Silicon-carbon negative electrode material, preparation method thereof and battery

Abstract

The invention provides a silicon-carbon negative electrode material, a preparation method thereof and a battery. The silicon-carbon negative electrode material comprises: porous carbon; the silicon material is positioned on the surface of the hole wall of the hole structure of the porous carbon; the carbon material covers the surface of the silicon material; the residual space of the pore structure of the porous carbon material is filled with the filler, and the filler comprises a solid electrolyte material. According to the silicon-carbon negative electrode material disclosed by the invention, through synergistic cooperation of the porous carbon, the silicon material, the carbon material, the filler containing the solid electrolyte material and the special structure, on one hand, an expansion space is reserved for working of the silicon active material, the silicon material is stabilized, and on the other hand, an electron transmission channel and an ion transmission channel are also constructed; therefore, the capacity, the first efficiency, the rate and the cycle performance of the silicon-carbon negative electrode material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries and relates to a silicon-carbon negative electrode material, a preparation method thereof, and a battery. Background Art

[0002] As environmental issues become increasingly severe, the development of electric vehicles has seen explosive growth. However, because traditional lithium-ion batteries, which use liquid electrolytes, cannot meet the demands for significantly increased energy density and safety, a new generation of batteries is needed. All-solid-state batteries, due to their use of solid electrolytes with high ionic conductivity, non-flammability, and a wide electrochemical stability window, while also offering increased energy density through a unique bipolar stack, have become one of the most promising battery systems to replace traditional lithium-ion batteries.

[0003] The solid electrolyte in an all-solid-state battery is one of the core components of the battery. Solid electrolytes mainly include four categories: polymers, oxides, sulfides, and halides. The selection of electrode materials determines the energy density, stability, and safety of solid-state batteries. Batteries based on traditional LiCoO2 negative electrodes and graphite negative electrodes have reached the theoretical limit of energy density. The development of high-energy-density all-solid-state batteries urgently requires the use of high-capacity electrode materials. Silicon is the lithium-ion battery negative electrode material with the highest specific capacity (4200mAh / g) discovered by humans so far. Its negative electrode capacity density is ten times higher than that of graphite, making it one of the most promising negative electrode materials. In addition, silicon has abundant natural reserves (the second most abundant element in the earth's crust), is environmentally friendly, and has low electrochemical potential.

[0004] Although silicon negative electrode materials are the preferred materials for high energy density all-solid-state battery negative electrodes due to their high specific capacity, high-capacity silicon negative electrode materials have large volume expansion and are prone to poor interface contact when used in conjunction with solid-state electrolytes, resulting in a rapid increase in cell impedance and the active material losing its electron and ion transmission pathways. The all-solid-state battery's impedance increases rapidly with cycling, ultimately leading to a rapid deterioration in cell performance.

[0005] Therefore, how to effectively suppress the volume expansion of silicon negative electrode materials and construct fast electron and ion pathways is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention aims to provide a silicon-carbon negative electrode material, a preparation method thereof, and a battery. The silicon-carbon negative electrode material of the present invention, through the synergistic combination of porous carbon, silicon material, carbon material, and a filler containing a solid electrolyte material, as well as a special structure, not only reserves expansion space for the silicon active material to work, thus stabilizing the silicon material, but also constructs electron and ion transmission channels, thereby improving the capacity, initial efficiency, rate capability, and cycle performance of the silicon-carbon negative electrode material.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a silicon-carbon negative electrode material, comprising:

[0009] porous carbon;

[0010] Silicon material, the silicon material is located on the pore wall surface of the pore structure of the porous carbon;

[0011] A carbon material, wherein the carbon material covers the surface of the silicon material;

[0012] A filler is filled in the remaining space of the porous carbon material pore structure, and the filler includes a solid electrolyte material.

[0013] It should be noted that the remaining space in the present invention refers to the fillable space after the silicon material and the carbon material are first arranged in the pore structure of the porous carbon, which can be completely filled or partially filled.

[0014] The silicon-carbon negative electrode material of the present invention works synergistically with porous carbon, silicon material, carbon material and filler containing solid electrolyte material and special structure. By depositing silicon material inside the pore structure of porous carbon, expansion space is reserved for the operation of silicon active material. The carbon material covering the surface of silicon material is used to further stabilize the silicon material and provide an electron transmission channel. A fast ion transmission channel is established by filling the remaining space of the pore structure of porous carbon material with solid electrolyte. In addition, the solid electrolyte is also elastic, which can further alleviate the volume effect of silicon material, ensure the ion and electron transmission path of silicon material during operation, thereby improving the capacity, first efficiency, rate and cycle performance of silicon-carbon negative electrode material.

[0015] Furthermore, when the silicon-carbon negative electrode material in the present invention is used in an all-solid-state battery, it also solves the interface contact problem between the solid electrolyte layer and the negative electrode, effectively reduces the battery cell impedance, and improves battery performance.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0017] Preferably, the porous carbon of the present invention comprises any one of artificial graphite, natural graphite, soft carbon or hard carbon, or a combination of at least two thereof.

[0018] Preferably, the median particle size D50 of the porous carbon material is 4μm to 6μm, for example, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm or 6μm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0019] Preferably, the porous carbon has a macroporous structure.

[0020] The present invention uses porous carbon with a macroporous structure as the filling matrix, which can better achieve the orderly distribution of silicon materials, carbon materials and solid electrolyte materials in the pore structure, construct excellent electron and ion transmission channels, improve material dynamics and stability, and thus improve the rate and cycle performance of the material.

[0021] Preferably, the pore size of the macroporous structure is 0.2 μm to 1 μm, for example, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0022] In the present invention, the pore size of the macroporous structure is further adjusted to be 0.2 μm to 1 μm, which is more conducive to the synthesis and preparation of the material and to accommodating the volume expansion of the silicon material.

[0023] Preferably, the volume proportion of the macroporous structure in the porous carbon is 60% to 80%, for example, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78% or 80%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] It should be noted that the present invention does not specifically limit the specific preparation process of porous carbon. Those skilled in the art can purchase it from commercial sources or prepare the desired porous carbon by conventional preparation processes.

[0025] Preferably, the silicon material includes nano-silicon material, and the particle size of the nano-silicon material is 2nm to 4nm, such as 2nm, 3nm or 4nm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the mass proportion of the silicon material in the silicon-carbon negative electrode material is 50% to 70%, for example, 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68% or 70%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0027] Preferably, the mass proportion of the carbon material covering the surface of the silicon material in the silicon-carbon negative electrode material is 1% to 3%, for example, 1%, 1.5%, 2%, 2.5% or 3%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0028] Preferably, the mass proportion of the filler in the silicon-carbon negative electrode material is 5% to 20%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0029] In the present invention, the mass proportion of the silicon material in the silicon-carbon negative electrode material is regulated to be 50% to 70% and / or the mass proportion of the carbon material in the silicon-carbon negative electrode material is 1% to 3% and / or the mass proportion of the filler in the silicon-carbon negative electrode material is 5% to 20%, which can better achieve high negative electrode capacity while having better reaction kinetics.

[0030] Preferably, the filler further includes a conductive agent.

[0031] Furthermore, the present invention adds an additional conductive agent to the filler, which together with the carbon material constructs a dual electron channel, which can better play the role of electron transmission.

[0032] It is understandable that the present invention does not impose any special restrictions on the specific material type of the conductive agent. Conventional conductive materials that can be used in battery systems and can be filled in the corresponding pore structure are applicable to the present invention. For example, the conductive agent includes but is not limited to at least one of carbon nanotubes, carbon black, carbon nanofibers, Ketjen black or graphene.

[0033] Preferably, the solid electrolyte includes a polymer solid electrolyte and / or a sulfide solid electrolyte.

[0034] In the technical solution of the present invention, the polymer solid electrolyte and / or sulfide solid electrolyte not only provides an ion transmission channel, but also has a certain elasticity, which can better alleviate the volume effect of silicon material expansion, thereby improving the structural stability and battery cell cycle performance.

[0035] Preferably, the median particle size D50 of the sulfide solid electrolyte is 30 nm to 100 nm, for example, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In the present invention, the median particle size D50 of the sulfide solid electrolyte is regulated to be 30 nm to 100 nm, which is more conducive to pore filling and the construction of ion transmission pathways.

[0037] In a second aspect, the present invention provides a method for preparing the silicon-carbon negative electrode material as described in the first aspect, the preparation method comprising the following steps:

[0038] (1) depositing silicon material on the pore walls of the porous carbon structure by chemical vapor deposition;

[0039] (2) depositing a carbon material on the surface of a silicon material by chemical vapor deposition to form an intermediate;

[0040] (3) Filling a filler containing a solid electrolyte into the remaining space of the porous carbon structure of the intermediate in step (2) to form the silicon-carbon negative electrode material.

[0041] In the preparation method of the present invention, in-situ deposition of silicon in the pore structure of porous carbon is achieved by chemical vapor deposition, the deposition effect is excellent, and the particle size of the silicon material is controllable; further, chemical vapor deposition is used to achieve coverage of the surface of the silicon material with carbon material, that is, the carbon material is also located inside the pore structure, rather than directly coated on the surface of the porous carbon material, and finally the filler is filled, thereby obtaining a silicon-carbon negative electrode material with structural stability and excellent performance, without the need for additional operating steps.

[0042] Preferably, the temperature of the chemical vapor deposition in step (1) is 400-500°C, for example, 400°C, 425°C, 450°C, 475°C or 500°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0043] Preferably, the chemical vapor deposition in step (1) is carried out in a fluidized bed.

[0044] Preferably, the temperature of the chemical vapor deposition in step (2) is 400°C to 600°C, for example, 400°C, 450°C, 500°C, 550°C or 600°C, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0045] It should be noted that the specific deposition process of the silicon material and the specific deposition process of the carbon material in the present invention can be adaptively selected and adjusted according to the required product characteristics.

[0046] Optionally, in step (1), the deposition raw material of the silicon material is silane gas.

[0047] Optionally, in step (2), the deposition raw material of the carbon material includes any one or a combination of at least two of gaseous carbon sources such as methane, ethylene or acetylene.

[0048] Preferably, the filling method in step (3) comprises a spray drying method, and the spray drying method comprises:

[0049] The intermediate and filler solutions were mixed and spray dried.

[0050] In the present invention, the spray drying method is used, which is more conducive to filling the filler into the pore structure of the porous carbon.

[0051] Preferably, the filler solution includes polymer solid electrolyte raw materials and / or sulfide solid electrolyte in addition to the solvent.

[0052] Preferably, the raw materials of the polymer solid electrolyte include polymer and lithium salt.

[0053] It can be understood that the polymer solid electrolyte and sulfide solid electrolyte described in the present invention are both conventional technical solutions in the field, and the present invention is applicable to conventional substances that can be obtained within a reasonable range by those skilled in the art.

[0054] Optionally, the polymer includes but is not limited to at least one of polyethylene oxide, polysiloxane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer or poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) copolymer.

[0055] Optionally, the lithium salt includes but is not limited to at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, or lithium trifluoromethanesulfonate.

[0056] Alternatively, the chemical formula of the sulfide solid electrolyte can be Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li6PS5I, Li6PS5ClBr, Li 10 SnP2S 12、Li7GePS8、70Li2S-30P2S5、Li2S-SiS2、80Li2S-20P2S5 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 At least one of the above.

[0057] Preferably, the number average molecular weight of the polymer is 800,000 to 1.5 million, for example, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000 or 1,500,000, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the polymer is 0% to 80%, for example, 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80%, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0059] Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the lithium salt is 0% to 10%, for example, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0060] Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the sulfide solid electrolyte in the filler is 0-100%, for example, 0%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0061] In the present invention, the filler solution can be a pure polymer solid electrolyte solution, a pure sulfide solid electrolyte solution, or a mixed solution of a polymer solid electrolyte and a sulfide solid electrolyte; further preferred is a combination of a polymer solid electrolyte and a sulfide solid electrolyte, which can better balance the improvement of ionic conductivity and elasticity.

[0062] Preferably, the solid electrolyte solution further includes a conductive agent.

[0063] Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the conductive agent in the filler is 0% to 5%, for example, 1%, 2%, 3%, 4% or 5%, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0064] For the present invention, regulating the mass proportion of the conductive agent in the filler to 0% to 5%, especially when the mass proportion of the conductive agent in the filler is 1% to 5%, can not only ensure the normal functioning of the ion transmission channel, but also provide additional electron transmission pathways to improve the electrode reaction kinetics.

[0065] Optionally, the solvent in the filler solution includes but is not limited to any one of acetonitrile, tetrahydrofuran, anisole, chloroform, dichloroethane or dimethylformamide, or a combination of at least two thereof.

[0066] Optionally, the spray drying temperature is 80°C to 150°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C.

[0067] In a third aspect, the present invention further provides an electrochemical device, comprising the silicon-carbon negative electrode material as described in the first aspect or the silicon-carbon negative electrode material prepared by the preparation method as described in the second aspect.

[0068] Preferably, the electrochemical device comprises a liquid lithium ion battery or a solid lithium ion battery, preferably a solid lithium ion battery.

[0069] It should be noted that the silicon-carbon negative electrode material in the present invention can be used in both liquid lithium-ion batteries and solid-state lithium-ion batteries, and is preferably used in solid-state lithium-ion batteries. While suppressing the volume expansion of silicon, it also has the technical effect of improving the interface contact between the solid electrolyte layer and the negative electrode and reducing the battery impedance.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] The silicon-carbon negative electrode material of the present invention works synergistically with porous carbon, silicon material, carbon material and filler containing solid electrolyte material and special structure. By depositing silicon material inside the pore structure of porous carbon, expansion space is reserved for the operation of silicon active material. The carbon material covering the surface of silicon material is used to further stabilize the silicon material and provide an electron transmission channel. A fast ion transmission channel is established by filling the remaining space of the pore structure of porous carbon material with solid electrolyte. In addition, the solid electrolyte is also elastic, which can further alleviate the volume effect of silicon material, ensure the ion and electron transmission path of silicon material during operation, thereby improving the capacity, first efficiency, rate and cycle performance of silicon-carbon negative electrode material. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0074] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0075] Example 1

[0076] This embodiment provides a silicon-carbon negative electrode material, which includes:

[0077] Porous carbon has a macroporous structure with a pore size of 0.5 μm, and the volume of macropores in the porous carbon material accounts for 70%;

[0078] Silicon material, the silicon material is located on the pore wall surface of the pore structure of the porous carbon, and the particle size of the silicon material is 2 to 3 nm;

[0079] A carbon material, wherein the carbon material covers the surface of the silicon material;

[0080] A filler, which fills the remaining space in the pore structure of the porous carbon material, and the filler includes a solid electrolyte material;

[0081] The mass ratio of porous carbon:silicon:carbon material:filler is 20:60:2:18.

[0082] The preparation method of the silicon-carbon negative electrode material is as follows:

[0083] (1) Synthesis of silicon-carbon materials: A porous hard carbon material with a median particle size of 4 μm and silane gas are introduced into a fluidized bed furnace and subjected to a heat treatment at 420°C by chemical vapor deposition, thereby depositing the silicon material on the pore walls of the porous carbon. A carbon layer is then formed on the surface of the silicon material by chemical vapor deposition at a deposition temperature of 500°C using methane as a carbon source gas, thereby forming an intermediate.

[0084] (2) Preparation of solid electrolyte slurry: Dissolve polyethylene oxide with a number average molecular weight of 1 million in acetonitrile, and then add lithium bis(fluorosulfonyl)imide, carbon nanotubes, and sulfide solid electrolyte Li6PS5Cl with a median particle size D50 of 50 nm in sequence to form a filler solution. The mass ratio of the polymer: lithium salt: conductive agent: sulfide is 70:5:2:23;

[0085] (3) Solid electrolyte filling: The first step intermediate is evenly dispersed in the filler solution, spray-dried, and the silicon-carbon negative electrode material is obtained.

[0086] Example 2

[0087] This embodiment provides a silicon-carbon negative electrode material, which includes:

[0088] Porous carbon has a macroporous structure with a pore size of 1 μm, and the volume of macropores in the porous carbon material accounts for 80%;

[0089] Silicon material, the silicon material is located on the pore wall surface of the pore structure of the porous carbon, and the particle size of the silicon material is 2 to 4 nm;

[0090] A carbon material, wherein the carbon material covers the surface of the silicon material;

[0091] A filler, which fills the remaining space in the pore structure of the porous carbon material, and the filler includes a solid electrolyte material;

[0092] The mass ratio of porous carbon:silicon:carbon material:filler is 12:80:3:5.

[0093] The preparation method of the silicon-carbon negative electrode material is as follows:

[0094] (1) Synthesis of silicon-carbon materials: A porous hard carbon material with a median particle size of 6 μm and silane gas are introduced into a fluidized bed furnace and subjected to a heat treatment at 500°C by chemical vapor deposition, thereby depositing the silicon material on the pore walls of the porous carbon structure. A carbon layer is then formed on the surface of the silicon material by chemical vapor deposition at a deposition temperature of 400°C using methane as a carbon source gas, thereby forming an intermediate;

[0095] (2) Preparation of solid electrolyte slurry: Dissolve polyethylene oxide with a number average molecular weight of 1.5 million in acetonitrile, then sequentially add bis(fluorosulfonyl)imide lithium salt, carbon nanotubes, and sulfide solid electrolyte Li6PS5Cl with a median particle size D50 of 100 nm to form a filler solution. The mass ratio of the polymer: lithium salt: conductive agent: sulfide is 80:10:1:10.

[0096] (3) Solid electrolyte filling: The first step intermediate is evenly dispersed in the filler solution, spray-dried, and the silicon-carbon negative electrode material is obtained.

[0097] Example 3

[0098] This embodiment provides a silicon-carbon negative electrode material, which includes:

[0099] Porous carbon has a macroporous structure with a pore size of 0.2 μm, and the volume of macropores in the porous carbon material accounts for 60%;

[0100] Silicon material, the silicon material is located on the pore wall surface of the pore structure of the porous carbon, and the particle size of the silicon material is 2 to 3 nm;

[0101] A carbon material, wherein the carbon material covers the surface of the silicon material;

[0102] A filler, which fills the remaining space in the pore structure of the porous carbon material, and the filler includes a solid electrolyte material;

[0103] The mass ratio of porous carbon:silicon:carbon material:filler is 33:50:2:15.

[0104] The preparation method of the silicon-carbon negative electrode material is as follows:

[0105] (1) Synthesis of silicon-carbon materials: A porous hard carbon material with a median particle size of 5 μm and silane gas are introduced into a fluidized bed furnace and subjected to a heat treatment at 420°C by chemical vapor deposition, thereby depositing the silicon material on the pore walls of the porous carbon. A carbon layer is then formed on the surface of the silicon material by chemical vapor deposition at a deposition temperature of 600°C using methane as a carbon source gas, thereby forming an intermediate.

[0106] (2) Preparation of solid electrolyte slurry: Dissolve polyethylene oxide with a number average molecular weight of 800,000 in acetonitrile and then add lithium bis(fluorosulfonyl)imide salt, carbon nanotubes, and sulfide solid electrolyte Li6PS5Cl with a median particle size D50 of 30 nm to form a filler solution. The mass ratio of the polymer: lithium salt: conductive agent: sulfide is 50:1:5:44.

[0107] (3) Solid electrolyte filling: The first step intermediate is evenly dispersed in the filler solution, spray-dried, and the silicon-carbon negative electrode material is obtained.

[0108] Example 4

[0109] The difference between this embodiment and embodiment 1 is that the polymer in this embodiment is polysiloxane.

[0110] The other conditions are the same as those in Example 1.

[0111] Example 5

[0112] The difference between this embodiment and embodiment 1 is that the filler in this embodiment does not contain sulfide solid electrolyte, and the mass ratio of the polymer:lithium salt:conductive agent is 88:10:2.

[0113] The other conditions are the same as those in Example 1.

[0114] Example 6

[0115] The difference between this embodiment and embodiment 1 is that the filler in this embodiment does not contain a polymer solid electrolyte, that is, the mass ratio of the conductive agent to the sulfide is 2:98.

[0116] The other conditions are the same as those in Example 1.

[0117] Example 7

[0118] The difference between this embodiment and embodiment 1 is that the pore diameter of the macroporous structure in this embodiment is 150 nm.

[0119] The other conditions are the same as those in Example 1.

[0120] Example 8

[0121] The difference between this embodiment and embodiment 1 is that the pore size of the macroporous structure in this embodiment is 1.1 μm.

[0122] The other conditions are the same as those in Example 1.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 1 is that the filler in this embodiment does not contain a conductive agent.

[0125] The mass ratio of the polymer: lithium salt: conductive agent: sulfide is 70:5:25.

[0126] The other conditions are the same as those in Example 1.

[0127] Example 10

[0128] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the conductive agent accounts for 10% of the total mass of the non-solvent filler, and the remaining raw materials are reduced proportionally.

[0129] The other conditions are the same as those in Example 1.

[0130] Example 11

[0131] The difference between this embodiment and embodiment 1 is that the solid electrolyte in the filler of this embodiment is lithium lanthanum zirconium oxide solid electrolyte Li7La3Zr2O 12 (LLZO), that is, in step (2), lithium lanthanum zirconium oxide solid electrolyte is used to replace the polymer solid electrolyte and the sulfide solid electrolyte.

[0132] The other conditions are the same as those in Example 1.

[0133] Example 12

[0134] The difference between this embodiment and embodiment 1 is that in the silicon-carbon negative electrode material of this embodiment, the mass proportion of the filler is 1%, and the remaining materials are adaptively increased in proportion.

[0135] In the preparation method, the amount of filler added can be adjusted adaptively.

[0136] The other conditions are the same as those in Example 1.

[0137] Example 13

[0138] The difference between this embodiment and embodiment 1 is that in the silicon-carbon negative electrode material of this embodiment, the mass proportion of the filler is 25%, and the remaining materials are reduced proportionally.

[0139] In the preparation method, the amount of filler added can be adjusted adaptively.

[0140] The other conditions are the same as those in Example 1.

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 1 is that the silicon-carbon negative electrode material of this comparative example does not contain filler.

[0143] In the preparation method, step (2) and step (3) are not performed.

[0144] The other conditions are the same as those in Example 1.

[0145] Comparative Example 2

[0146] The difference between this comparative example and Example 1 is that the silicon-carbon negative electrode material of this comparative example does not contain carbon material covering the surface of the silicon material.

[0147] In step (1) of the preparation method, after the silicon material is deposited, no subsequent methane deposition process is performed.

[0148] The rest of the preparation methods and parameters were the same as those in Example 1.

[0149] Comparative Example 3

[0150] This comparative example provides a method for preparing a silicon-carbon negative electrode material. The method for preparing the silicon-carbon negative electrode material is as follows:

[0151] The porous hard carbon (porous hard carbon particle size is 4 μm, with nanopores, the volume of a single nanopore is 30 nm) 3 ) is first heat-treated with silane gas at 420°C in a fluidized bed furnace to form a base material, and then a carbon layer is formed on the surface of the base material by chemical vapor deposition using methane as a carbon source gas at a deposition temperature of 500°C to form a final silicon-carbon material. The average particle size of the nano-silicon is 2nm, and the mass percentage of silicon in the base material is 50%.

[0152] [Battery preparation and performance testing]

[0153] I. Battery Preparation

[0154] The Li6PS5Cl with a median particle size of 3 microns was placed in the mold battery and a 1mm electrolyte original sheet was processed under a pressure of 30MPa. 0.8 Co 0.1 Mn 0.1 O2) was mixed evenly with a Li6PS5Cl material with a median particle size of 1 micron in a mass ratio of 9:1 and placed on one side of the electrolyte sheet for pressing. The silicon negative electrode material provided in the embodiment and the comparative example and Li6PS5Cl were mixed evenly in a mass ratio of 9:1 and placed on the other side of the electrolyte sheet relative to the positive electrode side. After pressing, a solid-state battery was obtained.

[0155] II Performance Test

[0156] ① Capacity and first effect: 25℃, voltage range 2.5-4.2V, charge and discharge at a rate of 0.1C. The 0.1C discharge specific capacity is the material specific capacity, and the first discharge capacity divided by the first charge capacity is the first effect.

[0157] ② Rate: 25℃, voltage range 2.5-4.2V, charge at 0.1C, discharge at 0.1C and 1C respectively, the 1C discharge capacity divided by the 0.1C discharge capacity is the rate retention rate.

[0158] ③ Cycle life: At 25℃, voltage range 2.5-4.2V, charge and discharge at 1C until the capacity decays to 80%, that is the cycle life.

[0159] The test results of the above tests are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] From Table 1, we can get:

[0164] The silicon-carbon negative electrode material provided by the present invention greatly improves the capacity, first efficiency, rate and cycle performance of the silicon-carbon negative electrode material through the synergistic combination of porous carbon, silicon material, carbon material and filler containing solid electrolyte material and special structure; and no significant performance improvement can be achieved if neither the material nor the structure meets the above conditions.

[0165] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A silicon-carbon negative electrode material, characterized in that: The silicon-carbon negative electrode material comprises: porous carbon; Silicon material, the silicon material is located on the pore wall surface of the pore structure of the porous carbon; A carbon material, wherein the carbon material covers the surface of the silicon material; A filler is filled in the remaining space of the porous carbon material pore structure, and the filler includes a solid electrolyte material.

2. The silicon-carbon negative electrode material according to claim 1, characterized in that The median particle size D50 of the porous carbon material is 4 μm to 6 μm; Preferably, the porous carbon has a macroporous structure; Preferably, the pore size of the macroporous structure is 0.2 μm to 1 μm; Preferably, the volume proportion of the macroporous structure in the porous carbon is 60% to 80%; Preferably, the silicon material includes nano-silicon material, and the particle size of the nano-silicon material is 2nm to 4nm.

3. The silicon-carbon negative electrode material according to claim 1, characterized in that The mass proportion of the silicon material in the silicon-carbon negative electrode material is 50% to 70%; Preferably, the carbon material covering the surface of the silicon material accounts for 1% to 3% by mass of the silicon-carbon negative electrode material; Preferably, the filler accounts for 5% to 20% by mass of the silicon-carbon negative electrode material.

4. The silicon-carbon negative electrode material according to claim 1, characterized in that The filler also includes a conductive agent; Preferably, the solid electrolyte comprises a polymer solid electrolyte and / or a sulfide solid electrolyte; Preferably, the median particle size D50 of the sulfide solid electrolyte is 30 to 100 nm.

5. A method for preparing the silicon-carbon negative electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) depositing silicon material on the pore walls of the porous carbon structure by chemical vapor deposition; (2) depositing a carbon material on the surface of a silicon material by chemical vapor deposition to form an intermediate; (3) Filling a filler containing a solid electrolyte into the remaining space of the porous carbon structure of the intermediate in step (2) to form the silicon-carbon negative electrode material.

6. The preparation method according to claim 5, characterized in that The temperature of the chemical vapor deposition in step (1) is 400-500° C. Preferably, the chemical vapor deposition in step (1) is carried out in a fluidized bed.

7. The preparation method according to claim 5, characterized in that The temperature of the chemical vapor deposition in step (2) is 400°C to 600°C.

8. The preparation method according to claim 5, characterized in that The filling method in step (3) includes a spray drying method, and the spray drying method includes: The intermediate and filler solutions were mixed and spray dried.

9. The preparation method according to claim 8, characterized in that The filler solution includes, in addition to the solvent, a polymer solid electrolyte raw material and / or a sulfide solid electrolyte; Preferably, the raw materials of the polymer solid electrolyte include polymer and lithium salt; Preferably, the number average molecular weight of the polymer is 800,000 to 1.5 million; Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass of the polymer accounts for 0% to 80%; Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass of the lithium salt accounts for 0% to 10%; Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the sulfide solid electrolyte in the filler is 0 to 100%; Preferably, the solid electrolyte solution further includes a conductive agent; Preferably, based on the mass of the non-solvent in the filler solution being 100%, the mass proportion of the conductive agent in the filler is 0% to 5%, preferably 1% to 5%.

10. An electrochemical device, characterized in that The electrochemical device comprises the silicon-carbon negative electrode material according to any one of claims 1 to 4 or the silicon-carbon negative electrode material prepared by the preparation method according to any one of claims 5 to 9; Preferably, the electrochemical device comprises a liquid lithium ion battery or a solid lithium ion battery, preferably a solid lithium ion battery.

Images