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

Abstract

This invention provides a fabrication process for a negative electrode-free sodium metal battery and the battery itself. The fabrication process includes the following steps: preparing a positive electrode sheet; mixing an acrylate monomer, an aromatic diamine, and an initiator to obtain a first mixture, then adding a graphene oxide solution to obtain a second mixture; adding a liquid electrolyte and an ether to the second mixture to obtain a third mixture; separating the positive electrode sheet and the negative electrode current collector using a separator membrane and assembling them into a bare cell, then packaging it; filling it with the third mixture and sealing it; and finally, heating and polymerizing to form the battery. This fabrication process effectively suppresses sodium dendrites and, while maintaining the high capacity of the negative electrode-free sodium metal battery, also improves the battery's cycle performance and low-temperature performance.

Description

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 performance and low-temperature 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, aromatic diamines and initiators to obtain a first mixture, then add graphene oxide solution to obtain a second mixture, and add liquid electrolyte and ether substances 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) It is formed by heating and polymerization.

[0012] In the fabrication process of the electrodeless sodium metal battery of the present invention, acrylate monomers and aromatic diamines polymerize under the action of an initiator and heating. Some acrylate monomers can reduce graphene oxide to obtain nitrogen-doped graphene serving as a framework. Therefore, through heating polymerization and formation, a nitrogen-doped graphene hydrogel with a porous three-dimensional structure can be formed, which can improve the low-temperature performance of the electrodeless sodium metal battery. The graphene hydrogel contains ethers, which, when combined with the negative electrode current collector and formed, can form an SEI film on the surface of the current collector, reducing sodium ion consumption during the formation stage and thus improving the initial coulombic efficiency. The nitrogen doping provided by the aromatic diamine can generate active sites, inducing the uniform formation of sodium crystal nuclei and avoiding sodium ion consumption, thereby improving the capacity and cycle performance of the electrodeless sodium metal battery.

[0013] As one technical solution of the present invention, the acrylate monomers include at least one selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, and the aromatic diamines include polyethylene glycol diacrylate (PEGDA) and / or polypropylene glycol diacrylate (PPGDA). The aromatic diamines include at least one selected from o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

[0014] As one technical solution of the present invention, the mass ratio of the acrylate monomer to the aromatic diamine is 1-2:1-2.

[0015] As one technical solution of the present invention, the sum of the masses of the acrylate monomer and the aromatic diamine 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 aromatic diamine is m, the mass of the graphene oxide solution is p, p / m is 10-90%, and the graphene oxide solution has a graphene oxide mass concentration of 1.0-5.0 mg / ml.

[0017] As one technical solution of the present invention, the mass ratio of the liquid electrolyte to the second mixture is 5-50:50-95.

[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 sum of the masses of the acrylate monomer and the aromatic diamine is m, the mass of the ether substance is q, q / m is 0.01 to 0.10, and the ether substance includes at least one of dimethyl ether, tetraethylene glycol dimethyl ether and diethylene glycol diethylene dimethyl ether.

[0020] As one technical solution of the present invention, the heating polymerization temperature is 50-80°C and the time is 4-9 hours.

[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 / 2 O2, Na[Ni 0.35 Fe 0.40 Mn 0.25 O2, Na[Ni 0.30 Fe0.45 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 oxide. 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 aromatic diamines and filling them with graphene and ethers. 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. Aromatic diamines include at least one of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine. Ethers include at least one of dimethyl ether, tetraethylene glycol dimethyl ether, and diethylene glycol diethylene dimethyl ether.

[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, aromatic diamines and initiators to obtain a first mixture, then add graphene oxide solution to obtain a second mixture, and add liquid electrolyte and ether substances 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) It is formed by heating and polymerization.

[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, NaNi 0.33 Fe 0.33 Mn 0.33At 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 oxide. 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 aromatic diamine includes at least one of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine. The mass ratio of the acrylate monomers to the aromatic diamine is 1 to 2:1 to 2. For example, the mass ratio may be, but is not limited to, 1:1, 1:2, 2:1, 3:2, 3:4, 3:5, 5:3, 5:4, 2:3, and 4:5. The sum of the masses of the acrylate monomers and the aromatic diamine is m, and the mass of the initiator is n. The ratio of n / m is 0.001 to 0.010. For example, the ratio of 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, and 0.010. The initiator includes at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate. The graphene oxide solution has a mass percentage (p) of 10-90%, and the p / m ratio is 10%-90%. For example, the p / m ratio can be, but is not limited to, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%. The graphene oxide solution is an aqueous solution with a graphene oxide mass concentration of 1.0-5.0 mg / ml. For example, the concentration can be, but is not limited to, 1.0 mg / ml, 1.5 mg / ml, 2.0 mg / ml, 2.5 mg / ml, 3.0 mg / ml, 3.5 mg / ml, 4.0 mg / ml, 4.5 mg / ml, and 5.0 mg / ml. The injected electrolyte includes sodium salts and non-aqueous organic solvents. 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 5 to 50:50 to 95. For example, the mass ratio of the two can be, but is not limited to, 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:50, and 50:50.The mass of the ether is q, and q / m is 0.01 to 0.10. For example, q / m may be, but is not limited to, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10. The ether includes at least one of dimethyl ether, tetraethylene glycol dimethyl ether, and diethylene glycol diethylene dimethyl ether.

[0033] 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.

[0034] In step (4), the heating polymerization temperature is 50–80°C. For example, the temperature can be, but is not limited to, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The time is 4–9 hours. For example, the time can be, but is not limited to, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 9 hours. Heating allows acrylate monomers to polymerize with aromatic diamines under the action of an initiator, and to mix with graphene and ethers to form an inorganic-organic composite solid electrolyte. Conventional formation methods can be used at room temperature during the formation process.

[0035] 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.

[0036] Example 1

[0037] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0038] (1) Preparation of positive electrode sheet

[0039] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0040] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 1:2. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.3 wt.% of the sum of the masses of methyl methacrylate and m-phenylenediamine, and the mixture is homogeneous to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 5.0 mg / ml) is added at a mass ratio of 60 wt.% of the sum of the masses of methyl methacrylate and m-phenylenediamine, and the mixture is homogeneous to obtain a second mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 40:60. 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. The tetraethylene glycol dimethyl ether accounts for 5% of the sum of the masses of methyl methacrylate and m-phenylenediamine.

[0041] (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.

[0042] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0043] Example 2

[0044] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0045] (1) Preparation of positive electrode sheet

[0046] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0047] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 4:5. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.6 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 3.0 mg / ml) is added at a mass ratio of 60 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a second mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 30:70. 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 5:3. The tetraethylene glycol dimethyl ether accounts for 10% of the sum of the mass of methyl methacrylate and m-phenylenediamine.

[0048] (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.

[0049] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0050] Example 3

[0051] (1) Preparation of positive electrode sheet

[0052] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0053] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 5:3. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.9 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 1.0 mg / ml) is added at a mass ratio of 10 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a second mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 27:73. 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. The tetraethylene glycol dimethyl ether accounts for 2% of the sum of the mass of methyl methacrylate and m-phenylenediamine.

[0054] (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.

[0055] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0056] Example 4

[0057] (1) Preparation of positive electrode sheet

[0058] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0059] (2) Ethyl acrylate and o-phenylenediamine are mixed at a mass ratio of 1:2. Azobisisobutyronitrile (AIORT) is added at 0.3 wt.% of the total mass of ethyl acrylate and o-phenylenediamine, and the mixture is thoroughly mixed to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 5.0 mg / ml) is added at 60 wt.% of the total mass of ethyl acrylate and o-phenylenediamine, and the mixture is thoroughly mixed to obtain a second mixture. A liquid electrolyte and dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 40:60. The liquid electrolyte consists of 0.8 M sodium hexafluorophosphate, 0.2 M sodium tetrafluoroborate, and a non-aqueous organic solvent. The non-aqueous organic solvent is a mixture of EC, EMC, and DEC in a volume ratio of 1:2:3. Dimethyl ether accounts for 5% of the total mass of ethyl acrylate and o-phenylenediamine.

[0060] (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.

[0061] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0062] Example 5

[0063] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0064] This embodiment describes a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0065] (1) Preparation of positive electrode sheet

[0066] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25O2, PVDF binder and SuperP conductive agent are mixed evenly in a mass ratio of 95:2.5:2.5 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.

[0067] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 1:2. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.3 wt.% of the sum of the masses of methyl methacrylate and m-phenylenediamine, and the mixture is homogeneous to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 5.0 mg / ml) is added at a mass ratio of 60 wt.% of the sum of the masses of methyl methacrylate and m-phenylenediamine, and the mixture is homogeneous to obtain a second mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 40:60. 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. The tetraethylene glycol dimethyl ether accounts for 5% of the sum of the masses of methyl methacrylate and m-phenylenediamine.

[0068] (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.

[0069] (4) The battery was polymerized at 70°C for 6 hours and then formed.

[0070] Comparative Example 1

[0071] This comparative example illustrates a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0072] (1) Preparation of positive electrode sheet

[0073] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0074] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 1:2. Azobisisobutyronitrile (AIBN) is added at a mass ratio of 0.3 wt.% of the sum of the masses of methyl methacrylate and m-phenylenediamine, and the mixture is stirred until homogeneous to obtain a first mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are then added to the first mixture to obtain a second mixture. The mass ratio of the liquid electrolyte to the first mixture is 40:60. 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. The tetraethylene glycol dimethyl ether accounts for 5% of the sum of the masses of methyl methacrylate and m-phenylenediamine.

[0075] (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 the second mixture and seal it.

[0076] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0077] Comparative Example 2

[0078] This comparative example illustrates a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0079] (1) Preparation of positive electrode sheet

[0080] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0081] (2) Methyl methacrylate and m-phenylenediamine are mixed at a mass ratio of 1:2. Azobisisobutyronitrile (AIB) is added at a mass ratio of 0.3 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a first mixture. Then, a graphene oxide solution (an aqueous solution with a graphene oxide concentration of 5.0 mg / ml) is added at a mass ratio of 60 wt.% of the sum of methyl methacrylate and m-phenylenediamine, and the mixture is thoroughly mixed to obtain a second mixture. A liquid electrolyte is added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 40:60. 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.

[0082] (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.

[0083] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0084] Comparative Example 3

[0085] This comparative example illustrates a fabrication process for a sodium metal battery without a negative electrode, comprising the following steps.

[0086] (1) Preparation of positive electrode sheet

[0087] The sodium nickel iron cobalt manganese oxide material Na[Ni] has a maximum charging voltage of 4.2V. 0.30 Fe 0.45 Mn 0.25 O2, binder PVDF and conductive agent SuperP are mixed evenly in a mass ratio of 96:1:3 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.

[0088] (2) Azobisisobutyronitrile (AIB) at a mass of 0.3 wt.% of methyl methacrylate (MMA) is added and mixed thoroughly to obtain a first mixture. Then, a graphene oxide solution (5.0 mg / ml aqueous solution) at a mass of 60 wt.% of methyl methacrylate (MMA) is added and mixed thoroughly to obtain a second mixture. A liquid electrolyte and tetraethylene glycol dimethyl ether are added to the second mixture to obtain a third mixture. The mass ratio of the liquid electrolyte to the second mixture is 40:60. 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 at a volume ratio of 2:3. The tetraethylene glycol dimethyl ether accounts for 5% of the mass of methyl methacrylate.

[0089] (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.

[0090] (4) The battery was polymerized at 75°C for 9 hours and then formed.

[0091] Electrochemical performance tests were conducted on the sodium metal batteries without negative electrodes prepared in Examples 1-5 and Comparative Examples 1-3. The test conditions are as follows, and the test results are shown in Table 1.

[0092] (1) First Coulomb efficiency test

[0093] 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.

[0094] First Coulomb efficiency = C0 / (C1+C2)×100%

[0095] (2) Room temperature cycling performance test

[0096] 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.

[0097] Capacity retention rate = (Discharge capacity in the last cycle / Discharge capacity in the first cycle) × 100%

[0098] (3) Low temperature performance test

[0099] At room temperature (25℃), the sodium metal battery without a negative electrode was charged and discharged once at 0.05C / 0.05C (the battery discharge capacity was recorded as C0), with an upper limit voltage of 4.0V. The battery was then placed in a low temperature chamber at -10℃ and discharged at a constant current of 0.1C until the voltage reached 2.0V. The first discharge capacity of the battery was recorded. This constitutes one charge-discharge cycle. After 10 cycles, the battery was disassembled and the capacity retention rate was calculated.

[0100] Capacity retention rate = (Discharge capacity in the last cycle / Discharge capacity in the first cycle) × 100%

[0101] Table 1. Electrochemical performance test results of Examples 1-5 and Comparative Examples 1-3

[0102]

[0103] As shown in Table 1, the polymerization of acrylate monomers and aromatic diamines, followed by the formation of a nitrogen-doped graphene hydrogel with a porous three-dimensional structure using graphene, ethers, and a liquid electrolyte, and then composited onto the negative electrode current collector, results in a high initial coulombic efficiency, better cycle performance, and lower-temperature performance in the fabricated electrodeless sodium metal battery. This is because the porous three-dimensional structure of the graphene hydrogel improves the low-temperature performance of the electrodeless sodium metal battery. The ethers, when composited onto the negative electrode current collector and then formed, can form an SEI film on the surface of the current collector, reducing sodium ion consumption during the formation stage and thus improving the initial coulombic efficiency. The nitrogen doping provided by the aromatic diamine generates active sites, inducing the uniform formation of sodium crystal nuclei and avoiding sodium ion consumption, thereby improving the capacity and cycle performance of the electrodeless sodium metal battery.

[0104] 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, Including the following steps: (1) Preparation of positive electrode sheet; (2) Mix acrylate monomers, aromatic diamines and initiators to obtain a first mixture, then add graphene oxide solution to obtain a second mixture, and add liquid electrolyte and ether substances to the second mixture to obtain a third mixture; (3) After separating the positive electrode and the negative electrode current collector with a separator and assembling them into a bare cell, package it, fill it with the third mixture and seal it; (4) After heating and polymerization, 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 dioxalate 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.

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 aromatic diamines include at least one of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

3. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, The mass ratio of the acrylate monomer to the aromatic diamine is 1~2:1~2.

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 monomer and the aromatic diamine 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 monomer and the aromatic diamine is m, the mass of the graphene oxide solution is p, p / m is 10~90%, and the graphene oxide solution is an aqueous solution with a graphene oxide mass concentration of 1.0~5.0 mg / ml.

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 5~50:50~95.

7. The fabrication process of the negative electrode-free sodium metal battery according to claim 1, characterized in that, The sum of the masses of the acrylate monomer and the aromatic diamine is m, the mass of the ether is q, q / m is 0.01~0.10, and the ether includes at least one of dimethyl ether, tetraethylene glycol dimethyl ether and diethylene glycol diethylene dimethyl ether.

8. The fabrication process of the sodium metal battery without a negative electrode according to claim 1, characterized in that, The heating polymerization temperature is 50~80℃, and the time is 4~9h.

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.

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