Flexible negative electrode paper for solid-state batteries and preparation method and application thereof

Abstract

The application discloses a preparation method of a flexible negative electrode paper for a solid-state battery, and comprises the following steps: (S1) uniformly mixing a nitrogen-containing molecule and a transition metal salt, and then performing catalytic pyrolysis to obtain carbon nanotubes, and then performing physical activation pore forming, silicon deposition and carbon coating to obtain a silicon-carbon negative electrode; (S2) mixing the silicon-carbon negative electrode, a dispersing agent and a solvent I to obtain a silicon-carbon dispersion liquid A; mixing conductive carbon materials, a solid-state electrolyte, a polymer and a solvent II to obtain an electron / ion conductive slurry B; mixing nanocellulose and a solvent III to obtain a fiber dispersion emulsion C; and mixing and dispersing the three to obtain a papermaking slurry; and (S3) coating the papermaking slurry on a substrate, and performing reduction treatment by using an amine group-containing small molecule reducing agent to obtain the flexible negative electrode paper for the solid-state battery. The solid-state battery assembled by using the flexible negative electrode paper prepared by the application has excellent cycle stability, rate performance and low expansion rate, and has high initial efficiency and high capacity.

Description

Technical Field

[0001] This invention belongs to the technical field of solid-state batteries, specifically relating to a flexible negative electrode paper for solid-state batteries, its preparation method, and its application. Background Technology

[0002] Solid-state battery anode materials are currently undergoing rapid development. Lithium metal, with its high theoretical capacity and low potential, is considered the ultimate form of battery anode material, especially for solid-state batteries. However, the formation of lithium dendrites and unstable interfacial contacts hinder the widespread application of lithium metal anodes. Traditional anode materials such as graphite cannot meet the high energy density and long cycle life requirements of solid-state batteries. Therefore, researchers are actively developing new anode materials, among which silicon-carbon anode materials have attracted significant attention.

[0003] Silicon-carbon anode materials have the advantage of high energy density, with a theoretical specific capacity far exceeding that of graphite anodes. However, due to the large volume expansion and relatively low conductivity of nano-silicon particles, research on silicon-carbon materials for solid-state batteries is still ongoing. Summary of the Invention

[0004] To address the aforementioned issues, this invention discloses a method for preparing flexible negative electrode paper for solid-state batteries. Solid-state batteries assembled using the prepared flexible negative electrode paper as the negative electrode exhibit excellent cycle stability, rate performance, and low expansion rate, while also possessing high initial efficiency and high capacity.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing flexible negative electrode paper for solid-state batteries, comprising:

[0007] (S1) Nitrogen-containing molecules are mixed evenly with transition metal salts and carbon nanotubes are obtained by catalytic pyrolysis reaction. Then, porous carbon nanotubes are obtained by physical activation to create pores. Using the porous carbon nanotubes as a substrate, silicon carbon anodes are obtained by silicon deposition and carbon coating in sequence.

[0008] (S2) A silicon-carbon dispersion A is obtained by mixing silicon-carbon anode, dispersant and solvent I; an electronic / ionic conductive slurry B is obtained by mixing conductive carbon material, solid electrolyte, polymer and solvent II; a fiber dispersion emulsion C is obtained by mixing nanocellulose and solvent III; and a papermaking pulp is obtained by mixing and dispersing silicon-carbon dispersion A, electronic / ionic conductive slurry B and fiber dispersion emulsion C.

[0009] The conductive carbon material includes one-dimensional carbon material and optional two-dimensional carbon material.

[0010] (S3) The paper pulp is coated onto a substrate and then reduced by an amine-containing small molecule reducing agent to obtain the flexible negative electrode paper for solid-state batteries.

[0011] The preparation method disclosed in this invention first uses nitrogen-containing molecules as raw materials to prepare wide-diameter carbon nanotubes (average diameter of 100-800 nm) through catalytic pyrolysis. This diameter is much larger than that of carbon nanotubes prepared by conventional methods (average diameter is mostly below 50 nm). Then, using the activated porous carbon nanotubes as a substrate, silicon and carbon are deposited to prepare a flexible silicon-carbon anode with low expansion rate. Furthermore, a complete electronic / ionic conductive network is constructed using conductive carbon materials and solid electrolytes, allowing lithium ions and electrons to fully interact with the silicon-carbon anode through electrical contact. This solves the problem of uneven lithium ion deposition, reduces the formation of lithium dendrites, significantly improves the overall rate performance of the anode, and eliminates the need for copper foil current collectors, reducing the total battery mass and increasing energy density. At the same time, the flexible conductive carbon materials and rigid solid electrolytes together form a "soft-hard" framework, further reducing the volume expansion of the silicon-carbon anode while ensuring the flexibility of the anode sheet. In addition, the prepared material is a flexible paper that can be quickly cut into any shape and does not expand significantly during battery cycling.

[0012] In step (S1):

[0013] In an optional embodiment, the nitrogen-containing molecule is selected from one or more of urea, dicyandiamide, molecules having a triazine structure and their hybrid derivatives, amino acids and their derived polypeptides;

[0014] Optionally, the molecule having a triazine structure and its hybrid derivatives are selected from 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1H-1,2,4-triazole, 4H-1,2,3-triazole, and 4H-1,2,4-triazole.

[0015] Optionally, the amino acids and their derived polypeptides are selected from guanine, leucine, and other small molecule peptide chains formed therefrom.

[0016] Optionally, the molar mass of the nitrogen-containing molecule is 10–1500 g / mol;

[0017] Further optionally, the molar mass of the nitrogen-containing molecule is 10 to 500 g / mol.

[0018] In an optional embodiment, the transition metal salt includes, but is not limited to, one or more of Fe(Ⅲ / Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), and Mn(Ⅱ) as cations, and one or more of nitrate ions, chloride ions, and sulfate ions as anions;

[0019] Optionally, the cation is selected from Fe(III) and / or Co(II);

[0020] Optionally, the anion is selected from nitrate ions.

[0021] In an alternative implementation:

[0022] The mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.1–1.5);

[0023] The catalytic pyrolysis is performed at a temperature of 600–1000℃.

[0024] The carbon nanotubes prepared by the catalytic pyrolysis have an average diameter of 100–800 nm.

[0025] Experiments have shown that the average diameter of the prepared carbon nanotubes can be controlled by adjusting the mass ratio of nitrogen-containing molecules to transition metal salts, thereby regulating the electrochemical performance of the final negative electrode paper and the solid-state battery assembled from it.

[0026] Optionally, the mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.25–0.75);

[0027] Further optionally, the mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.25 to 0.5).

[0028] Optionally, the heating rate of catalytic pyrolysis is 2–20 °C / min, and the holding time is 1–6 h.

[0029] Optionally, the crude product obtained after the catalytic pyrolysis reaction needs to undergo acid washing and drying steps;

[0030] Optionally, the acid concentration in the pickling step is 0.1–2 mol / L;

[0031] Optionally, the pickling time is 2 to 20 hours;

[0032] Optionally, the drying temperature is 50–80℃ and the drying time is 1–10 hours.

[0033] In step (S1):

[0034] In an optional implementation, the physical activation pore formation satisfies at least one of the following A to D:

[0035] A. The physical activation pore-forming agent is selected from one or more of CO, CO2, water vapor, and oxygen;

[0036] Optionally, the activator is selected from one or more of CO, CO2, and water vapor;

[0037] B. The physical activation pore-forming method uses an activator flow rate of 0.1–20 L / min;

[0038] Optionally, the activator flow rate is 5–10 L / min;

[0039] C. The physical activation pore-forming process is carried out at a temperature of 600–1200℃;

[0040] Optionally, the heating rate is 0.1–10 °C / min;

[0041] Further optionally, the heating rate is 1–10 °C / min;

[0042] D. The physical activation pore-forming process takes 1–15 hours.

[0043] Optionally, the physical activation pore formation is carried out in a rotary kiln, and the rotation speed of the rotary kiln is controlled to be 1 to 20 rpm.

[0044] In an optional implementation, the silicon deposition satisfies at least one of the following a to f:

[0045] a. The silicon deposition process uses a silicon source gas as the raw material gas;

[0046] Optionally, the silicon source gas includes, but is not limited to, common types such as silane, ethylsilane, monochlorosilane, and trichlorosilane;

[0047] b. For the silicon deposition, the flow rate of the raw material gas is 1-200 L / h;

[0048] Optionally, the flow rate of the feed gas is 50–150 L / h;

[0049] c. The silicon deposition temperature is 300–600°C;

[0050] Optionally, the heating rate is 1–10 °C / min;

[0051] d. The silicon deposition time is 1–50 h;

[0052] e. The raw material gas also includes a carrier gas;

[0053] Optionally, the carrier gas is nitrogen and / or argon;

[0054] f. Taking the total volume of the raw gas as 100%, the volume ratio of the carrier gas is 1-30%.

[0055] In an optional embodiment, the carbon coating satisfies at least one of the following 1) to 6):

[0056] 1) The carbon coating uses carbon-containing gases as raw materials;

[0057] 2) The carbon coating refers to one or more of the following carbon-containing gases: C1-C4 alkanes (methane, ethane, propane, butane), C2-C4 olefins (ethylene, propylene, butene, 1,3-butadiene), and C2-C4 alkynes (acetylene, propyne, butyne).

[0058] 3) The carbon coating is performed with a feed gas flow rate of 1–100 L / h;

[0059] 4) The carbon coating is performed at a temperature of (400~1200)℃;

[0060] 5) The carbon coating time is 1–20 hours;

[0061] 6) The carbon coating also includes inert gas in the raw material gas. The volume ratio of inert gas is 1-30% based on the total volume of the raw material gas as 100%.

[0062] In step (S2):

[0063] In an optional embodiment, the dispersant is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives.

[0064] In an optional embodiment, solvent I is selected from deionized water and / or N-methylpyrrolidone;

[0065] In an optional embodiment, the mass ratio of silicon carbon negative electrode, dispersant and solvent I in silicon carbon dispersion A is 10:(0.01-5):(10-300);

[0066] Optionally, in the silicon-carbon dispersion A, the mass ratio of silicon-carbon negative electrode, dispersant, and solvent I is 10:(0.15-0.5):(10-300);

[0067] Further optionally, in the silicon-carbon dispersion A, the mass ratio of silicon-carbon negative electrode, dispersant and solvent I is 10:(0.25-0.5):(10-300).

[0068] In an optional embodiment, the one-dimensional carbon material is selected from one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, oligo-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon fibers.

[0069] Optionally, when single-walled carbon nanotubes are selected, the intensity of the G band / D band in their Raman spectrum is not less than 5, the average length is not less than 100 μm, and the diameter is 2 to 15 nm.

[0070] Optionally, when other one-dimensional carbon materials are selected, the G-band / D-band strength is not less than 1, the length is not less than 5 μm, and the diameter is not more than 50 nm.

[0071] In an optional embodiment, the two-dimensional carbon material is selected from graphene oxide;

[0072] Optionally, the two-dimensional graphene oxide is prepared by the Hammer process and has an oxygen content of not less than 20%.

[0073] In an optional embodiment, the solid electrolyte is selected from one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium silicon oxide, and lithium lanthanum titanium oxide;

[0074] In an optional embodiment, the polymer is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives.

[0075] In an optional embodiment, solvent II is selected from deionized water and / or N-methylpyrrolidone;

[0076] In an optional embodiment, the mass ratio of conductive carbon material, solid electrolyte, polymer and solvent II in the electronic / ionic conductive paste B is 1:(0.1-10):(0.1-10):(10-300);

[0077] Optionally, the mass ratio of conductive carbon material, solid electrolyte, polymer and solvent II is 1:(0.5-5):(0.5-5):(10-100);

[0078] In an optional embodiment, the mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0-1);

[0079] Optionally, the mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0.01 to 0.5).

[0080] Experiments have shown that introducing additional two-dimensional carbon materials can further improve the conductivity of the system, resulting in improved initial coulombic efficiency, cycle retention, and rate performance of the final assembled solid-state battery.

[0081] Comparative experiments revealed that replacing one-dimensional carbon materials with two-dimensional or three-dimensional carbon materials (such as acetylene black) would lead to a deterioration in the cycle retention rate and rate performance of the final assembled solid-state battery.

[0082] In an optional embodiment, the nanocellulose has a diameter of 1–50 nm and a length of 30–100 μm;

[0083] In an optional embodiment, solvent III is selected from deionized water and / or N-methylpyrrolidone;

[0084] In an optional embodiment, the solid content of the fiber dispersion emulsion C is 1 to 50 wt%.

[0085] In an optional embodiment, the mass ratio of silicon carbon dispersion A, electronic / ionic conductive paste B, and fiber dispersion emulsion C is 10:(1-10):(1-10).

[0086] Optionally, the mass ratio of silicon carbon dispersion A, electronic / ionic conductive slurry B, and fiber dispersion emulsion C is 10:(2.5-5):(2.5-5);

[0087] Experiments have shown that by optimizing the proportions of the above-mentioned raw materials in the papermaking pulp, the electrochemical performance of the final negative electrode paper and its assembled solid-state battery can be controlled.

[0088] Alternatively, the mass ratio of silicon carbon dispersion A, electronic / ionic conductive slurry B, and fiber dispersion emulsion C is 10:5:5.

[0089] Optionally, the mixing and dispersion is carried out at a dispersion rate of 500 to 3000 rpm and a dispersion time of 0.5 to 10 h.

[0090] In step (S2):

[0091] In an optional embodiment, the fiber dispersion emulsion C satisfies at least one of the following (1) to (2):

[0092] (1) The fiber dispersion emulsion C also includes elastic fibers;

[0093] Optionally, the elastic fiber is selected from one or more of polytetrafluoroethylene fiber, polyvinylidene fluoride fiber, and polysiloxane fiber;

[0094] Optionally, the mass ratio of nanocellulose to elastic fiber is (0.2–5):1;

[0095] Optionally, nanocellulose is first dispersed in solvent III to obtain a nanocellulose dispersion, then elastic fibers are dispersed in solvent III to obtain an elastic fiber dispersion, and finally the two are mixed evenly to obtain a fiber dispersion emulsion C.

[0096] Optionally, the concentration of the nanocellulose dispersion is 0.1–10 wt%.

[0097] Optionally, the concentration of the elastic fiber dispersion is 0.1–10 wt%.

[0098] Optionally, the volume ratio of the nanocellulose dispersion to the elastic fiber dispersion is (0.2–5):1.

[0099] Experiments have shown that the introduction of elastic fibers further improves the stability of the negative electrode, giving it certain mechanical properties while also providing flexibility. This allows the negative electrode to be cut arbitrarily without causing structural defects, and the elastic fibers can also further overcome the volume expansion of silicon-carbon.

[0100] (2) The nanocellulose undergoes copper modification treatment, specifically including:

[0101] Copper-modified nanocellulose was obtained by immersing nanocellulose in an aqueous solution of copper salt and washing it.

[0102] Optionally, the concentration of the copper salt aqueous solution is 1–20 wt%.

[0103] Optionally, the selected copper salt may contain one or more of the following anions: nitrate, chloride, and sulfate.

[0104] In step (S3):

[0105] In an optional embodiment, the amine-based small molecule reducing agent is selected from hydrazine hydrate and / or ethylenediamine;

[0106] Optionally, the amine-based small molecule reducing agent is selected from hydrazine hydrate, which has stronger reducing properties.

[0107] In an optional embodiment, the amine-based small molecule reducing agent is reduced in a vapor state;

[0108] In an optional embodiment, the vapor containing the amine-containing small molecule reducing agent also includes water vapor;

[0109] In an optional embodiment, the mass fraction of the amine-based small molecule reducing agent is 0.1% to 3% based on the total mass of steam (100%).

[0110] Optionally, the mass fraction of the amine-based small molecule reducing agent is 1–2%.

[0111] In an optional embodiment, the temperature of the reduction treatment is 80–120°C;

[0112] Optionally, the reduction process can be performed over a period of 5 to 12 hours.

[0113] Secondly, the present invention also provides a flexible negative electrode paper for solid-state batteries prepared according to the method.

[0114] Thirdly, the present invention also provides a negative electrode sheet, which is prepared by impregnating the flexible negative electrode paper for solid-state batteries with electrolyte.

[0115] Fourthly, the present invention also provides a solid-state battery, including the aforementioned negative electrode sheet.

[0116] Compared with the prior art, the present invention has the following advantages:

[0117] This invention discloses a method for preparing flexible negative electrode paper for solid-state batteries. The method uses silicon as the core active material and wide-diameter porous carbon nanotubes (average diameter of 100-800 nm) prepared by catalytic pyrolysis of nitrogen-containing molecules as raw materials as the substrate. Then, it combines an electronic / ionic conductive network constructed with conductive carbon materials and solid electrolyte to prepare a soft and elastic negative electrode sheet, which solves the current problem of silicon-carbon negative electrodes having significant expansion and low conductivity.

[0118] Solid-state batteries assembled using the flexible negative electrode paper prepared in this invention as the negative electrode exhibit excellent cycle stability, rate performance, and low expansion rate, while also possessing high initial efficiency and high capacity. Attached Figure Description

[0119] Figure 1 This is a schematic diagram of the preparation process of a flexible negative electrode paper for solid-state batteries disclosed in this invention. Detailed Implementation

[0120] 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.

[0121] In the description of this invention, it should be noted that those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. The embodiments of this invention are described below based on its overall structure. Unless otherwise specified, the raw materials used in the embodiments of this invention were all purchased commercially.

[0122] In a first aspect, the present invention provides a method for preparing flexible negative electrode paper for solid-state batteries, comprising:

[0123] (S1) Nitrogen-containing molecules are mixed evenly with transition metal salts and carbon nanotubes are obtained by catalytic pyrolysis reaction. Then, porous carbon nanotubes are obtained by physical activation to create pores. Using the porous carbon nanotubes as a substrate, silicon carbon anodes are obtained by silicon deposition and carbon coating in sequence.

[0124] (S2) A silicon-carbon dispersion A is obtained by mixing silicon-carbon anode, dispersant and solvent I; an electronic / ionic conductive slurry B is obtained by mixing conductive carbon material, solid electrolyte, polymer and solvent II; a fiber dispersion emulsion C is obtained by mixing nanocellulose and solvent III; and a papermaking pulp is obtained by mixing and dispersing silicon-carbon dispersion A, electronic / ionic conductive slurry B and fiber dispersion emulsion C.

[0125] The conductive carbon material includes one-dimensional carbon material and optional two-dimensional carbon material.

[0126] (S3) The paper pulp is coated onto a substrate and then reduced by an amine-containing small molecule reducing agent to obtain the flexible negative electrode paper for solid-state batteries.

[0127] The preparation method disclosed in this invention first uses nitrogen-containing molecules as raw materials to prepare wide-diameter carbon nanotubes (average diameter of 100-800 nm) through catalytic pyrolysis. This diameter is much larger than that of carbon nanotubes prepared by conventional methods (average diameter is mostly below 50 nm). Then, using the activated porous carbon nanotubes as a substrate, silicon and carbon are deposited to prepare a flexible silicon-carbon anode with low expansion rate. Furthermore, a complete electronic / ionic conductive network is constructed using conductive carbon materials and solid electrolytes, allowing lithium ions and electrons to fully interact with the silicon-carbon anode through electrical contact. This solves the problem of uneven lithium ion deposition, reduces the formation of lithium dendrites, significantly improves the overall rate performance of the anode, and eliminates the need for copper foil current collectors, reducing the total battery mass and increasing energy density. At the same time, the flexible conductive carbon materials and rigid solid electrolytes together form a "soft-hard" framework, further reducing the volume expansion of the silicon-carbon anode while ensuring the flexibility of the anode sheet. In addition, the prepared material is a flexible paper that can be quickly cut into any shape and does not expand significantly during battery cycling.

[0128] In step (S1):

[0129] In an optional embodiment, the nitrogen-containing molecule is selected from one or more of urea, dicyandiamide, molecules having a triazine structure and their hybrid derivatives, amino acids and their derived polypeptides;

[0130] Optionally, the molecule having a triazine structure and its hybrid derivatives are selected from 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1H-1,2,4-triazole, 4H-1,2,3-triazole, and 4H-1,2,4-triazole.

[0131] Optionally, the amino acids and their derived polypeptides are selected from guanine, leucine, and other small molecule peptide chains formed therefrom.

[0132] Optionally, the molar mass of the nitrogen-containing molecule is 10–1500 g / mol; specifically, it can be 10 g / mol, 50 g / mol, 100 g / mol, 200 g / mol, 300 g / mol, 400 g / mol, 500 g / mol, 600 g / mol, 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1100 g / mol, 1200 g / mol, 1300 g / mol, 1400 g / mol, 1500 g / mol, or any value within the above range.

[0133] Further optionally, the molar mass of the nitrogen-containing molecule is 10 to 500 g / mol.

[0134] In an optional embodiment, the transition metal salt includes, but is not limited to, one or more of Fe(Ⅲ / Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), and Mn(Ⅱ) as cations, and one or more of nitrate ions, chloride ions, and sulfate ions as anions;

[0135] Optionally, the cation is selected from Fe(III) and / or Co(II);

[0136] Optionally, the anion is selected from nitrate ions.

[0137] In an alternative implementation:

[0138] The mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.1 to 1.5); specifically, it can be 10:0.1, 10:0.3, 10:0.5, 10:0.8, 10:1.0, 10:1.2, 10:1.5 or any ratio within the above range;

[0139] The carbon nanotubes prepared by the catalytic pyrolysis have an average diameter of 100–800 nm.

[0140] Optionally, the mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.25–0.75);

[0141] Further optionally, the mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.25 to 0.5).

[0142] Experiments have shown that the average diameter of the prepared carbon nanotubes can be controlled by adjusting the mass ratio of nitrogen-containing molecules to transition metal salts, thereby regulating the electrochemical performance of the final negative electrode paper and the solid-state battery assembled from it.

[0143] In an alternative implementation:

[0144] The catalytic pyrolysis is performed at a temperature of 600–1000°C; specifically, it can be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, or any value within the above range.

[0145] Optionally, the heating rate of catalytic pyrolysis is 2 to 20 °C / min; specifically, it can be 2 °C / min, 5 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 15 °C / min, 18 °C / min, 20 °C / min or any value within the above range.

[0146] Optionally, the holding time for catalytic pyrolysis is 1 to 6 hours; specifically, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or any value within the above range.

[0147] Optionally, the crude product obtained after the catalytic pyrolysis reaction needs to undergo acid washing and drying steps;

[0148] Optionally, the acid concentration in the pickling step is 0.1–2 mol / L; specifically, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, or any value within the above range.

[0149] Optionally, the pickling time is 2 to 20 hours; specifically, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours or any value within the above range.

[0150] Optionally, the drying temperature is 50 to 80°C; specifically, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value within the above range.

[0151] Optionally, the drying time is 1 to 10 hours; specifically, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any value within the above range.

[0152] In step (S1):

[0153] In an optional implementation, the physical activation pore formation satisfies at least one of the following A to D:

[0154] A. The physical activation pore-forming agent is selected from one or more of CO, CO2, water vapor, and oxygen;

[0155] Optionally, the activator is selected from one or more of CO, CO2, and water vapor;

[0156] B. The physical activation pore-forming process uses an activator flow rate of 0.1–20 L / min; specifically, it can be 0.1 L / min, 0.5 L / min, 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 12 L / min, 14 L / min, 16 L / min, 18 L / min, 20 L / min, or any value within the above range.

[0157] Optionally, the activator flow rate is 5–10 L / min.

[0158] C. The physical activation pore-forming temperature is 600-1200℃; specifically, it can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ or any value within the above range.

[0159] Optionally, the heating rate is 0.1 to 10 °C / min; specifically, it can be 0.1 °C / min, 0.5 °C / min, 1 °C / min, 2 °C / min, 5 °C / min, 8 °C / min, 10 °C / min or any value within the above range.

[0160] Alternatively, the heating rate is 1–10 °C / min.

[0161] D. The physical activation pore-forming time is 1 to 15 hours; specifically, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or any value within the above range.

[0162] Optionally, the physical activation pore formation is carried out in a rotary kiln, and the rotation speed of the rotary kiln is controlled to be 1 to 20 rpm; specifically, it can be 1 rpm, 2 rpm, 5 rpm, 8 rpm, 10 rpm, 12 rpm, 15 rpm, 18 rpm, 20 rpm or any value within the above range.

[0163] In an optional implementation, the silicon deposition satisfies at least one of the following a to f:

[0164] a. The silicon deposition process uses a silicon source gas as the raw material gas;

[0165] Optionally, the silicon source gas includes, but is not limited to, common types such as silane, ethylsilane, monochlorosilane, and trichlorosilane;

[0166] b. For the silicon deposition, the flow rate of the raw material gas is 1 to 200 L / h; specifically, it can be 1 L / h, 5 L / h, 10 L / h, 20 L / h, 30 L / h, 50 L / h, 80 L / h, 100 L / h, 150 L / h, 200 L / h or any value within the above range.

[0167] Optionally, the flow rate of the feed gas is 50–150 L / h.

[0168] c. The silicon deposition temperature is 300–600°C; specifically, it can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, or any value within the above range.

[0169] Optionally, the heating rate is 1 to 10 °C / min; specifically, it can be 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min or any value within the above range.

[0170] d. The silicon deposition time is 1 to 50 hours; specifically, it can be 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours or any value within the above range.

[0171] e. The raw material gas also includes a carrier gas;

[0172] Optionally, the carrier gas is nitrogen and / or argon;

[0173] f. Taking the total volume of the raw material gas as 100%, the volume ratio of the carrier gas is 1% to 30%; specifically, it can be 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any value within the above range.

[0174] In an optional embodiment, the carbon coating satisfies at least one of the following 1) to 6):

[0175] 1) The carbon coating uses carbon-containing gases as raw materials;

[0176] 2) The carbon coating refers to one or more of the following carbon-containing gases: C1-C4 alkanes (methane, ethane, propane, butane), C2-C4 olefins (ethylene, propylene, butene, 1,3-butadiene), and C2-C4 alkynes (acetylene, propyne, butyne).

[0177] 3) The carbon coating process involves a raw gas flow rate of 1 to 100 L / h; specifically, it can be 1 L / h, 5 L / h, 10 L / h, 20 L / h, 30 L / h, 50 L / h, 80 L / h, 100 L / h, or any value within the above range.

[0178] 4) The carbon coating temperature is 400-1200℃; specifically, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ or any value within the above range.

[0179] 5) The carbon coating time is 1 to 20 hours; specifically, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 20 hours or any value within the above range.

[0180] 6) The carbon coating also includes an inert gas in the raw material gas. The volume percentage of the inert gas is 1% to 30% based on the total volume of the raw material gas as 100%. Specifically, it can be 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any value within the above range.

[0181] In step (S2):

[0182] In an optional embodiment, the dispersant is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives.

[0183] In an optional embodiment, solvent I is selected from deionized water and / or N-methylpyrrolidone;

[0184] In an optional embodiment, the mass ratio of silicon-carbon negative electrode to dispersant in silicon-carbon dispersion A is 10:(0.01~5); specifically, it can be 10:0.01, 10:0.05, 10:0.1, 10:0.5, 10:1.0, 10:1.5, 10:2.0, 10:2.5, 10:3.0, 10:3.5, 10:4.0, 10:4.5, 10:5.0 or any ratio within the above range;

[0185] Optionally, the mass ratio of silicon-carbon anode to dispersant is 10:(0.15~0.5);

[0186] Further optionally, the mass ratio of silicon-carbon anode to dispersant is 10:(0.25-0.5).

[0187] In an optional embodiment, the mass ratio of silicon-carbon negative electrode to solvent I in silicon-carbon dispersion A is 10:(10-300); specifically, it can be 10:10, 10:20, 10:50, 10:80, 10:100, 10:150, 10:200, 10:250, 10:300 or any ratio within the above range.

[0188] In an optional embodiment, the one-dimensional carbon material is selected from one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, oligo-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon fibers.

[0189] Optionally, when single-walled carbon nanotubes are selected, the intensity of the G band / D band in their Raman spectrum is not less than 5, the average length is not less than 100 μm, and the diameter is 2 to 15 nm.

[0190] Optionally, when other one-dimensional carbon materials are selected, the G-band / D-band strength is not less than 1, the length is not less than 5 μm, and the diameter is not more than 50 nm.

[0191] In an optional embodiment, the two-dimensional carbon material is selected from graphene oxide;

[0192] Optionally, the two-dimensional graphene oxide is prepared by the Hammer process and has an oxygen content of not less than 20%.

[0193] In an optional embodiment, the solid electrolyte is selected from one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium silicon oxide, and lithium lanthanum titanium oxide;

[0194] In an optional embodiment, the polymer is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives.

[0195] In an optional embodiment, solvent II is selected from deionized water and / or N-methylpyrrolidone;

[0196] In an optional embodiment, the mass ratio of conductive carbon material to solid electrolyte in the electronic / ionic conductive paste B is 1:(0.1 to 10); specifically, it can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any ratio within the above range;

[0197] In the electronic / ionic conductive paste B, the mass ratio of conductive carbon material to polymer is 1:(0.1~10); specifically, it can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any ratio within the above range;

[0198] In the electronic / ionic conductive paste B, the mass ratio of conductive carbon material to solvent II is 1:(10-300); specifically, it can be 1:10, 1:20, 1:50, 1:80, 1:100, 1:150, 1:200, 1:250, 1:300 or any ratio within the above range.

[0199] Optionally, the mass ratio of conductive carbon material, solid electrolyte, polymer and solvent II is 1:(0.5-5):(0.5-5):(10-100);

[0200] In an optional embodiment, the mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0-1);

[0201] Optionally, the mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0.01 to 0.5); specifically, it can be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5 or any ratio within the above range; further optionally, the mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0.01 to 0.1).

[0202] Experiments have shown that introducing additional two-dimensional carbon materials can further improve the conductivity of the system, resulting in improved initial coulombic efficiency, cycle retention, and rate performance of the final assembled solid-state battery.

[0203] Comparative experiments revealed that replacing one-dimensional carbon materials with two-dimensional or three-dimensional carbon materials (such as acetylene black) would lead to a deterioration in the cycle retention rate and rate performance of the final assembled solid-state battery.

[0204] In an optional embodiment, the nanocellulose has a diameter of 1–50 nm and a length of 30–100 μm;

[0205] In an optional embodiment, solvent III is selected from deionized water and / or N-methylpyrrolidone;

[0206] In an optional embodiment, the solid content of the fiber dispersion emulsion C is 1 to 50 wt%; specifically, it can be 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, or any value within the above range.

[0207] In an optional embodiment, the mass ratio of silicon carbon dispersion A to electronic / ionic conductive paste B is 10:(1 to 10); specifically, it can be 10:1, 10:1.5, 10:2, 10:2.5, 10:3, 10:3.5, 10:5, 10:5.5, 10:8, 10:8.5, 10:10 or any ratio within the above range;

[0208] In an optional embodiment, the mass ratio of silicon carbon dispersion A to fiber dispersion emulsion C is 10:(1 to 10); specifically, it can be 10:1, 10:1.5, 10:2, 10:2.5, 10:3, 10:3.5, 10:5, 10:5.5, 10:8, 10:8.5, 10:10 or any ratio within the above range;

[0209] Optionally, the mass ratio of silicon carbon dispersion A, electronic / ionic conductive slurry B, and fiber dispersion emulsion C is 10:(2.5-5):(2.5-5);

[0210] Experiments have shown that by optimizing the proportions of the above-mentioned raw materials in the papermaking pulp, the electrochemical performance of the final negative electrode paper and its assembled solid-state battery can be controlled.

[0211] Alternatively, the mass ratio of silicon carbon dispersion A, electronic / ionic conductive slurry B, and fiber dispersion emulsion C is 10:5:5.

[0212] Optionally, the mixing and dispersion rate is 500 to 3000 rpm; specifically, it can be 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, 1800 rpm, 2000 rpm, 2500 rpm, 3000 rpm or any value within the above range.

[0213] Optionally, the mixing and dispersion time is controlled within 0.5 to 10 hours; specifically, it can be 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any value within the above range.

[0214] In step (S2):

[0215] In an optional embodiment, the fiber dispersion emulsion C satisfies at least one of the following (1) to (2):

[0216] (1) The fiber dispersion emulsion C also includes elastic fibers;

[0217] Optionally, the elastic fiber is selected from one or more of polytetrafluoroethylene fiber, polyvinylidene fluoride fiber, and polysiloxane fiber;

[0218] Optionally, the mass ratio of nanocellulose to elastic fiber is (0.2-5):1; specifically, it can be 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 or any ratio within the above range.

[0219] Optionally, nanocellulose is first dispersed in solvent III to obtain a nanocellulose dispersion, then elastic fibers are dispersed in solvent III to obtain an elastic fiber dispersion, and finally the two are mixed evenly to obtain a fiber dispersion emulsion C.

[0220] Optionally, the concentration of the nanocellulose dispersion is 0.1 to 10 wt%; specifically, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 8 wt%, 10 wt%, or any value within the above range.

[0221] Optionally, the concentration of the elastic fiber dispersion is 0.1 to 10 wt%; specifically, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 8 wt%, 10 wt%, or any value within the above range.

[0222] Optionally, the volume ratio of the nanocellulose dispersion to the elastic fiber dispersion is (0.2-5):1; specifically, it can be 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 or any ratio within the above range.

[0223] Experiments have shown that the introduction of elastic fibers further improves the stability of the negative electrode, giving it certain mechanical properties while also providing flexibility. This allows the negative electrode to be cut arbitrarily without causing structural defects, and the elastic fibers can also further overcome the volume expansion of silicon-carbon.

[0224] (2) The nanocellulose undergoes copper modification treatment, specifically including:

[0225] Copper-modified nanocellulose was obtained by immersing nanocellulose in an aqueous solution of copper salt and washing it.

[0226] Optionally, the concentration of the copper salt aqueous solution is 1 to 20 wt%; specifically, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, or any value within the above range.

[0227] Optionally, the selected copper salt may contain one or more of the following anions: nitrate, chloride, and sulfate.

[0228] In step (S3):

[0229] In an optional embodiment, the amine-based small molecule reducing agent is selected from hydrazine hydrate and / or ethylenediamine;

[0230] Optionally, the amine-based small molecule reducing agent is selected from hydrazine hydrate, which has stronger reducing properties.

[0231] In an optional embodiment, the amine-based small molecule reducing agent is reduced in a vapor state;

[0232] In an optional embodiment, the vapor containing the amine-containing small molecule reducing agent also includes water vapor;

[0233] In an optional embodiment, the mass fraction of the amine-based small molecule reducing agent is 0.1% to 3% based on the total mass of steam (100%); specifically, it can be 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, or any value within the above range.

[0234] Optionally, the mass fraction of the amine-based small molecule reducing agent is 1–2%.

[0235] In an optional embodiment, the temperature of the reduction treatment is 80 to 120°C; specifically, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or any value within the above range.

[0236] Optionally, the restoration process can be performed for 5 to 12 hours; specifically, it can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours or any value within the above range.

[0237] Secondly, the present invention also provides a flexible negative electrode paper for solid-state batteries prepared according to the method.

[0238] Thirdly, the present invention also provides a negative electrode sheet, which is prepared by impregnating the flexible negative electrode paper for solid-state batteries with electrolyte.

[0239] Fourthly, the present invention also provides a solid-state battery, including the aforementioned negative electrode sheet.

[0240] Example 1

[0241] (S1) Preparation of silicon-carbon anode:

[0242] 20 kg of melamine and 1 kg of cobalt nitrate powder were mixed in a mixer for 2 hours and then fed into a tube furnace. The oxygen content was controlled to be below 50 ppm. The temperature was then increased to 800 ℃ at a rate of 10 ℃ / min and held for 2 hours. After the material cooled, it was taken out and immersed in a 1 mol / L hydrochloric acid solution for 5 hours. After the material was washed with water until neutral, excess water was filtered out. The filter cake was dried at 60 ℃ for 5 hours to obtain a dry product. The dry product was then broken up using a dispersant to obtain carbon nanotubes.

[0243] 10 kg of carbon nanotubes were placed in a rotary kiln, the kiln speed was controlled at 5 rpm, the oxygen content was below 50 ppm, and the temperature was raised to 700 ℃ at 5 ℃ / min. Then, water vapor with a flow rate of 10 L / min was introduced and the temperature was maintained for 4 h. After the reaction was completed, the water vapor supply was cut off, and the activated carbon nanotubes were obtained after cooling.

[0244] Transmission electron microscopy (TEM) revealed that the average diameter of the activated carbon nanotubes prepared in this embodiment ranged from 200 to 400 nm.

[0245] 5 kg of activated carbon nanotubes were placed in a rotary kiln, with the kiln speed controlled at 5 rpm and the oxygen content below 30 ppm. The temperature was raised to 500°C at a rate of 5°C / min, followed by the introduction of silane gas at a flow rate of 100 L / h and holding for 20 h, with nitrogen accounting for 2%. The temperature was then raised to 650°C at a rate of 5°C / min, followed by the introduction of acetylene gas at a flow rate of 50 L / h and holding for 5 h, with nitrogen accounting for 20%. After the material cooled, it was removed to obtain the silicon-carbon anode.

[0246] (S2) Papermaking pulp preparation

[0247] Preparation of silicon-carbon dispersion A: 100g of silicon-carbon anode prepared in step (S1), 2.5g of carboxymethyl cellulose and 500g of water are mixed and dispersed (wherein, the total solid content is 17% and the silicon-carbon anode content is 16.6%).

[0248] Preparation of electronic / ionic conductive paste B: 5g single-walled carbon nanotubes, 2g multi-walled carbon nanotubes, 4g lithium lanthanum zirconium oxide, 4g polyoxyethylene, and 400g water were mixed and dispersed (total solid content approximately 3.6%).

[0249] Preparation of fiber dispersion emulsion C: 10g of nanocellulose (CNF-C) was dispersed in 190g of water;

[0250] Paper pulp preparation: 100g silicon carbide dispersion A, 50g electronic / ionic conductive pulp B, and 50g fiber dispersion emulsion C were mixed and dispersed at a dispersion rate of 1000rpm for 5h.

[0251] (S3) Negative electrode paper preparation

[0252] The paper pulp obtained in step (S2) was coated onto a PTFE plate and dried at 70°C for 5 hours to obtain preliminary negative electrode paper. The negative electrode paper was then reduced in hydrazine hydrate vapor (hydrazine hydrate mass fraction 1.5%) at 80°C for 8 hours, followed by roll pressing to obtain the final negative electrode paper. The thickness of the negative electrode paper was measured to be 96.3 μm.

[0253] Example 2

[0254] The preparation process is basically the same as in Example 1, except that in step (S1), the mass of cobalt nitrate powder is replaced with 0.5 kg.

[0255] TEM analysis showed that the average diameter of the activated carbon nanotubes prepared in this embodiment ranged from 400 to 600 nm. The thickness of the prepared negative electrode paper was 97.1 μm.

[0256] Example 3

[0257] The preparation process is basically the same as in Example 1, except that in step (S1), the mass of cobalt nitrate powder is replaced with 1.5 kg.

[0258] TEM analysis showed that the average diameter of the activated carbon nanotubes prepared in this embodiment ranged from 100 to 200 nm. The thickness of the prepared negative electrode paper was 96.5 μm.

[0259] Example 4

[0260] The preparation process is basically the same as in Example 1, except that in step (S1), cobalt nitrate powder is replaced with an equal mass of nickel nitrate powder.

[0261] TEM analysis showed that the average diameter of the activated carbon nanotubes prepared in this embodiment ranged from 200 to 400 nm. The thickness of the prepared negative electrode paper was 96.8 μm.

[0262] Example 5

[0263] The preparation process is basically the same as in Example 1, except that in step (S1), the flow rate of silane gas is replaced with 50 L / h.

[0264] The thickness of the prepared negative electrode paper was tested to be 96.7 μm.

[0265] Example 6

[0266] The preparation process is basically the same as in Example 1, except that in step (S1), the flow rate of silane gas is replaced with 150 L / h.

[0267] The thickness of the prepared negative electrode paper was tested to be 96.2 μm.

[0268] Example 7

[0269] The preparation process is basically the same as in Example 1, except for the preparation of the electronic / ionic conductive paste B in step (S2):

[0270] Mix and disperse 5g of single-walled carbon nanotubes, 2g of multi-walled carbon nanotubes, 0.1g of graphene oxide, 4g of lithium lanthanum zirconium oxide, 4g of polyoxyethylene, and 400g of water.

[0271] The thickness of the prepared negative electrode paper was tested to be 95.3 μm.

[0272] Example 8

[0273] The preparation process is basically the same as in Example 7, except for the preparation of the fiber dispersion emulsion C in step (S2):

[0274] 10g of nanocellulose was dispersed in 190g of water to obtain a nanocellulose dispersion.

[0275] 10g of polytetrafluoroethylene fiber was dispersed in 190g of water to obtain a polytetrafluoroethylene fiber dispersion.

[0276] Equal masses of nanocellulose dispersion and polytetrafluoroethylene fiber dispersion were thoroughly mixed and dispersed. The thickness of the prepared negative electrode paper was measured to be 95.8 μm.

[0277] Example 9

[0278] The preparation process is basically the same as in Example 7, except for the preparation of the fiber dispersion emulsion C in step (S2):

[0279] 10g of nanocellulose was soaked in 110g of copper nitrate aqueous solution (concentration of 9wt%). After 24h, the nanocellulose was taken out and rinsed three times with deionized water to ensure the removal of copper salts, thus obtaining copper-modified nanocellulose.

[0280] 10g of copper-modified nanocellulose was dispersed in 190g of water to obtain a copper-modified nanocellulose dispersion.

[0281] 10g of polytetrafluoroethylene fiber was dispersed in 190g of water to obtain a polytetrafluoroethylene fiber dispersion.

[0282] Equal masses of copper-modified nanocellulose dispersion and polytetrafluoroethylene fiber dispersion were thoroughly mixed and dispersed.

[0283] The thickness of the prepared negative electrode paper was tested to be 95.8 μm.

[0284] Example 10

[0285] The preparation process is basically the same as in Example 1, except that in step (S2), the preparation of silicon carbon dispersion A is carried out by replacing the mass of carboxymethyl cellulose with 1.5g.

[0286] The thickness of the prepared negative electrode paper was tested to be 95.3 μm.

[0287] Example 11

[0288] The preparation process is basically the same as in Example 1, except that in step (S2), the mass of electronic / ionic conductive pulp B is replaced with 25g when preparing the paper pulp.

[0289] The thickness of the prepared negative electrode paper was tested to be 92.3 μm.

[0290] Example 12

[0291] The preparation process is basically the same as in Example 1, except that in step (S2), when preparing the paper pulp, the mass of the fiber dispersion emulsion C is replaced with 25g.

[0292] The thickness of the prepared negative electrode paper was tested to be 93.4 μm.

[0293] Example 13

[0294] The preparation process is basically the same as in Example 1, except that in step (S3), hydrazine hydrate vapor is replaced with ethylenediamine vapor (mass fraction is still 1.5%, temperature is 100°C).

[0295] The thickness of the prepared negative electrode paper was tested to be 96.3 μm.

[0296] Comparative Example 1

[0297] The preparation process is basically the same as in Example 1, except that in step (S1), the mass of cobalt nitrate powder is replaced with 3 kg.

[0298] TEM analysis showed that the average diameter of the activated carbon nanotubes prepared in this comparative example ranged from 10 to 50 nm.

[0299] The thickness of the prepared negative electrode paper was tested to be 97.1 μm.

[0300] Comparative Example 2

[0301] The preparation process is basically the same as in Example 1, except for the preparation of the electronic / ionic conductive paste B in step (S2):

[0302] Mix and disperse 7g of graphene oxide, 4g of lithium lanthanum zirconium oxide, 4g of polyoxyethylene, and 400g of water.

[0303] The thickness of the prepared negative electrode paper was tested to be 96.7 μm.

[0304] Comparative Example 3

[0305] The preparation process is basically the same as in Example 1, except for the preparation of the electronic / ionic conductive paste B in step (S2):

[0306] Mix and disperse 7g acetylene black, 4g lithium lanthanum zirconium oxide, 4g polyoxyethylene, and 400g water.

[0307] The thickness of the prepared negative electrode paper was tested to be 95.9 μm.

[0308] Comparative Example 4

[0309] The preparation process is basically the same as in Example 1, except that in step (S3), the paper pulp obtained in step (S2) is scraped onto a PTFE plate and dried at 70°C for 5 hours to obtain the negative electrode paper.

[0310] The thickness of the prepared negative electrode paper was tested to be 105.3 μm.

[0311] The specific test data of the silicon-carbon anode materials prepared in step S1 of each embodiment and comparative example of the present invention are shown in Table 1 below. The silicon content was obtained by conversion from the thermogravimetric curve in air (conversion method: Si% = M1 × 100% × 0.467 / M0, where M0 and M1 are the masses of the test sample at room temperature and 1000℃, respectively, and 0.467 is the mass ratio coefficient of silicon in silicon dioxide). The powder resistance was measured by a four-terminal powder resistivity tester (ST2722B), and the specific surface area was obtained by a high-precision nitrogen adsorption-desorption test system (JW-HB100).

[0312] Table 1

[0313]

[0314] In this invention, the dispersion stability of the papermaking pulp affects the electrochemical performance of the final negative electrode paper. Therefore, it is necessary to test the dispersion stability of the papermaking pulp prepared in step S2. The test method is the dilution-precipitation method. The specific steps are as follows: 20g of papermaking pulp is added to a 200mL glass conical flask, and then deionized water is added to dilute it to 5 times the original volume. At this time, the solid content of the dispersion is γ0. The flask is covered with plastic wrap and ultrasonicated in a 10W ultrasonic bath for 10min. Then it is placed in a 25℃ constant temperature oven for 24h. After 24h, the lower precipitate is discarded. At this time, the solid content of the supernatant is γ1. The ratio of the solid content before and after precipitation is calculated to obtain the value Q related to the dispersion stability of the pulp, i.e., Q = γ1 / γ0. The closer the Q value is to 1, the better the dispersion stability.

[0315] The thickness of the negative electrode paper was measured using a micrometer.

[0316] The resistance of the negative electrode paper was tested using a blocking electrode. The test method was as follows: the negative electrode paper was cut and punched into small circular pieces with a diameter of 12mm. The circular pieces were sandwiched between two stainless steel sheets and clamped together with alligator clips. The resistance was then tested using a multimeter. The resistance (Ω / cm) was then normalized according to the thickness reading shown on the micrometer.

[0317] Solid-state full cells were assembled using negative electrode paper prepared in each embodiment and comparative example. The specific test methods are as follows:

[0318] ① Preparation of the positive electrode sheet: A positive electrode slurry (70 wt% solid content) was prepared by mixing lithium nickel cobalt manganese oxide (NCM811), conductive agent SuperP, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 97:1:0.5:1.5 with N-methylpyrrolidone (NMP). This slurry was coated onto both sides of an aluminum foil current collector, dried at 100°C, and then cold-pressed at 4 MPa at room temperature. The edges were then trimmed, cut into strips, and slits were formed. The tabs were then welded to produce the positive electrode sheet. The preparation of the diaphragm electrolyte is as follows. Preparation of the negative electrode sheet: The negative electrode paper was trimmed, cut into sheets, and slit, and electrode tabs were welded to form the negative electrode sheet (the negative electrode paper was soaked in the electrolyte in the dark for 3 hours and then dried at 60°C; the electrolyte consisted of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (EC:EMC:DEC volume ratio = 1:1:1) and LiPF6 (1.0M)). Preparation of the solid electrolyte film: 5g of polyvinylidene fluoride (PVDF), 10g of polyethylene oxide (PEO), 5g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 5g of solid electrolyte lithium lanthanum zirconium tantalum oxide (LLZTO) were added sequentially to 110g of DMF. After stirring for 12 hours, the slurry was uniformly coated onto a PET substrate using a height-adjustable doctor blade. Finally, the film was vacuum dried at 55°C for 24 hours, and the PET template was removed to obtain the LLZTO / PVDF / PEO solid electrolyte film.

[0319] ② Using an LLZTO / PVDF / PEO solid electrolyte membrane as the separator, the prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes, and wound to obtain a bare cell; the bare cell is placed in an aluminum-plastic shell package and heated under a relative vacuum pressure of -0.95×10 5 Under Pa conditions, the battery is dried at 100℃ until the moisture content is below 100ppm. Then, the battery is packaged, left to stand, formed (0.02C constant current charging for 2 hours, 0.1C constant current charging for 2 hours), shaped, and capacity tested (capacity grading) to produce a soft-pack solid-state lithium-ion battery.

[0320] During battery assembly, five batteries were prepared for each test group, and a total of five sets of data were tested. The final performance was taken as the average of the five sets of data.

[0321] ③ Battery cycle performance was tested on Xinwei equipment, specifically as follows: At 25℃, the battery was first discharged at 0.1C to 0.005V, then discharged at 0.08C to 0.001V, then at 0.05C to 0.001V, and finally at 0.02C to 0.001V, and then left to stand for 10 minutes; next, it was charged at 0.1C to 1.5V, left to stand for 10 minutes, and the charge / discharge capacity after the first cycle was recorded, and the initial coulombic efficiency was calculated; the battery was cycled 100 times in the same manner, and the charge / discharge capacity after 100 cycles was recorded, and the capacity retention rate after 100 cycles was calculated. The expansion rate was obtained by comparing the electrode expansion displacement before and after the cycle. The 3C reversible specific capacity was obtained by changing the 0.1C to 3C after 5 cycles of the above rate test. Specific test / calculation results are shown in Table 2 below.

[0322] Table 2

[0323]

[0324]

[0325] Comparing Examples 1 to 13 in Table 2, it can be seen that the solid-state batteries assembled from the negative electrode materials prepared in each example all have excellent cycle stability, rate performance and low expansion rate, among which the product prepared in Example 9 has the best electrochemical performance.

[0326] Comparing Examples 1-3 and Comparative Example 1, the solid-state battery assembled with the negative electrode material prepared in Example 3 exhibits slightly lower cycle and rate performance. This may be because the porous carbon nanotubes used as the substrate have a finer diameter, resulting in lower pore volume after activation. This makes it easier for silicon to float to the surface with the same amount of silicon deposition, leading to increased powder resistance of the negative electrode material and consequently affecting its cycle and rate performance. In contrast, the solid-state battery assembled with the negative electrode material prepared in Comparative Example 1 shows a significant decrease in cycle and rate performance, possibly due to the excessively fine diameter of the porous carbon nanotubes used as the substrate, equivalent only to the pore size of conventional carbon nanotubes (10-50 nm).

[0327] Comparing Examples 1, 5, and 6, it can be seen that the amount of deposited silicon affects the electrochemical performance; the higher the silicon content, the higher the capacity, but the resistance and electrochemical expansion will be higher.

[0328] Comparing Examples 1 and 7-9, it can be seen that the addition of two-dimensional conductive carbon material (Example 7) increases its conductivity in a plane, resulting in improved initial coulombic efficiency, cycle retention, and rate performance. The addition of elastic fibers (Example 8) makes the negative electrode paper softer and reduces its swelling rate after cycling. The addition of elastic fibers, along with copper modification of nanocellulose (Example 9), opens the strong hydrogen bonds of cellulose, enabling it to have effective lithium-ion transport capabilities, thus improving rate performance and cycle retention.

[0329] Comparing Examples 1 and 10, it can be seen that reducing the amount of silicon-carbon anode dispersant resulted in lower dispersion stability of the paper pulp, uneven anode paper, and a decrease in its electrochemical performance.

[0330] Comparing Examples 1 and 11-12, it can be seen that reducing the amount of electronic / ionic conductive agent slurry B and fiber dispersion emulsion C respectively will lead to a decrease in the dispersion stability of the paper pulp. Reducing the amount of electronic / ionic conductive agent slurry B will result in a higher negative electrode paper resistance. Although the capacity is improved, the initial coulombic efficiency and rate capacity are lower, and the expansion rate is higher. Reducing the amount of fiber dispersion emulsion C will result in a significant increase in the expansion rate on the basis of the already low initial coulombic efficiency and rate capacity.

[0331] Comparing Examples 1 and 13, it can be seen that using ethylenediamine vapor as a reducing agent results in a weaker reducing power than hydrazine hydrate vapor, thus the resistance will be slightly higher, but the electrochemical performance is still at the same level as in Example 1.

[0332] Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that replacing the one-dimensional conductive carbon material with a two-dimensional conductive carbon material (Comparative Example 2) and a three-dimensional conductive carbon material (Comparative Example 3) respectively leads to a significant reduction in the cycle retention rate and rate capability of the solid-state battery assembled with the prepared negative electrode material.

[0333] Comparing Example 1 and Comparative Example 4, it can be seen that the resistance of the negative electrode paper increases significantly and the overall electrochemical performance decreases significantly due to the lack of reduction treatment.

[0334] The above-described embodiments are preferred embodiments, but the scope of protection of the present invention is not limited thereto. Those skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A method for preparing flexible negative electrode paper for solid-state batteries, characterized in that, include: (S1) Nitrogen-containing molecules are mixed uniformly with transition metal salts and carbon nanotubes are obtained by catalytic pyrolysis reaction. Then, porous carbon nanotubes are obtained by physical activation to create pores. Using the porous carbon nanotubes as a substrate, silicon carbon anodes are obtained by silicon deposition and carbon coating in sequence. The carbon nanotubes prepared by the catalytic pyrolysis have an average diameter of 100~800 nm. (S2) A silicon-carbon dispersion A is obtained by mixing silicon-carbon anode, dispersant and solvent I; an electronic / ionic conductive slurry B is obtained by mixing conductive carbon material, solid electrolyte, polymer and solvent II; a fiber dispersion emulsion C is obtained by mixing nanocellulose and solvent III; and a papermaking pulp is obtained by mixing and dispersing silicon-carbon dispersion A, electronic / ionic conductive slurry B and fiber dispersion emulsion C. The conductive carbon material includes one-dimensional carbon material and optionally added two-dimensional carbon material. (S3) The paper pulp is coated onto a substrate and then reduced by an amine-containing small molecule reducing agent to obtain the flexible negative electrode paper for solid-state batteries.

2. The method for preparing flexible negative electrode paper for solid-state batteries according to claim 1, characterized in that, In step (S1): The nitrogen-containing molecule is selected from one or more of urea, dicyandiamide, molecules with a triazine structure and their hybrid derivatives, amino acids and their derived polypeptides; The transition metal salt has cations including one or more of Fe(III / II), Co(II), Ni(II), Cu(II), Zn(II), and Mn(II), and anions including one or more of nitrate, chloride, and sulfate. The mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.1~1.5). The catalytic pyrolysis is performed at a temperature of 600~1000℃.

3. The method for preparing flexible negative electrode paper for solid-state batteries according to claim 1, characterized in that, In step (S1), the physical activation pore formation satisfies at least one of the following A~D: A. The physical activation pore-forming method uses an activator selected from one or more of CO, CO2, water vapor, and oxygen; B. The physical activation pore-forming method uses an activator flow rate of 0.1~20L / min; C. The physical activation pore-forming process is carried out at a temperature of 600~1200℃; D. The physical activation pore-forming process takes 1-15 hours; The silicon deposition satisfies at least one of the following a to f: a. The silicon deposition process uses a silicon source gas as the raw material gas; b. For the silicon deposition, the flow rate of the raw material gas is 1~200 L / h; c. The silicon deposition temperature is 300~600℃; d. The silicon deposition time is 1~50h; e. The silicon deposition process further includes a carrier gas in the feed gas; f. Taking the total volume of the feed gas as 100%, the volume ratio of the carrier gas is 1-30%; The carbon coating satisfies at least one of the following 1) to 6): 1) The carbon coating uses carbon-containing gases as raw materials; 2) The carbon coating refers to a carbon-containing gas selected from one or more of C1-C4 alkanes, C2-C4 alkenes, and C2-C4 alkynes; 3) The carbon coating is performed with a raw gas flow rate of 1~100 L / h; 4) The carbon coating is applied at a temperature of 400~1200℃; 5) The carbon coating time is 1~20h; 6) The carbon coating also includes inert gas in the raw material gas. The volume ratio of inert gas is 1-30% based on the total volume of the raw material gas as 100%.

4. The method for preparing flexible negative electrode paper for solid-state batteries according to claim 1, characterized in that, In step (S2), The dispersant is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives. Solvent I is selected from deionized water and / or N-methylpyrrolidone; In silicon-carbon dispersion A, the mass ratio of silicon-carbon negative electrode, dispersant and solvent I is 10:(0.01~5):(10~300); The one-dimensional carbon material is selected from one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon fibers. The two-dimensional carbon material is selected from graphene oxide; The solid electrolyte is selected from one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium silicon oxide, and lithium lanthanum titanium oxide. The polymer is selected from one or more of carboxymethyl cellulose and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, polyketone and its derivatives, polyvinylidene fluoride and its derivatives, polyoxyethylene and its derivatives, and polyvinyl alcohol and its derivatives. Solvent II is selected from deionized water and / or N-methylpyrrolidone; In electronic / ionic conductive paste B, the mass ratio of conductive carbon material, solid electrolyte, polymer and solvent II is 1:(0.1~10):(0.1~10):(10~300). The mass ratio of one-dimensional carbon material to two-dimensional carbon material is 1:(0~1); The nanocellulose has a diameter of 1~50nm and a length of 30~100μm; Solvent III is selected from deionized water and / or N-methylpyrrolidone; The solid content of fiber dispersion emulsion C is 1~50wt%; The mass ratio of silicon carbon dispersion A, electronic / ionic conductive paste B and fiber dispersion emulsion C is 10:(1~10):(1~10).

5. The method for preparing flexible negative electrode paper for solid-state batteries according to claim 1, characterized in that, In step (S2), the fiber dispersion emulsion C satisfies at least one of the following (1) to (2): (1) The fiber dispersion emulsion C also includes elastic fibers; The elastic fiber is selected from one or more of polytetrafluoroethylene fiber, polyvinylidene fluoride fiber, and polysiloxane fiber; The mass ratio of nanocellulose to elastic fiber is (0.2~5):1; (2) The nanocellulose undergoes copper modification treatment, specifically including: Copper-modified nanocellulose was obtained by immersing nanocellulose in an aqueous solution of copper salt and washing it. The concentration of the copper salt aqueous solution is 1~20wt%.

6. The method for preparing flexible negative electrode paper for solid-state batteries according to claim 1, characterized in that, In step (S3), The amine-based small molecule reducing agent is selected from hydrazine hydrate and / or ethylenediamine; The amine-based small molecule reducing agent is reduced in a vapor state; The vapors of amine-containing small molecule reducing agents also include water vapor; Based on the total mass of steam (100%), the mass fraction of the amine-based small molecule reducing agent is 0.1% to 3%. The reduction treatment temperature is 80~120℃.

7. The method for preparing flexible negative electrode paper for solid-state batteries according to any one of claims 1 to 6, characterized in that: In step (S1), the mass ratio of nitrogen-containing molecules to transition metal salts is 10:(0.25~0.75). In step (S2), the mass ratio of silicon carbon dispersion A, electronic / ionic conductive paste B and fiber dispersion emulsion C is 10:(2.5~5):(2.5~5).

8. A flexible negative electrode paper for solid-state batteries prepared by the method according to any one of claims 1 to 7.

9. A negative electrode sheet, characterized in that, It is prepared by impregnating the flexible negative electrode paper for solid-state batteries as described in claim 8 with electrolyte.

10. A solid-state battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

Images