A polymeric sieving interphase silicon-carbon negative electrode material for all-solid-state batteries and a preparation method and application thereof

Abstract

This invention relates to the field of lithium battery anode material technology, specifically a polymer sieving interface silicon-carbon anode material for all-solid-state batteries, its preparation method, and its application. It comprises a porous carbon material matrix with micropores / mesoporous pores of 1-5 nm in diameter. A silicon-carbon composite matrix is ​​first formed by depositing a 1-2 nm diameter nano-silicon layer within the pores of the porous carbon material matrix. Then, a polymer layer is deposited on the surface of the silicon-carbon composite matrix to form a silicon-carbon anode material with nano-confined pores and a polymer sieving interface layer of 2-50 nm thickness and an elastic modulus of 0.1-15 GPa. The polymer layer is formed by cross-linking and polymerizing at least one polymerizable monomer containing ether bonds with at least one cross-linking agent. The preparation process is simple and mature, showing great promise for industrialization. It solves the problems of interface instability and slow ion transport kinetics in existing technologies, meeting the operating requirements under low external pressure conditions, enabling all-solid-state batteries to possess both high specific energy and long cycle life.

Description

Technical Field

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

[0002] All-solid-state batteries combine the advantages of high energy density and high safety, making them a promising next-generation electrochemical energy storage technology. Silicon anodes, with their high theoretical capacity (3579 mAh•g), are particularly promising. -1 ) and suitable lithium intercalation potential (0.4V vs. Li) + Li₂ / Li₂, while maintaining high energy density, avoids dendrite problems, making it a key anode choice for constructing high-safety, high-performance solid-state lithium batteries.

[0003] However, the silicon anode undergoes a massive volume change (>300%) during lithium insertion / extraction, making it difficult to maintain good contact at the rigid solid / solid interface with the solid electrolyte. Currently, high external pressure (≥50MPa) is often required to ensure interfacial bonding and prevent increased polarization and capacity decay due to contact failure. The significant gap between this high external pressure requirement and the low external pressure (≤2MPa) required in practical applications leads to substantial volume changes in the silicon anode, easily causing interfacial delamination and stress accumulation, resulting in interfacial failure, impedance surges, and rapid capacity decay, severely restricting its long-cycle performance and practical application. Therefore, solving the interfacial instability problem between the silicon anode and the solid electrolyte under low external pressure (≤2MPa) is key to promoting the practical application of silicon-based all-solid-state batteries.

[0004] To address this, existing technologies employ graphene hydrogel shrinkage to construct a pre-compressed negative electrode (volume expansion rate >100%), enabling the battery to cycle under an external pressure of 2 MPa. However, this method struggles to avoid interfacial side reactions caused by direct contact between the sulfide electrolyte and carbon materials. Existing technologies also utilize Li... 21 Si5 / Si–Li 21 The Si5 bilayer anode structure enables operation without external pressure; however, it uses a pure silicon anode (volume expansion rate >300%) and still contains active lithium components, making it difficult to avoid the risks of interface instability and dendrite growth. In summary, under low external pressure conditions, the core bottleneck of silicon-based all-solid-state batteries remains the interface instability caused by the intrinsic volume expansion of the silicon anode. Current technologies have not fundamentally suppressed the expansion and side reactions of silicon-based anodes. Therefore, it is urgent to reduce the intrinsic expansion rate of silicon anodes and coordinate interface modification to balance ion transport and chemical stability, thereby systematically realizing the construction of high-energy-density, long-life silicon-based all-solid-state batteries operating under low external pressure. Summary of the Invention

[0005] Based on the background technology, this invention provides a polymer sieving interface silicon-carbon anode material for all-solid-state batteries, its preparation method, and its application. The aim is to solve the problems of interface instability and slow ion transport dynamics of silicon-carbon anode materials by designing a polymer sieving interface layer, thereby enabling it to have both high specific energy and long cycle life, and meet the operating requirements of all-solid-state batteries under low external pressure conditions.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention are as follows.

[0007] Firstly, this invention proposes a polymer sieving interface silicon-carbon anode material for all-solid-state batteries, comprising a porous carbon material matrix. The porous carbon material matrix has micropores / mesopores with a pore size of 1-5 nm, which can reserve space for the deposition of nano-silicon layers within its channels. A nano-silicon layer with a diameter of 1-2 nm is first deposited within the channels of the porous carbon material matrix to form a silicon-carbon composite matrix. Then, a polymer layer is deposited on the surface of the silicon-carbon composite matrix to form a polymer sieving interface layer, thereby obtaining the polymer sieving interface silicon-carbon anode material. The polymer sieve interface layer has a thickness of 2-50 nm and an elastic modulus of 0.1-15 GPa. The polymer layer is deposited at the pore openings of the channels without blocking the pore openings, so that the polymer sieve interface silicon-carbon anode material has nano-confined channels. The polymer layer is formed by cross-linking and polymerizing at least one polymerizable monomer containing an ether bond in its molecular structure with at least one cross-linking agent; wherein, the polymerizable monomer contains at least one C–O–C ether bond structure in its molecular structure, and also contains at least one unsaturated structural unit that can undergo a polymerization reaction; the cross-linking agent is a polymerizable molecule containing at least two unsaturated structural units that can undergo a polymerization reaction, so as to realize the construction of a three-dimensional cross-linked polymer network.

[0008] Compared with the prior art, the present invention designs a silicon-carbon anode material with nano-confined pores and a polymer sieving interface layer with a thickness of 2-50 nm and an elastic modulus of 0.1-15 GPa. The polymer sieving interface layer is formed by cross-linking and polymerization of at least one polymerizable monomer containing ether bonds and at least one cross-linking agent, and has multiple functions of physical sieving, electrochemical sieving and mechanical-chemical coupling sieving: (1) It acts as a physical barrier to isolate the direct contact between the silicon-carbon anode and the solid electrolyte, inhibit the occurrence of side reactions, and play a physical sieving role; (2) The functional groups such as ether oxygen bonds contained in the polymer material react with lithium ions in Lewis acid-base reactions. The function is to construct a low-energy barrier migration channel for lithium ions by regulating the activation energy at the interface, forming a high-energy barrier for the transfer of electrons at the interface or by-reaction products, thereby achieving selective transport of lithium ions and playing an electrochemical sieving role; (3) The polymer layer is deposited at the pore opening of the channel without blocking the pore opening to generate the pore opening effect. The viscoelasticity and pore opening effect of the polymer sieving interface layer realize stress "sieving" during the cycle, concentrating the volume expansion stress of silicon at the pore opening and realizing the elastic storage and release of stress, playing a mechanical-chemical coupling sieving role, thereby maintaining the dynamic and stable contact between the silicon carbon negative electrode and the solid electrolyte interface during the cycle of the all-solid-state battery.

[0009] In summary, in the obtained polymer-sieved interface silicon-carbon anode material, the nano-confined pores provide the first-level buffer protection for the volume change of silicon, and the polymer sieved interface layer absorbs the expansion stress through its own deformation to form the second-level buffer protection. The synergistic effect of the two-level buffer protection can effectively suppress particle breakage and anode sheet structure collapse, achieve intrinsic low expansion, and enable the anode sheet to maintain a high degree of structural integrity during long-term cycling. This meets the operating requirements of all-solid-state batteries under low external pressure conditions, and the obtained all-solid-state battery has both high specific energy and long cycle life.

[0010] Furthermore, the pore size of the nano-confined pores is 0.7-1.8 nm.

[0011] Porous carbon material matrices possess micropores / mesopores with pore sizes of 1-5 nm. Even after depositing a 1-2 nm diameter nano-silicon layer within the pores, space remains. In contrast, polymer layers are deposited at the pore openings, preserving the pores and preventing clogging – this is the key difference between this and traditional coating methods. In this technical solution, the final retained pore size is 0.7-1.8 nm. The resulting pore opening effect enables stress "sieving" during cycling, concentrating the volumetric expansion stress of silicon at the pore openings and achieving elastic stress storage and release. This maintains dynamic and stable contact between the silicon-carbon anode and the solid electrolyte interface during cycling.

[0012] Furthermore, the specific surface area of ​​the porous carbon material matrix is ​​500-3000 m². 2 / g, pore volume of 0.2-2.0cm 3 / g.

[0013] In this technical solution, the specific surface area of ​​the porous carbon material matrix meets the above requirements, providing sufficient pore size for the deposition of nano-silicon while avoiding excessive side reactions caused by an excessively high specific surface area. The pore volume of the porous carbon material matrix also meets the above requirements, ensuring sufficient space to accommodate the volume expansion of silicon without making the material too loose. This porous carbon material matrix, meeting the above requirements, provides appropriate reserved space for the deposition of nano-silicon and effectively provides mechanical support, effectively reducing the material expansion rate, which is a prerequisite for interface stability.

[0014] Furthermore, the polymerizable monomer is selected from at least one of polyethylene glycol methacrylate, polyethylene glycol diacrylate, ethyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether.

[0015] Furthermore, the crosslinking agent is selected from at least one of ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, divinylbenzene, and compounds containing two or more vinyl groups.

[0016] Through the crosslinking polymerization of the above polymerizable monomers and crosslinking agents, the resulting polymer sieve interface layer has both good ionic conductivity and viscoelasticity. It can be used as an artificial solid electrolyte interface to form a tight and stable solid / solid contact interface with various solid electrolytes such as sulfides and oxides. It can maintain excellent interface stability under low external pressure (≤2 MPa) without the need for additional pressure devices, which greatly simplifies battery packaging design.

[0017] Secondly, this invention proposes a method for preparing a polymer-sieved interface silicon-carbon anode material for all-solid-state batteries, comprising the following steps: S1. Provide a porous carbon material matrix; S2. A nano-silicon layer generated by the decomposition of silicon source gas is deposited into the pores of the porous carbon matrix by chemical vapor deposition (CVD) to obtain a silicon-carbon composite matrix. S3. The polymer layer is polymerized on the surface of the silicon-carbon composite matrix by initiation chemical vapor deposition (iCVD) to form the polymer sieve interface layer.

[0018] In this technical solution, the porous carbon material matrix described in step S1 satisfies the following requirements: it has micropores / mesopores with a pore size of 1-5 nm and a specific surface area of ​​500-3000 m². 2 / g, pore volume of 0.2-2.0cm 3 / g.

[0019] In this technical solution, the silicon source gas can be selected from one or more of silane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and methylsilane. The deposition chamber used in CVD can be any one of the deposition chambers of fluidized bed, tube furnace, rotary kiln, pusher kiln, roller kiln, conveyor belt kiln, air cushion kiln, and walking beam furnace.

[0020] In this technical solution, the initiation-based chemical vapor deposition method described in step S3 is a relatively mature process in the coating field. The main reaction conditions are: sample stage temperature 25-40℃, working pressure 0.1-1 Torr, initiator filament temperature 200-300℃, and deposition time 5-40 min.

[0021] Furthermore, to meet the requirements of subsequent iCVD polymer sieving interface layer construction, the specific surface area of ​​the silicon-carbon composite matrix obtained in step S2 is 100-500 m². 2 / g, pore volume 0.05-0.5cm 3 / g.

[0022] In this technical solution, the silicon-carbon composite matrix is ​​a silicon-carbon composite matrix with intrinsically reserved space. In order to achieve a silicon-carbon composite matrix that meets the above requirements, the preferred chemical vapor deposition conditions in step S2 are: deposition temperature 430-600℃, deposition time 30-120min, and silicon source gas concentration 5vol%-30vol%.

[0023] Furthermore, step S3 specifically involves placing the silicon-carbon composite matrix in an initiation chemical vapor deposition reaction chamber, introducing polymerizable monomers, crosslinking agents, and initiators to perform initiation chemical vapor deposition polymerization to form the polymer sieve interface layer. The molar ratio of polymerizable monomers to crosslinking agents is (50-99):(1-50), and the molar ratio of the sum of the molar amounts of polymerizable monomers and crosslinking agents to the molar ratio of the initiator is 100:(0.1-10). Preferably, the molar ratio of polymerizable monomer to crosslinking agent is (70-95):(5-30), and the molar ratio of the sum of the molar amounts of polymerizable monomer and crosslinking agent to the molar ratio of initiator is 100:(0.5-5). Preferably, the initiator is selected from at least one of tert-butyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, tert-butyl hydroperoxide, and azobisisobutyronitrile; Specifically, the mixed vapor of polymerizable monomers and crosslinking agents and the vapor of initiator are introduced into the initiation chemical vapor deposition reaction chamber, and the working pressure and filament temperature are adjusted to the set values. When the initiator passes through the filament, it decomposes to generate free radicals, which then initiate the gas-phase polymerization reaction of polymerizable monomers and crosslinking agents on the surface of silicon-carbon composite matrix to form the polymer sieve interface layer.

[0024] In summary, the preparation of the polymer sieved interface silicon-carbon anode material for all-solid-state batteries proposed in this invention is simple. The chemical vapor deposition and initiation chemical vapor deposition used are both mature technologies for large-scale industrial preparation of deposited materials. By controlling the reaction conditions, the polymer sieved interface layer that meets the design requirements can be accurately obtained, which has significant industrialization prospects.

[0025] Thirdly, this invention proposes a negative electrode sheet, using the aforementioned polymer-sieved interface silicon-carbon negative electrode material for all-solid-state batteries as the active material.

[0026] Fourth, the present invention proposes an all-solid-state battery, comprising: a positive electrode, a solid electrolyte and the aforementioned negative electrode.

[0027] Furthermore, the solid electrolyte is a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte; Specifically, when operating under low external pressure conditions not exceeding 2MPa, its capacity retention rate is higher than 80% after 500 cycles; moreover, based on the structural and performance advantages of the polymer sieving interface, its application in all-solid-state batteries can also improve the battery's fast-charging capability. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The graph shows the cycle stability and coulombic efficiency of a 2Ah all-solid-state pouch cell assembled from PSI-SC-1, the product of Example 1 of this invention, at 2MPa. Figure 2 The nitrogen (77 K) desorption curves of PC, SC and PSI-SC-1 in Example 1 of this invention are shown. Figure 3 X-ray diffraction (XRD) curves of PC, SC, and PSI-SC-1 in Embodiment 1 of the invention; Figure 4 The small-angle X-ray diffraction (SAXS) curves of PC, SC, and PSI-SC-1 in Embodiment 1 of the present invention are shown. Figure 5 This is a transmission electron microscope (TEM) image of the polymer interface layer of PSI-SC-1 in Example 1 of the present invention; Figure 6 The loading-unloading curve is obtained from the nanoindentation test of PSI-SC-1 in Example 1 of this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] All chemical raw materials used in the following examples and comparative examples are commercially available, and all apparatus and operations involved are conventional in the art.

[0032] Example 1

[0033] The following steps were performed to prepare the polymer-sieved interface silicon-carbon anode material: S1, with a specific surface area of ​​approximately 2000 m² 2 / g, pore volume approximately 1.0cm 3 / g, commercially available porous carbon powder with a pore size distribution concentrated in 1-3nm as the porous carbon material matrix (abbreviated as: PC); S2. Spread 10g of porous carbon material matrix evenly in a quartz boat and place it in the constant temperature zone of a tube furnace. First, introduce high-purity argon gas (flow rate 500 sccm) into the tube furnace to purge air. Then, raise the furnace temperature to 550℃ at a heating rate of 5℃ / min and maintain the temperature stable. Next, introduce high-purity SiH4 silicon source gas at a flow rate of 50 sccm, while maintaining the total flow rate of high-purity argon gas at 500 sccm. Deposit at atmospheric pressure for 120min to allow the nano-silicon generated by the pyrolysis of SiH4 to be deposited on the inner wall of the pores of the porous carbon material matrix. After the deposition reaction is completed, stop introducing SiH4 and allow it to cool naturally to room temperature under high-purity argon gas to obtain a silicon-carbon composite matrix (abbreviated as: SC). S3. Take 2g of the SC powder obtained in step S2 and disperse it evenly on the sample stage of the iCVD reaction chamber and control the sample stage temperature to 30℃. First, evacuate the reaction chamber to a background pressure below 0.01 Torr. Then, introduce the mixed vapor (total flow rate of 100 sccm) of polymerizable monomer ethylene glycol dimethacrylate (EGDMA) and crosslinking agent divinylbenzene (DVB) and the vapor (flow rate of 10 sccm) of initiator tert-butyl peroxide (TBPO) into the reaction chamber. The molar ratio of EGDMA to DVB is 70:30. Maintain the working pressure at 0.5 Torr and heat the filament to 250℃. When TBPO flows through the hot filament, it decomposes to generate free radicals, which initiate the gas-phase polymerization reaction of EGDMA and DVB on the SC surface. Control the gas-phase polymerization reaction time to 15 min. After the reaction is completed, stop the introduction of polymerizable monomer, crosslinking agent and initiator, and continue to evacuate for 10 min to remove unreacted raw materials and by-products to obtain the final product.

[0034] The resulting product is abbreviated as PSI-SC-1.

[0035] like Figure 2 As shown: The specific surface area of ​​PC in Example 1 is 1998 m². 2 / g, pore volume is 0.925cm 3 / g; the specific surface area of ​​SC obtained after CVD deposition is 200.9m². 2 / g, pore volume is 0.121cm 3 / g, and after iCVD construction of the polymerization sieving interface, the specific surface area of ​​PSI-SC-1 obtained is 4.29m². 2 / g, pore volume 0.0125cm 3 / g; Obviously, the specific surface area and pore volume of the material are significantly reduced after the first step of CVD deposition, indicating that SiH4 gas decomposes and silicon is deposited within the pores of porous carbon; at the same time, the construction of the polymer sieving interface further significantly reduces the nitrogen adsorption capacity of PSI-SC-1, indicating that the pore structure has changed further, and this polymer layer is mainly deposited on the material surface, which together leads to the decrease in adsorption capacity. Figure 3 As shown: the XRD pattern of SC shows no obvious crystalline silicon peaks, indicating that the deposited nano-silicon within the channels exists in an amorphous form, which is consistent with expectations; fitting analysis revealed that the size of the deposited nano-silicon layer is 1-2 nm, which is currently widely recognized as the optimal structure for silicon prepared by chemical vapor deposition (CVD). Figure 4 As shown: Based on SAXS data, the internal specific surface areas of PC, SC, and PSI-SC-1 are calculated to be 1785.6 m². 2 / g、615.6m 2 / g and 605.6m 2 / g, PSI-SC-1 has a pore size of 1.2nm; from PC to SC, the internal specific surface area of ​​the material decreases significantly, indicating a substantial reduction in porosity, showing that Si successfully enters and occupies the internal space of the PC nanopores; it is worth noting that there is only a slight difference in the internal specific surface area between SC and PSI-SC-1, and the difference is not obvious on the SAXS curve. This phenomenon indicates that the polymerization sieving interface constructed by the iCVD process mainly tends to accumulate at the pore inlet, tightening the pore inlet size, rather than filling the pore interior. Therefore, the internal cavity structure of the SC pores is still preserved, and the resulting silicon-carbon anode material has nano-confined channels. Figure 5 As shown: Nanoindentation testing reveals that the elastic modulus of the polymer sieve interface layer of the product is 9.5 GPa. This excellent elasticity effectively stores and releases energy, suppressing the volume expansion of the nano-silicon layer during charging and discharging. Figure 6 As shown, the polymer sieve interface layer thickness is 11.2 nm, and the ion transport path is short, which is beneficial to rapid electrochemical kinetics.

[0036] Example 2

[0037] Compared with Example 1, in step S3, the molar ratio of EGDMA to DVB was adjusted from 70:30 to 50:50, the flow rate of TBPO was adjusted from 10 sccm to 5 sccm, the sample stage temperature was adjusted from 30℃ to 35℃, the working pressure was adjusted from 0.5 Torr to 0.2 Torr, and the filament temperature was adjusted from 250℃ to 280℃. All other aspects remained the same as in Example 1.

[0038] The resulting product is referred to as PSI-SC-2.

[0039] Example 3

[0040] Compared with Example 1, the specific surface area of ​​the porous carbon material substrate in step S1 increased from 2000 m² / g. 2 / g adjusted to 2500m 2 / g; In step S2, the deposition temperature was adjusted from 550℃ to 500℃, the flow rate of high-purity SiH4 was adjusted from 50sccm to 30sccm, and the deposition time was adjusted from 120min to 180min; In step S3, the flow rate of TBPO was adjusted from 10sccm to 3sccm, and the rest remained the same as in Example 1.

[0041] The resulting product is abbreviated as PSI-SC-3.

[0042] Example 4

[0043] Compared with Example 1, the molar ratio of EGDMA to DVB in step S3 was adjusted from 70:30 to 90:10, while the rest remained the same as in Example 1.

[0044] The resulting product is abbreviated as PSI-SC-4.

[0045] Example 5

[0046] Compared with Example 1, the time for the gas-phase polymerization reaction in step S3 was adjusted from 15 min to 40 min, while the rest remained the same as in Example 1.

[0047] The resulting product is abbreviated as PSI-SC-5.

[0048] Example 6

[0049] Compared with Example 1, the time for the gas-phase polymerization reaction in step S3 was adjusted from 15 min to 5 min, while the rest remained the same as in Example 1.

[0050] The resulting product is abbreviated as PSI-SC-6.

[0051] Example 7

[0052] Compared to Example 1, the polymerizable monomer and crosslinking agent were both adjusted to equal amounts of polyethylene glycol diacrylate (PEGDA), while all other aspects remained the same as in Example 1.

[0053] The resulting product is abbreviated as PSI-SC-7.

[0054] Example 8

[0055] Compared with Example 1, the molar ratio of EGDMA to DVB in step S3 was adjusted from 70:30 to 95:5, while the rest remained the same as in Example 1.

[0056] The resulting product is abbreviated as PSI-SC-8.

[0057] Example 9

[0058] Compared with Example 1, the molar ratio of EGDMA to DVB in step S3 was adjusted from 70:30 to 80:20, while the rest remained the same as in Example 1.

[0059] The resulting product is abbreviated as PSI-SC-9.

[0060] Example 10

[0061] Compared with Example 1, the molar ratio of EGDMA to DVB in step S3 was adjusted from 70:30 to 50:50, while the rest remained the same as in Example 1.

[0062] The resulting product is referred to as PSI-SC-10.

[0063] Example 11

[0064] Compared with Example 1, the molar ratio of EGDMA to DVB in step S3 was adjusted from 70:30 to 99:1, while the rest remained the same as in Example 1.

[0065] The resulting product is abbreviated as PSI-SC-11.

[0066] Example 12

[0067] Compared with Example 1, the polymerizable monomer in step S3 was changed from ethylene glycol dimethacrylate to ethyl vinyl ether, and the crosslinking agent was changed from divinylbenzene to 1,4-butanediol diacrylate. All other steps remained the same as in Example 1.

[0068] The resulting product is referred to as PSI-SC-12.

[0069] Comparative Example 1 Compared with Example 1, step S3 is omitted, and all other steps are the same as in Example 1.

[0070] Comparative Example 2 Compared with Example 1, this comparative example does not use iCVD in-situ gas-phase polymerization to construct the polymer sieving interface. Instead, it uses a solution method to form a polymer coating layer on the surface of a silicon-carbon composite matrix. The specific preparation process is as follows: S1 and S2 are the same as in Example 1, to obtain a silicon-carbon composite matrix (abbreviated as: SC). S3 and S4 are adjusted, and the specific operations are as follows: S3. Take 2g of SC powder and add it to an organic solvent containing polymerizable monomer ethylene glycol dimethacrylate (EGDMA), crosslinking agent divinylbenzene (DVB), and initiator tert-butyl peroxide (TBPO), wherein the molar ratio of EGDMA to DVB is 70:30, and the amount of initiator TBPO added is consistent with that in Example 1; stir the mixture thoroughly at room temperature to make the SC powder uniformly dispersed in the solution, and initiate the free radical polymerization reaction of EGDMA and DVB in the solution environment, thereby forming a polymer coating layer on the surface of the SC powder; S4. After the polymerization reaction is completed, the solid product is separated by filtration or centrifugation and dried under vacuum to remove residual solvent and unreacted components, resulting in a silicon-carbon composite material with a cross-linked polymer layer on the surface.

[0071] The resulting product is referred to as CP-SC-2.

[0072] Comparative Example 3 Compared with Example 1, the porous carbon material matrix in step S1 was adjusted to a porous carbon material with a predominantly microporous structure, and its specific surface area was 2120 m². 2 / g, pore volume 0.95cm 3 / g, the pore size is mainly concentrated in 0.7nm, and basically does not contain mesoporous structures in the range of 1-5nm; the remaining steps are the same as in Example 1.

[0073] The resulting product is referred to as CP-SC-3.

[0074] Comparative Example 4 Compared with Example 1, the polymerizable monomer used in step S3 was adjusted to a polymerization system without C–O–C ether bond structure. The remaining steps were the same as in Example 1. The specific operation of S3 was as follows: 2g of SC powder obtained in step S2 was taken and evenly dispersed on the sample stage of the iCVD reaction chamber, and the sample stage temperature was controlled at 30°C; a mixture of polymerizable monomer methyl methacrylate (MMA) and crosslinking agent DVB vapor was introduced into the reaction chamber, wherein the molar ratio of MMA to DVB was 70:30, and the initiator was TBPO. The introduction method and reaction conditions were the same as in Example 1; under free radical initiation conditions, MMA and DVB underwent gas-phase polymerization on the SC surface to form a polymer coating layer.

[0075] The resulting product is referred to as CP-SC-4.

[0076] The products obtained from each embodiment and comparative example were assembled into button cells and subjected to relevant electrochemical performance tests as follows: (1) Preparation of negative electrode sheet: The products obtained from each embodiment and comparative example were used as active materials and were thoroughly mixed and ground in an agate mortar with sulfide solid electrolyte Li6PS5Cl and conductive agent vapor-grown carbon fiber VGCF at a mass ratio of 70:25:5 to obtain negative electrode composite material; then about 20mg of negative electrode composite material was pressed into a sheet-shaped negative electrode with a diameter of 10mm under a pressure of 250MPa; (2) Preparation of positive electrode sheet: NCM81 active material was used as active material Li6PS5Cl and VGCF are thoroughly mixed and ground in an agate mortar at a mass ratio of 80:15:5 to obtain a positive electrode composite material; then about 15mg of the positive electrode composite material is pressed into a sheet-shaped positive electrode with a diameter of 10mm under a pressure of 200MPa; (3) Battery assembly: in an argon-protected glove box (H2O, O2<0.1ppm), the negative electrode sheet, the sulfide solid electrolyte Li6PS5Cl (about 80mg, pressed into a sheet under 300MPa), and the positive electrode sheet are pressed into a whole under a pressure of 200MPa to obtain an all-solid-state mold battery. The electrochemical performance of the obtained all-solid-state mold battery was tested. All electrochemical performance tests were conducted at 25℃ and 2MPa external pressure. Charge-discharge cycle tests were performed at a current of 0.5C (1C=1500mA / g) with a voltage window of 2.5-4.3V. The discharge specific energy of the first cycle and the discharge specific energy of the 500th cycle were calculated, and the capacity retention rate after 500 cycles was calculated. The specific test results are shown in Table 1.

[0077]

[0078] From Table 1, Figures 1-6 As shown in the following: The test results from Examples 1-12 and Comparative Examples 1 and 2 show that: when no polymer layer is provided on the surface of the silicon-carbon anode, the capacity retention rate of the assembled all-solid-state battery after 500 cycles at 0.5C is only 46.5%; when a polymer coating layer is constructed on the surface of the silicon-carbon anode using a traditional coating method, the corresponding capacity retention rate increases to 57.5%; while the silicon-carbon anode material with a polymer sieving interface proposed in this invention can achieve a capacity retention rate as high as 80.3%-86.3% under the same test conditions, with a much higher improvement effect than the traditional coating method. Taking the product PSI-SC-1 obtained in Example 1 as an example, as... Figure 1 As shown, a 2Ah all-solid-state pouch cell assembled from PSI-SC-1 cells retains 80% of its capacity after 500 cycles, with a coulombic efficiency consistently above 99%, demonstrating excellent interface stability. Clearly, this invention solves the problems of interface instability and slow ion transport kinetics in existing technologies, meeting the operational requirements under low external pressure conditions and enabling all-solid-state batteries to possess both high specific energy and long cycle life.

[0079] A comparison of the test results from Example 1 and Comparative Example 3 reveals that when the pore size in the porous carbon matrix is ​​concentrated at 0.7 nm, this size is significantly smaller than the effective diffusion size of polymerizable monomers and crosslinking agents under iCVD conditions. In the initial stage of gas-phase polymerization, the polymerization reaction preferentially occurs at the pore openings and the outer surface of the particles, leading to rapid pore blockage by the polymer. Subsequently, silicon source gas molecules struggle to enter the micropores to continue the polymerization reaction, ultimately resulting in the polymer mainly distributed on the outer surface of the particles, forming a coating polymer layer. This prevents the construction of a continuous, confined polymer sieving interface structure within the pores and at the silicon / carbon interface. Therefore, whether the porous carbon matrix possesses appropriately sized mesopores / micropores directly determines whether a polymer sieving interface structure can be successfully constructed.

[0080] A comparison of the test results from Example 1 and Comparative Example 4 shows that if the polymerizable monomer does not contain C–O–C ether bonds, the resulting polymer sieve interface layer has weak solvation and coordination capabilities for lithium ions, making it difficult to form an effective ion-selective transport channel. Simultaneously, the resulting polymer sieve interface layer has a high elastic modulus, making it difficult to buffer the volume changes of silicon during charging and discharging, leading to interface stress concentration and decreased structural stability. Consequently, the cycle stability and rate performance of the resulting silicon-carbon anode material are significantly inferior to those of Example 1. Therefore, C–O–C ether bonds in the polymerizable monomer are crucial for constructing a polymer sieve interface layer with an appropriate elastic modulus.

[0081] In summary, this invention first deposits nano-silicon within the pores of a porous carbon material with micropores / mesoporous structures of 1-5 nm, reserving space to obtain a silicon-carbon composite matrix. Then, a polymer layer that does not clog the pores is deposited on the surface of the silicon-carbon composite matrix, resulting in a silicon-carbon anode material with nano-confined channels and a polymer sieve interface with a thickness of 2-50 nm and an elastic modulus of 0.1-15 GPa. The nano-confined pores of this silicon-carbon anode material provide a first-level buffer protection against silicon volume changes, while the polymer sieve interface layer absorbs expansion stress through its own deformation, forming a second-level buffer protection. The synergistic effect of these two levels of buffer protection meets the operational requirements of all-solid-state batteries under low external pressure conditions. The resulting all-solid-state battery exhibits both high specific energy and long cycle life, solving the problems of interface instability and slow ion transport kinetics in silicon-carbon anode materials.

[0082] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A polymer-sieved interfacial silicon-carbon anode material for all-solid-state batteries, characterized in that: The material includes a porous carbon material matrix, which has micropores / mesopores with a pore size of 1-5 nm. A nano-silicon layer with a diameter of 1-2 nm is first deposited in the pores of the porous carbon material matrix to form a silicon-carbon composite matrix. Then, a polymer layer is deposited on the surface of the silicon-carbon composite matrix to form a polymer sieving interface layer, thereby obtaining the polymer sieving interface silicon-carbon anode material. The polymer sieve interface layer has a thickness of 2-50 nm and an elastic modulus of 0.1-15 GPa. The polymer layer is deposited at the pore openings of the channels without blocking the pore openings, so that the polymer sieve interface silicon-carbon anode material has nano-confined channels. The polymer layer is formed by cross-linking and polymerizing at least one polymerizable monomer containing an ether bond in its molecular structure with at least one cross-linking agent; wherein, the polymerizable monomer contains at least one C–O–C ether bond structure in its molecular structure, and also contains at least one unsaturated structural unit that can undergo a polymerization reaction; the cross-linking agent is a polymerizable molecule containing at least two unsaturated structural units that can undergo a polymerization reaction, so as to realize the construction of a three-dimensional cross-linked polymer network.

2. The polymer-sieved interface silicon-carbon anode material for all-solid-state batteries according to claim 1, characterized in that: The pore size of the nano-confined pores is 0.7-1.8 nm.

3. The polymer-sieved interfacial silicon-carbon anode material for all-solid-state batteries according to claim 1, characterized in that: The porous carbon material matrix has a specific surface area of ​​500-3000 m². 2 / g, pore volume of 0.2-2.0cm 3 / g.

4. The polymer-sieved interfacial silicon-carbon anode material for all-solid-state batteries according to claim 1, characterized in that: The polymerizable monomer is selected from at least one of polyethylene glycol methacrylate, polyethylene glycol diacrylate, ethyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether.

5. The polymer-sieved interfacial silicon-carbon anode material for all-solid-state batteries according to claim 1, characterized in that: The crosslinking agent is selected from at least one of ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, divinylbenzene, and compounds containing two or more vinyl groups.

6. A method for preparing a polymer-sieved interface silicon-carbon anode material for all-solid-state batteries as described in any one of claims 1-5, characterized in that: The following steps are included: S1. Provide a porous carbon material matrix; S2. A nano-silicon layer generated by the decomposition of silicon source gas is deposited into the pores of the porous carbon matrix by chemical vapor deposition to obtain a silicon-carbon composite matrix. S3. The polymer layer is polymerized on the surface of the silicon-carbon composite matrix by initiation chemical vapor deposition to form the polymer sieving interface layer.

7. The method for preparing the polymer-sieved interface silicon-carbon anode material for all-solid-state batteries according to claim 6, characterized in that: The silicon-carbon composite matrix obtained in step S2 has a specific surface area of ​​100-500 m². 2 / g, pore volume 0.05-0.5cm 3 / g; The specific operation of step S3 is as follows: the silicon-carbon composite matrix is ​​placed in the initiation chemical vapor deposition reaction chamber, and polymerizable monomers, crosslinking agents and initiators are introduced to carry out initiation chemical vapor deposition polymerization to form the polymer sieve interface layer. The molar ratio of polymerizable monomers to crosslinking agents is (50-99):(1-50), and the molar ratio of the sum of the molar amounts of polymerizable monomers and crosslinking agents to the molar ratio of initiator is 100:(0.1-10). Preferably, the molar ratio of polymerizable monomer to crosslinking agent is (70-95):(5-30), and the molar ratio of the sum of the molar amounts of polymerizable monomer and crosslinking agent to the molar ratio of initiator is 100:(0.5-5). Preferably, the initiator is selected from at least one of tert-butyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, tert-butyl hydroperoxide, and azobisisobutyronitrile.

8. A negative electrode sheet, characterized in that: The polymer-sieved interface silicon-carbon anode material for all-solid-state batteries as described in any one of claims 1-5 is used as the active material.

9. An all-solid-state battery, comprising: Positive electrode, solid electrolyte and negative electrode as described in claim 8.

10. The all-solid-state battery according to claim 9, characterized in that: The solid electrolyte is a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, or a polymer solid electrolyte; Preferably, its capacity retention rate is higher than 80% when operating under low external pressure conditions not exceeding 2 MPa for 500 cycles.

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