Negative electrode material and preparation method thereof, battery and electronic device

Abstract

The invention relates to a negative electrode material and a preparation method thereof, a battery and an electronic device, the preparation method comprises the following steps: dissolving zinc nitrate hexahydrate in a first solvent to obtain a solution A; dissolving 2-methylimidazole in a second solvent to obtain a solution B; adding the solution B into the solution A to obtain an intermediate A; reacting the intermediate A with dopamine in the presence of alkali to obtain an intermediate B, carbonizing in a first protective gas atmosphere to obtain an intermediate C, and reacting in the presence of acid to obtain an intermediate D; adding the intermediate D into water, and adding a molybdenum source to obtain a solution C; adding a reducing agent and a selenium source into water to obtain a solution D; adding the solution D into the solution C for hydrothermal reaction to obtain an intermediate E; and performing high-temperature annealing treatment on a sulfur source and the intermediate E in a second protective gas atmosphere to obtain the negative electrode material. Comprising the negative electrode material is stable in negative electrode structure, has excellent capacitance and also has excellent cycle performance under high flow density.

Description

Technical Field

[0001] The present invention relates to the technical field of potassium ion batteries, and in particular to a negative electrode material and a preparation method thereof, a battery and an electronic device. Background Art

[0002] With the increasing global awareness of environmental protection and the demand for sustainable development, the exploration of efficient and environmentally friendly energy storage technologies has become increasingly urgent. In the past few decades, lithium-ion batteries (LIBs) have been widely used in portable electronic devices, electric vehicles, and grid energy storage due to their excellent energy density and lightness. However, the low natural abundance and uneven distribution of lithium resources have led to rising costs in recent years, further limiting their large-scale application. Against this background, potassium-ion batteries have shown great development potential due to their abundant potassium resource reserves, low cost, and energy storage mechanism similar to that of lithium-ion batteries.

[0003] Molybdenum diselenide (MoSe2) has a high theoretical capacity and a large interlayer spacing K + However, during the charge and discharge cycle, the volume expansion of MoSe2 often leads to a decrease in structural stability, which in turn affects battery performance. Summary of the Invention

[0004] In view of this, embodiments of the present application provide a negative electrode material and a preparation method thereof, a battery, and an electronic device to solve at least one problem existing in the background technology.

[0005] The first aspect of the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0006] S1: dissolving zinc nitrate hexahydrate in a first solvent to obtain solution A; dissolving 2-methylimidazole in a second solvent to obtain solution B; adding solution B to solution A to obtain intermediate A;

[0007] S2: reacting the intermediate A obtained in step S1 with dopamine in the presence of a base to obtain an intermediate B, followed by carbonization under a first protective gas atmosphere to obtain an intermediate C, and then reacting in the presence of an acid to obtain an intermediate D;

[0008] S3: adding the intermediate D obtained in step S2 to water and a molybdenum source to obtain a solution C; adding a reducing agent and a selenium source to the water to obtain a solution D; adding the solution D to the solution C for a hydrothermal reaction to obtain an intermediate E;

[0009] S4: Under a second protective gas atmosphere, the sulfur source and the intermediate E obtained in step S3 are subjected to a high-temperature annealing treatment to obtain the negative electrode material.

[0010] Preferably, in step S1, the first solvent is selected from one or more of water, methanol, ethanol and ethylene glycol, and the molar concentration of zinc nitrate hexahydrate in solution A is 50 to 110 mmol / L;

[0011] Preferably, in step S1, the second solvent is selected from one or more of water, methanol, ethanol and ethylene glycol, and the molar concentration of the 2-methylimidazole in solution B is 200 to 400 mmol / L.

[0012] Preferably, in step S2, the mass ratio of the intermediate A to dopamine is (0.5-3):1;

[0013] Preferably, in step S2, the base is a Trizma base solution, and the pH of the Trizma base solution is 8 to 8.5;

[0014] More preferably, the dopamine is dopamine hydrochloride.

[0015] Preferably, in step S2, the first protective gas is selected from at least one of argon, helium, krypton and nitrogen; the carbonization temperature is 500-800°C, the carbonization time is 1-3 hours, and the acid is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid.

[0016] Preferably, in step S3, the molybdenum source is selected from one or more of sodium molybdate, potassium molybdate, ammonium molybdate tetrahydrate and molybdenum powder;

[0017] Preferably, in step S3, the selenium source is selected from one or more of selenium powder, selenourea, selenium dioxide and sodium selenate;

[0018] Preferably, in step S3, the reducing agent is selected from one or more of sodium borohydride, hydrazine hydrate and ethylenediamine.

[0019] Preferably, in step S3, the ratio of the molar amount (mmol) of the molybdenum source to the mass (mg) of the intermediate D is 1:(70-90);

[0020] Preferably, in step S3, the molar ratio of the molybdenum source to the selenium source is 1:(1.5-2.5);

[0021] Preferably, in step S3, the concentration of the reducing agent in solution D is 80 to 120 mmol / L;

[0022] Preferably, in step S3, the temperature of the hydrothermal reaction is 120-200° C., and the time of the hydrothermal reaction is 10-14 hours.

[0023] Preferably, in step S4, during the high-temperature annealing treatment, the sulfur source is located at the upwind side of the tube furnace, and the intermediate E is located at the downwind side of the tube furnace;

[0024] Preferably, in step S4, the sulfur source is selected from one or more of thiourea, ammonium sulfide, thioacetamide and sulfur powder; and the feed mass ratio of the sulfur source to the intermediate E is (1-3):1.

[0025] Preferably, in step S4, the second protective gas is selected from at least one of argon, helium, krypton and nitrogen; the temperature of the high temperature annealing treatment is 400-600° C., and the time of the high temperature annealing treatment is 1-4 hours.

[0026] A second aspect of the present invention provides a battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode material prepared according to the preparation method provided by the first aspect of the present invention.

[0027] A third aspect of the present invention provides an electronic device, comprising the battery provided by the second aspect of the present invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The negative electrode material prepared by the preparation method provided in the present application provides more sites for the growth of molybdenum selenide sulfide nanosheets by preparing a hollow hexahedron carbon substrate (i.e., intermediate D), which can effectively prevent the agglomeration of molybdenum selenide sulfide, thereby effectively improving the structural stability of the obtained negative electrode material. The nitrogen-doped carbon substrate has high conductivity. On this basis, the prepared MoSe2 / NC (intermediate E) has a high specific surface area through a hydrothermal method, which is beneficial to the infiltration of the electrolyte of the negative electrode material and the transmission of potassium ions. It can improve the capacity contribution while ensuring the structural strength and promote electron transmission, so that the battery has a higher capacity and excellent cycle performance; in addition, by doping S atoms into the MoSe2 lattice in the intermediate E, it forms S in the negative electrode material. 2-x Se x The interlayer ligand can significantly increase the platform capacity of batteries equipped with this negative electrode material. Potassium ion batteries using the negative electrode material prepared in this application as the negative electrode active material have a stable negative electrode structure, excellent capacitance, and excellent cycle performance even at high flow densities. The preparation method of this application is simple and controllable, and can be used for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1This is a test diagram of the cycling performance of the negative electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 2 at a current density of 0.5 A / g (wherein MoSSe / NC-1 represents the negative electrode material obtained in Example 1; MoSSe / NC-2 represents the negative electrode material obtained in Example 2; MoSSe / NC-3 represents the negative electrode material obtained in Example 3; MoSe2 / NC represents the negative electrode material obtained in Comparative Example 1; MoSSe represents the negative electrode material obtained in Comparative Example 2). DETAILED DESCRIPTION

[0032] In order to make the technical solutions and beneficial effects of the present invention more obvious and easy to understand, the following is described in detail by enumerating specific embodiments. Wherein, the accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of local features. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods for which specific conditions are not specified in the following examples are generally based on conventional experimental conditions. Unless otherwise specified, the reagents and raw materials used in the present invention are all commercially available.

[0033] In the following description, numerous specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and steps described in detail.

[0034] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0035] In order to fully understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below. However, in addition to these detailed descriptions, the present application may also have other implementation methods.

[0036] Unless otherwise defined, technical and scientific terms used in this application have the same meanings as those in the technical field to which this application belongs.

[0037] In the following examples, if no specific techniques or conditions are specified, the methods are generally carried out according to conventional techniques or conditions described in the literature in the field, or according to the product instructions and the conditions recommended by the manufacturer. The numerical ranges in the following examples are all inclusive.

[0038] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0039] [Preparation of negative electrode materials]

[0040] The first aspect of the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0041] S1: dissolving zinc nitrate hexahydrate in a first solvent to obtain solution A; dissolving 2-methylimidazole in a second solvent to obtain solution B; adding solution B to solution A to obtain intermediate A;

[0042] S2: reacting the intermediate A obtained in step S1 with dopamine in the presence of a base to obtain an intermediate B, followed by carbonization under a first protective gas atmosphere to obtain an intermediate C, and then reacting in the presence of an acid to obtain an intermediate D;

[0043] S3: adding the intermediate D obtained in step S2 to water and a molybdenum source to obtain a solution C; adding a reducing agent and a selenium source to the water to obtain a solution D; adding the solution D to the solution C for a hydrothermal reaction to obtain an intermediate E;

[0044] S4: Under a second protective gas atmosphere, the sulfur source and the intermediate E obtained in step S3 are subjected to a high-temperature annealing treatment to obtain the negative electrode material.

[0045] The negative electrode material prepared by the preparation method provided in the present application provides more sites for the growth of molybdenum selenide sulfide nanosheets by preparing a hollow hexahedron carbon substrate (i.e., intermediate D), which can effectively prevent the agglomeration of molybdenum selenide sulfide, thereby effectively improving the structural stability of the obtained negative electrode material. The nitrogen-doped carbon substrate has high conductivity. On this basis, the prepared MoSe2 / NC (intermediate E) has a high specific surface area through a hydrothermal method, which is beneficial to the infiltration of the electrolyte of the negative electrode material and the transmission of potassium ions. It can improve the capacity contribution while ensuring the structural strength and promote electron transmission, so that the battery has a higher capacity and excellent cycle performance; in addition, by doping S atoms into the MoSe2 lattice in the intermediate E, it forms S in the negative electrode material. 2-x Se x The interlayer ligand can significantly increase the platform capacity of the battery equipped with the negative electrode material.

[0046] In certain embodiments, in step S1, the first solvent is selected from one or more of water, methanol, ethanol and ethylene glycol.

[0047] In certain embodiments, in step S1, the first solvent is methanol.

[0048] In certain embodiments, in step S1, the molar concentration of zinc nitrate hexahydrate in solution A is 50 to 110 mmol / L, for example, 50 mmol / L, 60 mmol / L, 70 mmol / L, 80 mmol / L, 90 mmol / L, 100 mmol / L, or 110 mmol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] In certain embodiments, in step S1, the second solvent is selected from one or more of water, methanol, ethanol and ethylene glycol, and the molar concentration of the 2-methylimidazole in solution B is 200-400 mmol / L, for example, 200 mmol / L, 220 mmol / L, 240 mmol / L, 260 mmol / L, 280 mmol / L, 300 mmol / L, 320 mmol / L, 340 mmol / L, 360 mmol / L, 380 mmol / L or 400 mmol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] In certain embodiments, in step S1, the volume ratio of solution A to solution B is 1:(0.5-2).

[0051] In certain embodiments, in step S1, the volume ratio of solution A to solution B is 1:1.

[0052] In certain embodiments, in step S1, after the step of adding solution B to solution A, the steps of stirring, standing, filtering, washing and drying are also included. In certain embodiments, the stirring time is 10 to 20 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes, but is not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable. In certain embodiments, the standing time is 20 to 28 hours, for example, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours or 28 hours, but is not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable. In certain embodiments, the washing is washing with methanol 2 to 4 times, for example, 2 times, 3 times or 4 times. In certain embodiments, the drying temperature is 60-70°C, for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In certain embodiments, in step S2, the mass ratio of the intermediate A to dopamine is (0.5-3):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable.

[0054] In certain embodiments, in step S2, the ratio of the mass (g) of the intermediate A to the volume (ml) of the base is 1:(800-1200), for example, 1:800, 1:850, 1:900, 1:950, 1:1000, 1:1050, 1:1100, 1:1150 or 1:1200, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable.

[0055] In certain embodiments, in step S2, the base is a Trizma base solution, and the pH of the Trizma base solution is 8 to 8.5.

[0056] In certain embodiments, in step S2, the dopamine is dopamine hydrochloride.

[0057] In certain embodiments, in step S2, the step of reacting the intermediate A and dopamine in the presence of a base to obtain the intermediate B is carried out under stirring conditions, and the stirring time is 10 to 14 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] In certain embodiments, in step S2, the first protective gas is selected from at least one of argon, helium, krypton, and nitrogen.

[0059] In certain embodiments, in step S2, the carbonization temperature is 500-800°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; the carbonization time is 1-3 hours, for example, 1 hour, 2 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] In certain embodiments, in step S2, the carbonization step further includes the steps of separating precipitation, washing and drying, wherein the washing step is washing with ultrapure water three times and then washing with ethanol once; the drying temperature is 55-65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] In certain embodiments, in step S2, the acid is selected from one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0062] In certain embodiments, in step S2, the concentration of the acid is 0.1 mol / L to 0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] In certain embodiments, in step S2, before the step of obtaining intermediate D, the step of stirring, filtering, washing and drying is further included, and the stirring time is 36 to 60 hours, for example, 36 hours, 40 hours, 44 hours, 48 ​​hours, 52 hours, 56 hours or 60 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; the washing is washing with ultrapure water 3 times and then washing with ethanol once; the drying temperature is 55 to 65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0064] In certain embodiments, in step S3, the ratio of the molar amount (mmol) of the molybdenum source to the mass (mg) of the intermediate D is 1:(70-90), for example, 1:70, 1:75, 1:80, 1:85 or 1:90, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable.

[0065] In certain embodiments, in step S3, the molybdenum source is selected from one or more of sodium molybdate, potassium molybdate, ammonium molybdate tetrahydrate, and molybdenum powder. In certain embodiments, in step S3, the molybdenum source is selected from sodium molybdate.

[0066] In some embodiments, in step S3, the selenium source is selected from one or more of selenium powder, selenourea, selenium dioxide, and sodium selenate. In some embodiments, in step S3, the selenium source is selected from selenium powder.

[0067] In certain embodiments, in step S3, the reducing agent is selected from one or more of sodium borohydride, hydrazine hydrate and ethylenediamine. In certain embodiments, in step S3, the reducing agent is selected from sodium borohydride.

[0068] In certain embodiments, in step S3, the molar ratio of the molybdenum source to the selenium source is 1:(1.5-2.5), for example, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable.

[0069] In certain embodiments, in step S3, the concentration of the reducing agent in solution D is 80 to 120 mmol / L, for example, 80 mmol / L, 85 mmol / L, 90 mmol / L, 95 mmol / L, 100 mmol / L, 105 mmol / L, 110 mmol / L, 115 mmol / L or 120 mmol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0070] In certain embodiments, in step S3, the temperature of the hydrothermal reaction is 120 to 200°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; the time of the hydrothermal reaction is 10 to 14 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0071] Thus, the intermediate E prepared by the hydrothermal reaction can have a higher specific surface area, which is beneficial to the infiltration of the electrolyte of the negative electrode material and the transmission of potassium ions. It can improve the capacity contribution while ensuring structural strength and promote electron transmission, so that the potassium ion battery equipped with the negative electrode material has high capacity and excellent cycle performance.

[0072] In certain embodiments, in step S3, a stirring step is further included before the hydrothermal reaction step, and the stirring time is 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0073] In certain embodiments, in step S3, after the hydrothermal reaction step, the steps of cooling, centrifugation, washing and drying are further included, wherein the cooling is cooling to room temperature; the washing is washing with ultrapure water three times and then washing with ethanol once; the drying temperature is 55-65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] In certain embodiments, in step S4, during the high-temperature annealing treatment, the sulfur source is located at the upwind side of the tube furnace, and the intermediate E is located at the downwind side of the tube furnace.

[0075] Thus, it is possible to ensure that S atoms are doped into the MoSe2 lattice in the intermediate E, thereby forming S 2-x Se x The interlayer ligand can significantly increase the platform capacity of the battery equipped with the negative electrode material.

[0076] In certain embodiments, in step S4, the sulfur source is selected from one or more of thiourea, ammonium sulfide, thioacetamide, and sulfur powder. In certain embodiments, the sulfur source is selected from thioacetamide.

[0077] In certain embodiments, in step S4, the mass ratio of the sulfur source to the intermediate E is (1-3):1, for example, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable.

[0078] In certain embodiments, in step S4, the second protective gas is selected from at least one of argon, helium, krypton, and nitrogen.

[0079] In certain embodiments, in step S4, the temperature of the high temperature annealing treatment is 400-600°C, for example, 400°C, 450°C, 500°C, 550°C or 600°C, but is not limited to the listed ratios, and other ratios not listed within the ratio range are also applicable; the time of the high temperature annealing treatment is 1-4 hours, for example, 1 hour, 2 hours, 3 hours or 4 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0080] When the annealing and sulfurization temperature is within the above range, the material can be smoothly carbonized and excessive defects in the material caused by the high annealing temperature can be prevented, resulting in a lack of stability in the material structure, thereby avoiding expansion of the material structure when potassium ions are inserted and removed, thereby affecting the cycle performance of the material. The potassium ion battery equipped with the negative electrode material prepared by the preparation method of the present application has extremely high stability and excellent electrochemical performance.

[0081] [Battery]

[0082] A second aspect of the present invention provides a battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode material prepared according to the preparation method provided by the first aspect of the present invention.

[0083] In certain embodiments, the battery may be a secondary battery or a primary battery, preferably a secondary battery. For example, the battery may be a potassium ion battery, but is not limited thereto. The battery structure of the present application includes but is not limited to a soft-pack potassium ion battery, a square hard-shell battery, or a cylindrical hard-shell battery.

[0084] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator, with the separator positioned between the two electrodes. During the battery's charge and discharge processes, active ions are inserted and removed from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0085] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector can be aluminum foil, copper foil, titanium foil, nickel foil, iron foil, zinc foil, etc. The negative electrode active material layer includes a negative electrode active material. In the present invention, the negative electrode active material is the negative electrode material prepared according to the preparation method provided in the first aspect of the present invention.

[0086] The negative electrode active material layer may further include one or two selected from a conductive agent and a binder. The conductive agent is used to improve the conductivity of the electrode. Examples of negative electrode conductive agents include conductive carbon black, conductive graphite, vapor deposited carbon fiber (VGCF), carbon nanotubes, graphene, etc. The binder of the negative electrode improves the bonding performance between the negative electrode active material particles and between the negative electrode active material particles and the current collector. Examples of negative electrode binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), cyclodextrin, gelatin, polyvinyl alcohol, polyacrylate, acrylonitrile multipolymer, etc. The mass ratio of each component in the negative electrode active material layer can be conventional.

[0087] This application does not particularly limit the preparation method of the negative electrode sheet. Any preparation method known in the art may be used, as long as the purpose of this application can be achieved. For example, the preparation method of the negative electrode sheet includes, but is not limited to, the following steps: dispersing the negative electrode active material, conductive agent, and binder in a solvent and mixing them to form a uniform negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector; and drying, cold pressing, cutting, slitting, and re-drying to obtain the negative electrode sheet. The solvent for the negative electrode slurry can be a conventional solvent in the art, such as deionized water.

[0088] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode current collector can be aluminum foil, copper foil, titanium foil, nickel foil, iron foil, zinc foil, etc. The positive electrode active material layer includes a positive electrode active material. Positive electrode active materials suitable for the present invention can be various known positive electrode active materials that can be used in potassium ion batteries, as long as they can reversibly intercalate and deintercalate potassium ions.

[0089] The positive electrode active material layer may further include one or two selected from a conductive agent and a binder. The conductive agent is used to improve the conductivity of the electrode. Examples of the positive electrode conductive agent include one or more of conductive carbon black, carbon fiber (CF), acetylene black, Ketjen black, graphene, carbon nanotubes and carbon microspheres. The positive electrode binder improves the bonding performance between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of the positive electrode binder include at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, a rubber-type binder and a polyimide-type binder. The mass ratio of each component in the positive electrode active material layer can be conventional.

[0090] The present application does not particularly limit the preparation method of the positive electrode sheet. Any preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the positive electrode sheet includes but is not limited to the following steps: dispersing the positive electrode active material, the conductive agent, and the binder in a solvent and mixing them to form a uniform positive electrode slurry, coating the positive electrode slurry on the positive electrode current collector, drying, cold pressing, cutting, slitting, and re-drying to obtain the positive electrode sheet. The solvent of the positive electrode slurry can be a conventional solvent in the art, such as N-methylpyrrolidone (NMP).

[0091] The separator can be a polymer porous separator, an inorganic porous separator or a polymer-inorganic composite porous separator. The polymer porous separator includes a single-layer polymer porous separator and a multi-layer polymer porous separator.

[0092] The electrolyte typically comprises a solvent and a potassium salt. The electrolyte suitable for the present invention may be conventional, for example, the solvent may be one or more selected from dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or 1,4-butyl propyl ester, more preferably one or more of PC, EC and EMC. The potassium salt may be selected from one or more of potassium hexafluorophosphate (KPF6), potassium perchlorate (KClO4), potassium bis(oxalatoborate) (KBOB), potassium difluorooxalatoborate (KDFOB), potassium tetrafluoroborate (KBF4), potassium bis(trifluoromethylsulfonyl imide) (KTFSI) and potassium bis(fluorosulfonyl imide) (KFSI).

[0093] The battery of the present application also includes a packaging shell for accommodating the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components known in the art for potassium ion batteries. This application does not limit these other components. This application does not particularly limit the packaging shell, and can be any packaging shell known in the art, as long as it can achieve the purpose of this application.

[0094] It should be understood that since the battery provided in the present application includes a negative electrode plate, and the negative electrode plate includes a negative electrode material prepared by the preparation method provided by the first aspect of the present invention, the beneficial effects of the preparation method of the negative electrode material described in any of the above embodiments are applicable to the battery.

[0095] [Electronic devices]

[0096] A third aspect of the present invention provides an electronic device, comprising the battery provided by the second aspect of the present invention.

[0097] The use of the battery of the present application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the battery of the present application can be used for, but is not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, drones, and potassium ion capacitors.

[0098] It should be understood that, since the electronic device provided in the present application includes the battery described in the second aspect of the present invention, the beneficial effects of the method for preparing the negative electrode material described in any of the above embodiments are applicable to the electronic device.

[0099] The method of the present invention is described below by means of specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples. The implementation conditions adopted in the examples can be further adjusted according to specific requirements. The implementation conditions not specified are generally the conditions in routine experiments.

[0100] Example 1

[0101] The preparation method of the MoSSe / NC negative electrode material of Example 1 comprises the following steps:

[0102] Step S101: 8 mmol (2.38 g) of zinc nitrate hexahydrate was dissolved in 100 mL of methanol to obtain solution A; 30 mmol (2.46 g) of 2-methylimidazole was dissolved in 100 mL of methanol to obtain solution B; solution B was rapidly added to solution A, stirred for 15 minutes, and then allowed to stand for 24 hours, filtered, washed with methanol three times, and dried at 65° C. to obtain hexadecahedral ZIF-8 (i.e., intermediate A);

[0103] Step S102: 0.1 g of ZIF-8 obtained in step S101 and 0.05 g of dopamine hydrochloride were stirred in 100 mL of Trizma base solution (pH 8-8.5) for 12 h to coat the surface of ZIF-8 with dopamine, thereby obtaining ZIF-8@PDA (i.e., intermediate B); the precipitate was separated, washed three times with ultrapure water, washed once with ethanol, and dried at 60° C., and carbonized at 650° C. under an Ar atmosphere for 2 h to obtain ZIF-8@NC (i.e., intermediate C); ZIF-8@NC was dispersed in 0.1 M hydrochloric acid, stirred for 48 h to remove ZIF-8, washed three times with ultrapure water, washed once with ethanol, and dried at 60° C. to obtain an N-doped hollow hexadecahedral carbon substrate NC (i.e., intermediate D);

[0104] Step S103: Disperse 40 mg of the NC obtained in step S102 in 20 mL of deionized water, add 0.5 mmol of sodium molybdate, and stir until uniform, obtaining solution C. Slowly add 2 mmol of sodium borohydride powder and then 1 mmol of Se powder to 20 mL of deionized water to obtain solution D. Solution D is slowly added to solution C, stirred for 30 minutes, and then transferred to an autoclave, heated at 160°C for 12 hours, cooled to room temperature, and centrifuged. The product is washed three times with ultrapure water and once with ethanol, and then dried at 60°C to obtain N-doped hollow hexadecahedral MoSe2 / NC (i.e., intermediate E).

[0105] Step S104: Place a porcelain boat containing thioacetamide (300 mg) at the upwind side of a tube furnace, and place a porcelain boat containing MoSe2 / NC (200 mg) at the downwind side of the tube furnace. Anneal at 500°C for 3 h in a N2 atmosphere to obtain N-doped hollow hexadecahedral MoSSe / NC (i.e., negative electrode material).

[0106] Example 2

[0107] The only difference between Example 2 and Example 1 is that in step S102 , the amount of dopamine hydrochloride added is 0.1 g; and in step S103 , the amount of NC added is 60 mg.

[0108] Example 3

[0109] The only difference between Example 3 and Example 1 is that in step S104 , the temperature of high-temperature annealing is 700° C.

[0110] Comparative Example 1

[0111] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not include step S104, and the MoSe2 / NC material obtained in step S103 is directly used as the negative electrode material.

[0112] Comparative Example 2

[0113] The preparation method of the MoSSe negative electrode material of Comparative Example 2 comprises the following steps:

[0114] Step S101*: Add 0.5 mmol of sodium molybdate to 20 mL of deionized water and stir until evenly mixed to form Solution A. Slowly add 2 mmol of sodium borohydride powder to 20 mL of deionized water, followed by 1 mmol of Se powder. This solution is referred to as Solution B. Slowly add Solution B to Solution A, stir for 30 minutes, and then transfer to an autoclave, heat at 160°C for 12 hours, cool to room temperature, centrifuge the product, wash, and dry to obtain MoSe2.

[0115] Step S102*: Place a porcelain boat containing thioacetamide (300 mg) on ​​the upwind side of a tube furnace, and place a porcelain boat containing MoSe2 / NC (200 mg) on ​​the downwind side of the tube furnace. Anneal at 500°C for 3 h in a N2 atmosphere to obtain MoSSe.

[0116] Electrochemical performance test

[0117] Preparation of potassium ion batteries:

[0118] (1) Preparation of negative electrode sheet: The negative electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were used as negative electrode active materials, Ketjen black was used as a conductive agent, and carboxymethyl cellulose was used as a binder. The mixture was mixed in a ratio of negative electrode active material: conductive agent: binder = 7:2:1 and fully ground. Deionized water was added as a solvent and further ground to obtain a uniform slurry. The slurry was coated on a copper foil current collector, vacuum dried at 80°C for 12 hours, and cut into circular electrode sheets using a punching machine.

[0119] (2) Preparation of positive electrode: Use metallic potassium sheet as positive electrode;

[0120] (3) Diaphragm: GF / A glass fiber diaphragm is used as the diaphragm;

[0121] (4) Electrolyte: The electrolyte is 1 mol / L potassium bis(fluorosulfonyl)imide (KFSI) dissolved in ethylene carbonate and diethyl carbonate at a volume ratio of 1:1 (EC:DEC, volume ratio 1:1);

[0122] (5) Battery assembly: The potassium ion half-cell uses a CR-2032 battery shell, which is assembled in the order of negative electrode sheet, separator, and positive electrode sheet, and is soaked in electrolyte. The half-cell is assembled in an argon glove box.

[0123] Performance tests were conducted on CR2032 button batteries using the negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 as the negative electrode active material. (The batteries were left for at least 16 hours after preparation before testing.)

[0124] 1. Cyclic specific capacity and coulombic efficiency test at a current density of 0.5A / g: Using the Land battery test system, at a constant temperature of 25°C, discharge to 0V at a current density of 0.5A / g, and continue to charge to 3V at a constant current of 0.5A / g. This is a complete charge and discharge cycle, recorded as cycle 1; repeat this process until the number of cycles is equal to 500, and then end the test. The discharge capacity of the nth cycle is the specific capacity after the nth cycle, and the discharge specific capacity of the nth cycle / the charging specific capacity of the nth cycle = coulombic efficiency. The test results after 500 cycles are shown in Table 1, and the cycle performance test diagram is shown in Figure 1. Figure 1 (n is an integer between 1 and 500)

[0125] Table 1

[0126] Example Number of cycles Specific capacity after cycle (mAh / g) Coulombic efficiency (%) Example 1 500 483.2 99.8 Example 2 500 397.3 99.7 Example 3 500 351.2 99.7 Comparative Example 1 500 399.9 98.4 Comparative Example 2 500 88.6 97.3

[0127] Combine Figure 1 As can be seen from Table 1, the batteries using the negative electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 as the negative electrode active material undergo an irreversible reaction in the first cycle at a current density of 0.5 A / g to form a stable SEI film; in the subsequent cycles, the capacity generally shows a relatively stable trend, and the coulombic efficiency after 500 cycles is 99.7% to 99.8% for Examples 1 to 3, 98.4% for Comparative Example 1, and 97.3% for Comparative Example 2.

[0128] The negative electrode material in Example 1 exhibited an excellent specific capacity of 483.2 mAh / g after 500 cycles. This is because MoSSe grows uniformly in the shape of nanosheets on the surface of the hexahedral hollow carbon substrate NC. This special structure can effectively prevent the agglomeration of molybdenum selenide sulfide and improve the stability of the structure. In addition, high-temperature heat treatment gives it suitable defects, which is conducive to the transmission of electrons / ions, and has a higher capacity and excellent cycle performance.

[0129] Compared with Example 1, the hexahedral hollow carbon substrate NC in Example 2 is thicker, making it closer to a sphere. The difference in shape and the increase in the carbon substrate make the capacity of the MoSSe / NC negative electrode material slightly lower than that in Example 1.

[0130] Compared with Example 1, a higher annealing and sulfurization temperature is used in Example 3, which results in too many defects in the material and causes the material structure to be less stable than that in Example 1. + The material structure expands during embedding and unembedding, and the cycle curve begins to decay after 300 cycles.

[0131] The capacity of the hollow hexadecahedral MoSe2 / NC in Comparative Example 1 decreased by 20.8% after 500 cycles, which indicates that the material in Example 1 doped S atoms into the MoSe2 lattice to form S 2-x Se x Interlayer ligands can give it a higher capacity.

[0132] In Comparative Example 2, the capacity of MoSSe without a carbon substrate decays rapidly in the early stages of cycling. This is because the volume expands significantly during the cycling process, resulting in structural collapse.

[0133] 2. Specific capacity and coulombic efficiency test after cycling at a current density of 10A / g: Using the Land battery test system, at a constant temperature of 25°C, discharge to 0V at a current density of 10A / g, and continue to charge to 3V at a constant current of 10A / g. This is a complete charge and discharge cycle, recorded as cycle 1. Repeat this process until the number of cycles is equal to 2000, and then end the test. The discharge capacity of the 2000th cycle is the specific capacity after the 2000th cycle, and the discharge specific capacity of the 2000th cycle / the charge specific capacity of the 2000th cycle = coulombic efficiency. The test results are shown in Table 2.

[0134] Table 2

[0135]

[0136]

[0137] As can be seen from Table 2, the battery using the negative electrode material prepared in Example 1 as the negative electrode active material also exhibits excellent cycling stability at a high current density of 10 A / g. After 1000 cycles, its specific capacity is 235.7 mAh / g (an increase of 28.6% over Comparative Example 1 and 453.3% over Comparative Example 2), and its coulombic efficiency is 99.8%. This demonstrates that the negative electrode material in Example 1 has a high capacity and excellent cycling performance during cycling.

[0138] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the claims. Various modifications and variations may be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form additional embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments merely illustrate several implementations of the present invention and do not limit the scope of protection of the patent of this invention.

Claims

1. A method for preparing a negative electrode material, characterized in that: The steps include: S1: dissolving zinc nitrate hexahydrate in a first solvent to obtain solution A; dissolving 2-methylimidazole in a second solvent to obtain solution B; adding solution B to solution A to obtain intermediate A; S2: reacting the intermediate A obtained in step S1 with dopamine in the presence of a base to obtain an intermediate B, followed by carbonization in a first protective gas atmosphere to obtain an intermediate C, and then reacting in the presence of an acid to obtain an intermediate D; S3: adding the intermediate D obtained in step S2 into water and a molybdenum source to obtain a solution C; Add a reducing agent and a selenium source to water to obtain solution D; Add solution D to solution C for hydrothermal reaction to obtain intermediate E; S4: Under the second protective gas atmosphere, the sulfur source and the intermediate E obtained in step S3 are subjected to high temperature annealing treatment to obtain the negative electrode material.

2. The preparation method according to claim 1, characterized in that: In step S1, the first solvent is selected from one or more of water, methanol, ethanol and ethylene glycol, and the molar concentration of zinc nitrate hexahydrate in solution A is 50-110 mmol / L; the second solvent is selected from one or more of water, methanol, ethanol and ethylene glycol, and the molar concentration of 2-methylimidazole in solution B is 200-400 mmol / L.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of the intermediate A to dopamine is (0.5-3):1; the base is a Trizma base solution, and the pH of the Trizma base solution is 8-8.5; Preferably, the dopamine is dopamine hydrochloride.

4. The preparation method according to claim 1, characterized in that: In step S2, the first protective gas is selected from at least one of argon, helium, krypton and nitrogen; the carbonization temperature is 500-800°C, the carbonization time is 1-3 hours, and the acid is selected from one or more of hydrochloric acid, sulfuric acid and nitric acid.

5. The preparation method according to claim 1, characterized in that: In step S3, the molybdenum source is selected from one or more of sodium molybdate, potassium molybdate, ammonium molybdate tetrahydrate and molybdenum powder; the selenium source is selected from one or more of selenium powder, selenourea, selenium dioxide and sodium selenate; and the reducing agent is selected from one or more of sodium borohydride, hydrazine hydrate and ethylenediamine.

6. The preparation method according to claim 1, characterized in that: In step S3, the ratio of the molar amount (mmol) of the molybdenum source to the mass (mg) of the intermediate D is 1:(70-90); the molar ratio of the molybdenum source to the selenium source is 1:(1.5-2.5); the concentration of the reducing agent in solution D is 80-120 mmol / L; the temperature of the hydrothermal reaction is 120-200°C, and the time of the hydrothermal reaction is 10-14 hours.

7. The preparation method according to claim 1, characterized in that: In step S4, during the high temperature annealing treatment, the sulfur source is located at the upper air port of the tubular furnace, and the intermediate E is located at the lower air port of the tubular furnace; the sulfur source is selected from one or more of thiourea, ammonium sulfide, thioacetamide and sulfur powder; the feed mass ratio of the sulfur source to the intermediate E is (1-3):

1.

8. The preparation method according to claim 1, characterized in that: In step S4, the second protective gas is selected from at least one of argon, helium, krypton and nitrogen; the temperature of the high temperature annealing treatment is 400-600° C., and the time of the high temperature annealing treatment is 1-4 hours.

9. A battery, characterized in that: The battery comprises a negative electrode plate, and the negative electrode plate comprises a negative electrode material prepared by the preparation method according to any one of claims 1-8.

10. An electronic device, characterized in that: The electronic device comprises the battery as claimed in claim 9.

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