper foil and dried to form a negative electrode sheet.

[0086] Solid-state batteries:

[0087] A solid-state battery is obtained by sequentially stacking and assembling the positive electrode, the solid electrolyte membrane, and the aforementioned negative electrode.

[0088] 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.

[0089] 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.

[0090] Example 2

[0091] In this embodiment, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0092] In step (1), the heating polymerization reaction time is 4.5 h; the particle size D50 of the silicon-carbon material particles prepared therefrom is 5 μm.

[0093] Example 3

[0094] In this embodiment, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0095] In step (1), the heating polymerization reaction time is 3.5 h; the particle size D50 of the silicon-carbon material particles prepared therefrom is 3 μm.

[0096] Example 4

[0097] In this embodiment, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0098] In step (1), the heating polymerization reaction time is 3h; the particle size D50 of the silicon-carbon material particles prepared therefrom is 2 μm.

[0099] Example 5

[0100] In this embodiment, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0101] In step (1), the mass fraction of polyacrylonitrile is 35 wt%; the sphericity of the silicon-carbon material particles prepared therefrom is 96%, and the particle size D50 is 3 μm.

[0102] Example 6

[0103] In this embodiment, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0104] In step (1), the mass fraction of polyacrylonitrile is 45 wt%; the sphericity of the silicon-carbon material particles prepared therefrom is 99%, and the particle size D50 is 3 μm.

[0105] Comparative Example 1

[0106] Silicon-carbon material particles:

[0107] (1) Carbon fine powder obtained by carbonizing 50g of phenolic resin carbonization product was carbonized at 500℃ for 1 h to prepare spherical carbon particles.

[0108] (2) The spherical carbon particles were activated and pore-forming by KOH activating pore-forming agent, and then acid washed to prepare a spherical porous carbon skeleton.

[0109] (3) Using porous carbon as a substrate, silane is introduced as the silicon source gas and deposited to prepare silicon carbon material particles.

[0110] Negative electrode plate:

[0111] Silicon carbon material particles and silicon material particles are dry-mixed at a mass ratio of 2.5:1 to form a mixture. The mixture is then mixed evenly with binder PVDF and solvent NMP to form a negative electrode slurry. The negative electrode slurry is coated onto copper foil and dried to form a negative electrode sheet.

[0112] Solid-state batteries:

[0113] A solid-state battery is obtained by sequentially stacking and assembling the positive electrode, the solid electrolyte membrane, and the aforementioned negative electrode.

[0114] 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.

[0115] 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.

[0116] Comparative Example 2

[0117] In this comparative example, the silicon-carbon material particles, negative electrode sheet, and solid-state battery are basically the same as in Example 1, except that:

[0118] In step (1), the amount of ethylene tar pitch used is 130g; the sphericity of the silicon carbon material particles prepared therefrom is 90%, the particle size D50 is 3 μm, and the Dmax is 10 μm.

[0119] Performance testing

[0120] (1) Sphericity test

[0121] The prepared porous silicon-carbon material was imaged using a scanning electron microscope (SEM). The ratio of the length to the width of the porous silicon-carbon material particles in the SEM image was measured, and the average value was calculated from 10 particles.

[0122] (2) Roughness test

[0123] Take the edge and center regions of the negative electrode sheet, prepare cross-sectional samples, obtain scanning electron microscope images, take five regions for each region, calculate the distance between the highest and lowest points of the interface, and take the average value as the roughness of the negative electrode sheet.

[0124] (3) Particle size test

[0125] D50 refers to the particle size value corresponding to a material's cumulative particle size distribution percentage reaching 50%.

[0126] The particle size D50 was determined according to the national standard GB / T 19077-2016 and characterized using a Malvern laser particle size analyzer.

[0127] (4) Electrochemical performance testing

[0128] The discharge capacity of a 0.1C battery is: at 25°C, a fully charged battery is discharged at a current of 0.1C to a cutoff voltage of 3.0V.

[0129] The discharge capacity of a 1C battery: At 25℃, a fully charged battery is discharged at a 1C current to a cutoff voltage of 3.0V. Capacity retention rate (1C / 0.1C) = discharge capacity of the 1C battery / discharge capacity of the 0.1C battery.

[0130] Capacity retention after 500 cycles: Charge at 0.1C to the termination voltage at 25℃, cut-off current 0.05C, and let stand for 30 min; discharge at 0.1C to the final discharge voltage, record the discharge capacity, and let stand for 30 min; repeat the charge-discharge cycle for 500 cycles and record the data.

[0131] The test results are shown in Table 1.

[0132] Table 1

[0133]

[0134] As shown in Table 1, by comparing Examples 1-6 and Comparative Examples 1-2, it can be seen that the negative electrode sheets provided in some embodiments of this application use silicon-carbon material particles with high sphericity (≥96%). The particles have regular shapes, the particle size can be effectively reduced, and the particle size distribution is uniform. At the same time, a negative electrode active material layer with low surface roughness is formed, which improves the capacity performance, rate performance and cycle performance of the battery.

[0135] 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.

[0136] 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 in that, include: Negative electrode current collector; as well as A negative electrode active material layer is disposed on at least one side surface of the negative electrode current collector, and the negative electrode active material layer includes silicon carbon material particles and silicon particles; The silicon-carbon material particles are spherical, and the sphericity of the silicon-carbon material particles is ≥96%.

2. The negative electrode sheet according to claim 1, characterized in that, The silicon-carbon particulate material includes: Porous carbon framework; and Silicon material is disposed within the pores of the porous carbon framework; The porous carbon framework has a spherical structure.

3. The negative electrode sheet according to claim 2, characterized in that, The particle size D50 of the silicon-carbon material particles is 1 μm to 10 μm.

4. The negative electrode sheet according to claim 3, characterized in that, The particle size D50 of the silicon-carbon material particles is 2 μm to 3 μm.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that, The mass ratio of the silicon carbide material particles to the silicon particles is (1.5~9):

1.

6. The negative electrode sheet according to any one of claims 1 to 4, characterized in that, The silicon particles are nano-silicon particles.

7. The negative electrode sheet according to claim 6, characterized in that, The particle size D50 of the nano-silicon particles is 20 nm to 70 nm.

8. The negative electrode sheet according to any one of claims 1 to 4, characterized in that, The negative electrode active material layer satisfies at least one of the following conditions: (1) The compaction density of the negative electrode active material layer is 0.5 g / cm³. 3 ~1 g / cm 3 ; (2) The thickness of the negative electrode active material layer is 25 μm to 30 μm; (3) The surface roughness of the negative electrode active material layer is <6 μm.

9. A solid-state battery, characterized in that, include: Positive electrode sheet; The negative electrode sheet as described in any one of claims 1 to 8; as well as A solid electrolyte membrane is disposed between the positive electrode and the negative electrode.

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

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