Porous silicon negative electrode, preparation method thereof and solid-state battery

Abstract

The invention belongs to the technical field of batteries, and relates to a porous silicon negative electrode, a preparation method thereof and a solid-state battery. The porous silicon negative electrode comprises a porous silicon negative electrode active material, an inorganic solid electrolyte, a conductive agent and a binder, the porous silicon negative electrode active material comprises a porous silicon skeleton formed by in-situ growth of carbon nanotubes, and organic and inorganic electrolytes distributed inside and outside pores of the porous silicon skeleton; the organic-inorganic electrolyte comprises an organic polymer solid electrolyte, an inorganic solid electrolyte and a lithium salt. The invention also discloses a solid-state battery adopting the porous silicon negative electrode, the solid-state battery provided by the invention has better cycle performance and rate capability, and the expansion rate of a negative electrode plate is obviously reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a porous silicon anode, its preparation method, and a solid-state battery. Background Technology

[0002] During the lithium insertion / extraction process, silicon anode materials repeatedly expand and contract. The extreme volume expansion can lead to two problems: first, the silicon particles become pulverized and fail, resulting in poor electrical contact between the silicon particles and the conductive agent or current collector, or even detachment from the electrode; second, it can cause the SEI film to continuously rupture and regenerate. This process consumes a large amount of active lithium and electrolyte, and forms a thick and uneven SEI film, thereby accelerating the capacity decay and aging of the battery. All of these defects are caused by the volume expansion of the silicon anode material itself during the lithium insertion / extraction process, resulting in problems such as low initial efficiency, electrode expansion, loss of effective materials, rapid cycle decay, and low conductivity, ultimately leading to the complete failure of the battery. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a porous silicon anode, in which the active material is based on a porous silicon framework grown in situ from carbon nanotubes, and organic and inorganic electrolytes are distributed inside and outside the porous silicon framework, thereby improving silicon ion conductivity and electronic conductivity, reducing silicon anode expansion, and improving the cycle performance of solid-state batteries.

[0004] One objective of this invention is achieved through the following technical solution:

[0005] A porous silicon anode includes a porous silicon anode active material, an inorganic solid electrolyte, a conductive agent, and a binder.

[0006] The porous silicon anode active material includes a porous silicon framework grown in situ from carbon nanotubes, and organic and inorganic electrolytes distributed inside and outside the pores of the porous silicon framework.

[0007] The average pore size of the porous silicon framework grown in situ from carbon nanotubes is >500 nm.

[0008] The organic-inorganic electrolytes include organic polymer solid electrolytes, inorganic solid electrolytes, and lithium salts.

[0009] Preferably, the porous silicon anode active material in the porous silicon anode accounts for 60-90 wt%.

[0010] Preferably, the proportion of organic and inorganic electrolytes in the porous silicon anode active material is 10-40 wt%.

[0011] Preferably, the proportion of carbon nanotubes in the porous silicon framework grown in situ is 0.01 to 1 wt%.

[0012] Preferably, the mass ratio of the porous silicon anode active material, conductive agent, binder and inorganic solid electrolyte in the porous silicon anode is (65-80):(0.1-4):(1-10):(10-30).

[0013] Preferably, the mass ratio of the organic polymer solid electrolyte, the inorganic solid electrolyte, and the lithium salt in the organic-inorganic electrolyte is (30-50):(40-60):(6-16).

[0014] More preferably, the proportion of inorganic solid electrolyte in the organic-inorganic electrolyte is 40-60 wt%.

[0015] More preferably, the mass ratio of the inorganic solid electrolyte to the organic polymer solid electrolyte is 1:(1.01~1.6).

[0016] Preferably, the pore size of the porous silicon framework is 500nm (excluding 500nm) to 2000nm.

[0017] More preferably, the pore size of the porous silicon framework is 600–1000 nm.

[0018] Preferably, the inorganic solid electrolyte includes one or more of lithium phosphorus sulfide chlorine (LPSCl), lithium germanium phosphorus sulfide (LGPS), lithium titanium aluminum phosphate (LATP), and lithium lanthanum zirconium oxide (LLZO).

[0019] Further preferably, the inorganic solid electrolyte in the porous silicon anode is the same as the inorganic solid electrolyte in the organic-inorganic electrolyte.

[0020] Preferably, the conductive agent includes one or more of acetylene black AB, super carbon black SP, Ketjen black KB, vapor-grown carbon fiber VGCF, and carbon nanotubes CNT.

[0021] Preferably, the binder comprises one or more of nitrile rubber (NBR), polyisobutylene (PIB), polysulfide (PTE), and polyvinylidene fluoride (PVDF). Preferably, the organic polymer solid electrolyte comprises one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA).

[0022] Preferably, the lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), and lithium difluorophosphate (LiPO2F2).

[0023] Preferably, the porous silicon framework grown in situ using carbon nanotubes is prepared by heating alloy particles in a carbon-containing gas and then etching them in an acid solution.

[0024] More preferably, the carbon-containing gas includes one or more of methane (CH4), ethylene (C2H4), and acetylene (C2H2).

[0025] More preferably, the heat treatment temperature is 600–1000°C and the time is 10–60 min.

[0026] More preferably, the average particle size of the alloy particles is 1–15 μm.

[0027] More preferably, the average particle size of the alloy particles is 5 to 10 μm.

[0028] More preferably, the alloy particles comprise silicon powder, light metals, and transition metals in an atomic ratio of (30-50):(30-50):(5-30).

[0029] Further preferably, the alloy particles are prepared by ball milling a mixture of silicon powder, light metals and transition metals.

[0030] More preferably, the light metal includes one or both of Mg and Al.

[0031] Preferably, the transition metal includes one or more of Fe, Co, and Ni.

[0032] The second objective of this invention is achieved through the following technical solution:

[0033] A method for preparing a porous silicon anode includes: mixing and ball-milling silicon powder, light metal and transition metal, and then heating the mixture in a carbon-containing gas to obtain alloy composite particles with in-situ carbon nanotube growth; placing the particles in an acid solution to obtain a porous silicon framework; distributing organic and inorganic electrolytes inside and outside the pores of the porous silicon framework to obtain a porous silicon anode active material; and mixing the porous silicon anode active material with a conductive agent, a binder and an inorganic solid electrolyte to obtain a porous silicon anode.

[0034] Preferably, the method for preparing the porous silicon anode includes:

[0035] (1) A mixture of silicon powder, light metal and transition metal with an atomic ratio of (30-50):(30-50):(5-30) is ball-milled to obtain alloy particles with an average particle size of 1-15 μm.

[0036] (2) The alloy particles are heated in a carbon-containing gas to generate carbon nanotubes in situ on the surface of the alloy particles, thus obtaining alloy composite particles with in situ carbon nanotube growth.

[0037] (3) The alloy composite particles grown in situ from carbon nanotubes are placed in an acid solution to obtain a porous silicon framework; the pore size of the porous silicon framework is 500 nm (excluding 500 nm) to 2000 nm.

[0038] (4) Mix 30-50 wt% organic polymer electrolyte, 5-20 wt% lithium salt, and 40-60 wt% inorganic solid electrolyte with a solvent to prepare an organic-inorganic electrolyte slurry;

[0039] (5) Mix the porous silicon framework and the organic-inorganic electrolyte slurry so that the organic-inorganic electrolyte slurry is distributed inside and outside the pores of the porous silicon framework. Dry to remove the solvent to obtain a porous silicon negative electrode active material.

[0040] (6) A porous silicon anode active material is mixed with a conductive agent, a binder and a solid electrolyte to obtain a porous silicon anode.

[0041] Further preferred, step (3) includes: placing 0.1-1 wt% of in-situ grown alloy composite particles of carbon nanotubes in a hydrochloric acid solution with a concentration of 1-5 M, etching for 0.5-6 h to obtain a porous silicon framework with an average pore size of 500-2000 nm.

[0042] More preferably, the solvent in step (4) includes one or more of toluene, tetrahydrofuran, acetonitrile, n-heptane, xylene, and anisole.

[0043] Further preferred, in step (5), the mass ratio of porous silicon skeleton to organic-inorganic electrolyte slurry is (60-90):(40-10).

[0044] The third objective of this invention is achieved through the following technical solution:

[0045] A solid-state battery includes a positive electrode, a porous silicon negative electrode, and a solid electrolyte sheet.

[0046] Preferably, the positive electrode of the solid-state battery includes a positive electrode active material, a conductive agent, a binder, and a solid electrolyte sheet.

[0047] Further preferably, the positive electrode active material includes ternary NCM, lithium cobalt oxide material LiCoO2, and lithium-rich manganese-based material Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Lithium-rich manganese-based material LiNi 0.5 Mn 1.5 One or more of O4.

[0048] Further preferably, the conductive agent includes one or more of acetylene black AB, super carbon black SP, Ketjen black KB, vapor-grown carbon fiber VGCF, and carbon nanotubes CNT. Further preferably, the binder includes one or more of nitrile rubber NBR, polyisobutylene PIB, polysulfide PTE, and polyvinylidene fluoride PVDF.

[0049] Preferably, the solid electrolyte sheet of the solid battery comprises a solid electrolyte and a binder in a mass ratio of (90-99):(1-10).

[0050] Further preferably, the solid electrolyte is an inorganic solid electrolyte, which includes one or more of lithium phosphorus sulfide chlorine sulfide (LPSCl), lithium germanium phosphorus sulfide (LGPS), lithium titanium aluminum phosphate (LATP), and lithium lanthanum zirconium oxide (LLZO).

[0051] More preferably, the adhesive includes one or more of nitrile rubber (NBR), polyisobutylene (PIB), polysulfide (PTE), and polyvinylidene fluoride (PVDF).

[0052] Preferably, the solid-state battery has a Soc 100% negative electrode expansion rate of <65% and a 3C rate of >90%.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. The porous silicon framework of this invention, with its unique large-pore structure, provides ample buffer space for the volume changes caused by lithium-ion insertion and extraction during charging and discharging, effectively alleviating the volume expansion problem of silicon and ensuring material stability from a structural perspective. Furthermore, the carbon nanotubes (CNTs) formed in situ on the surface of the porous silicon framework tightly encapsulate the silicon particles, maintaining the structural integrity of the silicon particles while constructing a continuous and efficient electron conduction network, significantly improving electron transport efficiency and laying a solid foundation for the high-performance operation of the battery.

[0055] 2. In this invention, organic and inorganic electrolytes are uniformly distributed inside and outside the pores of a porous silicon framework, allowing the electrolytes to fully wet the framework structure and thus construct a coherent lithium-ion conduction network. The formation of this network not only ensures that lithium ions can migrate and shuttle quickly and stably during charging and discharging, but also provides a reliable ion transport channel for the stable operation of the battery, effectively improving the overall performance of the battery.

[0056] 3. The solid-state battery of the present invention exhibits excellent comprehensive performance. In terms of cycle performance, the battery capacity can still maintain a high level after multiple charge-discharge cycles, and the decay rate is slow. In terms of rate performance, the battery can respond quickly at high charge-discharge rates and still maintain stable charge-discharge efficiency. Furthermore, the expansion rate of the negative electrode sheet during long-term cycling is significantly suppressed, which greatly reduces the risk of electrode structure damage caused by volume expansion and significantly improves the safety and service life of the battery. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the preparation process of the porous silicon anode active material of the present invention. Detailed Implementation

[0058] The technical solution of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention.

[0059] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0060] In this article, the performance tests of solid-state batteries include:

[0061] 1. Cyclic performance: Charged to 4.2V under constant current and constant voltage at 0.5C, cutoff current 0.05C; rested for 30 minutes; discharged to 2.5V under constant current at 0.5C; cycled 200 times.

[0062] 2. Negative electrode expansion rate: Before and after the cycle performance test, the thickness of the negative electrode was measured with a high-precision caliper.

[0063] 3. 3C rate: Charge to 4.2V under 0.5C constant current and constant voltage, cut-off current 0.05C; rest for 30 minutes; discharge to 2.5V under 3C constant current.

[0064] Example 1

[0065] Methods for preparing porous silicon anodes:

[0066] (1) Silicon powder, light metal Mg and transition metal Co with an atomic ratio of 45:45:10 were mixed and ball-milled for 6 hours to obtain alloy particles with an average particle size of 8 μm.

[0067] (2) The alloy particles were placed in acetylene gas and heated at 800°C for 10 min to generate CNTs in situ on the surface of the alloy particles, thus obtaining alloy composite particles with in situ carbon nanotube growth.

[0068] (3) 10g of in-situ grown carbon nanotube alloy composite particles were placed in 200ml of 2M hydrochloric acid solution for 4h, washed with deionized water and dried to obtain a porous silicon framework; the average pore size of the porous silicon framework was 800nm.

[0069] (4) Mix 1.2g of organic polymer electrolyte PEO, 0.3g of lithium salt LITFSI, 1.5g of inorganic solid electrolyte LPSCL with 10ml of acetonitrile solvent to prepare an organic-inorganic electrolyte slurry;

[0070] (5) Mix the porous silicon framework and the organic-inorganic electrolyte slurry so that the organic-inorganic electrolyte slurry is distributed inside and outside the pores of the porous silicon framework. Dry and remove the solvent to obtain a porous silicon anode active material. The proportion of organic-inorganic electrolyte in the porous silicon anode active material is 30wt%.

[0071] (6) The porous silicon anode active material is mixed with conductive agent SP, binder NBR and solid electrolyte LPSCl in a mass ratio of 71.5:0.5:5:23 to obtain a porous silicon anode.

[0072] Methods for preparing the positive electrode:

[0073] The positive electrode is prepared by mixing ternary NCM, conductive agent VGCF, binder NBR, and solid electrolyte LPSCl in a mass ratio of 70:2:5:23.

[0074] Preparation method of solid electrolyte sheet:

[0075] Solid electrolyte LPSCl and binder NBR were mixed at a mass ratio of 95:5 to prepare solid electrolyte sheets.

[0076] Solid-state battery fabrication methods:

[0077] The positive electrode, solid electrolyte sheet, and porous silicon negative electrode were assembled into a solid-state battery and then tested.

[0078] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0079] Example 2

[0080] Methods for preparing porous silicon anodes:

[0081] (1) A mixture of silicon powder, light metal Mg and transition metal Co with an atomic ratio of 40:40:20 was ball-milled for 6 hours to obtain alloy particles with an average particle size of 8 μm.

[0082] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0083] Methods for preparing the positive electrode:

[0084] The preparation method is the same as that of the positive electrode in Example 1.

[0085] Preparation method of solid electrolyte sheet:

[0086] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0087] Solid-state battery fabrication methods:

[0088] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0089] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0090] Example 3

[0091] Methods for preparing porous silicon anodes:

[0092] (1) Silicon powder, light metal Mg and transition metal Fe with an atomic ratio of 50:30:20 were mixed and ball-milled for 4 hours to obtain alloy particles with an average particle size of 10 μm.

[0093] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0094] Methods for preparing the positive electrode:

[0095] The preparation method is the same as that of the positive electrode in Example 1.

[0096] Preparation method of solid electrolyte sheet:

[0097] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0098] Solid-state battery fabrication methods:

[0099] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0100] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0101] Example 4

[0102] Methods for preparing porous silicon anodes:

[0103] (1) Silicon powder, light metal Mg and transition metal Fe with an atomic ratio of 30:50:20 were mixed and ball-milled for 4 hours to obtain alloy particles with an average particle size of 10 μm.

[0104] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0105] Methods for preparing the positive electrode:

[0106] The preparation method is the same as that of the positive electrode in Example 1.

[0107] Preparation method of solid electrolyte sheet:

[0108] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0109] Solid-state battery fabrication methods:

[0110] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0111] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0112] Example 5

[0113] Methods for preparing porous silicon anodes:

[0114] (1-3) are the same as steps (1-3) in the preparation method of porous silicon anode in Example 1.

[0115] (4) Mix 1.5g organic polymer electrolyte PEO, 0.3g lithium salt LITFSI, 1.2g inorganic solid electrolyte LPSCL with 10ml acetonitrile solvent to prepare organic-inorganic electrolyte slurry;

[0116] (5-6) are the same as steps (5-6) in the preparation method of porous silicon anode in Example 1.

[0117] Methods for preparing the positive electrode:

[0118] The preparation method is the same as that of the positive electrode in Example 1.

[0119] Preparation method of solid electrolyte sheet:

[0120] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0121] Solid-state battery fabrication methods:

[0122] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0123] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0124] Example 6

[0125] Methods for preparing porous silicon anodes:

[0126] (1-3) are the same as steps (1-3) in the preparation method of porous silicon anode in Example 1.

[0127] (4) Mix 1.2g of organic polymer electrolyte PVDF, 0.3g of lithium salt LITFSI, 1.5g of inorganic solid electrolyte LGPS with 10ml of dimethylformamide DMF solvent to prepare an organic-inorganic electrolyte slurry;

[0128] (5-6) are the same as steps (5-6) in the preparation method of porous silicon anode in Example 1.

[0129] Methods for preparing the positive electrode:

[0130] The preparation method is the same as that of the positive electrode in Example 1.

[0131] Preparation method of solid electrolyte sheet:

[0132] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0133] Solid-state battery fabrication methods:

[0134] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0135] The performance of the solid-state battery in this embodiment is shown in Table 1.

[0136] Comparative Example 1

[0137] Methods for preparing silicon anodes:

[0138] A silicon anode was prepared by mixing micron-sized silicon (average particle size 8 μm), conductive agent SP, binder NBR, and solid electrolyte LPSCl in a mass ratio of 71.5:0.5:5:23.

[0139] Methods for preparing the positive electrode:

[0140] The preparation method is the same as that of the positive electrode in Example 1.

[0141] Preparation method of solid electrolyte sheet:

[0142] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0143] Solid-state battery fabrication methods:

[0144] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0145] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0146] Comparative Example 2

[0147] Methods for preparing porous silicon anodes:

[0148] (1) The preparation method of the porous silicon anode in Example 1 is the same as step (1).

[0149] (2-3) are the same as steps (2-3) in the preparation method of porous silicon anode in Example 1.

[0150] (4) Mix 2.7g of organic polymer electrolyte PEO, 0.3g of lithium salt LITFSI with 10ml of acetonitrile solvent to prepare an organic electrolyte slurry;

[0151] (5-6) are the same as steps (5-6) in the preparation method of porous silicon anode in Example 1.

[0152] Methods for preparing the positive electrode:

[0153] The preparation method is the same as that of the positive electrode in Example 1.

[0154] Preparation method of solid electrolyte sheet:

[0155] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0156] Solid-state battery fabrication methods:

[0157] The preparation method is the same as that of the solid-state battery in Example 1. Cyclic testing was performed.

[0158] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0159] Comparative Example 3

[0160] Methods for preparing porous silicon anodes:

[0161] (1) The preparation method of the porous silicon anode in Example 1 is the same as step (1).

[0162] (2-3) are the same as steps (2-3) in the preparation method of porous silicon anode in Example 1.

[0163] (4) Mix 0.3g of lithium salt LITFSI, 2.7g of inorganic solid electrolyte LPSCL with 10ml of acetonitrile solvent to prepare an inorganic electrolyte slurry;

[0164] (5-6) are the same as steps (5-6) in the preparation method of porous silicon anode in Example 1.

[0165] Methods for preparing the positive electrode:

[0166] The preparation method is the same as that of the positive electrode in Example 1.

[0167] Preparation method of solid electrolyte sheet:

[0168] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0169] Solid-state battery fabrication methods:

[0170] The preparation method is the same as that of the solid-state battery in Example 1. Cyclic testing was performed.

[0171] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0172] Comparative Example 4

[0173] Methods for preparing porous silicon anodes:

[0174] (1) The preparation method of the porous silicon anode in Example 1 is the same as step (1).

[0175] (2-3) are the same as steps (2-3) in the preparation method of porous silicon anode in Example 1.

[0176] (4) Mix 3g of inorganic solid electrolyte LPSCL with 10ml of acetonitrile solvent to prepare inorganic electrolyte slurry;

[0177] (5-6) are the same as steps (5-6) in the preparation method of porous silicon anode in Example 1.

[0178] Methods for preparing the positive electrode:

[0179] The preparation method is the same as that of the positive electrode in Example 1.

[0180] Preparation method of solid electrolyte sheet:

[0181] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0182] Solid-state battery fabrication methods:

[0183] The preparation method is the same as that of the solid-state battery in Example 1. Cyclic testing was performed.

[0184] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0185] Comparative Example 5

[0186] Methods for preparing porous silicon anodes:

[0187] (1) A mixture of silicon powder and light metal Mg with an atomic ratio of 45:55 was ball-milled for 6 hours to obtain alloy particles with an average particle size of 8 μm.

[0188] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0189] Methods for preparing the positive electrode:

[0190] The preparation method is the same as that of the positive electrode in Example 1.

[0191] Preparation method of solid electrolyte sheet:

[0192] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0193] Solid-state battery fabrication methods:

[0194] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0195] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0196] Comparative Example 6

[0197] Methods for preparing porous silicon anodes:

[0198] (1) Mix silicon powder and transition metal Co with an atomic ratio of 90:10 and ball mill for 6 hours to obtain alloy particles with an average particle size of 8 μm.

[0199] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0200] Methods for preparing the positive electrode:

[0201] The preparation method is the same as that of the positive electrode in Example 1.

[0202] Preparation method of solid electrolyte sheet:

[0203] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0204] Solid-state battery fabrication methods:

[0205] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0206] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0207] Comparative Example 7

[0208] Methods for preparing porous silicon anodes:

[0209] (1) The preparation method of the porous silicon anode in Example 1 is the same as step (1).

[0210] (2-5) are the same as steps (3-6) in the preparation method of porous silicon anode in Example 1.

[0211] Methods for preparing the positive electrode:

[0212] The preparation method is the same as that of the positive electrode in Example 1.

[0213] Preparation method of solid electrolyte sheet:

[0214] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0215] Solid-state battery fabrication methods:

[0216] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0217] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0218] Comparative Example 8

[0219] Methods for preparing porous silicon anodes:

[0220] (1) The preparation method of the porous silicon anode in Example 1 is the same as step (1).

[0221] (2) The alloy particles were placed in an inert gas Ar and heated at 800°C for 10 min to obtain CNT-free alloy particles.

[0222] (3-6) are the same as steps (3-6) in the preparation method of porous silicon anode in Example 1.

[0223] Methods for preparing the positive electrode:

[0224] The preparation method is the same as that of the positive electrode in Example 1.

[0225] Preparation method of solid electrolyte sheet:

[0226] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0227] Solid-state battery fabrication methods:

[0228] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0229] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0230] Comparative Example 9

[0231] Methods for preparing porous silicon anodes:

[0232] (1) A mixture of silicon powder, light metal Mg and transition metal Co with an atomic ratio of 45:45:10 was ball-milled for 12 hours to obtain alloy particles with an average particle size of 3 μm.

[0233] (2-6) are the same as steps (2-6) in the preparation method of porous silicon anode in Example 1.

[0234] Methods for preparing the positive electrode:

[0235] The preparation method is the same as that of the positive electrode in Example 1.

[0236] Preparation method of solid electrolyte sheet:

[0237] The preparation method is the same as that of the solid electrolyte sheet in Example 1.

[0238] Solid-state battery fabrication methods:

[0239] The preparation method is the same as that of the solid-state battery in Example 1. Testing was then conducted.

[0240] The performance of the solid-state battery in this comparative example is shown in Table 1.

[0241] Table 1. Performance Data of Solid-State Batteries

[0242]

[0243] As shown in Table 1, the solid-state batteries prepared using the porous silicon anode of the present invention in Examples 1 to 6 have good cycle performance and rate performance, and the expansion rate of the anode sheet is significantly reduced.

[0244] In Comparative Example 1, micron-sized silicon was used to directly fabricate the silicon anode. Due to the large expansion of micron-sized silicon, the interface and interparticle contact became unstable, resulting in poor rate performance and cycle performance. In Comparative Example 2, lithium salt and organic polymer electrolytes were used instead of organic-inorganic electrolytes. Due to the low ionic conductivity of organic polymer electrolytes, the conduction rate of lithium ions in the pores was reduced, resulting in a deterioration in rate performance. In Comparative Example 3, lithium salt and inorganic electrolytes were used instead of organic-inorganic electrolytes. Due to the poor flexibility and easy agglomeration of inorganic electrolytes, the conduction rate of lithium ions in the pores and the buffering effect on expansion were reduced, resulting in a deterioration in rate performance and cycle performance. In Comparative Example 4, pure inorganic electrolytes were used instead of organic-inorganic electrolytes, resulting in a deterioration in the expansion rate of the negative electrode. In Comparative Example 5, light metals were used instead of transition metals, resulting in a deterioration in rate performance and cycle performance. In Comparative Example 6, the proportion of metals was reduced, resulting in smaller pores that could not effectively buffer volume expansion. In Comparative Examples 7 and 8, an effective electronic conductive network was not formed on the surface of silicon particles, resulting in poor rate performance. In Comparative Example 9, the particle size of the porous silicon skeleton was reduced, the particle strength was reduced, and it could not effectively form a porous skeleton, making it prone to collapse, resulting in a deterioration in battery performance.

[0245] In summary, the porous silicon framework of this invention, with its unique large-pore structure, provides ample buffer space for the volume changes caused by lithium-ion insertion and extraction during charging and discharging, effectively alleviating the volume expansion problem of silicon and ensuring material stability from a structural perspective. Furthermore, the carbon nanotubes (CNTs) formed in situ on the surface of the porous silicon framework tightly encapsulate the silicon particles, maintaining the structural integrity of the silicon particles while constructing a continuous and efficient electron conduction network, significantly improving electron transport efficiency and enhancing battery performance.

[0246] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0247] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0248] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A porous silicon anode, characterized in that, It includes porous silicon anode active material, inorganic solid electrolyte, conductive agent and binder; The porous silicon anode active material includes a porous silicon framework grown in situ from carbon nanotubes, and organic and inorganic electrolytes distributed inside and outside the pores of the porous silicon framework. The porous silicon framework grown in situ from carbon nanotubes has a pore size > 500 nm. The organic-inorganic electrolytes include organic polymer solid electrolytes, inorganic solid electrolytes, and lithium salts.

2. The porous silicon anode according to claim 1, characterized in that, The porous silicon anode contains 60-90 wt% porous silicon anode active material; the porous silicon anode active material contains 10-40 wt% organic-inorganic electrolyte.

3. The porous silicon anode according to claim 1, characterized in that, The mass ratio of the organic polymer solid electrolyte, the inorganic solid electrolyte, and the lithium salt in the organic-inorganic electrolyte is (30-50):(40-60):(6-16).

4. The porous silicon anode according to claim 3, characterized in that, The inorganic solid electrolyte includes one or more of lithium phosphorus sulfide chlorine sulfide (LPSCl), lithium germanium phosphorus sulfide (LGPS), lithium titanium aluminum phosphate (LATP), and lithium lanthanum zirconium oxide (LLZO). The organic polymer solid electrolyte includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA). The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), and lithium difluorophosphate (LiPO2F2).

5. The porous silicon anode according to claim 1, characterized in that, The porous silicon framework grown in situ using carbon nanotubes is prepared by heating alloy particles in a carbon-containing gas and then etching them in an acid solution.

6. The porous silicon anode according to claim 5, characterized in that, The alloy particles comprise silicon powder, light metals, and transition metals in an atomic ratio of (30-50):(30-50):(5-30).

7. The porous silicon anode according to claim 6, characterized in that, The light metal includes one or both of Mg and Al; the transition metal includes one or more of Fe, Co and Ni.

8. The porous silicon anode according to claim 5, characterized in that, The heat treatment is performed at a temperature of 600–1000°C for a time of 10–60 minutes.

9. A method for preparing a porous silicon anode as described in claim 1, characterized in that, The preparation method includes: mixing and ball-milling silicon powder, light metal and transition metal, and then heating the mixture in a carbon-containing gas to obtain alloy composite particles with in-situ carbon nanotube growth; placing the particles in an acid solution to obtain a porous silicon framework; distributing organic and inorganic electrolytes inside and outside the pores of the porous silicon framework to obtain a porous silicon anode active material; and mixing the porous silicon anode active material with a conductive agent, a binder and an inorganic solid electrolyte to obtain a porous silicon anode.

10. A solid-state battery, characterized in that, It includes a positive electrode, a porous silicon negative electrode, and a solid electrolyte sheet, wherein the porous silicon negative electrode is the porous silicon negative electrode according to any one of claims 1 to 8, or the porous silicon negative electrode prepared by the method of claim 9.

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