A six-membered ring ether-based electrolyte, a preparation method, applications and a potassium ion battery

Abstract

The application provides a six-membered ring ether-based electrolyte, a preparation method, an application and a potassium ion battery, relates to the field of potassium ion batteries, and the six-membered ring ether-based electrolyte comprises an electrolyte potassium salt and an electrolyte solvent, wherein the electrolyte potassium salt comprises one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium bisfluorosulfonylimide, potassium triflate, potassium bis-trifluoromethylsulfonylimide, potassium nitrate and potassium perchlorate; and the electrolyte solvent is a six-membered ring ether. The electrolyte provided by the application solves the problem that the current potassium ion battery electrolyte cannot remain stable at high voltage and low voltage at the same time and continuously decomposes, thereby improving the cycle stability of the potassium ion battery and preparing a potassium ion battery that can maintain high energy density, high capacity retention rate and long cycle life.

Description

[Technical Field]

[0001] This invention relates to the field of potassium-ion battery technology, and in particular to a six-membered ring ether-based electrolyte, its preparation method, its application, and a potassium-ion battery. [Background Technology]

[0002] Alkali metal ion batteries have been widely used in various industries. Among them, lithium-ion batteries, with their high voltage, high energy density, and long cycle life, are commonly used in portable electronic devices (mobile phones, laptops, etc.) and new energy vehicles. However, due to the scarcity and high cost of lithium resources, the price and production volume of lithium-ion batteries are difficult to match with market demand. Therefore, new secondary battery systems such as sodium, potassium, aluminum, and zinc ion batteries have attracted much attention from researchers due to their lower cost. Among these new systems, potassium ion batteries stand out due to their abundant reserves, low cost, low standard electrode potential, and compatibility with graphite anodes.

[0003] However, the cycle stability of potassium-ion batteries has long been a point of contention. Initially, many believed that the poor stability of potassium-ion batteries stemmed from the large size of potassium ions, and that the repeated insertion and extraction of potassium ions into and out of the electrodes during charging and discharging damaged the electrode structure. However, with further research, numerous studies have demonstrated that the Prussian blue analogue cathode and the graphite and hard carbon anode, widely used in potassium-ion batteries, possess extremely strong structural stability; the instability is primarily attributed to the electrolyte.

[0004] Electrolyte is a crucial component of batteries, decisively influencing their performance and cost. Currently, the market demands increasingly higher energy density and longer lifespan for batteries. Alkali metal ion batteries, with their high operating voltage, possess inherently high energy density. Potassium ion batteries utilize Prussian white cathodes with operating voltages exceeding 4.0V, while commonly used graphite and hard carbon anodes operate below 0.4V. This significant voltage difference between the positive and negative electrode materials places high demands on the electrochemical stability of the electrolyte.

[0005] Since commonly used carbon, silicon, and metal anodes mostly undergo significant volume expansion during cycling, the solid electrolyte interface (SEI) on the anode surface will repeatedly deform. If the SEI breaks, the exposed anode surface will experience electrolyte decomposition to form a new SEI, leading to electrolyte consumption and capacity decay.

[0006] Traditional commercial carbonate electrolytes suffer from poor reduction stability and the inability of their derived organic-dominated SEI to effectively passivate the negative electrode surface, leading to continuous decomposition on the negative electrode side and resulting in low coulombic efficiency, a significant factor in battery capacity decay. Ether-based electrolytes exhibit good reduction stability, but most show poor oxidation stability and pose a risk of solvent molecules co-intercalating with metal cations. Ether molecules can be classified into linear and cyclic ethers based on their molecular structure, with typical examples being 1,2-dimethoxyethane (DME) and 1,3-dioxopentane (DOL). Compared to linear ethers, cyclic ethers often have weaker binding energies with alkali metal ions. Benefiting from this characteristic, cyclic ethers have been repeatedly used in research on lithium-ion and sodium-ion battery electrolytes, but are not yet widely used in potassium-ion battery electrolyte research.

[0007] Therefore, it is necessary to study a six-membered ring ether-based electrolyte, its preparation method, its application, and a potassium-ion battery to address the shortcomings of existing technologies and solve or mitigate one or more of the aforementioned problems. [Summary of the Invention]

[0008] In view of this, the present invention provides a six-membered ring ether-based electrolyte, a preparation method, an application, and a potassium-ion battery. By providing an electrolyte adapted to high-voltage potassium-ion batteries, this electrolyte improves the reduction stability of the electrolyte on the negative electrode side by selecting cyclic ethers as solvents, and further restricts the cyclic ethers to six-membered rings with larger molecular sizes. By regulating the molecular structure, the high-voltage stability of the ether electrolyte is improved and the ion-solvent co-intercalation is suppressed.

[0009] The electrolyte of this invention solves the problem that current potassium-ion battery electrolytes cannot remain stable and continuously decompose under both high and low voltages, thereby improving the cycle stability of potassium-ion batteries and enabling the preparation of potassium-ion batteries that can maintain high energy density, high capacity retention and long cycle life.

[0010] On one hand, the present invention provides a six-membered ring ether-based electrolyte, wherein the six-membered ring ether-based electrolyte comprises an electrolyte potassium salt and an electrolyte solvent, wherein:

[0011] The electrolyte potassium salt includes one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium difluorosulfonyl imide, potassium trifluoromethanesulfonate, potassium difluoromethanesulfonyl imide, potassium nitrate, and potassium perchlorate;

[0012] The electrolyte solvent is a six-membered cyclic ether.

[0013] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the six-membered cyclic ether comprises one or more of 1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane, tetrahydropyran, 2-methyltetrahydropyran, and 4-methyltetrahydropyran.

[0014] In accordance with the aspects and any possible implementations described above, a method for preparing a six-membered ring ether-based electrolyte is further provided, the method comprising the following steps:

[0015] S1: Weigh the electrolyte potassium salt and the six-membered cyclic ether according to the preset amount;

[0016] S2: Dissolve the potassium salt of electrolyte in a six-membered cyclic ether;

[0017] S3: Stir and let stand to obtain a six-membered ring ether electrolyte.

[0018] In addition to the aspects and any possible implementations described above, an implementation is further provided in which the stirring method in S3 includes, but is not limited to, electromagnetic stirring.

[0019] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the settling time in S3 is 3-5 hours.

[0020] In accordance with the aspects and any possible implementations described above, an application of a six-membered ring ether-based electrolyte is further provided, characterized in that the application specifically involves adapting the six-membered ring ether-based electrolyte to a high-voltage potassium-ion battery, and using the six-membered ring ether-based electrolyte as the electrolyte for the high-voltage potassium-ion battery.

[0021] In accordance with the aspects described above and any possible implementation thereof, a potassium-ion battery is further provided, the potassium-ion battery comprising a positive electrode material, a negative electrode material and the aforementioned six-membered ring ether-based electrolyte, wherein the positive electrode material is connected to the negative electrode material via the aforementioned six-membered ring ether-based electrolyte.

[0022] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the potassium-ion battery improves the reducing stability of the electrolyte on the negative electrode side by selecting a cyclic ether as a solvent, and further restricts the cyclic ether to a six-membered ring with a larger molecular size, thereby improving the high-voltage stability of the ether electrolyte and suppressing ion-solvent co-intercalation by regulating the molecular structure.

[0023] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the positive electrode material is a Prussian blue analogue and the negative electrode material is graphite or hard carbon.

[0024] In addition to the aspects and any possible implementations described above, an implementation is further provided in which the potassium-ion battery is a full cell or a half cell, specifically a button cell, a pouch cell, or a cylindrical cell.

[0025] Compared with the prior art, the present invention can achieve the following technical effects:

[0026] 1) This invention is low in cost, easy to prepare, and has good oxidation and reduction stability, and does not undergo significant continuous decomposition below 4.5V;

[0027] 2) In the electrolyte of this invention, the graphite anode can exhibit a specific capacity close to the theory, a high initial coulombic efficiency and excellent cycle stability, and the cathode also exhibits a high initial coulombic efficiency. In the full cell system composed of the two, it also exhibits good potassium storage performance and excellent cycle stability, with a high capacity retention rate.

[0028] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time. [Attached Image Description]

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 To use 1.5 mol L in Comparative Example 1 -1 Linear sweep voltammetry curves of KFSI / EC / DEC electrolyte;

[0031] Figure 2 To use 1.5 mol L in Comparative Example 2 -1 Linear sweep voltammetry curves of KFSI / DOL electrolyte;

[0032] Figure 3 To use the 1.5 mol L in Example 1 -1 Linear sweep voltammetry curves of KFSI / 1,3-DX electrolyte;

[0033] Figure 4 To use 1.5 mol L in Comparative Example 1 -1 The graphite anode in KFSI / EC / DEC electrolyte operates at 27.9 mA g. -1 First charge-discharge curves at current density;

[0034] Figure 5To use the 1.5 mol L in Example 1 -1 The graphite anode in KFSI / DOL electrolyte operates at 27.9 mA g. -1 First charge-discharge curves at current density;

[0035] Figure 6 To use the 1.5 mol L in Example 1 -1 The graphite anode in KFSI / 1,3-DX electrolyte operates at 27.9 mA g. -1 First charge-discharge curves at current density;

[0036] Figure 7 To use the 1.5 mol L in Example 1 -1 The graphite anode in KFSI / 1,3-DX electrolyte operates at 27.9 mA g. -1 Cyclic stability plot at current density;

[0037] Figure 8 To use 1.5 mol L in Comparative Example 1 -1 In KFSI / EC / DEC electrolyte, the K2Mn[Fe(CN)6] cathode has an ampere up to 15.5 mA g in this electrolyte. -1 Charge-discharge curves at current density;

[0038] Figure 9 To use the 1.5 mol L in Example 1 -1 In KFSI / 1,3-DX electrolyte, the K2Mn[Fe(CN)6] cathode achieves an ampere up to 15.5 mA g in this electrolyte. -1 Charge-discharge curves at current density;

[0039] Figure 10 To use 1.5 mol L in Comparative Example 1 -1 When KFSI / 1,3-DX electrolyte is used, the K2Mn[Fe(CN)6] cathode operates at 77.5 mA g. -1 Cyclic stability plot at current density;

[0040] Figure 11 To use 1.5 mol L in Comparative Example 1 -1 Potassium-ion full cells with KFSI / 1,3-DX electrolyte achieve 15.5 mAg. -1 Charge-discharge curves at current density;

[0041] Figure 12 To use 1.5 mol L in Comparative Example 1 -1 Potassium-ion full cells with KFSI / EC / DEC electrolytes operate at 310 mA g. -1 Cyclic stability plot at current density;

[0042] Figure 13 To use the 1.5 mol L in Example 1 -1 A potassium-ion full cell with KFSI / 1,3-DX electrolyte at 310 mA g -1 Cyclic stability plot at current density.

Detailed Implementation Methods

[0043] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0046] This invention provides a six-membered ring ether-based electrolyte, wherein the six-membered ring ether-based electrolyte comprises an electrolyte potassium salt and an electrolyte solvent, wherein:

[0047] The electrolyte potassium salt includes one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium difluorosulfonyl imide, potassium trifluoromethanesulfonate, potassium difluoromethanesulfonyl imide, potassium nitrate, and potassium perchlorate;

[0048] The electrolyte solvent is a six-membered cyclic ether.

[0049] The six-membered cyclic ether includes one or more of 1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane, tetrahydropyran, 2-methyltetrahydropyran, and 4-methyltetrahydropyran.

[0050] This invention also provides a method for preparing a six-membered ring ether-based electrolyte, the method comprising the following steps:

[0051] S1: Weigh the electrolyte potassium salt and the six-membered cyclic ether according to the preset amount;

[0052] S2: Dissolve the potassium salt of electrolyte in a six-membered cyclic ether;

[0053] S3: Stir and let stand to obtain a six-membered ring ether electrolyte.

[0054] The stirring method in S3 includes, but is not limited to, electromagnetic stirring.

[0055] The settling time in S3 is 3-5 hours.

[0056] This invention provides an application of a six-membered ring ether-based electrolyte, specifically: adapting the six-membered ring ether-based electrolyte to a high-voltage potassium-ion battery, and using the six-membered ring ether-based electrolyte as the electrolyte for the high-voltage potassium-ion battery.

[0057] The present invention also provides a potassium-ion battery, the potassium-ion battery comprising a positive electrode material, a negative electrode material and the aforementioned six-membered ring ether-based electrolyte, the positive electrode material being connected to the negative electrode material via the aforementioned six-membered ring ether-based electrolyte, the potassium-ion battery improving the reducing stability of the electrolyte on the negative electrode side by selecting cyclic ether as a solvent, and further restricting the cyclic ether to a larger molecular size six-membered ring, thereby improving the high-voltage stability of the ether electrolyte and suppressing ion-solvent co-intercalation by regulating the molecular structure.

[0058] The potassium-ion battery is either a full cell or a half cell.

[0059] The positive electrode material is a Prussian blue analogue, and the negative electrode material is graphite or hard carbon.

[0060] The potassium-ion battery specifically refers to a button cell, a pouch cell, or a cylindrical cell.

[0061] In practice, all electrochemical tests in this invention are performed at room temperature.

[0062] In specific implementation, preferably, the positive electrode active material in the positive electrode sheet is selected from one of the Prussian blue analogues, accounting for 50 wt.% to 96 wt.% by mass, and the total mass percentage (by mass) of conductive carbon and binder in the positive electrode sheet is 4 wt.% to 50 wt.%. This ensures that the sum of the mass ratios of conductive carbon, binder, and positive electrode active material is 1. The loading of the positive electrode active material can be controlled at 0.1 mg / cm³. -2 ~50mg cm -2 scope.

[0063] In specific implementation, preferably, the negative electrode active material in the negative electrode sheet is a carbon-based negative electrode, including graphite, hard carbon, etc., accounting for 60wt.% to 96wt.% by mass. The total mass percentage (by mass) of conductive carbon and binder in the negative electrode sheet is 4wt.% to 40wt.%. This ensures that the sum of the mass ratios of conductive carbon, binder, and negative electrode active material is 1. The loading of the negative electrode active material can be controlled at 0.1 mg / cm³. -2 ~30mg cm -2 scope.

[0064] In specific implementation, in the potassium-ion battery provided by the present invention, the capacity ratio of the negative electrode and the positive electrode can be controlled in the range of 1.01:1 to 1.2:1.

[0065] In practice, the conductive carbon used in the positive and negative electrode sheets can be one or more of acetylene black, Ketjen black, carbon nanotubes, and graphene. The positive and negative electrode sheets can use the same type of conductive carbon or two different types of conductive carbon; no limitation is made here.

[0066] In practice, the binder used in the positive electrode is either polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), and the current collector is aluminum foil.

[0067] In specific implementation, the binder used in the negative electrode sheet is one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) emulsion, or sodium alginate, and the current collector is aluminum foil.

[0068] In specific implementations, the electrolyte comprises a potassium salt and an organic solvent. The potassium salt in the electrolyte comprises one or more of potassium hexafluorophosphate (KPF6), potassium bis(fluorosulfonyl)imide (KFSI), potassium trifluoromethanesulfonate (KCF3SO3), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), and potassium nitrate (KNO3). Preferably, the salt concentration is 0.5 mol / L. -1 ~3mol L -1 The electrolyte solvent is a cyclic ether selected from one or more of 1,3-dioxane (1,3-DX), 1,4-dioxane (1,4-DX), tetrahydropyran (THP), 2-methyltetrahydropyran (2-MeTHP), and 4-methyltetrahydropyran (4-MeTHP).

[0069] In practical implementation, the potassium-ion battery separator can be selected from one of the following: polyolefins such as polyethylene (PE) and polypropylene (PP), polyvinylidene fluoride (PVDF), polyimide (PI), and glass fiber.

[0070] It should be noted that the potassium-ion battery provided by this invention can be a button-type potassium-ion battery, or it can be a pouch-type potassium-ion battery or a cylindrical potassium-ion battery, and there is no limitation on it here.

[0071] In specific implementation, when the binder used in the battery electrode is polyvinylidene fluoride (PVDF), the solvent used to prepare the slurry is N-methylpyrrolidone (NMP); when the binder used in the electrode is polytetrafluoroethylene (PTFE), the solvent used to prepare the slurry is ethanol; when the binder used in the electrode is sodium carboxymethyl cellulose (CMC), the solvent used to prepare the slurry is water; and when the binder used in the electrode is sodium alginate, the solvent used to prepare the slurry is water.

[0072] It should be noted that there is no fixed ratio for mixing the solvent with the electrode material, binder, and conductive agent during the preparation of the electrode slurry; it is sufficient as long as the mixture is stirred evenly and forms a slurry-like consistency.

[0073] The following detailed description of the specific implementation process of the present invention will be provided through specific embodiments, taking the preparation of a coin-type potassium-ion battery as an example.

[0074] Comparative Example 1

[0075] (1) Electrolyte preparation: The following operations were performed in an argon-atmospheric glove box. 328.8 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using a balance and dissolved in 1 ml of a 1:1 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The solution was stirred electromagnetically until fully dissolved and allowed to stand for 4 hours to prepare a solution with a concentration of 1.5 mol / L. -1 Electrolytes for KFSI / EC / DEC.

[0076] (2) A button cell containing the above electrolyte was tested using a potassium metal reference electrode and a glass fiber diaphragm. The electrochemical oxidation stability of the electrolyte was tested using a linear sweep voltammetry method at a scan rate of 1 mV / s. -1 .

[0077] Comparative Example 2

[0078] (1) Electrolyte preparation: The following operations were performed in an argon-atmospheric glove box. 328.8 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using a balance and dissolved in 1 ml of 1,3-dioxane (DOL). The solution was stirred electromagnetically until fully dissolved, and allowed to stand for 4 hours to prepare a solution with a concentration of 1.5 mol / L. -1 KFSI / DOL electrolyte.

[0079] (2) A button cell containing the above electrolyte was tested using a potassium metal reference electrode and a glass fiber diaphragm. The electrochemical oxidation stability of the electrolyte was tested using a linear sweep voltammetry method at a scan rate of 1 mV / s. -1 .

[0080] Example 1

[0081] (1) Electrolyte preparation: The following operations were performed in an argon-atmospheric glove box. 328.8 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using a balance and dissolved in 1 mL of 1,3-dioxane (1,3-DX). The solution was stirred magnetically until fully dissolved, and allowed to stand for 4 hours to prepare a solution with a concentration of 1.5 mol / L. -1 KFSI / 1,3-DX electrolyte.

[0082] (2) A button cell containing the above electrolyte was tested using a potassium metal reference electrode and a glass fiber diaphragm. The electrochemical oxidation stability of the electrolyte was tested using a linear sweep voltammetry method at a scan rate of 1 mV / s. -1 .

[0083] Comparative Example 1 is a commonly used potassium-ion battery electrolyte system, Comparative Example 2 is a commonly used five-membered ring ether-based electrolyte system, and Example 1 is an optimized electrolyte design. The comparison of the three better illustrates the differences in electrochemical performance.

[0084] Example 2

[0085] Negative electrode preparation: Commercial graphite was used as the active material. Sodium carboxymethyl cellulose (CMC), the negative electrode active material, was mixed with water at a mass ratio of 95:5. After thorough mixing, the mixture was uniformly coated onto an aluminum foil current collector and vacuum dried at 80°C to obtain the negative electrode sheet. Using potassium metal as the counter electrode and glass fiber as the separator, coin cells were assembled in a glove box with water and oxygen contents both below 0.1 ppm, following the sequence of negative electrode shell, spring, gasket, potassium metal, electrolyte, separator, negative electrode sheet, gasket, and positive electrode shell. After assembly, the cells were compacted using a coin cell sealing machine for subsequent testing. After assembly, the cells were allowed to stand for 4 hours, and then constant current charge-discharge tests were performed at room temperature using a battery testing system.

[0086] Example 3

[0087] (1) Preparation of positive electrode sheet: Prussian blue analogue (K2Mn[Fe(CN)6]) was used as positive electrode active material. The positive electrode active material, conductive carbon Ketjen black and binder PVDF were mixed in a mass ratio of 8:1:1. After adding N-methylpyrrolidone (NMP) and stirring evenly, the mixture was uniformly coated on aluminum foil current collector and vacuum dried at 80°C to obtain the positive electrode sheet.

[0088] (2) Half-cell preparation: Using potassium metal as the counter electrode and glass fiber as the separator, coin cells were assembled in a glove box with water and oxygen contents both below 0.1 ppm in the following order: negative electrode shell, spring, gasket, potassium metal, electrolyte, separator, electrolyte, negative electrode sheet, gasket, and positive electrode shell. After assembly, the cells were compacted using a coin cell sealing machine for subsequent testing. After assembly, the cells were left to stand for 4 hours, and then constant current charge-discharge tests were performed at room temperature using a battery testing system.

[0089] Example 4

[0090] (1) Preparation of negative electrode sheet: The negative electrode sheet was prepared using the method in step (1) of Example 1.

[0091] (2) Preparation of positive electrode: The negative electrode was prepared using the method in step (1) of Example 2.

[0092] (3) Potassium-ion battery preparation: Using glass fiber as the separator, button cells were assembled in a glove box with water and oxygen content both below 0.1 ppm in the following order: negative electrode shell, spring, gasket, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, gasket, and positive electrode shell. After assembly, the batteries were compacted using a button cell sealing machine for subsequent testing. After assembly, the batteries were left to stand for 4 hours, and then constant current charge-discharge tests were performed at room temperature using a battery testing system. Figure 7 The battery demonstrated its cycle stability at 310 mA g. -1 After 2000 cycles at the specified current density, the charge / discharge capacity retention rate is 71.01%.

[0093] Based on the above Examples 1-4 and Comparative Example 1, as shown... Figures 1-13 As shown, where Figure 1 It is 1.5 mol L -1 Linear sweep voltammetry curves of KFSI / EC / DEC electrolyte. Figure 2 It is 1.5 mol L -1 Linear sweep voltammetry curves of KFSI / DOL electrolyte. Figure 3 It is 1.5 mol L -1 Linear sweep voltammetry curves of KFSI / 1,3-DX electrolyte, with oxidation potentials higher than 1.5 mol / L. -1 KFSI / EC / DEC electrolyte and 1.5 mol L -1 KFSI / DOL electrolyte. Figure 4 It is 1.5 mol L -1 The initial charge-discharge curves of the graphite anode in KFSI / EC / DEC electrolyte show a coulombic efficiency of 79.64% and a reversible specific capacity of 256.6 mAh g⁻¹. -1 . Figure 5 It is 1.5 mol L-1 The initial charge-discharge curves of the graphite anode in KFSI / DOL electrolyte show a coulombic efficiency of 54.56% and a reversible specific capacity of 121.5 mAh g⁻¹. -1 . Figure 6 It is 1.5 mol L -1 The initial charge-discharge curves of the graphite anode in KFSI / 1,3-DX electrolyte showed a coulombic efficiency of 90.70% and a reversible specific capacity of 267.8 mAh g⁻¹. -1 . Figure 7 It is 1.5 mol L -1 The graphite anode in KFSI / 1,3-DX electrolyte at a current density of 27.9 mA g -1 The cycle stability curve shows that the capacity retention rate is 95% after 120 cycles. Figure 8 It is 1.5 mol L -1 In KFSI / EC / DEC electrolyte, the K2Mn[Fe(CN)6] cathode is subjected to a current density of 15.5 mA g. -1 The initial charge-discharge curves showed a coulombic efficiency of 80.57% and a reversible specific capacity of 125.9 mAh g. -1 . Figure 9 It is 1.5 mol L -1 In KFSI / 1,3-DX electrolyte, the K2Mn[Fe(CN)6] cathode is subjected to a current density of 15.5 mA g. -1 The initial charge-discharge curves showed a coulombic efficiency of 84.05% and a reversible specific capacity of 132.3 mAh g⁻¹. -1 . Figure 10 It is 1.5 mol L -1 KFSI / 1,3-DX electrolyte K2Mn[Fe(CN)6] cathode at a current density of 155 mA g -1 The cycle stability curve shows that the capacity retention rate is 83.78% after 300 cycles. Figure 11 It is 1.5 mol L -1 A potassium-ion full cell in KFSI / 1,3-DX electrolyte at a current density of 15.5 mA g -1 The charge-discharge curves show a coulombic efficiency of 74.39% and a reversible specific capacity of 125.8 mAh g. -1 . Figure 12 It is 1.5 mol L - 1 Potassium-ion full cells in KFSI / EC / DEC electrolyte at a current density of 310 mA g -1 The charge-discharge curves show that the capacity retention rate is 57.59% after 2000 cycles. Figure 13 It is 1.5 mol L -1A potassium-ion full cell in KFSI / 1,3-DX electrolyte at a current density of 310 mA g -1 The charge-discharge curves show that the capacity retention rate is 71.01% after 2000 cycles.

[0094] In Example 1, 1.5 mol L -1 In KFSI / 1,3-DX electrolyte, the graphite anode can exhibit a specific capacity close to the theoretical value (267.8 mAh g). -1 It exhibits high initial coulombic efficiency (90.70%) and excellent cycling stability at 27.9 mA g. -1 The K2Mn[Fe(CN)6] cathode exhibited a stable capacity retention of over 95% after 120 cycles at a current density of 310 mA g. It also demonstrated an initial coulombic efficiency of 84.05%. In the full cell system composed of both electrodes, it exhibited excellent potassium storage performance and outstanding cycle stability at 310 mA g. -1 The specific capacity at the given current density is 75.2 mAh g. -1 After 2000 cycles, the capacity retention was 71.01%. In Comparative Example 1, which represents a traditional carbonate electrolyte, 1.5 mol L... -1 In KFSI / EC / DEC electrolyte, the specific capacity and initial coulombic efficiency of the graphite anode are only 256.6 mAh g. -1 The initial coulombic efficiency of the K2Mn[Fe(CN)6] cathode was 80.57%, and the specific capacity of the potassium-ion full cell at the same current density was 63.9 mAh g. -1 After 2000 cycles, the capacity retention was 57.59%. In Comparative Example 2, representing a conventional ether-based electrolyte and a five-membered ring ether electrolyte, 1.5 mol L... -1 In KFSI / DOL electrolyte, the graphite anode can only provide 121.5 mAh g. -1 It has a specific capacity and a first coulomb efficiency of 54.56%.

[0095] The foregoing has provided a detailed description of a six-membered ring ether-based electrolyte, its preparation method, its application, and a potassium-ion battery, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the methods and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0096] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0097] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0098] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0099] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A six-membered ring ether-based electrolyte, characterized in that, The six-membered ring ether-based electrolyte comprises an electrolyte potassium salt and an electrolyte solvent, wherein: The electrolyte potassium salt includes one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium difluorosulfonyl imide, potassium trifluoromethanesulfonate, potassium difluoromethanesulfonyl imide, potassium nitrate, and potassium perchlorate; The electrolyte solvent is a fluorine-free six-membered cyclic ether; The fluorine-free six-membered cyclic ether includes one or more of 1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane, tetrahydropyran, 2-methyltetrahydropyran, and 4-methyltetrahydropyran.

2. A method for preparing a six-membered ring ether-based electrolyte, used to prepare the six-membered ring ether-based electrolyte of claim 1, characterized in that, The preparation method includes the following steps: S1: Weigh the electrolyte potassium salt and the six-membered cyclic ether according to the preset amount; S2: Dissolve the potassium salt of electrolyte in a six-membered cyclic ether; S3: Stir and let stand to obtain a six-membered ring ether electrolyte.

3. The preparation method according to claim 2, characterized in that, The stirring method in S3 includes, but is not limited to, electromagnetic stirring.

4. The preparation method according to claim 2, characterized in that, The settling time in S3 is 3-5 hours.

5. An application of a six-membered ring ether-based electrolyte, characterized in that, The specific application is as follows: adapting the six-membered ring ether-based electrolyte of claim 1 to a high-voltage potassium-ion battery, and using the six-membered ring ether-based electrolyte as the electrolyte of the high-voltage potassium-ion battery.

6. A potassium-ion battery, characterized in that, The potassium-ion battery includes a positive electrode material, a negative electrode material, and a six-membered ring ether-based electrolyte as described in claim 1, wherein the positive electrode material is connected to the negative electrode material through the six-membered ring ether-based electrolyte.

7. The potassium-ion battery according to claim 6, characterized in that, The potassium-ion battery improves the reduction stability of the electrolyte on the negative electrode side by selecting cyclic ethers as solvents. At the same time, it further restricts the cyclic ethers to large-molecule six-membered rings, thereby improving the high-voltage stability of the ether electrolyte and suppressing ion-solvent co-intercalation by regulating the molecular structure.

8. The potassium-ion battery according to claim 6, characterized in that, The positive electrode material is a Prussian blue analogue, and the negative electrode material is graphite or hard carbon.

9. The potassium-ion battery according to claim 6, characterized in that, The potassium-ion battery is a full cell or a half cell, specifically a button cell, a pouch cell, or a cylindrical cell.

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