Potassium ion battery, positive plate or negative plate and preparation method thereof

Abstract

The invention relates to a potassium ion battery, a positive plate or a negative plate and a preparation method of the positive plate or the negative plate. A potassium supplement additive KCOOH, a Prussian blue analogue K2Mn [Fe (CN) 6], a conductive agent and a binder are added; or mixing the graphite, the conductive agent and the binder in a glove box filled with argon, adding the mixture into a ball milling tank, sealing, taking out the sealed ball milling tank from the glove box, mounting the ball milling tank on a planetary ball mill, carrying out ball milling, disassembling the ball milling tank in the glove box, taking out the mixture, and carrying out oscillation screening to obtain a sample; the method comprises the following steps: adding a slurry solvent into a sample, mixing, adding into a mixing tank, sealing the mixing tank in a glove box, mixing on a mixer, spreading the obtained slurry at the top end of a current collector, and coating and drying to obtain a positive plate or a negative plate. The potassium formate is used as a potassium supplement additive, under the condition of room temperature, the cycle life of 0.1 C current density is more than 300 times, the energy density is 339.9 Wh / kg, and a relatively large application field is provided for a high-performance potassium ion battery.

Description

Technical Field

[0001] The invention belongs to the technical field of potassium ion batteries, and in particular relates to a potassium ion battery, a positive electrode sheet or a negative electrode sheet and a preparation method thereof. Background Art

[0002] In recent years, lithium-ion batteries have dominated the energy storage market. Although lithium-ion batteries are widely used in portable electronic devices and new energy vehicles, due to the scarcity of raw materials, the production cost and output of lithium-ion batteries are difficult to meet the growing demand of the energy storage market. In contrast, potassium-ion batteries reduce dependence on high-cost elements such as lithium, nickel, cobalt and copper, and are compatible with current commercial graphite, and have become a low-cost and sustainable alternative to lithium-ion batteries. However, the potassium-free negative electrode of conventional potassium-ion batteries often suffers from potassium loss caused by the formation of a solid electrolyte interphase (Solid Electrolyte Interphase) in the first cycle. This loss will lead to the consumption of potassium in the positive electrode material, which will ultimately lead to a decrease in the battery's energy density.

[0003] On this basis, if we can find another potassium source outside the positive electrode material and let the formation of SEI consume the potassium ions in the potassium source, we can reduce the consumption of potassium ions in the positive electrode material and ultimately increase the capacity of the potassium ion battery. This process of providing an external potassium source is called pre-potassiumization. Pre-potassiumization of electrode materials can effectively compensate for the consumption of potassium ions by side reactions during the first cycle of battery operation and increase the energy density of the battery.

[0004] The current pre-potassiumization methods mainly include electrochemical pre-potassiumization, chemical pre-potassiumization and the use of positive electrode potassium supplement additives. Additional potassium ions are introduced into the positive or negative electrode of the battery by physical or chemical methods to compensate for the consumption of potassium ions during the formation of SEI. Electrochemical pre-potassiumization refers to the process in which the electrode undergoes an electrochemical reaction with metallic potassium in the presence of an electrolyte. However, the electrode after electrochemical pre-potassiumization is unstable in the air due to its high chemical reactivity. The subsequent battery manufacturing process must be carried out under inert atmosphere conditions, which limits its large-scale industrial production. Chemical pre-potassiumization refers to the use of a strongly reducing potassium-containing reagent to introduce active potassium into the negative electrode through a redox reaction for pre-potassiumization treatment. However, the chemical pre-potassiumization reagent has a low redox potential, high reactivity and flammability, and has hidden safety hazards, which limits its industrial application. Summary of the invention

[0005] In order to overcome the problems existing in the prior art, the present invention provides a potassium ion battery, a positive electrode sheet or a negative electrode sheet and a preparation method thereof, which are used to overcome the current defects.

[0006] A method for preparing a positive electrode sheet or a negative electrode sheet for a potassium ion battery, the method comprising the steps of:

[0007] S1. When preparing a positive electrode, a potassium supplement KCOOH, a Prussian blue analog K2Mn[Fe(CN)6], a conductive agent and a binder are added in a certain proportion; or, when preparing a negative electrode, graphite, a conductive agent and a binder are added in a certain proportion to a ball mill in a glove box filled with argon, and then the ball mill is sealed in the glove box;

[0008] S2. The sealed ball mill is taken out from the glove box, and the ball mill is mounted on a planetary ball mill to ball mill the mixture in the ball mill for a period of time at a certain speed, and then the ball mill is removed and disassembled in the glove box, and the mixture is taken out and vibrated and sieved as a sample;

[0009] S3. Add the slurry solvent to the sample and add the mixture to the mixing tank, seal the mixing tank in the glove box, remove the mixing tank from the glove box after sealing, and mix at a certain speed for a period of time on the mixer;

[0010] S4. Spread the slurry obtained after the mixing is completed on the top of the current collector, apply and dry it to obtain a positive electrode sheet or a negative electrode sheet.

[0011] According to the aspects and any possible implementation methods described above, an implementation method is further provided, wherein the binder for preparing the negative electrode sheet is polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, polyvinyl alcohol PVA, sodium hydroxymethyl cellulose CMC, sodium alginate or potassium alginate; and the binder for preparing the positive electrode sheet is polyvinylidene fluoride PVDF or polytetrafluoroethylene PTFE.

[0012] According to the above aspects and any possible implementation, an implementation is further provided, wherein the conductive agent for preparing the positive electrode sheet or the negative electrode sheet is a mixture of one or more of acetylene black, Ketjen black, carbon nanotubes or graphene.

[0013] The present invention also provides a positive electrode sheet or a negative electrode sheet for a potassium ion battery, wherein the positive electrode sheet or the negative electrode sheet is prepared by the method described.

[0014] According to the aspects described above and any possible implementation method, an implementation method is further provided, wherein the total proportion of KCOOH in the positive electrode sheet is 5wt.% to 15wt.%, the total proportion of K2Mn[Fe(CN)6] is 60wt.% to 80wt.%, and the total proportion of the conductive agent and the binder is 35wt.% to 5wt.%.

[0015] According to the above aspects and any possible implementation, a further implementation is provided, wherein the loading amount of K2Mn[Fe(CN)6] in the positive electrode sheet is 2 mg / cm 2~10mg / cm.

[0016] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the total proportion of graphite in the negative electrode sheet is 70wt.% to 95wt.%, and the total proportion of the conductive agent and the binder is 30wt.% to 5wt.%.

[0017] The present invention provides a potassium ion battery, wherein the battery comprises a positive electrode sheet and / or a negative electrode sheet.

[0018] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the potassium ion battery comprises, from top to bottom, a negative electrode shell, a spring, a gasket, a negative electrode sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, a gasket and a positive electrode shell.

[0019] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the potassium ion battery comprises, from top to bottom, a negative electrode shell, a spring, a gasket, a potassium sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, a gasket and a positive electrode shell.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention uses a potassium supplement additive when preparing the positive electrode sheet, which is directly used in the electrode preparation process, and then the prepared positive electrode sheet is used to form a potassium ion battery that can maintain high energy density, high capacity retention rate and long cycle life. The battery energy density of the positive electrode sheet using the potassium supplement additive KCOOH is 334.4Wh / kg. After 120 cycles, the capacity retention rate is 98.27%. The use of the potassium supplement additive KCOOH significantly improves the cycle stability and energy density of the K2Mn[Fe(CN)6]-graphite full battery. Potassium formate is used as a potassium supplement additive, and its decomposition potential is 4 to 4.1V (vs.K + / K). At room temperature, the cycle life at 0.1C current density is greater than 300 times, and the energy density is 339.9Wh / kg, which provides a large application field for high-performance potassium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the XRD pattern of the KCOOH material in Example 1 of the present invention;

[0023] Figure 2 This is a graph showing the decomposition voltage and specific capacity of the potassium supplement KCOOH in Example 1 of the present invention at a current density of 15 mA / g;

[0024] Figure 3This is a comparison diagram of the first cycle charge and discharge curves of the K2Mn[Fe(CN)6] positive electrode in Example 1 of the present invention with and without the potassium supplement additive KCOOH added;

[0025] Figure 4 This is a cycle stability diagram of the potassium ion half-cell at current densities of 15 mA / g and 75 mA / g after the additive KCOOH is added in Example 1 of the present invention;

[0026] Figure 5 Graph showing the cycling stability of the potassium ion battery at current densities of 15 mA / g and 75 mA / g in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods described below, and similar technologies and methods should be considered to be within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] It should be clear that the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] A method for preparing a positive electrode sheet or a negative electrode sheet for a potassium ion battery of the present invention comprises the steps of:

[0030] S1. When preparing a positive electrode, a potassium supplement KCOOH, a Prussian blue analog K2Mn[Fe(CN)6], a conductive agent and a binder are added in a certain proportion; or, when preparing a negative electrode, graphite, a conductive agent and a binder are added in a certain proportion to a ball mill in a glove box filled with argon, and then the ball mill is sealed in the glove box;

[0031] S2. The sealed ball mill is taken out from the glove box, and the ball mill is mounted on a planetary ball mill to ball mill the mixture in the ball mill for a period of time at a certain speed, and then the ball mill is removed and disassembled in the glove box, and the mixture is taken out and vibrated and sieved as a sample;

[0032] S3. Add the slurry solvent to the sample and add the mixture to the mixing tank, seal the mixing tank in the glove box, remove the mixing tank from the glove box after sealing, and mix at a certain speed for a period of time on the mixer;

[0033] S4. Spread the slurry obtained after the mixing is completed on the top of the current collector, apply and dry it to obtain a positive electrode sheet or a negative electrode sheet.

[0034] Specifically, the implementation process of the present invention is as follows:

[0035] The potassium supplement additive KCOOH is directly added to the electrode during the preparation of the positive electrode, and plays a role in the first cycle of charging of the battery. Specifically, during the preparation of the positive electrode, KCOOH, K2Mn[Fe(CN)6], conductive agent, and binder are added to a ball mill in a glove box filled with argon (the water and oxygen content are all less than 0.1ppm) in a certain proportion (the mass ratio of zirconia ball milling beads to the total amount of added substances is 20:1). During the preparation of the negative electrode, graphite, conductive agent, and binder are added to a ball mill in a glove box filled with argon (the water and oxygen content are all less than 0.1ppm) in a certain proportion (the mass ratio of zirconia ball milling beads to the total amount of added substances is 20:1). Then the ball mills are sealed in the glove box respectively to ensure that the inside of the ball mill is an argon environment. After sealing, the ball mill is taken out of the glove box, the ball mill is installed on a planetary ball mill, and the mixture in the ball mill is ball milled at a speed of 400 rpm for 30 minutes. After the ball milling is completed, the ball mill jar is disassembled in the glove box, and the ball mill beads and the mixture therein are poured into a 50-mesh sample sieve at the same time. After the sample sieve is vibrated, the sample screened by the sample sieve is collected to obtain the corresponding sample. The sample is then weighed and added to the mixing tank, and then 1.5 mL of N-methylpyrrolidone (NMP) is taken as a slurry solvent for every 0.3 g of sample, added to the mixing tank, and then the mixing tank is sealed in the glove box to ensure that the interior of the mixing tank is an argon environment. After sealing, the mixing tank is taken out of the glove box and mixed at a speed of 1000 rpm on the mixer for 1 hour. After the mixing is completed, the uniform slurry is spread on the top of the current collector and coated using a coating machine to obtain a positive electrode sheet or a negative electrode sheet, wherein the positive electrode sheet slurry components are KCOOH, K2Mn[Fe(CN)6] and a conductive agent and a binder, and the negative electrode sheet slurry components are graphite and a conductive agent and a binder. After coating, the positive electrode sheet was dried in a vacuum oven at 80°C for 12 hours. After drying, the electrode sheet was cut using a cutting machine and the battery was assembled for testing.

[0036] As an embodiment disclosed in the present invention, the present invention also discloses a positive electrode sheet or a negative electrode sheet, which is prepared by the above method of the present invention, wherein the total proportion of the potassium supplement KCOOH in the positive electrode sheet is 5wt.% to 15wt.%, the total proportion of K2Mn[Fe(CN)6] in the positive electrode sheet is 60wt.% to 80wt.%, and the total proportion of the conductive agent and the binder in the positive electrode sheet is 35wt.% to 5wt.%. To ensure that the potassium supplement additive, the mass proportion of the positive electrode active material, the conductive carbon and the binder is 100%. The loading amount of the positive electrode active material can be controlled at 2mg / cm 2 ~10mg / cm 2 scope;

[0037] The negative electrode active material in the negative electrode sheet is graphite, which accounts for 80wt.% to 95wt.% by mass. The total proportion (mass proportion) of conductive carbon and binder in the negative electrode sheet is 20wt.% to 5wt.%. The sum of the mass proportions of the negative electrode active material, conductive carbon and binder is guaranteed to be 100%. The loading amount of the negative electrode active material can be controlled at 1mg / cm 2 ~5mg / cm 2 scope.

[0038] Preferably, the binder used in preparing the positive electrode sheet is one of polyvinylidene fluoride PVDF and polytetrafluoroethylene PTFE.

[0039] Preferably, the binder used in preparing the negative electrode sheet is one of polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, polyvinyl alcohol PVA, sodium hydroxymethyl cellulose CMC, potassium alginate and sodium alginate.

[0040] The current collectors of the positive electrode sheet and the negative electrode sheet are made of aluminum foil, which has a low cost and meets the requirements of low-cost industrial production.

[0041] In the specific implementation, in the potassium ion battery provided by the present invention, the active material ratio of the positive electrode sheet and the negative electrode sheet can be controlled in the range of 1.8:1 to 1.9:1, which can ensure the maximum capacity of the battery while avoiding potassium ion deposition in the battery as much as possible. Specifically, in the process of preparing the battery, the mass ratio of K2Mn[Fe(CN)6] in the positive electrode sheet and the graphite in the negative electrode sheet is in the range of 1.8:1 to 1.9:1.

[0042] In a specific implementation, the conductive carbon used in preparing 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 the positive electrode sheet and the negative electrode sheet can also use two different conductive carbons, which is not limited here.

[0043] 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 aluminum foil.

[0044] 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, potassium alginate, and sodium alginate, and the current collector is aluminum foil.

[0045] As an embodiment disclosed in the present invention, the present invention also provides a potassium ion battery, the battery comprising a positive electrode sheet and / or a negative electrode sheet prepared by the method of the present invention, including two types of half-cells and full cells. Specifically, the half-cell includes a negative electrode shell, a shrapnel, a gasket, a potassium metal sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, and a positive electrode shell from top to bottom; the full battery includes a negative electrode shell, a shrapnel, a gasket, a negative electrode sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, and a positive electrode shell from top to bottom. In the specific implementation, the potassium ion battery electrolyte includes a potassium salt and a solvent, and the solvent of the electrolyte is triethyl phosphate TEP. The electrolyte potassium salt is potassium bis(fluorosulfonyl)imide KFSI. Preferably, the potassium salt concentration is 2.5 mol / LKFSI.

[0046] 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 paper.

[0047] It should be noted that the potassium ion battery provided by the present invention, wherein the half-cell or the full cell may be a button-type potassium ion battery, or the full cell may be a soft-pack potassium ion battery, which is not limited here.

[0048] 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 battery pole piece is polytetrafluoroethylene PTFE, the solvent used to prepare the slurry is isopropyl alcohol; when the binder used in the battery pole piece is sodium carboxymethyl cellulose CMC, the solvent used to prepare the slurry is water; when the binder used in the battery pole piece is sodium alginate or sodium alginate, the solvent used to prepare the slurry is water.

[0049] It should be noted that in the process of preparing the electrode slurry, there is no fixed ratio for the mixture of the solvent, the electrode material, the binder, and the conductive agent, as long as they are stirred evenly to form a slurry.

[0050] 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.

[0051] Example 1

[0052] (1) Preparation of positive electrode sheet: K2Mn[Fe(CN)6](KMF) was used as the positive electrode active material and KCOOH was used as the potassium supplement additive. Figure 1 The XRD pattern of the potassium supplement additive is shown. Figure 2The schematic diagram of the decomposition voltage and decomposition capacity of the potassium supplement additive is shown. The positive electrode active material, potassium supplement additive, conductive carbon Ketjen black, and binder PVDF are mixed in a mass ratio of 7.3:0.7:1:1, and a ball mill (the mass ratio of zirconium oxide ball milling beads to the total amount of added substances is 20:1, and the substances can be evenly mixed at this mass ratio) is added to a glove box filled with argon (the water and oxygen content are all less than 0.1ppm), and then the ball mill is sealed in the glove box to ensure that the inside of the ball mill is an argon environment. After sealing, the ball mill is taken out of the glove box and ball milled at 400 rpm for 30 minutes on a planetary ball mill. After the ball milling is completed, the ball mill is disassembled in the glove box, the sample is taken out and weighed and added to the mixing tank, and then 1.5mL of N-methylpyrrolidone NMP is taken for every 0.3g of sample and added to the mixing tank, and then the mixing tank is sealed in the glove box to ensure that the inside of the mixing tank is an argon environment. After sealing, take the mixing tank out of the glove box and mix it on the mixer at 1000 rpm for 1 hour. After mixing, spread the uniform slurry on the top of the current collector and apply it using a coater. After coating, dry the positive electrode sheet in a vacuum oven at 80°C for 12 hours. After drying, use a cutter to cut the electrode sheet and assemble the battery for testing. The loading amount of the positive electrode active material is 2 mg / cm 2 .

[0053] (2) Preparation of half-cell: Use potassium metal sheet as counter electrode and reference electrode, glass fiber as separator, and 2.5 mol / L potassium bis(fluorosulfonyl)imide (KFSI) dissolved in triethyl phosphate (TEP) as electrolyte. In a glove box with water and oxygen content less than 0.1 ppm, assemble button cells in the order of negative electrode shell, spring sheet, gasket, potassium sheet, electrolyte, separator, electrolyte, positive electrode sheet, gasket, and positive electrode shell. After assembly, use a button cell sealing machine to compact the cell for subsequent testing.

[0054] (3) Potassium supplement application test: After the battery is assembled, it is left to stand for 12 hours, and a constant current charge and discharge test is performed at room temperature using a battery test system. + / K, disassemble the battery in the glove box, exhaust the gas, and assemble the positive electrode sheet, potassium sheet and diaphragm in the battery into a button battery in the order of negative electrode shell, spring, gasket, potassium sheet, electrolyte, diaphragm, electrolyte, positive electrode sheet, gasket, positive electrode shell from top to bottom; after assembly, use a button battery sealer to compact the battery for subsequent testing. After the battery is assembled, let it stand for 12 hours, use the battery test system at room temperature with a current density of 0.1C, and discharge it to 2.7Vvs.K first. + / K, then charged to 4.4V vs.K + / K process was cycled, and after 10 cycles, the current density was changed to 0.5C for cycle stability test. Figure 3The charge and discharge curves of the positive electrode sheet with and without potassium supplement KCOOH are compared. After adding 7% potassium supplement KCOOH to the positive electrode sheet, the potassium supplement KCOOH has a high charge and discharge rate at 4-4.1V (vs. K + / K) decomposes, and the first-cycle charging capacity is 198 mAh / g, which is higher than the first-cycle charging capacity without additives, proving that the additives decompose within the positive electrode operating voltage range and provide additional potassium ions. Figure 4 The half-cell cycle stability of KMF after using the additive KCOOH was demonstrated. The capacity retention rate was 97.63% after 120 cycles at a current density of 0.5C (1C = 150mA / g), proving that the use of KCOOH does not affect the stability of the KMF half-cell.

[0055] Example 2

[0056] (1) Preparation of positive electrode sheet: The positive electrode sheet was prepared by the method of step (1) of Example 1.

[0057] (2) Preparation of negative electrode sheet: Commercial graphite was used as the negative electrode active material. The negative electrode active material, conductive carbon Ketjen black, and binder CMC were mixed in a mass ratio of 8:1:1. After adding water and stirring evenly, the mixture was evenly coated on the aluminum foil current collector. After vacuum drying at 80°C, the negative electrode sheet was obtained. The loading amount of the negative electrode active material was 1 mg / cm 2 .

[0058] (3) Preparation of potassium ion batteries: Glass fiber was used as the separator and 2.5 mol / L potassium bis(fluorosulfonyl)imide (KFSI) was selected as the electrolyte in a triethyl phosphate (TEP) solution. In a glove box where the water and oxygen content were both less than 0.1 ppm, button cells were assembled 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, the battery was compacted using a button battery sealing machine for subsequent testing.

[0059] (4) Potassium supplement additive application test: After the battery is assembled, let it stand for 12 hours, and use the battery test system to perform constant current charge and discharge test at room temperature. After the first cycle is charged to 4.3V, the battery is disassembled in the glove box, and after exhausting, the positive electrode sheet, negative electrode sheet and diaphragm in the battery are assembled into a button battery in the order of negative electrode shell, spring, gasket, negative electrode sheet, electrolyte, diaphragm, electrolyte, positive electrode sheet, gasket, positive electrode shell from top to bottom; after assembly, the button battery sealing machine is used to compact the battery for subsequent testing. After the battery is assembled, let it stand for 12 hours, and use the battery test system at room temperature to use a current density of 0.1C, and cycle it according to the process of first discharging to 1.0V and then charging to 4.3V. After 10 cycles, change to 0.5C current density for cycle stability test. Figure 4The battery showed a cycle stability after using the potassium supplement KCOOH. After using the potassium supplement KCOOH, the potassium supplement KCOOH was 4-4.1V (vs.K + / K) decomposition battery can maintain a maximum discharge capacity of 144.5mAh / g, and the battery energy density is 334.4Wh / kg. After 120 cycles, the capacity retention rate is 98.27%. Compared with the battery without potassium supplement KCOOH, the capacity retention rate of 100 cycles is only 30.79%. The use of potassium supplement KCOOH significantly improves the cycle stability and energy density of K2Mn[Fe(CN)6]-graphite full battery.

[0060] 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.

[0061] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a positive electrode sheet or a negative electrode sheet for a potassium ion battery, characterized in that: The method comprises the steps of: S1. When preparing a positive electrode, a potassium supplement KCOOH, a Prussian blue analog K2Mn[Fe(CN)6], a conductive agent and a binder are added in a certain proportion; or, when preparing a negative electrode, graphite, a conductive agent and a binder are added in a certain proportion to a ball mill in a glove box filled with argon, and then the ball mill is sealed in the glove box; S2. The sealed ball mill is taken out from the glove box, and the ball mill is mounted on a planetary ball mill to ball mill the mixture in the ball mill for a period of time at a certain speed, and then the ball mill is removed and disassembled in the glove box, and the mixture is taken out and vibrated and sieved as a sample; S3. Add the slurry solvent to the sample and then add the mixture to the mixing tank, seal the mixing tank in the glove box, remove the mixing tank from the glove box after sealing, and mix at a certain speed on the mixer for a period of time; S4. Spread the slurry obtained after the mixing is completed on the top of the current collector, apply and dry it to obtain a positive electrode sheet or a negative electrode sheet.

2. The method according to claim 1, characterized in that The binder for preparing the negative electrode sheet is polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, polyvinyl alcohol PVA, sodium hydroxymethyl cellulose CMC, sodium alginate or potassium alginate; the binder for preparing the positive electrode sheet is polyvinylidene fluoride PVDF or polytetrafluoroethylene PTFE.

3. The method according to claim 1, characterized in that The conductive agent for preparing the positive electrode sheet or the negative electrode sheet is a mixture of one or more of acetylene black, Ketjen black, carbon nanotubes or graphene.

4. A positive electrode or negative electrode for a potassium ion battery, characterized in that: The positive electrode sheet or the negative electrode sheet is prepared by the method according to any one of claims 1 to 3.

5. The positive electrode sheet or negative electrode sheet of a potassium ion battery according to claim 4, characterized in that: In the positive electrode sheet, the total proportion of KCOOH is 5wt.% to 15wt.%, the total proportion of K2Mn[Fe(CN)6] is 60wt.% to 80wt.%, and the total proportion of the conductive agent and the binder is 35wt.% to 5wt.%.

6. The positive electrode sheet or negative electrode sheet of a potassium ion battery according to claim 4, characterized in that: The loading amount of K2Mn[Fe(CN)6] in the positive electrode sheet is 2 mg / cm 2 ~10mg / cm.

7. The positive electrode sheet or negative electrode sheet of a potassium ion battery according to claim 4, characterized in that: The total proportion of graphite in the negative electrode sheet is 70wt.% to 95wt.%, and the total proportion of the conductive agent and the binder is 30wt.% to 5wt.%.

8. A potassium ion battery, characterized in that: The battery comprises the positive electrode sheet and / or the negative electrode sheet according to any one of claims 4 to 7.

9. The potassium ion battery according to claim 8, characterized in that The potassium ion battery comprises, from top to bottom, a negative electrode shell, a spring, a gasket, a negative electrode sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, a gasket and a positive electrode shell.

10. The potassium ion battery according to claim 9, characterized in that: The potassium ion battery comprises, from top to bottom, a negative electrode shell, a spring, a gasket, a potassium sheet, an electrolyte, a diaphragm, an electrolyte, a positive electrode sheet, a gasket and a positive electrode shell.

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