Non-combustible and high-voltage-resistant electrolyte, preparation method and potassium ion battery

Abstract

The invention relates to a non-flammable and high-voltage-resistant electrolyte, a preparation method and a potassium ion battery, and the method comprises the following steps: in a glove box in which the water content and the oxygen content are below a certain value, dissolving a sylvite solute in a non-flammable phosphate ester solvent, fully dissolving, and standing for 2 hours to prepare a mixed solution formed by the sylvite solute and the non-flammable phosphate ester solvent; and adding a high-voltage additive into the mixed solution, fully mixing, and standing for 12 hours to prepare the non-combustible and high-voltage-resistant electrolyte. The method disclosed by the invention has the advantages that the electrolyte is simple in manufacturing process, low in cost and incombustible, and meanwhile, the prepared electrolyte has good oxidation stability and reduction stability, and can give consideration to a 4.4 V high-voltage positive electrode and a low-voltage graphite negative electrode when being applied to the potassium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of potassium ion batteries, and in particular relates to a non-flammable and high-voltage resistant electrolyte, a preparation method and a potassium ion battery. Background Art

[0002] At present, lithium-ion batteries (LIBs) with high energy density and long cycle life have become an important power source in the field of portable electronic devices and electric vehicles. However, lithium and cobalt required for LIBs are costly and relatively scarce elements. With the rapid development of the electric vehicle market, the demand for these material resources is also growing. In addition, lithium and cobalt resources are unevenly distributed, mainly in South America and the Republic of Congo, which leads to an urgent need to develop new rechargeable batteries to supplement the development of LIBs. At present, potassium ion batteries (KIBs) are a low-cost option that can supplement LIBs. Potassium resources are widely distributed and abundant on the earth, and the cost is low. In addition, KIBs provide higher voltage than sodium ion batteries (SIBs) or even LIBs. Due to their obvious cost advantages and sustainable supply characteristics, potassium ion batteries have attracted much attention in large-scale grid energy storage. The electrolyte plays a vital role in the battery. As a conductive medium, it maintains the chemical reaction of the battery and the flow of current by transferring ions between the positive and negative electrodes. During the charging and discharging process, the ions in the electrolyte move to ensure the effective energy storage and release of the battery. In addition, the electrolyte also directly affects the energy density, safety and cycle life of the battery. Until now, carbon materials such as graphite are relatively promising negative electrode materials for KIBs, and Prussian blue analogs (PBAs) are the most promising positive electrode materials. Due to the requirements for high voltage characteristics and cycle life of batteries, traditional electrolytes can no longer meet the needs of potassium ion batteries, so there is an urgent need to develop electrolytes that meet high voltage stable cycles.

[0003] Considering the use of carbon materials as negative electrode materials, the electrolyte should have good anti-reduction properties at low pressures, and the anti-reduction properties of the electrolyte mainly depend on the stability of the solid electrolyte interface film formed by the electrolyte at the solid-liquid interface. Traditional carbonate electrolytes have good film-forming properties at the negative electrode and can form a stable solid electrolyte interface film. However, considering that high-voltage materials are used for the positive electrode, carbonate electrolytes have poor oxidation stability and are prone to oxidative decomposition under high pressure, accelerating interfacial side reactions and affecting the cycle life of the battery. However, some high-voltage resistant electrolytes show very poor cycle stability at graphite negative electrodes. At the same time, traditional electrolytes are all flammable organic substances, which are prone to thermal runaway at high temperatures, causing battery safety issues. Therefore, the development of a high-voltage resistant and non-flammable electrolyte is crucial to the commercialization of potassium ion batteries. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides a non-flammable and high-voltage resistant electrolyte, a preparation method and a potassium ion battery.

[0005] A method for preparing a non-flammable and high-voltage resistant electrolyte, the method comprising the steps of: S1. dissolving a potassium salt solute in a non-flammable phosphate solvent in a glove box where the water and oxygen contents are below a certain value, fully dissolving and standing for 2 hours to prepare a mixed solution of the potassium salt solute and the non-flammable phosphate solvent;

[0006] S2. Add high-voltage additives to the mixed solution, mix thoroughly, and let stand for 12 hours to prepare a non-flammable and high-voltage resistant electrolyte.

[0007] According to the aspects and any possible implementation described above, an implementation is further provided, wherein the potassium salt solute is at least one or more of potassium hexafluorophosphate KPF6, bis(fluorosulfonyl)imide potassium salt KFSI, bis(trifluorosulfonyl)imide potassium salt KTFSI, potassium perchlorate KClO4, potassium nitrate KNO3, and potassium tetrafluoroborate KBF4.

[0008] According to the above aspects and any possible implementation, an implementation is further provided, wherein the non-flammable phosphate ester solvent is one or more of trimethyl phosphate (TMP), triethyl phosphate (TEP), tripropyl phosphate (TPP), tributyl phosphate (TBP), and tris(2,2,2-trifluoroethyl) phosphate (FTEP).

[0009] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the high-pressure additive is one or more of 1,1,2,3,3,3-hexafluoropropyl methyl ether HM, perfluorobutyl ethyl ether EFE, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether OTE, hexafluoroisopropyl methyl ether HME, 1,1,2,2-tetrafluoroethyl ether ETE, 1,1,2,2,-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether TTE, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether HFE.

[0010] According to the above aspects and any possible implementation, an implementation is further provided, wherein the potassium salt solute, the non-flammable organic solvent and the high-pressure resistant additive are all analytically pure with a purity of ≥99.5% and a moisture content of less than 1 ppm.

[0011] The present invention also provides a non-flammable and high-voltage resistant electrolyte, which is obtained by using the preparation method.

[0012] The present invention also provides a potassium ion battery, which comprises a negative electrode sheet or potassium metal, the electrolyte of the present invention, and a diaphragm and a positive electrode sheet arranged in sequence.

[0013] According to the aspects and any possible implementation methods described above, an implementation method is further provided, in which the positive electrode sheet preparation process includes: using a Prussian blue analogue K2Mn[Fe(CN)6] as a positive electrode active material, mixing it with conductive carbon and a binder in a certain mass ratio, adding a solvent, stirring evenly, and then coating it on an aluminum foil current collector, and obtaining a positive electrode sheet after vacuum drying at 80°C for 12 hours.

[0014] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the preparation process of the negative electrode sheet includes: using commercial graphite as an active material, mixing it with a binder in a certain mass ratio, adding water and stirring evenly, and then coating it on an aluminum foil current collector, and vacuum drying at 80°C to obtain the negative electrode sheet.

[0015] According to the above aspects and any possible implementation, there is further provided an implementation, in which the capacity ratio of the negative electrode sheet to the positive electrode sheet is 1.05 to 1.2:1.

[0016] Beneficial effects of the present invention

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a non-flammable and high-voltage resistant electrolyte and a preparation method, the method comprising the steps of: in a glove box with water and oxygen content below a certain value, dissolving a potassium salt solute in a non-flammable phosphate solvent, fully dissolving and standing for 2 hours, and preparing a mixed solution formed by the potassium salt solute and the non-flammable phosphate solvent; adding a high-voltage additive to the mixed solution, fully mixing, standing for 12 hours, and preparing a non-flammable and high-voltage resistant electrolyte. The advantages of the method of the present invention are: the electrolyte has a simple manufacturing process, low cost, and is non-flammable. At the same time, the prepared electrolyte has good oxidation stability and reduction stability. When applied to potassium ion batteries, it can take into account 4.4V high-voltage positive electrode and low-voltage graphite negative electrode. Under the high-voltage positive electrode of Prussian blue analogue, after 500 cycles, the capacity retention rate of the battery is as high as 94.2%, and the capacity is almost not attenuated. The graphite negative electrode can show high specific capacity (close to the theoretical specific capacity) and high first-week coulomb efficiency (>85%) in the electrolyte. At the same time, the electrolyte uses non-flammable organic solvents and fluorine-containing high-pressure additives, which is completely non-flammable and completely superior to traditional carbonate electrolytes in terms of electrochemical performance and safety. The potassium ion battery composed of the positive electrode of the Prussian blue analog and the graphite and hard carbon negative electrode shows good potassium storage performance, high energy density, high safety and excellent cycle stability in a wide voltage window of 4.3V-1.5V. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 mol L in Example 1 -1 When KFSI / TEP / TTE electrolyte was used, the positive electrode of K2Mn[Fe(CN)6] was 15.5 mA g -1 Charge and discharge curves under current density;

[0020] Figure 2 1 mol L in Example 1 -1 When KFSI / TEP / TTE electrolyte was used, K2Mn[Fe(CN)6] cathode was at 75 mA g -1 Cyclic stability diagram at current density;

[0021] Figure 3 1 mol L in Example 1 -1 When KFSI / TEP / TTE electrolyte is used, the graphite anode is at 27.9 mA g -1 Charge and discharge curves under current density;

[0022] Figure 4 1 mol L in Example 1 -1 When KFSI / TEP / TTE electrolyte is used, the graphite anode is at 27.9 mA g -1 Cyclic stability diagram at current density;

[0023] Figure 5 1 mol L in Example 1 -1 KFSI / TEP / TTE electrolytes for potassium ion full battery at 15.5 mA g -1 The first charge and discharge curve at current density;

[0024] Figure 6 1 mol L in Example 1 -1 KFSI / TEP / TTE electrolytes for potassium ion full cells at 75 mA g -1 Cyclic stability diagram at different current densities. DETAILED DESCRIPTION

[0025] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods described below, and similar technologies and methods should be considered to be within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] It should be clear that the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0028] The present invention provides a method for preparing a non-flammable and high-voltage resistant electrolyte, the method comprising the steps of: S1. in a glove box where the water and oxygen contents are below a certain value, dissolving a potassium salt solute in a solvent, fully dissolving and standing for 2 hours to prepare a mixed solution of the potassium salt solute and a non-flammable phosphate solvent;

[0029] S2. Add high-voltage resistant additives to the mixed solution, mix thoroughly, and let stand for 12 hours to prepare a non-flammable and high-voltage resistant electrolyte.

[0030] The electrolyte potassium salt solute of the present invention is one or more of at least one of potassium hexafluorophosphate KPF6, bis(fluorosulfonyl)imide potassium salt KFSI, bis(trifluorosulfonyl)imide potassium salt KTFSI, potassium perchlorate KClO4, potassium nitrate KNO3, and potassium tetrafluoroborate KBF4. Preferably, the salt concentration is 0.5 mol / L to 3 mol / L, and the electrolyte has a suitable ionic conductivity within this concentration range. Too high or too low a concentration will have a low ionic conductivity.

[0031] The solvent used to prepare the electrolyte is a non-flammable phosphate solvent, and the non-flammable phosphate solvent is one or more of trimethyl phosphate TMP, triethyl phosphate TEP, tripropyl phosphate TPP, tributyl phosphate TBP, and tri(2,2,2-trifluoroethyl) phosphate FTEP.

[0032] The high-pressure resistant additive is one or more of 1,1,2,3,3,3-hexafluoropropyl methyl ether HM, perfluorobutyl ethyl ether EFE, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether OTE, hexafluoroisopropyl methyl ether HME, 1,1,2,2-tetrafluoroethyl ether ETE, 1,1,2,2,-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether TTE, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether HFE.

[0033] Preferably, the volume ratio of the non-flammable phosphate ester solvent to the high-pressure resistant additive is 1:0.5-5. The additive at this ratio can provide better high-pressure resistance performance (.

[0034] In a specific implementation, the potassium salt solute, the non-flammable organic solvent and the high-pressure resistant additive in the electrolyte are all analytically pure, with a purity of ≥99.5%, and a water content of less than 1 ppm.

[0035] Preferably, the positive electrode active material of the positive electrode sheet is one of the Prussian blue analogs, with a mass ratio of 70wt.% to 95wt.%, and a total mass ratio of the conductive carbon and the binder of 30wt.% to 5wt.%. The positive electrode sheet under this ratio can provide higher conductivity and adhesion. The sum of the mass ratios of the positive electrode active material, the conductive carbon and the binder is 100%. The loading amount of the positive electrode active material is controlled at 0.1mg cm -2 Up to 20 mg cm -2 range, the positive electrode sheet has good activity within this range.

[0036] In a specific implementation, preferably, the negative electrode active material of the negative electrode sheet is selected from carbon materials such as graphite or hard carbon, with a mass ratio of 70wt.% to 96wt.%, and a total mass ratio of conductive carbon and binder of 30wt.% to 4wt.%. The negative electrode sheet under this ratio can provide higher conductivity and adhesion. Similarly, the sum of the mass ratios of the negative electrode active material, conductive carbon and binder is 100%. The loading amount of the negative electrode active material is also controlled at 0.1mg cm -2 Up to 20 mg cm -2 range, the positive electrode sheet has good activity within this range.

[0037] In a specific implementation, in the potassium ion battery of the present invention, the capacity ratio of the negative electrode sheet to the positive electrode sheet is preferably between 1.05:1 and 1.2:1. The capacity ratio within this range can avoid potassium deposition and capacity loss effects.

[0038] In specific implementation, the conductive carbon used in the positive electrode sheet and the negative electrode sheet can be selected from one or more of acetylene black, Ketjen black, carbon nanotubes or graphene. These materials can be the same in the positive electrode sheet and the negative electrode sheet, or different.

[0039] In a specific implementation, the binder in the positive electrode sheet is preferably one of polyvinylidene fluoride PVDF or polytetrafluoroethylene PTFE.

[0040] In a specific implementation, the binder in the negative electrode sheet can be selected from PVDF, PTFE, polyvinyl alcohol PVA, sodium carboxymethyl cellulose CMC or sodium alginate.

[0041] In specific implementation, aluminum foil is selected as the current collector of both the positive and negative electrode sheets.

[0042] In a specific implementation, the separator of the potassium ion battery can be selected from one of polyethylene PE, polypropylene PP, polyvinylidene fluoride PVDF, polyimide PI or glass fiber.

[0043] As an embodiment disclosed in the present invention, the present invention also provides an electrolyte obtained by the preparation method of the present invention. The electrolyte introduces a high-voltage resistant additive that reduces concentration and viscosity into a non-flammable phosphate electrolyte, reduces the binding of solvent molecules and metal cations through the intermolecular action between two or more solvents, and promotes more anions to enter the solvation shell, so that the anions decompose on the surface of the negative electrode to form a stable solid electrolyte interface film. At the same time, the addition of high-voltage resistant additives further enhances the oxidative stability of the phosphate electrolyte, thereby improving the high-voltage stability of the potassium ion battery. In addition, the non-flammability of phosphate reduces the thermal runaway phenomenon of the battery and ensures the safe and stable circulation of the battery.

[0044] As an embodiment disclosed by the present invention, the present invention also provides a potassium ion battery, comprising a negative electrode sheet or potassium metal arranged in sequence, the electrolyte of the present invention, and a diaphragm and a positive electrode sheet arranged therein, wherein the non-flammable and high-voltage resistant electrolyte is used as an electrolyte for a safe potassium ion battery. The present invention solves the problem that the current potassium ion battery electrolyte cannot simultaneously meet high-voltage stability and low-pressure decomposition through a simple improvement strategy, while taking into account non-flammability, effectively improving the overall cycle stability, safety, and rate performance of the potassium ion battery, and realizing a practical potassium ion battery with high energy density, long cycle life, high capacity retention rate, and non-flammability, meeting the design requirements of commercial energy storage batteries.

[0045] The potassium ion battery is a full battery or a half battery.

[0046] In the full cell and half cell, the positive electrode material is a Prussian blue analogue, such as potassium manganese hexacyanoferrate (K2Mn[Fe(CN)6]), and the negative electrode material is graphite or hard carbon.

[0047] The potassium ion battery is specifically a button battery, a soft pack battery or a cylindrical battery, without specific limitation.

[0048] In the specific implementation, in the process of preparing the electrode sheet, when the binder is PVDF, the solvent used is N-methylpyrrolidone (NMP); when the binder is PTFE, the solvent used is ethanol; when the binder is CMC or sodium alginate, the solvent used is water.

[0049] It should be noted that when preparing electrode slurry, there is no strict requirement for the mixing ratio of solvent, electrode material, binder and conductive agent. It only needs to be stirred evenly until it becomes a slurry.

[0050] The specific implementation process of the present invention is described in detail below through specific embodiments, taking button-type potassium ion batteries as an example.

[0051] Example 1

[0052] (1) Preparation of electrolyte: In a glove box with water and oxygen content less than 1 ppm, 438.5 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using an analytical balance and dissolved in 1 mL of triethyl phosphate (TEP) solvent. The solution was fully dissolved using electromagnetic stirring and allowed to stand for 2 hours to prepare a 2 mol / L KFSI / TEP solution.

[0053] (2) Add 1 mL of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) diluent to 1 mL of the 2 mol / L KFSI / TEP solution prepared in (1) above, mix thoroughly using electromagnetic stirring, and let stand for 12 hours to prepare a 1 mol / L KFSI / TEP / TTE electrolyte.

[0054] Example 2

[0055] (1) Preparation of positive electrode sheet: Prussian blue analog (K2Mn[Fe(CN)6]) was used as the positive electrode active material, mixed with Ketjen black and PVDF in a mass ratio of 8:1:1, added with NMP, stirred evenly, and coated on an aluminum foil current collector. After vacuum drying at 80°C for 12 hours, the positive electrode sheet was obtained.

[0056] (2) Preparation of half-cell: With potassium metal as the counter electrode and reference electrode and glass fiber as the separator, in a glove box with water and oxygen content less than 0.1 ppm, assemble the negative electrode shell, spring, gasket, potassium metal, electrolyte, separator, electrolyte, positive electrode sheet, gasket, and positive electrode shell in the order of button cell, and finally compact with a button cell sealing machine. After assembly, let it stand for 8 hours and perform constant current charge and discharge test at room temperature.

[0057] The electrolyte prepared in Example 1 was 1 mol L -1 KFSI / TEP / TTE, constant current charge and discharge test of the assembled K2Mn[Fe(CN)6] half-cell. K2Mn[Fe(CN)6] positive electrode at 15.5mA g -1 At the current density, the first week coulombic efficiency is 74.89% and the reversible specific capacity is 115.15 mAh g -1 At 75mA g -1 At the current density, the capacity retention rate is 94.2% after 500 cycles.

[0058] Example 3

[0059] (1) Preparation of negative electrode sheet: Commercial graphite is used as the active material, mixed with CMC at a mass ratio of 95:5, added with water and stirred evenly, coated on the aluminum foil current collector, and vacuum dried at 80°C to obtain the negative electrode sheet. Then, potassium metal is used as the counter electrode and glass fiber is used as the separator. The button cells are assembled in sequence in an argon glove box, and finally compacted using a button cell sealing machine. After assembly, the cells are left to stand for 4 hours, and constant current charge and discharge tests are performed at room temperature.

[0060] The electrolyte prepared in Example 1 was 1 mol L -1 KFSI / TEP / TTE, constant current charge and discharge test of the assembled graphite half-cell. The graphite negative electrode is at 27.9mA g -1 At the current density, the first week coulombic efficiency is 87% and the reversible specific capacity is 260 mAh g -1 , close to the theoretical specific capacity of graphite 279 mAh g -1 At 27.9 mA g -1 At the same current density, the capacity retention rate was 95.7% after 300 cycles.

[0061] Example 4

[0062] (1) Preparation of electrode sheet: The positive electrode sheet was prepared by the method of step (1) of Example 2. The negative electrode sheet was prepared by the method of step (1) of Example 3.

[0063] (2) Preparation of potassium ion battery: Using glass fiber as separator, assemble button cells in a glove box with water and oxygen content less than 0.1 ppm in the order of negative electrode shell, spring, gasket, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, gasket, positive electrode shell, and compact with a button cell sealing machine. After assembly, let stand for 4 hours and perform constant current charge and discharge test at room temperature. Figure 6 The battery showed high cycling stability at 75 mA g -1 After 200 cycles at a current density of , the battery capacity retention rate is greater than 90%.

[0064] The electrolyte prepared in Example 1 was 1 mol L -1 KFSI / TEP / TTE, constant current charge and discharge test of the assembled potassium ion full battery. The potassium ion full battery is at 15.5mA g -1 At the current density, the first-week coulombic efficiency is 73.18%, and the reversible specific capacity is 110.8 mAh g -1 At 75mA g -1 At the same current density, the capacity retention rate is 90% after 200 cycles.

[0065] Figure 1 For the use of 1 mol L -1When KFSI / TEP / TTE electrolyte was used, the positive electrode of K2Mn[Fe(CN)6] was 15.5 mA g -1 The charge and discharge curve under the current density, the first week coulomb efficiency is 74.89%, and the reversible specific capacity is 115.15mAhg -1 ;

[0066] Figure 2 For the use of 1 mol L -1 In KFSI / TEP / TTE electrolyte, K2Mn[Fe(CN)6] cathode has a charge capacity of 75 mA g -1 Cyclic stability curve under current density, the capacity retention rate after 500 cycles is 94.2%;

[0067] Figure 3 For the use of 1 mol L -1 When KFSI / TEP / TTE electrolyte is used, the graphite anode is at 27.9 mA g -1 The charge and discharge curves under the current density are shown in Figure 1. The coulombic efficiency in the first cycle is 87% and the reversible specific capacity is 260 mAh g -1 , close to the theoretical specific capacity of graphite 279 mAh g -1 ;

[0068] Figure 4 For the use of 1 mol L -1 When KFSI / TEP / TTE electrolyte is used, the graphite anode is at 27.9 mA g -1 Cyclic stability curve under current density, the capacity retention rate after 300 cycles is 95.7%;

[0069] Figure 5 For the use of 1 mol L -1 KFSI / TEP / TTE electrolytes for potassium ion full battery at 15.5 mA g -1 The first charge-discharge curve at the current density is 73.18% coulombic efficiency and 110.8 mAh g -1 ;

[0070] Figure 6 For the use of 1 mol L -1 KFSI / TEP / TTE electrolytes for potassium ion full cells at 75 mA g -1 Cyclic stability curve under current density, the capacity retention rate is 90% after 200 cycles.

[0071] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a non-flammable and high-voltage resistant electrolyte, characterized in that: The method comprises the steps of: S1. dissolving a potassium salt solute in a non-flammable solvent in a glove box where the water and oxygen contents are below a certain value, and allowing the solution to stand for 2 hours after the solution is fully dissolved to prepare a mixed solution of the potassium salt solute and the non-flammable phosphate solvent; S2. Add high-voltage resistant additives to the mixed solution, mix thoroughly, and let stand for 12 hours to prepare a non-flammable and high-voltage resistant electrolyte.

2. The preparation method according to claim 1, characterized in that: The potassium salt solute is at least one or more of potassium hexafluorophosphate KPF6, bis(fluorosulfonyl)imide potassium salt KFSI, bis(trifluorosulfonyl)imide potassium salt KTFSI, potassium perchlorate KClO4, potassium nitrate KNO3, and potassium tetrafluoroborate KBF4.

3. The preparation method according to claim 1, characterized in that: The non-flammable solvent is one or more of trimethyl phosphate (TMP), triethyl phosphate (TEP), tripropyl phosphate (TPP), tributyl phosphate (TBP), and tris(2,2,2-trifluoroethyl) phosphate (FTEP).

4. The preparation method according to claim 1, characterized in that: The high-pressure resistant additive is one or more of 1,1,2,3,3,3-hexafluoropropyl methyl ether HM, perfluorobutyl ethyl ether EFE, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether OTE, hexafluoroisopropyl methyl ether HME, 1,1,2,2-tetrafluoroethyl ethyl ether ETE, 1,1,2,2,-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether TTE, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether HFE.

5. The preparation method according to claim 1, characterized in that: The potassium salt solute, the non-flammable organic solvent and the high-pressure resistant additive are all analytically pure, with a purity of ≥99.5% and a water content of less than 1 ppm.

6. A non-flammable and high-voltage resistant electrolyte, characterized in that: The electrolyte is obtained by the preparation method according to any one of claims 1 to 5.

7. A potassium ion battery, characterized in that: The potassium ion battery comprises a negative electrode sheet or potassium metal, the electrolyte according to claim 6, and a separator and a positive electrode sheet arranged therein in sequence.

8. The potassium ion battery according to claim 7, characterized in that The positive electrode sheet preparation process includes: using Prussian blue analogue K2Mn[Fe(CN)6] as the positive electrode active material, mixing it with conductive carbon and binder in a certain mass ratio, adding solvent and stirring evenly, and then coating it on the aluminum foil current collector, and then vacuum drying at 80°C for 12 hours to obtain the positive electrode sheet.

9. The potassium ion battery according to claim 7, characterized in that: The preparation process of the negative electrode sheet includes: using commercial graphite as the active material, mixing it with a binder in a certain mass ratio, adding water and stirring evenly, then coating it on an aluminum foil current collector, and vacuum drying it at 80°C to obtain the negative electrode sheet.

10. The potassium ion battery according to claim 7, characterized in that: The capacity ratio of the negative electrode sheet to the positive electrode sheet is 1.05 to 1.2:1.

Images