Composite silicon-carbon negative electrode and preparation method and application thereof

Abstract

The invention provides a composite silicon-carbon negative electrode and a preparation method and application thereof, and relates to the technical field of all-solid-state lithium ion batteries, the composite silicon-carbon negative electrode comprises: a silicon-carbon negative electrode matrix; the plurality of independent lithium-loving metal nanoparticles are arranged on the surface of the silicon-carbon negative electrode substrate; and the tough interface layer covers the surface of the silicon-carbon negative electrode substrate provided with the lithium-loving metal nanoparticles. The core of the invention is to provide a substrate modification-interface packaging composite structure, firstly, a discontinuous lithium-loving metal nano island array is created on a silicon carbon negative electrode substrate, and then, a complete tough interface layer is used for packaging and covering the discontinuous lithium-loving metal nano island array. According to the all-solid-state battery, the electrochemical performance of the all-solid-state battery can be effectively improved through the collaborative design of the discontinuous nano island and the tough packaging layer.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium-ion battery technology, and in particular to a composite silicon-carbon anode, its preparation method, and its application. Background Technology

[0002] In all-solid-state lithium-ion batteries, the interfacial compatibility between the sulfide electrolyte and the silicon-carbon anode is a core challenge restricting their practical application. Although sulfide solid electrolytes possess high ionic conductivity (up to 10⁻⁶ at room temperature),… -2 While lithium density is on the order of S / cm, its inherent brittleness makes it difficult to withstand the enormous volume changes that silicon undergoes during charging and discharging. This leads to interfacial contact degradation, exacerbated side reactions, and uncontrolled lithium dendrite growth, all of which contribute to a sharp drop in battery cycle life and increased safety risks. Currently, rigid oxide coatings are often used to improve the uniformity of lithium deposition, but their high modulus makes them prone to cracking and peeling under silicon expansion, thus becoming dendrite penetration channels. In addition, research on lithiophilic layers for lithium nucleation regulation mainly focuses on liquid systems. Their designs do not consider the stringent requirements for interfacial structural integrity caused by repeated expansion and contraction of silicon in the solid state. If these layers are directly transferred to sulfide systems, the lithiophilic layer may crack and peel off during silicon expansion, losing its function. Summary of the Invention

[0003] One of the objectives of this invention is to provide a composite silicon-carbon anode to at least solve one of the technical problems existing in the prior art.

[0004] The second objective of this invention is to provide a method for preparing a composite silicon-carbon anode.

[0005] The third objective of this invention is to provide a composite silicon-carbon anode or a composite silicon-carbon anode prepared by the aforementioned method for use in the preparation of lithium-ion batteries.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a composite silicon-carbon anode, comprising: Silicon-carbon anode substrate; Multiple independent lithium-friendly metal nanoparticles are disposed on the surface of the silicon-carbon anode substrate; A tough interface layer is applied to the surface of a silicon-carbon anode substrate containing lithium-loving metal nanoparticles.

[0007] Furthermore, the average particle size of the lithium-loving metal nanoparticles is 5-15 nm; Preferably, the material of the lithium-loving metal nanoparticles is selected from one or more of silver, zinc, magnesium, antimony and gold, or from an alloy containing at least one of silver, zinc, magnesium, antimony and gold. Furthermore, the thickness of the tough interface layer is 0.5-20 μm; Preferably, the raw materials for preparing the tough interface layer include a polymer matrix and a lithium salt; Preferably, the polymer matrix comprises one or more of polyethylene oxide, polypropylene carbonate, and polyacrylonitrile; Preferably, the lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium bis(oxalateborate).

[0008] Secondly, the present invention provides a method for preparing a composite silicon-carbon anode, comprising: (a) Multiple lithium-loving metal nanoparticles are prepared on the surface of a silicon-carbon anode substrate; (b) A tough interface layer is prepared on the surface of a silicon-carbon anode substrate containing lithium-loving metal nanoparticles.

[0009] Furthermore, in step (a), the lithium-loving metal nanoparticles are prepared using physical vapor deposition.

[0010] Furthermore, the physical vapor deposition method includes magnetron sputtering or vacuum evaporation. Preferably, the sputtering power of the magnetron sputtering method is 10-40 W and the sputtering time is 10-50 s.

[0011] Furthermore, the preparation process of the tough interface layer includes: (A) Dissolve the polymer matrix, lithium salt, and optional filler in a solvent to form a slurry; (B) The slurry is applied to the surface of the silicon-carbon anode substrate containing lithium-philic metal nanoparticles and then dried to obtain the tough interface layer. Preferably, the mass ratio of the polymer matrix to the lithium salt is 1:0.2-1.0; Preferably, the solvent includes one or more of acetonitrile, N-methylpyrrolidone, dimethylformamide, and tetrahydrofuran; Preferably, the application method includes one of the following: blade coating, spray coating, roller coating, and dip coating.

[0012] Furthermore, the filler includes one or more of LLZO, Al2O3, plastic crystals, and silica nanoparticles; Preferably, the amount of the filler is 0.2-0.5:1.

[0013] Furthermore, the drying temperature is 55-100℃, and the drying time is 4-15 hours.

[0014] Thirdly, the present invention provides an application of a composite silicon-carbon anode or a composite silicon-carbon anode prepared by the aforementioned preparation method in the preparation of lithium-ion batteries.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The composite silicon-carbon anode provided by this invention comprises multiple independent lithium-loving metal nanoparticles disposed on the surface of a silicon-carbon anode substrate, and a tough interface layer completely covering the exposed areas of the nanoparticles and the silicon-carbon anode substrate. This constructs a three-level synergistic structure of silicon-carbon substrate, lithium-loving nanoparticles, and a tough encapsulation layer. The lithium-loving nanoparticles serve as highly active nucleation sites, guiding the uniform deposition of lithium ions from the source and inhibiting dendrite initiation. Specifically, the multiple lithium-loving metal nanoparticles are isolated from each other and do not connect to each other, preventing the formation of continuous conductive pathways and avoiding them becoming channels for preferential growth of lithium dendrites. At the same time, it ensures that each particle serves as a discrete, highly active nucleation site, achieving spatial homogenization of lithium deposition and a significant reduction in overpotential. The tough interface layer buffers the volume expansion stress during silicon-carbon cycling to adapt to all-solid-state battery applications where there is direct contact with sulfide solid electrolytes. Furthermore, it physically isolates the composite surface of the silicon-carbon anode substrate and the lithium-loving metal nanoparticles from direct contact with the electrolyte, significantly reducing interfacial side reactions and thus effectively improving the electrochemical performance of all-solid-state batteries. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the composite silicon-carbon anode provided in an embodiment of the present invention. Detailed Implementation

[0018] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, the first aspect of the present invention provides a composite silicon-carbon anode, comprising: a silicon-carbon anode substrate; a plurality of isolated and unconnected lithium-loving metal nanoparticles disposed on the surface of the silicon-carbon anode substrate; and a tough interface layer covering the lithium-loving metal nanoparticles and the surface areas of the silicon-carbon anode substrate not covered by the lithium-loving metal nanoparticles.

[0021] This invention provides a composite silicon-carbon anode suitable for all-solid-state batteries using sulfide as the solid electrolyte, aiming to balance uniform lithium-ion deposition with long-term interfacial stability. The anode comprises a silicon-carbon anode substrate, multiple isolated and unconnected lithium-philic metal nanoparticles, and a tough interfacial layer. The lithium-philic metal nanoparticles are directly formed on the surface of the silicon-carbon anode substrate, exhibiting a discrete distribution without physical connections, forming a discontinuous array of lithium-philic metal nanoislands. This array pre-sets uniform lithium nucleation sites on the silicon-carbon anode surface, thereby reducing lithium nucleation overpotential, guiding uniform lithium-ion deposition, and inhibiting lithium dendrite initiation. The tough interfacial layer covers all lithium-philic metal nanoparticles and the uncovered surface areas of the silicon-carbon anode substrate, forming a complete encapsulation of the nanoparticles and substrate. This not only buffers the stress generated by the volume expansion of the silicon-carbon anode to protect the sulfide solid electrolyte, but also physically isolates the silicon-carbon anode substrate from the electrolyte, reducing side reactions. Furthermore, the complete coverage anchors the nanoparticle structure, ensuring long-term interfacial stability.

[0022] To further explain, the composite silicon-carbon anode provided by this invention has a composite structure of silicon-carbon anode matrix-nano-island-tough interface layer. The lithium-loving nano-islands that are in direct contact with the silicon-carbon anode matrix serve as preset, energy-priority nucleation sites, effectively guiding lithium ions to nucleate uniformly at their locations. This avoids random lithium deposition at defects on the surface of the silicon-carbon anode matrix, thus suppressing lithium dendrites at the source. On the other hand, the significant lithium-loving nano-island array essentially creates a low-energy barrier, high-reaction-rate, and highly spatially uniform interface for the lithium deposition / dissolution reaction, reducing the lithium nucleation overpotential and improving the reaction kinetics of lithium deposition / dissolution. This results in the battery having better rate performance and fast charging capability. The tough interface layer ensures efficient and smooth passage of lithium ions through the interface. Its polymer matrix molecular chains undergo reversible elastic deformation through stretching, bending, and entanglement, effectively absorbing, dispersing, and buffering the stress generated by the volume expansion of the silicon-carbon anode. This protects the brittle sulfide solid electrolyte on the outside, preventing mechanical damage caused by repeated expansion and contraction during charging and discharging, maintaining the physical integrity of the interface, and ensuring the long-term cycle stability of the battery. Therefore, the tough interface layer acts as a buffer, absorbing the stress generated by volume expansion and protecting the outer sulfide electrolyte. On the other hand, it acts as an isolation layer, physically blocking direct contact between the silicon-carbon anode substrate / nano-islands and the electrolyte, reducing side reactions, and effectively solving the mechanical failure problem of the lithiophilic layer under silicon volume expansion. The discontinuous island structure avoids stress concentration, while the tough interface layer absorbs stress through its viscoelastic deformation and anchors the nano-islands to the silicon-carbon anode substrate, preventing them from detaching or agglomerating during cycling, thus ensuring the long-term stability of the modification effect. The core of this invention lies in providing a composite structure of substrate modification and interface encapsulation, which first creates a discontinuous array of lithium-loving metal nanoislands on a silicon-carbon anode substrate, and then encapsulates and covers them with a complete tough interface layer.

[0023] In this invention, the synergistic design of discontinuous nano-islands and a tough encapsulation layer can effectively improve the electrochemical performance of all-solid-state batteries.

[0024] In some preferred embodiments, the average particle size of the lithium-loving metal nanoparticles is 5-15 nm, for example, 5 nm, 10 nm, 15 nm, etc. If the particle size is too small (e.g., <5 nm), the surface energy of the nanoparticles is too high, and they are prone to agglomeration during subsequent coating or cycling, resulting in a decrease in the density of nucleation sites and uneven distribution. If the particle size is too large (e.g., >15 nm), the coverage area of ​​a single particle increases, which weakens the stress dispersion advantage brought about by discontinuity, and may penetrate the tough interface layer to form a local conductive path, inducing dendrite preferential nucleation. An average particle size of 5-15 nm can ensure a sufficiently high specific surface area to provide dense and uniform nucleation sites, and can also be fully wrapped and anchored by the tough interface layer to maintain its spatial stability during the expansion and contraction of silicon volume.

[0025] Preferably, the material of the lithiophilic metal nanoparticles is selected from one or more of silver, zinc, magnesium, antimony, and gold, or from an alloy containing at least one of silver, zinc, magnesium, antimony, and gold. Firstly, the process of the aforementioned metals or alloys forming an alloy with lithium is an exothermic reaction (Gibbs free energy change ΔG < 0). This means that lithium atoms are in a lower energy state on or inside these metal surfaces than on the silicon-carbon anode surface. Therefore, lithium ions tend to aggregate at these sites before reduction, thereby reducing the additional energy required for nucleation (overpotential); moreover, on the silicon-carbon anode surface, lithium needs to overcome an extremely high energy barrier to form its own lattice (homogeneous nucleation). The lattice constants and surface electronic structures of these lithiophilic metals match those of lithium or lithium alloys, serving as readily available templates for direct lithium growth on their surfaces (heterogeneous nucleation), significantly reducing the energy barrier and greatly minimizing the risk of uncontrolled lithium dendrite growth.

[0026] In some preferred embodiments, the thickness of the tough interface layer is 0.5-20 μm, for example, it can be 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, etc. If the tough interface layer is too thin (e.g., <0.5 μm), a continuous and dense film cannot be formed, making it difficult to achieve complete encapsulation of nanoparticles and effective stress buffering; if it is too thick (e.g., >20 μm), it will increase interfacial impedance and reduce lithium-ion migration rate. The thickness of the tough interface layer is further preferably 3-10 μm.

[0027] Understandably, the thickness and modulus of the toughness interface layer can be optimized and adjusted according to the silicon content and the battery operating pressure.

[0028] In some preferred embodiments, the raw materials for preparing the tough interface layer include a polymer matrix and a lithium salt. More preferably, the polymer matrix includes one or more of polyethylene oxide (PEO), polypropylene carbonate (PPC), and polyacrylonitrile (PAN). The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalateborate (LiDFOB), and lithium bis(oxalateborate)borate (LiBOB).

[0029] Specifically, the tough interface layer is a viscoelastic lithium-ion conductive polymer composite material. The polymer matrix provides a viscoelastic framework and mechanical buffering capacity, while the lithium salt provides charge carriers (Li... + ), its anions (such as TFSI) - FSI -It can also regulate the chain segment mobility and interfacial wettability by interacting with the polar groups of polymers, thereby affecting the interfacial bonding strength with silicon-carbon matrix and nanoparticles, as well as the chemical stability against electrolyte erosion during long-term cycling.

[0030] A second aspect of this invention provides a method for preparing a composite silicon-carbon anode, comprising: (a) Physical vapor deposition is preferably used on the surface of silicon-carbon anode substrate to directly deposit lithium-loving metal. By controlling the deposition process parameters, a discontinuous array of lithium-loving metal nano-islands is formed to obtain silicon-carbon material with lithium-loving metal nano-island array composite. (b) A slurry for preparing a tough interface layer is coated on a silicon-carbon anode substrate with a nano-island array deposited on it. After drying, a tough interface layer with complete coverage is formed, and the final sulfide all-solid-state battery anode material is obtained.

[0031] The preparation method provided by this invention employs a step-by-step controllable process. First, a discontinuous array of lithium-loving metal nanoparticles is prepared on a silicon-carbon substrate. Then, through slurry coating and drying, the tough interfacial layer precursor slurry fully penetrates into the gaps between the lithium-loving metal nanoparticles, completely encapsulating each nanoparticle. After drying, a continuous and dense encapsulation structure is formed. This structure not only prevents unconstrained lithium-loving metal nanoparticles from detaching or agglomerating during long-term cycling, but also avoids direct exposure of the lithium-loving metal nanoparticles to the sulfide solid electrolyte, thereby suppressing interfacial side reactions between the two and ensuring the continuous effectiveness of nucleation function. Ultimately, this results in a long-life, highly safe, and fast-charge compatible all-solid-state sulfide battery.

[0032] In some preferred embodiments, the physical vapor deposition method includes magnetron sputtering or vacuum evaporation.

[0033] Preferably, when the physical vapor deposition method is magnetron sputtering, the sputtering power is 10-40 W, for example, 10 W, 20 W, 30 W, 40 W, etc., and the sputtering time is 10-50 s, for example, 10 s, 20 s, 30 s, 40 s, 50 s, etc.

[0034] Preferably, when the physical vapor deposition method is vacuum evaporation, the reading of the evaporation thickness monitor is 0.5-1.0 nm, for example, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1.0 nm, etc. It should be noted that this thickness reading refers to the thickness of the plate assuming the deposited metal is uniformly spread into a continuous plate. The size of the nanoislands is proportional to this thickness, and the spacing between the nanoislands is also proportional to this thickness.

[0035] In some preferred embodiments, the preparation process of the tough interface layer includes: (A) Dissolve the polymer matrix, lithium salt, and optional filler in a solvent to form a slurry; (B) The slurry is applied to the surface of the silicon-carbon anode substrate containing lithium-philic metal nanoparticles and then dried to obtain the tough interface layer.

[0036] Preferably, the mass ratio of the polymer matrix to the lithium salt is 1:0.2-1.0, for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, etc.

[0037] Preferably, the solvent includes one or more of acetonitrile, N-methylpyrrolidone, dimethylformamide, and tetrahydrofuran.

[0038] Preferably, the application method includes one of the following: blade coating, spray coating, roller coating, and dip coating.

[0039] In some preferred embodiments, the filler includes one or more of LLZO, Al2O3, plastic crystals, and silica nanoparticles.

[0040] Preferably, the mass ratio of the filler to the lithium salt is 0.2-0.5:1.

[0041] In some preferred embodiments, the drying temperature is 55-100°C; the drying time is 4-15 hours.

[0042] The third aspect of the present invention provides an application of a composite silicon-carbon anode or a composite silicon-carbon anode prepared by the above preparation method in the preparation of lithium-ion batteries.

[0043] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0044] Example 1 This embodiment provides a composite silicon-carbon anode, the preparation process of which is as follows: Step 1: Place the silicon-carbon composite material (silicon-carbon mass ratio 1:9) in the vacuum chamber of the magnetron sputtering instrument; Step 2: Using high-purity silver (Ag) with a purity of not less than 99.9% as the target material, sputtering is performed under an argon atmosphere. By controlling the sputtering power to be 25W and the sputtering time to be 20 seconds, a discontinuous array of silver nanoislands with an average particle size of about 10 nm is formed on the surface of the silicon-carbon anode. Step 3: Weigh 0.5g of polyethylene oxide (PEO, Mv=600,000) and 0.25g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and dissolve them in 10mL of acetonitrile solvent, stirring until completely dissolved.

[0045] Step 4: Apply the above solution to the surface of the silicon-carbon anode modified with silver nano-islands using a scraping method.

[0046] Step 5: Dry in a vacuum oven at 60℃ for 12 hours to form a tough interface layer with a thickness of about 5μm that is fully encapsulated, thus obtaining a composite silicon-carbon anode.

[0047] Example 2 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that the target material in step 2 is Zn.

[0048] Example 3 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that the target material in step 2 is Mg.

[0049] Example 4 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: in step 3, 0.5g of polypropylene carbonate (PPC, Mv=50000) and 0.25g of lithium bis(fluorosulfonyl)imide (LiFSI) are weighed and dissolved in 10mL of acetonitrile solvent.

[0050] Example 5 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: by controlling the sputtering power to be 10W and the sputtering time to be 20 seconds, a discontinuous array of silver nano-islands with an average particle size of about 5nm is formed on the surface of the silicon-carbon anode.

[0051] Example 6 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: by controlling the sputtering power to be 40W and the sputtering time to be 20 seconds, a discontinuous array of silver nanoislands with an average particle size of about 15nm is formed on the surface of the silicon-carbon anode.

[0052] Example 7 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: in step 3, 0.25g of polyethylene oxide (PEO, Mv=600,000) and 0.125g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are weighed and dissolved in 10mL of acetonitrile solvent to form a tough interface layer with a thickness of about 3 μm that is fully encapsulated.

[0053] Example 8 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: in step 3, 0.75g of polyethylene oxide (PEO, Mv=600,000) and 0.375g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are weighed and dissolved in 10mL of acetonitrile solvent to form a tough interface layer with a thickness of about 10 μm that is fully encapsulated.

[0054] Example 9 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: by controlling the sputtering power to be 5W and the sputtering time to be 20 seconds, a discontinuous array of gold nanoislands with an average particle size of approximately 3 nm is formed on the surface of the silicon-carbon anode. Example 10 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that: by controlling the sputtering power to be 50W and the sputtering time to be 20 seconds, a discontinuous array of silver nanoislands with an average particle size of about 18 nm is formed on the surface of the silicon-carbon anode.

[0055] Example 11 This embodiment provides a composite silicon-carbon anode, which differs from Embodiment 1 in that 0.05g of silicon dioxide nanoparticles are added in step 3.

[0056] Example 12 This embodiment provides a composite silicon-carbon anode, the preparation process of which is as follows: Step 1: Using thermal evaporation, place the silicon-carbon anode substrate (silicon-carbon mass ratio 1:9) on an evaporation table and evaporate under high vacuum (<5×10⁻⁶). -4 The silver wire is heated to evaporate by Pa, and the evaporation thickness is monitored by a monitor until the reading is 0.8 nm (nominal thickness). At this point, silver is deposited on the silicon-carbon surface in the form of nano-islands.

[0057] Step 2: Weigh 0.4g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), 0.3g of LiTFSI and 0.3g of silica nanoparticles and dissolve them in 10mL of N-methylpyrrolidone (NMP), and stir until homogeneous.

[0058] Step 3: Apply the modified silver nano-islands onto the surface of the silicon-carbon anode substrate using a spray coating method.

[0059] Step 4: After drying at 80℃, transfer to a vacuum oven at 100℃ for 4 hours to form a tough interface layer with a thickness of about 8μm, thus obtaining a composite silicon-carbon anode.

[0060] Comparative Example 1 This comparative example provides a composite silicon-carbon anode, which differs from Example 1 in that it does not prepare a tough interface layer.

[0061] Comparative Example 2 This comparative example provides a composite silicon-carbon anode, which differs from Example 1 in that it does not deposit silver nano-islands.

[0062] Comparative Example 3 This comparative example provides a composite silicon-carbon anode, which differs from Example 1 in that a polyvinylidene fluoride (PVDF) layer is used instead of the tough interface layer.

[0063] Test case Test samples: The composite silicon-carbon anodes prepared in Examples 1-12 and Comparative Examples 1-3 were used as samples for testing.

[0064] Test method: Initial coulombic efficiency test: At room temperature, the prepared negative electrode material was assembled into a half-cell of an all-solid-state battery and charged and discharged at a rate of 0.1C. Initial coulombic efficiency = initial discharge capacity / initial charge capacity × 100%; Cyclic performance test: At room temperature, the prepared negative electrode material is assembled into a half-cell of an all-solid-state battery and charged and discharged at a rate of 0.5C for cycle performance test. The life is terminated when the capacity retention rate reaches 80%.

[0065] Rate performance testing: At room temperature, the prepared negative electrode material was assembled into a half-cell of an all-solid-state battery and its charge and discharge performance was tested at 0.1C, 0.3C, 0.5C, 1.0C, and 2.0C.

[0066] The test results are shown in Table 1.

[0067] Table 1

[0068] As can be seen from the data in Table 1, the overall electrochemical performance of all examples is better than that of the comparative examples. Among them, the comparative example 1 lacks a tough interface layer, which cannot buffer stress during the volume expansion of silicon and carbon, resulting in continuous deterioration of interface contact and aggravation of side reactions, ultimately leading to electrolyte rupture and lithium dendrite penetration. In the comparative example 2, without nucleation sites to guide it, lithium dendrites eventually caused a short circuit.

[0069] Examples 1-8 and Examples 11-12 use materials and parameters within the preferred range of the present invention, and exhibit balanced and stable performance. In Example 9, the nanoparticle size is too small, which leads to easy aggregation and inactivation of nucleation sites, weakening the nucleation guiding effect. In Example 10, the size is too large, which reduces the spatial dispersion of nano-islands, affects the stress buffering effect, and may aggravate uneven local lithium deposition.

[0070] This invention employs a dual-layer synergistic design of lithium-loving nanoisland-guided nucleation and a tough interfacial layer for buffer protection. Compared to a single-function protective layer, this method effectively overcomes the two core challenges of lithium dendrite growth and volume expansion faced by high-capacity silicon-carbon anodes in sulfide all-solid-state batteries, achieving comprehensive improvements in cycle life, rate performance, and interfacial stability. Superior electrochemical performance is observed when the average particle size of the lithium-loving nanoisland-guided nucleation is 10 nm, the polymer-to-lithium salt mass ratio in the tough interfacial layer is 2:1, and the coating thickness is 5 μm.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite silicon-carbon anode, characterized in that, include: Silicon-carbon anode substrate; Multiple independent lithium-friendly metal nanoparticles are disposed on the surface of the silicon-carbon anode substrate; A tough interface layer is applied to the surface of a silicon-carbon anode substrate containing lithium-loving metal nanoparticles.

2. The composite silicon-carbon anode according to claim 1, characterized in that, The average particle size of the lithium-loving metal nanoparticles is 5-15 nm. Preferably, the material of the lithium-loving metal nanoparticles is selected from one or more of silver, zinc, magnesium, antimony and gold, or from an alloy containing at least one of silver, zinc, magnesium, antimony and gold.

3. The composite silicon-carbon anode according to claim 1, characterized in that, The thickness of the tough interface layer is 0.5-20 μm; Preferably, the raw materials for preparing the tough interface layer include a polymer matrix and a lithium salt; Preferably, the polymer matrix comprises one or more of polyethylene oxide, polypropylene carbonate, and polyacrylonitrile; Preferably, the lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium bis(oxalateborate).

4. The method for preparing the composite silicon-carbon anode according to any one of claims 1-3, characterized in that, include: (a) Multiple lithium-loving metal nanoparticles are prepared on the surface of a silicon-carbon anode substrate; (b) A tough interface layer is prepared on the surface of a silicon-carbon anode substrate containing lithium-loving metal nanoparticles.

5. The preparation method according to claim 4, characterized in that, In step (a), the lithium-loving metal nanoparticles are prepared by physical vapor deposition.

6. The preparation method according to claim 5, characterized in that, The physical vapor deposition method includes magnetron sputtering or vacuum evaporation. Preferably, the sputtering power of the magnetron sputtering method is 10-40 W and the sputtering time is 10-50 s.

7. The preparation method according to claim 4, characterized in that, The preparation process of the tough interface layer includes: (A) Dissolve the polymer matrix, lithium salt, and optional filler in a solvent to form a slurry; (B) The slurry is applied to the surface of the silicon-carbon anode substrate containing lithium-philic metal nanoparticles and then dried to obtain the tough interface layer. Preferably, the mass ratio of the polymer matrix to the lithium salt is 1:0.2-1.0; Preferably, the solvent includes one or more of acetonitrile, N-methylpyrrolidone, dimethylformamide, and tetrahydrofuran; Preferably, the application method includes one of the following: blade coating, spray coating, roller coating, and dip coating.

8. The preparation method according to claim 7, characterized in that, The filler includes one or more of LLZO, Al2O3, plastic crystals, and silica nanoparticles; Preferably, the amount of the filler is 0.2-0.5:

1.

9. The preparation method according to claim 7, characterized in that, The drying temperature is 55-100℃, and the drying time is 4-15 hours.

10. The application of the composite silicon-carbon anode as described in any one of claims 1-3 or the composite silicon-carbon anode prepared by the preparation method described in any one of claims 4-9 in the preparation of lithium-ion batteries.

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