Semi-solid state sodium-ion battery and preparation method therefor

Abstract

A semi-solid state sodium-ion battery and a preparation method therefor. An electrolyte is a gel polymer electrolyte formed by subjecting an electrolytic solution to formation at 50-80°C. On the basis of the total mass of the electrolytic solution being 100 wt%, the electrolytic solution comprises the following components in percentage by weight: 3-20 wt% of a fluorine-containing acrylate monomer; 0.01-0.1 wt% of an initiator; 10-20 wt% of a sodium salt; 2-10 wt% of an additive; and the balance of an organic solvent. The organic solvent is ethylene carbonate and propylene carbonate. The fluorine-containing acrylate monomer is used, which has a high degree of polymerization, reducing the residue of unsaturated double bond monomers in the polymer electrolyte. When the battery undergoes thermal runaway, the fluorine-containing acrylate monomer decomposes to generate fluorine radicals, thereby eliminating hydrogen radicals and hydroxyl radicals from participating in a chain combustion reaction in a gas phase, and improving the flame retardancy of the electrolyte.

Description

A semi-solid sodium-ion battery and its preparation method Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a semi-solid sodium-ion battery and its preparation method. Background Technology

[0002] With the gradual depletion of traditional fossil fuels and increasingly serious environmental problems, the development of new renewable energy sources has become an inevitable trend. Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, and environmental friendliness, have been widely used in electric vehicles, laptops, and energy storage. However, lithium resources are limited and unevenly distributed across the Earth, and will eventually be exhausted. Sodium, on the other hand, is one of the most abundant elements on Earth. Sodium-ion batteries operate on a similar principle to lithium-ion batteries and offer advantages such as low cost, good safety, and long-term large-scale storage, making them increasingly attractive to researchers.

[0003] However, commercially available sodium-ion batteries mostly use organic liquid electrolytes, which pose safety hazards such as short circuits, combustion and explosion, and electrolyte leakage. Semi-solid batteries prepared using in-situ polymerization technology can improve battery safety performance to some extent, but current gel polymer batteries still have problems such as poor thermal stability and flame retardancy of the polymer matrix, resulting in poor thermal stability and safety of the semi-solid sodium-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects or deficiencies of poor thermal stability and flame retardancy in the above-mentioned semi-solid sodium-ion batteries, and to provide a semi-solid sodium-ion battery.

[0005] Another object of the present invention is to provide a method for preparing the semi-solid sodium-ion battery.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A semi-solid sodium-ion battery, wherein the electrolyte of the semi-solid sodium-ion battery is a gel polymer electrolyte formed by electrolysis of an electrolyte solution at 50-80°C; based on a total mass of 100 wt% of the electrolyte solution, the electrolyte solution comprises the following components calculated by weight percentage:

[0008] Fluorinated acrylate monomers 3–20 wt%; initiator 0.01–0.1 wt%; sodium salt 10–20 wt%; additives 2–10 wt%; organic solvent balance;

[0009] The organic solvents are ethylene carbonate and propylene carbonate.

[0010] This invention provides a semi-solid sodium-ion battery. The gel polymer electrolyte uses fluorinated acrylate monomers, which not only have a high degree of polymerization, effectively reducing the residual unsaturated double-bonded monomers in the polymer electrolyte, but also, under thermal runaway conditions, the fluorinated groups decompose to generate fluorine free radicals, eliminating the chain combustion reaction of hydrogen and hydroxyl free radicals in the gas phase, improving the flame retardancy of the electrolyte, and thus enhancing battery safety. Ethylene carbonate and propylene carbonate are selected as solvents. These solvents have high boiling points, further improving the thermal stability of the electrolyte itself. Furthermore, ethylene carbonate participates in the formation of the negative electrode film, further improving SEI stability and reducing side reactions, thereby further enhancing battery safety.

[0011] It should be noted that the fluorinated acrylate monomers described in this invention are 3 to 20 wt%, for example, but not limited to 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, etc., all of which can achieve this invention.

[0012] Further, the fluorinated acrylate monomer is one or more of trifluoroethyl methacrylate (CAS: 352-87-4), octafluoropentyl acrylate (CAS: 376-84-1), dodecafluoroheptyl acrylate (CAS: 2993-85-3), hexafluorobis(2-methyl-2-acrylate) (CAS: 918-36-5), or perfluorooctyl acrylate (CAS: 117374-41-1).

[0013] Furthermore, the fluorinated acrylate monomer is octafluoropentyl acrylate (CAS: 376-84-1) and / or dodecafluoroheptyl acrylate (CAS: 2993-85-3).

[0014] Furthermore, the mass ratio of ethylene carbonate to propylene carbonate is 1:6 to 4:3, for example, but not limited to 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:3 or 4:3, etc., all of which can achieve the present invention.

[0015] Furthermore, the mass ratio of ethylene carbonate to propylene carbonate is 1:6 to 1:1.

[0016] Furthermore, the initiator is an organic peroxide initiator and / or an azo initiator.

[0017] Specifically, the organic peroxide initiator includes one or more of benzoyl peroxide, tert-butyl peroxide, or methyl ethyl ketone peroxide.

[0018] Specifically, the azo initiator includes one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, or azobisisoheptanenitrile.

[0019] The sodium salt described in this invention can be selected from commonly used sodium salts according to existing technology, such as, but not limited to, one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorophosphate, sodium bis(oxalateborate), sodium difluorooxalateborate, sodium difluorosulfonylimide, or sodium bis(trifluoromethylsulfonyl)imide.

[0020] In some preferred embodiments, the sodium salt is sodium hexafluorophosphate and / or sodium difluorosulfonamide.

[0021] The additives described in this invention can be selected from commonly used additives according to existing technology, such as, but not limited to, one or more of the following: vinylene carbonate, fluorovinyl carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, propylene sulfate, methanedisulfonate, tris(trimethylsilane) phosphate, or tris(trimethylsilane) borate.

[0022] In some preferred embodiments, the additive is a mixture of fluoroethylene carbonate, 1,3-propenesulfonate lactone, methylene disulfonate and tris(trimethylsilane) phosphate in a mass ratio of (1-3):1:1:1.

[0023] Furthermore, the electrolyte comprises the following components calculated by weight percentage:

[0024] Fluorinated acrylate monomers 8–15 wt%; initiator 0.03–0.08 wt%; sodium salt 12–18 wt%; additives 3–8 wt%; organic solvent balance.

[0025] Furthermore, the method for preparing the electrolyte includes the following steps:

[0026] Sodium salt, organic solvent and additives are mixed evenly in proportion, and then fluorinated acrylate monomers and initiators are added to obtain electrolyte.

[0027] Furthermore, the formation time is 1 to 5 hours.

[0028] The present invention also provides a method for preparing the above-mentioned semi-solid sodium-ion battery, comprising the following steps: obtaining a bare cell by stacking a positive electrode sheet, a negative electrode sheet and a separator; loading the cell into a packaging film; injecting the prepared electrolyte into the cell and sealing it; allowing it to stand; aging it at 50-80°C for 1-5 hours; and performing capacity testing to obtain a semi-solid sodium-ion battery.

[0029] In some specific embodiments, the settling time is 48 to 96 hours.

[0030] The positive electrode sheet described in this invention can be commercially available or self-made.

[0031] In some specific embodiments, the positive electrode sheet can be prepared by the following method:

[0032] The positive electrode material (e.g., Na4Fe(PO4)2P2O7), binder (e.g., polytetrafluoroethylene), and conductive agent (e.g., carbon black) are dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of (94:3:3) to (98:1:1) (e.g., 96:2:2). The mixture is stirred until stable and uniform, and then uniformly coated onto a carbon-coated aluminum foil with a thickness of 15 μm. The coating is then dried at 120°C for 1 hour, followed by cold pressing and die cutting.

[0033] The negative electrode sheet described in this invention can be commercially available or self-made.

[0034] A negative electrode material (e.g., hard carbon), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and conductive agent (SP) are mixed together in a mass ratio of (93:2:3:2) to (98:0.5:1:0.5) (e.g., 96:1:2:1), dispersed in deionized water, and stirred using a vacuum mixer until stable and homogeneous to form a negative electrode slurry. The negative electrode slurry is then uniformly coated onto an aluminum foil with a thickness of 12 μm. After drying the aluminum foil at room temperature, it is transferred to a 120°C forced-air oven for 1 hour of drying, followed by cold pressing and die-cutting.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention provides a semi-solid sodium-ion battery, comprising a gel polymer electrolyte obtained by polymerization of an electrolyte. The gel polymer electrolyte uses fluorinated acrylate monomers, which not only have a high degree of polymerization, effectively reducing the residual unsaturated double bond monomers in the polymer electrolyte, but also, under thermal runaway, the fluorinated groups decompose to generate fluorine free radicals, eliminating the chain combustion reaction of hydrogen and hydroxyl free radicals in the gas phase, improving the flame retardancy of the electrolyte, thereby improving battery safety. The resulting semi-solid sodium-ion battery has a thermal runaway temperature of not less than 200°C and will not catch fire; after 500 cycles at 85°C, the capacity retention rate is not less than 85%; after 60 days of storage at 85°C, the capacity retention rate and capacity recovery rate are both not less than 65%, with low gas production and cell thickness expansion of less than 10%. Attached Figure Description

[0037] Figure 1 shows the 85°C cycling curves for Example 1 and Comparative Example 3. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0039] The positive electrode sheets used in the examples and comparative examples were prepared by the following method:

[0040] The cathode material Na4Fe(PO4)2P2O7 (NFPP), binder (PVDF), and conductive agent (SP) were dispersed in NMP organic solvent at a mass ratio of 96:2:2. The mixture was stirred under vacuum until stable and homogeneous, and then uniformly coated onto a 15μm thick carbon-coated aluminum foil. After drying the aluminum foil at room temperature, it was transferred to a 120℃ forced-air oven for 1 hour of drying. Then, it was cold-pressed and die-cut to form the cathode sheet.

[0041] The negative electrode sheets used in the examples and comparative examples were prepared by the following method:

[0042] Hard carbon, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and conductive agent (SP) were mixed together in a mass ratio of 96:1:2:1 and dispersed in deionized water. The mixture was stirred in a vacuum mixer until stable and homogeneous, forming a negative electrode slurry. The negative electrode slurry was then uniformly coated onto an aluminum foil with a thickness of 12 μm. After the aluminum foil was dried at room temperature, it was transferred to a 120°C forced-air oven for 1 hour of drying. Finally, it was cold-pressed and die-cut to form a negative electrode sheet.

[0043] Example 1

[0044] A semi-solid sodium-ion battery is prepared by the following method:

[0045] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0046] The electrolyte comprises the following components in parts by weight:

[0047] Octafluoroamyl acrylate is 10 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 17.49 wt%; propylene carbonate is 52.46 wt%; additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0048] Example 2

[0049] A semi-solid sodium-ion battery is prepared by the following method:

[0050] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0051] The electrolyte comprises the following components in parts by weight:

[0052] Dodecafluoroheptyl acrylate 10 wt%; benzoyl peroxide 0.05 wt%; sodium hexafluorophosphate (NaPF6) 10 wt%; sodium difluorosulfonyl imide (NaFSI) 5 wt%; ethylene carbonate 17.49 wt%; propylene carbonate 52.46 wt%; additives 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0053] Example 3

[0054] A semi-solid sodium-ion battery is prepared by the following method:

[0055] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0056] The electrolyte comprises the following components in parts by weight:

[0057] Perfluorooctyl acrylate is 10 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 17.49 wt%; propylene carbonate is 52.46 wt%; and additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene ester and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0058] Example 4

[0059] A semi-solid sodium-ion battery is prepared by the following method:

[0060] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0061] The electrolyte comprises the following components in parts by weight:

[0062] Octafluoroamyl acrylate is 10 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 39.97 wt%; propylene carbonate is 29.98 wt%; additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0063] Example 5

[0064] A semi-solid sodium-ion battery is prepared by the following method:

[0065] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0066] The electrolyte comprises the following components in parts by weight:

[0067] Octafluoroamyl acrylate is 10 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 9.99 wt%; propylene carbonate is 59.96 wt%; additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0068] Example 6

[0069] A semi-solid sodium-ion battery is prepared by the following method:

[0070] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0071] The electrolyte comprises the following components in parts by weight:

[0072] Octafluoroamyl acrylate is 5 wt%; benzoyl peroxide is 0.1 wt%; NaPF6 is 20 wt%; ethylene carbonate is 16.73 wt%; propylene carbonate is 50.17 wt%; and additives are 8 wt% (ethylene carbonate, 1,3-propenesulfonyl lactone, vinyl sulfate, and tris(trimethylsilane) phosphate in a mass ratio of 3:3:1:1).

[0073] Example 7

[0074] A semi-solid sodium-ion battery is prepared by the following method:

[0075] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0076] The electrolyte comprises the following components in parts by weight:

[0077] Octafluoroamyl acrylate is 20 wt%; benzoyl peroxide is 0.01 wt%; NaFSI is 10 wt%; ethylene carbonate is 15.50 wt%; propylene carbonate is 46.49 wt%; and additives are 5 wt% (ethylene carbonate, 1,3-propenesulfonyl lactone, vinyl sulfate and tris(trimethylsilane) phosphate in a mass ratio of 1:1:3:3).

[0078] Comparative Example 1

[0079] A semi-solid sodium-ion battery is prepared by the following method:

[0080] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0081] The electrolyte comprises the following components in parts by weight:

[0082] Octafluoroamyl acrylate 10 wt%; benzoyl peroxide 0.05 wt%; sodium hexafluorophosphate (NaPF6) 10 wt%; sodium difluorosulfonyl imide (NaFSI) 5 wt%; ethylene carbonate 17.49 wt%; methyl ethyl carbonate 52.46 wt%; additives 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1)

[0083] Comparative Example 2

[0084] A semi-solid sodium-ion battery is prepared by the following method:

[0085] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0086] The electrolyte comprises the following components in parts by weight:

[0087] Octafluoroamyl acrylate is 10 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 20.99 wt%; propylene carbonate is 13.99 wt%; methyl ethyl carbonate is 34.97 wt%; and additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0088] Comparative Example 3

[0089] A semi-solid sodium-ion battery is prepared by the following method:

[0090] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0091] The electrolyte comprises the following components in parts by weight:

[0092] Octafluoroamyl acrylate is 1 wt%; benzoyl peroxide is 0.05 wt%; sodium hexafluorophosphate (NaPF6) is 10 wt%; sodium difluorosulfonyl imide (NaFSI) is 5 wt%; ethylene carbonate is 19.74 wt%; propylene carbonate is 59.21 wt%; additives are 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0093] Comparative Example 4

[0094] A semi-solid sodium-ion battery is prepared by the following method:

[0095] The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in an aluminum-plastic film. The prepared electrolyte is injected into the cell and sealed. The cell is then left to stand at room temperature for 72 hours and then formed at 70°C for 4 hours (during the formation process, the electrolyte will undergo thermal polymerization to form a gel polymer electrolyte). After the formation is completed, the battery is aged and capacity tested to obtain a semi-solid sodium-ion battery.

[0096] The electrolyte comprises the following components in parts by weight:

[0097] Octafluoroamyl acrylate 30 wt%; benzoyl peroxide 0.05 wt%; sodium hexafluorophosphate (NaPF6) 10 wt%; sodium difluorosulfonyl imide (NaFSI) 5 wt%; ethylene carbonate 12.49 wt%; propylene carbonate 37.46 wt%; additives 5 wt% (fluoroethylene carbonate, 1,3-propenesulfonyl lactone, methanedisulfonate methylene and tris(trimethylsilane) phosphate in a mass ratio of 2:1:1:1).

[0098] Performance testing

[0099] 1. Testing Method

[0100] (1) Battery safety performance test: The sodium-ion cells prepared in the above examples and comparative examples were charged to 3.65V at 25°C at 1C, and then charged to the cutoff current of 0.02C at a constant voltage of 3.65V. The fully charged cells were then placed on a hot plate and heated continuously to monitor the thermal runaway temperature of the cells and observe the runaway situation of the cells.

[0101] (2) 85℃ Cyclic Test: The sodium-ion cells prepared in the above examples and comparative examples were fully charged and then placed in an environment of (85±3)℃ for 3 hours. When the cell body reached (85±3)℃, the cell was charged to 3.65V at a constant current of 1C, then charged to a cutoff current of 0.05C at a constant voltage of 3.65V, and then discharged to 1.5V at 1C. The initial capacity Q0 was recorded. This cycle was repeated until 500 cycles were completed, at which point the capacity Q1 was recorded. The capacity retention rate (%) was calculated, and the results are shown in Table 1. The calculation formulas used are as follows:

[0102] Capacity retention rate (%) = Q1 / Q0 × 100%.

[0103] (3) 85℃ High-Temperature Storage Experiment: The sodium-ion cells prepared in the above examples and comparative examples were charged at 25℃ to 3.65V using a 1C method, then charged at a constant voltage of 3.65V to a cutoff current of 0.02C, and then discharged at a constant current of 1C to 1.5V, which was recorded as the initial capacity Q2. The cells were then charged again to 3.65V using a 1C method, and then charged at a constant voltage of 3.65V to a cutoff current of 0.02C. The thickness D0 of the fully charged cell was measured. The fully charged battery was then placed at 85℃. After being left in the environment for 60 days, the thickness D1 of the fully charged cell was tested. It was then discharged at a constant current of 1C to 1.5V, and this was recorded as the retention capacity Q3. At 25℃, the battery was charged at 1C to 3.65V, then charged at a constant voltage of 3.65V to the cutoff current of 0.02C, and finally discharged at a constant current of 1C to 1.5V, which was recorded as the recovery capacity Q4. The cell capacity retention rate (%), capacity recovery rate (%), and thickness change rate (%) were calculated, and the results are shown in Table 1. The calculation formulas used are as follows:

[0104] Capacity retention rate (%) = Q3 / Q2 × 100%; Capacity recovery rate (%) = Q4 / Q2 × 100%; Thickness change rate (%) = (D1-D0) / D0 × 100%.

[0105] 2. Test Results

[0106] The test results of each embodiment and comparative example are shown in Table 1 and Figure 1.

[0107] Table 1. Experimental data for each embodiment and comparative example.

[0108] As can be seen from Table 1 and Figure 1, the semi-solid sodium-ion battery provided by the present invention has good safety performance and high-temperature stability. Specifically, the thermal runaway temperature is not lower than 200°C and no fire will occur; after 500 cycles at 85°C, the retention rate is not lower than 85%; after 60 days of storage at 85°C, the capacity retention rate and capacity recovery rate are both not lower than 65%, the gas production is relatively low, and the cell thickness expansion is less than 10%.

[0109] As can be seen from Comparative Examples 1 and 2, the semi-solid-state batteries prepared by using other organic solvents instead of the organic solvents in this invention do not have a thermal runaway temperature exceeding 200°C, and their performance in cycling and storage at 85°C is worse than that of the organic solvents in this invention. This may be because methyl ethyl carbonate has a low boiling point and is easily volatilized at high temperatures, resulting in poor thermal stability of the electrolyte and thus poor battery performance at high temperatures.

[0110] Comparative Examples 3 and 4 show that when too little fluorinated acrylate monomer is used, it cannot achieve the flame retardant effect, and the battery experiences thermal runaway at 170°C, accompanied by fire. When too much fluorinated acrylate monomer is used, the electrolyte viscosity is relatively high, and the thermal stability of the electrolyte is reduced, resulting in poor high-temperature performance.

[0111] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A semi-solid sodium-ion battery, characterized in that, The electrolyte of the semi-solid sodium-ion battery is a gel polymer electrolyte formed by electrolysis of an electrolyte solution at 50–80°C; based on a total mass of 100 wt%, the electrolyte solution contains the following components calculated by weight percentage: Fluorinated acrylate monomers 3–20 wt%; initiator 0.01–0.1 wt%; sodium salt 10–20 wt%; additives 2–10 wt%; organic solvent balance; The organic solvents are ethylene carbonate and propylene carbonate.

2. The semi-solid sodium-ion battery according to claim 1, characterized in that, The fluorinated acrylate monomers are one or more of trifluoroethyl methacrylate, octafluoropentyl acrylate, dodecafluoroheptyl acrylate, hexafluorobis(2-methyl-2-acrylate) or perfluorooctyl acrylate.

3. The semi-solid sodium-ion battery according to claim 1, characterized in that, The mass ratio of ethylene carbonate to propylene carbonate is 1:6 to 4:

3.

4. The semi-solid sodium-ion battery according to claim 1, characterized in that, The fluorinated acrylate monomers are octafluoropentyl acrylate and / or dodecafluoroheptyl acrylate.

5. The semi-solid sodium-ion battery according to claim 1, characterized in that, The initiator is an organic peroxide initiator.

6. The semi-solid sodium-ion battery according to claim 1, characterized in that, The sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorophosphate, sodium bis(oxalate-borate), sodium di(oxalate-borate), sodium difluorosulfonylimide, or sodium bis(trifluoromethylsulfonyl)imide.

7. The semi-solid sodium-ion battery according to claim 1, characterized in that, The additives include one or more of the following: vinylene carbonate, fluorovinyl carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, propylene sulfate, methanedisulfonate, tris(trimethylsilane) phosphate, or tris(trimethylsilane) borate.

8. The semi-solid sodium-ion battery according to claim 1, characterized in that, The preparation method of the electrolyte includes the following steps: Sodium salt, organic solvent and additives are mixed evenly in proportion, and then fluorinated acrylate monomers and initiators are added to obtain electrolyte.

9. The semi-solid sodium-ion battery according to claim 1, characterized in that, The formation time is 1 to 5 hours.

10. A method for preparing a semi-solid sodium-ion battery according to any one of claims 1 to 9, characterized in that, Includes the following steps: The positive electrode, negative electrode and separator are stacked to obtain a bare cell. The cell is then placed in a packaging film, the prepared electrolyte is injected into the cell, and the cell is sealed and left to stand. After being conditioned at 50-80℃ for 1-5 hours, it is aged and capacity tested to obtain a semi-solid sodium-ion battery.

Images