Artificial interface layer for silicon-carbon negative electrode of all-solid-state lithium battery as well as preparation method and application of artificial interface layer

Abstract

The invention provides an artificial interface layer for a silicon-carbon negative electrode of an all-solid-state lithium battery as well as a preparation method and application of the artificial interface layer. And the artificial interface layer is made of a nest type hydroborate material. The artificial interface layer provided by the invention has mechanical flexibility and chemical stability, can adapt to the huge volume change of silicon, maintains the integrity of interface contact, can improve the transmission rate of lithium ions between a negative electrode and a solid electrolyte, and reduces the interface impedance and side reaction. In addition, the artificial interface layer is adaptive to various solid-state electrolytes, so that the constructed all-solid-state lithium battery shows excellent cycle and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to an artificial interface layer for silicon-carbon anodes in all-solid-state lithium batteries, its preparation method, and its application. Background Technology

[0002] All-solid-state lithium batteries use non-flammable solid electrolytes instead of organic liquid electrolytes, and are considered a next-generation technology that fundamentally solves battery safety issues and improves energy density. Silicon-carbon composite materials, due to their extremely high theoretical specific capacity, are an ideal anode choice for achieving the high energy density target of all-solid-state batteries.

[0003] However, the application of silicon-carbon anodes in all-solid-state battery systems faces more severe challenges: 1. Significant volume change: The volume effect of silicon exceeding 300% persists during alloying / dealloying, leading to physical separation between the active material and the solid electrolyte, resulting in significant interfacial impedance. 2. Poor solid-solid interface contact: Rigid solid-solid interfaces have limited ion transport channels and high contact stress, making them prone to cracking during cycling and exacerbating interfacial failure. 3. Chemical / electrochemical compatibility: Silicon-carbon materials exhibit chemical incompatibility with various solid electrolytes (such as sulfide electrolytes), and side reactions can lead to interfacial degradation and a surge in impedance.

[0004] Currently, strategies for improving solid-solid interfaces include introducing flexible buffer layers or constructing hybrid conductive interfaces. However, existing interface layer materials often fail to simultaneously meet the requirements of high ionic conductivity, excellent mechanical flexibility, and good chemical stability, and their fabrication processes are difficult to apply to complex anode surfaces to form nanoscale ultrathin and uniform coatings.

[0005] Therefore, developing a novel interface layer that can simultaneously address the volume effect of silicon-carbon anodes and the solid-solid interface contact problem is crucial for advancing the commercialization of all-solid-state batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an artificial interface layer for silicon-carbon anodes in all-solid-state lithium batteries, along with its preparation method and applications. This invention provides an artificial interface layer composed of a nested hydroborate material. This artificial interface layer possesses both excellent mechanical flexibility and chemical stability, effectively absorbing and releasing the enormous stress of the silicon-carbon anode during cycling, adapting to the volume changes of silicon, thereby maintaining the integrity of the physical contact with the solid electrolyte layer and significantly reducing interfacial impedance. Simultaneously, the inherent ultra-high ionic conductivity of the nested hydroborate material constructs a "highway" for lithium-ion transport between the anode and the solid electrolyte, significantly reducing the transport energy barrier at the solid-solid interface. Furthermore, this interface layer effectively isolates the silicon-carbon anode from direct contact with the solid electrolyte, suppressing harmful interfacial side reactions. Moreover, this artificial interface layer exhibits excellent versatility, adaptable to various solid electrolytes, and easy to integrate. All-solid-state lithium batteries constructed based on this interface layer demonstrate superior cycle life and rate performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The present invention provides an artificial interface layer for silicon-carbon anodes of all-solid-state lithium batteries, the artificial interface layer being composed of a nested hydroborate material.

[0009] This invention provides an artificial interface layer composed of a nested hydroborate material. This artificial interface layer possesses both excellent mechanical flexibility and chemical stability, effectively absorbing and releasing the enormous stress of the silicon-carbon anode during cycling, adapting to the volume changes of silicon, thereby maintaining the integrity of the physical contact with the solid electrolyte layer and significantly reducing interfacial impedance. Simultaneously, the inherent ultra-high ionic conductivity of the nested hydroborate material constructs a "highway" for lithium ion transport between the anode and the solid electrolyte, significantly reducing the transport energy barrier at the solid-solid interface. Furthermore, this interface layer effectively isolates the silicon-carbon anode from direct contact with the solid electrolyte, suppressing harmful interfacial side reactions. Moreover, this artificial interface layer exhibits excellent versatility, adaptable to various solid electrolytes, and easy to integrate. All-solid-state lithium batteries constructed based on this interface layer demonstrate superior cycle life and rate performance.

[0010] It should be noted that nested hydroborate materials are a class of cage-like clusters containing hydrogen, boron, and metal cations (such as lithium ions). In this invention, it specifically refers to borohydrides with a "nested" (nido-) geometric structure, whose general chemical formula can be represented as M. x B y H z Or M x B y X z(where M is a metal cation and X is a halogen or other substituent), its anionic part is composed of boron atoms forming an open polyhedral framework missing one vertex.

[0011] Preferably, the thickness of the artificial interface layer is 20-50nm, for example, it can be 20nm, 30nm, 40nm or 50nm.

[0012] In this invention, an artificial interface layer of a certain thickness can not only effectively block direct contact between silicon-carbon active materials and solid electrolytes and suppress harmful interfacial side reactions, but also provide sufficient mechanical integrity to buffer the volume stress of silicon during cycling without significantly increasing the overall impedance and volume of the battery.

[0013] Preferably, the nested hydroborate material includes any one or a combination of at least two of lithium chloride-closed-dodecoborane, lithium bromide-closed-dodecoborane, lithium undecylhydro-closed-dodecoborate, or lithium decahydro-closed-decaborate.

[0014] Preferably, the nested hydroborate material has an open boron cluster structure.

[0015] It should be noted that the open boron cluster structure refers to an incomplete polyhedral framework (such as an open bowl-shaped or nest-shaped structure) with missing vertices, which is composed of boron atoms through multicenter bonds; this structure forms an internal cavity and open channel rich in delocalized electrons and carrying a negative charge.

[0016] The nested hydroborate material used in this invention has an open boron cluster structure, which is beneficial for lithium ion exchange (Li₂O₃). + It provides a fast migration channel with a low energy barrier; its delocalized electron system can effectively shield Li + The strong interaction between the electrolyte and the framework enables ultra-high ion conductivity, approaching that of liquid electrolytes.

[0017] Preferably, the room temperature ionic conductivity of the artificial interface layer is ≥1×10⁻⁶. -3 S / cm, for example, could be 1×10 -3 S / cm, 2×10 -3 S / cm, 3×10 -3 S / cm, 4×10 -3 S / cm, 5×10 -3 S / cm or 6×10 -3 S / cm, etc.

[0018] The room temperature ionic conductivity of the artificial interface layer provided by this invention is ≥1×10⁻⁶. -3S / cm is beneficial for achieving uniform and rapid transport of lithium ions at the solid-solid interface, thereby significantly reducing the interface impedance of the battery, improving its rate performance, and fundamentally suppressing lithium dendrite growth or interface failure caused by uneven ion flow.

[0019] Preferably, the elastic modulus of the artificial interface layer is 0.5-5 GPa, for example, it can be 0.8 GPa, 1.2 GPa, 2.5 GPa, 3.5 GPa or 4.5 GPa.

[0020] Preferably, the fracture toughness of the artificial interface layer is ≥0.5 MPa·m. 0.5 For example, it could be 0.8 MPa·m 0.5 1.2 MPa·m 0.5 1.8 MPa·m 0.5 Or 2.5 MPa·m 0.5 wait.

[0021] The elastic modulus and fracture toughness of the artificial interface layer provided by this invention meet the above requirements, indicating that the artificial interface layer has excellent flexibility and can effectively absorb and release stress during the cycling process of silicon-carbon anode like a "buffer pad", maintain the integrity of physical contact with the solid electrolyte layer, and greatly reduce interface impedance.

[0022] In a second aspect, the present invention provides a method for preparing an artificial interface layer for a silicon-carbon anode in an all-solid-state lithium battery as described in the first aspect, the method comprising the following steps:

[0023] Provides silicon-carbon anode substrate.

[0024] Nested hydroborate material is deposited on the surface of the silicon-carbon anode substrate to obtain the artificial interface layer.

[0025] Preferably, the deposition method includes low-temperature vapor deposition, more preferably physical vapor deposition, and even more preferably thermal evaporation.

[0026] In this invention, a low-temperature vapor deposition method can be used to form a nanoscale ultrathin and uniform coating layer on the surface of a silicon-carbon anode, with almost no increase in the volume and weight of the battery, perfectly maintaining the high energy density advantage of all-solid-state batteries. Furthermore, the low-temperature vapor deposition process is compatible with the fabrication processes of all-solid-state batteries (such as multilayer stacking technology), making it easy to integrate and scale up production.

[0027] Preferably, the deposition process is carried out in a vacuum environment with a vacuum level of 1×10⁻⁶. -4 Pa-1×10 -2 Pa, for example, could be 1×10 -4 Pa, 5×10 -4 Pa, 1×10 -3Pa, 5×10 -3 Pa or 1×10 -2 Pa, etc.

[0028] Preferably, during the deposition process, the temperature of the silicon-carbon anode substrate is controlled at 25-80°C, for example, 25°C, 35°C, 55°C, 65°C, 75°C, or 80°C.

[0029] Preferably, in the thermal evaporation method, the evaporation source material includes any one or a combination of at least two of lithium chloride-closed-dodecoborane, lithium bromide-closed-dodecoborane, lithium undecylhydro-closed-dodecoborate, or lithium decahydro-closed-decaborate.

[0030] Preferably, in the thermal evaporation method, the evaporation rate of the evaporation source material is 0.1-2 Å / s, for example, it can be 0.2 Å / s, 0.5 Å / s, 1 Å / s, 1.5 Å / s or 2 Å / s, etc.

[0031] In this invention, controlling the evaporation rate of the evaporation source material within a suitable range is beneficial for precisely controlling the growth of the thin film at the molecular / atomic scale. A lower evaporation rate (e.g., <0.5 Å / s) facilitates the full migration of deposited particles on the substrate surface, forming a dense, uniform film that is firmly bonded to the substrate. Conversely, controlling the upper limit of the evaporation rate to within 2.0 Å / s prevents excessive internal stress, decreased crystal quality, or unexpected thermal decomposition of the material due to excessively rapid evaporation, thereby ensuring the reliability of the final artificial interface layer structure and performance.

[0032] Thirdly, the present invention provides a modified silicon-carbon anode for all-solid-state lithium batteries, the modified silicon-carbon anode comprising a silicon-carbon anode substrate and an artificial interface layer as described in the first aspect disposed on the surface of the silicon-carbon anode substrate.

[0033] It should be noted that this invention does not specifically limit the selection of the silicon-carbon anode substrate. It can be prepared in-house using conventional silicon-carbon composite materials and processes known in the art (such as spray drying, vapor deposition coating, etc.), or commercially available silicon-carbon anode sheets can be directly used. For the silicon-carbon composite material, the silicon phase content is preferably 5% to 50% by mass, more preferably 10% to 20%. Those skilled in the art can select a suitable silicon-carbon anode substrate within the aforementioned range according to the required battery capacity.

[0034] Preferably, the thickness ratio of the silicon-carbon anode substrate to the artificial interface layer is (1000-5000):1, for example, it can be 1000:1, 2000:1, 3000:1, 4000:1 or 5000:1, etc.

[0035] Preferably, the thickness of the silicon-carbon anode substrate is 50-200 μm, for example, it can be 50 μm, 60 μm, 100 μm, 150 μm or 200 μm.

[0036] In this invention, a suitable thickness ratio between the silicon-carbon anode substrate and the artificial interface layer can minimize the volume and mass proportion of inactive materials in the battery while ensuring that the artificial interface layer performs its interface modification and high-speed ion transport functions. This ultra-large thickness ratio (10) 3 The magnitude of the material directly reflects the "ultra-thin" characteristic of the artificial interface layer prepared in this invention, which is a key structural feature that enables it to be integrated into the all-solid-state battery system without sacrificing its inherent advantage of high energy density.

[0037] Fourthly, the present invention provides an all-solid-state lithium battery, the all-solid-state lithium battery comprising a positive electrode, a negative electrode and a solid electrolyte layer, wherein the negative electrode is the modified silicon-carbon negative electrode described in the third aspect.

[0038] In this process, the artificial interface layer of the modified silicon-carbon anode is in direct contact with the solid electrolyte layer.

[0039] Preferably, the solid electrolyte layer is a sulfide solid electrolyte layer or an oxide solid electrolyte layer. For example, the sulfide solid electrolyte layer may be LPSCl (Li6PS5Cl), Li3PS4, or Li... 10 GeP2S 12 (LGPS) or their derivatives and complexes, etc., the oxide solid electrolyte layer may be, for example, Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) or their dopants / modifiers, etc.

[0040] For example, the positive electrode can be a layered oxide (such as nickel-cobalt-manganese ternary material NCM, nickel-cobalt-aluminum ternary material NCA), a polyanionic compound (such as lithium iron phosphate LFP), or a lithium-rich manganese-based material, which can be combined with a solid electrolyte and a conductive agent to form a composite positive electrode sheet.

[0041] 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.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention provides an artificial interface layer composed of a nested hydroborate material. This artificial interface layer possesses both excellent mechanical flexibility and chemical stability, effectively absorbing and releasing the enormous stress of the silicon-carbon anode during cycling, adapting to the volume changes of silicon, thereby maintaining the integrity of the physical contact with the solid electrolyte layer and significantly reducing interfacial impedance. Simultaneously, the inherent ultra-high ionic conductivity of the nested hydroborate material constructs a "highway" for lithium ion transport between the anode and the solid electrolyte, significantly reducing the transport energy barrier at the solid-solid interface. Furthermore, this interface layer effectively isolates the silicon-carbon anode from direct contact with the solid electrolyte, suppressing harmful interfacial side reactions. Moreover, this artificial interface layer exhibits excellent versatility, adaptable to various solid electrolytes, and easy to integrate. All-solid-state lithium batteries constructed based on this interface layer demonstrate superior cycle life and rate performance. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating the fabrication process of the artificial interface layer provided in Example 1 of this invention. Detailed Implementation

[0045] 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.

[0046] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0047] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] Example 1

[0049] This embodiment provides an artificial interface layer for silicon-carbon anodes in all-solid-state lithium batteries. The artificial interface layer is composed of a nested hydroborate material. The thickness of the artificial interface layer is 30 nm. The nested hydroborate material is lithium chloride-closed-dodecorane, which has an open boron cluster structure.

[0050] This embodiment also provides a method for preparing the artificial interface layer, and its preparation process flow diagram is shown below. Figure 1 As shown, the preparation method includes the following steps:

[0051] (1) Provide a commercially available silicon-carbon composite anode sheet (silicon content of 15wt% and thickness of about 100μm) as the silicon-carbon anode substrate.

[0052] The silicon-carbon anode substrate is placed on the sample stage of a vacuum thermal evaporation coating equipment.

[0053] (2) Using chlorinated-closed-dodecorane lithium as the evaporation source material, the vacuum thermal evaporation coating equipment is evacuated to a vacuum level of 5×10⁻⁶ in the vacuum chamber. -4 Pa, and heat the sample stage to 50°C.

[0054] (3) Control the heating power of the evaporation source so that the evaporation source material is vaporized at an evaporation rate of 0.4 Å / s and deposited on the surface of the silicon-carbon anode substrate. Monitor the film thickness in real time using a quartz crystal film thickness gauge. Stop the deposition when the film thickness reaches 30 nm.

[0055] (4) Cool in a vacuum environment and then take out the sample to obtain the artificial interface layer.

[0056] This embodiment also provides a modified silicon-carbon anode for all-solid-state lithium batteries. The modified silicon-carbon anode includes a silicon-carbon anode substrate and an artificial interface layer as described above disposed on the surface of the silicon-carbon anode substrate.

[0057] The silicon-carbon anode substrate is the commercially available silicon-carbon composite anode sheet (with a silicon content of 15 wt%), and the thickness ratio of the silicon-carbon anode substrate to the artificial interface layer is 3333:1.

[0058] This embodiment also provides an all-solid-state lithium battery, which includes a positive electrode, a negative electrode and a solid electrolyte layer, wherein the negative electrode is a modified silicon-carbon negative electrode as described above.

[0059] The positive electrode is prepared by mixing nickel-cobalt-manganese ternary positive electrode material (NCM811), sulfide solid electrolyte (LPSCl), and conductive carbon black; the solid electrolyte layer is a sulfide solid electrolyte (LPSCl) layer.

[0060] The assembly method of the all-solid-state lithium battery is as follows: in a glove box under a nitrogen atmosphere, the all-solid-state lithium battery is assembled by stacking the cathode / solid electrolyte layer / modified silicon-carbon anode in the order of "positive electrode / solid electrolyte layer / modified silicon-carbon anode" under a pressure of 300 MPa using a uniaxial pressing method.

[0061] Example 2

[0062] This embodiment provides an artificial interface layer for silicon-carbon anodes in all-solid-state lithium batteries. The artificial interface layer is composed of a nested hydroborate material. The thickness of the artificial interface layer is 20 nm. The nested hydroborate material is brominated-closed-dodecorane lithium, which has an open boron cluster structure.

[0063] This embodiment also provides a method for preparing the artificial interface layer, the method comprising the following steps:

[0064] (1) Provide a commercially available silicon-carbon composite anode sheet (silicon content of 15wt% and thickness of about 100μm) as the silicon-carbon anode substrate.

[0065] The silicon-carbon anode substrate is placed on the sample stage of a vacuum thermal evaporation coating equipment.

[0066] (2) Using brominated-closed-dodecorane lithium as the evaporation source material, the vacuum thermal evaporation coating equipment was evacuated to a vacuum level of 5×10⁻⁶ in the vacuum chamber. -3 Pa, and heat the sample stage to 30°C.

[0067] (3) Control the heating power of the evaporation source so that the evaporation source material is vaporized at an evaporation rate of 0.2 Å / s and deposited on the surface of the silicon-carbon anode substrate. Monitor the film thickness in real time using a quartz crystal film thickness gauge. Stop the deposition when the film thickness reaches 20 nm.

[0068] (4) Cool in a vacuum environment and then take out the sample to obtain the artificial interface layer.

[0069] This embodiment also provides a modified silicon-carbon anode for all-solid-state lithium batteries. The modified silicon-carbon anode includes a silicon-carbon anode substrate and an artificial interface layer as described above disposed on the surface of the silicon-carbon anode substrate.

[0070] The silicon-carbon anode substrate is the commercially available silicon-carbon composite anode sheet (with a silicon content of 15 wt% and a thickness of approximately 100 μm), and the thickness ratio of the silicon-carbon anode substrate to the artificial interface layer is 5000:1.

[0071] This embodiment also provides an all-solid-state lithium battery, which includes a positive electrode, a negative electrode and a solid electrolyte layer, wherein the negative electrode is a modified silicon-carbon negative electrode as described above.

[0072] The positive electrode is prepared by mixing nickel-cobalt-manganese ternary positive electrode material (NCM811), sulfide solid electrolyte (LPSCl), and conductive carbon black; the solid electrolyte layer is a sulfide solid electrolyte (LPSCl) layer.

[0073] The assembly method of the all-solid-state lithium battery is as follows: in a glove box under a nitrogen atmosphere, the all-solid-state lithium battery is assembled by stacking the cathode / solid electrolyte layer / modified silicon-carbon anode in the order of "positive electrode / solid electrolyte layer / modified silicon-carbon anode" under a pressure of 300 MPa using a uniaxial pressing method.

[0074] Example 3

[0075] This embodiment provides an artificial interface layer for the silicon-carbon anode of an all-solid-state lithium battery. The artificial interface layer is composed of a nested hydroborate material; the thickness of the artificial interface layer is 50 nm; the nested hydroborate material is lithium decahydrogen-closed-decaborate (Li₂B₃). 10 H 10 It has an open boron cluster structure.

[0076] This embodiment also provides a method for preparing the artificial interface layer, the method comprising the following steps:

[0077] (1) Provide a commercially available silicon-carbon composite anode sheet (silicon content of 15wt% and thickness of about 100μm) as the silicon-carbon anode substrate.

[0078] The silicon-carbon anode substrate is placed on the sample stage of a vacuum thermal evaporation coating equipment.

[0079] (2) Using decahydrogen-closed-decaborate lithium as the evaporation source material, the vacuum thermal evaporation coating equipment is evacuated to a vacuum level of 1×10⁻⁶ in the vacuum chamber. -3 Pa, and heat the sample stage to 80°C.

[0080] (3) Control the heating power of the evaporation source so that the evaporation source material is vaporized at an evaporation rate of 0.6 Å / s and deposited on the surface of the silicon-carbon anode substrate. Monitor the film thickness in real time using a quartz crystal film thickness gauge. Stop the deposition when the film thickness reaches 50 nm.

[0081] (4) Cool in a vacuum environment and then take out the sample to obtain the artificial interface layer.

[0082] This embodiment also provides a modified silicon-carbon anode for all-solid-state lithium batteries. The modified silicon-carbon anode includes a silicon-carbon anode substrate and an artificial interface layer as described above disposed on the surface of the silicon-carbon anode substrate.

[0083] The silicon-carbon anode substrate is the commercially available silicon-carbon composite anode sheet (with a silicon content of 15 wt% and a thickness of approximately 100 μm), and the thickness ratio of the silicon-carbon anode substrate to the artificial interface layer is 2000:1.

[0084] This embodiment also provides an all-solid-state lithium battery, which includes a positive electrode, a negative electrode and a solid electrolyte layer, wherein the negative electrode is a modified silicon-carbon negative electrode as described above.

[0085] The positive electrode is prepared by mixing nickel-cobalt-manganese ternary positive electrode material (NCM811), sulfide solid electrolyte (LPSCl), and conductive carbon black; the solid electrolyte layer is a sulfide solid electrolyte (LPSCl) layer.

[0086] The assembly method of the all-solid-state lithium battery is as follows: in a glove box under a nitrogen atmosphere, the all-solid-state lithium battery is assembled by stacking the cathode / solid electrolyte layer / modified silicon-carbon anode in the order of "positive electrode / solid electrolyte layer / modified silicon-carbon anode" under a pressure of 300 MPa using a uniaxial pressing method.

[0087] Example 4

[0088] The difference between this embodiment and Embodiment 1 is that the solid electrolyte layer is replaced with an oxide solid electrolyte (LLZO) layer, and a liquid electrolyte (5µL / cm³) is added dropwise between the oxide solid electrolyte (LLZO) layer and the modified silicon-carbon anode. 2 The liquid electrolyte is prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC:DEC volume ratio = 1:1), and the concentration of LiPF6 is 1 mol / L.

[0089] The remaining preparation methods and parameters are consistent with those in Example 1.

[0090] Example 5

[0091] The difference between this embodiment and Embodiment 1 is that the thickness of the artificial interface layer in the modified silicon-carbon anode is 10 nm.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 6

[0094] The difference between this embodiment and Embodiment 1 is that the thickness of the artificial interface layer in the modified silicon-carbon anode is 80 nm.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Example 7

[0097] The difference between this embodiment and embodiment 1 is that in step (3), the evaporation rate of the evaporation source material is 0.05 Å / s.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Example 8

[0100] The difference between this embodiment and embodiment 1 is that in step (3), the evaporation rate of the evaporation source material is 3 Å / s.

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that the artificial interface layer is not provided; that is, an all-solid-state lithium battery is prepared directly based on a commercially available silicon-carbon composite anode sheet.

[0104] The remaining preparation methods and parameters are consistent with those in Example 1.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that the artificial interface layer is made of lithium borate material, that is, the evaporation source material in step (2) is lithium borate material.

[0107] The remaining preparation methods and parameters are consistent with those in Example 1.

[0108] Performance testing

[0109] The artificial interface layer and all-solid-state lithium battery provided in the above embodiments and comparative examples were tested.

[0110] 1) Room temperature ionic conductivity:

[0111] The room-temperature ionic conductivity of the artificial interface layer was measured using powder pressing-AC impedance spectroscopy. The specific procedure was as follows: Approximately 300 mg of the dried artificial interface layer (powder) was placed in a nitrogen-atmospheric glove box, fitted with a 10 mm diameter stainless steel mold, and pressed into a dense disc under a uniaxial pressure of 300 MPa for 5 min. A gold layer approximately 100 nm thick was deposited on both sides of the disc using magnetron sputtering as ion-blocking electrodes. The sample was then placed in a sealed test fixture and tested at room temperature using an electrochemical workstation. The frequency scan range was 1 MHz to 0.1 Hz, and the perturbation voltage amplitude was 10 mV. The bulk resistance (Rt) was obtained from the impedance spectroscopy. b ), through the formula σ=d / (R b • A) Calculate the ionic conductivity, where d is the thickness of the disc (measured multiple times with a micrometer and the average value is taken, accurate to 0.001 mm), and A is the electrode area (calculated based on the mold diameter).

[0112] 2) Elastic modulus:

[0113] The elastic modulus of the artificial interface layer (thin film) was tested using a nanoindenter. The specific procedure was as follows: a Berkovich diamond indenter was selected, and at least five evenly distributed points were chosen on the sample surface for testing; a quasi-static indentation mode was used, setting the maximum indentation depth to 10% of the film thickness (e.g., 3 nm for a 30 nm film) to ensure the data was not affected by the substrate; the loading and unloading rate was set to 10 nm / s, and pressure was maintained at the maximum load for 5 seconds to eliminate creep effects; the load-displacement curve was automatically analyzed using the Oliver-Pharr model in the instrument software to calculate the elastic modulus, and the final result was the arithmetic mean of the five test points.

[0114] 3) Fracture toughness:

[0115] The fracture toughness of the artificial interface layer (thin film) was estimated using the nanoindentation-crack propagation method. The specific procedure is as follows: A relatively large load (e.g., 50 mN) was applied to the film surface using a Vickers diamond indenter, held for 10 seconds, and then unloaded, causing an indentation with radial cracks. The lengths (c) of four cracks propagating outward from the apex of the indentation were measured using a high-resolution scanning electron microscope. The fracture toughness was then calculated using formula K. IC =α(E / H) 1 / 2 (P / c 3 / 2 Calculate the fracture toughness, where α is an empirical constant (taken as 0.016), E is the elastic modulus, H is the hardness (obtained from the same indentation data), and P is the applied load; at least 3 indentation points are tested and the average value is taken.

[0116] 4) Initial interface impedance:

[0117] The initial interfacial impedance of the all-solid-state lithium battery was obtained through electrochemical impedance spectroscopy (EIS). The specific procedure was as follows: the assembled battery was left to stand for 2 hours under open-circuit voltage conditions, then placed in a constant temperature environment at 25°C; using an electrochemical workstation, the frequency scan range was set to 100kHz to 10mHz, and the applied sinusoidal perturbation voltage amplitude was 5mV; in the obtained Nyquist plot, the intercept of the high-frequency region with the real axis was equal to the ohmic resistance (R). Ω The semicircle appearing in the mid-to-high frequency region corresponds to the interface impedance (R). int Using ZView software, select an equivalent circuit model (such as R(CR)(CR)) for fitting and directly extract R. int The value is used as the initial interface impedance.

[0118] 5) First-lap Coulomb efficiency:

[0119] The first-cycle coulombic efficiency of the all-solid-state lithium battery was measured in a constant-current charge-discharge test. The specific procedure was as follows: the battery was placed in a 25°C constant-temperature chamber and subjected to the first cycle at a rate of 0.1C (1C is defined as the current at theoretical capacity). The charging method was: constant-current charging to the upper limit voltage of 4.2V, followed by constant-voltage charging until the current dropped to 0.05C; the discharging method was: constant-current discharging to the cutoff voltage of 2.5V. The first-cycle coulombic efficiency (ICE, %) = (first discharge capacity / first charge capacity) × 100%. The capacity value was automatically recorded and calculated by equipment (such as a Landon or LAND testing system).

[0120] 6) Capacity retention rate:

[0121] The capacity retention rate of all-solid-state lithium batteries is determined through long-cycle testing. The specific procedure is as follows: After the battery completes the first two cycles of 0.1C activation, starting from the third cycle, constant current charge-discharge cycles are performed within a 1C rate and a voltage window of 2.5-4.2V. The discharge capacity of each cycle is recorded. Capacity retention rate (cycle N, %) = (discharge capacity of cycle N / discharge capacity of cycle 3) × 100%; the capacity retention rate of the 100th cycle is recorded.

[0122] 7) Critical current density:

[0123] The critical current density of the all-solid-state lithium battery was tested using the stepped current method in a Li|-modified silicon-carbon anode symmetric cell. The specific procedure was as follows: a constant current density was applied to the battery (the initial point was typically 0.1 mA / cm²). 2 Lithium deposition was performed, and the voltage-time curve was observed after 1 hour; subsequently, the voltage was increased to 0.1 or 0.2 mA / cm². 2The deposition process was repeated with incrementally increasing current density. When the voltage curve experienced a sudden and significant negative drop (typically >1V) during deposition and could not recover, it was determined that lithium dendrites had pierced the separator, causing a short circuit. The highest current density before the short circuit occurred was recorded as the critical current density. The entire test was conducted at 25°C.

[0124] The results are shown in Table 1.

[0125] Table 1

[0126]

[0127] analyze:

[0128] As shown in Table 1, this invention provides an artificial interface layer composed of a nested hydroborate material. This artificial interface layer possesses both excellent mechanical flexibility and chemical stability, effectively absorbing and releasing the enormous stress of the silicon-carbon anode during cycling, adapting to the volume changes of silicon, thereby maintaining the integrity of the physical contact with the solid electrolyte layer and significantly reducing interfacial impedance. Simultaneously, the inherent ultra-high ionic conductivity of the nested hydroborate material constructs a "highway" for lithium ion transport between the anode and the solid electrolyte, significantly reducing the transport energy barrier at the solid-solid interface. Furthermore, this interface layer effectively isolates the silicon-carbon anode from direct contact with the solid electrolyte, suppressing harmful interfacial side reactions. Moreover, this artificial interface layer exhibits excellent versatility, adaptable to various solid electrolytes, and easy to integrate. All-solid-state lithium batteries constructed based on this interface layer demonstrate superior cycle life; lower impedance and higher critical current density indicate that the battery can withstand higher operating currents, exhibiting excellent rate performance.

[0129] As can be seen from the comparison between Example 1 and Example 4, the artificial interface layer provided by the present invention can also effectively improve the interfacial contact with the oxide electrolyte and exhibits better electrochemical performance than the bare negative electrode.

[0130] A comparison of Examples 1 and 5-6 shows that if the thickness of the artificial interface layer in the modified silicon-carbon anode is too small (e.g., 10 nm), its mechanical integrity is insufficient, failing to effectively buffer volumetric stress and block side reactions, leading to increased interface impedance and a significant decrease in cycle stability and critical current density. Conversely, if the thickness of the artificial interface layer in the modified silicon-carbon anode is too large (e.g., 80 nm), its own ion transport path lengthens, internal resistance increases, and the excessively thick brittle layer is more prone to overall fracture under stress, similarly resulting in decreased ionic conductivity, interface deterioration, and overall battery performance degradation. This demonstrates that controlling the interface layer thickness within the range of 20-50 nm is key to achieving the optimal performance balance.

[0131] A comparison of Examples 1 and 7-8 shows that if the evaporation rate of the evaporation source material is too low (e.g., 0.05 Å / s), impurities are easily introduced during the deposition process, making it difficult to form a dense film. This results in a loose interface layer, decreased purity, and deterioration of both ionic conductivity and mechanical strength. Conversely, if the evaporation rate of the evaporation source material is too high (e.g., 3 Å / s), the energy of the deposited particles is too high, easily damaging the nested boron cluster structure and forming a porous, rough film with high internal stress and poor bonding. This leads to a surge in interface layer impedance, deterioration of mechanical properties, and rapid battery failure. This demonstrates that controlling the thermal evaporation rate within the range of 0.1-2 Å / s is a necessary process condition for obtaining a high-performance interface layer.

[0132] As can be seen from the comparison between Example 1 and Comparative Example 1, if the artificial interface layer is not set, that is, if the all-solid-state lithium battery is prepared directly based on the commercial silicon-carbon composite negative electrode, the interface impedance is high, the cycle life is short, and the critical current density is low, which is not conducive to improving the rate performance of the battery.

[0133] As can be seen from the comparison between Example 1 and Comparative Example 2, if the artificial interface layer is composed of lithium borate material, its ionic conductivity is extremely low (~10). -6 The high S / cm elastic modulus and poor fracture toughness of the resulting interface layer, while providing some physical isolation, significantly hinder ion transport and result in high brittleness, making it prone to pulverization and fracture under cyclic stress. Therefore, its improvement on interface impedance, cycle life, and critical current density is extremely limited, far inferior to the solution of this invention. This highlights the crucial role of using nested hydroborates with open boron cluster structures in simultaneously achieving high ion conductivity and mechanical flexibility.

[0134] It should be noted that the present invention is illustrated through 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, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An artificial interface layer for silicon-carbon anodes in all-solid-state lithium batteries, characterized in that, The artificial interface layer is composed of a nested hydroborate material with an open boron cluster structure.

2. The artificial interface layer according to claim 1, characterized in that, The thickness of the artificial interface layer is 20-50 nm; And / or, the nested hydroborate material includes any one or a combination of at least two of lithium chloride-closed-dodecoborane, lithium bromide-closed-dodecoborane, lithium undecylhydro-closed-dodecoborate, or lithium decahydro-closed-decaborate.

3. The artificial interface layer according to claim 1 or 2, characterized in that, The nested hydroborate material has an open boron cluster structure; And / or, the room temperature ionic conductivity of the artificial interface layer is ≥1×10⁻⁶. -3 S / cm; And / or, the elastic modulus of the artificial interface layer is 0.5-5 GPa; And / or, the fracture toughness of the artificial interface layer is ≥0.5 MPa·m 0.5 .

4. A method for preparing an artificial interface layer for a silicon-carbon anode in an all-solid-state lithium battery as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: Provide silicon-carbon anode substrate; Nested hydroborate material is deposited on the surface of the silicon-carbon anode substrate to obtain the artificial interface layer.

5. The preparation method according to claim 4, characterized in that, The deposition method includes low-temperature vapor deposition, preferably physical vapor deposition, and more preferably thermal evaporation. And / or, the deposition process is carried out in a vacuum environment with a vacuum level of 1×10⁻⁶. -4 Pa-1×10 -2 Pa; And / or, during the deposition process, the temperature of the silicon-carbon anode substrate is controlled at 25-80°C.

6. The preparation method according to claim 5, characterized in that, In the thermal evaporation method, the evaporation source material includes any one or a combination of at least two of the following: lithium chloride-closed-dodecoborane, lithium bromide-closed-dodecoborane, lithium undecylhydrogen-closed-dodecoborate, or lithium decahydrogen-closed-decaborate. And / or, in the thermal evaporation method, the evaporation rate of the evaporation source material is 0.1-2 Å / s.

7. A modified silicon-carbon anode for all-solid-state lithium batteries, characterized in that, The modified silicon-carbon anode includes a silicon-carbon anode substrate and an artificial interface layer as described in any one of claims 1-3 disposed on the surface of the silicon-carbon anode substrate.

8. The modified silicon-carbon anode according to claim 7, characterized in that, The thickness ratio of the silicon-carbon anode substrate to the artificial interface layer is (1000-5000):

1.

9. A fully solid-state lithium battery, characterized in that, The all-solid-state lithium battery includes a positive electrode, a negative electrode, and a solid electrolyte layer, wherein the negative electrode is the modified silicon-carbon negative electrode as described in claim 7 or 8; In this process, the artificial interface layer of the modified silicon-carbon anode is in direct contact with the solid electrolyte layer.

10. The all-solid-state lithium battery according to claim 9, characterized in that, The solid electrolyte layer is a sulfide solid electrolyte layer or an oxide solid electrolyte layer.

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