Flame-retardant electrolyte capable of being solidified in situ and sodium ion secondary battery
By using a flame-retardant electrolyte that can be solidified in situ in sodium-ion batteries, and adding dimethyl vinylphosphonate and an initiator to form a gel electrolyte, the safety and leakage problems of sodium-ion batteries are solved, achieving high efficiency in flame retardancy and long cycle life, making it suitable for large-scale energy storage applications.
Patent Information
- Application Number
- CN202511520394.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-23
- Publication Date
- 2026-02-03
AI Technical Summary
Sodium-ion batteries pose safety risks and the risk of liquid electrolyte leakage, which limits their widespread application.
A flame-retardant electrolyte that can be solidified in situ is used, which contains sodium salt, solvent and initiator. By adding dimethyl vinylphosphonate and initiator, a gel electrolyte is formed by polymerization at high temperature, thus achieving the in-situ solidification of the electrolyte.
Significantly improves the flame retardancy and cycle stability of batteries, avoids leakage risks, enhances battery safety and reliability, broadens the range of material choices, and reduces production costs.
Smart Images
Figure CN121460718A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of battery materials. Specifically, the present application relates to an in-situ solidifiable flame-retardant electrolyte and an in-situ solidifiable sodium-ion secondary battery. BACKGROUND
[0002] In the critical period of energy transformation today, high-performance secondary batteries, as efficient and convenient energy storage and conversion devices, play a crucial role in building a clean energy system and achieving large-scale energy storage. Sodium-ion batteries, with their abundant resources, wide distribution, and low cost, are recognized as a powerful supplement to lithium-ion batteries, especially in the field of large-scale energy storage, showing great application potential and becoming a hot spot for global research teams to compete.
[0003] However, the safety problem of sodium-ion batteries has always been a key bottleneck restricting their development. Currently, sodium-ion batteries mostly use flammable carbonate and / or ether solvent systems as electrolytes. In abnormal conditions such as overcharging, short circuiting, or heating, the battery is prone to fire, combustion, and even explosion, which can cause serious safety accidents. Although the development of flame-retardant electrolytes has alleviated some safety problems to some extent, the inherent risk of liquid electrolyte leakage still exists, which undoubtedly casts a shadow on the widespread application of sodium-ion batteries.
[0004] Therefore, there is an urgent need for a safe, non-leakage-risk, high-performance (such as cycle stability) electrolyte. SUMMARY
[0005] The purpose of the present application is to provide an in-situ solidifiable flame-retardant electrolyte and a sodium-ion secondary battery to solve the safety hazards and liquid electrolyte leakage risks of existing sodium-ion batteries, improve the safety performance and cycle stability of sodium-ion batteries, and make them more suitable for large-scale energy storage and other application scenarios.
[0006] The above-mentioned purpose of the present application is achieved by the following technical solutions.
[0007] In a first aspect, the present application provides an in-situ solidifiable flame-retardant electrolyte, which comprises the following components: a sodium salt, a solvent, and an initiator.
[0008] The solvent comprises a first solvent and a second solvent; wherein the first solvent is selected from at least one of a carbonate solvent, a carboxylate solvent, and an ether solvent; the second solvent is dimethyl vinylphosphonate and / or diethyl vinylphosphonate; and the volume fraction of the second solvent in the solvent is 5%-65%.
[0009] The inventors of the present application unexpectedly found that when dimethyl vinylphosphonate and an initiator are added in the electrolyte, both the safety problem of the electrolyte and the cycle stability of the battery can be improved, and it is also a gelable electrolyte.
[0010] The inventors of the present application also unexpectedly found that the polymerizable dimethyl vinylphosphonate and / or diethyl vinylphosphonate can solidify the electrolyte after high temperature, improve the high-voltage stability of the electrolyte, and the battery made of dimethyl vinylphosphonate and / or diethyl vinylphosphonate with a suitable content can pass the puncture test and realize more than 800 cycles of quasi-solid sodium battery cycle.
[0011] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonate), sodium trifluoromethylsulfonate and sodium perchlorate.
[0012] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the concentration of the sodium salt in the electrolyte is 0.1-2 mol / L.
[0013] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the mass ratio of the second solvent to the initiator is second solvent: initiator = (5-500): 1.
[0014] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the initiator includes at least one of azobis isobutyronitrile (AIBN), di(2,4-dichlorobenzoyl) peroxide (DCBP), diacetyl peroxide, dioctanoyl peroxide, dilauryl peroxide, dicarbonate peroxide, diisopropyl dicarbonate peroxide, diisobutyl dicarbonate peroxide, dicyclohexyl dicarbonate peroxide and di(p-tert-butylcyclohexyl) dicarbonate peroxide.
[0015] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the carbonate solvent is a cyclic carbonate solvent and / or a chain carbonate solvent.
[0016] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the cyclic carbonate is ethylene carbonate and / or propylene carbonate.
[0017] Preferably, in the in-situ solidifiable flame-retardant electrolyte of the present application, the chain carbonate is a carbonate synthesized from a linear or branched aliphatic monohydric alcohol with a carbon number of 3-8 and carbonic acid.
[0018] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate and methyl ethyl carbonate.
[0019] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the ether solvent is selected from one or more of tetrahydrofuran, 2-methyl tetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
[0020] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the carboxylic acid ester solvent is a cyclic carboxylic acid ester solvent and / or a chain carboxylic acid ester solvent.
[0021] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the cyclic carboxylic acid ester is γ-butyrolactone and the chain carboxylic acid ester is a chain carboxylic acid ester having a carbon number of 3-8.
[0022] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the chain carboxylic acid ester is selected from one or more of methyl acetate, ethyl acetate, propyl acetate, propyl propionate and ethyl propionate.
[0023] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the electrolyte further comprises a functional additive.
[0024] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the functional additive is selected from one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, ethylene sulfate, dimethyl sulfite, diethyl sulfite and succinonitrile.
[0025] Preferably, in the in-situ solidifiable flame-retardant electrolyte according to the present application, the mass fraction of the functional additive in the electrolyte is 0.5-10%.
[0026] The in-situ solidifiable flame-retardant electrolyte according to the present application can be solidified in-situ by a method comprising the following steps:
[0027] (1) under the protection of an inert atmosphere, dissolving a sodium salt, a solvent and a functional additive by stirring to obtain a uniform mixture;
[0028] (2) adding dimethyl vinylphosphonate and an initiator to the mixture obtained in step (1) and mixing uniformly to obtain an electrolyte;
[0029] (3) injecting the electrolyte into a battery shell and sealing;
[0030] (4) heating the battery after injecting the electrolyte at 60-80°C for 1-10 hours to initiate the polymerization of dimethyl vinylphosphonate and form a gel electrolyte, thereby realizing the in-situ solidification of the electrolyte.
[0031] In a second aspect, the present application provides an in-situ solidifiable sodium-ion secondary battery, which comprises a positive electrode material, a negative electrode material, and the in-situ solidifiable flame-retardant electrolyte of the present application.
[0032] Preferably, in the in-situ solidifiable sodium-ion secondary battery of the present application, the positive electrode material is a layered metal oxide, a polyanion-based positive electrode material, or a Prussian blue-based material, and the negative electrode material is a carbon-based material.
[0033] Preferably, in the in-situ solidifiable sodium-ion secondary battery of the present application, the positive electrode material is a layered metal oxide, and the negative electrode material is hard carbon.
[0034] The present application has the following advantages:
[0035] (1) significantly improved safety performance
[0036] Excellent flame-retardant effect: dimethyl vinylphosphonate and / or diethyl vinylphosphonate in the electrolyte significantly improve the flame-retardant performance of the battery. In the case of battery misuse or accidental damage (such as puncture), the risk of fire can be effectively reduced or avoided.
[0037] Solves the problem of electrolyte leakage: the in-situ solidification technology is adopted to form a quasi-solid state structure of the electrolyte inside the battery, effectively avoiding the risk of electrolyte leakage of traditional liquid electrolyte, further enhancing the safety and reliability of the battery.
[0038] (2) excellent electrochemical performance
[0039] Excellent cycle performance: by reasonably selecting and proportioning dimethyl vinylphosphonate and / or diethyl vinylphosphonate, initiator, and other components, long cycle life of the sodium-ion battery is achieved.
[0040] Strong compatibility: the flame-retardant in-situ solidifiable electrolyte can be compatible with various positive electrode materials (such as layered metal oxides, polyanion-based positive electrode materials, and Prussian blue-based materials) and negative electrode materials (such as carbon-based materials), especially with hard carbon negative electrode, which widens the material selection range of sodium-ion batteries and provides more possibilities for the design and optimization of batteries.
[0041] (3) Simple production process: the preparation process of the in-situ solidifiable electrolyte is relatively simple, without the need for complex equipment and cumbersome process steps, which is conducive to large-scale production and application, and further reduces the manufacturing cost of the battery.
[0042] (4) Strong environmental adaptability
[0043] Good high-temperature stability: under high-temperature conditions, the addition of dimethyl vinylphosphonate and / or diethyl vinylphosphonate in the electrolyte can effectively inhibit the heat release of the positive electrode material, reducing the risk of thermal runaway inside the battery. BRIEF DESCRIPTION OF DRAWINGS
[0044] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings, in which:
[0045] Figure 1 showing the first charge-discharge curve of the battery of Example 1 at room temperature;
[0046] Figure 2 showing the performance graph of the battery of Example 1 after 800 cycles at room temperature;
[0047] Figure 3 showing the gas production graph of the battery of Comparative Example 6;
[0048] Figure 4 showing the picture of the solidified electrolyte of Example 12 DETAILED DESCRIPTION
[0049] The present application will be further described in detail below with reference to the specific embodiments, and the examples given are only to illustrate the present application, but not to limit the scope of the present application.
[0050] O3-Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2 as the positive active material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, and uniformly mixed in a mass ratio of 90:6:4. Then, N-methylpyrrolidone was added and a slurry was prepared. The slurry was coated on an aluminum foil. Vacuum drying was performed at 120°C overnight. After rolling, the positive electrode sheet was obtained. Hard carbon was used as the negative active material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, and uniformly mixed in a mass ratio of 90:5:5. Then, N-methylpyrrolidone was added and a slurry was prepared. The slurry was coated on an aluminum foil, vacuum dried at 120°C overnight. After rolling, the negative electrode sheet was obtained.
[0051] Preparation of electrolyte: In the glove box filled with argon, the sodium salt was weighed according to the data in Table 1. Then, a certain volume of solvent and additive was added. After stirring thoroughly, the prepared electrolyte was obtained. After adding a certain amount of monomer mixture, the initiator was added, and then the battery (18650 cylindrical battery) was injected, and after 10 hours of curing at 70°C, the capacity was tested after formation and the cycle performance and safety performance were tested. The needle test was carried out at full charge.
[0052] The English abbreviations in Table 1 are as follows:
[0053] TEP: triethyl phosphate; PC: propylene carbonate; EMC: ethyl methyl carbonate; DEC: diethyl carbonate; EC: ethylene carbonate; EP: propyl acetate; DEGDME: diethylene glycol dimethyl ether; THF: tetrahydrofuran; HFE: 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; VC: vinylene carbonate; TMPTA: trimethylolpropane triacrylate; MMA: methyl methacrylate; PETA: pentaerythritol triacrylate; PETTA: pentaerythritol tetraacrylate; DMVP dimethyl vinylphosphonate; DEVP: diethyl vinylphosphonate; DPVP: diisopropyl vinylphosphonate; AIBN: azobisisobutyronitrile; DCBP: di(2,4-dichlorobenzoyl) peroxide; FEC: fluoroethylene carbonate.
[0054]
[0055]
[0056] Figure 1 is the first charge-discharge curve of the battery of Example 1 at room temperature. Figure 1 shows the first charge-discharge curve of O3-Na[Cu 1 / 9 Ni 2 / 9Fe 1 / 3 Mn 1 / 3 ]O2 / / hard carbon full battery at 0.1C rate (1C=1.2Ah). It can be seen from Figure 1 that the capacity of the O3-Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2 / / hard carbon battery cell is about 1.2Ah. The flame-retardant in-situ solid-state electrolyte and carbon negative electrode are compatible, and the capacity is normally developed.
[0057] Figure 2 is the cycle performance graph of the battery of Example 1 at room temperature. From Figure 2As can be seen: the battery of Example 1 can be stably cycled for 800 times at room temperature, with a capacity retention rate of 85%. The flame-retardant in-situ solid-state electrolyte is compatible with the carbon negative electrode, and has good cycle performance.
[0058] The electrolyte of Examples 1-18 and Comparative Examples 1-4 was injected into a cylindrical battery (capacity of 1.2 Ah). The battery was cycled for 2 cycles, and the needle penetration test was performed under full charge. During the penetration process, the battery of Examples 1-18 did not smoke, did not catch fire, and did not explode. During the penetration process of the battery of Comparative Examples 1-4, there was thick smoke, which posed a safety hazard. This comparison shows that the polymerizable flame retardant DMVP helps to improve the safety performance of the battery. Acrylate monomers without flame retardance have poor safety and cannot pass the puncture test.
[0059] Although Comparative Example 9 and Example 13, and Comparative Example 10 and Example 12 contain the same volume fraction of flame-retardant solvent (TEP / DMVP), and are both semi-solid electrolytes, Comparative Examples 9 and 10 cannot pass the needle penetration test, indicating that the polymer formed by DMVP as a flame-retardant monomer has better safety. This may be because the flame-retardant DMVP forms a flame-retardant skeleton after polymerization, while TEP still has fluidity, which causes the difference in safety.
[0060] Examples 1-5 show that the solvent can be selected from carbonates, carboxylates, and ether solvents, and the battery has stable cycle performance and high capacity retention rate.
[0061] Examples 1 and 6, sodium salt selection NaPF6, or NaPF6 and NaFSI battery cycle performance is stable and the capacity retention rate is high.
[0062] Examples 1, 7-11 and Comparative Examples 5, 6 show that the ratio of the amount of monomer to initiator needs to be appropriate. Too low an amount of initiator (600: 1) leads to insufficient polymerization of the electrolyte, and too high a ratio of initiator (4: 1) leads to gas production of the initiator, which degrades the battery performance.
[0063] Examples 1, 12-15 and Comparative Examples 7-8 show that too little monomer DMVP (4%) leads to insufficient battery safety, which cannot pass the puncture test, and too much monomer DMVP (67%) leads to poor cycle performance of the battery.
[0064] Example 1, 16 shows that the selection of VC, FEC additives leads to stable cycle performance and high capacity retention rate of the battery.
[0065] Example 1, 17 shows that the selection of initiator DCPB leads to stable cycle performance and high capacity retention rate of the battery.
[0066] Examples 1, 18 and Comparative Example 11 show that dimethyl vinylphosphonate and diethyl vinylphosphonate have good safety and electrochemical properties. When diisopropyl vinylphosphonate is selected, it can not pass the needle penetration test because the chain length and phosphorus content are reduced.
Claims
1. A flame-retardant electrolyte that can be solidified in situ, comprising the following components: sodium salt, solvent and initiator; The solvent comprises a first solvent and a second solvent; wherein... The first solvent is selected from at least one of carbonate solvents, carboxylic acid ester solvents, and ether solvents; the second solvent is dimethyl vinylphosphonate and / or diethyl vinylphosphonate; and the second solvent accounts for 5%-65% of the volume fraction of the solvent.
2. The flame-retardant electrolyte that can be solidified in situ according to claim 1, wherein, The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonate), sodium trifluoromethanesulfonate, and sodium perchlorate. Preferably, the concentration of the sodium salt in the electrolyte is 0.1-2 mol / L.
3. The flame-retardant electrolyte that can be solidified in situ according to claim 1, wherein, The mass ratio of the second solvent to the initiator is second solvent: initiator = (5~500): 1; Preferably, the initiator comprises at least one of azobisisobutyronitrile, bis(2,4-dichlorobenzoyl) peroxide, diacetyl peroxide, dioctyl peroxide, dilauryl peroxide, dicarbonate peroxide, diisopropyl peroxide, diisobutyl peroxide, dicyclohexyl peroxide, and di(p-tert-butylcyclohexyl) peroxide.
4. The flame-retardant electrolyte that can be solidified in situ according to claim 1, wherein, The carbonate solvent is a cyclic carbonate solvent and / or a chain carbonate solvent; Preferably, the cyclic carbonate is ethylene carbonate and / or propylene carbonate; Preferably, the chain carbonate is a carbonate synthesized from a straight-chain or branched aliphatic monool with 3-8 carbon atoms and carbonic acid. Preferably, the chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate and methyl ethyl carbonate.
5. The flame-retardant electrolyte that can be solidified in situ according to claim 1, wherein, The ether solvent is selected from one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Preferably, the carboxylic acid ester solvent is a cyclic carboxylic acid ester solvent and / or a chain carboxylic acid ester solvent; More preferably, the cyclic carboxylic acid ester is γ-butyrolactone, and the chain carboxylic acid ester is a chain carboxylic acid ester with 3-8 carbon atoms; More preferably, the chain carboxylic ester is selected from one or more of methyl acetate, ethyl acetate, propyl acetate, propyl propionate and ethyl propionate.
6. The flame-retardant electrolyte that can be solidified in situ according to claim 1, wherein, The electrolyte also contains functional additives.
7. The flame-retardant electrolyte that can be solidified in situ according to claim 6, wherein, The functional additive is selected from one or more of ethylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, propenyl-1,3-sulfonate lactone, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, vinyl sulfate, dimethyl sulfite, diethyl sulfite, and succinate.
8. The flame-retardant electrolyte that can be solidified in situ according to claim 6, wherein, The functional additive has a mass fraction of 0.5-10% in the electrolyte.
9. A sodium-ion secondary battery capable of in-situ solidification, comprising a positive electrode material, a negative electrode material, and a flame-retardant electrolyte capable of in-situ solidification according to any one of claims 1-8.
10. The sodium-ion secondary battery capable of in-situ solidification according to claim 9, wherein, The positive electrode material is a layered metal oxide, a polyanionic positive electrode material, or a Prussian blue material, and the negative electrode material is a carbon material. Preferably, the positive electrode material is a layered metal oxide, and the negative electrode material is hard carbon.