5.0 V level high-voltage potassium ion battery ester electrolyte, preparation method and application thereof

Abstract

The application discloses a 5.0 V high-voltage potassium ion battery ester electrolyte and a preparation method and application thereof. The electrolyte comprises an ester solvent, a potassium salt and an additive. The potassium salt is potassium hexafluorophosphate. The additive is lithium difluoro(oxalato)borate. The preparation method comprises the following steps: (1) uniformly mixing the ester solvent to obtain a mixed solvent A; (2) adding KPF6 into the mixed solvent A and uniformly mixing to obtain a premix B; and (3) adding lithium difluoro(oxalato)borate into the premix B, uniformly mixing and standing to obtain the electrolyte. By introducing LiDFOB into the potassium ion battery, the application realizes the transition from 'negative electrode optimization' to '5.0 V positive electrode stability', from'strong solvation' to 'weak solvation film optimization', from'single K + domination' to 'Li + doping enhancement', the electrolyte has an electrochemical stability window of 1.5-5.5 V, realizes 5.0 V, and is not easy to decompose at high voltage.

Description

Technical Field

[0001] This invention belongs to the field of potassium-ion battery technology, and specifically relates to a 5.0 V high-voltage potassium-ion battery ester electrolyte, its preparation method and application. Background Technology

[0002] Potassium-ion batteries, due to their abundant resources and excellent electrochemical performance, have been regarded in recent years as an important supplement or potential alternative to lithium-ion batteries. Potassium accounts for approximately 2.09 wt.% of the Earth's crust, far exceeding that of lithium (0.0017 wt.%), giving it a significant cost advantage; simultaneously, K... + The standard reduction potential of / K (−2.93 V vs. SHE) and Li + The potentials of potassium ions (-3.04 V vs. SHE) are very close to those of Li, and even lower redox potentials can be achieved in some organic electrolytes, which makes it possible to construct high-voltage, high-energy-density battery systems. In addition, potassium ions have weak Lewis acidity, forming smaller solvation structures (smaller than lithium and sodium ions), higher ionic conductivity, and lower desolvation energy, which is beneficial for improving the reaction kinetics at the electrode / electrolyte interface.

[0003] The key limitation to the practical application of potassium-ion batteries is their low energy density, and developing high-voltage cathode materials is one of the core pathways to improve the energy density of potassium-ion batteries. Currently, researchers have developed various cathode materials such as layered oxides, Prussian blue analogs, and polyanionic compounds. Through crystal structure regulation and element substitution, some materials can theoretically achieve voltage plateaus above 4.0 V, even reaching 5.0 V, and possess good potassium-ion insertion / extraction capabilities. However, in actual battery systems, these high-voltage cathode materials often experience rapid performance degradation due to electrolyte oxidation and decomposition, creating a technical dilemma where the material's potential cannot be realized.

[0004] Currently, commonly used electrolyte systems for potassium-ion batteries mainly include carbonate and ether electrolytes. Ether solvents have low viscosity and high ionic conductivity, but their high-voltage resistance is poor. Lei Kaixiang et al. disclosed a high-voltage potassium-ion battery ether electrolyte (CN 116072973A) that can withstand a high voltage of 4.5 V without decomposition, but achieving voltages above 4.5 V is still impractical. Carbonate solvents have a wide electrochemical window and high oxidation stability, making them an ideal choice for matching high-voltage cathodes. However, the operating voltage (5.0 V level) of high-voltage cathode materials such as KVPO4F exceeds the oxidation stability window of traditional carbonate electrolytes, and the cathode electrolyte interface (CEI) film formed on the cathode interface cannot prevent the continuous oxidation and decomposition of the electrolyte, leading to performance degradation. In the existing technology, strategies to improve the high-voltage resistance of potassium-ion battery electrolytes mainly include developing new solvent systems (such as sulfones, nitriles, and ionic liquids) or using high-concentration salt electrolytes. However, all of the above solutions have significant drawbacks. For example, sulfone solvents have high viscosity and low ionic conductivity, nitrile solvents have poor compatibility with the negative electrode, and ionic liquids are too expensive for large-scale application. High-concentration salt electrolytes suffer from poor wettability and high viscosity. In contrast, optimizing existing low-concentration carbonate systems using an additive strategy requires only a small amount of functional additives to achieve high voltage stability without large-scale replacement of the main electrolyte components, offering significant advantages in cost control and process compatibility. However, the CEI film formed by conventional additives (such as FEC and DTD) relied upon by existing carbonate electrolytes cannot inhibit electrolyte decomposition, leading to continuous electrolyte consumption and battery swelling and failure. Therefore, developing novel additives that can preferentially oxidize and decompose at high voltages of 5.0 V to form a dense and stable CEI film is key to overcoming this technological bottleneck. Summary of the Invention

[0005] Objectives of the Invention: The first objective of this invention is to provide a 5.0 V high-voltage potassium-ion battery ester electrolyte, which has a wide electrochemical stability window (1.5–5.5 V) and is not easily decomposed at a high voltage of 5.0 V; the second objective of this invention is to provide a method for preparing the 5.0 V high-voltage potassium-ion battery ester electrolyte; the third objective of this invention is to provide applications of the 5.0 V high-voltage potassium-ion battery ester electrolyte.

[0006] Technical solution: The 5.0 V high-voltage potassium-ion battery ester electrolyte of the present invention is composed of ester solvent, potassium salt and additives; the potassium salt is potassium hexafluorophosphate (KPF6); the additive is lithium difluorooxalate borate (LiDFOB).

[0007] Preferably, the concentration of potassium hexafluorophosphate is 0.5–1.0 mol / L. -1The concentration of lithium difluorooxalate borate is 0.05–0.20 mol / L. -1 .

[0008] Preferably, the ester solvent is a mixture of ethylene carbonate (EC) and propylene carbonate (PC), or diethyl carbonate (DEC) or methyl ethyl carbonate (EMC).

[0009] Preferably, the volume ratio of ethylene carbonate (EC) to propylene carbonate (PC), diethyl carbonate (DEC), or methyl ethyl carbonate is 1:1.

[0010] More preferably, the ester solvent is composed of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1:1.

[0011] The preparation method of the 5.0 V high-voltage potassium-ion battery ester electrolyte of the present invention is characterized by comprising the following steps:

[0012] (1) Mix the ester solvents evenly to obtain mixed solvent A;

[0013] (2) Add KPF6 to mixed solvent A and mix well to obtain premixed solution B;

[0014] (3) Add the additive lithium difluorooxalate borate to the premixed solution B, mix evenly, and let stand to obtain the electrolyte.

[0015] Preferably, in steps (1) to (3), heating can be performed during the mixing process, with the heating temperature being 40 to 60°C. Heating can accelerate the mixing process and obtain a clear electrolyte.

[0016] The application of the electrolyte described in this invention in potassium-ion batteries.

[0017] The potassium-ion battery is either a half-cell or a full-cell battery.

[0018] The potassium-ion battery mentioned is specifically a button cell, a pouch cell, or a cylindrical cell.

[0019] Preferably, the working electrode in the potassium-ion battery half-cell is a polyanionic compound potassium vanadium fluorophosphate (KVPO4F), Prussian white (KMn[Fe(CN)6]), or layered oxide (K 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2), metallic bismuth, and bismuth-tin alloys.

[0020] Preferably, the positive electrode material of the potassium-ion battery is a polyanionic compound KVPO4F; the negative electrode material is a bismuth-tin alloy; and the separator is glass fiber.

[0021] Invention Mechanism:

[0022] This invention applies LiDFOB additive from lithium-ion battery electrolytes to potassium-ion battery ester electrolyte systems. LiDFOB serves as a film-forming additive in both types of batteries, sharing a similar basic function: preferentially decomposing to form a protective interfacial film containing LiF and boron-oxygen species on the electrode surface, inhibiting electrolyte decomposition and side reactions, and capturing HF to reduce electrode corrosion. However, due to the unique electrochemical environment of potassium-ion batteries—a high-voltage cathode at 5.0 V, poor potassium salt stability, and weak potassium ion solvation characteristics—the mechanism of action of LiDFOB has undergone a targeted and differentiated transformation, specifically manifested in the following three core innovations:

[0023] (1) Shift in target: from optimization of the negative electrode solid electrolyte interphase (SEI) membrane to 5.0 V CEI stabilization

[0024] In lithium-ion batteries, the core function of LiDFOB is to optimize the negative electrode SEI film by reducing and decomposing graphite on the surface to generate a protective layer rich in LiF and BO compounds; the optimization of the high-voltage positive electrode interface is only an auxiliary function.

[0025] This invention addresses the high operating voltage of KVPO4F cathodes (up to 4.95 V), which exceeds the oxidation stability range of traditional carbonate electrolytes. Utilizing the significantly higher HOMO level (−7.81 eV) of LiDFOB compared to EC (−8.50 eV), PC (−8.65 eV), and KPF6 (−10.88 eV), LiDFOB preferentially undergoes oxidative decomposition at high cathode voltages, prior to the main electrolyte components, thus constructing a dense CEI film in situ on the cathode surface. This film effectively suppresses side reactions between KVPO4F and the electrolyte (such as transition metal dissolution and electrolyte oxidation gas generation), ensuring cycle stability at high voltages up to 5.0 V. The LiDFOB oxidation potential (approximately 4.2 V) lies precisely before the KVPO4F charging plateau (4.3~4.9 V), ensuring CEI film construction before high potentials for precise protection. The oxidation products possess a wide bandgap, effectively preventing continuous electrolyte oxidation at 5.0 V. Comparative experiments with additives showed that the oxidation products of fluoroethylene carbonate (FEC, oxidation potential approximately 4.0 V) and ethylene sulfate (DTD, oxidation potential approximately 3.8 V) are unstable at 5.0 V and cannot form effective protection, highlighting the irreplaceable nature of LiDFOB in the 5.0 V system.

[0026] (2) Change in operating environment: Optimization of film formation from strong solvation to weak solvation environment

[0027] Lithium ions have strong solvation capabilities, forming a stable solvated sheath layer in the electrolyte. LiDFOB has limited ability to regulate its solvation structure.

[0028] Potassium ions exhibit weaker solvation ability, and this intrinsic difference provides new opportunities for optimizing LiDFOB film formation. This invention discovers that the introduction of LiDFOB can significantly alter the Kc in the weakly solvated environment of potassium-ion batteries. + The solvation structure—from [K(EC)2(PC)2] + Transform into [K(EC)(PC)(DFOB)] + This reduces the number of solvent molecules and lowers the risk of oxidative decomposition. This optimized solvation structure results in a more dense and ordered CEI film formed subsequently on the cathode surface. Meanwhile, DFOB... - The oxidative decomposition products (boron-containing polymers) possess a spatial network structure, which can physically coat the positive electrode active particles to form a composite protective layer, accommodating the large anisotropic volume changes during potassium ion insertion / extraction. This film-forming optimization effect based on a weak solvation environment is not significant in the strongly solvated system of lithium-ion batteries.

[0029] (3) Transformation of film-forming ions: from single K+ ions to film-forming ions. + Dominant towards Li + Doping-enhanced interface construction

[0030] In lithium-ion batteries, the main salt is lithium salt (such as LiPF6), and the interface film is composed of Li... + It consists of dominant decomposition products (LiF, Li2CO3, etc.) and does not require the introduction of other cations.

[0031] In potassium-ion batteries, the main salt is KPF6 (the cation is K). + However, in this invention, LiDFOB is introduced as an additive to introduce Li... + As an "exogenous cation" participating in the formation of CEI in the cathode, Li exhibits unique interface enhancement advantages: + The radius (0.76 Å) is much smaller than K. + (1.38 Å), which makes it easier for LiF to accumulate on the cathode surface and participate in interfacial reactions, forming a stable CEI layer rich in LiF and BO compounds (such as B2O3). LiF has a high Young's modulus, making this LiF more suitable for deposition. + Doped CEI films are better than pure K + The dominant interface film is denser and tougher, and can more effectively suppress oxidation corrosion under high voltage. This "exogenous Li" + The "doping" enhancement mechanism is a unique advantage not found in lithium-ion battery systems.

[0032] In summary, this invention, by introducing LiDFOB into potassium-ion batteries, achieves improvements ranging from "negative electrode optimization" to "5.0 V positive electrode stability," from "strong solvation" to "weak solvation film formation optimization," and from "single K" to "potassium-ion battery." + From "dominant" to "Li" + The three levels of innovation, namely "doping enhancement", together constitute its essential characteristics that distinguish it from lithium-ion batteries in potassium-ion batteries.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention introduces LiDFOB into the electrolyte of potassium ion batteries, which has a wide electrochemical stability window of 1.5 to 5.5 V and is not easily decomposed at a high voltage of 5.0 V; (2) The volume ratio of ester solvent EC:PC is 1:1, and the concentration of LiDFOB added is 0.1 mol L. -1 The best performance is achieved when the electrochemical window reaches 1.5–5.5 V, allowing for stable operation at high voltages. The first-cycle discharge specific capacity is 104.6 mAh g. -1 (0.02 C), the capacity of KVPO4F after 100 cycles is 90.1 mAh g. -1 (0.2 C), capacity retention rate is 97.5%; (3) The preparation method is simple and easy to industrialize. Attached Figure Description

[0034] Figure 1 Linear sweep voltammetry curves of the electrolytes in Comparative Examples 1-4 and Example 1;

[0035] Figure 2 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Comparative Examples 1-4 and Example 1 are shown.

[0036] Figure 3 Linear sweep voltammetry curves of the electrolytes in Examples 1-3;

[0037] Figure 4 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Examples 1-3 are shown.

[0038] Figure 5 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Examples 4, 1, and 5 are shown.

[0039] Figure 6 Linear sweep voltammetry curves of the electrolytes in Comparative Example 1, Example 6, Example 1, Example 7, and Example 8;

[0040] Figure 7The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Comparative Example 1, Example 6, Example 1, Example 7, and Example 8 are shown.

[0041] Figure 8 The graph shows the cycling performance of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Comparative Example 1, Example 6, Example 1, Example 7, and Example 8.

[0042] Figure 9 The rate performance of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Comparative Example 1, Example 6, Example 1, Example 7, and Example 8 is shown in the graph.

[0043] Figure 10 The first charge-discharge curve of the KMn[Fe(CN)6] potassium ion battery cathode material of Example 10 in the electrolyte of Example 1;

[0044] Figure 11 K in Example 11 0.5 Mn 0.8 Ni 0.1 Co 0.1 First charge-discharge curve of O2 potassium ion battery cathode material in electrolyte of Example 1;

[0045] Figure 12 The graph shows the first charge-discharge curve of the bismuth-potassium ion battery anode material of Example 12 in the electrolyte of Example 1.

[0046] Figure 13 The graph shows the first charge-discharge curve of the bismuth-tin alloy potassium-ion battery anode material of Example 13 in the electrolyte of Example 1.

[0047] Figure 14 The graph shows the cycling performance of the bismuth-tin alloy potassium-ion battery anode material of Example 14 in the electrolyte of Example 1.

[0048] Figure 15 The first charge-discharge curve of the KVPO4F / / BiSn potassium-ion full cell assembled with KVPO4F from Example 9 as the positive electrode and BiSn alloy from Example 13 as the negative electrode in the electrolyte of Example 1.

[0049] Figure 16 The graph shows the cycling performance of the KVPO4F / / BiSn potassium-ion full cell assembled using KVPO4F from Example 9 as the positive electrode and BiSn alloy from Example 13 as the negative electrode in the electrolyte of Example 1. Detailed Implementation

[0050] The technical solution of the present invention will be further described below with reference to the embodiments.

[0051] Example 1

[0052] The electrolyte of this invention is prepared by the following method:

[0053] The electrolyte was prepared in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm. 0.5 mL of PC was added to 0.5 mL of EC, and the mixture was stirred at 40 °C for 5 minutes to obtain a mixed solvent. 147.25 mg of KPF6 was weighed using an electronic balance and added to the mixed solvent. The mixture was stirred at 40 °C for 4 hours until homogeneous to obtain a premix. 14.40 mg of LiDFOB was added to the premix, and the mixture was stirred at 40 °C for 4 hours until homogeneous. After stirring was stopped, the mixture was allowed to stand at room temperature (25 °C) for 12 hours to prepare a 0.8 mol / L solution. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0054] Example 2

[0055] Based on Example 1, the solvent PC was replaced with DEC, and all other conditions remained unchanged to prepare a 0.8 mol L solution. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:DEC (V:V, 1:1) electrolyte.

[0056] Example 3

[0057] Based on Example 1, the solvent PC was replaced with EMC, while all other conditions remained unchanged, to prepare a 0.8 mol L solution. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:EMC (V:V, 1:1) electrolyte.

[0058] Example 4

[0059] Based on Example 1, the amount of KPF6 added was changed to 92.05 mg, while other conditions remained unchanged, to prepare a 0.5 mol / L solution. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0060] Example 5

[0061] Based on Example 1, the amount of KPF6 added was changed to 184.06 mg, while other conditions remained unchanged, to prepare a 1.0 mol L solution. -1KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0062] Example 6

[0063] Based on Example 1, the amount of LiDFOB added was changed to 7.20 mg, while other conditions remained unchanged, to prepare a 0.8 mol L solution. -1 KPF6+ 0.05 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0064] Example 7

[0065] Based on Example 1, the amount of LiDFOB added was changed to 21.60 mg, while other conditions remained unchanged, to prepare a 0.8 mol L solution. -1 KPF6+ 0.15 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0066] Example 8

[0067] Based on Example 1, the amount of LiDFOB added was changed to 28.80 mg, while other conditions remained unchanged, to prepare a 0.8 mol L solution. -1 KPF6+ 0.20 mol L -1 LiDFOB / EC:PC (V:V, 1:1) electrolyte.

[0068] Comparative Example 1

[0069] Based on Example 1, without adding LiDFOB, and with all other conditions unchanged, a 0.8 mol L solution was prepared. -1 KPF6 / EC:PC (V:V, 1:1) electrolyte.

[0070] Comparative Example 2

[0071] Based on Example 1, the additive LiDFOB was replaced with 10.61 mg of FEC, while all other conditions remained unchanged, to prepare a 0.8 mol L⁻¹ solution. -1 KPF6+ 0.10 mol L -1 FEC / EC:PC (V:V, 1:1) electrolyte.

[0072] Comparative Example 3

[0073] Based on Example 1, the additive LiDFOB was replaced with 12.40 mg DTD, and all other conditions remained unchanged to prepare a 0.8 mol L⁻¹ solution.-1 KPF6+ 0.10 mol L -1 DTD / EC:PC (V:V, 1:1) electrolyte.

[0074] Comparative Example 4

[0075] Based on Example 1, the additive LiDFOB was replaced with 17.6 mg of potassium difluorooxalate borate (KDFOB), with all other conditions remaining unchanged, to prepare a solution of 0.8 mol / L. -1 KPF6+ 0.10 mol L -1 KDFOB / EC:PC (V:V, 1:1) electrolyte.

[0076] Example 9

[0077] The synthesis steps of KVPO4F are as follows: 0.92 g ammonium dihydrogen phosphate (NH4)H2PO4, 0.936 g ammonium metavanadate (NH4VO3), 0.557 g potassium fluoride (KF), and 1.228 g citric acid (HOC(COOH)(CH2COOH)2) were added sequentially to 30 mL of deionized water. The mixture was stirred at 80 °C for 4 hours. The resulting gel was dried in a vacuum drying oven at 80 °C for 12 hours. The resulting solid was ground in a mortar for 1 hour and then calcined at 700 °C for 8 hours under an argon atmosphere (heating rate of 2 °C / min). -1 KVPO4F was obtained by cooling to room temperature.

[0078] The preparation steps of KVPO4F potassium-ion battery positive electrode sheet are as follows: Synthesized KVPO4F, conductive carbon black (SuperP) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1. After adding an appropriate amount of N-methylpyrrolidone (NMP), the mixture is stirred for 30 minutes at room temperature (25 ℃) using a mixer. The resulting slurry is coated onto aluminum foil and dried in a vacuum drying oven at 100 ℃ for 10 hours. After cooling to room temperature, it is cut into KVPO4F positive electrode sheets with a diameter of 10 mm for later use.

[0079] Example 10

[0080] The synthesis steps of KMnFe(CN)6 are as follows: 7.37 g of potassium ferrocyanide K4Fe(CN)6·3H2O and 3.096 g of manganese chloride MnCl2 mixed powder were ball-milled in a ball mill at a rate of 400 r / min for 10 min. The resulting solid was washed three times by centrifugation with deionized water and ethanol, respectively, to obtain KMnFe(CN)6.

[0081] The preparation steps of KMnFe(CN)6 potassium-ion battery positive electrode sheet are as follows: Synthesized KMnFe(CN)6, conductive carbon black (Super P) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) is added, and the mixture is stirred for 30 minutes at room temperature (25 ℃) using a mixer. The resulting slurry is coated onto aluminum foil and dried in a vacuum drying oven at 120 ℃ for 10 hours. After cooling to room temperature, it is cut into KMnFe(CN)6 positive electrode sheets with a diameter of 10 mm for later use.

[0082] Example 11

[0083] K 0.5 Mn 0.8 Ni 0.1 Co 0.1 The synthesis steps of O2 are as follows: 1.38 g of manganese acetate Mn(CH3COO)2, 0.177 g of nickel acetate Ni(CH3COO)2, 0.177 g of cobalt acetate Co(CH3COO)2, and 0.35 g of potassium carbonate K2CO3 were sequentially added to 50 mL of deionized water and stirred at room temperature (25 °C) for 8 hours. The mixed solution was dried in a forced-air drying oven at 80 °C for 12 hours. The resulting solid was first calcined in a muffle furnace at 350 °C for 2 hours, and then calcined at 800 °C for 10 hours (heating rate of 2 °C / min). -1 ), to obtain layered oxide K 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2.

[0084] K 0.5 Mn 0.8 Ni 0.1 Co 0.1 The preparation steps for the positive electrode of an O2 potassium-ion battery are as follows: The synthesized K... 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) is added, and the mixture is stirred for 30 minutes at room temperature (25 °C) using a mixer. The resulting slurry is coated onto aluminum foil and dried in a vacuum drying oven at 100 °C for 10 hours. After cooling to room temperature, it is cut into K-shaped pieces with a diameter of 10 mm. 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2 positive electrode sheet for use.

[0085] Example 12

[0086] The synthesis steps of metallic Bi are as follows: At room temperature, 150 mg of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 1.5 g of trimesic acid (H3BTC) were sequentially added to 60 mL of ethylene glycol (EG). After sonication for 30 minutes, a homogeneous solution was obtained. The solution was then transferred to a 100 mL polytetrafluoroethylene-lined reactor and dried in a forced-air drying oven at 5 °C for [time missing]. -1 The temperature was increased to 120 °C and held for 12 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The sample was washed three times each with deionized water and ethanol by centrifugation, and then dried in a vacuum oven at 60 °C for 12 h to obtain a white precursor. The precursor was then subjected to an argon atmosphere at 5 °C for 1 min. -1 The temperature was increased to 850 °C and held for 1.5 hours. After natural cooling, a black powder was finally obtained.

[0087] The preparation steps of the negative electrode sheet for metal Bi potassium ion battery are as follows: synthesized metal Bi, conductive carbon black (SuperP) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1. After adding an appropriate amount of N-methylpyrrolidone (NMP), the mixture is stirred for 30 minutes at room temperature (25 ℃) using a mixer. The resulting slurry is coated onto copper foil and dried in a vacuum drying oven at 70 ℃ for 10 hours. After cooling to room temperature, it is cut into metal Bi negative electrode sheets with a diameter of 10 mm for later use.

[0088] Example 13

[0089] The synthesis steps of the BiSn alloy are as follows: At room temperature, 150 mg of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), 29.4 mg of tin tetrachloride (SnCl4), and 1.5 g of trimesic acid (H3BTC) were sequentially dissolved in 60 mL of ethylene glycol (EG). After ultrasonic treatment for 30 minutes, a homogeneous solution was obtained. The solution was transferred to a 100 mL polytetrafluoroethylene-lined reactor and dried in a forced-air drying oven at 5 °C for [time missing]. -1 The temperature was increased to 120 °C and held for 12 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The sample was washed three times each with deionized water and ethanol by centrifugation, and then dried in a vacuum oven at 60 °C for 12 h to obtain a white precursor. The precursor was then subjected to an argon atmosphere at 5 °C for 1 min. -1 The temperature was increased to 850 °C and held for 1.5 hours. After natural cooling, a black powder was finally obtained.

[0090] The preparation steps of BiSn alloy potassium-ion battery negative electrode sheet are as follows: The synthesized BiSn alloy, conductive carbon black (Super P) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1. After adding an appropriate amount of N-methylpyrrolidone (NMP), the mixture is stirred for 30 minutes at room temperature (25 °C) using a mixer. The resulting slurry is coated onto copper foil and dried in a vacuum drying oven at 70 °C for 10 hours. After cooling to room temperature, it is cut into BiSn alloy negative electrode sheets with a diameter of 10 mm for later use.

[0091] Example 14

[0092] The following potassium-ion battery was assembled in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: a potassium metal sheet was used as the reference and counter electrode, aluminum foil as the working electrode, and glass fiber as the separator, using 0.8 mol L⁻¹ as in Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 2 -1 KPF6+ 0.10 mol L -1 FEC / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 3 -1 KPF6+ 0.10 mol L -1 DTD / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 4 -1 KPF6+ 0.10 mol L -1 KDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0093] Linear sweep voltammetry test: On an electrochemical workstation, linear sweep voltammetry was used at 5.0 mV s. -1 The electrochemical windows of the electrolytes in Example 1 and Comparative Examples 1-4 were tested at a specific scan rate. The test results are as follows: Figure 1 As shown.

[0094] Figure 1 The electrolytes of Comparative Examples 1-4 and Example 1 were tested at a scan rate of 5.0 mV / s. -1 Linear sweep voltammetry curves were obtained. By comparing the electrochemical windows of the five electrolytes, the electrolyte of Example 1 exhibited a wider electrochemical stability window, reaching 1.5–5.5 V. This is due to the DFOB... -Optimized solvation structure and Li + Participating in DFOB - The decomposition of the CEI film resulted in a dense, highly antioxidant CEI. Comparative Example 1 had a stability window of 1.6–3.4 V, decomposing above 3.4 V, because no additives were added. Comparative Examples 2 and 3 had stability windows of 1.5–4.0 V and 2.5–3.8 V, respectively, both decomposing above 4.0 V, because the CEI film formed by FEC and DTD is unstable at high voltages. Comparative Example 4 had a stability window of 2.5–5.0 V, decomposing above 5.0 V, because DFOB… - The decomposition products are relatively stable at high voltages below 5.0 V, but due to the absence of Li... + The KDFOB-derived CEI, which participates in the formation of the positive electrode CEI, has a lower stability than that of Example 1. Figure 1 This indicates that the electrolyte containing LiDFOB can operate stably at a high voltage of 5.0 V.

[0095] Example 15

[0096] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing 0.8 mol L⁻¹ of the potassium ion exchange rate from Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+0.10mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 2 -1 KPF6+ 0.10 mol L -1 FEC / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 3 -1 KPF6+ 0.10 mol L -1 DTD / EC:PC (V:V, 1:1) or 0.8 mol L in Comparative Example 4 -1 KPF6+ 0.10 mol L -1 KDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0097] Constant current charge-discharge test: After the above-mentioned KVPO4F potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a LandCT2001A battery testing system at a rate of 0.02 C within a voltage range of 2.0–4.95 V. The test results are as follows. Figure 2 As shown.

[0098] Figure 2 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Examples 1 and Comparative Examples 1-4 are shown at a rate of 0.02 C. The KVPO4F material could not reach the cutoff voltage of 4.95 V in the electrolytes of Comparative Examples 2 and 3, and only after a long period of continuous charging in the electrolyte of Comparative Example 1 could it reach 4.95 V. Only when using the electrolytes of Examples 1 and Comparative Example 4 could KVPO4F achieve normal charge-discharge in the first cycle, with a discharge specific capacity of 104.6 mAh g⁻¹. -1 and 75.8 mAh g -1 A comparison of the electrochemical performance of different additives shows that electrolytes without any additives (Comparative Example 1) or with the addition of FEC (Comparative Example 2) and DTD (Comparative Example 3) all underwent severe decomposition during charging; while only electrolytes with the addition of LiDFOB (Example 1) and KDFOB (Comparative Example 4) effectively suppressed decomposition, allowing the KVPO4F cathode to achieve normal charge and discharge. However, due to the presence of DFOB... − and Li + Together, they form a denser and more robust CEI, resulting in superior electrochemical performance in Example 1.

[0099] Example 16

[0100] The following potassium-ion battery was assembled in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: a potassium metal sheet was used as the reference and counter electrode, aluminum foil as the working electrode, and glass fiber as the separator, using the 0.8 mol L⁻¹ solution from Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 2 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:DEC (V:V, 1:1) or 0.8 mol L in Example 3 -1 KPF6+ 0.10 mol / L -1 Using LiDFOB / EC:EMC (V:V, 1:1) as the electrolyte, a CR2032 coin cell is assembled from a battery assembly containing a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0101] Linear sweep voltammetry test: On an electrochemical workstation, linear sweep voltammetry was used at 5.0 mV s. -1 The electrochemical window of the electrolytes in Examples 1-3 was tested at a specific scan rate. The test results are as follows: Figure 3 As shown.

[0102] Figure 3 The electrolytes used in Examples 1-3 were scanned at a rate of 5.0 mV / s. -1 Linear sweep voltammetry curves were obtained. The electrochemical windows of the electrolytes in Examples 1-3 all reached above 5.0 V, indicating that the LiDFOB additive can effectively improve the high-voltage stability of the electrolyte in different ester solvent systems. This is because LiDFOB preferentially oxidizes and decomposes, forming a dense CEI film rich in LiF and boron oxides on the positive electrode surface, effectively inhibiting the continuous oxidative decomposition of the electrolyte under high voltage. Compared with Example 1, the oxidation onset potential (~5.1 V) of Examples 2 and 3 decreased, and the oxidation current rise rate in the high-voltage region was greater than that of Example 1. This is because PC is a cyclic carbonate with strong molecular polarity and high dielectric constant, which can optimize K when mixed with EC. + The solvation environment promotes the orderly decomposition and film formation of LiDFOB on the positive electrode surface, making the CEI film denser; while DEC and EMC are linear carbonates with lower viscosity but weaker polarity, and their control effect on the solvation structure is slightly weaker, resulting in their corresponding electrolytes having slightly lower oxidation stability under ultra-high voltage (above 5.1 V) than the EC:PC system, but it does not affect the stability in the actual working voltage range (2.0~4.95 V). Figure 3 It was confirmed that the LiDFOB additive can achieve high voltage stability at 5.0 V in different ester solvents, with the EC:PC system showing the best performance, providing key experimental basis for optimizing solvent composition.

[0103] Example 17

[0104] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing the 0.8 mol L⁻¹ solution from Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 2 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:DEC (V:V, 1:1) or 0.8 mol L in Example 3 -1 KPF6+ 0.10 mol L -1Using LiDFOB / EC:EMC (V:V, 1:1) as the electrolyte, a CR2032 coin cell is assembled from a battery assembly containing a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0105] Constant current charge-discharge test: After the above-mentioned KVPO4F potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a LandCT2001A battery testing system at a rate of 0.02 C within a voltage range of 2.0–4.95 V. The test results are as follows. Figure 4 As shown.

[0106] Figure 4 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Examples 1-3 are shown at a rate of 0.02 C. The KVPO4F material achieved reversible charge-discharge in electrolytes with three different ester solvents, and its charging curves did not show a plateau of continuous decomposition. This indicates that the LiDFOB additive can effectively suppress high-voltage decomposition of the electrolyte in different ester systems. However, there is a significant difference in discharge specific capacity; Example 1 shows 104.6 mAh g⁻¹. -1 This is higher than the 87.1 mAh g in Example 2. -1 And 100.5 mAh g in Example 3 -1 This result indicates that the LiDFOB and EC:PC solvent system has the best synergistic effect, which can maximize the potassium storage capacity of the material.

[0107] Example 18

[0108] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing 0.5 mol / L potassium ion exchange rate from Example 4. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 1.0 mol L in Example 5 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0109] Constant current charge-discharge test: After the above-mentioned KVPO4F potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a LandCT2001A battery testing system at a rate of 0.02 C within a voltage range of 2.0–4.95 V. The test results are as follows. Figure 5 As shown.

[0110] Figure 5 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Examples 4, 1, and 5 at a rate of 0.02 C are shown. This is achieved with a fixed LiDFOB addition amount (0.10 mol L). -1 Under these conditions, the first charge-discharge curves of KVPO4F material in electrolytes with three different KPF6 concentrations were normal, indicating that the LiDFOB additive is effective for electrolytes of different concentrations. As the KPF6 concentration increased from 0.5 mol / L... -1 Increased to 0.8 mol L -1 The discharge specific capacity during the first cycle significantly increased to its maximum value; it continued to increase to 1.0 mol L. -1 At that time, the capacity actually decreased, exhibiting an inverted U-shaped change. This is because 0.8 mol L... -1 The concentration achieved an optimal balance between ionic conductivity, CEI film formation quality, solvation structure optimization, and electrode wettability, resulting in the "Li" of LiDFOB. + The effects of "doping enhancement" and "weak solvation film formation optimization" are maximized. This result strongly supports the preferred concentration of 0.8 mol L in this invention. -1 KPF6 is the technical solution for the optimal potassium salt concentration.

[0111] Example 19

[0112] The following potassium-ion battery was assembled in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: a potassium metal sheet was used as the reference and counter electrode, aluminum foil as the working electrode, and glass fiber as the separator, using 0.8 mol L⁻¹ as in Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 6 -1 KPF6+ 0.05 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 7 -1 KPF6+ 0.15 mol L -1LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 8 -1 KPF6+ 0.20 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0113] Linear sweep voltammetry test: On an electrochemical workstation, linear sweep voltammetry was used at 5.0 mV s. -1 At a given scan rate, the electrochemical window of the electrolytes in Comparative Example 1, Example 1, Example 6, Example 7, and Example 8 was tested. The test results are as follows: Figure 6 As shown.

[0114] Figure 6 For the electrolytes of Comparative Example 1, Example 1, and Examples 6-8, a scan rate of 5.0 mV / s was used. -1 Linear sweep voltammetry curves were obtained. The electrochemical windows of the four different LiDFOB concentrations in Examples 1 and 6-8 all reached 1.5–5.5 V, indicating stable operation at high voltages. Furthermore, it was found that adding a trace amount of LiDFOB (0.05 mol L)... -1 In the case of [unclear], the electrochemical oxidation potential of the electrolyte in Example 6 also reached 5.5 V, indicating that the trace amount of LiDFOB additive [unclear] due to DFOB [unclear]. - and Li + The combined effect of these factors has a significant effect on the system. In contrast, the electrolyte in Comparative Example 1, which did not contain LiDFOB, exhibited a significant oxidation reaction at 3.5–5.0 V, indicating that the CEI film formed in Comparative Example 1 failed to effectively inhibit the continuous decomposition of the electrolyte.

[0115] Example 20

[0116] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing 0.8 mol L⁻¹ of the potassium ion exchange rate from Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 6 -1 KPF6+ 0.05mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 7 -1 KPF6+ 0.15 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 8 -1 KPF6+ 0.20 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0117] Constant current charge-discharge test: After the above-mentioned KVPO4F potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a LandCT2001A battery testing system at a rate of 0.02 C within a voltage range of 2.0–4.95 V. The test results are as follows. Figure 7 As shown.

[0118] Figure 7 The first charge-discharge curves of the KVPO4F potassium-ion battery cathode material of Example 9 in the electrolytes of Comparative Example 1 and Examples 6-8 are shown at a rate of 0.02 C. In Comparative Example 1, without additives, the electrolyte begins to decompose continuously after charging to approximately 4.1 V, indicating that the initially formed CEI cannot effectively prevent electrolyte oxidation. Only after a very long period of electrolyte decomposition can a protective CEI be formed, and its first-cycle discharge specific capacity is only 86.8 mAh g⁻¹. -1 The other four electrolytes with additives (Examples 1, 6-8) showed completely normal first-cycle charging, even with only 0.05 mol L⁻¹ added. -1 The LiDFOB (Example 6) also effectively inhibits the continuous decomposition of the electrolyte, enabling reversible charge-discharge. The first-cycle discharge specific capacity provided by the four electrolytes in Examples 1 and 2 was 91.9 mAh g⁻¹. -1 (Example 6) 104.6 mAh g -1 (Example 1), 96.9 mAhg -1 (Example 7), 94.1 mAh g -1 (Example 8) All of these have a higher capacity than Comparative Example 1, indicating that the DFOB... - Optimize K + Solvation structure and Li + DFOB Participation - The decomposition process resulted in a dense CEI protective layer with strong antioxidant properties. Example 1 exhibited the highest specific capacity, indicating that the additive dosage was optimal.

[0119] Example 21

[0120] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing 0.8 mol L⁻¹ of the potassium ion exchange rate from Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 6 -1 KPF6+ 0.05mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 7 -1 KPF6+ 0.15 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 8 -1 KPF6+ 0.20 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0121] Cyclic performance test: After the above-mentioned KVPO4F potassium-ion half-cells were left to stand for 12 hours, a constant current charge-discharge test was performed at a 0.2 C rate using a Land CT2001A battery testing system, cycling 100 times. The test results are as follows. Figure 8 As shown.

[0122] Figure 8 The cycling performance of the KVPO4F potassium-ion battery cathode material of Example 9 was compared with that of Comparative Examples 1, 6, 1, 7, and 8 electrolytes at a rate of 0.2 C. The cycling performance of KVPO4F material in five electrolytes with different LiDFOB concentrations was compared, and it was found that using the electrolyte of Example 1, KVPO4F achieved a specific capacity of 90.1 mAh g after 100 cycles. -1 The capacity retention rate was 97.5%. However, using the electrolytes of Comparative Examples 1 and Examples 6-8, the specific capacity of KVPO4F after 100 cycles was 50.0 mAh g. -1 83.3 mAh g -1 87.5 mAh g -1 84.4 mAh g -1The capacity retention rates were 72.9%, 86.7%, 85.7%, and 77.8%, respectively. It can be seen that the addition of LiDFOB significantly improved the battery cycle stability, which is attributed to the synergistic effect of LiDFOB's "Li⁺ doping enhancement" and "weak solvation film formation optimization." Furthermore, with increasing LiDFOB content, the capacity retention rate initially increased and then decreased. This is because excessive LiDFOB forms a thicker CEI film, inhibiting the rapid migration of potassium ions within the CEI and thus reducing cycle stability. In summary, the results show that the KVPO4F cathode material exhibits excellent cycle stability in the electrolyte of Example 1.

[0123] Example 22

[0124] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using KVPO4F from Example 9 as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing 0.8 mol L⁻¹ of the potassium ion exchange rate from Comparative Example 1. -1 KPF6 / EC:PC (V:V, 1:1) or 0.8 mol L in Example 6 -1 KPF6+ 0.05mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 1 -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 7 -1 KPF6+ 0.15 mol L -1 LiDFOB / EC:PC (V:V, 1:1) or 0.8 mol L in Example 8 -1 KPF6+ 0.20 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0125] Rate performance testing: After the KVPO4F potassium-ion half-cells were left to stand for 12 hours, constant current charge-discharge tests were performed using a Land CT2001A battery testing system at rates of 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, 3C, 5C, and 10C. The test results are as follows: Figure 9 As shown.

[0126] Figure 9The rate performance of the KVPO4F potassium-ion battery cathode material of Example 9 was compared with that of Comparative Example 1, Example 6, Example 1, Example 7, and Example 8 at rates of 0.1 C, 0.2 C, 0.3 C, 0.5 C, 1 C, 2 C, 3 C, 5 C, and 10 C. The comparison of the rate performance of KVPO4F material in electrolytes with five different LiDFOB concentrations revealed that, using the electrolyte of Example 1, KVPO4F still maintained a high specific capacity of 37.2 mAh g⁻¹ at 10 C. -1 Using the electrolytes of Comparative Example 1 and Examples 6-8, the specific capacity of KVPO4F at a rate of 10 C was 7.6 mAh g. -1 22.6 mAh g -1 33.7 mAh g -1 30.6mAh g -1 The comparison revealed that the addition of LiDFOB additive significantly improved the battery's rate performance, which is due to the effect of DFOB. - and Li + The combined effects of these additives resulted in a dense CEI film. Furthermore, with increasing LiDFOB content, the rate performance initially increased and then decreased. This is because excessive LiDFOB formed a thicker CEI film, slowing down the migration kinetics of potassium ions within the CEI and thus reducing rate performance. In summary, the KVPO4F cathode material exhibited excellent rate performance in the electrolyte of Example 1, indicating that the CEI film formed at this additive concentration achieved an optimal balance between protection and kinetic performance.

[0127] Example 23

[0128] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: KMnFe(CN)6 from Example 10 was used as the positive electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator. The 0.8 mol / L potassium hydroxide solution from Example 1 was used as the separator. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0129] Constant current charge-discharge test: After the above-mentioned KMnFe(CN)6 potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a LandCT2001A battery testing system at a rate of 0.02 C within a voltage range of 2.0–4.5 V. The test results are as follows. Figure 10 As shown.

[0130] Figure 10 The first charge-discharge curve of the KMnFe(CN)6 potassium-ion battery cathode material of Example 10 in the electrolyte of Example 1 at a rate of 0.02C is shown. The first-cycle discharge specific capacity of the KMnFe(CN)6 material is 125.28 mAh g. -1 The results show that the KMnFe(CN)6 cathode material exhibits excellent potassium storage performance in the electrolyte of Example 1.

[0131] Example 24

[0132] The following assembly of a potassium-ion half-cell was carried out in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using the K from Example 11 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2 is used as the positive electrode, potassium metal sheet as the reference electrode and counter electrode, and glass fiber as the diaphragm, using 0.8 mol L as in Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0133] Constant current charge-discharge test: The above K... 0.5 Mn 0.8 Ni 0.1 Co 0.1 After the O2 potassium-ion half-cell was left to stand for 12 hours, a constant current charge-discharge test was performed using a Land CT2001A battery testing system at a rate of 0.02 C within a voltage range of 1.5–4.0 V. The test results are as follows. Figure 11 As shown.

[0134] Figure 11 K in Example 11 0.5 Mn 0.8 Ni 0.1 Co 0.1 The first charge-discharge curve of the O2 potassium-ion battery cathode material in the electrolyte of Example 1 at a rate of 0.02 C. 0.5 Mn 0.8 Ni 0.1 Co 0.1 The initial discharge specific capacity of the O2 material is 106.2 mAh g. -1 The results showed that K in the electrolyte of Example 1 0.5 Mn 0.8 Ni 0.1 Co 0.1 O2 cathode materials exhibit excellent potassium storage performance.

[0135] Example 25

[0136] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using metallic Bi from Example 12 as the negative electrode, a potassium sheet as the reference and counter electrode, and glass fiber as the separator, and employing the 0.8 mol L⁻¹ potassium ion exchange rate from Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0137] Constant current charge-discharge test: After the above-mentioned Bi-potassium ion half-cell was left to stand for 12 hours, it was tested using the LandCT2001A battery test system at 200 mA g. -1 A constant current charge-discharge test was conducted within the voltage range of 0.01–1.5 V at a given rate. The test results are as follows: Figure 12 As shown.

[0138] Figure 12 The metal Bi potassium ion battery anode material of Example 12 was tested in the electrolyte of Example 1 at 200 mA g. -1 The first charge-discharge curves at various rates show that the first discharge specific capacity of the metallic Bi anode material is 200.5 mAh g⁻¹. -1 The results show that the metallic Bi anode material exhibits excellent potassium storage performance in the electrolyte of Example 1.

[0139] Example 26

[0140] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using the BiSn alloy from Example 13 as the negative electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing the 0.8 mol L⁻¹ potassium ion exchange rate from Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0141] Constant current charge-discharge test: After the above-mentioned BiSn alloy potassium-ion half-cell was left to stand for 12 hours, it was tested using the LandCT2001A battery testing system at 200 mA g. -1 A constant current charge-discharge test was conducted within the voltage range of 0.01–1.5 V at a given rate. The test results are as follows: Figure 13 As shown.

[0142] Figure 13 The BiSn alloy potassium-ion battery anode material of Example 13 was tested in the electrolyte of Example 1 at 200 mAg. -1 The first-cycle charge-discharge curves at various rates show that the BiSn alloy anode material has a first-cycle discharge specific capacity of 339.9 mAh g⁻¹. -1 The results show that the BiSn alloy anode material exhibits excellent potassium storage performance in the electrolyte of Example 1.

[0143] Example 27

[0144] The following potassium-ion half-cell assembly was performed in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: using the BiSn alloy from Example 13 as the negative electrode, a potassium metal sheet as the reference and counter electrode, and glass fiber as the separator, and employing the 0.8 mol L⁻¹ potassium ion exchange rate from Example 1. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0145] Cyclic performance test: After the above-mentioned BiSn alloy potassium-ion half-cell was left to stand for 12 hours, it was tested using the Land CT2001A battery test system at 200 mA g. -1 A constant current charge-discharge test was performed at the specified rate, with 100 cycles. The test results are as follows: Figure 14 As shown.

[0146] Figure 14 The BiSn alloy potassium-ion battery anode material of Example 13 was tested in the electrolyte of Example 1 at 200 mAg. -1 Cycling performance at various rates. Using the electrolyte from Example 1, the BiSn alloy exhibited a specific capacity of 211.6 mAhg after 100 cycles. -1 The capacity retention rate was 76.6%. These results demonstrate that the BiSn alloy anode material exhibits excellent cycle stability in the electrolyte of Example 1.

[0147] Example 28

[0148] The following potassium-ion full cell was assembled in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: KVPO4F from Example 9 was used as the positive electrode, BiSn alloy from Example 13 as the negative electrode, the mass ratio of the positive to negative electrode active materials was approximately 2:1, glass fiber was used as the separator, and 0.8 mol / L of the active material from Example 1 was used. -1 KPF6+ 0.10 mol L -1LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0149] Constant current charge-discharge test: After the above KVPO4F / / BiSn potassium-ion full cell was left to stand for 12 hours, it was tested using the LandCT2001A battery test system at 75 mA g. -1 Constant current charge-discharge tests were conducted within the voltage range of 2.0–4.95 V at various rates. The test results are as follows: Figure 15 As shown.

[0150] Figure 15 For the KVPO4F / / BiSn potassium ion full cell in the electrolyte of Example 1, at 75 mA g -1 The first-cycle charge-discharge curves at various rates show that the first-cycle discharge specific capacity of the KVPO4F / / BiSn full cell is 80.2 mAh g⁻¹. -1 In summary, the results show that the KVPO4F / / BiSn full cell exhibits excellent potassium storage performance in the electrolyte of Example 1.

[0151] Example 29

[0152] The following potassium-ion full cell was assembled in a glove box under an argon atmosphere, with water and oxygen concentrations both less than or equal to 0.1 ppm: KVPO4F from Example 9 was used as the positive electrode, BiSn alloy from Example 13 as the negative electrode, the mass ratio of the positive to negative electrode active materials was approximately 2:1, glass fiber was used as the separator, and 0.8 mol / L of the active material from Example 1 was used. -1 KPF6+ 0.10 mol L -1 LiDFOB / EC:PC (V:V, 1:1) is used as the electrolyte. The CR2032 coin cell is assembled using a battery assembly that includes a negative electrode shell, a positive electrode shell, a gasket, and a spring.

[0153] Cyclic performance test: After the above KVPO4F / / BiSn potassium ion full cell was left to stand for 12 hours, it was tested using a LandCT2001A battery test system at 75 mA g. -1 A constant current charge-discharge test was performed at the specified rate, for 95 cycles. The test results are as follows: Figure 16 As shown.

[0154] Figure 16 For the KVPO4F / / BiSn potassium ion full cell in the electrolyte of Example 1, at 75 mA g -1 Cycling performance at high rates. Using the electrolyte of Example 1, the specific capacity of the KVPO4F / / BiSn full cell was 76.0 mAh g after 95 cycles. -1The capacity retention rate was 95%. In summary, the KVPO4F / / BiSn full cell exhibits excellent cycling stability in the electrolyte of Example 1.

Claims

1. A 5.0 V high-voltage potassium-ion battery ester electrolyte, characterized in that, It includes ester solvents, potassium salts, and additives; the potassium salt is potassium hexafluorophosphate; and the additive is lithium difluorooxalate borate.

2. The 5.0 V high-voltage potassium-ion battery ester electrolyte according to claim 1, characterized in that, The concentration of potassium hexafluorophosphate is 0.5–1.0 mol / L. -1 The concentration of lithium difluorooxalate borate is 0.05–0.20 mol / L. -1 .

3. The 5.0 V high-voltage potassium-ion battery ester electrolyte according to claim 1, characterized in that, The ester solvent is a mixture of ethylene carbonate and propylene carbonate, diethyl carbonate, or methyl ethyl carbonate.

4. The 5.0 V high-voltage potassium-ion battery ester electrolyte according to claim 3, characterized in that, The volume ratio of ethylene carbonate to propylene carbonate, diethyl carbonate, or methyl ethyl carbonate is 1:

1.

5. The 5.0 V high-voltage potassium-ion battery ester electrolyte according to claim 4, characterized in that, The ester solvent is composed of ethylene carbonate and propylene carbonate in a volume ratio of 1:

1.

6. A method for preparing a 5.0 V high-voltage potassium-ion battery ester electrolyte according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Mix the ester solvents evenly to obtain mixed solvent A; (2) Add potassium hexafluorophosphate to mixed solvent A and mix well to obtain premixed solution B; (3) Add the additive lithium difluorooxalate borate to the premixed solution B, mix evenly, and let stand to obtain the electrolyte.

7. The application of the electrolyte according to any one of claims 1 to 5 in a potassium-ion battery.

8. The application according to claim 7, characterized in that, The potassium-ion battery is either a half-cell or a full-cell battery.

9. The application according to claim 8, characterized in that, The working electrode in the half-cell of the potassium-ion battery is a polyanionic compound, potassium vanadium fluorophosphate, Prussian white, layered oxide, metallic bismuth, or a bismuth-tin alloy.

10. The application according to claim 8, characterized in that, The positive electrode material of the potassium-ion battery is a polyanionic compound, vanadium fluorophosphate potassium; the negative electrode material is a bismuth-tin alloy; and the separator is glass fiber.

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