Quasi-solid polymer electrolyte, preparation method therefor and use thereof

Abstract

A quasi-solid polymer electrolyte, a preparation method therefor, and the use thereof. The quasi-solid polymer electrolyte comprises an electrolyte salt, an organic carbonate ester solvent, and a solid polymer electrolyte matrix, wherein the solid polymer electrolyte matrix is formed into a cross-linked network structure by polymerizing a polymer monomer and a cross-linking agent under the action of an initiator, the organic carbonate ester solvent comprises a main solvent and a fluorine-containing organic solvent, and the organic carbonate ester solvent is encapsulated in situ in the cross-linked network structure of the solid polymer electrolyte matrix.

Description

A quasi-solid polymer electrolyte, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202410929855.6, filed on July 11, 2024, entitled "A Quasi-Solid Polymer Electrolyte and Its Preparation Method and Application". Technical Field

[0002] This invention relates to the field of solid-state sodium metal battery technology, and in particular to a quasi-solid polymer electrolyte, its preparation method, and its application. Background Technology

[0003] Energy storage and conversion technologies play a crucial role in the energy transition under a dual-carbon context (i.e., "carbon peaking" and "carbon neutrality"), with applications including electronics, electric vehicles, and renewable energy storage. Currently, lithium-ion batteries dominate the rechargeable battery market. However, the limited and uneven distribution of lithium ore reserves in the Earth's crust makes gigawatt-scale applications of lithium-ion batteries (such as grid-connected stationary energy storage) economically infeasible. From a physicochemical perspective, sodium and lithium belong to the same Group 1 elements and have similar properties. From an industrial demand perspective, metallic sodium is abundant, extraction technology is simple, and production costs are low. Therefore, sodium metal batteries, using metallic sodium as the negative electrode, are very promising as a low-cost alternative to lithium metal batteries. Sodium metal possesses a low electrochemical potential (-2.714V (relative to the standard hydrogen electrode)) and a high theoretical specific energy (1,165 mAh g⁻¹). -1 Using sodium metal as the negative electrode can further improve the overall capacity of the battery.

[0004] However, due to the high reactivity of sodium metal, problems such as severe dendrite growth in sodium metal anodes, the formation of a thick and fragile solid electrolyte interphase (SEI) layer from the reaction of the electrolyte with metallic sodium, and uncontrollable volume changes lead to the rapid failure of sodium metal anodes. Furthermore, the use of highly reactive sodium metal and the formation of sodium dendrites during battery operation raise safety concerns, especially when using highly flammable liquid electrolytes.

[0005] Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a quasi-solid polymer electrolyte, its preparation method, and its applications. The cross-linked network of the polymer in the quasi-solid polymer electrolyte can anchor highly reactive solvents, preventing their continuous reduction and decomposition on the metal anode surface to form a thick and uneven SEI layer, which is beneficial for improving Na+ performance. + The reversibility of deposition / stripping delays the rapid depletion of sodium ions at the negative electrode interface, restricts the development of sodium deposition morphology towards dendritic morphology, and thus achieves the stability of sodium metal in long-term cycling.

[0007] To achieve the above objectives, the present invention provides a quasi-solid polymer electrolyte, comprising: an electrolyte salt, an organic carbonate solvent, and a solid polymer electrolyte matrix;

[0008] The solid polymer electrolyte matrix is ​​formed by polymerizing polymer monomers and crosslinking agents under the action of an initiator, and has a crosslinked network structure.

[0009] The organic carbonate solvent includes a main solvent and a fluorinated organic solvent; the organic carbonate solvent is encapsulated in situ within the cross-linked network structure of the solid polymer electrolyte matrix.

[0010] Preferably, the electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB).

[0011] The polymer monomers include one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate;

[0012] The crosslinking agent includes one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate, and ethylene glycol methyl ether acetate;

[0013] The initiator includes azobisisobutyronitrile.

[0014] Preferably, the organic carbonate solvent and the electrolyte salt are co-complexed on the surface and / or inside the solid polymer electrolyte matrix.

[0015] Preferably, the mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25;

[0016] The volume percentage of the polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%.

[0017] The crosslinking agent has a volume percentage content of greater than 0 vol.% and less than or equal to 5 vol.% in the polymer monomer;

[0018] The mass ratio of the initiator to the polymer monomer is 0.1:100-1:20.

[0019] Preferably, the main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether;

[0020] The fluorinated organic solvent includes: fluoroethylene carbonate;

[0021] The volume ratio of the main solvent to the fluorinated organic solvent is 8:1 to 10:1.

[0022] Preferably, the voltage window of the quasi-solid polymer-based electrolyte is 0-4.5V;

[0023] The sodium ion transference number of the quasi-solid polymer electrolyte is 0.3-0.9.

[0024] In a second aspect, embodiments of the present invention provide a method for preparing the quasi-solid polymer electrolyte described in the first aspect above, characterized in that the preparation method includes:

[0025] An electrolyte salt and an organic carbonate solvent are mixed in a certain proportion and stirred evenly to form an electrolyte salt solution; wherein, the organic carbonate solvent includes a main solvent and a fluorine-containing organic solvent.

[0026] Polymer monomers and crosslinking agents are added to the electrolyte salt solution and stirred until homogeneous. Then, an initiator is added and stirred until homogeneous to obtain an electrolyte precursor.

[0027] The electrolyte precursor is injected into the battery, encapsulated, and then cured at a set temperature.

[0028] Preferably, the electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB).

[0029] The polymer monomers include one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate;

[0030] The crosslinking agent includes one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate, and ethylene glycol methyl ether acetate;

[0031] The initiator includes azobisisobutyronitrile;

[0032] The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether.

[0033] The fluorinated organic solvent includes: fluoroethylene carbonate;

[0034] The volume ratio of the main solvent to the fluorinated organic solvent is 8:1-10:1;

[0035] The mass ratio of the electrolyte salt to the organic carbonate solvent is 13:100-4:25;

[0036] The volume percentage of the polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%.

[0037] The crosslinking agent has a volume percentage content of greater than 0 vol.% and less than or equal to 5 vol.% in the polymer monomer;

[0038] The mass ratio of the initiator to the polymer monomer is 0.1:100-1:20;

[0039] The set temperature is 60℃-80℃.

[0040] Thirdly, embodiments of the present invention provide a sodium battery comprising the quasi-solid polymer electrolyte described in the first aspect above.

[0041] Preferably, the sodium battery further includes a positive electrode and a negative electrode;

[0042] The positive electrode active material 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 the negative electrode is a metallic sodium negative electrode;

[0043] Wherein, A1 and A2 are at least two of Mn, Fe, Co, Ni, Cu, and Zn, x = 1 to 4, y = 1 to 4, z = 0 to 10; M is at least one of Co, Fe, Mn, and Ni, n = 1 to 2.

[0044] The quasi-solid polymer electrolyte provided in this invention has the ability to anchor highly reactive solvents through the polymer cross-linking network, preventing them from continuously reducing and decomposing on the metal anode surface to form a thick and uneven SEI layer. This is beneficial for improving the performance of Na+. +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. Therefore, the quasi-solid polymer electrolyte proposed in this invention has high interfacial compatibility, can suppress the increase in impedance during long-term cell cycling, and can improve 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. Attached Figure Description

[0045] Figure 1 shows the electrochemical impedance spectroscopy (EIS) curves of the quasi-solid polymer electrolyte of the present invention at different temperatures;

[0046] Figure 2 shows the DC polarization curves of the Na||Na symmetric cell in Example 1. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0047] Figure 3 shows the DC polarization curves of the Na||Na symmetric cell of the comparative example. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0048] Figure 4 shows the voltammetric curves of the electrochemical oxidation stability of Example 1 and the comparative example tested by linear cyclic voltammetry.

[0049] Figure 5 shows the rate performance test results of Example 1 and the comparative example using a fresh Na metal anode.

[0050] Figure 6 shows the long-term cycling stability test of Example 1 and the comparative example using a fresh Na metal anode at a current density of 5C.

[0051] Figure 7 shows the results of Example 1 and the comparative example, with Na metal at 0.5 mA cm⁻¹. -2 Long-term cycling performance of Na||Na symmetric battery structure;

[0052] Figure 8 shows examples 2 and 3, where Na metal was used at 0.1 mA cm⁻¹. -2 The long-term cycling performance of the Na||Na symmetric battery structure. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0055] This invention provides a quasi-solid polymer electrolyte, which comprises: an electrolyte salt, an organic carbonate solvent, and a solid polymer electrolyte matrix;

[0056] Among them, the solid polymer electrolyte matrix is ​​formed by the polymerization of polymer monomers and crosslinking agents under the action of an initiator, and has a crosslinked network structure;

[0057] The organic carbonate solvent and the electrolyte salt are co-complexed on the surface and / or inside the solid polymer electrolyte matrix.

[0058] By using complexed electrolyte salts, the ions required for conductivity of the quasi-solid polymer electrolyte are provided, further improving the ionic conductivity of the quasi-solid polymer electrolyte and reducing the battery interface resistance.

[0059] The organic carbonate solvent includes a main solvent and a fluorinated organic solvent; the organic carbonate solvent is in situ encapsulated in the cross-linked network structure of the solid polymer electrolyte matrix. This invention, by adding a fluorinated organic solvent, such as fluoroethylene carbonate, can effectively improve the battery's interfacial compatibility, rate capability, coulombic efficiency, and cycle charge-discharge performance.

[0060] The aforementioned quasi-solid polymer electrolyte can be prepared using the method shown in the following steps. The specific selection of various substances used is explained in the preparation method.

[0061] The method for preparing the quasi-solid polymer electrolyte proposed in this invention includes:

[0062] Step 110: Mix the electrolyte salt and organic carbonate solvent in a certain proportion and stir evenly to form an electrolyte salt solution;

[0063] The mass ratio of electrolyte salt to organic carbonate solvent is 13:100-4:25.

[0064] The electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB).

[0065] The organic carbonate solvent includes a main solvent and a fluorinated organic solvent; the volume ratio of the main solvent to the fluorinated 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 fluorinated organic solvent includes fluoroethylene carbonate.

[0066] Step 120: Add polymer monomers and crosslinking agents to the electrolyte salt solution and stir until homogeneous, then add initiator and stir until homogeneous to obtain electrolyte precursor;

[0067] The volume percentage 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 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.

[0068] The polymer monomers include one or more of butyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, and butyl methacrylate; the crosslinking agents include one or more of polyethylene glycol diacrylate, triethylene glycol diacrylate, and ethylene glycol methyl ether acetate; and the initiator includes azobisisobutyronitrile.

[0069] Step 130: Inject the electrolyte precursor into the battery, encapsulate it, and then cure it at a set temperature.

[0070] Specifically, the electrolyte precursor is directly injected into the battery to effectively wet the electrodes and separator. After the battery is encapsulated, polymerization is initiated by heating. The set temperature is a temperature sufficient to initiate polymerization, preferably 60°C-80°C. The curing time is preferably 2 hours.

[0071] The pre-electrolyte precursor, which has good flowability before thermally initiated polymerization and curing, can achieve good contact with the electrode. After the electrolyte is cured, conformal interfacial contact is achieved, which can ensure uniform ion transport between the electrode and the electrolyte.

[0072] In this invention, the quasi-solid polymer electrolyte matrix polymerized from the aforementioned polymer monomers possesses high mechanical strength, thus effectively suppressing sodium dendrites from piercing the electrolyte. In the quasi-solid polymer electrolyte, the solid polymer electrolyte matrix acts as a framework, providing active sites for the electrolyte salt, thereby ensuring both mechanical strength and ion transference number.

[0073] The quasi-solid polymer electrolyte of the present invention can improve the problems of low ionic conductivity and poor interfacial compatibility of solid polymer electrolytes. At the same time, the quasi-solid polymer electrolyte can also have good processability and electrochemical performance. More importantly, since energy storage power stations have a wide operating temperature range, batteries assembled with the quasi-solid polymer electrolyte of the present invention can be more safely applied to a wider temperature range than batteries assembled with electrolytes.

[0074] The quasi-solid polymer electrolyte proposed in this invention can be applied in sodium batteries, such as sodium metal batteries. Sodium metal batteries also include a positive electrode and a negative electrode. The positive electrode active material includes: Na... x A1[A2(CN)6] y ·zH2O、Na n The anode material is 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 cathode is a metallic sodium cathode.

[0075] 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 SEI 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, so that the electrolyte can fit and cover the electrode and adapt to the surface morphology and microstructure of the electrode, effectively improving interfacial compatibility, suppressing the increase of impedance during long-term cell cycling, improving the voltage window and ion transport number of the battery, thereby improving the service life and safety performance of batteries assembled with quasi-solid polymer electrolytes (such as sodium metal batteries) in energy storage power stations.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] Example 1

[0080] 1) Preparation of electrolyte precursors:

[0081] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0082] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide (NaFSI) and stir at room temperature for 1 hour to prepare a sodium bis(fluorosulfonyl)imide salt solution with a concentration of 1 mol / L;

[0083] 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;

[0084] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0085] 2) Preparation of the positive electrode:

[0086] 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.

[0087] 3) Preparation of negative electrode sheet:

[0088] 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.

[0089] 4) Assemble sodium metal batteries:

[0090] 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.

[0091] Example 2

[0092] 1) Preparation of electrolyte precursors:

[0093] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0094] 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;

[0095] 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;

[0096] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0097] 2) Preparation of the positive electrode:

[0098] 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.

[0099] 3) Preparation of negative electrode sheet:

[0100] 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.

[0101] 4) Assemble sodium metal batteries:

[0102] 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.

[0103] Example 3

[0104] 1) Preparation of electrolyte precursors:

[0105] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0106] 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;

[0107] 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;

[0108] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0109] 2) Preparation of the positive electrode:

[0110] 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.

[0111] 3) Preparation of negative electrode sheet:

[0112] 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.

[0113] 4) Assemble sodium metal batteries:

[0114] 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.

[0115] Example 4

[0116] 1) Preparation of electrolyte precursors:

[0117] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0118] ② Add 91.2 mg of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and stir at room temperature for 1 hour to prepare a sodium bis(trifluoromethanesulfonyl)imide salt solution with a concentration of 1 mol / L;

[0119] 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;

[0120] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0121] 2) Preparation of the positive electrode:

[0122] 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.

[0123] 3) Preparation of negative electrode sheet:

[0124] 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.

[0125] 4) Assemble sodium metal batteries:

[0126] 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.

[0127] Example 5

[0128] 1) Preparation of electrolyte precursors:

[0129] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0130] 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;

[0131] 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;

[0132] ④ Add 3 mg of azobisisobutyronitrile and stir for 10 min to obtain the electrolyte precursor.

[0133] 2) Preparation of the positive electrode:

[0134] 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.

[0135] 3) Preparation of negative electrode sheet:

[0136] 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.

[0137] 4) Assemble sodium metal batteries:

[0138] 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.

[0139] Comparative example

[0140] 1) Preparation of electrolytes:

[0141] ① At room temperature, 300 μL of propylene carbonate and fluoroethylene carbonate were mixed at a volume ratio of 9:1.

[0142] ② Add 60.9 mg of sodium bis(fluorosulfonyl)imide and stir at room temperature for 1 hour to prepare a 1 mol / L sodium bis(fluorosulfonyl)imide salt solution as an electrolyte precursor.

[0143] 2) Preparation of the positive electrode:

[0144] 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.

[0145] 3) Preparation of negative electrode sheet:

[0146] 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.

[0147] 4) Assemble sodium metal batteries:

[0148] 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.

[0149] The above embodiments and comparative examples were tested and analyzed.

[0150] 1. Electrochemical impedance spectroscopy and ionic conductivity testing:

[0151] 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 The test temperature ranged from 0℃ to 60℃, and the EIS curves at different temperatures were obtained, as shown in Figure 1.

[0152] Ionic conductivity was tested in Example 1 using a blocked battery with stainless steel (SS) electrodes at both ends. 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.

[0153] 2. Ion transport number test:

[0154] 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:

[0155] t Na+ =I s *R b s (ΔV-I o *R i o ) / I o *R b 0(ΔV-I s *R i s );

[0156] 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.

[0157] Figure 2 shows the DC polarization curves of the Na||Na symmetric cell in Example 1. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0158] Figure 3 shows the DC polarization curves of a comparative example, the Na||Na symmetric cell. The blue and purple-red curves in the figure correspond to the EIS curves before and after polarization, respectively.

[0159] 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.

[0160] 3. Electrochemical stability window:

[0161] 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 conducted on Example 1 and the comparative example, and the results are shown in Figure 4. It can be seen that 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.

[0162] 4. Constant current charge and discharge test:

[0163] The 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. They were cycled for 5 cycles each at current densities of 0.1C, 0.2C, 1C, 5C, 10C, 15C, and 20C. For each cycle, the batteries were charged for 2 hours and then discharged for 2 hours, and the cycle was repeated. The test results are shown in Figure 5. It can be seen that the cycle stability of Example 1 is better than that of the Comparative Example.

[0164] 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 The battery was first charged for 2 hours, then discharged for 2 hours, and this cycle was repeated. The test results are shown in Figure 6. 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 this invention are significantly better than those of the comparative example.

[0165] Figure 7 shows the quasi-solid polymer electrolytes of Example 1 and the comparative example 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.

[0166] Figure 8 shows the quasi-solid polymer electrolytes of Examples 2 and 3 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.

[0167] 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 in that, 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 polymerizing polymer monomers and crosslinking agents under the action of an initiator, and has a crosslinked network structure. The organic carbonate solvent includes a main solvent and a fluorinated organic solvent; the organic carbonate solvent is encapsulated in situ within the cross-linked network structure of the solid polymer electrolyte matrix.

2. The quasi-solid polymer electrolyte according to claim 1, characterized in that, The electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB). The polymer monomers include 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; The initiator includes azobisisobutyronitrile.

3. The quasi-solid polymer electrolyte according to claim 1, characterized in that, The organic carbonate solvent and the electrolyte salt are complexed together on the surface and / or inside the solid polymer electrolyte matrix.

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

20.

5. The quasi-solid polymer electrolyte according to claim 1, characterized in that, The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether. The fluorinated organic solvent includes: fluoroethylene carbonate; The volume ratio of the main solvent to the fluorinated organic solvent is 8:1 to 10:

1.

6. The quasi-solid polymer electrolyte according to claim 1, characterized in that, The voltage window of the quasi-solid polymer-based electrolyte is 0-4.5V; The sodium ion transference number of the quasi-solid polymer electrolyte is 0.3-0.

9.

7. A method for preparing the quasi-solid polymer electrolyte according to any one of claims 1-6, characterized in that, The preparation method includes: An electrolyte salt and an organic carbonate solvent are mixed in a certain proportion and stirred evenly to form an electrolyte salt solution; wherein, the organic carbonate solvent includes a main solvent and a fluorine-containing organic solvent. Polymer monomers and crosslinking agents are added to the electrolyte salt solution and stirred until homogeneous. Then, an initiator is added and stirred until homogeneous to obtain an electrolyte precursor. The electrolyte precursor is injected into the battery, encapsulated, and then cured at a set temperature.

8. The preparation method according to claim 7, characterized in that, The electrolyte salt is a sodium salt, including one or more of NaPF6, NaClO4, NaFSI, NaTFSI, and sodium bis(oxalate)borate (NaBOB). The polymer monomers include 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; The initiator includes azobisisobutyronitrile; The main solvent includes at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, and diethylene glycol dimethyl ether. The fluorinated organic solvent includes: fluoroethylene carbonate; The volume ratio of the main solvent to the fluorinated 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 of the polymer monomer in the organic carbonate solvent is greater than 0 vol.% and less than or equal to 35 vol.%. The crosslinking agent has a volume percentage content of greater than 0 vol.% and less than or equal to 5 vol.% in the polymer monomer; The mass ratio of the initiator to the polymer monomer is 0.1:100-1:20; The set temperature is 60℃-80℃.

9. A sodium battery, characterized in that, The sodium battery comprises the quasi-solid polymer electrolyte as described in any one of claims 1-6.

10. The sodium battery according to claim 9, characterized in that, The sodium battery further includes: a positive electrode and a negative electrode; The positive electrode active material 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 the negative electrode is a metallic sodium negative electrode; Wherein, A1 and A2 are at least two of Mn, Fe, Co, Ni, Cu, and Zn, x = 1 to 4, y = 1 to 4, z = 0 to 10; M is at least one of Co, Fe, Mn, and Ni, n = 1 to 2.

Images