Preparation method of solid-state battery with doped silicon-based negative electrode

Abstract

The invention discloses a preparation method of a solid-state battery with a doped silicon-based negative electrode. The preparation method comprises the following steps: (1) preparing a porous nano silicon core; (2) preparing alloy powder; (3) preparing a solid-state electrolyte; the negative electrode plate has a Si-Ge-N-B quaternary alloy gradient structure, the surface enrichment degree of the B element is 2-3 times that of the interior of the alloy powder, N forms Si-N bonds with high bond energy, the reaction rate of Si and S < 2-> is reduced by 90% or above, a Li-Si-S insulating phase is not likely to be generated, interface impedance is reduced, a solid electrolyte structure adopts a Li3PS4-Li2O-Li3BO3-LiI synergistic system, and therefore the solid electrolyte structure has the advantages that the solid electrolyte structure is stable, and the service life of the solid electrolyte structure is prolonged. Li3BO3 and B of the negative plate form a B-O-B bonding layer, so that the bonding strength is greatly improved, the B-O-B bonding layer effectively prevents generation of microcracks, and Ge alloying is utilized to improve the conductivity and realize synchronous optimization of the interface and the conductivity.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a method for preparing a solid-state battery with a doped silicon-based anode. Background Technology

[0002] High-energy-density solid-state batteries are a core technology for overcoming "range anxiety" in new energy vehicles, and silicon-based anodes, with their ultra-high theoretical specific capacity of 3500-4200 mAh / g, are key to improving battery energy density. However, the interface problem between silicon-based anodes and solid electrolytes restricts their application: firstly, silicon has high surface chemical activity, easily reacting with sulfur in sulfide electrolytes. 2- The reaction generates a low-conductivity Li-Si-S phase, leading to a sharp increase in interfacial impedance; secondly, the interfacial adhesion between silicon and electrolyte is poor, and interfacial peeling occurs due to volume expansion during charging and discharging; thirdly, silicon has low intrinsic conductivity, and relying solely on external conductive agents cannot achieve the coordinated transport of electrons and ions.

[0003] Existing silicon-based anode and solid-state electrolyte matching technologies have significant optimization blind spots: While the Si-Ge binary alloy anode disclosed in patent CN116015243A increases the electronic conductivity to 5×10⁻⁶, it still faces significant limitations. -3 S / cm, but because NB doping was not introduced to regulate the surface chemical state, the Si-Si bonds on the silicon surface easily react with S after contact with Li3PS4 electrolyte. 2- The reaction produces a Li-Si-S insulating phase up to 40 nm thick, resulting in an interfacial impedance as high as 150 Ω·cm. 2 The capacity retention rate after 50 cycles is only 78%; patent CN115863729A uses a single boron-doped silicon anode but does not specifically design the electrolyte formulation, so the interfacial anchoring effect of boron cannot be released, the interfacial adhesion strength is only 5MPa, and interfacial peeling is prone to occur during charge-discharge cycles; the Li3PS4-Li3BO3 electrolyte disclosed in patent CN114979651A, due to the lack of doping modification of silicon-based anodes, has a low BO3 content in Li3BO3. 3- Lacking reaction targets, the electrolyte-electrode interface contact angle reaches 65°, resulting in extremely poor compatibility and a capacity retention rate of only 72% after 100 cycles. It is evident that existing technologies have failed to achieve synergistic design between "silicon-based anode doping" and "solid-state electrolyte formulation," and cannot simultaneously address the three core issues of poor interfacial reactivity, low adhesion, and low conductivity through doping elements. Therefore, it is necessary to propose a new approach to improve upon these problems. Summary of the Invention

[0004] In view of this, the present invention addresses the deficiencies of the prior art, and its main objective is to provide a method for preparing a solid-state battery with a doped silicon-based anode, which can effectively solve the problems of poor interfacial reactivity, low adhesion and low conductivity that existing silicon anode solid-state batteries doped with other elements cannot simultaneously solve.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for fabricating a solid-state battery with a doped silicon-based anode includes the following steps:

[0007] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 2-5h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 8-10h to obtain porous nano-silicon cores.

[0008] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) are mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of porous nano-silicon cores to Ge powder and BN powder is (82-91):(7-13):(1.5-5.5). The furnace is evacuated to a vacuum of 3×10⁻⁶. -4 Pa, inert gas is introduced, and the temperature is raised to 1500-2000℃ at a heating rate of 10℃ / min, held for 2-5h, and cooled to obtain a mixture. The mixture is then placed in a high-energy ball mill for ball milling with a ball-to-material ratio of 20:1, a ball milling speed of 350r / min, and a ball milling time of 5h to obtain alloy powder.

[0009] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was (65-80):(5-15):(8-18):(2-7), the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 1-4 h to obtain a solid electrolyte.

[0010] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder, with 8-9.5g of alloy powder and 0.5-2g of binder. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 12-15h. The negative electrode is obtained by rolling. The negative electrode, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.5-1h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0011] As a preferred embodiment, the purity of the industrial silicon powder is greater than 99.5%, and the purity of the Ge powder is 99.9%.

[0012] As a preferred embodiment, in step (1), the concentration of the hydrofluoric acid is 4 mol / L.

[0013] As a preferred embodiment, in step (1), the porous nano-silicon core has a particle size of 20-35 nm and a porosity of 42%.

[0014] As a preferred option, in step (2), the inert gas is argon.

[0015] As a preferred embodiment, in step (2), the enrichment of element B on the surface of the alloy powder is 2.5 times that inside the alloy powder.

[0016] As a preferred embodiment, in step (3), the Li3PS4 is prepared by a mechanochemical method and the Li3BO3 is prepared by a sol-gel method.

[0017] As a preferred embodiment, the Li3BO3 is prepared by hydrolysis, condensation and calcination of boric acid and lithium hydroxide as raw materials, and the particle size of Li3BO3 is 20nm.

[0018] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0019] The negative electrode in this invention application has a Si-Ge-NB quaternary alloy gradient structure, and the surface enrichment of boron is 2-3 times that inside the alloy powder. Nitrogen forms high-energy Si-N bonds, which bind Si and S. 2-The reaction rate is reduced by more than 90%, making it less likely to form a Li-Si-S insulating phase and reducing interfacial impedance. Furthermore, the solid electrolyte structure adopts a Li3PS4-Li2O-Li3BO3-LiI synergistic system, where Li3BO3 forms a BOB bond layer with the B of the negative electrode, significantly improving the bonding strength. The BOB bond layer effectively prevents the generation of microcracks. Additionally, Ge alloying is used to improve conductivity, achieving simultaneous optimization of interface and conductivity performance.

[0020] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to several embodiments. Detailed Implementation

[0021] This invention discloses a method for preparing a solid-state battery with a doped silicon-based anode, comprising the following steps:

[0022] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 2-5h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 8-10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0023] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) are mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of porous nano-silicon cores to Ge powder and BN powder is (82-91):(7-13):(1.5-5.5). The furnace is evacuated to a vacuum of 3×10⁻⁶. -4 Pa is introduced with inert gas, and the temperature is raised to 1500-2000℃ at a heating rate of 10℃ / min, held for 2-5 hours, and cooled to obtain a mixture. The mixture is then placed in a high-energy ball mill for ball milling at a ball-to-material ratio of 20:1, a milling speed of 350 r / min, and a milling time of 5 hours to obtain alloy powder. The purity of the Ge powder is 99.9%, the inert gas is argon, and the enrichment of B element on the surface of the alloy powder is 2.5 times that inside the alloy powder.

[0024] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was (65-80):(5-15):(8-18):(2-7), the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 1-4 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, condensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0025] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder, with 8-9.5g of alloy powder and 0.5-2g of binder. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 12-15h. The negative electrode is obtained by rolling. The negative electrode, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.5-1h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0026] The following detailed description is provided in conjunction with several embodiments and comparative examples.

[0027] Example 1

[0028] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0029] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 88.4:8:3.6. The furnace was evacuated to a vacuum of 3×10⁻⁶.-4 Pa was introduced with inert gas, and the temperature was increased to 1750℃ at a heating rate of 10℃ / min, held for 3.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350r / min, and ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0030] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 72:10:12:6, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 2 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, polycondensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0031] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 15h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0032] Example 2

[0033] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0034] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 90.2:8:1.8. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1750℃ at a heating rate of 10℃ / min, held for 3.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350r / min, and ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0035] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 80:5:8:7, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 2 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, polycondensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0036] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 15h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0037] Example 3

[0038] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0039] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 83.6:12:5.4. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1750℃ at a heating rate of 10℃ / min, held for 3.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350r / min, and ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0040] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 65:15:18:2, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 2 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, polycondensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0041] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 15h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0042] Example 4

[0043] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 2h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 8h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0044] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 91:8:1.5. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1500℃ at a heating rate of 10℃ / min, held for 5 hours, and then cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350 r / min, and ball milling time of 5 hours to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0045] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 72:6:18:3, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 4 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, polycondensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0046] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder, with 9g of alloy powder and 1g of binder. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 12h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 1h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0047] Example 5

[0048] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 5h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 9h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0049] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) are mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of porous nano-silicon cores to Ge powder and BN powder is 85:10:3. The furnace is then evacuated to a vacuum of 3×10⁻⁶. -4Pa was introduced with inert gas, and the temperature was increased to 2000℃ at a heating rate of 10℃ / min, held for 3 hours, and then cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350 r / min, and ball milling time of 5 hours to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0050] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 80:12:13:5, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 1 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, condensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0051] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder, with 8g of alloy powder and 1g of binder. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 12h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 1h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0052] Example 6

[0053] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 4h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 9h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0054] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 86:8.5:3.5. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1700℃ at a heating rate of 10℃ / min, held for 2.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350r / min, and ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0055] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 68:13:11:4, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 3 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, condensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0056] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated on copper foil and placed in a vacuum drying oven. It is vacuum dried at 120℃ for 13h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.8h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0057] Comparative Example 1

[0058] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0059] (2) Preparation of solid electrolyte: The ball-to-powder ratio of Li3PS4 was 20:1, the ball milling speed was 350 r / min, the ball milling time was 12 h, and the powder was obtained. The powder was placed in a mold and hot-pressed using a hot press at a temperature of 220℃, a pressure of 2 MPa, and a annealing time of 2 h to obtain solid electrolyte; the Li3PS4 was prepared by mechanochemical method.

[0060] (3) Preparation of solid-state battery: The porous nano-silicon cores obtained in step (1) are mixed with a binder. The porous nano-silicon cores are 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is vacuum dried at 120℃ for 15h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0061] Comparative Example 2

[0062] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0063] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder, and then placed in a vacuum induction furnace. The mass ratio of porous nano-silicon cores to Ge powder was 88.4:8. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1750℃ at a heating rate of 10℃ / min, held for 3.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill for ball milling at a ball-to-material ratio of 20:1, a ball milling speed of 350r / min, and a ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, and the inert gas was argon.

[0064] (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was 72:10:12:6, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 2 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method, and the Li3BO3 was prepared by a sol-gel method. Specifically, the Li3BO3 was prepared by hydrolysis, polycondensation and calcination of boric acid and lithium hydroxide as raw materials. The particle size of Li3BO3 was 20 nm.

[0065] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is vacuum dried at 120℃ for 15h and then rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0066] Comparative Example 3

[0067] (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 3h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 10h to obtain porous nano-silicon cores. The purity of the industrial silicon powder was greater than 99.5%, the concentration of the hydrofluoric acid was 4mol / L, the particle size of the porous nano-silicon cores was 20-35nm, and its porosity was 42%.

[0068] (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) were mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of the porous nano-silicon cores to Ge powder and BN powder was 88.4:8:3.6. The furnace was evacuated to a vacuum of 3×10⁻⁶. -4 Pa was introduced with inert gas, and the temperature was increased to 1750℃ at a heating rate of 10℃ / min, held for 3.5h, and cooled to obtain a mixture. The mixture was then placed in a high-energy ball mill and ball-to-material ratio of 20:1, ball milling speed of 350r / min, and ball milling time of 5h to obtain alloy powder. The purity of the Ge powder was 99.9%, the inert gas was argon, and the enrichment of B element on the surface of the alloy powder was 2.5 times that inside the alloy powder.

[0069] (3) Preparation of solid electrolyte: Li3PS4, Li2O and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O and LiI was 72:10:6, the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed with a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa and the hot pressing annealing time was 2 h to obtain a solid electrolyte. The Li3PS4 was prepared by a mechanochemical method.

[0070] (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder. The alloy powder is 9.5g and the binder is 0.5g. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 15h and rolled to obtain a negative electrode sheet. The negative electrode sheet, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.65h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

[0071] Performance tests were conducted on the above embodiments and comparative examples, and the test results are shown in Table 1.

[0072] Table 1

[0073] Analysis of the above data sets shows that Examples 1-6 all exhibit high conductivity and low interfacial impedance, maintaining a good capacity retention rate and high bonding strength. Comparing Example 1 with Comparative Example 1, Comparative Example 1 uses only porous nano-silicon as the negative electrode material, combined with a single Li3PS4, lacking an alloy gradient structure and thus failing to form a structure that reduces the Si and S content. 2- The reaction rate was too high, resulting in the formation of a Li-Si-S insulating phase, leading to extremely high interfacial impedance and very low capacity retention. Comparing Example 1, Comparative Example 1, and Comparative Example 2, Comparative Example 2 used the same composite solid electrolyte as Example 1, significantly improving interfacial bonding strength and preventing surface cracking of the electrolyte, thus increasing capacity retention. Simultaneously, the addition of Ge powder to the negative electrode greatly improved conductivity. Although still far from that of Example 1 in terms of conductivity, it was more than ten times higher than that of Comparative Example 1. Furthermore, comparing Example 1 and Example 3, Example 3 used the same negative electrode as the examples. The electrode was prepared to achieve the same conductivity as in Example 1, but its composite electrolyte lacked Li3BO3, and the B in the negative electrode could not form a BOB bond layer with Li3BO3. Although the composite electrolyte had good interfacial bonding strength and low interfacial resistance, its interfacial bonding strength was relatively weak, making it difficult to prevent the generation of microcracks and not significantly improving the capacity retention rate. In addition, its interfacial resistance was also relatively high, further reducing the cycle performance. Ultimately, the capacity retention rate of Comparative Example 3 was only 80% of that of Example 1. It can be seen that the solid-state battery prepared by the preparation method of this invention has excellent performance and has achieved significant progress.

[0074] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a solid-state battery with a doped silicon-based anode, characterized in that: It includes the following steps: (1) Preparation of porous nano-silicon cores: 10g of industrial silicon powder was placed in a planetary ball mill for ball milling. The ball-to-material ratio was 15:1, the ball milling speed was 400r / min, and the ball milling time was 6h to obtain silicon powder. The silicon powder was added to hydrofluoric acid solution and stirred and etched at room temperature for 2-5h. Then, it was washed with deionized water until pH=7, and then transferred to a vacuum drying oven and vacuum dried at 80℃ for 8-10h to obtain porous nano-silicon cores. (2) Preparation of alloy powder: The porous nano-silicon cores obtained in step (1) are mixed evenly with Ge powder and BN powder, and then placed in a vacuum induction furnace. The mass ratio of porous nano-silicon cores to Ge powder and BN powder is (82-91):(7-13):(1.5-5.5). The furnace is evacuated to a vacuum of 3×10⁻⁶. -4 Pa, inert gas is introduced, and the temperature is raised to 1500-2000℃ at a heating rate of 10℃ / min, held for 2-5h, and cooled to obtain a mixture. The mixture is then placed in a high-energy ball mill for ball milling with a ball-to-material ratio of 20:1, a ball milling speed of 350r / min, and a ball milling time of 5h to obtain alloy powder. (3) Preparation of solid electrolyte: Li3PS4, Li2O, Li3BO3 and LiI were placed in a high-energy ball mill and ball milled. The mass ratio of Li3PS4, Li2O, Li3BO3 and LiI was (65-80):(5-15):(8-18):(2-7), the ball-to-material ratio was 20:1, the ball milling speed was 350 r / min, and the ball milling time was 12 h to obtain a mixed powder. The mixed powder was placed in a mold and hot-pressed using a hot press. The hot pressing temperature was 220℃, the hot pressing pressure was 2 MPa, and the hot pressing annealing time was 1-4 h to obtain a solid electrolyte. (4) Preparation of solid-state battery: The alloy powder obtained in step (2) is mixed with a binder, with 8-9.5g of alloy powder and 0.5-2g of binder. 15mL of N-methylpyrrolidone is added and stirred to form a slurry. The slurry is coated onto copper foil and placed in a vacuum drying oven. It is then vacuum dried at 120℃ for 12-15h. The negative electrode is obtained by rolling. The negative electrode, solid electrolyte layer, and LiNi are then combined. 0.8 Co 0.1 Mn 0.1 O2 positive electrode sheets are stacked sequentially and placed in a hot pressing mold. The temperature is increased to 210°C at a heating rate of 5°C / min, the hot pressing stress is 30MPa, and the hot pressing time is 0.5-1h. After cooling in the furnace, the cells are encapsulated in an aluminum-plastic film to obtain a solid-state battery.

2. The method for preparing a solid-state battery with a doped silicon-based anode according to claim 1, characterized in that: The industrial silicon powder has a purity greater than 99.5%, and the Ge powder has a purity of 99.9%.

3. The method for preparing a solid-state battery with a doped silicon-based anode according to claim 1, characterized in that: In step (1), the concentration of the hydrofluoric acid is 4 mol / L.

4. The method for preparing a solid-state battery with a doped silicon-based anode according to claim 1, characterized in that: In step (1), the porous nano-silicon core has a particle size of 20-35 nm and a porosity of 42%.

5. The method for preparing a solid-state battery with a doped silicon-based anode according to claim 1, characterized in that: In step (2), the inert gas is argon.

6. The method for preparing a solid-state battery with a doped silicon-based negative electrode according to claim 1, characterized in that: In step (2), the enrichment of element B on the surface of the alloy powder is 2.5 times that inside the alloy powder.

7. The method for preparing a solid-state battery with a doped silicon-based negative electrode according to claim 1, characterized in that: In step (3), the Li3PS4 is prepared by mechanochemical method and the Li3BO3 is prepared by sol-gel method.

8. The method for preparing a solid-state battery with a doped silicon-based negative electrode according to claim 7, characterized in that: The Li3BO3 is prepared by hydrolysis, condensation and calcination of boric acid and lithium hydroxide as raw materials, and the particle size of Li3BO3 is 20nm.

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