A quasi-solid polymer electrolyte, a method for preparing the same, and an application thereof

Abstract

The embodiment of the present application relates to a kind of quasi-solid polymer electrolyte and its preparation method and application.The quasi-solid polymer electrolyte includes: electrolyte salt, organic carbonate solvent, solid polymer electrolyte matrix;Wherein, the solid polymer electrolyte matrix is formed by polymer monomer and crosslinking agent under the action of initiator polymerization, with crosslinking network structure;The organic carbonate solvent includes main solvent and fluorine-based organic solvent;The organic carbonate solvent is encapsulated in the crosslinking network structure of the solid polymer electrolyte matrix in situ.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid sodium metal batteries, in particular to a quasi-solid polymer electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Energy storage and conversion technologies play a key role in the energy transition process under the background of double carbon, and its applications include electronic products, electric vehicles and renewable energy storage. At present, lithium-ion batteries dominate the rechargeable battery market. However, the limited reserves and uneven distribution of lithium in the earth's crust make it economically unfeasible for lithium-ion batteries to be used in gigawatt-level applications (such as grid-connected stationary energy storage). From the perspective of physicochemical properties, sodium and lithium belong to the same first main group element and have similar properties. From the perspective of industrial demand, metal sodium is abundant in reserves, simple to extract and low in production cost. Therefore, sodium metal batteries using metal sodium as the negative electrode are very promising as a low-cost alternative to lithium metal batteries. Among them, sodium metal has a lower electrochemical potential (-2.714 V (relative to the standard hydrogen electrode)) and a high theoretical specific capacity (1,165 mAh g -1 ), and the use of sodium metal as the negative electrode can further improve the overall capacity of the battery.

[0003] However, due to the high reactivity of sodium metal, the rapid failure of the metal sodium negative electrode is caused by the serious dendrite growth of the sodium metal negative electrode, the thick and fragile SEI layer generated by the reaction of the electrolyte with the metal sodium, and the uncontrollable volume change. In addition, the use of highly active sodium metal and the formation of sodium dendrites during battery operation cause safety problems, especially when highly flammable liquid electrolytes are used. SUMMARY

[0004] The purpose of the present application is to overcome the defects in the prior art and provide a quasi-solid polymer electrolyte, a preparation method and application thereof. The cross-linked network of the polymer in the quasi-solid polymer electrolyte can anchor the high-reactivity solvent, avoid its continuous reduction and decomposition on the metal negative electrode surface to generate a thick and uneven SEI layer, and is beneficial to improve the reversibility of Na+ deposition / exfoliation, delay the rapid depletion of sodium ions at the negative electrode interface, limit the development of the sodium deposition morphology to dendritic morphology, and thus realize the stability of sodium metal in long-term cycling.

[0005] To achieve the above purpose, the present application provides a quasi-solid polymer electrolyte, comprising: an electrolyte salt, an organic carbonate solvent, and a solid polymer electrolyte matrix.

[0006] The solid polymer electrolyte matrix is formed by polymerization of a polymer monomer and a cross-linking agent under the action of an initiator, and has a cross-linked network structure.

[0007] The organic carbonate solvent comprises a main solvent and a fluorine-containing organic solvent; the organic carbonate solvent is encapsulated in a crosslinked network structure of the solid polymer electrolyte matrix in situ.

[0008] Preferably, the electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and NaBOB;

[0009] The polymer monomer includes one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate;

[0010] The crosslinking agent includes one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate, and ethylene glycol methyl ether acetate;

[0011] The initiator includes azobisisobutyronitrile.

[0012] Preferably, the organic carbonate solvent and the electrolyte salt are complexed together on the surface and / or inside of the solid polymer electrolyte matrix.

[0013] Preferably, the mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25;

[0014] The volume percentage content of the polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%;

[0015] The volume percentage content of the crosslinking agent in the polymer monomer is greater than 0 vol.% and less than or equal to 5 vol.%;

[0016] The mass ratio of the initiator to the polymer monomer is 0.1:100-1:20.

[0017] Preferably, the main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether;

[0018] The fluorine-containing organic solvent includes fluoroethylene carbonate;

[0019] The volume ratio of the main solvent to the fluorine-containing organic solvent is 8:1-10:1.

[0020] Preferably, the voltage window of the quasi-solid polymer electrolyte is 0-4.5V;

[0021] The sodium ion transference number of the quasi-solid polymer electrolyte is 0.3-0.9.

[0022] In a second aspect, the present application provides a preparation method of the quasi-solid polymer electrolyte according to the first aspect, characterized in that the preparation method comprises:

[0023] mixing the electrolyte salt and the organic carbonate solvent in proportion and stirring uniformly to form an electrolyte salt solution; wherein the organic carbonate solvent comprises a main solvent and a fluorine-containing organic solvent;

[0024] adding polymer monomers and a cross-linking agent into the electrolyte salt solution and stirring uniformly, and then adding an initiator and stirring uniformly to obtain an electrolyte precursor;

[0025] injecting the electrolyte precursor into a battery, packaging, and then curing at a set temperature.

[0026] Preferably, the electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and NaBOB;

[0027] The polymer monomers include one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate;

[0028] The cross-linking agent includes one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate, and ethylene glycol methyl ether acetate;

[0029] The initiator includes azobisisobutyronitrile;

[0030] The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether;

[0031] The fluorine-containing organic solvent includes fluoroethylene carbonate;

[0032] The volume ratio of the main solvent to the fluorine-containing organic solvent is 8:1-10:1;

[0033] The mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25;

[0034] The volume percentage content of the polymer monomers in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%;

[0035] The volume percentage content of the cross-linking agent in the polymer monomers is greater than 0 vol.% and less than or equal to 5 vol.%;

[0036] The mass ratio of the initiator to the polymer monomers is 0.1:100-1:20;

[0037] The set temperature is 60-80 DEG C.

[0038] In a third aspect, the embodiments of the present application provide a sodium battery comprising the quasi-solid polymer electrolyte of the first aspect.

[0039] Preferably, the sodium battery further comprises a positive electrode and a negative electrode.

[0040] The positive electrode active material of the positive electrode comprises: Na x A1[A2(CN)6] y ·zH2O, Na n MO2, NaFePO4, Na2MP2O7, Na3V2(PO4)3, Na2M2(SO4)3, V2O5; and the negative electrode is a metal sodium negative electrode.

[0041] Wherein, A1 and A2 are at least two of Mn, Fe, Co, Ni, Cu and Zn, x = 1-4, y = 1-4, and z = 0-10; M is at least one of Co, Fe, Mn and Ni, and n = 1-2.

[0042] The quasi-solid polymer electrolyte provided by the embodiments of the present application. The cross-linked network of the polymer in the quasi-solid polymer electrolyte can anchor the high-reactivity solvent, avoid its continuous reduction decomposition on the metal negative electrode surface to generate a thick and uneven SEI layer, and be beneficial to improve the Na + The deposition / peeling reversibility, the rapid depletion of sodium ions at the negative electrode interface is delayed, the deposition morphology of sodium is limited to develop into a dendritic morphology, and thus the stability of sodium metal in long-term cycling is realized. In addition, the quasi-solid polymer electrolyte matrix formed after the addition of the polymer monomer after polymerization can change the electrolyte / electrode double-layer structure, derive a more stable solid-state electrolyte interface, effectively reduce the negative electrode corrosion phenomenon in the metal battery, and further improve the electrochemical performance and cycle stability of the battery. In the quasi-solid polymer electrolyte of the present application, the organic carbonate solvent is encapsulated in the cross-linked network structure of the polymer, thereby improving the safety performance of the battery assembled by the quasi-solid polymer electrolyte. By introducing the organic carbonate solvent containing fluorinated groups, the interface compatibility, rate, coulombic efficiency and cycle charge-discharge performance of the battery are effectively improved. Therefore, the quasi-solid polymer electrolyte proposed in the present application has high interface compatibility, can inhibit the increase of impedance in the long cycle process of the battery, can improve the voltage window and ion transference number of the battery, and thus improves the service life and safety performance of the battery (such as sodium metal battery) assembled by the quasi-solid polymer electrolyte in the energy storage power station. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The electrochemical impedance spectroscopy (EIS) curves of the quasi-solid polymer electrolyte of the present application at different temperatures;

[0044] Figure 2 is the DC polarization curve of Example 1, Na||Na symmetric cell, the blue and magenta curves in the figure correspond to the EIS curves before and after polarization, respectively;

[0045] Figure 3 is the DC polarization curve of Comparative Example, Na||Na symmetric cell, the blue and magenta curves in the figure correspond to the EIS curves before and after polarization, respectively;

[0046] Figure 4 is the voltammogram of the electrochemical oxidation stability of Example 1 and Comparative Example tested by linear sweep voltammetry.

[0047] Figure 5 is the rate performance test of Example 1 and Comparative Example using fresh Na metal negative electrode;

[0048] Figure 6 Example 1 and Comparative Example were tested for long-term cycle stability at a current density of 5C using fresh Na metal negative electrode.

[0049] Figure 7 is the long-term cycle performance of Example 1 and Comparative Example, Na metal in the structure of Na||Na symmetric cell at 0.5mA cm -2 .

[0050] Figure 8 is the long-term cycle performance of Example 2 and Example 3, Na metal in the structure of Na||Na symmetric cell at 0.1mA cm -2 . DETAILED DESCRIPTION

[0051] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0052] The technical solutions of the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0053] The embodiment of the present application provides a quasi-solid polymer electrolyte, which comprises: an electrolyte salt, an organic carbonate solvent, and a solid polymer electrolyte matrix.

[0054] The solid polymer electrolyte matrix is formed by polymerization of a polymer monomer and a crosslinking agent under the action of an initiator, and has a crosslinked network structure.

[0055] The organic carbonate solvent and the electrolyte salt are complexed together on the surface and / or inside of the solid polymer electrolyte matrix.

[0056] The complexed electrolyte salt provides the ions required for the quasi-solid polymer electrolyte to conduct electricity, further improves the ionic conductivity of the quasi-solid polymer electrolyte, and reduces the battery interface resistance.

[0057] The organic carbonate solvent includes a main solvent and a fluorine-containing organic solvent; the organic carbonate solvent is encapsulated in situ in the crosslinked network structure of the solid polymer electrolyte matrix. By adding the fluorine-containing organic solvent, such as fluoroethylene carbonate, the battery interface compatibility, rate, coulombic efficiency, and cyclic charge-discharge performance can be effectively improved.

[0058] The above quasi-solid polymer electrolyte can be prepared by the preparation method shown in the following step flow. The specific selection of various substances is described in the preparation method.

[0059] The preparation method of the quasi-solid polymer electrolyte provided by the application comprises:

[0060] In step 110, the electrolyte salt and the organic carbonate solvent are mixed in proportion and stirred uniformly to form an electrolyte salt solution.

[0061] The mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25.

[0062] The electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB).

[0063] The organic carbonate solvent includes a main solvent and a fluorine-containing organic solvent; the volume ratio of the main solvent to the fluorine-containing organic solvent is 8:1-10:1; preferably 9:1. The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether; the fluorine-containing organic solvent includes fluoroethylene carbonate.

[0064] In step 120, the polymer monomer, the crosslinking agent, and the initiator are added to the electrolyte salt solution and stirred uniformly to obtain an electrolyte precursor.

[0065] The volume percentage content of the added polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%; the volume percentage content of the added crosslinking agent in the polymer monomer is greater than 0 vol.% and less than or equal to 5 vol.%; and the mass ratio of the added initiator to the polymer monomer is 0.1:100-1:20.

[0066] The polymer monomer includes one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate and butyl methacrylate; the crosslinking agent includes one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate and ethylene glycol methyl ether acetate; and the initiator includes azobisisobutyronitrile.

[0067] In step 130, the electrolyte precursor is injected into the battery, and after encapsulation, solidification is performed at a set temperature.

[0068] Specifically, the electrolyte precursor is directly injected into the battery, the electrode and the separator are well infiltrated, and then the battery is encapsulated and polymerization is initiated by heating. The set temperature is a temperature capable of initiating polymerization, and is preferably 60-80 DEG C. The solidification time is preferably 2 hours.

[0069] The electrolyte precursor with good flowability before solidification by thermal polymerization can achieve good contact with the electrode, and after solidification of the electrolyte, conformal interface contact is achieved, which can ensure uniform transmission of ions between the electrode and the electrolyte.

[0070] In the present application, the quasi-solid polymer electrolyte matrix polymerized from the above polymer monomer has high mechanical strength, and thus can effectively inhibit sodium dendrite from piercing the electrolyte. In the quasi-solid polymer electrolyte, the solid polymer electrolyte matrix serves as a skeleton and provides active sites for the electrolyte salt, thereby ensuring mechanical strength and ion transference number.

[0071] The quasi-solid polymer electrolyte of the present application can improve the problems of low ionic conductivity and poor interface compatibility of the solid-state polymer electrolyte; at the same time, the quasi-solid polymer electrolyte can also have good processability and electrochemical performance; more importantly, since the energy storage power station has a wide temperature range, compared with the battery assembled with electrolyte, the battery assembled with the quasi-solid polymer electrolyte of the present application can be more safely applied to a wider temperature range.

[0072] The quasi-solid polymer electrolyte proposed in the present application can be applied in sodium batteries, such as sodium metal batteries. The sodium metal battery also includes a positive electrode and a negative electrode. The positive electrode active material of the positive electrode includes: Na x A1[A2(CN)6] y ·zH2O, Na n At least one of MO2, NaFePO4, Na2MP2O7, Na3V2(PO4)3, Na2M2(SO4)3 and V2O5; wherein A1 and A2 are at least two of Mn, Fe, Co, Ni, Cu and Zn, x = 1-4, y = 1-4, and z = 0-10; M is at least one of Co, Fe, Mn and Ni, and n = 1-2. The negative electrode is a metal sodium negative electrode.

[0073] Sodium ions, due to their Lewis acidity and large ionic radius, exhibit weaker interactions with polar solvent molecules in liquid electrolytes and are more susceptible to the influence of other polar dipoles. In this invention, the introduction of polar polymer groups alters the coordination environment of sodium ions. Ordered ion migration on the sodium metal anode surface leads to uniform sodium deposition / stripping. Furthermore, the cross-linked network of the polymer in the solid polymer electrolyte anchors the highly reactive solvent, preventing its continuous reduction and decomposition on the metal anode surface to form a thick and uneven SE I layer, which is beneficial for improving the sodium... + The reversibility of deposition / stripping delays the rapid depletion of sodium ions at the negative electrode interface, limiting the development of sodium deposition morphology towards dendrites, thereby achieving the stability of sodium metal during long-term cycling. Furthermore, the quasi-solid polymer electrolyte matrix formed after polymerization of the added polymer monomers can alter the electrolyte / electrode double-layer structure, resulting in a more stable solid electrolyte interface, effectively reducing negative electrode corrosion within the metal battery, and further improving the electrochemical performance and cycle stability of the cell. In the quasi-solid polymer electrolyte of this invention, the organic carbonate solvent is encapsulated within the cross-linked network structure of the polymer, thereby improving the safety performance of the battery assembled with the quasi-solid polymer electrolyte. By introducing an organic carbonate solvent containing fluorinated groups, the interfacial compatibility, rate capability, coulombic efficiency, and cycle charge-discharge performance of the battery are effectively improved. The quasi-solid polymer electrolyte prepared by the in-situ curing method of this invention can achieve perfect conformal contact with the electrode, effectively improving interfacial compatibility, suppressing the increase in impedance during long-term cycling of the cell, increasing the battery's voltage window and ion transport number, thereby improving the service life and safety performance of batteries assembled with quasi-solid polymer electrolytes (e.g., sodium metal batteries) in energy storage power stations.

[0074] The quasi-solid polymer-based electrolyte of this invention has a voltage window of 0-4.5V and a sodium ion transference number of 0.3-0.9. In a specific embodiment of this invention, the conductivity of the quasi-solid polymer electrolyte is 3.06 mS / cm, and the discharge specific capacity of the sodium metal battery using the quasi-solid polymer-based electrolyte of this invention is 114 mAh / g.

[0075] The technical solutions of the present invention will be further described in detail below with reference to several specific embodiments. It should be understood that the embodiments of the present invention are merely examples, and the scope of the present invention is not limited to the processes, values, or components defined in the embodiments, as these implementations are only intended to illustrate the technical solutions of the present invention. In fact, various changes that those skilled in the art or related fields can make to the embodiments of the present invention without creative effort are all covered within the scope of the present invention.

[0076] Unless otherwise specified, all raw material components involved in the following embodiments are commercially available products well known to those skilled in the art. The weight-average molecular weight of butyl acrylate used in the following embodiments is 128.17.

[0077] Example 1

[0078] 1) Preparation of electrolyte precursors:

[0079] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0080] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide (NaFS I) and stir at room temperature for 1 hour to prepare a sodium bis(fluorosulfonyl)imide salt solution with a concentration of 1 mol / L;

[0081] ③ After adding 100 μL of butyl acrylate monomer and 5 μL of polyethylene glycol diacrylate, stir at room temperature for 1 hour to prepare a homogeneous precursor solution;

[0082] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0083] 2) Preparation of the positive electrode:

[0084] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0085] 3) Preparation of negative electrode:

[0086] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0087] 4) Assemble sodium metal batteries:

[0088] Assemble the button cell in the order of positive electrode, glass fiber, and negative electrode, and inject the electrolyte precursor into the cell. Place the assembled cell in a 60°C oven for 2 hours to cure the electrolyte precursor into a quasi-solid polymer electrolyte, thus obtaining a quasi-solid polymer-based electrolyte sodium metal battery.

[0089] Example 2

[0090] 1) Preparation of electrolyte precursors:

[0091] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0092] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide and stir at room temperature for 1 hour to prepare a sodium bis(fluorosulfonyl)imide salt solution with a concentration of 1 mol / L;

[0093] ③ Add 100 μL of 2,2,3,4,4,4-hexafluorobutyl acrylate monomer and 5 μL of polyethylene glycol diacrylate, and stir at room temperature for 1 hour to prepare a homogeneous precursor solution;

[0094] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0095] 2) Preparation of the positive electrode:

[0096] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0097] 3) Preparation of negative electrode:

[0098] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0099] 4) Assemble sodium metal batteries:

[0100] Assemble the button cell in the order of positive electrode, glass fiber, and negative electrode, and inject the electrolyte precursor into the cell. Place the assembled cell in a 60°C oven for 2 hours to cure the electrolyte precursor into a quasi-solid polymer electrolyte, thus obtaining a quasi-solid polymer-based electrolyte sodium metal battery.

[0101] Example 3

[0102] 1) Preparation of electrolyte precursors:

[0103] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0104] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide and stir at room temperature for 1 hour to prepare a sodium bis(fluorosulfonyl)imide salt solution with a concentration of 1 mol / L;

[0105] ③ After adding 100 μL of butyl methacrylate monomer and 5 μL of polyethylene glycol diacrylate, stir at room temperature for 1 hour to prepare a homogeneous precursor solution;

[0106] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0107] 2) Preparation of the positive electrode:

[0108] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0109] 3) Preparation of negative electrode:

[0110] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0111] 4) Assemble sodium metal batteries:

[0112] Assemble the button cell in the order of positive electrode, glass fiber, and negative electrode, and inject the electrolyte precursor into the cell. Place the assembled cell in a 60°C oven for 2 hours to cure the electrolyte precursor into a quasi-solid polymer electrolyte, thus obtaining a quasi-solid polymer-based electrolyte sodium metal battery.

[0113] Example 4

[0114] 1) Preparation of electrolyte precursors:

[0115] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0116] ② Add 91.2 mg of sodium bis(trifluoromethanesulfonyl)imide (NaTFS I) and stir at room temperature for 1 hour to prepare a sodium bis(trifluoromethanesulfonyl)imide salt solution with a concentration of 1 mol / L;

[0117] ③ After adding 100 μL of butyl acrylate monomer and 5 μL of polyethylene glycol diacrylate, stir at room temperature for 1 hour to prepare a homogeneous precursor solution;

[0118] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0119] 2) Preparation of the positive electrode:

[0120] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0121] 3) Preparation of negative electrode:

[0122] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0123] 4) Assemble sodium metal batteries:

[0124] Assemble the button cell in the order of positive electrode, glass fiber, and negative electrode, and inject the electrolyte precursor into the cell. Place the assembled cell in a 60°C oven for 2 hours to cure the electrolyte precursor into a quasi-solid polymer electrolyte, thus obtaining a quasi-solid polymer-based electrolyte sodium metal battery.

[0125] Example 5

[0126] 1) Preparation of electrolyte precursors:

[0127] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0128] ② Add 50.4 mg of sodium hexafluorophosphate (NaPF6) and stir at room temperature for 1 hour to prepare a sodium hexafluorophosphate solution with a concentration of 1 mol / L;

[0129] ③ After adding 100 μL of butyl acrylate monomer and 5 μL of polyethylene glycol diacrylate, stir at room temperature for 1 hour to prepare a homogeneous precursor solution;

[0130] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0131] 2) Preparation of the positive electrode:

[0132] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0133] 3) Preparation of negative electrode:

[0134] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0135] 4) Assemble sodium metal batteries:

[0136] Assemble the button cell in the order of positive electrode, glass fiber, and negative electrode, and inject the electrolyte precursor into the cell. Place the assembled cell in a 60°C oven for 2 hours to cure the electrolyte precursor into a quasi-solid polymer electrolyte, thus obtaining a quasi-solid polymer-based electrolyte sodium metal battery.

[0137] Comparative example

[0138] 1) Preparation of electrolytes:

[0139] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0140] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide and stir at room temperature for 1 hour to prepare a sodium bis(fluorosulfonyl)imide salt solution with a concentration of 1 mol / L as an electrolyte precursor.

[0141] 2) Preparation of the positive electrode:

[0142] Sodium vanadium phosphate (NVP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were dispersed in N-methylpyrrolidone and stirred to obtain a uniform positive electrode slurry. The solid components included 80 wt.% NVP, 1 wt.% conductive carbon black, and 1 wt.% PVDF, with a viscosity of 9000 mPa·s. The positive electrode slurry was uniformly coated on the surface of carbon-coated aluminum foil and baked in an oven at 80°C for 12 hours to obtain the positive electrode sheet.

[0143] 3) Preparation of negative electrode:

[0144] The sodium metal block was removed from the kerosene and dried; after removing the oxidized part of the sodium metal surface, it was rolled thin and then slit to obtain a negative electrode sheet with a diameter of 10 mm.

[0145] 4) Assemble sodium metal batteries:

[0146] A button cell is assembled by combining the positive electrode, glass fiber, and negative electrode in that order, and then the electrolyte is injected into the cell to obtain a sodium metal battery.

[0147] The above embodiments and comparative examples were tested and analyzed.

[0148] 1. Electrochemical impedance spectroscopy and ionic conductivity testing:

[0149] Electrochemical impedance spectroscopy (EIS) tests apply a small-amplitude alternating current potential wave with varying frequencies to an electrochemical system. The impedance ratio of the alternating current potential to the current signal changes with the frequency of the sinusoidal wave. The tests were performed using the Gamry electrochemical workstation, with a test frequency range of 10 Hz. -2 Hz to 10 5 Between Hz, and with test temperatures between 0℃ and 60℃, EIS curves were obtained at different temperatures, such as... Figure 1 .

[0150] Ionic conductivity was tested in Example 1 using a blocked battery with stainless steel (SS) electrodes. The ionic conductivity (σ) was calculated using the following formula: σ = L / R ь A; where σ(S cm) -1 ) represents the ionic conductivity, L (cm) represents the thickness of the electrolyte between the two electrodes, and A (cm) represents the thickness of the electrolyte between the two electrodes. -2 R represents the effective contact area between the electrolyte and the electrode. b (Ω) represents the bulk resistance, and the conductivity of the quasi-solid polymer electrolyte in Example 1 is 3.06 mS / cm.

[0151] 2. Ion transport number test:

[0152] Chronoamperometry involves applying a single or double potential step to the working electrode of an electrochemical system and measuring the current response as a function of time. This invention combines the Bruce & Vincent method for measuring electrochemical impedance spectroscopy with chronoamperometry to measure the sodium ion transport number (t) of a quasi-solid-state polymer electrolyte. Na+ To calculate the t of the quasi-solid polymer electrolyte. Na+ A Na / quasi-solid-state polymer electrolyte / Na battery was assembled using two sodium metal electrodes (Na) and the quasi-solid-state polymer electrolyte prepared in Example 1. Na+ The value is calculated using the following formula:

[0153] t Na+ =I s *R b s (ΔV-I o *R i o ) / I o *R b 0 (ΔV-I s *R i s )

[0154] Where ΔV(mV) is the applied polarization voltage, I o ,I s (mA) represent the initial current and steady-state current during the polarization process, respectively, R b 0 ,R b s (Ω) represent the bulk resistance at the initial and steady-state conditions, respectively. i o ,R i s (Ω) represent the interface resistance at the initial and steady states, respectively.

[0155] Figure 2 This is Example 1, the DC polarization curve of the Na||Na symmetric cell. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0156] Figure 3 This is a comparative example, showing the DC polarization curves of a Na||Na symmetric cell. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0157] It can be seen that butyl acrylate polymer-based electrolytes have high ion transference numbers while ensuring interfacial compatibility between solid polymer electrolytes and positive and negative electrodes.

[0158] 3. Electrochemical stability window:

[0159] The electrochemical stability window of the quasi-solid-state polymer electrolyte was determined using linear sweep voltammetry. A three-electrode system (Na / quasi-solid-state polymer electrolyte / SS) was used as the working electrode, with Na serving as both the counter and reference electrode. The measurement range was 2.5–8 V (vs. Na). + / Na), scan rate 1mVs -1 Tests were performed on Example 1 and the comparative example respectively, and the test results are as follows. Figure 4As shown, the discharge voltage window of the quasi-solid polymer electrolyte in Example 1 can reach 4.5V. This indicates that the addition of butyl acrylate widens the voltage window of the quasi-solid polymer electrolyte. A higher discharge voltage window is beneficial for improving the energy density of the cell and also implies less polarization.

[0160] 4. Constant current charge and discharge test:

[0161] Batteries assembled using the quasi-solid-state polymer electrolytes of Example 1 and the Comparative Example were subjected to charge-discharge tests in a constant temperature chamber set at 30°C. Five cycles were performed at current densities of 0.1C, 0.2C, 1C, 5C, 10C, 15C, and 20C. For each cycle, the batteries were charged for 2 hours followed by discharging for 2 hours, and this cycle was repeated. The test results are as follows: Figure 5 As shown, the cyclic stability of Example 1 is better than that of the comparative example.

[0162] The long-term cycle stability of the batteries in Example 1 and the comparative example was tested using the Wuhan Landian Battery Testing System (CT3001A / 2001A) at a 5C current density. The charge-discharge tests were conducted in a constant temperature chamber set at 30°C and a constant current density (0.1 mA cm⁻¹). -2 First charge for 2 hours, then discharge for 2 hours, repeat the cycle, and the test results are as follows. Figure 6 As shown. Based on the voltage curve changes during the cycle, it can be determined that the stability and cycle life of the battery in Example 1 of the present invention are significantly better than those of the comparative example.

[0163] Figure 7 The quasi-solid polymer electrolytes of Example 1 and the comparative example are at 0.5 mA cm⁻¹ -2 The long-term cycling performance of the Na||Na symmetric battery structure is shown. It can be seen that the long-term cycling performance of Example 1 is significantly better than that of the comparative example.

[0164] Figure 8 The quasi-solid polymer electrolytes of Examples 2 and 3 are at 0.1 mA cm⁻¹ -2 The long-term cycling performance of the Na||Na symmetric battery structure was observed. It can be seen that polymers obtained using 2,2,3,4,4,4-hexafluorobutyl acrylate monomers and butyl methacrylate monomers both exhibit good long-term cycling performance.

[0165] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A quasi-solid polymer electrolyte, characterized by, The quasi-solid polymer electrolyte comprises: an electrolyte salt, an organic carbonate solvent, and a solid polymer electrolyte matrix; The solid polymer electrolyte matrix is formed by thermal initiation and polymerization curing of polymer monomers and a cross-linking agent under the action of an initiator in the battery, and has a cross-linked network structure; the cross-linked network structure anchors the organic carbonate solvent; The organic carbonate solvent comprises a main solvent and a fluorine-based organic solvent; the organic carbonate solvent is encapsulated in the cross-linked network structure of the solid polymer electrolyte matrix in situ; The quasi-solid polymer electrolyte forms an interface structure in conformal contact with the surface of a metal sodium negative electrode through the thermal initiation and polymerization curing; The electrolyte salt is a sodium salt, and comprises one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and NaBOB; The polymer monomer comprises one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate; The cross-linking agent comprises one or both of polyethylene glycol diacrylate and triethylene glycol diacrylate; The initiator comprises azobisisobutyronitrile; The organic carbonate solvent and the electrolyte salt are complexed together on the surface and / or inside the solid polymer electrolyte matrix; The main solvent comprises at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether; The fluorine-based organic solvent comprises fluoroethylene carbonate.

2. The quasi-solid polymer electrolyte according to claim 1, wherein The mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25; The volume percentage content of the polymer monomer in the organic carbonate solvent is greater than 0 vol. % and less than or equal to 35 vol. %; The volume percentage content of the cross-linking agent in the polymer monomer is greater than 0 vol. % and less than or equal to 5 vol. %; The mass ratio of the initiator to the polymer monomer is 0.1:100-1:

20.

3. The quasi-solid polymer electrolyte according to claim 1, wherein The volume ratio of the main solvent to the fluorine-based organic solvent is 8:1-10:

1.

4. The quasi-solid polymer electrolyte according to claim 1, wherein The voltage window of the quasi-solid polymer electrolyte is 0-4.5 V; The sodium ion transference number of the quasi-solid polymer electrolyte is 0.3-0.

9.

5. A method of producing the quasi-solid polymer electrolyte according to any one of claims 1 to 4, characterized by, The preparation method comprises: The electrolyte salt and the organic carbonate solvent are mixed in proportion and stirred uniformly to form an electrolyte salt solution; the organic carbonate solvent comprises a main solvent and a fluorine-based organic solvent; The polymer monomer, the cross-linking agent, and the initiator are added to the electrolyte salt solution and stirred uniformly to obtain an electrolyte precursor. The electrolyte precursor is injected into a battery, after encapsulation, solidification is carried out at a set temperature, so that the polymer monomer and crosslinking agent form a solid polymer electrolyte matrix with crosslinked network structure under the action of initiator, the organic carbonate solvent is anchored through the crosslinked network structure, so that the organic carbonate solvent is encapsulated in the crosslinked network structure of the solid polymer electrolyte matrix in situ; and the quasi-solid polymer electrolyte is cured by thermal initiation polymerization to form an interface structure in conformal contact with the surface of the metal sodium negative electrode.

6. The production method according to claim 5, characterized by, The electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and NaBOB; The polymer monomer includes one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate; The crosslinking agent includes one or both of polyethylene glycol diacrylate and triethylene glycol diacrylate; The initiator includes azobisisobutyronitrile; The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether; The fluorine-containing organic solvent includes fluoroethylene carbonate; The volume ratio of the main solvent to the fluorine-containing organic solvent is 8:1-10:1; The mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25; The volume percentage content of the polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%; The volume percentage content of the crosslinking agent in the polymer monomer is greater than 0 vol.% and less than or equal to 5 vol.%; The mass ratio of the initiator to the polymer monomer is 0.1:100-1:20; The set temperature is 60°C-80°C.

7. A sodium battery, characterized by, The sodium battery includes the quasi-solid polymer electrolyte of any one of claims 1-4.

8. The sodium battery of claim 7, wherein, The sodium battery further includes a positive electrode and a negative electrode; The positive electrode active material of the positive electrode includes: Na x A1[A2(CN)6] y • zH2O, Na n MO2, NaFePO4, Na2MP2O7, Na3V2(PO4)3, Na2M2(SO4)3, V2O5; the negative electrode is a metal sodium negative electrode; wherein A1 and A2 are at least two of Mn, Fe, Co, Ni, Cu, and Zn, x=1-4, y=1-4, and z=0-10; M is at least one of Co, Fe, Mn, and Ni, and n=1-2.

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