Preparation process of sodium metal battery without negative electrode and sodium metal battery without negative electrode

Abstract

The application provides a preparation process of a negative-electrode-free sodium metal battery and the negative-electrode-free sodium metal battery. The preparation process comprises the following steps: preparing a positive electrode sheet; mixing an acrylic ester monomer, a polyester polymer and an initiator to obtain a first mixture, then adding an oxide solid-state electrolyte to obtain a second mixture, and adding a liquid electrolyte into the second mixture to obtain a third mixture; spacing the positive electrode sheet and a negative electrode current collector by using a separation film, assembling a bare battery, and then packaging, filling the third mixture and sealing; and polymerizing and pressurizing after heating. The solid-state electrolyte and the negative electrode current collector are compounded, so that the sodium dendrite problem existing in the negative-electrode-free sodium metal battery can be solved, and the cycle, rate and initial coulomb efficiency of the negative-electrode-free sodium metal battery can be improved.

Description

Fabrication process and sodium metal battery without negative electrode Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a preparation process and a sodium metal battery without a negative electrode. Background Technology

[0002] As lithium-ion battery technology expands its application in consumer electronics, electric vehicles, and energy storage, the problem of insufficient lithium resources is becoming increasingly prominent. Sodium-based batteries are gaining attention due to the Earth's sufficiently high sodium abundance and hold a strategically important position in cost-sensitive applications such as energy storage. However, the low specific capacity of sodium-ion batteries limits their large-scale application.

[0003] In contrast, the sodium metal battery without a negative electrode has no sodium ion intercalation material on the negative electrode side, only a negative electrode current collector. After the initial charging process, it can work as the negative terminal of the sodium metal battery, thereby providing a higher operating voltage and significantly improving the volumetric energy density and gravimetric energy density due to the reduction in battery volume and weight.

[0004] However, sodium metal batteries without a negative electrode currently face two main problems: First, due to the limited amount of active sodium in the battery, the SEI film is constantly consuming sodium ions and undergoing rupture and reconstruction due to the volume change of deposited sodium metal, resulting in extremely rapid capacity decay. Second, during the repeated insertion and extraction of sodium ions, without the constraint of a negative electrode material, sodium ions tend to exhibit an uneven deposition pattern on the current collector, resulting in "dead sodium," which affects the capacity utilization and coulombic efficiency of the battery without a negative electrode.

[0005] Therefore, compared to electrodes with negative electrode active materials, sodium metal-free batteries suffer from more prominent sodium dendrite growth issues in their negative electrode current collectors, leading to problems such as rapid capacity decay and low coulombic efficiency. Thus, there is an urgent need for a new negative electrode current collector or a sodium metal-free battery to meet the demands for high-capacity and high-safety performance while further improving sodium dendrite growth, cycle life, and coulombic efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a process for preparing a sodium metal battery without a negative electrode and the sodium metal battery without a negative electrode. This process can effectively suppress sodium dendrites and improve the cycle and rate performance of the battery while maintaining the high capacity of the sodium metal battery without a negative electrode.

[0007] To achieve the above objectives, the present invention provides a process for preparing a sodium metal battery without a negative electrode, comprising the following steps:

[0008] (1) Preparation of positive electrode sheet;

[0009] (2) Mix acrylate monomers, polyester polymers and initiators to obtain a first mixture, then add an oxide solid electrolyte to obtain a second mixture, and add a liquid electrolyte to the second mixture to obtain a third mixture;

[0010] (3) After separating the positive electrode and the negative electrode current collector with a separator and assembling them into a bare cell, the cell is packaged, filled with the third mixture and sealed.

[0011] (4) Heating polymerization followed by pressure formation.

[0012] In the fabrication process of the electrodeless sodium metal battery of the present invention, an acrylate monomer is polymerized by heating and then crosslinked with a polyester polymer to form a framework that encapsulates the oxide solid electrolyte, thereby forming an inorganic-organic composite solid electrolyte. After heating and polymerization, pressure formation is applied. Under external pressure, the solid composite solid electrolyte is in close contact with the solid negative electrode current collector, which reduces interfacial impedance and prevents uneven deposition of sodium ions on the negative electrode current collector during repeated insertion and extraction, thus reducing sodium ion loss. In addition, the pressure applied during formation can control the nucleation shape of sodium metal, enhance orientation, prevent the formation of sodium dendrites, and make the deposition more uniform, thereby improving the initial coulombic efficiency and capacity of the battery. The oxide solid electrolyte encapsulated by the framework can improve the conductivity of the solid electrolyte. Therefore, the present invention combines the solid electrolyte and the negative electrode current collector, which not only solves the sodium dendrite problem existing in electrodeless sodium metal batteries, but also improves the cycle life, rate capability, and initial coulombic efficiency of electrodeless sodium metal batteries.

[0013] As one technical solution of the present invention, the acrylate monomers include at least one of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, and the polyester polymers include polyethylene glycol diacrylate (PEGDA) and / or polypropylene glycol diacrylate (PPGDA).

[0014] As one technical solution of the present invention, the mass ratio of the acrylate monomer to the polyester polymer is 1-5:1-5.

[0015] As one technical solution of the present invention, the sum of the masses of the acrylate monomer and the polyester polymer is m, the mass of the initiator is n, n / m is 0.001 to 0.010, and the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

[0016] As one technical solution of the present invention, the sum of the masses of the acrylate monomer and the polyester polymer is m, the mass of the oxide solid electrolyte is p, p / m is 0.10 to 0.50, and the oxide solid electrolyte includes at least one of LLZO, LATP, LAGP and LLTO.

[0017] As one technical solution of the present invention, the mass ratio of the liquid electrolyte to the second mixture is 1-9:1-9.

[0018] As a technical solution of the present invention, the liquid electrolyte includes a sodium salt and a non-aqueous organic solvent. The sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate borate), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide. The non-aqueous organic solvent includes at least one of carbonate, carboxylic acid ester, and lactone.

[0019] As one technical solution of the present invention, the heating polymerization temperature is 40-90°C and the time is 6-12 hours.

[0020] As one technical solution of the present invention, the heating polymerization is followed by standing for 36 to 60 hours and then undergoing formation at 200 to 1200 kPa.

[0021] A second aspect of the present invention provides a sodium metal battery without a negative electrode, comprising a positive electrode sheet, a separator, a negative electrode current collector, and a solid electrolyte, wherein the solid electrolyte is at least composite on the surface of the negative electrode current collector. Detailed Implementation

[0022] The non-negative electrode sodium metal battery of the present invention includes a positive electrode sheet, a separator, a negative electrode current collector, and a solid electrolyte, wherein the solid electrolyte is at least composited on the surface of the negative electrode current collector. In other words, the solid electrolyte may be composited on both surfaces of the negative electrode current collector and also on both surfaces of the separator.

[0023] The positive electrode sheet includes positive electrode active material, positive electrode conductive agent, and positive electrode binder. Positive electrode active material includes α-NaFeO2, NaCoO2, and Na... 0.7 [Fe 0.7 Mn 0.3 O2, Na(Mn) 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, NaMnO2, Na 0.5 [Fe 1 / 2 Mn 1 / 2 O2, Na 0.67 [Fe 1 / 2 Mn 1 / 2O2, Na[Ni 0.35 Fe 0.40 Mn 0.25 O2, Na[Ni 0.30 Fe 0.45 Mn 0.25 O2, Na[Ni 0.25 Fe 0.50 Mn 0.25 O2, Na[Ni 0.20 Fe 0.55 Mn 0.25 O2, Na 0.67 [Mn 0.60 Ni 0.15 Fe 0.25 O2, Na[Li 0.05 (Ni 0.25 Fe 0.25 Mn 0.5 ) 0.95 ]O2, Na2FePO4F, Na4Fe2(CN)6, NaNi 0.33 Fe 0.33 Mn 0.33 The positive electrode active material includes at least one of the following: O2, NaFePO4, Na2FeP2O7, Na2MnPO4F, NaCoPO4, Na3V2(PO4)3, NaCrO2, and Na2Fe2(SO4)3. The positive electrode active material includes not only the above-mentioned materials but also their corresponding coating and doping materials. The positive electrode conductive agent includes at least one of the following: conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene. The positive electrode binder includes polyvinylidene fluoride. The mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder can be 90–98:1–5:1–5.

[0024] There are no particular restrictions on the separator; it can be made of polypropylene, polyethylene, paper, glass fiber, fiber resin, non-woven fabric, etc. The negative electrode current collector can be copper foil.

[0025] Solid electrolytes include sodium salts and polymer electrolytes. Polymer electrolytes are formed by polymerizing acrylate monomers and then crosslinking them with polyester polymers to encapsulate an oxide solid electrolyte. Sodium salts include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate borate), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide. Acrylate monomers include at least one of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate. Polyester polymers include polyethylene glycol diacrylate and / or polypropylene glycol diacrylate. Oxide solid electrolytes include at least one of LLZO, LATP, LAGP, and LLTO.

[0026] The fabrication process of the sodium metal battery without a negative electrode of the present invention includes the following steps:

[0027] (1) Preparation of positive electrode sheet;

[0028] (2) Mix acrylate monomers, polyester polymers and initiators to obtain a first mixture, then add an oxide solid electrolyte to obtain a second mixture, and add a liquid electrolyte to the second mixture to obtain a third mixture;

[0029] (3) After separating the positive electrode and the negative electrode current collector with a separator and assembling them into a bare cell, the cell is packaged, filled with the third mixture and sealed.

[0030] (4) Heating polymerization followed by pressure formation.

[0031] In step (1), the positive electrode sheet can be a conventional all-solid-state battery electrode sheet. The positive electrode active material, positive electrode conductive agent, and positive electrode binder are mixed to form a positive electrode slurry, which is then coated onto aluminum foil, dried, and rolled to obtain the positive electrode sheet. The positive electrode active material includes α-NaFeO2, NaCoO2, and Na... 0.7 [Fe 0.7 Mn 0.3 O2, Na(Mn) 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, NaMnO2, Na 0.5 [Fe 1 / 2 Mn 1 / 2 O2, Na 0.67 [Fe 1 / 2 Mn 1 / 2 O2, Na[Ni 0.35 Fe 0.40 Mn 0.25 O2, Na[Ni 0.30 Fe 0.45 Mn 0.25 O2, Na[Ni 0.25 Fe 0.50 Mn 0.25 O2, Na[Ni 0.20 Fe 0.55 Mn 0.25 O2, Na 0.67 [Mn 0.60 Ni 0.15 Fe 0.25 O2, Na[Li 0.05 (Ni 0.25 Fe 0.25 Mn 0.5 ) 0.95 ]O2, Na2FePO4F, Na4Fe2(CN)6, NaNi0.33 Fe 0.33 Mn 0.33 At least one of O2, NaFePO4, Na2FeP2O7, Na2MnPO4F, NaCoPO4, Na3V2(PO4)3, NaCrO2, and Na2Fe2(SO4)3. The positive electrode active material includes not only the above materials but also their corresponding coating and doping materials. The positive electrode conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene. The positive electrode binder includes polyvinylidene fluoride. The positive electrode slurry is prepared using NMP as the organic solvent. The mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder can be 90–98:1–5:1–5.

[0032] In step (2), the acrylate monomers include at least one of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate. The polyester polymers include polyethylene glycol diacrylate (PEGDA) and / or polypropylene glycol diacrylate (PPGDA). The mass ratio of the acrylate monomers to the polyester polymers is 1 to 5:1 to 5. As an example, the mass ratio may be, but is not limited to, 1:1, 1:2, 1:3, 1:4, 1:5, 3:1, 3:2, 3:4, 3:5, 5:1, 5:2, 5:3, 5:4, 2:3, and 4:5. The sum of the masses of the acrylate monomers and the polyester polymers is m, and the mass of the initiator is n, with n / m ranging from 0.001 to 0.010. For example, n / m may be, but is not limited to, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or 0.010. The initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate. The mass of the oxide solid electrolyte is p, with p / m ranging from 0.10 to 0.50. For example, p / m may be, but is not limited to, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.50. The oxide solid electrolyte includes at least one of LLZO, LATP, LAGP, and LLTO.

[0033] The injected electrolyte comprises a sodium salt and a non-aqueous organic solvent. The sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate borate), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide. The non-aqueous organic solvent is selected from at least one of carbonates, carboxylic acid esters, and lactones. Specifically, the non-aqueous organic solvent may be, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), amyl carbonate, vinyl carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), butyl acetate (n-Ba), γ-butyrolactone (γ-Bt), propyl propionate (n-PP), ethyl propionate (EP), and ethyl butyrate (Eb). The mass ratio of the liquid electrolyte and the second mixture is 1 to 9:1 to 9. For example, the mass ratio of the two can be, but is not limited to, 1:1, 1:3, 1:5, 1:7, 1:9, 5:1, 5:3, 5:6, 5:7, 5:9, 9:1, 9:3, 9:5, 9:7, and 9:8.

[0034] In step (3), the bare cell can be a wound cell or a stacked cell. A stacked cell is made by stacking a negative electrode current collector, a separator, and a positive electrode sheet in sequence to form a laminate, and then stacking multiple laminates. A wound cell is made by winding a single laminate. The bare cell is sealed in a packaging bag and filled with liquid and sealed to obtain a precursor for a sodium metal battery without a negative electrode. After polymerization and formation, a solid electrolyte is formed on the negative electrode current collector inside the packaging bag. Since the third mixture is fluid, it fills the inside of the packaging bag after liquid injection. Therefore, the solid electrolyte formed after polymerization and formation exists not only on the surface of the negative electrode current collector, but also on the surface of the separator and the positive electrode sheet. In any case, the solid electrolyte can be composited on the negative electrode current collector. This composite structure not only solves the safety problems caused by liquid electrolyte, but the presence of solid electrolyte can also solve the sodium dendrite problem of sodium metal batteries without a negative electrode.

[0035] In step (4), the heating polymerization temperature is 40–90°C. For example, the temperature can be, but is not limited to, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C. The time is 6–12 hours. For example, the time can be, but is not limited to, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. Heating allows acrylate monomers to polymerize under the action of an initiator and crosslink with polyester polymers to form a skeleton encapsulating the oxide solid electrolyte, thus forming an inorganic-organic composite solid electrolyte. After heating polymerization, the mixture is allowed to stand for 36–60 hours. For example, the standing time can be, but is not limited to, 36 hours, 40 hours, 44 hours, 48 ​​hours, 50 hours, 54 hours, 58 hours, or 60 hours. The formation pressure is 200–1200 kPa. For example, the pressure can be, but is not limited to, 200 kPa, 400 kPa, 600 kPa, 800 kPa, 1000 kPa, or 1200 kPa. Pressurizing during formation allows the solid composite solid electrolyte to fully contact the solid negative electrode current collector, which can reduce the interfacial impedance and prevent sodium ions from exhibiting uneven deposition on the negative electrode current collector during repeated insertion and extraction.

[0036] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0037] Example 1

[0038] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0039] (1) Preparation of positive electrode sheet

[0040] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0041] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 2:3. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.4 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. Then, LLZO is added at a mass ratio of 45 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a second mixture. A liquid electrolyte is added to the second mixture, and the mixture is stirred until homogeneous to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 5:2. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0042] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0043] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed at 800 kPa.

[0044] Example 2

[0045] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0046] (1) Preparation of positive electrode sheet

[0047] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0048] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 5:2. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.9 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. Then, LLZO is added at a mass ratio of 30 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a second mixture. A liquid electrolyte is added to the second mixture, and the mixture is stirred until homogeneous to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 8:1. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 3:1.

[0049] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0050] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed at 800 kPa.

[0051] Example 3

[0052] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0053] (1) Preparation of positive electrode sheet

[0054] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0055] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 1:1. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.2 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. Then, LLZO (LLZO) at a mass ratio of 50 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate is added and stirred until homogeneous to obtain a second mixture. A liquid electrolyte is then added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 2:7. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0056] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0057] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed at 800 kPa.

[0058] Example 4

[0059] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0060] (1) Preparation of positive electrode sheet

[0061] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.35 Fe 0.40 Mn 0.25O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:3:1 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0062] (2) Ethyl acrylate and polypropylene glycol diacrylate are mixed at a mass ratio of 2:3. Azobisisobutyronitrile (AIORT) at a mass ratio of 0.4 wt.% of the sum of the masses of ethyl acrylate and polypropylene glycol diacrylate is added and mixed thoroughly to obtain a first mixture. Then, LLTO at a mass ratio of 45 wt.% of the sum of the masses of ethyl acrylate and polypropylene glycol diacrylate is added and mixed thoroughly to obtain a second mixture. A liquid electrolyte is then added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 5:2. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0063] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0064] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed at 800 kPa.

[0065] Example 5

[0066] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0067] (1) Preparation of positive electrode sheet

[0068] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0069] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 2:3. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.4 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. Then, LLZO is added at a mass ratio of 45 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a second mixture. A liquid electrolyte is added to the second mixture, and the mixture is stirred until homogeneous to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 5:2. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0070] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0071] (4) The battery was polymerized at 90°C for 7 hours and then allowed to stand for 40 hours before being formed at 1000 kPa.

[0072] Comparative Example 1

[0073] This comparative example illustrates a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0074] (1) Preparation of positive electrode sheet

[0075] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0076] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 2:3. Azobisisobutyronitrile (AIBN) is added at a mass ratio of 0.4 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. A liquid electrolyte is then added to the first mixture to obtain a second mixture. The mass ratio of the liquid electrolyte to the first mixture is 5:2. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0077] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0078] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed at 800 kPa.

[0079] Comparative Example 2

[0080] This comparative example illustrates a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0081] (1) Preparation of positive electrode sheet

[0082] The sodium nickel iron cobalt manganese oxide material Na(Mn) with a maximum charging voltage of 4.2V was used. 0.25 Fe 0.25 Co 0.25 Ni 0.25 O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2:3 to prepare a positive electrode slurry of a certain viscosity. The mixed positive electrode slurry is coated on both sides of aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0083] (2) Methyl methacrylate and polyethylene glycol diacrylate are mixed at a mass ratio of 2:3. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.4 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a first mixture. Then, LLZO is added at a mass ratio of 45 wt.% of the sum of the masses of methyl methacrylate and polyethylene glycol diacrylate, and the mixture is stirred until homogeneous to obtain a second mixture. A liquid electrolyte is added to the second mixture, and the mixture is stirred until homogeneous to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 5:2. The liquid electrolyte is 1M sodium hexafluorophosphate + a non-aqueous organic solvent, and the non-aqueous organic solvent is a mixture of EC and EMC solvents at a volume ratio of 2:3.

[0084] (3) After separating the positive electrode sheet and copper foil with a separator and assembling them into a bare cell, package it, fill it with a third mixture and seal it.

[0085] (4) The battery was polymerized at 75°C for 9 hours and then allowed to stand for 48 hours before being formed under normal pressure.

[0086] Electrochemical performance tests were conducted on the sodium metal batteries without negative electrodes prepared in Examples 1-5 and Comparative Examples 1-2. The test conditions are as follows, and the test results are shown in Table 1.

[0087] (1) First Coulomb efficiency test

[0088] The sodium metal battery without a negative electrode is subjected to aging, formation, sealing and capacity testing using conventional methods. The charging capacity during the formation process is denoted as C1, the charging capacity during the capacity testing process is denoted as C2, and the discharging capacity during the capacity testing process is denoted as C0.

[0089] First Coulomb efficiency = C0 / (C1+C2)×100%

[0090] (2) Room temperature cycling performance test

[0091] The sodium metal battery without a negative electrode was placed in an environment of 25°C and charged at a constant current of 1C to 4.0V, then charged at a constant voltage to 0.05C, and then discharged at a constant current of 1C to 2.0V. This cycle was repeated for 500 cycles. The discharge capacity of the first cycle and the discharge capacity of the last cycle were recorded. The capacity retention rate of the room temperature cycle was calculated according to the following formula.

[0092] Capacity retention rate = (Discharge capacity in the last cycle / Discharge capacity in the first cycle) × 100%

[0093] (3) Ratio Performance Test

[0094] The sodium metal battery without a negative electrode was charged to 4.0V at a constant current of 0.5C, then charged to 0.05C at a constant voltage, and then discharged to 2.0V at a constant current. The discharge capacity was recorded as C0. The battery was then charged to 4.0V again using the above method, and then discharged at a current of 3C. The discharge capacity was recorded as C1.

[0095] Capacity retention rate = C1 / C0 * 100%

[0096] Table 1. Electrochemical performance test results of Examples 1-5 and Comparative Examples 1-2

[0097]

[0098] As shown in Table 1, the inorganic-organic composite solid electrolyte formed by polymerizing acrylate monomers and then crosslinking them with polyester polymers to encapsulate the oxide solid electrolyte, after pressurized formation onto the negative electrode current collector, results in a sodium metal-free battery with higher initial coulombic efficiency, cycle performance, and rate performance. This is because the oxide solid electrolyte encapsulated by the framework improves the conductivity of the solid electrolyte, thus enhancing the rate performance. Furthermore, pressurized formation after polymerization ensures that the solid composite solid electrolyte is in close contact with the solid negative electrode current collector, reducing interfacial impedance and preventing uneven deposition of sodium ions on the current collector during repeated insertion and extraction, thereby reducing sodium ion loss. The pressurized formation also controls the nucleation shape of sodium metal, enhancing orientation, preventing sodium dendrite formation, and resulting in more uniform deposition, thus improving the initial coulombic efficiency and capacity of the battery.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A fabrication process for a sodium metal battery without a negative electrode, characterized in that, The process includes the following steps: (1) preparing a positive electrode sheet; (2) mixing acrylate monomers, polyester polymers and initiators to obtain a first mixture, then adding an oxide solid electrolyte to obtain a second mixture, and adding a liquid electrolyte to the second mixture to obtain a third mixture; (3) using a separator membrane to separate the positive electrode sheet and the negative electrode current collector and assembling them into a bare battery cell, then packaging it, filling it with the third mixture and sealing it; (4) heating and polymerizing and then pressurizing to form the liquid electrolyte, wherein the liquid electrolyte includes sodium salts and non-aqueous organic solvents, wherein the sodium salts include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate and sodium bis(trifluoromethanesulfonyl)imide, and wherein the non-aqueous organic solvents include at least one of carbonates, carboxylic esters and lactones.

2. The fabrication process of the negative electrode-free sodium metal battery according to claim 1, characterized in that, The acrylate monomers include at least one of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, and the polyester polymers include polyethylene glycol diacrylate and / or polypropylene glycol diacrylate.

3. The fabrication process of the negative electrode-free sodium metal battery according to claim 1, characterized in that, The mass ratio of the acrylate monomer to the polyester polymer is 1~5:1~5.

4. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, The sum of the masses of the acrylate monomers and the polyester polymers is m, the mass of the initiator is n, n / m is 0.001~0.010, and the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

5. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, The sum of the masses of the acrylate monomers and the polyester polymers is m, the mass of the oxide solid electrolyte is p, the p / m ratio is 0.10~0.50, and the oxide solid electrolyte includes at least one of LLZO, LATP, LAGP and LLTO.

6. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, The mass ratio of the liquid electrolyte to the second mixture is 1~9:1~9.

7. The fabrication process of the negative electrode-free sodium metal battery according to claim 1, characterized in that, The heating polymerization is carried out at a temperature of 40~90℃ for 6~12 hours.

8. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, After heating and polymerization, the mixture is allowed to stand for 36-60 hours and then undergoes formation at 200-1200 kPa.

9. A sodium-metal battery without a negative electrode prepared by the preparation process of a sodium-metal battery without a negative electrode according to any one of claims 1 to 8, characterized in that, It includes a positive electrode, a separator, a negative electrode current collector, and a solid electrolyte, wherein the solid electrolyte is at least composited on the surface of the negative electrode current collector.

Images