Six-membered ring ether-based electrolyte, preparation method, application and potassium ion battery

Abstract

The invention provides a six-membered ring ether-based electrolyte, a preparation method, application and a potassium ion battery, and relates to the field of potassium ion batteries, 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 bis (fluorosulfonyl) imide, potassium trifluoromethanesulfonate, potassium bis (trifluoromethanesulfonyl) imide, potassium nitrate and potassium perchlorate; according to the electrolyte, the problem that the existing potassium ion battery electrolyte cannot be kept stable and continuously decomposed at high voltage and low voltage at the same time is solved, so that the cycling stability of the potassium ion battery is improved, and the potassium ion battery capable of keeping high energy density, high capacity retention rate and long cycle life is prepared.

Description

[Technical field]

[0001] The present invention relates to the technical field of potassium ion batteries, and in particular to a six-membered ring ether-based electrolyte, a preparation method, an 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 have the characteristics of high voltage, high energy density, and long cycle life and have been widely 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 output 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 received a lot of attention from researchers due to their lower costs. Among these new systems, potassium ions stand out with many advantages such as abundant reserves, low cost, low standard electrode potential, and compatibility with graphite negative electrodes.

[0003] However, the cycle stability of potassium-ion batteries has been criticized. At first, many people believed that the poor stability of potassium-ion batteries was due to the large volume of potassium ions. The repeated insertion / extraction of potassium ions into the electrodes during the charge and discharge process destroyed the electrode structure. However, as research deepened, many studies have shown that the Prussian blue analogue positive electrode and graphite and hard carbon negative electrodes widely used in potassium-ion batteries have extremely strong structural stability, and the main cause of instability comes from the electrolyte.

[0004] The electrolyte is an important component of the battery and has a decisive influence on the battery performance and cost. At present, the market's requirements for the energy density and service life of the battery are constantly increasing. The high operating voltage of alkali metal ion batteries gives them a higher energy density. The working voltage of the Prussian white positive electrode in the potassium ion battery is higher than 4.0V, while the working voltage of the commonly used graphite and hard carbon negative electrodes is below 0.4V. The high 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 negative electrodes all have a large volume expansion during the cycle process, the solid electrolyte interface (SEI) on the negative electrode surface will be repeatedly deformed. If the SEI breaks, the electrolyte will decompose on the exposed negative electrode surface to form a new SEI, resulting in electrolyte consumption and capacity attenuation.

[0006] Traditional commercial carbonate electrolytes will continue to decompose on the negative electrode side due to their poor reduction stability and the inability of their derived organic-dominated SEI to effectively passivate the negative electrode surface, resulting in low coulombic efficiency, which is an important factor in battery capacity decay. Ether-based electrolytes have good reduction stability, but most ether-based electrolytes show poor oxidation stability, and there is also a risk of co-embedding of solvent molecules and metal cations. Ether molecules can be divided into linear ethers and cyclic ethers according to their molecular structure, with 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) as typical representatives. Compared with linear ethers, cyclic ethers often have weaker binding energy with alkali metal ions. Thanks to this property, cyclic ethers have been used many times in the research of lithium-ion battery and sodium-ion battery electrolytes, but have not yet been widely used in the research of potassium-ion battery electrolytes.

[0007] Therefore, it is necessary to study a six-membered ring ether-based electrolyte, preparation method, application and potassium ion battery to address the shortcomings of the prior art and to solve or alleviate one or more of the above 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 a high-voltage potassium ion battery, the electrolyte improves the reduction stability of the electrolyte on the negative electrode side by selecting a cyclic ether as a solvent, and further limits the cyclic ether to a six-membered ring with a larger molecular size, thereby improving the high-voltage stability of the ether electrolyte and inhibiting ion-solvent co-embedding by regulating the molecular structure.

[0009] The electrolyte of the present invention solves the problem that the current potassium ion battery electrolyte cannot maintain stability and continuous decomposition at high voltage and low voltage at the same time, 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.

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

[0011] The electrolyte potassium salt includes one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium bis(fluorosulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(trifluoromethanesulfonyl)imide, potassium nitrate and potassium perchlorate;

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

[0013] According to the aspects and any possible implementations described above, an implementation is further provided, wherein 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.

[0014] According to the above aspects and any possible implementation, a method for preparing a six-membered ring ether-based electrolyte is further provided, which is used to prepare the six-membered ring ether-based electrolyte, and the preparation method comprises the following steps:

[0015] S1: Weighing electrolyte potassium salt and six-membered cyclic ether according to preset conditions;

[0016] S2: dissolving electrolyte potassium salt in six-membered cyclic ether;

[0017] S3: Stirring and standing to obtain a six-membered ring ether-based electrolyte.

[0018] As described above, in any possible implementation, there is further provided an implementation, wherein the stirring method in S3 includes but is not limited to electromagnetic stirring.

[0019] According to the above aspects and any possible implementation, an implementation is further provided, wherein the standing time in S3 is 3-5 hours.

[0020] According to the aspects and any possible implementation methods described above, an application of a six-membered ring ether-based electrolyte is further provided, characterized in that the application specifically comprises: 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 of the high-voltage potassium ion battery.

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

[0022] According to the aspects and any possible implementations described above, an implementation is further provided, in which the potassium ion battery improves the reduction stability of the electrolyte on the negative electrode side by selecting a cyclic ether as a solvent, and further limits the cyclic ether to a six-membered ring with a larger molecular size, thereby regulating the molecular structure to improve the high-voltage stability of the ether electrolyte and inhibit ion-solvent co-embedding.

[0023] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the positive electrode material is a Prussian blue analogue, and the negative electrode material is graphite or hard carbon.

[0024] According to the aspects described above and any possible implementation, an implementation is further provided, wherein the potassium ion battery is a full cell or a half cell, and the full cell and / or half cell is specifically a button cell, a soft pack cell or a cylindrical cell.

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

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

[0027] 2) The graphite negative electrode in the electrolyte of the present invention can exhibit a specific capacity close to the theory, a high first coulombic efficiency and excellent cycle stability, and the positive electrode also exhibits a high first coulombic efficiency. In the full battery system composed of the two, it also exhibits good potassium storage performance and excellent cycle stability, and the capacity retention rate is very high.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time.

Brief Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 For the use of 1.5 mol L -1 Linear sweep voltammetry curve of KFSI / EC / DEC electrolyte;

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

[0032] Figure 3 For the use of 1.5 mol L -1 Linear sweep voltammetry curve of KFSI / 1,3-DX electrolyte;

[0033] Figure 4 For the use of 1.5 mol L -1 When KFSI / EC / DEC electrolyte is used, the graphite anode is at 27.9 mA g -1 First charge and discharge curves at current density;

[0034] Figure 5For the use of 1.5 mol L -1 When KFSI / DOL electrolyte is used, the graphite anode is at 27.9 mA g -1 First charge and discharge curves at current density;

[0035] Figure 6 For the use of 1.5 mol L -1 When KFSI / 1,3-DX electrolyte was used, the graphite anode was at 27.9 mA g -1 First charge and discharge curves at current density;

[0036] Figure 7 For the use of 1.5 mol L -1 When KFSI / 1,3-DX electrolyte was used, the graphite anode was at 27.9 mA g -1 Cycling stability diagram at different current densities;

[0037] Figure 8 For the use of 1.5 mol L -1 In KFSI / EC / DEC electrolyte, the K2Mn[Fe(CN)6] cathode has a charge capacity of 15.5 mA g -1 Charge and discharge curves under current density;

[0038] Fig. 9 For the use of 1.5 mol L -1 When the electrolyte is KFSI / 1,3-DX, the K2Mn[Fe(CN)6] cathode has a charge-discharge rate of 15.5 mA g -1 Charge and discharge curves under current density;

[0039] Fig.10 For the use of 1.5 mol L -1 When KFSI / 1,3-DX electrolyte was used, the positive electrode of K2Mn[Fe(CN)6] was 77.5 mA g -1 Cycling stability diagram at different current densities;

[0040] Fig.11 For the use of 1.5 mol L -1 KFSI / 1,3-DX electrolyte potassium ion full battery at 15.5mAg -1 Charge and discharge curves under current density;

[0041] Fig.12 For the use of 1.5 mol L -1 KFSI / EC / DEC electrolyte potassium ion full battery at 310mA g -1 Cycling stability diagram at different current densities;

[0042] Fig.13 For the use of 1.5 mol L -1 KFSI / 1,3-DX electrolyte potassium ion full battery at 310mA g -1 Cycling stability plot at different current densities. [Specific implementation method]

[0043] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0044] It should be clear that the described embodiments 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.

[0045] 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.

[0046] The present invention provides a six-membered ring ether-based electrolyte, which 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 bis(fluorosulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(trifluoromethanesulfonyl)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] The present invention also provides a method for preparing a six-membered ring ether-based electrolyte, which is used to prepare the six-membered ring ether-based electrolyte. The preparation method comprises the following steps:

[0051] S1: Weighing electrolyte potassium salt and six-membered cyclic ether according to preset conditions;

[0052] S2: dissolving electrolyte potassium salt in six-membered cyclic ether;

[0053] S3: Stirring and standing to obtain a six-membered ring ether-based electrolyte.

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

[0055] The standing time in S3 is 3-5h.

[0056] The present invention provides an application of a six-membered ring ether-based electrolyte, and the application specifically comprises: 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 of the high-voltage potassium ion battery.

[0057] The present invention also provides a potassium ion battery, which comprises a positive electrode material, a negative electrode material and the six-membered ring ether-based electrolyte, wherein the positive electrode material is connected to the negative electrode material through the six-membered ring ether-based electrolyte, and the potassium ion battery improves the reduction stability of the electrolyte on the negative electrode side by selecting a cyclic ether as a solvent, and further limits the cyclic ether to a six-membered ring with a larger molecular size, thereby improving the high-voltage stability of the ether electrolyte and inhibiting ion-solvent co-embedding by regulating the molecular structure.

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

[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 is specifically a button battery, a soft pack battery or a cylindrical battery.

[0061] In a specific implementation, all electrochemical tests in the present invention were performed at room temperature.

[0062] In a specific implementation, preferably, the positive electrode active material in the positive electrode sheet is selected from one of the Prussian blue analogs, and the mass ratio is 50wt.% to 96wt.%, and the total mass ratio (mass ratio) of the conductive carbon and the binder in the positive electrode sheet is 4wt.% to 50wt.%. It is ensured that the sum of the mass ratios of the conductive carbon, the binder and the positive electrode active material is 1. The loading amount of the positive electrode active material can be controlled at 0.1mg cm -2 ~50mg cm -2 scope.

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

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

[0065] In a specific implementation, the conductive carbon used in the positive electrode sheet and the negative electrode sheet can be one or more of acetylene black, Ketjen black, carbon nanotubes and graphene. The positive electrode sheet and the negative electrode sheet can use the same conductive carbon or two different conductive carbons, which is not limited here.

[0066] In a specific implementation, the binder used in the positive electrode sheet is one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), and the current collector is selected as aluminum foil.

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

[0068] In a specific implementation, the electrolyte includes a potassium salt and an organic solvent. The electrolyte potassium salt includes 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 ~3 mol 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 a specific implementation, the potassium ion battery separator can be selected from 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 the present invention may be a button-type potassium ion battery, or may also be a soft-pack potassium ion battery and a cylindrical potassium ion battery, which is not limited here.

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

[0072] It should be noted that in the process of preparing electrode slurry, there is no fixed ratio for the mixture of solvent, electrode material, binder and conductive agent, as long as they are stirred evenly to form a slurry.

[0073] The specific implementation process of the present invention is described in detail below through specific embodiments, taking the preparation of button-type potassium ion batteries as an example.

[0074] Comparative Example 1

[0075] (1) Preparation of electrolyte: The following operations were performed in a glove box under an argon atmosphere: 328.8 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using a balance and dissolved in 1 ml of a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1. Electromagnetic stirring was used to fully dissolve the mixture, and the mixture was allowed to stand for 4 hours to prepare a concentration of 1.5 mol L -1 Electrolyte for KFSI / EC / DEC.

[0076] (2) Using potassium metal as the reference electrode and glass fiber as the separator, a button cell loaded with the above electrolyte was used to test the electrochemical oxidation stability of the electrolyte using linear sweep voltammetry at a scan rate of 1 mV s -1 .

[0077] Comparative Example 2

[0078] (1) Preparation of electrolyte: The following operations were performed in a glove box under an argon atmosphere: 328.8 mg of potassium bis(fluorosulfonyl)imide (KFSI) was weighed using a balance and dissolved in 1 ml of 1,3-dioxolane (DOL). Electromagnetic stirring was used to fully dissolve the KFSI and the electrolyte was allowed to stand for 4 hours to prepare a concentration of 1.5 mol L -1 KFSI / DOL electrolyte.

[0079] (2) Using potassium metal as the reference electrode and glass fiber as the separator, a button cell loaded with the above electrolyte was used to test the electrochemical oxidation stability of the electrolyte using linear sweep voltammetry at a scan rate of 1 mV s -1 .

[0080] Example 1

[0081] (1) Preparation of electrolyte: The following operations were performed in a glove box under an argon atmosphere: 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). Electromagnetic stirring was used to fully dissolve the KFSI and the electrolyte was allowed to stand for 4 hours to prepare a concentration of 1.5 mol L -1 KFSI / 1,3-DX electrolyte.

[0082] (2) Using potassium metal as the reference electrode and glass fiber as the separator, a button cell loaded with the above electrolyte was used to test the electrochemical oxidation stability of the electrolyte using linear sweep voltammetry at a scan rate of 1 mV s -1 .

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

[0084] Example 2

[0085] Preparation of negative electrode sheet: Commercial graphite is used as the active material. The negative electrode active material sodium carboxymethyl cellulose (CMC) is mixed in a mass ratio of 95:5, and after adding water and stirring evenly, it is evenly coated on the aluminum foil current collector, and vacuum dried at 80°C to obtain the negative electrode sheet. Potassium metal is used as the counter electrode and glass fiber is used as the diaphragm. In a glove box with water and oxygen content less than 0.1ppm, button cells are assembled in the order of negative electrode shell, shrapnel, gasket, potassium metal, electrolyte, diaphragm, electrolyte, negative electrode sheet, gasket, and positive electrode shell. After assembly, the button battery sealing machine is used to compact the battery for subsequent testing. After the battery assembly is completed, it is left to stand for 4 hours, and the constant current charge and discharge test is first performed at room temperature using the battery testing system.

[0086] Example 3

[0087] (1) Preparation of positive electrode sheet: Prussian blue analog (K2Mn[Fe(CN)6]) was used as the 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. N-methylpyrrolidone (NMP) was added and stirred evenly. The mixture was evenly coated on an aluminum foil current collector and vacuum dried at 80°C to obtain a positive electrode sheet.

[0088] (2) Preparation of half-cell: Potassium metal is used as the counter electrode and glass fiber is used as the separator. In a glove box where the water and oxygen content are both less than 0.1 ppm, button cells are assembled in the order of negative electrode shell, spring, gasket, potassium metal, electrolyte, separator, electrolyte, negative electrode sheet, gasket, and positive electrode shell. After assembly, the battery is compacted using a button cell sealing machine for subsequent testing. After the battery is assembled, it is left to stand for 4 hours, and a constant current charge and discharge test is first 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 by the method of step (1) of Example 1.

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

[0092] (3) Preparation of potassium ion battery: Using glass fiber as a separator, a button cell was assembled 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, and positive electrode shell. After assembly, a button cell sealing machine was used to compact the battery for subsequent testing. After the battery was assembled, it was left to stand for 4 hours, and a constant current charge and discharge test was first performed at room temperature using a battery testing system. Figure 7 The battery showed a stable cycling performance at 310 mA g -1 After 2000 cycles at a current density of , the charge-discharge capacity retention rate was 71.01%.

[0093] Through the above Examples 1-4 and Comparative Example 1, Figure 1-Figure 13 As shown, Figure 1 is 1.5 mol L -1 Linear sweep voltammetry curve of KFSI / EC / DEC electrolyte. Figure 2 is 1.5 mol L -1 Linear sweep voltammogram of KFSI / DOL electrolyte. Figure 3 is 1.5 mol L -1 Linear sweep voltammetry curve of KFSI / 1,3-DX electrolyte, oxidation potential is higher than 1.5 molL -1 KFSI / EC / DEC electrolyte and 1.5 mol L -1 KFSI / DOL electrolyte. Figure 4 is 1.5 mol L -1 The first charge-discharge curve of the graphite anode in KFSI / EC / DEC electrolyte, with a coulombic efficiency of 79.64% and a reversible specific capacity of 256.6 mAh g -1 . Figure 5 is 1.5 mol L-1 The first charge-discharge curve of the graphite anode in KFSI / DOL electrolyte, with a coulombic efficiency of 54.56% and a reversible specific capacity of 121.5 mAh g -1 . Figure 6 is 1.5 mol L -1 The first charge-discharge curve of the graphite anode in KFSI / 1,3-DX electrolyte, with a coulombic efficiency of 90.70% and a reversible specific capacity of 267.8 mAh g -1 . Figure 7 is 1.5 mol L -1 The graphite anode in KFSI / 1,3-DX electrolyte was -1 The cycle stability curve below shows that the capacity retention rate is 95% after 120 cycles. Figure 8 is 1.5 mol L -1 The K2Mn[Fe(CN)6] cathode in KFSI / EC / DEC electrolyte was -1 The first charge-discharge curve under the condition of -1 . Fig. 9 is 1.5 mol L -1 The K2Mn[Fe(CN)6] cathode in KFSI / 1,3-DX electrolyte was subjected to a current density of 15.5 mA g -1 The first charge-discharge curve under the condition of -1 . Fig.10 is 1.5 mol L -1 The K2Mn[Fe(CN)6] cathode in KFSI / 1,3-DX electrolyte was -1 The cycling stability curve below shows that the capacity retention rate is 83.78% after 300 cycles. Fig.11 is 1.5 mol L -1 The potassium ion full cell in KFSI / 1,3-DX electrolyte was tested at a current density of 15.5 mA g -1 The charge and discharge curves under the above conditions show a Coulombic efficiency of 74.39% and a reversible specific capacity of 125.8 mAh g -1 . Fig.12 is 1.5 mol L - 1 The potassium ion full cell in KFSI / EC / DEC electrolyte was tested at a current density of 310 mA g -1 The charge and discharge curves show that the capacity retention rate is 57.59% after 2000 cycles. Fig.13 is 1.5 mol L -1The potassium ion full cell in KFSI / 1,3-DX electrolyte was used at a current density of 310 mA g -1 The charge and discharge curve below shows 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 show a specific capacity close to the theoretical value (267.8 mAh g -1 ), high first coulombic efficiency (90.70%) and excellent cycle stability at 27.9 mA g -1 The positive electrode K2Mn[Fe(CN)6] exhibited a first coulombic efficiency of 84.05% and exhibited good potassium storage performance and excellent cycle stability at 310 mA g -1 The specific capacity is 75.2 mAh g -1 After 2000 cycles, the capacity retention rate was 71.01%. -1 In KFSI / EC / DEC electrolyte, the specific capacity and first coulombic efficiency of the graphite anode are only 256.6 mAh g -1 and 79.64%, the first coulombic efficiency of the K2Mn[Fe(CN)6] cathode is 80.57%, and the specific capacity of the potassium ion full battery is 63.9 mAh g at the same current density. -1 After 2000 cycles, the capacity retention rate was 57.59%. In Comparative Example 2, which represents a conventional ether-based electrolyte and a pentacyclic ether electrolyte, 1.5 mol L -1 In KFSI / DOL electrolyte, the graphite anode can only provide 121.5 mAh g -1 The specific capacity and the first coulombic efficiency of 54.56% are achieved.

[0095] The above is a detailed introduction to a six-membered ring ether-based electrolyte, preparation method, application and potassium ion battery provided in the embodiments of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application; at the same time, for those of ordinary skill in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0096] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0097] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0098] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0099] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application 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 do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

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 bis(fluorosulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(trifluoromethanesulfonyl)imide, potassium nitrate and potassium perchlorate; The electrolyte solvent is a six-membered cyclic ether.

2. The six-membered ring ether-based electrolyte according to claim 1, characterized in that 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.

3. A method for preparing a six-membered ring ether-based electrolyte, for preparing the six-membered ring ether-based electrolyte according to any one of claims 1-2, characterized in that: The preparation method comprises the following steps: S1: Weighing electrolyte potassium salt and six-membered cyclic ether according to preset conditions; S2: dissolving electrolyte potassium salt in six-membered cyclic ether; S3: Stirring and standing to obtain a six-membered ring ether-based electrolyte.

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

5. The preparation method according to claim 3, characterized in that: The standing time in S3 is 3-5h.

6. An application of a six-membered ring ether-based electrolyte, characterized in that: The application is specifically: adapting the six-membered ring ether-based electrolyte described in any one of claims 1-2 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.

7. A potassium ion battery, characterized in that: The potassium ion battery comprises a positive electrode material, a negative electrode material and the six-membered ring ether-based electrolyte as claimed in any one of claims 1 to 2, wherein the positive electrode material is connected to the negative electrode material through the six-membered ring ether-based electrolyte.

8. The potassium ion battery according to claim 7, characterized in that The potassium ion battery improves the reduction stability of the electrolyte on the negative electrode side by selecting a cyclic ether as a solvent, and further limits the cyclic ether to a six-membered ring with a large molecular size, thereby improving the high-voltage stability of the ether electrolyte and inhibiting ion-solvent co-embedding by regulating the molecular structure.

9. The potassium ion battery according to claim 7, characterized in that: The positive electrode material is a Prussian blue analogue, and the negative electrode material is graphite or hard carbon.

10. The potassium ion battery according to claim 7, characterized in that: The potassium ion battery is a full cell or a half cell, and the full cell and / or half cell is specifically a button cell, a soft pack cell or a cylindrical cell.

Images