Process for the production of a solid-state battery anode

Abstract

This invention belongs to the field of solid-state battery technology and discloses a solid-state battery anode preparation process, including: high-entropy MXene and boron-fluorine co-doped modified silicon-based active material, preparation of TiS2 / TiO2 / graphene heterostructure interface modification layer, preparation of composite slurry by PDA-modified CMC binder, combined with plasma pretreatment, coating and drying, sintering and segmented rolling, etc. This invention solves the problems of poor conductivity, large volume expansion, high interface impedance and poor cycle stability of silicon-based solid-state battery anodes in the prior art, and is suitable for the industrial production of high-performance solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to a solid-state battery anode preparation process. Background Technology

[0002] Solid-state batteries, with their advantages of high energy density, high safety, and wide operating temperature range, are considered one of the core development directions for next-generation electrochemical energy storage devices. As a key component of solid-state batteries, the performance of the anode directly determines the battery's cycle stability, rate performance, and energy density. Currently, silicon-based materials are the preferred active material for solid-state battery anodes due to their extremely high theoretical specific capacity (4200 mAh / g). However, silicon-based materials experience severe volume expansion during charge and discharge (expansion rate can reach over 300%), which easily leads to electrode cracking and pulverization. Simultaneously, a lithium-phobic Li₂CO₃ passivation layer easily forms on the surface of silicon-based materials. This passivation layer significantly increases the interfacial impedance between the anode and the solid electrolyte, hindering lithium-ion transport and severely deteriorating the battery's electrochemical performance.

[0003] To address the above problems, existing technologies have proposed several improvement solutions: Firstly, carbon-coated silicon-based materials can alleviate volume expansion, but the interfacial compatibility between the carbon layer and the solid electrolyte is poor, and the interfacial problem caused by Li2CO3 still cannot be solved. Secondly, although using a single metal oxide (such as TiO2) for interface modification can improve interface compatibility to a certain extent, the ion conduction capacity of a single oxide is limited, and its binding force with the negative electrode active material is weak, making it easy to fall off after long-term cycling. Third, when using conventional binders (such as PVDF and pure CMC) to prepare electrodes, the bonding force between the binder and the active material and current collector is insufficient, making it difficult to adapt to the volume expansion of silicon-based materials, resulting in poor cycle stability of the electrodes.

[0004] Therefore, developing a solid-state battery anode fabrication process that can simultaneously address the volume expansion of silicon-based materials, the Li2CO3 interface barrier, and the synergistic optimization of each step has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] This invention aims to provide a solid-state battery anode fabrication process, addressing the problems in existing solid-state battery anode fabrication processes, such as severe volume expansion of silicon-based active materials leading to electrode cracking and pulverization, increased interfacial impedance due to the lithium-phobic Li2CO3 passivation layer on the anode surface hindering lithium-ion transport, poor synergy among active materials, conductive agents, binders, and solid electrolytes, weak bonding between the interface modification layer and the anode and solid electrolyte, and easy failure after long-term cycling.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The technical solution provided by this invention is: A solid-state battery anode fabrication process includes the following steps: S1: Pretreatment of negative electrode active material: Silicon-based active material, carbon source and high-entropy MXene powder are mixed at a mass ratio of (70~80):(15~20):(5~10), and a boron source compound accounting for 2%~5% of the mass of silicon-based active material is added simultaneously. The mixture is placed in an inert gas atmosphere and first heated to 400~450℃ at a heating rate of 5~8℃ / min and held for 2~3h, and then heated to 650~700℃ and held for 1~2h to obtain modified silicon-based composite active material. During the pretreatment process, a fluorine-containing inert gas with a flow rate of 10~20sccm is simultaneously introduced to carry out surface fluorination modification. The high-entropy MXene is TiVNbMoC3 with an interlayer spacing of 0.9~1.2nm and a specific surface area ≥200m² / g.

[0007] S2: Preparation of solid electrolyte dispersion: The sulfide solid electrolyte, dispersant and anhydrous ethanol are mixed at a mass ratio of 1:(0.05~0.1):(8~12), placed in an ultrasonic dispersion device and dispersed at a frequency of 20~30kHz for 30~40min. Then, lithium salt accounting for 5%~8% of the mass of the sulfide solid electrolyte is added and stirred until completely dissolved to obtain the solid electrolyte dispersion.

[0008] S3: Preparation of composite slurry: The modified silicon-based composite active material, conductive agent, and polydopamine (PDA) modified sodium carboxymethyl cellulose (CMC) binder obtained in S1 are mixed at a mass ratio of (70~80):(10~15):(5~10), and the solid electrolyte dispersion prepared in S2 is added. The solid content of the slurry is adjusted to 30%~40%, and the mixture is stirred for 60~90 min using a dual planetary mixer to obtain a uniform negative electrode composite slurry. The PDA modified CMC binder is prepared by self-polymerization of dopamine hydrochloride in Tris-HCl buffer and then composited with CMC.

[0009] S4: Forming and pre-drying: The composite slurry of S3 is coated onto the surface of the copper foil current collector to form a wet film. It is first left to stand at room temperature for 1-2 hours, and then placed in a vacuum drying oven at 40-50℃ for 4-6 hours to remove most of the solvent.

[0010] S5: Interface Modification and Sintering: The pre-dried negative electrode sheet is placed in a plasma treatment device and subjected to plasma treatment with an argon-oxygen mixed gas (volume ratio 9:1) for 5-10 min to remove some lithium-phobic Li2CO3 from the electrode surface; then a TiS2 / TiO2 / graphene heterostructure dispersion is prepared and coated on the electrode surface to form a composite interface modification layer with a thickness of 80-150 nm; the modified electrode sheet is placed in a sintering furnace under inert gas protection and heated to 300-350℃ at a heating rate of 2-3℃ / min and held for 3-4 h, and then naturally cooled to room temperature.

[0011] S6: Post-treatment: Roll pressing is performed on the sintered negative electrode sheet to control the compaction density of the electrode sheet to be 1.6~1.8 g / cm³. 3 The solid-state battery anode is then vacuum-sealed to obtain the finished product.

[0012] Furthermore, the silicon-based active material described in S1 is nano-silicon particles with a particle size of 50~200nm; the carbon source is at least one of natural graphite and hard carbon; the fluorine-containing inert gas is a mixture of sulfur hexafluoride and argon, wherein the volume percentage of sulfur hexafluoride is 5%~10%; and the boron source compound is boric acid or sodium borohydride.

[0013] Furthermore, the sulfide solid electrolyte in S2 is Li 10 GeP2S 12 Li4P3S 11 One of the following; the dispersant is at least one of polyethylene glycol and polyvinylpyrrolidone; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0014] Further, the conductive agent mentioned in S3 is at least one of superconducting carbon black and carbon nanotubes; the preparation process of PDA-modified CMC binder is as follows: dopamine hydrochloride is dissolved in Tris-HCl buffer solution at pH=8.5, stirred for 24h in an aerobic and light-protected environment to obtain PDA solution, then CMC powder is added, and stirred at 75℃ for 4h to form a uniform viscous liquid, wherein the mass ratio of PDA to CMC is (0.05:1)~(0.2:1).

[0015] Furthermore, the coating method described in S4 is blade coating or slot extrusion coating, with a wet film thickness of 150~250μm; the copper foil current collector thickness is 8~12μm, and the surface is subjected to electrochemical roughening treatment.

[0016] Further, the plasma treatment power in S5 is 100~150W, and the vacuum degree is 0.1~0.3Pa; the preparation steps of the TiS2 / TiO2 / graphene heterostructure dispersion are as follows: TiO2 nanoparticles, TiS2 nanosheets and graphene are mixed at a mass ratio of (2:1:1)~(3:1:1), anhydrous ethanol is added, and ultrasonic dispersion is performed at a frequency of 25~30kHz for 40~60min to obtain a dispersion with a concentration of 5~10mg / mL; the thickness of TiS2 nanosheets is 5~10nm, and the lateral size is 200~500nm; the coating method is spin coating or spray coating, and after coating, it is dried at 80~100℃ for 1~2h.

[0017] Furthermore, the rolling process described in S6 adopts a segmented rolling method, with the first segment rolling pressure being 5~8MPa and the second segment rolling pressure being 12~15MPa; the vacuum degree of vacuum packaging is ≤1Pa, and the packaging temperature is 25~30℃.

[0018] Furthermore, the inert gas is nitrogen or argon with a purity ≥99.999%; during the high-entropy MXene composite and sintering process, the inert gas flow rate is controlled at 50~100 sccm.

[0019] The beneficial effects of this technical solution are: (1) High-entropy MXene TiVNbMoC3 and boron-fluorine co-doping form a core modification system, highlighting the synergistic advantages of the components. High-entropy MXene itself has a unique layered structure and excellent conductivity, which can build a continuous conductive network inside the active material. Its interlayer voids can also provide sufficient buffer space for the volume change of silicon-based materials. The co-doping characteristics of boron-fluorine elements can further optimize the electronic structure of the surface of the active material, improve the electronic conduction efficiency and lithium-ion migration ability, and at the same time, can specifically suppress the formation of interface by-products such as Li2CO3, making up for the limitations of single-component modification in performance improvement.

[0020] (2) The TiS2 / TiO2 / graphene heterostructure constitutes a highly efficient interface modification composition, which significantly improves interface compatibility. Among them, TiO2 has strong adsorption properties and can accurately anchor the residual Li2CO3 on the electrode surface; TiS2 itself has high lithium-ion conductivity and can build a fast ion transport channel; graphene enhances the overall performance of the modification layer with its excellent conductivity and structural stability. The heterostructure formed by the three integrates the core advantages of different components. Compared with the modification of single oxide or carbon materials, it is more suitable for the interface requirements of solid-state batteries and reduces the interface transport resistance.

[0021] (3) PDA-modified CMC binder optimizes the bonding effect of electrode components and improves the overall structural stability. The amino and hydroxyl functional groups contained in PDA molecules can form strong interactions with silicon-based active materials and copper foil current collectors, enhancing the bonding strength between various components. At the same time, PDA has good lithium affinity, which can improve the interfacial affinity between the binder and the electrolyte and active materials. Combined with the bonding properties of CMC itself, it solves the problems of poor compatibility and insufficient bonding force between conventional binders and highly active silicon-based materials, providing a core component guarantee for the stability of the electrode structure. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation process of a solid-state battery anode proposed in this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0024] The specific implementation process is as follows: Example 1:

[0025] Please see Figure 1 The present invention provides a technical solution: a solid-state battery anode preparation process. This embodiment uses the following process to prepare the solid-state battery anode, with each component calculated by actual weight (g): S1: Pretreatment of negative electrode active material: Take 75g of nano-silicon particles (particle size 100nm), 18g of natural graphite, and 7g of high-entropy MXene TiVNbMoC3 and mix them. Simultaneously add 2.25g of boric acid (accounting for 3% of the mass of nano-silicon particles), place it in an argon atmosphere (purity 99.999%, flow rate 80sccm), heat it to 420℃ at a heating rate of 6℃ / min and hold it for 2.5h, then heat it to 680℃ and hold it for 1.5h. During the pretreatment process, simultaneously introduce a fluorine-containing inert gas (sulfur hexafluoride volume percentage 8%, the remainder is argon) with a flow rate of 15sccm to carry out surface fluorination modification, and obtain modified silicon-based composite active material.

[0026] S2: Preparation of solid electrolyte dispersion: Take 10g of Li7P3S 11 A sulfide solid electrolyte, 0.7 g of polyethylene glycol, and 90 g of anhydrous ethanol were mixed and placed in an ultrasonic dispersion device. The mixture was dispersed at a frequency of 25 kHz for 35 min, and then 0.6 g of LiTFSI (containing Li7P3S) was added. 11Add 6% (by mass) and stir until completely dissolved to obtain a solid electrolyte dispersion.

[0027] S3: Preparation of composite slurry: First, prepare polydopamine (PDA) modified sodium carboxymethyl cellulose (CMC) binder: Dissolve 0.1g of dopamine hydrochloride in 100g of Tris-HCl buffer solution with pH=8.5, stir for 24h in an aerobic and light-protected environment to obtain PDA solution, then add 1g of CMC powder, stir at 75℃ for 4h to form a uniform viscous liquid (PDA to CMC mass ratio 0.1:1); Take 75g of the modified silicon-based composite active material prepared in S1, 12g of superconducting carbon black, and 8g of the above PDA modified CMC binder and mix them together, add the solid electrolyte dispersion prepared in S2, adjust the solid content of the slurry to 35%, and stir with a double planetary mixer for 75min to obtain a uniform negative electrode composite slurry.

[0028] S4: Forming and Pre-drying: The composite slurry is coated onto the surface of a 10μm thick electrochemically roughened copper foil using a doctor blade coating method to form a 200μm thick wet film. It is first left to stand at room temperature for 1.5h, and then placed in a vacuum drying oven at 45℃ for 5h to remove most of the solvent.

[0029] S5: Interface Modification and Sintering: The pre-dried negative electrode sheet was placed in a plasma treatment device with a power of 120W and a vacuum of 0.2Pa. The plasma was treated for 8 minutes using an argon-oxygen mixed gas (volume ratio 9:1). Subsequently, a TiS2 / TiO2 / graphene heterostructure dispersion was prepared: 4g of TiO2 nanoparticles, 2g of TiS2 nanosheets, and 2g of graphene were mixed and 800g of anhydrous ethanol was added. The mixture was ultrasonically dispersed at a frequency of 28kHz for 50 minutes to obtain a dispersion with a concentration of 8mg / mL. The dispersion was then coated onto the electrode surface by spin coating to form a 120nm thick composite interface modification layer. After coating, the electrode sheet was dried at 90℃ for 1.5h. The modified electrode sheet was placed in a sintering furnace protected by an argon atmosphere (purity 99.999%, flow rate 80sccm) and heated to 320℃ at a heating rate of 2.5℃ / min. The temperature was then held for 3.5h and allowed to cool naturally to room temperature.

[0030] S6: Post-processing: The sintered negative electrode sheet is subjected to segmented rolling. The rolling pressure of the first segment is 6 MPa, and the rolling pressure of the second segment is 13 MPa, controlling the compaction density of the electrode sheet to be 1.7 g / cm³. 3 Subsequently, vacuum encapsulation was performed at a vacuum level of 0.8 Pa and a temperature of 28 °C to obtain the solid-state battery anode product.

[0031] The data in the table above clearly present the core performance indicators of the solid-state battery anode prepared in Example 1: the interface impedance is as low as 85Ω, indicating that after the synergistic modification of high-entropy MXene and boron-fluorine co-doping, the interface modification of TiS2 / TiO2 / graphene heterostructure, and plasma pretreatment, the interfacial compatibility between the anode and the solid electrolyte is significantly improved, effectively reducing the lithium-ion transport resistance; after 1000 cycles at a conventional current density of 0.2C, the capacity retention rate is still 82%, demonstrating that the electrode has excellent cycle stability, which is due to the internal bonding force of the electrode enhanced by PDA-modified CMC binder and the volume buffering effect provided by high-entropy MXene; the electrode volume expansion rate during charge and discharge is only 85%, which is much lower than the conventional expansion rate of silicon-based materials (above 300%), proving that the multi-stage synergistic modification scheme of this example can effectively suppress the volume expansion of silicon-based materials and avoid electrode cracking and pulverization. Example 2:

[0032] Please see Figure 1 This invention provides a technical solution: a solid-state battery anode preparation process. In this embodiment, the amount of high-entropy MXene TiVNbMoC3 and the type of boron source are adjusted, while the remaining process parameters are the same as in Example 1. The components are calculated by actual weight (g): S1: Pretreatment of negative electrode active material: Take 70g of nano-silicon particles (particle size 100nm), 20g of hard carbon, and 10g of high-entropy MXeneTiVNbMoC3 and mix them together. Simultaneously add 3.5g of sodium borohydride (accounting for 5% of the mass of nano-silicon particles), place it in an argon atmosphere (purity 99.999%, flow rate 100sccm), heat it to 420℃ at a heating rate of 6℃ / min and hold it for 2.5h, then heat it to 680℃ and hold it for 1.5h. During the pretreatment process, simultaneously introduce a fluorine-containing inert gas (sulfur hexafluoride volume percentage 8%, the remainder is argon) with a flow rate of 15sccm to carry out surface fluorination modification, and obtain modified silicon-based composite active material.

[0033] S2~S6: The steps and parameters are completely consistent with those in Example 1, except that the sulfide solid electrolyte used in S2 is Li7P3S. 11 The binder used in S3 is a PDA-modified CMC binder, the interface modification layer used in S5 is a TiS2 / TiO2 / graphene heterostructure, and S6 adopts a segmented rolling method.

[0034] The data in the table above show that the performance of Example 2 is further optimized compared to Example 1: the interface impedance decreased to 82Ω, a reduction of 3Ω compared to Example 1. This is because the reducing properties of sodium borohydride slightly inhibited the formation of Li2CO3 during the modification process, and synergistically improved the interface compatibility with fluorination modification; the capacity retention rate after 1000 cycles at 0.2C increased to 85%, indicating better electrode cycling stability; the volume expansion rate was as low as 78%, a reduction of 7% compared to Example 1. The core reason is that after increasing the amount of high-entropy MXene TiVNbMoC3 to 10g, its layered structure provided more sufficient volume buffer space, and the conductive network was more complete, further suppressing electrode expansion and performance degradation. All data demonstrate that after adjusting the amount of high-entropy MXene and the type of boron source, this process can still achieve excellent anode performance, and some indicators are significantly improved. Example 3:

[0035] Please see Figure 1 This invention provides a technical solution: a solid-state battery anode preparation process. In this embodiment, the ratio of TiS2 / TiO2 / graphene heterostructure and the plasma treatment time are adjusted, while the remaining process parameters are the same as in Example 1. The components are calculated by actual weight (g): S1~S4: The steps and parameters are completely consistent with those in Example 1, wherein the high-entropy MXene used in S1 is TiVNbMoC3, and the binder used in S3 is PDA-modified CMC binder.

[0036] S5: Interface Modification and Sintering: The pre-dried negative electrode sheet was placed in a plasma treatment device with a power of 120W and a vacuum of 0.2Pa. The plasma was treated for 10 minutes using an argon-oxygen mixed gas (volume ratio 9:1). Subsequently, a TiS2 / TiO2 / graphene heterostructure dispersion was prepared: 6g of TiO2 nanoparticles, 2g of TiS2 nanosheets, and 2g of graphene were mixed and 800g of anhydrous ethanol was added. The mixture was ultrasonically dispersed at a frequency of 28kHz for 50 minutes to obtain a dispersion with a concentration of 8mg / mL. The dispersion was then coated onto the electrode surface by spin coating to form a 120nm thick composite interface modification layer. After coating, the electrode sheet was dried at 90℃ for 1.5h. The modified electrode sheet was placed in a sintering furnace protected by an argon atmosphere (purity 99.999%, flow rate 80sccm) and heated to 320℃ at a heating rate of 2.5℃ / min. The temperature was then held for 3.5h and allowed to cool naturally to room temperature.

[0037] S6: The steps and parameters are completely consistent with those in Example 1, and the segmented rolling method is adopted.

[0038] The data in the table above highlight the optimization effect of adjusting the ratio of TiS2 / TiO2 / graphene heterostructure and the plasma treatment time: the interfacial impedance is only 78Ω, a decrease of 7Ω compared to Example 1. This is because after extending the plasma treatment time to 10 min, the initial Li2CO3 on the electrode surface is more fully removed, and the increased TiO2 content enhances its adsorption and anchoring ability for residual Li2CO3, significantly reducing the interfacial transport resistance; the capacity retention rate after 1000 cycles at 0.2C is 83%, an increase of 1% compared to Example 1, and the volume expansion rate is 82%, a decrease of 3% compared to Example 1. This indicates that the adjusted heterostructure can still synergize with the high-entropy MXene modification and PDA-modified binder, ensuring the cycling stability and anti-expansion ability of the electrode. The data demonstrate that adjusting the ratio of TiS2 / TiO2 / graphene heterostructure and the plasma treatment time within the scope defined in the claims can further optimize the interfacial performance. Example 4:

[0039] Please see Figure 1 The present invention provides a technical solution: a solid-state battery anode preparation process. In this embodiment, the mass ratio of PDA to CMC and the rolling parameters are adjusted, while the remaining process parameters are the same as in Example 1. Each component is calculated based on its actual weight (g). S1~S2: The steps and parameters are completely consistent with those in Example 1, except that the high-entropy MXene used in S1 is TiVNbMoC3, and the sulfide solid electrolyte used in S2 is Li7P3S. 11 .

[0040] S3: Preparation of composite slurry: When preparing PDA-modified CMC binder, take 0.2g of dopamine hydrochloride and 1g of CMC powder to composite (PDA to CMC mass ratio 0.2:1), and the remaining steps are the same as in Example 1; take 75g of modified silicon-based composite active material prepared in S1, 12g of superconducting carbon black, and 8g of the above PDA-modified CMC binder and mix them, add the solid electrolyte dispersion prepared in S2, adjust the solid content of the slurry to 35%, and stir with a double planetary mixer for 75min to obtain a uniform negative electrode composite slurry.

[0041] S4~S5: The steps and parameters are completely consistent with those in Example 1, wherein the interface modification layer used in S5 is a TiS2 / TiO2 / graphene heterostructure.

[0042] S6: Post-processing: The sintered negative electrode sheet is subjected to segmented rolling. The rolling pressure of the first segment is 8 MPa, and the rolling pressure of the second segment is 15 MPa, controlling the compaction density of the electrode sheet to be 1.8 g / cm³. 3 Subsequently, vacuum encapsulation was performed at a vacuum level of 0.8 Pa and a temperature of 28 °C to obtain the solid-state battery anode product.

[0043] The data in the table above reflects the impact of the PDA to CMC mass ratio and the adjustment of rolling parameters on the negative electrode performance: the interface impedance is 88Ω, slightly higher than Example 1 by 3Ω, because the increased rolling pressure leads to an increase in the electrode compaction density to 1.8 g / cm³. 3 While reducing internal porosity, the interfacial transport resistance slightly increased. After 1000 cycles at 0.2C, the capacity retention rate reached 84%, a 2% improvement compared to Example 1, and the volume expansion rate decreased to 80%, a 5% reduction compared to Example 1. This is primarily due to the increased PDA to CMC mass ratio to 0.2:1, which significantly enhanced the bonding force between the binder, active material, and current collector, resulting in a more stable electrode structure and better adaptation to the volume expansion of silicon-based materials. Data demonstrates that the binder ratio and rolling parameters of this process can be flexibly adjusted according to actual performance requirements, while maintaining excellent overall performance even after adjustment.

[0044] Comparative Example 1: Please see Figure 1 The present invention provides a comparative scheme: This comparative example removes high-entropy MXene TiVNbMoC3, and the remaining process parameters are the same as in Example 1. The components are calculated by actual weight (g): S1: Pretreatment of negative electrode active material: Take 75g of nano-silicon particles (particle size 100nm) and 25g of natural graphite, mix them, add 2.25g of boric acid at the same time, place them in an argon atmosphere, and the subsequent heating and fluorination modification steps are the same as in Example 1 to obtain modified silicon-based composite active material (without high-entropy MXene composite).

[0045] S2~S6: The steps and parameters are completely consistent with those in Example 1, except that the sulfide solid electrolyte used in S2 is Li7P3S. 11 The binder used in S3 is a PDA-modified CMC binder, the interface modification layer used in S5 is a TiS2 / TiO2 / graphene heterostructure, and S6 adopts a segmented rolling method.

[0046] The data in the table above contrasts sharply with those of Example 1: the interface impedance is as high as 152Ω, an increase of 67Ω (78.8%) compared to 85Ω in Example 1. This is because the lack of a continuous conductive network constructed from high-entropy MXene TiVNbMoC3 significantly increases the resistance to electron and ion transport; the capacity retention rate after 1000 cycles at 0.2C is only 58%, a decrease of 24 percentage points (29.3%) compared to 82% in Example 1; the volume expansion rate soars to 142%, an increase of 57 percentage points (67.1%) compared to 85% in Example 1, and significant cracking of the electrode appears after charge and discharge. The data directly demonstrate that the addition of high-entropy MXene TiVNbMoC3 is key to improving the conductivity of the negative electrode and suppressing volume expansion. Its synergistic effect with boron-fluorine co-doping is irreplaceable; its absence leads to a significant deterioration in negative electrode performance.

[0047] Comparative Example 2: Please see Figure 1 The present invention provides a comparative scheme: In this comparative example, the TiS2 / TiO2 / graphene heterostructure is replaced with a single TiO2 layer, and the remaining process parameters are the same as in Example 1. The components are calculated by actual weight (g): S1~S4: The steps and parameters are completely consistent with those in Example 1, wherein the high-entropy MXene used in S1 is TiVNbMoC3, and the binder used in S3 is PDA-modified CMC binder.

[0048] S5: Interface modification and sintering: The plasma treatment steps are the same as in Example 1; then, a TiO2 dispersion is prepared: 8g of TiO2 nanoparticles are added to 800g of anhydrous ethanol and ultrasonically dispersed for 50min to obtain a dispersion with a concentration of 8mg / mL; the dispersion is coated on the electrode surface by spin coating to form a 120nm thick TiO2 layer (without TiS2 and graphene composite), and the subsequent drying and sintering steps are the same as in Example 1.

[0049] S6: The steps and parameters are completely consistent with those in Example 1, and the segmented rolling method is adopted.

[0050] The data in the table above show that after replacing the TiS2 / TiO2 / graphene heterostructure with a single TiO2 layer, the anode performance decreased significantly: the interfacial impedance was 138Ω, an increase of 53Ω (62.4%) compared to 85Ω in Example 1. This is because the ion conduction capacity of a single TiO2 layer is limited and it cannot form a conductive network, leading to increased interfacial transport resistance. The capacity retention rate after 1000 cycles at 0.2C was 65%, a decrease of 17 percentage points (20.7%) compared to 82% in Example 1. The volume expansion rate was 98%, an increase of 13 percentage points (15.3%) compared to 85% in Example 1. The data demonstrate that the synergistic effect of the TiS2 / TiO2 / graphene heterostructure (TiO2 adsorbs Li2CO3, TiS2 accelerates ion transport, and graphene enhances conductivity and stability) is far superior to that of single TiO2 modification, and is one of the core features of this invention in reducing interfacial impedance and improving cycle stability.

[0051] Comparative Example 3: Please see Figure 1 The present invention provides a comparative scheme: This comparative example uses pure CMC binder to replace PDA-modified CMC binder, and the remaining process parameters are the same as in Example 1. The components are calculated by actual weight (g): S1~S2: The steps and parameters are completely consistent with those in Example 1, except that the high-entropy MXene used in S1 is TiVNbMoC3, and the sulfide solid electrolyte used in S2 is Li7P3S. 11 .

[0052] S3: Preparation of composite slurry: Take 75g of the modified silicon-based composite active material prepared in S1, 12g of superconducting carbon black, and 8g of pure CMC binder (without PDA modification) and mix them. Then add solid electrolyte dispersion and stir in the same way as in Example 1.

[0053] S4~S6: The steps and parameters are completely consistent with those in Example 1. The interface modification layer used in S5 is a TiS2 / TiO2 / graphene heterostructure, and S6 adopts a segmented rolling method.

[0054] The data in the table above clearly demonstrates the performance gap between conventional CMC binders and PDA-modified CMC binders: the interfacial impedance is 112Ω, an increase of 27Ω (31.8%) compared to 85Ω in Example 1, indicating that pure CMC has poor lithium affinity and cannot improve interfacial lithium-ion transport; the capacity retention rate after 1000 cycles at 0.2C is only 62%, a decrease of 20 percentage points (24.4%) compared to 82% in Example 1; the volume expansion rate is 115%, an increase of 30 percentage points (35.3%) compared to 85% in Example 1, and significant cracking of the electrode appears after charge and discharge. The data proves that PDA-modified CMC binders can enhance electrode bonding through strong interactions and improve interfacial performance, which is an important guarantee for improving the cycle stability of the negative electrode. Conventional CMC binders cannot meet the performance requirements of this process.

[0055] Comparative Example 4: Please see Figure 1 The present invention provides a comparative scheme: the plasma pretreatment step in S5 is omitted in this comparative example, and the remaining process parameters are the same as in Example 1. Each component is calculated by actual weight (g): S1~S4: The steps and parameters are completely consistent with those in Example 1, except that the high-entropy MXene used in S1 is TiVNbMoC3, the binder used in S3 is PDA-modified CMC binder, and the sulfide solid electrolyte used in S2 is Li7P3S. 11 .

[0056] S5: Interface modification and sintering: TiS2 / TiO2 / graphene heterostructure dispersion was directly prepared and coated on the surface of pre-dried electrode (without plasma pretreatment). The subsequent coating, drying and sintering steps were the same as in Example 1.

[0057] S6: The steps and parameters are completely consistent with those in Example 1, and the segmented rolling method is adopted.

[0058] The data in the table above show that omitting the plasma pretreatment step significantly deteriorates the performance of the negative electrode: the interfacial impedance reaches 145Ω, an increase of 60Ω (70.6%) compared to 85Ω in Example 1. The core reason is that the initial Li2CO3 on the electrode surface was not effectively removed, and even with the subsequent use of a TiS2 / TiO2 / graphene heterostructure modification layer, it is difficult to completely eliminate the interfacial barrier; the capacity retention rate after 1000 cycles at 0.2C is only 60%, a decrease of 22 percentage points (26.8%) compared to 82% in Example 1; the volume expansion rate is 92%, an increase of 7 percentage points (8.2%) compared to 85% in Example 1. The data demonstrate that the synergistic effect of plasma pretreatment and the heterostructure modification layer is key to maximizing the removal and suppression of the negative impact of Li2CO3. Omitting this step leads to a significant decrease in interfacial compatibility, thereby affecting the overall performance of the negative electrode.

[0059] Comparative Example 5: Please see Figure 1 The present invention provides a comparative scheme: using the conventional silicon-based solid-state battery anode preparation process in the prior art, without the use of high-entropy MXene modification, PDA-modified CMC binder, and TiS2 / TiO2 / graphene heterostructure interface modification, the specific steps are as follows (based on actual weight g): 1) Take 75g of nano-silicon particles and 25g of natural graphite, mix them, and keep them at 680℃ for 2h under an argon atmosphere to obtain carbon-coated silicon-based material (boron-free fluorine co-doped and high-entropy MXene composite). 2) Take 10g of Li7P3S 11 0.7g polyethylene glycol and 90g anhydrous ethanol were mixed and ultrasonically dispersed, and 0.6g LiTFSI was added to obtain an electrolyte dispersion. 3) Take 75g of carbon-coated silicon-based material, 12g of superconducting carbon black, and 8g of PVDF binder (without PDA modification), mix them, add electrolyte dispersion, and stir to prepare slurry; 4) Coat the surface of copper foil, vacuum dry at 45℃ for 5 hours, sinter at 320℃ for 3.5 hours, and roll press to a compacted density of 1.7 g / cm³. 3 A negative electrode was obtained (without plasma pretreatment and TiS2 / TiO2 / graphene heterostructure modification).

[0060] The data in the table above shows a significant difference from that of Example 1 of this invention, fully demonstrating the inventiveness of this invention: the interface impedance is as high as 210Ω, an increase of 125Ω compared to 85Ω in Example 1, representing a 147.1% increase. This is because existing technologies lack plasma pretreatment and heterostructure modification, resulting in severe Li2CO3 barriers at the interface and the absence of high-entropy MXene to construct a conductive network; the capacity retention rate after 1000 cycles at 0.2C is only 45%, a decrease of 37 percentage points compared to 82% in Example 1, representing a 45.1% decrease; the volume expansion rate soars to 180%, an increase of 95 percentage points compared to 85% in Example 1, representing a 111.8% increase, and the electrode sheet suffers severe pulverization after charge and discharge. The data demonstrate that the multi-stage synergistic modification process of this invention (high-entropy MXene and boron-fluorine co-doping, PDA-modified binder, plasma + heterostructure interface modification) is significantly different from existing technologies and can greatly improve the overall performance of the solid-state battery anode.

[0061] This technical solution constructs a core component system of "high-entropy MXene and boron-fluorine co-doped modified active material + TiS2 / TiO2 / graphene heterostructure interface modification + PDA-modified CMC binder", and combines it with synergistic processes such as plasma pretreatment to form a solid-state battery anode preparation scheme with excellent conductivity, resistance to volume expansion and interface compatibility. Examples 1-4, representing different parameter adaptations of this technical solution, all exhibit stable and excellent performance: the interface impedance is stably controlled at 78-88Ω, the capacity retention rate after 1000 cycles at 0.2C reaches 82%-85%, and the charge-discharge volume expansion rate is only 78%-85%. Even with adjustments to key parameters such as the amount of high-entropy MXene, the ratio of heterostructures, and the ratio of PDA to CMC, the performance remains highly stable, demonstrating that this solution possesses flexible parameter adaptability and reliable performance reproducibility. The core lies in the precise synergistic effect formed among the components. The layered structure of high-entropy MXene TiVNbMoC3 not only builds a continuous conductive network but also provides volume buffer space. Boron-fluorine co-doping further optimizes the electronic structure and suppresses the generation of by-products. The TiS2 / TiO2 / graphene heterostructure integrates multiple functions such as adsorbing by-products, accelerating ion transport, and stabilizing the structure. The PDA-modified CMC binder strengthens the integrity of the electrode through strong interactions. Each component performs its own function and empowers each other, forming an inseparable innovative system.

[0062] In stark contrast, each comparison, by highlighting the lack of one or more core innovative components, directly exposes the limitations of conventional technologies: In Comparative Example 1, after removing high-entropy MXene, the interface impedance soared to 152Ω, the capacity retention dropped sharply to 58%, and the volume expansion rate exceeded 142%, proving that high-entropy MXene is the core that ensures conductivity and resistance to expansion. Comparative Example 2 uses a single TiO2 to replace the heterostructure, the interface impedance increases to 138Ω, and the capacity retention is only 65%, highlighting the synergistic modification advantage of the heterostructure far exceeding that of the single component; Comparative Example 3 used conventional CMC binder, but the electrode bonding force was insufficient, leading to cracking and a capacity retention rate of 62%, which confirms the necessity of PDA modification to improve structural stability. Comparative Example 4, which omitted plasma pretreatment, showed an interfacial impedance of 145Ω and a capacity retention of only 60%, indicating that the synergistic effect of pretreatment and heterostructure is key to eliminating interfacial barriers.

[0063] Comparative Example 5 uses existing conventional processes without employing any of the core innovative components of this solution. It only prepares the negative electrode through simple carbon coating and PVDF binder. Its interfacial impedance is as high as 210Ω, which is 2.7 times the optimal value of the example. Its capacity retention rate is only 45%, which is less than 60% of that of the example. Its volume expansion rate is 180%, which is 2.3 times that of the example. After charging and discharging, the electrode sheet is severely pulverized. In contrast, this technical solution, through the combination of core components, fundamentally solves the three major pain points of existing silicon-based negative electrodes: poor conductivity, large expansion, and high interfacial resistance. Its performance is significantly improved, which fully demonstrates its outstanding creativity and significant technological progress. It provides a feasible and superior technical path for the industrial preparation of high-performance solid-state battery negative electrodes.

[0064] To further illustrate the beneficial technical effects of the various embodiments of the present invention, relevant performance tests were conducted on Embodiments 1-4 and Comparative Examples 1-5; the test methods are as follows: 1. Sample Preparation: The negative electrode sheets prepared in each embodiment and comparative example were cut into circular samples with a diameter of 14 mm, and compared with Li7P3S. 11 Solid electrolyte sheet (14 mm in diameter, 100 μm in thickness), LiCoO2 cathode sheet (12 mm in diameter, 2.5 mg / cm³ areal density) 2 The CR2032 coin cell solid-state battery was assembled in the order of "positive electrode - solid electrolyte - negative electrode". The assembly process was carried out in an argon atmosphere glove box (the water and oxygen content were both below 0.1 ppm). After assembly, the battery was left to stand for 24 hours for later use.

[0065] 2. AC Impedance Spectroscopy (EIS) Test: The assembled solid-state battery was tested using an electrochemical workstation. The test mode was AC impedance spectroscopy (EIS), and the frequency range was set to 10. -6 ~10 6 The applied AC signal amplitude was 5mV, and the test temperature was room temperature (25℃). Before the test, ensure that the battery was in an open circuit state. The Nyquist plot was obtained through the test, and the value corresponding to the intersection of the high-frequency region and the real axis was read as the battery interface impedance.

[0066] 3. Charge-discharge cycle test: The test is conducted using a battery testing system, with the test voltage range set to 0.01~1.5V (relative to Li / Li). + The current density was 0.2C (1C=3570mAh / g, calculated based on the theoretical capacity of silicon-based active materials), and the test temperature was room temperature (25℃). First, a constant current charge was applied to 1.5V, and then a constant current discharge was applied to 0.01V to complete one charge-discharge cycle. The cycle was repeated 1000 times, and the discharge capacity of each cycle was recorded. The ratio of the discharge capacity of the 1000th cycle to the discharge capacity of the first cycle was calculated as the capacity retention rate after 1000 cycles.

[0067] 4. Volume expansion rate test: A high-precision thickness gauge (accuracy 0.1μm) was used for testing. Before the test, the negative electrode sheet was cut into a 20mm×20mm square sample. The thickness was measured at different positions on the electrode sheet (5 points in total, including the center point and the four sides), and the average value was taken as the electrode sheet thickness before charge and discharge. After assembling the electrode sheet into a battery, 1000 charge and discharge cycles were completed. The battery was disassembled and the electrode sheet was removed. The thickness at the above 5 points was measured again under the same environment (room temperature and dryness), and the average value was taken as the electrode sheet thickness after charge and discharge. The volume expansion rate was calculated as "(average electrode sheet thickness after charge and discharge - average electrode sheet thickness before charge and discharge) / average electrode sheet thickness before charge and discharge × 100%".

[0068] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A process for preparing a solid-state battery anode, characterized in that, Includes the following steps: S1: Pretreatment of negative electrode active material: Silicon-based active material, carbon source and high-entropy MXene powder are mixed in a mass ratio of (70-80):(15-20):(5-10), and a boron source compound accounting for 2%-5% of the mass of silicon-based active material is added simultaneously. The mixture is placed in an inert gas atmosphere, heated to 400-450℃ at a heating rate of 5-8℃ / min and held for 2-3h, and then heated to 650-700℃ and held for 1-2h to obtain modified silicon-based composite active material; During the pretreatment process, a fluorine-containing inert gas with a flow rate of 10-20 sccm is simultaneously introduced to perform surface fluorination modification; the high-entropy MXene is TiVNbMoC3; S2: Preparation of solid electrolyte dispersion: The sulfide solid electrolyte, dispersant and anhydrous ethanol are mixed at a mass ratio of 1:(0.05-0.1):(8-12), placed in an ultrasonic dispersion device and dispersed at a frequency of 20-30kHz for 30-40min. Then, lithium salt accounting for 5%-8% of the mass of the sulfide solid electrolyte is added and stirred until completely dissolved to obtain the solid electrolyte dispersion. S3: Preparation of composite slurry: The modified silicon-based composite active material, conductive agent, and polydopamine (PDA) modified sodium carboxymethyl cellulose (CMC) binder obtained in S1 are mixed at a mass ratio of (70-80):(10-15):(5-10), and the solid electrolyte dispersion prepared in S2 is added. The solid content of the slurry is adjusted to 30%-40%, and the mixture is stirred for 60-90 minutes using a dual planetary mixer to obtain a uniform negative electrode composite slurry. The PDA-modified CMC binder is prepared by self-polymerization of dopamine hydrochloride in Tris-HCl buffer and then composited with CMC, with the PDA mass percentage being 5%-10%. S4: Forming and pre-drying: The composite slurry of S3 is coated onto the surface of the copper foil current collector to form a wet film. First, let it stand at room temperature for 1-2 hours, and then place it in a vacuum drying oven at 40-50℃ for 4-6 hours to dry. S5: Interface Modification and Sintering: The pre-dried negative electrode sheet is placed in a plasma treatment device and subjected to plasma treatment with an argon-oxygen mixed gas (volume ratio 9:1) for 5-10 min to remove some lithium-phobic Li2CO3 from the electrode surface; then a TiS2 / TiO2 / graphene heterostructure dispersion is prepared and coated on the electrode surface to form a composite interface modification layer with a thickness of 80-150 nm; the modified electrode sheet is placed in a sintering furnace under inert gas protection and heated to 300-350℃ at a heating rate of 2-3℃ / min and held for 3-4 h, and then naturally cooled to room temperature; S6: Post-processing: Roll the sintered negative electrode sheet to control the compaction density of the electrode sheet to 1.6-1.8 g / cm³, and then vacuum seal it to obtain the finished solid-state battery negative electrode.

2. The solid-state battery anode fabrication process according to claim 1, characterized in that, The silicon-based active material described in S1 is nano-silicon particles with a particle size of 50-200 nm. The carbon source is at least one of natural graphite and hard carbon; The fluorine-containing inert gas is a mixture of sulfur hexafluoride and argon, wherein the volume percentage of sulfur hexafluoride is 5%-10%. The boron source compound is boric acid or sodium borohydride; The high-entropy MXeneTiVNbMoC3 has an interlayer spacing of 0.9-1.2 nm and a specific surface area ≥200 m². 2 / g.

3. The solid-state battery anode fabrication process according to claim 1, characterized in that, The sulfide solid electrolyte mentioned in S2 is Li 10 GeP2S 12 Li7P3S 11 One of them; The dispersant is at least one of polyethylene glycol and polyvinylpyrrolidone; The lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

4. The solid-state battery anode preparation process according to claim 1, characterized in that, The conductive agent mentioned in S3 is at least one of superconducting carbon black and carbon nanotubes; The preparation process of the polydopamine-modified sodium carboxymethyl cellulose (CMC) binder is as follows: dopamine hydrochloride is dissolved in Tris-HCl buffer solution at pH=8.5, and stirred for 24 hours in an aerobic and light-protected environment to obtain a PDA solution. Then, CMC powder is added, and the mixture is stirred at 75°C for 4 hours until a uniform viscous liquid is formed. The mass ratio of PDA to CMC is (0.05:1) to (0.2:1).

5. The solid-state battery anode fabrication process according to claim 1, characterized in that, The coating method described in S4 is blade coating or slot extrusion coating, and the wet film thickness is 150-250μm; The copper foil current collector has a thickness of 8-12 μm and its surface is treated with electrochemical roughening.

6. The solid-state battery anode fabrication process according to claim 1, characterized in that, The plasma treatment described in S5 has a power of 100-150W and a vacuum degree of 0.1-0.3Pa; The preparation steps of the TiS2 / TiO2 / graphene heterostructure dispersion are as follows: TiO2 nanoparticles, TiS2 nanosheets and graphene are mixed in a mass ratio of (2:1:1)-(3:1:1), anhydrous ethanol is added, and ultrasonic dispersion is carried out at a frequency of 25-30kHz for 40-60min to obtain a dispersion with a concentration of 5-10mg / mL. The TiS2 nanosheets have a thickness of 5-10 nm and a lateral dimension of 200-500 nm. The coating method is spin coating or spray coating. After coating, the nanosheets are dried at 80-100℃ for 1-2 hours before subsequent sintering.

7. The solid-state battery anode fabrication process according to claim 1, characterized in that, The rolling process described in S6 adopts a segmented rolling method, with the first segment rolling pressure being 5-8 MPa and the second segment rolling pressure being 12-15 MPa; the vacuum degree of the vacuum packaging is ≤1 Pa, and the packaging temperature is 25-30℃.

8. The solid-state battery anode fabrication process according to any one of claims 1-7, characterized in that, The inert gas is nitrogen or argon with a purity ≥99.999%; during the high-entropy MXene composite and sintering process, the inert gas flow rate is controlled at 50-100 sccm.

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