Silicon-based composite negative electrode material for all-solid-state lithium battery and preparation method of silicon-based composite negative electrode material

Abstract

The invention provides a silicon-based composite negative electrode material for an all-solid-state lithium battery and a preparation method of the silicon-based composite negative electrode material. The silicon-based composite negative electrode material for the all-solid-state lithium battery comprises the following components in percentage by mass: 55-90% of a silicon substrate, which comprises silicon powder or a silicon carbon material; the magnesium doping agent comprises magnesium powder and magnesium nitride, and the mass fraction of the magnesium doping agent is 5%-40%; and the auxiliary component comprises a conductive agent and an adhesive. According to the silicon-based composite negative electrode material for the all-solid-state lithium battery and the preparation method of the silicon-based composite negative electrode material, metal magnesium and magnesium nitride are doped into a silicon-based negative electrode, so that collaborative lithium storage of silicon and lithium deposition is realized, lithium dendrite growth can be effectively inhibited, interface contact is improved, rate performance is improved, and energy density and cycling stability are improved.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, and more specifically, to a silicon-based composite anode material for all-solid-state lithium batteries and a method for preparing the same. Background Technology

[0002] In existing technologies, the safety hazards of lithium-ion batteries have always been a focus of industry attention. The liquid electrolyte in traditional lithium-ion batteries is prone to thermal runaway under conditions such as high temperatures, impact, or puncture, leading to battery failure or even explosion. This severely limits the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and other fields. All-solid-state batteries, by using solid electrolytes instead of liquid electrolytes, offer advantages such as high energy density (theoretical energy density can reach over 500Wh / kg) and excellent safety (no electrolyte leakage or combustion risk), and are considered the core development direction for next-generation power batteries. The negative electrode material, as a key component of all-solid-state batteries, directly affects the battery's lithium storage capacity and cycle stability.

[0003] Silicon-based anodes have become the preferred material for all-solid-state batteries due to their extremely high theoretical lithium storage capacity (4200 mAh / g, more than 10 times that of traditional graphite anodes), environmental friendliness, and abundant reserves. In existing technologies, to alleviate the problems of electrode pulverization and cycle performance degradation caused by volume expansion (expansion rate can reach 300%) during charge and discharge of silicon-based anodes, solutions such as "silicon-carbon composites," "nanostructured silicon," or "metal doping" are commonly used.

[0004] Chinese patent CN120109182A discloses "a silicon-carbon composite anode material for lithium-ion batteries and its preparation method". By coating silicon nanoparticles in a porous carbon matrix, the volume expansion of silicon is alleviated, but the lithium metal deposition process is not involved and the lithium diffusion coefficient of the carbon-based material is limited at low rates.

[0005] Chinese patent CN119650661A discloses "a silicon-tin-carbon composite material and its preparation method and application." The addition of tin improves the conductivity of the silicon-based anode, but tin has weak control over lithium metal deposition, making it impossible to achieve uniform lithium deposition at high current densities. Furthermore, the lithium-tin alloy has a low diffusion coefficient (approximately 5 × 10⁻⁶). -11 (cm² / s), resulting in poor battery rate performance;

[0006] Youngjin Song et al. proposed an Al-Si alloy anode in their 2025 paper published in *Advanced Functional Materials* (DOI: 10.1002 / adfm.202504739): Al accounts for 88% of the mass, and the initial lithiation volume expansion rate is approximately 37.5% (far lower than the 300%+ of pure silicon). However, the high aluminum content severely affects the energy density, and the diffusion coefficient of the Li-Al alloy is approximately 5 × 10⁻⁶. -10 cm 2 / s, 2C capacity retention is only 50%.

[0007] Based on the aforementioned existing technologies, silicon-based anodes in all-solid-state lithium batteries currently suffer from the following core defects:

[0008] Poor interface contact performance: Existing silicon-based anodes have poor interfacial compatibility with solid electrolytes, and current silicon-carbon materials are too hard and lack ductility to fill the gaps caused by silicon volume expansion, resulting in the battery needing to maintain a high pressure (greater than 100MPa) to operate, which increases equipment loss and energy consumption.

[0009] A trade-off exists between rate performance and cycle stability: Existing solutions that mitigate silicon volume expansion (such as carbon coating) often lead to prolonged lithium diffusion paths, and alloys formed by doped metals have low diffusion coefficients (≤1×10⁻⁶). -10 The capacity of the battery is reduced to cm² / s, resulting in poor capacity performance at high rates (2C and above). In addition, the poor resilience of carbon materials means that they cannot be repaired after breakage, leading to severe capacity decay. After 500 cycles, the capacity retention rate is generally less than 50%.

[0010] The lithium storage mechanism is too simple: existing silicon-based anodes mainly rely on the lithium storage capacity of silicon, and do not make full use of the additional capacity of lithium metal deposition, resulting in the overall lithium storage efficiency of the anode not reaching the optimal level.

[0011] Insufficient suppression of lithium dendrites: Existing doped metals (tin, aluminum, etc.) have weak lithium affinity and cannot control the uniform deposition of lithium metal at high current densities (≥4mA / cm²). Lithium dendrites can easily pierce the solid electrolyte, causing battery safety risks.

[0012] Therefore, there is a need in the prior art for a silicon-based composite anode material and its preparation method for all-solid-state lithium batteries, in order to solve the problem of insufficient electrochemical performance and cycle stability of existing silicon-based composite anode materials for all-solid-state lithium batteries. Summary of the Invention

[0013] The main objective of this invention is to provide a silicon-based composite anode material for all-solid-state lithium batteries and its preparation method, so as to solve the problems of insufficient electrochemical performance and cycle stability of existing silicon-based composite anode materials for all-solid-state lithium batteries.

[0014] To achieve the above objectives, according to one aspect of the present invention, a silicon-based composite anode material for all-solid-state lithium batteries is provided, comprising the following components:

[0015] A silicon matrix comprising 55%-90% by mass, including silicon powder or silicon-carbon materials;

[0016] Magnesium dopants with a mass fraction of 5%-40%, including magnesium powder and magnesium nitride;

[0017] Auxiliary components, including conductive agents and binders, are present in a mass fraction of 3%-8%.

[0018] Furthermore, in the silicon-based composite anode material for all-solid-state lithium batteries described above, the silicon powder is nano-silicon powder with a particle size of 50-100nm and / or micro-silicon powder with a particle size of 1-3µm, preferably nano-silicon powder with a particle size of 50-100nm.

[0019] Furthermore, in the aforementioned silicon-based composite anode material for all-solid-state lithium batteries, the particle size of the silicon-carbon material is 1-10µm, preferably 1-3µm.

[0020] Furthermore, in the aforementioned silicon-based composite anode material for all-solid-state lithium batteries, the particle size of the magnesium powder is 30-500 μm, preferably 30-50 μm.

[0021] Furthermore, in the aforementioned silicon-based composite anode material for all-solid-state lithium batteries, the magnesium nitride has a particle size of 1-10µm.

[0022] Furthermore, in the aforementioned silicon-based composite anode material for all-solid-state lithium batteries, the conductive agent includes vapor-grown carbon fiber (VGCF).

[0023] Furthermore, in the aforementioned silicon-based composite anode material for all-solid-state lithium batteries, the binder includes styrene-ethylene-butadiene copolymer (SEBS).

[0024] According to another aspect of the present invention, a method for preparing the above-mentioned silicon-based composite anode material for all-solid-state lithium batteries is provided, comprising the following steps:

[0025] 1) The silicon substrate material is ball-milled to obtain a pretreated silicon substrate;

[0026] 2) The pretreated silicon substrate, the magnesium powder, and the magnesium nitride are added to an organic solvent and mixed to obtain a mixed slurry;

[0027] 3) Mix the slurry with the conductive agent and the adhesive and dry it.

[0028] According to another aspect of the present invention, a negative electrode for an all-solid-state lithium battery is provided, the negative electrode comprising the aforementioned silicon-based composite negative electrode material for an all-solid-state lithium battery.

[0029] According to another aspect of the present invention, an all-solid-state lithium battery is provided, the all-solid-state lithium battery including the above-described negative electrode for an all-solid-state lithium battery.

[0030] Furthermore, in the above-mentioned all-solid-state lithium battery, the N / P ratio of the negative electrode to the positive electrode of the all-solid-state lithium battery is >0 and ≤0.6.

[0031] The silicon-based composite anode material for all-solid-state lithium batteries of the present invention achieves synergistic lithium storage of silicon and lithium deposition by incorporating metallic magnesium and magnesium nitride into the silicon-based anode. This can effectively suppress lithium dendrite growth, improve interface contact, and enhance rate performance, thereby improving energy density and cycle stability. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram illustrating the lithium intercalation process of silicon-based anode materials for all-solid-state lithium batteries in the prior art and silicon-based composite anode materials for all-solid-state lithium batteries according to embodiments of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present application, the technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0035] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] As explained in the background section, existing silicon-based composite anode materials for all-solid-state lithium batteries suffer from insufficient electrochemical performance and cycle stability. To address these problems, according to a typical embodiment of the present invention, a silicon-based composite anode material for all-solid-state lithium batteries is provided, comprising the following components:

[0037] A silicon matrix comprising 55%-90% by mass, including silicon powder or silicon-carbon materials;

[0038] Magnesium dopants with a mass fraction of 5%-40%, including magnesium powder and magnesium nitride;

[0039] Auxiliary components, including conductive agents and binders, are present in a mass fraction of 3%-8%.

[0040] This invention achieves a comprehensive improvement in the performance of silicon-based anodes for all-solid-state batteries by incorporating magnesium and magnesium nitride into silicon-based composite anode materials used in all-solid-state lithium batteries through the "silicon-magnesium synergistic effect" and the specific ratio of the above components. The specific effects are as follows:

[0041] 1. Synergistic lithium storage to increase capacity

[0042] The silicon substrate provides the basic lithium storage capacity (contributing 60%-70% of the total capacity), while metallic magnesium forms Li-Mg alloys with lithium (such as L...). M It provides additional lithium storage capacity (contributing 10%-15% of the total capacity) and guides the uniform deposition of lithium metal (contributing 15%-20% of the total capacity). The three work together to enable the first discharge capacity of the anode to reach 3800-4500mAh / g, which is 15%-20% higher than that of pure silicon anode.

[0043] 2. Regulate lithium deposition and suppress dendrite formation.

[0044] Magnesium metal possesses a strong affinity for lithium, serving as an "inducing site" for lithium deposition and guiding the uniform nucleation of lithium metal along magnesium particles. Simultaneously, lithium intercalation in magnesium nitride forms lithium-magnesium alloys and lithium nitride. These alloys and nitride exhibit high ionic conductivity, promoting uniform lithium-ion transport and increasing the lithium deposition current density to 5-7 mA / cm² (100%-300% higher than pure silicon anodes), while exhibiting no significant lithium dendrite formation at this current density. See also Figure 1 The diagram illustrates how the silicon-based composite anode material of this invention suppresses dendrite formation compared to existing silicon-based materials. Furthermore, while lithium nitride produced by the magnesium nitride reaction helps improve rate performance, pure magnesium nitride has low reactivity and suffers from lithium intercalation expansion. Introducing metallic magnesium, however, enhances its reactivity and suppresses volume expansion.

[0045] 3. Improve interface contact and reduce operating pressure.

[0046] The Li-Mg alloy formed by the aforementioned magnesium and lithium is soft (hardness ≤0.8GPa, only 1 / 3 of that of Li-Al alloy), which can fill the gaps caused by the volume expansion of silicon (expansion rate reduced to 150%-180%, 40%-45% lower than that of pure silicon anode), thereby increasing the interfacial contact area between the anode and the solid electrolyte by 30%-40%, and reducing the battery operating pressure from the traditional >100MPa to <5MPa, significantly reducing equipment energy consumption and packaging costs.

[0047] 4. Improve the diffusion coefficient and optimize rate performance.

[0048] The lithium diffusion coefficient of the Li-Mg alloy formed by the above-mentioned magnesium and lithium is 0.9-1.5×10⁻⁹ cm² / s (9-15 times higher than that of pure lithium, which is 1×10⁻¹⁰ cm² / s). The lithium nitride formed by lithium intercalation in magnesium nitride exhibits high lithium-ion conductivity (1×10⁻⁹ cm² / s). - 3 The S / cm ratio doubles to accelerate lithium-ion transport, shortening the diffusion path of lithium inside the anode; at 2C rate, the anode capacity retention can reach 70%-88% (30%-45% higher than silicon anode).

[0049] 5. Enhances cycle stability

[0050] Magnesium nitride and silicon exhibit severe volume expansion during lithium intercalation. The presence of magnesium not only alleviates the volume expansion of silicon and magnesium nitride, but also repairs interfacial microcracks through the "self-healing" effect of the Li-Mg alloy. After 500 cycles, the anode capacity retention rate still reaches 80%-85% (120%-150% higher than that of pure silicon anode), and the cycle life is significantly extended.

[0051] The silicon-based composite anode material for all-solid-state lithium batteries of the present invention solves the following technical problems:

[0052] 1. Achieve synergistic lithium storage through silicon, magnesium, and lithium metal deposition to improve the overall lithium storage capacity of the anode;

[0053] 2. Enhanced ability to control lithium metal deposition, suppressing lithium dendrite growth at high current densities (≥12mA / cm²) to ensure battery safety;

[0054] 3. Improve the interfacial contact between the negative electrode and the solid electrolyte, and reduce the battery operating pressure (≤2MPa).

[0055] 4. Improve lithium diffusion coefficient and optimize battery rate performance (capacity retention ≥80% at 2C) and cycle stability (capacity retention ≥80% after 500 cycles).

[0056] In summary, the silicon-based composite anode material for all-solid-state lithium batteries of the present invention achieves synergistic lithium storage of silicon and lithium deposition by incorporating metallic magnesium and magnesium nitride into the silicon-based anode, which can improve the rate performance, energy density and cycle stability of all-solid-state lithium batteries.

[0057] In a preferred embodiment, the silicon powder is nano-silicon powder with a particle size of 50-100nm and / or micro-silicon powder with a particle size of 1-3µm, preferably nano-silicon powder with a particle size of 50-70nm.

[0058] In a preferred embodiment, the particle size of the silicon-carbon material is 1-10µm, preferably 1-3µm.

[0059] In a preferred embodiment, the magnesium powder has a particle size of 30-500 μm.

[0060] In a preferred embodiment, the magnesium nitride has a particle size of 1-10 µm.

[0061] In a preferred embodiment, the conductive agent includes superconducting carbon black, carbon nanotubes, and vapor-grown carbon fiber (VGCF), preferably vapor-grown carbon fiber (VGCF).

[0062] In a preferred embodiment, the adhesive comprises polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-ethylene-butadiene copolymer (SEBS), preferably styrene-ethylene-butadiene copolymer (SEBS).

[0063] In a preferred embodiment, the silicon-based composite anode material for all-solid-state lithium batteries of the present invention comprises the following components:

[0064] Silicon matrix: 55%-90% by mass, using nano-silicon powder with a particle size of 50-100nm, micro-silicon powder with a particle size of 1-3µm, and / or silicon-carbon material with a particle size of 1-10µm (purity ≥99.9%), to provide basic lithium storage capacity;

[0065] Magnesium dopant: 5%-40% by mass, using magnesium powder with a particle size of 30μm-500μm (purity ≥99.5%) and magnesium nitride with a particle size of 10μm, which has both lithium storage and lithium deposition regulation functions.

[0066] Auxiliary components: 3%-8% by mass, including conductive agent (VGCF, 2%-5% by mass) and binder (SEBS, 1%-3% by mass), which are used to improve conductivity and electrode formability, respectively.

[0067] Using the specific components and their parameters (such as particle size) described above in the silicon-based composite anode material for all-solid-state lithium batteries of the present invention is beneficial to further improve the electrochemical performance and cycle stability of all-solid-state lithium batteries.

[0068] According to another embodiment of the present invention, a method for preparing the above-mentioned silicon-based composite anode material for all-solid-state lithium batteries is provided, comprising the following steps:

[0069] 1) The silicon substrate material is ball-milled to obtain a pretreated silicon substrate;

[0070] 2) The pretreated silicon substrate, the magnesium powder, and the magnesium nitride are added to an organic solvent and mixed to obtain a mixed slurry;

[0071] 3) Mix the slurry with the conductive agent and the adhesive and dry it.

[0072] The method of the present invention for preparing silicon-based composite anode materials for all-solid-state lithium batteries has yielded silicon-based composite anode materials for all-solid-state lithium batteries with improved electrochemical performance and cycle stability.

[0073] In a preferred embodiment, the method for preparing a silicon-based composite anode for all-solid-state lithium batteries includes the following steps:

[0074] Step 1: Silicon powder pretreatment

[0075] Nano-silicon powder is placed in a planetary ball mill under an argon atmosphere and ball-milled for 1-2 hours at a ball-to-powder ratio of 10:1 and a rotation speed of 300-400 rpm to remove the oxide layer on the surface of the silicon powder and refine the particle size, thus obtaining pretreated silicon powder.

[0076] Step 2: Mixing and dispersing silicon and magnesium

[0077] Pretreated silicon powder, magnesium powder, and magnesium nitride powder are added to xylene according to the set mass ratio, and then transferred to a planetary ball mill (speed 200-300 rpm) and mixed for 1-10 hours to obtain a mixed slurry of silicon, magnesium, and magnesium nitride.

[0078] Step 3: Shaping and Drying

[0079] Add binder and conductive agent to the silicon-magnesium mixture slurry, stir evenly, and then coat it onto the copper current collector (thickness 5-15μm), with the coating thickness controlled at 10-100μm; then place the coated electrode in a vacuum oven and dry it at 60-80℃ for 8-12 hours to remove the solvent.

[0080] Using the specific components and parameters (such as ball milling parameters, drying parameters, etc.) described above in the method of the present invention for preparing silicon-based composite anode materials (or anodes) for all-solid-state lithium batteries is beneficial to further improve the electrochemical performance and cycle stability of all-solid-state lithium batteries.

[0081] According to another embodiment of the present invention, a negative electrode for an all-solid-state lithium battery is provided, the negative electrode comprising the aforementioned silicon-based composite negative electrode material for an all-solid-state lithium battery.

[0082] According to another embodiment of the present invention, an all-solid-state lithium battery is provided, the all-solid-state lithium battery including the above-described negative electrode for an all-solid-state lithium battery.

[0083] Through the silicon-based composite anode material for all-solid-state lithium batteries of the present invention, an anode for all-solid-state lithium batteries with improved electrochemical performance and cycle stability are obtained, as well as all-solid-state lithium batteries.

[0084] In a preferred embodiment, the N / P ratio of the negative electrode to the positive electrode of the all-solid-state lithium battery is >0 and ≤0.6.

[0085] In the all-solid-state lithium battery using the silicon-based composite anode of the present invention, by controlling the ratio of anode capacity to cathode capacity (N / P ratio) within a specific range, the energy density is improved and the stacking pressure is reduced by utilizing the coordinated lithium storage of silicon and lithium metal, which is beneficial to further improving the electrochemical performance and cycle stability of the all-solid-state lithium battery.

[0086] Example

[0087] In the following examples, all-solid-state lithium batteries were prepared and their performance was tested.

[0088] Example 1

[0089] Negative electrode preparation: Weigh 1.80g of nano-silicon powder (50-70nm), 0.338g of magnesium powder (30μm), and 0.15g of magnesium nitride (10μm), add them to 12mL of xylene, transfer to a planetary ball mill, and mix at 250rpm for 8 hours. The magnesium powder and magnesium nitride are uniformly dispersed in the gaps between the silicon powder by mechanical force to obtain a silicon-magnesium-nitride mixed slurry. Add 0.086g of vapor-grown carbon fiber (VGCF) and 0.057g of styrene-ethylene-butadiene copolymer (SEBS) to the silicon-magnesium mixed slurry, and stir at 2000rpm for 30 minutes to form a uniform slurry. Coat the slurry onto a copper current collector (10μm thick) using a doctor blade coater, controlling the coating thickness to 30μm. Place the electrode in a vacuum oven and dry at 80℃ for 10 hours to remove the xylene solvent, obtaining a silicon-based composite negative electrode.

[0090] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode (NCM811 positive electrode, the same below) is used as the counter electrode and pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0091] Example 2

[0092] Negative electrode preparation: Weigh 1.50g of nano-silicon powder (50-70nm), 0.692g of magnesium powder (30μm), and 0.3g of magnesium nitride (10μm), add them to 12mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0093] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0094] Example 3

[0095] Negative electrode preparation: Weigh 1.40g of micron-sized silicon powder (2-3μm), 0.50g of magnesium powder (200-300μm), and 0.2g of magnesium nitride (10μm), add them to 100mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.076g of VGCF and 0.051g of SEBS to the silicon-magnesium mixed slurry, and stir at 2000rpm for 30 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0096] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0097] Example 4

[0098] Negative electrode preparation: Weigh 1.80g silicon-carbon material (5-8μm), 0.338g magnesium powder (30μm), and 0.15g magnesium nitride (10μm), add them to 12mL xylene, transfer to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.086g VGCF and 0.057g SEBS to the silicon-magnesium mixed slurry, and stir at 2000rpm for 30 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 45μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0099] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0100] Example 5

[0101] Negative electrode preparation: Weigh 1.50g silicon-carbon material (1-3μm), 0.692g magnesium powder (30μm), and 0.3g magnesium nitride (10μm), add them to 12mL xylene, transfer to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g VGCF and 0.058g SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 45μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0102] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0103] Example 6

[0104] Negative electrode preparation: Weigh 1.50g of nano-silicon powder (50-70nm), 0.692g of magnesium powder (30μm), and 0.3g of magnesium nitride (10μm), add them to 12mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 60μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0105] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 1.2.

[0106] Example 7

[0107] Anode preparation: Weigh 1.50g of nano-silicon powder (50-70nm), 0.692g of magnesium powder (30μm), and 0.3g of magnesium nitride (10μm), add them to 12mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 45μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite anode.

[0108] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.9.

[0109] Comparative Example 1

[0110] Negative electrode preparation: Weigh 2.30g of nano-silicon powder (50-70nm), add it to 12mL of xylene, transfer it to a planetary ball mill, and mix for 8 hours at 250rpm to obtain a silicon slurry; add 0.086g of VGCF and 0.057g of SEBS to the silicon slurry, and stir it at 2000rpm for 30 minutes to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to obtain a pure nano-silicon negative electrode.

[0111] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0112] Comparative Example 2

[0113] Negative electrode preparation: Weigh 1.90g of nano-silicon powder (50-70nm), add it to 12mL of xylene, transfer it to a planetary ball mill, and mix for 8 hours at 250rpm to obtain a silicon slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon slurry, and stir it at 2200rpm for 50 minutes to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to obtain a pure nano-silicon negative electrode.

[0114] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0115] Comparative Example 3

[0116] Negative electrode preparation: Weigh 1.80g of silicon-carbon material (5-8μm), add it to 12mL of xylene, transfer it to a planetary ball mill, and mix for 8 hours at 250rpm to obtain a silicon-carbon slurry; add 0.086g of VGCF and 0.057g of SEBS to the silicon-magnesium mixed slurry, and stir at 2000rpm for 30 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 45μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0117] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0118] Comparative Example 4

[0119] Negative electrode preparation: Weigh 1.50g of silicon-carbon material (1-3μm), add it to 12mL of xylene, transfer it to a planetary ball mill, and mix at 250rpm for 2 hours to obtain a silicon-carbon slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-carbon slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 45μm; vacuum dry at 80℃ for 10 hours to obtain a pure silicon-carbon negative electrode.

[0120] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0121] Comparative Example 5

[0122] Negative electrode preparation: Weigh 1.50g of nano-silicon powder (50-70nm) and 0.692g of magnesium powder (30μm), add them to 12mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0123] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0124] Comparative Example 6

[0125] Negative electrode preparation: Weigh 1.50g of nano-silicon powder (50-70nm) and 0.3g of magnesium nitride (10μm), add them to 12mL of xylene, transfer them to a planetary ball mill, and mix at 250rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088g of VGCF and 0.058g of SEBS to the silicon-magnesium mixed slurry, and stir at 2200rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0126] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0127] Comparative Example 7

[0128] Negative electrode preparation: Weigh 1.40g of micron-sized silicon powder (2-3μm), add it to 100mL of xylene, transfer it to a planetary ball mill, and mix for 8 hours at 250rpm to obtain a silicon-magnesium mixed slurry; add 0.076g of VGCF and 0.051g of SEBS to the silicon-magnesium mixed slurry, and stir it at 2000rpm for 30 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10μm thick), controlling the coating thickness to 30μm; vacuum dry at 80℃ for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0129] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0130] Comparative Example 8

[0131] Negative electrode preparation: Weigh 0.4 nm silicon powder (50-70 nm), 0.923 g magnesium powder (30 μm), and 0.4 g magnesium nitride (10 μm), add them to 12 mL xylene, transfer to a planetary ball mill, and mix at 250 rpm for 8 hours to obtain a silicon-magnesium mixed slurry; add 0.088 g VGCF and 0.058 g SEBS to the silicon-magnesium mixed slurry, and stir at 2200 rpm for 50 minutes using a homogenizer to form a uniform slurry; coat it onto a copper current collector (10 μm thick), controlling the coating thickness to 30 μm; vacuum dry at 80 °C for 10 hours to remove xylene, and obtain a silicon-based composite negative electrode.

[0132] Battery fabrication: The obtained negative electrode sheet was cut and placed on one side of the solid-state lithium-ion battery casing. Sulfide solid electrolyte powder (specifically Li6PS5Cl) was poured in and spread evenly, followed by a layer with an surface capacity of approximately 3 mAh / cm². 2 The positive electrode is used as the counter electrode and is pressed into a sheet using a pressure of 400MPa to make an all-solid-state lithium-ion battery with an N / P ratio of 0.6.

[0133] Battery test

[0134] The test pressure was 50 MPa, and the charge / discharge cutoff voltage during the test was 4.3-1.5 V. The current density used for different charge / discharge rates was 0.1C = 0.3 mA / cm². 2 (Based on the positive electrode surface capacity contained in a solid-state lithium-ion battery), the following tests were conducted:

[0135] (1) Cyclic performance test at room temperature: first, charge and discharge at a constant current of 0.1C once, and then charge and discharge cycle at a constant current of 0.5C;

[0136] (2) Rate performance test at room temperature: First, constant current charge and discharge at 0.1C, then constant current charge and discharge at 0.2C, 0.5C, 0.8C, 1C and 0.1C in sequence.

[0137] The measured energy density of the battery (based on the mass of the positive and negative electrodes), the maximum rate at which no micro-short circuit occurs, the capacity retention rate after 100 cycles at 0.5C, and the capacity retention rate at 0.5C are shown in Table 1 below.

[0138] Table 1: Battery performance test data for the examples and comparative examples

[0139]

[0140] Performance data for Comparative Examples 1-4 and 6-8 were not obtained because micro-short circuits occurred at lower rates.

[0141] By comparing Examples 1-7 and Comparative Examples 1-8 (especially Examples 1 and 2 compared to Comparative Examples 1 and 2, Examples 3 compared to Comparative Example 7, and Examples 4 and 5 compared to Comparative Examples 3 and 4), it can be seen that the silicon-based composite anode material for all-solid-state lithium batteries of the present invention improves the electrochemical performance and cycle stability of the battery by incorporating metallic magnesium and magnesium nitride and their specific composition into the silicon-based anode.

[0142] By comparing Example 2 and Comparative Examples 5 and 6, it can be seen that the silicon-based composite anode material for all-solid-state lithium batteries containing metallic magnesium and magnesium nitride of the present invention achieves improved electrochemical performance and cycle stability compared with silicon-based composite anode materials containing only magnesium or magnesium nitride, demonstrating the synergistic effect of magnesium and magnesium nitride in the silicon-based composite anode material of the present invention.

[0143] By comparing Examples 1 and 2 with Comparative Example 8, it can be seen that the silicon-based composite anode material for all-solid-state lithium batteries of the present invention improves the electrochemical performance and cycle stability of the battery through its specific composition.

[0144] By comparing Examples 1-5 with Examples 6 and 7 (especially Example 2 compared with Examples 6 and 7), it can be seen that the all-solid-state lithium battery of the present invention further improves the electrochemical performance and cycle stability of the battery through a specific N / P ratio.

[0145] Comparative Examples 1-3 and 4 and 5 show that using materials with smaller particle sizes (such as 50-70nm nano-silicon powder, 30-50μm magnesium powder, and 1-3μm silicon-carbon materials) in the silicon-based composite anode material for all-solid-state lithium batteries of the present invention is beneficial to further improve the electrochemical performance and cycle stability of the battery.

[0146] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A silicon-based composite anode material for all-solid-state lithium batteries, characterized in that, It contains the following components: A silicon matrix comprising 55%-90% by mass, including silicon powder or silicon-carbon materials; Magnesium dopants with a mass fraction of 5%-40%, including magnesium powder and magnesium nitride; Auxiliary components, including conductive agents and binders, are present in a mass fraction of 3%-8%.

2. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 1, characterized in that, The silicon powder is nano-silicon powder with a particle size of 50-100nm and / or micro-silicon powder with a particle size of 1-3µm.

3. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 1, characterized in that, The particle size of the silicon-carbon material is 1-10µm.

4. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 1, characterized in that, The magnesium powder has a particle size of 30-500 μm.

5. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 4, characterized in that, The magnesium nitride has a particle size of 1-10µm.

6. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 1, characterized in that, The conductive agent includes vapor-grown carbon fiber (VGCF).

7. The silicon-based composite anode material for all-solid-state lithium batteries according to claim 1, characterized in that, The adhesive includes styrene-ethylene-butadiene copolymer (SEBS).

8. A method for preparing the silicon-based composite anode material for all-solid-state lithium batteries according to any one of claims 1-7, characterized in that, Includes the following steps: 1) The silicon substrate material is ball-milled to obtain a pretreated silicon substrate; 2) The pretreated silicon substrate, the magnesium powder, and the magnesium nitride are added to an organic solvent and mixed to obtain a mixed slurry; 3) Mix the slurry with the conductive agent and the adhesive and dry it.

9. A negative electrode for an all-solid-state lithium battery, characterized in that, The negative electrode comprises the silicon-based composite negative electrode material for all-solid-state lithium batteries according to any one of claims 1-7.

10. An all-solid-state lithium battery, characterized in that, The all-solid-state lithium battery includes the negative electrode for an all-solid-state lithium battery as described in claim 9.

11. The all-solid-state lithium battery according to claim 10, characterized in that, The N / P ratio of the negative electrode to the positive electrode of the all-solid-state lithium battery is >0 and ≤0.6.

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