Fluorinated phosphazene additive, electrolyte and solid-state battery

Abstract

The invention relates to a fluorinated phosphazene additive, an electrolyte and a solid-state battery. The additive is prepared through fluorination and substitution reactions, the reaction is continuous, and the operation is simple. The electrolyte is obtained by condensing a basic electrolyte, a fluorinated phosphazene additive, a condensation unit and a phase conversion agent. The fluorinated phosphazene additive provided by the invention has a high-toughness flame-retardant skeleton in a solid-state battery, can inhibit the growth of lithium dendrites, and can significantly improve the safety performance of an electrolyte; and meanwhile, an excellent SEI film is favorably formed on an electrode interface, the electrochemical performance of the electrode is improved, relatively good oxidation resistance is achieved, and the high-voltage long-cycle performance of the lithium battery can be promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and lithium ion batteries, and specifically relates to a fluorinated phosphazene additive, an electrolyte and a solid-state battery. Technical Background

[0002] Lithium-ion batteries have significant advantages such as low energy consumption, high specific capacity and specific energy, high operating voltage, long cycle life, low self-discharge, environmental friendliness, good cycle performance, and long life. They are widely used in portable electronic devices such as laptops, mobile phones, cameras, and mining lamps. With the increasing demand for environmentally friendly, safe and stable power sources and the development of electric vehicles, lithium-ion batteries, as green, environmentally friendly and high-energy batteries, have been more widely used.

[0003] However, lithium batteries are also prone to internal thermal runaway, which can cause the battery to burn or even explode, so it is usually necessary to add a suitable flame retardant, which can significantly improve the safety performance of the battery. Due to its special molecular structure, fluorinated phosphazene is not easy to open the ring and has excellent thermal stability. At the same time, due to the synergistic effect of phosphorus and nitrogen elements, compounds containing cyclotriphosphazene can absorb heat during high-temperature degradation and generate phosphates, metaphosphates and polyphosphates, forming a non-volatile protective film on the surface and releasing non-flammable gases such as CO2, NH3, and N2, thereby achieving a flame retardant effect; at the same time, fluorinated phosphazene helps to form an excellent SEI film at the electrode interface, improves the compatibility between the electrolyte and the active material, and then stabilizes the electrochemical properties of the electrode. It has good antioxidant resistance and can significantly improve the cycle performance of high-voltage batteries.

[0004] The method provided by patent CN102702268A is that hexachlorocyclotriphosphazene is first ethoxy-substituted and then fluorinated. However, due to the high activity of the P-C1 bond, it is difficult to control the monoethoxy substitution reaction of hexachlorocyclotriphosphazene in a single substitution state, resulting in low yield, difficult and complicated purification. The solution provided by patent CN110066295A is first perfluorinated and then ethoxy-substituted, but the first step of fluorination uses hydrogen fluoride gas, which reacts under the action of a catalyst, and hydrogen fluoride gas is extremely corrosive to glass and metal products, and it is difficult to store. Once leaked, it has a greater impact on the human body and the environment. Therefore, there are extremely high requirements for the storage and use of hydrogen fluoride, resulting in difficult operation. At the same time, the above method is difficult to achieve continuous production and is not easy to meet the requirements of industrial production. Summary of the invention

[0005] Technical problems to be solved: In view of the technical problems existing in the prior art that the monoethoxy substitution reaction of hexachlorocyclotriphosphazene is difficult to control in a monosubstituted state, has a low yield, is difficult and complicated to purify, hydrogen fluoride gas is extremely corrosive to glass and metal products, and is difficult to store. Once leaked, it has a great impact on the human body and the environment, the present invention provides a method for preparing fluorinated phosphazene which is green, environmentally friendly, simple and safe, has a continuous reaction process, and is safe for reaction preparation, as well as an electrolyte and a solid-state battery containing a fluorinated phosphazene additive.

[0006] A fluorinated phosphazene additive, an electrolyte and a solid-state battery, wherein the additive has the following structure:

[0007]

[0008] Wherein R1-R3 are independently selected from halogen, substituted or unsubstituted unsaturated alkane, substituted or unsubstituted unsaturated heteroalkane.

[0009] Furthermore, the method comprises the following steps:

[0010] Fluorination reaction: under stirring, at a temperature of 0°C-40°C, hexachlorocyclotriphosphazene, a fluorinating agent and a liquid catalyst are pumped into a distillation reactor in a ratio of 1 mol:6.5 mol:0.5 L to 1 mol:7.5 mol:5 L to react for 6 to 12 hours to purify hexafluorocyclotriphosphazene;

[0011] Substitution reaction: at a temperature of 40°C to 90°C, hexafluorocyclotriphosphazene, an organic salt and a solvent are introduced into a tubular reactor in a ratio of 1 mol:1 mol:0.1 L to 1 mol:3.75 mol:1 L to react for 10 to 30 minutes, and fluorinated phosphazene is purified and stored in a product collection tank; the by-product chloride is collected, and the fluorinating agent and the solvent are recovered.

[0012] Furthermore, the fluorinating agent is one or more of tetramethylammonium fluoride, tetraethylammonium fluoride, tetrabutylammonium fluoride, sodium hexafluorosilicate, lithium fluoride, sodium fluoride, magnesium fluoride, potassium fluoride, and calcium fluoride.

[0013] Furthermore, the liquid catalyst is one or more of 18-crown-6-ether, 15-crown-5-ether, 12-crown-4-ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol diisopropyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, and diethylene glycol monobutyl ether.

[0014] Furthermore, the solvent is one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N,N-dimethylformamide, N,N-diethylformamide, N-methylformamide, N-ethylformamide, dimethyl sulfoxide, tetramethyl urea, 1,1-dimethyl urea, and 1,3-dimethyl urea.

[0015] Furthermore, the organic salt includes but is not limited to potassium propylene oxide, potassium acrylate, potassium methacrylate, sodium propylene oxide, sodium acrylate, and sodium methacrylate.

[0016] An electrolyte is obtained by condensing a basic electrolyte, a fluorinated phosphazene additive, a condensation unit and a phase conversion agent.

[0017] Furthermore, the basic electrolyte consists of LiPF6 (1 mol / L) DMC / EC / FEC (v:v:v=6:3:1).

[0018] Furthermore, the mass fraction of the fluorinated phosphazene additive in the basic electrolyte is 0.1%-5%.

[0019] Furthermore, the coagulation unit includes but is not limited to methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and the mass fraction of the coagulation unit in the basic electrolyte is 1%-20%.

[0020] Furthermore, the phase conversion agent includes but is not limited to azobisisobutyronitrile, boron trifluoride, potassium amide, and butyl lithium, and the mass fraction of the phase conversion agent in the basic electrolyte is 0.1%-2%.

[0021] A solid-state battery consists of a positive electrode shell, a positive electrode sheet, a diaphragm, an electrolyte, a negative electrode sheet, a gasket, a spring sheet, and a negative electrode shell.

[0022] Furthermore, commercial lithium cobalt oxide positive electrode material, conductive carbon black Super P and PVDF were added to N-methylpyrrolidone in a mass ratio of 7:2:1, dispersed into a uniform slurry at high speed, and coated on aluminum foil with a coater and dried at 80°C, then cut into 15mm positive electrode sheets, rolled at 1MPa pressure, and then vacuum dried at 100°C for 24h and transferred to a glove box. With metal lithium sheet as negative electrode, Celgard-2500 diaphragm, 35μL target electrolyte was taken, and the positive electrode sheet coated with NCM811 active material was assembled into a battery in the order of positive electrode shell / positive electrode sheet / diaphragm / negative electrode sheet / gasket / spring sheet / negative electrode shell, left to stand for 24h, thermally cured at 60°C for 3h, and finally packaged using a manual hydraulic battery packaging machine.

[0023] Principle explanation:

[0024] The addition of a liquid catalyst in the reaction of synthesizing hexafluorocyclotriphosphazene reduces the activation energy of the reaction, allowing the fluorination reaction to occur at a lower temperature, while the reaction without the participation of a liquid catalyst requires a higher temperature to promote the reaction, but high temperature will also promote the occurrence of side reactions; negative pressure operation is used in this scheme, the purpose of which is to allow the generated fluorinated phosphazene to separate from the reaction system while retaining other substances, thereby promoting the reaction to proceed in the forward direction.

[0025] The reaction for synthesizing fluorinated phosphazene is a "fast" reaction. When the reaction temperature is reached, hexafluorocyclotriphosphazene and organic salt will quickly generate fluorinated phosphazene. In order to prevent the occurrence of side reactions, the reaction temperature and reaction time need to be strictly controlled, so a shell-and-tube reactor is used.

[0026] Beneficial effects:

[0027] 1. The method for preparing fluorinated phosphazene of the present invention uses fewer types of reaction raw materials and does not involve hazardous chemicals. The raw materials are cheap and easily available, the reaction process is continuous, the reaction preparation is safe, and the operation is simple. The purity of the hexafluorocyclotriphosphazene and the fluorinated phosphazene is above 99.5%, the yield is above 90%, and the reaction materials can be recycled, which is more suitable for industrial production.

[0028] 2. The fluorinated phosphazene provided by the present invention is modified with unsaturated functional groups. When making solid-state batteries, it can be polymerized through a phase conversion agent to obtain a highly tough molecular skeleton, which can reduce the amount of additives used, improve the flame retardant efficiency, and significantly improve the safety performance of the electrolyte. It can completely prevent the safety hazards of fire, combustion, and explosion caused by battery abuse and overcharging; under the synergistic effect of N, P, and F, it helps to form an excellent SEI film at the electrode interface, improve the compatibility between the electrolyte and the active material, and then stabilize the electrochemical properties of the electrode, have good antioxidant resistance, and can significantly improve the cycle performance of the high-voltage battery.

[0029] 3. The solid-state battery made of the fluorinated phosphazene additive provided by the present invention has been tested and has excellent performance. After 300 cycles at room temperature under a high voltage of 4.35V, its capacity retention rate is as high as 99.2%, and the self-extinguishing time of the combustion test is 0s / g, that is, it is non-flammable. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of continuous flow preparation process of fluorinated phosphazene additive

[0031] Figure 2 The H NMR and C NMR spectra of 1,3,5-trifluorocyclotriphosphazene tri(meth)acrylate DETAILED DESCRIPTION

[0032] Unless otherwise defined, technical terms or scientific terms used in the claims and the specification shall have the ordinary meanings understood by persons having ordinary skills in the technical field to which the present invention belongs. Unless otherwise specified, all parts are parts by weight and all percentages are percentages by weight.

[0033] The present invention will be further described below in conjunction with specific implementation modes, but the present invention is not limited to the following specific implementation modes.

[0034] The present invention will be further described in detail below in conjunction with specific examples to make the advantages of the present invention more obvious. It should be understood that the contents thereof are only used for illustration and are by no means intended to limit the scope of protection of the present invention. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0035] Synthesis of Hexafluorocyclotriphosphazene

[0036] Method 1: Under stirring, at a temperature of 25° C., a mixed liquid of 1 mol of hexachlorocyclotriphosphazene, 7 mol of sodium fluoride, and 1 L of 12-crown-4-ether is pumped into a dry 2000 ml distillation reactor, and distilled under a -0.07 MPa environment for 6 to 12 hours. When GC-MS shows that there is no hexachlorocyclotriphosphazene in the system, hexafluorocyclotriphosphazene with a purity of 99.81% and a yield of 94.7% is obtained.

[0037] Method 2: Under stirring, at a temperature of 10°C, a mixed liquid of 1 mol of hexachlorocyclotriphosphazene, 6.5 mol of potassium fluoride, and 1 L of diethylene glycol monobutyl ether is pumped into a dry 2000 ml distillation reactor, and distilled under a -0.07 MPa environment for 6 to 12 hours. When GC-MS shows that there is no hexachlorocyclotriphosphazene in the system, hexafluorocyclotriphosphazene with a purity of 99.69% and a yield of 91.7% is obtained.

[0038] Method 3: Under stirring, at a temperature of 30°C, a mixed liquid of 1 mol of hexachlorocyclotriphosphazene, 7.5 mol of lithium fluoride and 1 L of diethylene glycol monomethyl ether is pumped into a dry 2000 ml distillation reactor, and distilled under a -0.07 MPa environment for 6 to 12 hours. When GC-MS shows that there is no hexachlorocyclotriphosphazene in the system, hexafluorocyclotriphosphazene with a purity of 99.72% and a yield of 92.5% is obtained.

[0039] Synthesis of Fluorinated Phosphazene

[0040] Compound 1 - Propyleneoxypentafluorocyclotriphosphazene

[0041] Take 1 mol of hexafluorocyclotriphosphazene, 1.01 mol of sodium propylene oxide and 100 ml of tetramethyl urea, put them into a tubular reactor at a temperature of 40°C and react continuously for 10 minutes. The generated crude product is continuously distilled out through a rectification kettle to obtain the solvent tetramethyl urea and a product with a purity of 99.67% and a yield of 92.9%. The residue is purified by pulping to obtain sodium fluoride, which is recovered and used as a fluorinating agent.

[0042] Compound 2 - Pentafluorocyclotriphosphazene acrylate

[0043] Take 1 mol of hexafluorocyclotriphosphazene, 1.01 mol of potassium acrylate and 100 ml of solvent N,N-dimethylformamide, put them into a tubular reactor at a temperature of 45°C for continuous reaction for 15 minutes, and the generated crude product is continuously distilled out through a rectification kettle to obtain solvent N,N-dimethylformamide and a product with a purity of 99.84% and a yield of 91.24%. The residue is purified by pulping to obtain potassium fluoride, which is recovered and used as a fluorinating agent.

[0044] Compound 3 - Pentafluorocyclotriphosphazene methacrylate

[0045] 1 mol of hexafluorocyclotriphosphazene, 1.01 mol of sodium methacrylate and 100 ml of solvent N,N-dimethylacetamide were placed in a tubular reactor at a temperature of 45°C for continuous reaction for 15 minutes. The generated crude product was continuously distilled out through a rectification kettle to obtain solvent N,N-dimethylacetamide and a product with a purity of 99.87% and a yield of 93.66%. The residue was purified by pulping to obtain sodium fluoride, which was recovered and used as a fluorinating agent.

[0046] Compound 4——1,3-Dipropyleneoxytetrafluorocyclotriphosphazene

[0047] Take 1 mol of hexafluorocyclotriphosphazene, 2.01 mol of sodium propylene oxide and 200 ml of tetramethyl urea, put them into a tubular reactor at a temperature of 55°C for continuous reaction for 15 minutes, and the generated crude product is continuously distilled out through a rectification kettle to obtain the solvent tetramethyl urea and a product with a purity of 99.58% and a yield of 93.69%. The residue is purified by pulping to obtain sodium fluoride, which is recovered and used as a fluorinating agent.

[0048] Compound 5——1,1,3,5-tetrafluorocyclotriphosphazene diacrylate

[0049] Take 1 mol of hexafluorocyclotriphosphazene, 2.01 mol of potassium acrylate and 200 ml of solvent N,N-dimethylformamide, put them into a tubular reactor at a temperature of 65°C for continuous reaction for 20 minutes, and the generated crude product is continuously distilled out through a rectification kettle to obtain solvent N,N-dimethylformamide and a product with a purity of 99.67% and a yield of 93.01%. The residue is purified by pulping to obtain potassium fluoride, which is recovered and used as a fluorinating agent.

[0050] Compound 6——1,1,3,5-tetrafluorocyclotriphosphazene di(meth)acrylate

[0051] Take 1 mol of hexafluorocyclotriphosphazene, 2.01 mol of sodium methacrylate and 200 ml of solvent N, N-dimethylacetamide, put them into a tubular reactor at a temperature of 65°C for continuous reaction for 20 minutes, and the generated crude product is continuously distilled out through a rectification kettle to obtain solvent N, N-dimethylacetamide and a product with a purity of 99.61% and a yield of 93.74%. The residue is purified by pulping to obtain sodium fluoride, which is recovered and used as a fluorinating agent.

[0052] Compound 7——1,3,5-Tripropyleneoxytrifluorocyclotriphosphazene

[0053] 1 mol of hexafluorocyclotriphosphazene, 3.5 mol of sodium propylene oxide and 300 ml of tetramethyl urea were placed in a tubular reactor at 75°C for continuous reaction for 25 minutes. The resulting crude product was continuously distilled out through a rectification kettle to obtain the solvent tetramethyl urea and a product with a purity of 99.62% and a yield of 94.71%. The residue was purified by pulping to obtain sodium fluoride, which was recovered and used as a fluorinating agent.

[0054] Compound 8——1,3,5-Trifluorocyclotriphosphazene triacrylate

[0055] Take 1 mol of hexafluorocyclotriphosphazene, 3.5 mol of potassium acrylate and 300 ml of solvent N,N-dimethylformamide, put them into a tubular reactor at a temperature of 85°C for continuous reaction for 30 minutes, and the generated crude product is continuously distilled out through a rectification kettle to obtain solvent N,N-dimethylformamide and a product with a purity of 99.53% and a yield of 95.22%. The residue is purified by pulping to obtain potassium fluoride, which is recovered and used as a fluorinating agent.

[0056] Compound 9——1,3,5-Trifluorocyclotriphosphazene tri(meth)acrylate

[0057] 1 mol of hexafluorocyclotriphosphazene, 3.5 mol of sodium methacrylate and 300 ml of solvent N,N-dimethylacetamide are placed in a tubular reactor at a temperature of 90°C for continuous reaction for 30 minutes. The generated crude product is continuously distilled out through a rectification kettle to obtain solvent N,N-dimethylacetamide and a product with a purity of 99.74% and a yield of 94.53%. The residue is purified by pulping to obtain sodium fluoride, which is recovered and used as a fluorinating agent.

[0058] Fluorinated phosphazene additives for high voltage room temperature cycling performance test and flame retardant performance test of electrolyte

[0059] Embodiment 1:

[0060] 1. Preparation of electrolyte: DMC, EC and FEC were mixed in a volume ratio of DMC:EC:FEC=6:3:1, and lithium hexafluorophosphate (concentration 1M) was added to form a basic electrolyte. Then, 15% of methyl acrylate (mass of methyl acrylate / mass of basic electrolyte=15%, the same below), 1% of azobisisobutyronitrile and 5% of compound 1 were added and mixed uniformly to obtain an electrolyte.

[0061] 2. Production of solid-state batteries: Commercial lithium cobalt oxide positive electrode materials, conductive carbon black Super P and PVDF are added to N-methylpyrrolidone in a mass ratio of 7:2:1, dispersed into a uniform slurry at high speed, and coated on aluminum foil with a coater and dried at 80°C, then cut into 15mm positive electrode sheets, rolled at 1MPa pressure, and then vacuum dried at 100°C for 24h and transferred to a glove box. With metal lithium sheet as the negative electrode, Celgard-2500 is used as the diaphragm, 35μL of the target electrolyte is taken, and the positive electrode sheet coated with NCM811 active material is assembled into a battery in the order of positive electrode shell / positive electrode sheet / diaphragm / negative electrode sheet / gasket / spring sheet / negative electrode shell, left to stand for 24h, thermally cured at 60°C for 3h, and finally packaged using a manual hydraulic battery packaging machine.

[0062] In Examples 2 to 9, the preparation of the electrolyte and the fabrication of the solid-state battery are consistent with those in Example 1, but the compounds therein are changed to Compounds 2 to 9, respectively.

[0063] Comparative Examples 1 to 3, the electrolyte preparation method and the battery preparation method refer to Example 1, and the additives are pentafluorocyclotriphosphazene propionate, 1,1,3,5-tetrafluorocyclotriphosphazene dipropionate and 1,3,5-trifluorocyclotriphosphazene tripropionate.

[0064] Comparative Examples 1 to 3, the electrolyte preparation method and the battery preparation method refer to Example 1, and the additives are no additive, 1,3-propane sultone and DTD respectively.

[0065] Cyclic performance test: Charge at 1.0C constant current to 4.35V at 25℃, charge at 4.35V constant voltage to cut-off current 0.05C, then discharge at 1.0C constant current, discharge capacity is recorded as C0, repeat the charge and discharge steps for 300 cycles, and obtain the 300th cycle discharge capacity C 300 , capacity retention rate = C 300 / C0*100%;

[0066] Flame retardant performance test: 1 g of the above electrolyte was placed on the bottom surface of a coin unit battery can 2032 (Hohsen Corp, Osaka, Japan), which was ignited, and the self-extinguishing time (SET) was recorded and expressed as time per unit weight (s / g).

[0067] The results are shown in the following table:

[0068]

[0069]

[0070] From the comparison of Examples 1 to 9 and Comparative Examples 1 to 3 in the above table, it can be seen that the electrolyte using the fluorinated phosphazene additive of the present invention can significantly improve the room temperature cycle performance of the lithium hexafluorophosphate solid-state battery at high voltage, and effectively improve the flame retardant properties of the electrolyte; and by comparing Examples 1 to 9 with Comparative Examples 1 to 3, the additive of the present invention has more advantages in cycle performance and flame retardant properties, indicating that the fluorinated phosphazene modified with unsaturated functional groups can be polymerized by a phase conversion agent to obtain a high-toughness molecular skeleton when making a solid-state battery, which helps to improve the room temperature cycle performance and flame retardant properties of the lithium hexafluorophosphate solid-state battery at high voltage, and has a good application prospect in the field of lithium battery electrolytes.

[0071] The above description is only an implementation case of the present invention, and does not limit the scope of protection claimed by the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, is also included in the scope of protection claimed by the present invention.

Claims

1. A fluorinated phosphazene additive, an electrolyte and a solid-state battery, wherein the additive has the following structure: Wherein R1-R3 are independently selected from halogen, substituted or unsubstituted unsaturated alkane, substituted or unsubstituted unsaturated heteroalkane.

2. A method for preparing fluorinated phosphazene, characterized in that: The method comprises the following steps: Fluorination reaction: under stirring, at a temperature of 0°C-40°C, hexachlorocyclotriphosphazene, a fluorinating agent and a liquid catalyst are pumped into a distillation reactor in a ratio of 1 mol:6.5 mol:0.5 L to 1 mol:7.5 mol:5 L to react for 6 to 12 hours to purify hexafluorocyclotriphosphazene; Substitution reaction: at a temperature of 40°C to 90°C, hexafluorocyclotriphosphazene, an organic salt and a solvent are introduced into a tubular reactor in a ratio of 1 mol:1 mol:0.1 L to 1 mol:3.75 mol:1 L to react for 10 to 30 minutes, and fluorinated phosphazene is purified and stored in a product collection tank; the by-product chloride is collected, and the fluorinating agent and the solvent are recovered.

3. The method for preparing fluorinated phosphazene according to claim 2, characterized in that: The fluorinating agent is one or more of tetramethylammonium fluoride, tetraethylammonium fluoride, tetrabutylammonium fluoride, sodium hexafluorosilicate, lithium fluoride, sodium fluoride, magnesium fluoride, potassium fluoride, and calcium fluoride.

4. The method for preparing fluorinated phosphazene according to claim 2, characterized in that: The liquid catalyst is one or more of 18-crown-6-ether, 15-crown-5-ether, 12-crown-4-ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol diisopropyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, and diethylene glycol monobutyl ether.

5. The method for preparing fluorinated phosphazene according to claim 2, characterized in that: The solvent is one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N,N-dimethylformamide, N,N-diethylformamide, N-methylformamide, N-ethylformamide, dimethyl sulfoxide, tetramethyl urea, 1,1-dimethyl urea, and 1,3-dimethyl urea.

6. The method for preparing fluorinated phosphazene according to claim 2, characterized in that: The organic salts include, but are not limited to, potassium acrylate, potassium methacrylate, sodium acrylate, sodium acrylate, and sodium methacrylate.

7. An electrolyte, characterized in that The electrolyte is obtained by condensing a basic electrolyte, a fluorinated phosphazene additive, a condensation unit and a phase conversion agent.

8. The method for preparing an electrolyte according to claim 7, characterized in that: The basic electrolyte is composed of LiPF6 (1 mol / L) DMC / EC / FEC (v:v:v=6:3:1).

9. The method for preparing an electrolyte according to claim 7, characterized in that: The mass fraction of the fluorinated phosphazene additive in the basic electrolyte is 0.1%-5%.

10. The method for preparing an electrolyte according to claim 7, characterized in that: The coagulation unit includes but is not limited to methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and the mass fraction of the coagulation unit in the basic electrolyte is 1%-20%.

11. The method for preparing an electrolyte according to claim 7, characterized in that: The phase conversion agent includes but is not limited to azobisisobutyronitrile, boron trifluoride, potassium amide, and butyl lithium. The mass fraction of the phase conversion agent in the basic electrolyte is 0.1%-2%.

12. A solid-state battery, characterized in that: The solid-state battery consists of a positive electrode shell, a positive electrode sheet, a separator, an electrolyte, a negative electrode sheet, a gasket, a spring sheet, and a negative electrode shell.

13. The method for preparing a solid-state battery according to claim 9, characterized in that: The commercial lithium cobalt oxide positive electrode material, conductive carbon black Super P and PVDF were added to N-methylpyrrolidone in a mass ratio of 7:2:1, dispersed into a uniform slurry at high speed, and coated on aluminum foil with a coater and dried at 80°C, then cut into 15mm positive electrode sheets, rolled at 1MPa pressure, and then vacuum dried at 100°C for 24h and transferred to a glove box. With a metal lithium sheet as the negative electrode, Celgard-2500 was used as the diaphragm, 35μL of the target electrolyte was taken, and the positive electrode sheet coated with NCM811 active material was assembled into a battery in the order of positive electrode shell / positive electrode sheet / diaphragm / negative electrode sheet / gasket / spring sheet / negative electrode shell, left to stand for 24h, thermally cured at 60°C for 3h, and finally packaged using a manual hydraulic battery packaging machine.

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