Silicon-based negative electrode material and preparation method and application thereof

Abstract

The application provides a silicon-based negative electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a silica sol and a nanocarbon sol to obtain a mixed sol, and performing a reduction reaction to obtain the silicon-based negative electrode material. The preparation method provided by the application not only solves the problem of difficult dispersion of a conductive agent, but also inhibits the volume expansion of the silicon-based negative electrode material in the charging and discharging process, and improves the capacity of the battery. In addition, the silicon-based negative electrode material is coated with a sulfide solid electrolyte, which can provide more lithium ion transmission channels, reduce the impedance and polarization degree of the material, and thus improve the electrochemical performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode technology, specifically relating to a silicon-based anode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in 3C digital products, automobiles, and energy storage due to their advantages such as high energy density, wide operating temperature range, and environmental friendliness. Currently, commercially available lithium-ion batteries generally use organic liquid electrolytes and gel electrolytes, which are volatile, flammable, and explosive, posing serious safety hazards to the battery system. Solid-state lithium-ion batteries, using solid electrolytes, offer unparalleled safety compared to liquid lithium-ion batteries and hold the promise of completely eliminating safety hazards during use, better meeting the future development needs of electric vehicles and large-scale energy storage. Currently, the most widely researched solid electrolytes are polymer electrolytes, oxide electrolytes, and sulfide electrolytes. Among them, sulfide solid electrolyte materials are the most promising materials for achieving high-performance all-solid-state batteries.

[0003] Commercially available lithium-ion battery anode materials are primarily graphite. While graphite possesses advantages such as low electrode potential, high cycle efficiency, and long cycle life, its theoretical specific capacity is only 372 mAh / g, limiting further capacity improvements. Furthermore, its lithium intercalation mechanism is typically cross-sectional, making it unsuitable for rapid charge-discharge cycles, thus restricting its application in high-power applications. Silicon materials have a specific capacity 10 times that of commercially available graphite anodes. The commercialization of silicon anodes can effectively increase the capacity of individual battery cells and has become a current research hotspot. However, the significant volume change and low conductivity of silicon-based anodes during charge-discharge processes limit their applications. Currently, efforts are mainly made to mitigate the volume expansion of silicon materials through alloying with metals, nano-sizing of silicon, or compositing silicon with active or inactive materials. Conductive agents are added to improve the conductivity of silicon-based anodes, but dispersing these agents is particularly challenging.

[0004] For example, CN108598430B discloses a method for preparing silicon-carbon anode materials and porous silicon-carbon microsphere anode materials. The preparation method includes: grinding silicon powder slurry to obtain ground silicon powder slurry; graphitizing carbon micropowder to obtain graphitized carbon micropowder; stirring the ground silicon powder slurry, continuously adding graphitized carbon micropowder to the ground silicon powder slurry during stirring, adding a coated carbon source, and performing ultrasonic treatment while stirring simultaneously, followed by spray drying to obtain silicon-carbon microspheres; carbonizing the silicon-carbon microspheres to obtain silicon-carbon carbide microspheres; etching the silicon-carbon carbide microspheres, and then washing and drying the silicon-carbon carbide microspheres to obtain porous silicon-carbon microsphere anode materials.

[0005] CN104681797B discloses a silicon-carbon composite anode, comprising a silicon source and a carbon source. The silicon source is elemental silicon with a particle size distribution of 100 nm-80 μm, and the silicon source accounts for 10%-80% of the total mass of the silicon-carbon composite anode. The carbon source includes a carbon anode material and a conductive agent. The carbon anode material is one or more of carbon fiber, graphite, and mesophase carbon microspheres, and the carbon anode material accounts for 10%-90% of the total mass of the carbon source.

[0006] CN107507972B discloses a method for preparing a silicon-carbon anode material, the silicon-carbon anode material, and a lithium-ion battery. The preparation method includes the following steps: using silicon alloy powder as raw material, acid washing is performed to remove metals other than silicon from the silicon alloy powder to obtain porous silicon; the porous silicon is placed in a carbon precursor and carbon-coated to form a silicon-carbon composite material with a carbon coating layer; the silicon-carbon composite material is carbonized to obtain the silicon-carbon anode material.

[0007] Therefore, providing a method for preparing silicon-based anode materials can not only solve the problem of difficult dispersion of conductive agents, but also suppress the volume expansion of the prepared silicon-based anode materials during charging and discharging, which is an urgent technical problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a silicon-based anode material, its preparation method, and its applications. The present invention utilizes an in-situ gelation method to prepare a porous silicon-based anode material with high conductivity. This preparation method not only solves the problem of difficult dispersion of conductive agents but also suppresses the volume expansion of the silicon-based anode material during charge and discharge, thereby improving battery capacity. Furthermore, coating the silicon-based anode material with a sulfide solid electrolyte provides more lithium-ion transport channels, reduces the material's impedance and polarization, and thus improves the battery's electrochemical performance.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a silicon-based anode material, the method comprising the following steps:

[0011] A mixed sol is obtained by mixing silica sol and nano carbon sol, and a reduction reaction is carried out to obtain the silicon-based anode material.

[0012] This invention employs an in-situ gelation method, directly mixing and reducing nano-carbon sol with silica sol to obtain a porous silicon-based anode material with high conductivity. This preparation method allows for the uniform distribution of nano-carbon around silicon particles, solving the problem of difficult conductive agent dispersion and suppressing the volume expansion of the silicon-based anode material during charge and discharge, thereby increasing battery capacity. This preparation method is simple, environmentally friendly, and easily scalable.

[0013] It is important to note that, compared to conventional carbon materials, nano-carbon sol not only exhibits better dispersion properties of carbon nanomaterials but also possesses a significantly larger specific surface area and superior electrical conductivity. If the nano-carbon sol is replaced with conventional carbon materials, such as carbon nanotubes, carbon nanofibers, or conductive carbon black, severe agglomeration of the conductive agent and difficulties in dispersion will occur.

[0014] In this invention, the silica sol is a dispersion of nano-sized silica particles in water or a solvent, also known as silica sol.

[0015] As a preferred embodiment of the present invention, the method for preparing the silica sol includes:

[0016] The silicon source, catalyst, and solvent are mixed and reacted to obtain the silica sol.

[0017] Preferably, the silicon source comprises tetraethyl orthosilicate.

[0018] Preferably, the catalyst comprises an alkaline catalyst, which includes ammonia.

[0019] Preferably, the solvent includes ethanol.

[0020] Preferably, the volume ratio of the silicon source to the solvent is 1:(2-6), for example, it can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, etc.

[0021] Preferably, the volume ratio of the catalyst to the solvent is 1:(8-16), for example, it can be 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 or 1:16, etc.

[0022] Preferably, the volume ratio of the silicon source to the catalyst is (3-5):1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, etc.

[0023] In this invention, whether the volume ratio of silicon source to catalyst is too large or too small, it will affect the formation of silica sol and lead to a decrease in the electrochemical performance of the material.

[0024] Preferably, the reaction time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0025] Preferably, in the preparation process of the silica sol, the specific steps of mixing include:

[0026] (1) Mix the silicon source and a portion of the solvent to obtain solution A;

[0027] The catalyst and another portion of the solvent were mixed to obtain solution B;

[0028] (2) Mix the solution A and the solution B from step (1) to obtain the mixed sol.

[0029] In this invention, the order of preparing solution A and solution B in step (1) is not limited. Solution A can be prepared first, followed by solution B; solution B can be prepared first, followed by solution A; or solution A and solution B can be prepared simultaneously.

[0030] Preferably, solution A and solution B are allowed to stand separately before mixing, and the standing time is independently 10-20 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes.

[0031] In this invention, "independently" means that the settling time of solution A can be selected as 10-20 minutes, and the settling time of solution B can be selected as 10-20 minutes. The settling time of the two solutions does not interfere with each other. They can be the same or different.

[0032] Preferably, the volume ratio of silicon source to nano-carbon sol in the silica sol is 1:(1-2), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0033] In this invention, if the volume ratio of silicon source to nano-carbon sol in silica sol is too small, that is, the amount of nano-carbon sol used is too large, the capacity of the prepared anode material will be small; if the volume ratio of silica sol to nano-carbon sol is too large, that is, the amount of nano-carbon sol used is too small, the conductivity of the prepared anode material will be low.

[0034] Preferably, the silica sol and nano-carbon sol are mixed and then dried.

[0035] Preferably, the drying method includes atmospheric pressure drying or vacuum drying.

[0036] Preferably, the drying temperature is 80-120℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃, etc.

[0037] Preferably, the drying time is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0038] As a preferred technical solution, the reduction reaction process includes:

[0039] The mixed sol is mixed with a reducing agent to carry out a reduction reaction and obtain the silicon-based anode material.

[0040] Preferably, the reducing agent comprises magnesium powder.

[0041] Preferably, the mass ratio of the mixed sol to the reducing agent is 1:(0.1-0.2), for example, it can be 1:0.1, 1:0.12, 1:0.14, 1:0.16, 1:0.18 or 1:0.2, etc.

[0042] Preferably, the reduction reaction is carried out in an inert atmosphere, wherein the gas in the inert atmosphere includes nitrogen and / or argon.

[0043] Preferably, the temperature of the reduction reaction is 600-800℃, for example, it can be 600℃, 650℃, 700℃, 750℃ or 800℃.

[0044] Preferably, the reduction reaction takes 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0045] Secondly, the present invention provides a silicon-based anode material prepared by the preparation method described in the first aspect, wherein the silicon-based anode material is a porous silicon-based anode material.

[0046] In this invention, a porous silicon-based anode material can be obtained by reducing the mixed sol. The porous structure can suppress the volume expansion of the silicon-based anode material during the charging and discharging process.

[0047] Thirdly, the present invention provides a silicon-based anode material having a sulfide solid electrolyte coating layer, wherein the silicon-based anode material having a sulfide solid electrolyte coating layer is obtained by ball milling the silicon-based anode material described in the second aspect with a sulfide solid electrolyte.

[0048] This invention employs a ball milling mixing method to coat silicon-based anode materials with sulfide solid electrolytes. Sulfide solid electrolytes can provide more lithium-ion channels, reduce impedance and polarization during charging and discharging, and improve the electrochemical performance of the battery.

[0049] Preferably, the silicon-based anode material with a sulfide solid electrolyte coating layer includes a silicon-based anode material core and a sulfide solid electrolyte coating layer located on the surface of the silicon-based anode material core.

[0050] Preferably, the chemical formula of the sulfide solid electrolyte is Li. 6-x PS 5-x M 1+x 0 ≤ x ≤ 0.6, where x can be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6, etc. M includes any one or at least a combination of two of Cl, Br, or I, preferably Li. 5.4 PS 4.4 Cl 1.6 .

[0051] Preferably, the mass ratio of the silicon-based anode material to the sulfide solid electrolyte is (5-9):(1-4), wherein the silicon-based anode material is selected from a range of 5-9, for example, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5 or 9, and the sulfide solid electrolyte is selected from a range of 1-4, for example, 1, 1.5, 2, 2.5, 3, 3.5 or 4.

[0052] In this invention, if the mass ratio of silicon-based anode material to sulfide solid electrolyte is too small, that is, if the amount of sulfide solid electrolyte is too large, the capacity that the electrode can achieve is low; if the mass ratio of silicon-based anode material to sulfide solid electrolyte is too large, that is, if the amount of sulfide solid electrolyte is too small, there are fewer lithium-ion channels, the impedance during charging and discharging increases, which is not conducive to battery cycling.

[0053] Fourthly, the present invention provides a method for preparing a silicon-based anode material having a sulfide solid electrolyte coating layer as described in the third aspect, the method comprising:

[0054] A silicon-based anode material is prepared using the preparation method described in the first aspect. The silicon-based anode material is ball-milled and mixed with the sulfide solid electrolyte, and then dried to obtain the composite silicon-based anode material with a sulfide solid electrolyte coating layer.

[0055] Preferably, the atmosphere in which the silicon-based anode material is mixed with the sulfide solid electrolyte is an inert atmosphere, and the gas in the inert atmosphere includes nitrogen and / or argon.

[0056] Preferably, the silicon-based anode material is ground before being ball-milled and mixed with the sulfide solid electrolyte.

[0057] Direct ball milling leads to extremely uneven distribution and causes unmixed components to adhere to the balls and the surface of the milling jar, resulting in loss and affecting the material ratio. Therefore, this invention uses grinding to premix the materials, which can make the distribution of each component more uniform.

[0058] Preferably, the ball milling mixing method includes wet ball milling, followed by a drying step.

[0059] In this invention, wet ball milling improves the contact and dispersion properties between the sulfide solid electrolyte and the silicon-based anode material, allowing the sulfide solid electrolyte to uniformly coat the silicon-based anode material. Furthermore, wet ball milling addresses the issues of severe pulverization and poor processing performance of the silicon-based anode material, enabling direct pressing without the need for binders, which is beneficial for achieving high specific capacity and cycle performance in the battery.

[0060] Preferably, the ball milling jar used in the wet ball milling is sealed to effectively prevent the sulfide solid electrolyte from coming into contact with air, thus avoiding deterioration or decomposition of the sulfide solid electrolyte.

[0061] Preferably, the solvent used in the wet ball milling includes any one or a combination of at least two of cyclohexane, anisole, isobutyl isobutyrate, or dichloromethane, with cyclohexane being the most preferred.

[0062] Preferably, the ball milling speed is 100-200 rpm, for example, it can be 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm.

[0063] In this invention, if the ball milling speed is too low, uniform coating of sulfide solid electrolyte cannot be achieved; if the ball milling speed is too high, the structure of the negative electrode material will be damaged.

[0064] Preferably, the ball milling mixing time is 10-30 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min.

[0065] In this invention, if the ball milling time is too short, uniform coating of sulfide solid electrolyte cannot be achieved; if the ball milling time is too long, the structure of the negative electrode material will be damaged.

[0066] Preferably, the drying temperature is 80-100℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃ or 100℃, etc.

[0067] Preferably, the drying time is 2-4 hours, for example, it can be 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours.

[0068] As a preferred technical solution, the preparation method includes the following steps:

[0069] (I) Mix the silicon source with a portion of the solvent to obtain solution A; mix the alkaline catalyst with another portion of the solvent to obtain solution B;

[0070] (II) Let stand for 10-20 minutes, then mix the solution A and solution B from step (I) and react for 4-6 hours to obtain silica sol;

[0071] (III) The silica sol and nano carbon sol described in step (II) are mixed to obtain a mixed sol. The mixed sol is dried at 80-120℃ for 4-6 hours and then mixed with a reducing agent. The mixture is reacted in an inert atmosphere at 600-800℃ for 2-6 hours to obtain a silicon-based anode material.

[0072] The volume ratio of silicon source to nano-carbon sol in the silica sol is 1:(1-2), and the mass ratio of mixed sol to magnesium powder is 1:(0.1-0.2).

[0073] (IV) In an inert atmosphere, the silicon-based anode material described in step (III) is first ground with a sulfide solid electrolyte, then ball-milled at 100-200 rpm for 10-30 min, and dried at 80-100℃ for 2-4 minutes to obtain a silicon-based anode material with a sulfide solid electrolyte coating.

[0074] The mass ratio of the silicon-based anode material to the sulfide solid electrolyte is (5-9):(1-4).

[0075] Fifthly, the present invention provides a lithium-ion battery, wherein the negative electrode of the lithium-ion battery includes the silicon-based negative electrode material described in the second aspect and / or the silicon-based negative electrode material having a sulfide solid electrolyte coating layer described in the third aspect.

[0076] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The present invention adopts the in-situ gelation method to directly mix nano carbon sol with silica sol liquid phase to obtain mixed sol. After the mixed sol is subjected to reduction reaction, a porous silicon-based anode material with high conductivity can be obtained. This preparation method can make nano carbon uniformly distributed around silicon particles, which not only solves the problem of difficult dispersion of conductive agent, but also inhibits the volume expansion of silicon-based anode material during charging and discharging, and improves the battery capacity.

[0079] (2) The present invention coats the prepared silicon-based anode material with a sulfide solid electrolyte. The sulfide solid electrolyte can provide more lithium-ion channels, effectively reducing the impedance and polarization of the material during charging and discharging, and improving the electrochemical performance of the battery.

[0080] (3) The preparation method provided by the present invention is simple, environmentally friendly, and easy to promote on a large scale. Attached Figure Description

[0081] Figure 1 This is the first charge-discharge curve of a sulfide all-solid-state battery prepared from a silicon-based anode material with a solid electrolyte coating layer, as provided in Example 1 of this invention.

[0082] Figure 2 This is a cycle capacity diagram of a sulfide all-solid-state battery prepared from a silicon-based anode material with a solid electrolyte coating layer, as provided in Example 1 of this invention. Detailed Implementation

[0083] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0084] Example 1

[0085] This embodiment provides a method for preparing a silicon-based anode material, the method comprising the following steps:

[0086] (1) Add 20 mL of tetraethyl orthosilicate and 30 mL of ethanol to a beaker and stir to obtain solution A;

[0087] Add 5 mL of ammonia water and 30 mL of ethanol to another beaker and stir well to obtain solution B;

[0088] The volume ratio of tetraethyl orthosilicate to ethanol is 1:3, and the volume ratio of ammonia to ethanol is 1:12.

[0089] (2) After standing for 15 minutes, solution A and solution B are mixed and reacted for 5 hours to obtain silica sol;

[0090] (3) Pour 20 mL of nano carbon sol into silica sol, mix in the liquid phase and stir for 30 min, let stand and age for 12 h to obtain a uniform mixed sol;

[0091] The volume ratio of tetraethyl orthosilicate to nano-carbon sol in the silica sol is 1:1.

[0092] (4) The mixed sol described in step (3) is dried in a vacuum drying oven at 120°C for 6 hours and then mixed with 1g of magnesium powder. Then, magnesium thermal reduction is carried out in a tube furnace under an argon atmosphere at a temperature of 700°C for 4 hours to obtain a uniform and porous silicon-based anode material.

[0093] The mass ratio of the mixed sol to magnesium powder is 1:0.2.

[0094] This embodiment also provides a silicon-based anode material with a sulfide solid electrolyte coating layer, wherein the silicon-based anode material with a sulfide solid electrolyte coating layer is obtained by ball milling the above-mentioned silicon-based anode material and the sulfide solid electrolyte.

[0095] The silicon-based anode material with a sulfide solid electrolyte coating layer comprises a silicon-based anode material core and a sulfide solid electrolyte coating layer located on the surface of the silicon-based anode material core, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.4 PS 4.4 Cl 1.6 The mass ratio of the silicon-based anode material to the sulfide solid electrolyte is 7:3.

[0096] This embodiment also provides a method for preparing the above-mentioned silicon-based anode material with a sulfide solid electrolyte coating layer, the preparation method comprising:

[0097] In an N2 glove box, 3.5g of the above-mentioned silicon-based anode material was mixed with 1.5g of Li. 5.4 PS 4.4 Cl 1.6 The sulfide solid electrolyte was mixed and ground in an agate mortar for 10 min, then transferred to a 500 mL ball mill jar. 25 g of cyclohexane solvent and 50 g of 5 mm diameter zirconium beads were added, the jar was sealed, and the mixture was ball milled at 100 rpm for 20 min. After ball milling, the mixture was transferred to an N2 glove box for sieving to remove the zirconium beads. The powder material was then dried on a 90°C heating plate for 2 h, followed by grinding for 5 min to obtain the silicon-based anode material with a sulfide solid electrolyte coating.

[0098] Figure 1The figure shows the first charge-discharge curve of the sulfide all-solid-state battery prepared from the silicon-based anode material with a solid electrolyte coating provided in this embodiment. As can be seen from the figure, the first discharge specific capacity can reach 171 mAh / g.

[0099] Figure 2 The diagram shows the cycle capacity of a sulfide all-solid-state battery prepared from a silicon-based anode material with a solid electrolyte coating provided in this embodiment. As can be seen from the diagram, the battery is relatively stable under a current of 0.5C, and the cycle retention rate is 93% after 50 cycles.

[0100] Example 2

[0101] This embodiment provides a method for preparing a silicon-based anode material, the method comprising the following steps:

[0102] (1) Add 30 mL of tetraethyl orthosilicate and 30 mL of ethanol to a beaker and stir to obtain solution A;

[0103] Add 7.5 mL of ammonia and 30 mL of ethanol to another beaker and stir well to obtain solution B;

[0104] The volume ratio of tetraethyl orthosilicate to ethanol is 1:2, and the volume ratio of ammonia to ethanol is 1:8.

[0105] (2) After standing for 20 minutes, solution A and solution B are mixed and reacted for 6 hours to obtain silica sol;

[0106] (3) Pour 45 mL of nano carbon sol into silica sol, mix in the liquid phase and stir for 30 min, let stand and age for 12 h to obtain a uniform mixed sol;

[0107] The volume ratio of tetraethyl orthosilicate to nano-carbon sol in the silica sol is 1:1.5.

[0108] (4) After drying the mixed sol in step (3) in a vacuum drying oven at 80°C for 5 hours, it is mixed with 1g of magnesium powder and then subjected to magnesium thermal reduction in a tube furnace under a nitrogen atmosphere at a temperature of 600°C for 6 hours to obtain a uniform and porous silicon-based anode material.

[0109] The mass ratio of the mixed sol to magnesium powder is 1:0.15.

[0110] This embodiment also provides a silicon-based anode material with a sulfide solid electrolyte coating layer, wherein the silicon-based anode material with a sulfide solid electrolyte coating layer is obtained by ball milling the above-mentioned silicon-based anode material and the sulfide solid electrolyte.

[0111] The silicon-based anode material with a sulfide solid electrolyte coating layer comprises a silicon-based anode material core and a sulfide solid electrolyte coating layer located on the surface of the silicon-based anode material core, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.7 PS 4.7 Br 1.3 The mass ratio of the silicon-based anode material to the sulfide solid electrolyte is 5:4.

[0112] This embodiment also provides a method for preparing the above-mentioned silicon-based anode material with a sulfide solid electrolyte coating layer, the preparation method comprising:

[0113] In an argon-filled glove box, 3.5g of the aforementioned silicon-based anode material was mixed with 2.8g of Li. 5.7 PS 4.7 Br 1.3 The sulfide solid electrolyte was mixed and ground in an agate mortar for 10 min, then transferred to a 500 mL ball mill jar. 25 g of anisole solvent and 50 g of 5 mm diameter zirconium beads were added, the jar was sealed, and the mixture was ball milled at 200 rpm for 10 min. After ball milling, the mixture was transferred to an argon-filled glove box for sieving to remove the zirconium beads. The powder material was then dried on an 80°C heating plate for 4 h, followed by grinding for another 5 min to obtain the silicon-based anode material with a sulfide solid electrolyte coating.

[0114] Example 3

[0115] This embodiment provides a method for preparing a silicon-based anode material, the method comprising the following steps:

[0116] (1) Add 10 mL of tetraethyl orthosilicate and 30 mL of ethanol to a beaker and stir to obtain solution A;

[0117] Add 3.8 mL of ammonia and 30 mL of ethanol to another beaker and stir well to obtain solution B;

[0118] The volume ratio of tetraethyl orthosilicate to ethanol is 1:6, and the volume ratio of ammonia to ethanol is 1:15.8.

[0119] (2) After standing for 10 minutes, solution A and solution B are mixed and reacted for 4 hours to obtain silica sol;

[0120] (3) Pour 20 mL of nano carbon sol into silica sol, mix in the liquid phase and stir for 30 min, let stand and age for 12 h to obtain a uniform mixed sol;

[0121] The volume ratio of tetraethyl orthosilicate to nano-carbon sol in the silica sol is 1:2.

[0122] (4) The mixed sol described in step (3) is dried at 100°C under normal pressure for 4 hours and then mixed with 1g of magnesium powder. Then, magnesium thermal reduction is carried out in a tube furnace under an argon atmosphere at a temperature of 800°C for 2 hours to obtain a uniform and porous silicon-based anode material.

[0123] The mass ratio of the mixed sol to magnesium powder is 1:0.1.

[0124] This embodiment also provides a silicon-based anode material with a sulfide solid electrolyte coating layer, wherein the silicon-based anode material with a sulfide solid electrolyte coating layer is obtained by ball milling the above-mentioned silicon-based anode material and the sulfide solid electrolyte.

[0125] The silicon-based anode material with a sulfide solid electrolyte coating layer includes a silicon-based anode material core and a sulfide solid electrolyte coating layer located on the surface of the silicon-based anode material core, wherein the chemical formula of the sulfide solid electrolyte is Li6PS5Cl, and the mass ratio of the silicon-based anode material to the sulfide solid electrolyte is 9:1.

[0126] This embodiment also provides a method for preparing the above-mentioned silicon-based anode material with a sulfide solid electrolyte coating layer, the preparation method comprising:

[0127] In an N2 glove box, 3.5g of the above-mentioned silicon-based anode material and 0.4g of Li6PS5Cl sulfide solid electrolyte were mixed and ground in an agate mortar for 10 minutes. Then, the mixture was transferred to a 500mL ball mill jar, 25g of dichloromethane solvent and 50g of 5mm diameter zirconium beads were added, the jar was sealed, and the mixture was ball milled at 150rpm for 30 minutes. After ball milling, the mixture was transferred to an N2 glove box for sieving to remove the zirconium beads. The powder material was then dried on a 100°C heating plate for 3 hours, and then ground for another 5 minutes to obtain the silicon-based anode material with a sulfide solid electrolyte coating.

[0128] Example 4

[0129] The difference between this embodiment and Embodiment 1 is that the volume of ammonia water is 20 mL, so the volume ratio of tetraethyl orthosilicate to ammonia water is 1:1.

[0130] The remaining preparation methods and parameters are consistent with those in Example 1.

[0131] Example 5

[0132] The difference between this embodiment and Embodiment 1 is that the volume of ammonia is 2.5 mL, so the volume ratio of tetraethyl orthosilicate to ammonia is 8:1.

[0133] The remaining preparation methods and parameters are consistent with those in Example 1.

[0134] Example 6

[0135] The difference between this embodiment and Example 1 is that the volume of the nano-carbon sol is 50 mL, so the volume ratio of tetraethyl orthosilicate to nano-carbon sol in the silica sol is 1:2.5.

[0136] The remaining preparation methods and parameters are consistent with those in Example 1.

[0137] Example 7

[0138] The difference between this embodiment and Example 1 is that the volume of the nano-carbon sol is 10 mL, so the volume ratio of tetraethyl orthosilicate to nano-carbon sol in the silica sol is 1:0.5.

[0139] The remaining preparation methods and parameters are consistent with those in Example 1.

[0140] Example 8

[0141] The difference between this embodiment and Embodiment 1 is that Li 5.4 PS 4.4 Cl 1.6 The mass of the sulfide solid electrolyte is 4.375 g. Then the silicon-based anode material and Li... 5.4 PS 4.4 Cl 1.6 The mass ratio of the sulfide solid electrolyte is 4:5.

[0142] The remaining preparation methods and parameters are consistent with those in Example 1.

[0143] Example 9

[0144] The difference between this embodiment and Embodiment 1 is that Li 5.4 PS 4.4 Cl 1.6 If the mass of the sulfide solid electrolyte is 0.35 g, then the silicon-based anode material and Li 5.4 PS 4.4 Cl 1.6 The mass ratio of the sulfide solid electrolyte is 10:1.

[0145] The remaining preparation methods and parameters are consistent with those in Example 1.

[0146] Example 10

[0147] The difference between this embodiment and Embodiment 1 is that in the preparation method of the silicon-based anode material with a sulfide solid electrolyte coating, the silicon-based anode material and the sulfide solid electrolyte are directly ball-milled and mixed.

[0148] The remaining preparation methods and parameters are consistent with those in Example 1.

[0149] Example 11

[0150] The difference between this embodiment and Embodiment 1 is that no sulfide solid electrolyte is added for coating.

[0151] The remaining preparation methods and parameters are consistent with those in Example 1.

[0152] Comparative Example 1

[0153] The difference between this comparative example and Example 1 is that the silica sol is replaced with a non-sol-state silica solution.

[0154] The remaining preparation methods and parameters are consistent with those in Example 1.

[0155] Comparative Example 2

[0156] The difference between this comparative example and Example 1 is that the nano-carbon sol is replaced with carbon nanofibers.

[0157] The remaining preparation methods and parameters are consistent with those in Example 1.

[0158] Comparative Example 3

[0159] The difference between this comparative example and Example 1 is that the silicon-based anode material was not prepared, but was purchased directly from the market.

[0160] The remaining preparation methods and parameters are consistent with those in Example 1.

[0161] Comparative Example 4

[0162] The difference between this comparative example and Example 1 is that in the preparation method of the silicon-based anode material with a sulfide solid electrolyte coating, the ball milling method is replaced by conventional mortar grinding, that is, the silicon-based anode material and the sulfide solid electrolyte are mixed and ground in an agate mortar for 30 minutes.

[0163] The remaining preparation methods and parameters are consistent with those in Example 1.

[0164] Performance testing

[0165] The silicon-based anode materials with sulfide solid electrolyte coatings provided in Examples 1-11 and Comparative Examples 1-4 were used to assemble sulfide all-solid-state batteries to evaluate their electrochemical performance.

[0166] Assembly process: Ternary cathode material and sulfide solid electrolyte powder are compounded at a mass ratio of 4:1 to obtain the cathode material of the sulfide all-solid-state battery system. The silicon-based anode materials with sulfide solid electrolyte coating provided in Examples 1-11 and Comparative Examples 1-4 are used as anode materials. The cathode material, sulfide solid electrolyte layer and anode material are pressed into shape in a PEEK sleeve, with an efficiency of ≥2.5 mA / cm².2 The surface capacity was used to fabricate a sulfide all-solid-state battery.

[0167] Electrochemical tests were performed using an electrochemical workstation under the following conditions: 0.1C, 0.5C, and 2.80-4.25V. The initial discharge specific capacity, initial coulombic efficiency, and 0.5C room temperature cycling performance were measured.

[0168] The test results are shown in Table 1.

[0169] Table 1

[0170]

[0171]

[0172] analyze:

[0173] The data from Examples 1-3 show that the silicon-based anode material with a sulfide solid electrolyte coating prepared in this invention exhibits superior electrochemical capacity, first-cycle coulombic efficiency, and cycle retention rate after 50 cycles when used in a sulfide solid-state battery system. This indicates that the preparation method of this invention can significantly improve the capacity utilization, first-cycle coulombic efficiency, and cycle stability of the anode material.

[0174] A comparison of the data results from Examples 1 and 4-5 shows that both excessively small and excessively large volume ratios of tetraethyl orthosilicate and catalyst will affect the electrochemical performance, resulting in reduced capacity, first-time efficiency, and capacity retention.

[0175] A comparison of the data from Examples 1 and 6-7 shows that if the volume ratio of silicon source to nano-carbon sol in the silica sol is too small (i.e., the amount of nano-carbon sol used is too large), the prepared anode material will have a smaller capacity. Conversely, if the volume ratio is too large (i.e., the amount of nano-carbon sol used is too small), the prepared anode material will have lower conductivity and more severe volume expansion. Both of these factors will lead to a decrease in the electrochemical performance of the product.

[0176] A comparison of the data from Examples 1 and 8-9 shows that if the mass ratio of silicon-based anode material to sulfide solid electrolyte is too small (i.e., too much sulfide solid electrolyte is used), the electrode can only achieve a low capacity; if the mass ratio is too large (i.e., too little sulfide solid electrolyte is used), there are fewer lithium-ion channels, resulting in increased impedance during charge and discharge. Both are detrimental to battery cycling.

[0177] A comparison of the data results from Examples 1 and 10 shows that direct ball milling without grinding and premixing will cause unmixed components to adhere to the surface of the balls and the ball milling jar and be lost, affecting the actual material ratio and hindering battery cycling.

[0178] A comparison of the data results from Examples 1 and 11 shows that the battery system cannot be charged and discharged normally because the material itself has fewer lithium-ion channels and poor lithium-ion transport, without the addition of a sulfide solid electrolyte for coating.

[0179] A comparison of the data results from Example 1 and Comparative Example 1 shows that when silica sol is replaced with a non-sol-state silica solution, its dispersion performance is poor, and it cannot be uniformly mixed with nano-carbon sol, resulting in poor electrochemical performance.

[0180] A comparison of the data results from Example 1 and Comparative Example 2 shows that when carbon nanofibers are replaced with carbon nanosol, the carbon nanofibers exhibit severe agglomeration and extremely poor dispersibility, resulting in uneven mixing with the silica sol and consequently poor electrochemical performance.

[0181] A comparison of the data results from Example 1 and Comparative Example 3 shows that when commercially available silicon-based anode materials are used in sulfide solid-state batteries, the anode performance is poor, which may be due to their poor conductivity.

[0182] A comparison of the data results from Example 1 and Comparative Example 4 shows that without the ball milling mixing process, the sulfide solid electrolyte and the silicon-based anode material cannot be uniformly coated, resulting in poor electrochemical performance.

[0183] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a silicon-based anode material, characterized in that, The preparation method includes the following steps: A mixed sol is obtained by mixing silica sol and nano carbon sol, and a reduction reaction is carried out to obtain the silicon-based anode material; The method for preparing the silica sol includes: A silicon source, a catalyst, and a solvent are mixed and reacted to obtain the silica sol; the catalyst includes an alkaline catalyst; the volume ratio of the silicon source to the catalyst is (3-5):1; The reduction reaction process includes: The mixed sol was dried at 80-120℃ for 4-6 h and then mixed with a reducing agent. The mixture was then reacted in an inert atmosphere at 600-800℃ for 2-6 h to obtain a silicon-based anode material.

2. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The silicon source includes tetraethyl orthosilicate.

3. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The alkaline catalyst includes ammonia.

4. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The solvent includes ethanol.

5. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The volume ratio of the silicon source to the solvent is 1:(2-6).

6. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The volume ratio of the catalyst to the solvent is 1:(8-16).

7. The method for preparing the silicon-based anode material according to claim 1, characterized in that, In the method for preparing the silica sol, the reaction time is 4-6 hours.

8. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The specific mixing steps in the preparation process of the silica sol include: (1) Mix the silicon source and a portion of the solvent to obtain solution A; The catalyst and another portion of the solvent were mixed to obtain solution B; (2) Mix the solution A and the solution B from step (1) to obtain the silica sol.

9. The method for preparing the silicon-based anode material according to claim 8, characterized in that, Solution A and solution B are allowed to stand separately before being mixed, and the standing time is independently 10-20 minutes.

10. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The volume ratio of silicon source to nano-carbon sol in the silica sol is 1:(1-2).

11. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The drying methods include atmospheric pressure drying or vacuum drying.

12. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The reducing agent includes magnesium powder.

13. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The mass ratio of the mixed sol to the reducing agent is 1:(0.1-0.2).

14. The method for preparing the silicon-based anode material according to claim 1, characterized in that, The reduction reaction is carried out in an inert atmosphere, wherein the gas in the inert atmosphere includes nitrogen and / or argon.

15. A silicon-based anode material prepared by the preparation method according to any one of claims 1-14, characterized in that, The silicon-based anode material is a porous silicon-based anode material.

16. A silicon-based anode material having a sulfide solid electrolyte coating layer, characterized in that, The silicon-based anode material with a sulfide solid electrolyte coating is obtained by ball milling the silicon-based anode material of claim 15 and the sulfide solid electrolyte.

17. The silicon-based anode material according to claim 16, characterized in that, The silicon-based anode material with a sulfide solid electrolyte coating layer includes a silicon-based anode material core and a sulfide solid electrolyte coating layer located on the surface of the silicon-based anode material core.

18. The silicon-based anode material according to claim 16, characterized in that, The chemical formula of the sulfide solid electrolyte is Li 6-x PS 5-x M 1+x , 0≤x≤0.6, M includes any one or at least two of Cl, Br or I.

19. The silicon-based anode material according to claim 18, characterized in that, The chemical formula of the sulfide solid electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

20. The silicon-based anode material according to claim 18, characterized in that, The mass ratio of the silicon-based anode material to the sulfide solid electrolyte is (5-9):(1-4).

21. A method for preparing a silicon-based anode material with a sulfide solid electrolyte coating as described in claim 18, characterized in that, The preparation method includes: A silicon-based anode material is prepared by the preparation method according to any one of claims 1-14. The silicon-based anode material is ball-milled and mixed with the sulfide solid electrolyte, and then dried to obtain the composite silicon-based anode material with a sulfide solid electrolyte coating layer.

22. The preparation method according to claim 21, characterized in that, The atmosphere in which the silicon-based anode material is mixed with the sulfide solid electrolyte is an inert atmosphere, and the gas in the inert atmosphere includes nitrogen and / or argon.

23. The preparation method according to claim 21, characterized in that, The silicon-based anode material is ground before being ball-milled and mixed with the sulfide solid electrolyte.

24. The preparation method according to claim 21, characterized in that, The ball milling mixing method includes wet ball milling, followed by a drying step.

25. The preparation method according to claim 24, characterized in that, The solvent used in the wet ball milling includes any one or a combination of at least two of cyclohexane, anisole, isobutyl isobutyrate, or dichloromethane.

26. The preparation method according to claim 25, characterized in that, The solvent used in the wet ball milling is cyclohexane.

27. The preparation method according to claim 21, characterized in that, The ball milling speed is 100-200 rpm.

28. The preparation method according to claim 21, characterized in that, The ball milling mixing time is 10-30 minutes.

29. The preparation method according to claim 21, characterized in that, The drying temperature is 80-100℃.

30. The preparation method according to claim 21, characterized in that, The drying time is 2-4 hours.

31. The preparation method according to claim 21, characterized in that, The preparation method includes the following steps: (I) Mix the silicon source with a portion of the solvent to obtain solution A; mix the alkaline catalyst with another portion of the solvent to obtain solution B; (II) Let stand for 10-20 minutes, then mix solution A and solution B from step (I) and react for 4-6 hours to obtain silica sol; (III) The silica sol and nano carbon sol described in step (II) are mixed to obtain a mixed sol. The mixed sol is dried at 80-120℃ for 4-6 hours and then mixed with a reducing agent. The mixture is reacted in an inert atmosphere at 600-800℃ for 2-6 hours to obtain a silicon-based anode material. The volume ratio of silicon source to nano-carbon sol in the silica sol is 1:(1-2), and the mass ratio of mixed sol to reducing agent is 1:(0.1-0.2). (IV) In an inert atmosphere, the silicon-based anode material described in step (III) is first ground with a sulfide solid electrolyte, then ball-milled at 100-200 rpm for 10-30 min, and dried at 80-100℃ for 2-4 minutes to obtain a silicon-based anode material with a sulfide solid electrolyte coating. The mass ratio of the silicon-based anode material to the sulfide solid electrolyte is (5-9):(1-4).

32. A lithium-ion battery, characterized in that, The negative electrode of the lithium-ion battery includes the silicon-based negative electrode material as described in claim 15 and / or the silicon-based negative electrode material with a sulfide solid electrolyte coating as described in claim 16.

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