Lithium replenisher and its manufacturing method, positive electrode sheet and secondary battery

Abstract

The present invention provides a lithium replenisher, a method for manufacturing the same, a positive electrode sheet, a secondary battery, and a power consumption device. [Solution] The lithium replenisher comprises a sulfide composite material, the sulfide composite material comprising a first sulfide and a second sulfide doped with the first sulfide, the first sulfide comprising lithium sulfide, and the second sulfide being at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides. This invention is advantageous in solving the problem in related art that lithium replenishment to the positive electrode tends to generate gas, resulting in low lithium replenishment effectiveness and being disadvantageous for effectively improving the overall performance of the battery.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority based on a Chinese patent application filed with the China National Intellectual Property Office on October 16, 2024, with application number 2024114492132, titled "Lithium Replenisher and Method for Manufacturing the Same, Cathode Sheet and Secondary Battery," and a Chinese patent application filed with the China National Intellectual Property Office on November 29, 2024, with application number 2024117482950, ​​titled "Lithium Replenisher and Method for Manufacturing the Same, Cathode Sheet and Secondary Battery," and incorporates the entire contents of those applications by reference.

[0002] This invention relates to the technology of energy storage, and more specifically to lithium replenishment agents and methods for producing the same, as well as to positive electrode sheets and secondary batteries. [Background technology]

[0003] Lithium-ion batteries are widely used in new energy fields, such as batteries for new energy vehicles. During the charging and discharging process of lithium-ion batteries, a certain amount of positive electrode active lithium is irreversibly consumed on the negative electrode surface to form an SEI (solid electrolyte interface) film, which leads to problems such as low initial cycle efficiency and short cycle life.

[0004] Currently, the primary method for improving initial cycle efficiency is pre-lithiumization or the addition of lithium replenishers. Common lithium replenishment methods mainly involve lithium replenishment to the positive electrode and lithium replenishment to the negative electrode. Lithium replenishment to the negative electrode often uses lithium powder or lithium foil as the replenisher, which can easily cause safety problems. Lithium replenishment to the positive electrode often uses lithium-rich compounds or binary lithium compounds as the replenisher, which can be added directly to the slurry mixing process, making it easy to handle, safe, and currently a focus of attention.

[0005] However, current lithium replenishment methods for the positive electrode have problems such as the tendency to generate gas and the low effectiveness of lithium replenishment, making them unfavorable for effectively improving the overall performance of the battery. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In view of the technical problems present in the background technology, this application provides a lithium replenisher, a method for manufacturing the same, a positive electrode sheet, a secondary battery, and a power consumption device in order to solve the problem that the overall performance of batteries cannot be effectively improved in related technologies. [Means for solving the problem]

[0007] According to the first aspect, the embodiment of the present application provides a lithium replenisher comprising a sulfide composite material, wherein the sulfide composite material comprises a first sulfide and a second sulfide doped with the first sulfide, the first sulfide comprising lithium sulfide, and the second sulfide comprising at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides.

[0008] In the technical means of the embodiments of the present application, the lithium sulfide in the lithium replenisher is used for lithium replenishment, and after the lithium is removed, the remaining sulfur combines with a secondary sulfide to form, for example, a polysulfide, thereby avoiding the formation of elemental sulfur after the lithium is removed from the lithium sulfide, reducing the amount of elemental sulfur dissolved in the electrolyte, reducing the amount of elemental sulfur that passes through the separator and accumulates on the negative electrode or the separator, further reducing the effect of residual elemental sulfur on the battery performance, improving the stability of the battery performance, and effectively improving the overall performance of the battery.

[0009] In some embodiments, the metal sulfide comprises at least one of sodium sulfide, calcium sulfide, and potassium sulfide, and / or The organic sulfide comprises at least one of ammonium sulfide, sodium dithiocarbamate, and potassium dithiocarbamate, and / or In the sulfide composite material, the mass ratio of the first sulfide to the second sulfide is (60-80):(15-30) and / or In the sulfide composite material, the molar ratio of sulfur elements in the second sulfide to the first sulfide is (0.1~0.31):(1.0~1.1).

[0010] In this embodiment, the effects of lithium replenishment and sulfur fixation can be achieved simultaneously by controlling the mass ratio of the first sulfide to the second sulfide to (60-80):(15-30) and / or controlling the molar ratio of sulfur elements in the second sulfide to the first sulfide to (0.1-0.31):(1.0-1.1).

[0011] In some embodiments, the lithium replenisher further comprises a carbon coating layer applied to the surface of a sulfide composite material, wherein the mass proportion of the carbon coating layer in the lithium replenisher is 5% to 10%.

[0012] In this embodiment, the electron conduction efficiency of the lithium replenisher can be effectively improved by coating the sulfide composite material with a carbon coating layer. By controlling the mass ratio of the carbon coating layer to 5% to 10%, the electron conduction efficiency can be effectively improved without affecting lithium ion transport.

[0013] In some embodiments, the D50 particle size of the lithium replenisher is 3 μm to 12 μm, and / or the specific surface area of ​​the lithium replenisher is 2 m². 2 / g~10m 2 It is / g.

[0014] In this embodiment, the D50 particle size and specific surface area of ​​the lithium replenisher are both within an appropriate range, thereby enabling the lithium replenisher to have a high compressive density and improve energy density.

[0015] According to the second aspect, the embodiments of the present application are mixing a first lithium source and a first sulfur source and performing a first reaction treatment to obtain a first reaction solution; mixing the first reaction solution with a reducing agent, a pH adjuster, and a second sulfide to obtain a mixed solution, and performing a first purification treatment to obtain a sulfide composite material, wherein the first reaction solution contains a first sulfide, the first sulfide contains lithium sulfide, and the second sulfide is at least one selected from the group consisting of metal sulfides and organic sulfides other than lithium sulfide, and a method for manufacturing a lithium supplement is provided.

[0016] In the technical means of the embodiments of the present application, by combining a second sulfide and a first sulfide, the sulfide composite material can be manufactured, and the manufacturing method is simple and easy to implement.

[0017] In some embodiments, the step of the first purification treatment includes concentrating the mixed solution to obtain crystals of the first sulfide and the second sulfide, and / or The method for manufacturing the lithium supplement further includes a step of solid-liquid separation of the material after crystallization, washing the separated solid material, and performing a drying treatment, and / or The method for manufacturing the lithium supplement further includes a step of mixing a carbon material and a sulfide composite material and performing a second reaction treatment to manufacture a lithium supplement, and / or The second reaction treatment includes polishing and calcination, the polishing time is 1 hour to 2 hours, the calcination is performed in a protective atmosphere, the calcination temperature is 200°C to 300°C, and the time is 5 hours to 8 hours.

[0018] In this embodiment, when the first purification process is simple, easy to implement, and low in cost, the purity of the sulfide composite material can be improved. By separating the solid and liquid of the material after crystallization, washing the separated solid material, and performing a drying process, a mixed crystal material of high-purity first sulfide and second sulfide can be obtained. By mixing the carbon material and the sulfide composite material and performing a second reaction process, the lithium supplement can be produced. Further, processes such as the solid-liquid separation, washing, drying, and second reaction process are simple, a sulfide composite material of high purity can be produced, and a lithium supplement with improved product quality can be obtained. By polishing and calcining, on the one hand, further fusion of the sulfide composite material can be promoted, and a more uniformly mixed sulfide composite material can be obtained. On the other hand, the sulfide composite material can be coated with a carbon material, and a carbon coating layer can be formed on the surface of the sulfide composite material after calcination, and the electron conduction efficiency of the lithium supplement can be improved. By performing calcination in a protective atmosphere, the humidity and oxygen content during calcination can be further controlled, and the purity of the obtained lithium supplement can be improved.

[0019] In some embodiments, the method for manufacturing the lithium supplement is (1) The temperature of the first reaction process is 30°C to 60°C, and the time is 30 min to 60 min; (2) The concentration is vacuum concentration, the temperature of the concentration is 50°C to 80°C, and / or the Baumé degree of the concentrated liquid after concentration is 45 to 50; (3) Conditions for cooling the concentrated liquid to obtain crystals of the first sulfide and the second sulfide; (4) The mass ratio when mixing the sulfide composite material and the carbon material satisfies at least one of the conditions of (90 to 95):(5 to 10).

[0020] In this embodiment, controlling the temperature of the first reaction treatment to 30°C to 60°C and the time to 30 min to 60 min improves the reaction rate between the first sulfur source and the first lithium source, which is advantageous for thoroughly reacting the first sulfur source and the first lithium source. Vacuum concentration improves the concentration rate, effectively lowers the concentration temperature, and is advantageous for reducing damage to the sulfide composite material due to high temperatures. At the same time, controlling the concentration temperature and the Baumé degree of the concentrated solution after concentration, and allowing the first and second sulfides to crystallize by cooling, improves the crystallization rate of the first and second sulfides, and is advantageous for thoroughly crystallizing the first and second sulfides and reducing the precipitation of impurities.

[0021] In some embodiments, the method for producing the lithium replenisher is as follows: (1) The first lithium source comprises at least one of lithium sulfate, lithium oxalate, and lithium carbonate, and the first sulfur source comprises at least one of barium sulfide and calcium sulfide, (2) The purity of both the first lithium source and the first sulfur source shall be 99.5% or higher. (3) The content of magnetic foreign matter in the first lithium source and the first sulfur source shall be less than 1 ppm. (4) The reducing agent is provided under conditions that include at least one of hydrazine hydrate and sulfite. (5) The pH adjuster contains a hydroxide, and the hydroxide is selected from the hydroxides of metals corresponding to metal sulfides other than lithium hydroxide and / or lithium sulfide. (6) The carbon material satisfies at least one of the following conditions, including CNTs and / or graphene.

[0022] In this embodiment, by using the above-mentioned first sulfur source and first lithium source, barium sulfate precipitate, barium oxalate and / or barium carbonate precipitate can be obtained, thereby reducing impurities in the first reaction solution and controlling the purity of both the first lithium source and the first sulfur source to 99.5% or higher, which is advantageous in reducing the impurity content and improving the purity of the lithium replenisher. The content of magnetic foreign matter in the first lithium source and the first sulfur source can be controlled to less than 1 ppm, reducing the introduction of magnetic foreign matter and reducing the problem of battery performance degradation due to magnetic foreign matter when the lithium replenisher is applied to a battery. The presence of a reducing agent and hydroxide is advantageous in purifying the first and second sulfides and reducing impurities. At the same time, the addition of hydroxide is advantageous in suppressing the hydrolysis of the first and second sulfides, and the addition of a reducing agent is advantageous in effectively avoiding the oxidation of sulfur ions, thereby maintaining the stability of the performance of the first and second sulfides in the sulfide composite material. The generation of nitrogen gas when hydrazine hydrate is reacted as a reducing agent is advantageous in avoiding the introduction of new impurities into the sulfide composite material, and the pH adjuster is a hydroxide, which is advantageous in effectively suppressing the hydrolysis of the corresponding metal sulfide and / or lithium sulfide.

[0023] According to a third aspect, an embodiment of the present application provides a positive electrode sheet comprising a current collector and a positive electrode material comprising a lithium replenisher as described in the first aspect, provided on at least one side in the thickness direction of the current collector.

[0024] In this embodiment, the positive electrode sheet contains the lithium replenisher, and therefore has the advantages of a lithium replenisher.

[0025] According to the fourth aspect, an embodiment of the present application provides a secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator as described in the third aspect.

[0026] In this embodiment, the secondary battery includes the positive electrode sheet, and therefore has the advantages of a positive electrode sheet.

[0027] The above description is merely an outline of the technical means of the present application. In order to provide a clearer understanding of the technical means of the present application and to enable implementation in accordance with the contents of the specification, as well as to make the above and other objectives, features and advantages of the present application clearer and easier to understand, specific embodiments of the present application are given below.

[0028] To more clearly explain the technical means of the present application, the drawings used in the present application are briefly described below. As will be apparent, the drawings in the following description are only a few embodiments of the present application, and those skilled in the art can obtain other drawings based on these without any creative work. [Brief explanation of the drawing]

[0029] [Figure 1] This is a flowchart of the method for manufacturing a lithium replenisher according to the embodiment of the present invention. [Modes for carrying out the invention]

[0030] The following embodiments of the technical means of the present application will be described in detail with reference to the drawings. The following embodiments are used solely for illustrative purposes and not to limit the scope of protection of the present application, as they are used solely to illustrate the technical means of the present application more clearly.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as that ordinarily understood by a person skilled in the art of this application, and the terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. The terms “including” and “having” and their variations in the description of the drawings herein are intended to cover non-exclusive inclusion.

[0032] In the description of the embodiments of this application, the technical terms "first," "second," etc., are merely used to distinguish different subjects and should not be understood as indicating or implying relative importance, or implicitly indicating the number, specific order, or hierarchical relationship of the indicated technical features. In the description of the embodiments of this application, "plural" means two or more unless explicitly and specifically limited.

[0033] In this specification, “Examples” means that certain features, structures, or properties described in relation to an Example may be included in at least one Example of the Application. The use of this term in various places in this specification does not necessarily refer to the same Example, nor are they mutually exclusive or alternative to other Examples. Those skilled in the art will understand, both expressly and implicitly, that the Examples described herein may be combined with other Examples.

[0034] In the description of the embodiments of this application, the term "and / or" is merely a relational relationship that describes related objects, indicating that there are three types of relationships. For example, A and / or B can indicate that there are three types of situations: A alone, both A and B, and B alone. In addition, the letter " / " in this specification generally indicates that the related objects before and after it have an "or" relationship.

[0035] In the description of the embodiments of this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more sets (including two sets), and "multiple sheets" means two or more sheets (including two).

[0036] In the description of the embodiments of this application, the orientations or positional relationships indicated by technical terms such as "center," "vertical direction," "horizontal direction," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," "axial direction," "radial direction," and "circumferential direction" are the orientations or positional relationships shown in the drawings and are used only to facilitate or simplify the explanation of the embodiments of this application. It should be understood that these terms do not necessarily indicate or imply that the shown devices or parts have a specific orientation or have a specific directional structure and operation, and therefore should not be interpreted as limiting the embodiments of this application.

[0037] In the description of the embodiments of this application, unless otherwise specifically defined and limited, technical terms such as “attachment,” “connection,” and “connection” should be understood in a broad sense. For example, these may be fixed connections, detachable connections, integral connections, mechanical connections, electrical connections, direct connections, indirect connections via an intermediate medium, internal communication between two members, or interaction relationships between two members. Those skilled in the art will be able to understand the specific meaning of these terms in the embodiments of this application depending on the specific circumstances.

[0038] In general lithium replenishment materials for positive electrodes, lithium-rich compounds, such as lithium-rich lithium ironate and lithium-rich lithium nickelate, are all expensive, have poor air stability, are complex to manufacture, and tend to generate gases and residues, making it difficult to effectively improve the overall performance of the battery.

[0039] To solve the above technical problems, this application provides a lithium replenisher, a method for producing the same, a positive electrode sheet, and a secondary battery. The lithium sulfide in the lithium replenisher is used for lithium replenishment, and after the lithium is removed from the lithium sulfide, the remaining sulfur combines with a second sulfide to form, for example, a polysulfide, thereby preventing the formation of elemental sulfur after the lithium is removed from the lithium sulfide, reducing the amount of elemental sulfur dissolved in the electrolyte, reducing the amount of elemental sulfur that passes through the separator and accumulates on the negative electrode or the separator, further reducing the effect of residual elemental sulfur on the battery performance, improving the stability of the battery performance, and effectively improving the overall performance of the battery.

[0040] The power consumption devices according to the embodiments of this application may be, but are not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, electric bicycles, electric automobiles, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric boat toys and electric airplane toys, and spacecraft may include airplanes, rockets, spacecraft and spaceships, etc.

[0041] According to a first aspect, the embodiments of the present application provide a lithium supplement comprising a sulfide composite material, the sulfide composite material comprising a first sulfide and a second sulfide doped with the first sulfide. The first sulfide comprises lithium sulfide, and the second sulfide is at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides.

[0042] The second sulfide comprises at least one of metal sulfides other than lithium sulfide and organic sulfides, and the second sulfide may be any sulfide that can bind to the sulfur after delithiation of lithium sulfide and fix the sulfur (e.g., elemental sulfur) after delithiation of the sulfide, thereby preventing the elemental sulfur after delithiation of lithium sulfide from dissolving or accumulating on the separator.

[0043] The principle by which disulfides fix sulfur after lithium sulfide has been delithiated is explained below.

[0044] When the lithium replenisher according to the embodiment of the present application is used as the positive electrode material, the lithium sulfide in the lithium replenisher is used for lithium replenishment, and after the lithium is removed, the remaining sulfur can combine with a second sulfide, for example, to form a polysulfide. This prevents the formation of elemental sulfur after the lithium is removed from the lithium sulfide, and by utilizing the characteristic that the solubility of the product after sulfur has combined with the second sulfide in the electrolyte is weaker than the solubility of elemental sulfur in the electrolyte, for example, the polysulfide is difficult to dissolve in the electrolyte and does not pass through the separator and accumulate on the negative electrode or the separator, and elemental sulfur does not dissolve in the electrolyte and pass through the separator and accumulate on the negative electrode or the separator. Furthermore, the impact of residual elemental sulfur on the battery performance is reduced, the stability of the battery performance is improved, and the overall battery performance can be effectively improved.

[0045] In some embodiments, the metal sulfide comprises at least one of sodium sulfide, calcium sulfide, and potassium sulfide, and / or the organic sulfide comprises at least one of ammonium sulfide, sodium dithiocarbamate, and sodium potassium dithiocarbamate.

[0046] In some embodiments, the mass ratio of the first sulfide to the second sulfide in the sulfide composite material is (60-80):(15-30). Exemplary mass ratios of the first sulfide to the second sulfide are 60:15, 60:18, 60:20, 60:23, 60:25, 60:28, 60:30, 65:16, 65:17, 65:20, 65:22, 65:25, 65:28, 65:30, 70:15, 70:18, 70:20, 70:23, 70:25, 70:29, 70:30, 75:15, 75:17, 75:20, 75:22, 75:25, 75:28, 75:30, 80:15, 80:17, 80:21, 80:24, 80:25, 80:28, or 80:30.

[0047] In these examples, the effects of lithium replenishment and sulfur fixation can be achieved simultaneously by controlling the mass ratio of the first sulfide to the second sulfide to (60-80):(15-30).

[0048] In some embodiments, the molar ratio of sulfur elements in the second sulfide to the first sulfide in the sulfide composite material is (0.1~0.31):(1.0~1.1). Illustratively, the molar ratio of sulfur elements in the second sulfide to the first sulfide may be 0.1:1.0, 0.2:1.0, 0.3:1.0, 0.1:1.1, 0.2:1.1, 0.3:1.1, or 0.31:1.1.

[0049] In these examples, the effects of lithium replenishment and sulfur fixation can be achieved simultaneously by controlling the molar ratio of sulfur elements in the disulfide to the primordial sulfide to (0.1~0.31):(1.0~1.1).

[0050] In some embodiments, the lithium replenisher further comprises a carbon coating layer applied to the surface of the sulfide composite material.

[0051] In these embodiments, the electron conduction efficiency of the lithium replenisher can be effectively improved by coating the sulfide composite material with a carbon coating layer.

[0052] In some embodiments, the mass percentage of the carbon coating layer in the lithium replenisher is 5% to 10%. Exemplarily, the mass percentage of the carbon coating layer may be 5%, 6%, 7%, 8%, 9%, or 10%.

[0053] In these embodiments, the mass ratio of the carbon coating layer is 5% to 10%, which does not affect lithium ion transport and effectively improves electron conduction efficiency.

[0054] In some embodiments, the D50 particle size of the lithium replenisher is 3 μm to 12 μm, and / or the specific surface area of ​​the lithium replenisher is 2 m². 2 / g~10m 2 It is / g.

[0055] Exemplarily, the D50 particle size of the lithium supplement may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm. The D50 particle size may be measured by a laser particle size distribution analyzer, and the D50 particle size indicates the particle size corresponding when the cumulative volume distribution percentage of the lithium supplement reaches 50%. Further, exemplarily, the specific surface area of the lithium supplement is 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g or 10 m 2 / g.

[0056] In these examples, since the D50 particle size and the specific surface area of the lithium supplement are within an appropriate range, the lithium supplement has a high compression density and can improve the energy density.

[0057] In some examples, the magnetic foreign matter content of the lithium supplement is 0.11 ppm to 0.20 ppm. Exemplarily, the magnetic foreign matter content of the lithium supplement may be 0.11 ppm, 0.12 ppm, 0.13 ppm, 0.14 ppm, 0.15 ppm, 0.16 ppm, 0.17 ppm, 0.18 ppm, 0.19 ppm or 0.20 ppm. The influence of magnetic foreign matter on the performance of the battery can be reduced.

[0058] In some examples, the moisture content of the lithium replenisher is 125 ppm to 530 ppm. For example, the moisture content of the lithium replenisher is 125 ppm, 127 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 215 ppm, 220 ppm, 225 ppm, 230 ppm, 240 ppm, 247 ppm, 260 ppm, 270 ppm, It may also be 280 ppm, 290 ppm, 296 ppm, 311 ppm, 312 ppm, 340 ppm, 350 ppm, 370 ppm, 390 ppm, 400 ppm, 410 ppm, 420 ppm, 430 ppm, 440 ppm, 450 ppm, 459 ppm, 470 ppm, 785 ppm, 500 ppm, 527 ppm, or 530 ppm.

[0059] In these embodiments, the lithium replenishment effect can be improved by having a low water content in the lithium replenishment agent and effectively reducing the hydrolysis of lithium sulfide and disulfide.

[0060] In some embodiments, the compressed density of the lithium replenisher is 2.01 g / mL to 2.15 g / mL. Exemplarily, the compressed density of the lithium replenisher may be 2.01 g / mL, 2.03 g / mL, 2.05 g / mL, 2.10 g / mL, 2.11 g / mL, 2.13 g / mL, 2.14 g / mL, or 2.15 g / mL.

[0061] In these embodiments, the lithium replenisher has a high compressive density and a high energy density.

[0062] According to a second aspect, the embodiment of the present application provides a method for manufacturing a lithium replenisher. As shown in Figure 1, the manufacturing method includes the following steps S11 to S12.

[0063] In step S11, the first lithium source and the first sulfur source are mixed and the first reaction treatment is carried out to obtain the first reaction solution. The first reaction solution contains a first sulfide, and the first sulfide contains lithium sulfide.

[0064] The first reaction may be a metathesis reaction.

[0065] In some embodiments, the first lithium source comprises at least one of lithium sulfate, lithium oxalate, and lithium carbonate, and the first sulfur source comprises at least one of barium sulfide and calcium sulfide.

[0066] In these embodiments, when the first lithium source and the first sulfur source are used, a metathesis reaction occurs during the first reaction treatment to obtain a lithium sulfide solution and a precipitate of barium sulfate, barium oxalate, or calcium sulfate, and then high-purity lithium sulfide is obtained by solid-liquid separation.

[0067] In some embodiments, the molar ratio of sulfur elements in the first sulfur source to lithium elements in the first lithium source may be 0.5:(1.0~1.1). For example, the molar ratio of sulfur elements in the first sulfur source to lithium elements in the first lithium source may be 0.5:1.0 or 0.5:1.1.

[0068] In these examples, high-purity lithium sulfide can be obtained by reacting the first sulfur source and the first lithium source in stoichiometric ratios, while avoiding the formation of polylithium sulfide or other impurities.

[0069] In some examples, the purity of the first lithium source and the first sulfur source is 99.5% or higher. This purity refers to the mass fraction; that is, the mass fraction of the first lithium source and the first sulfur source is 99.5% or higher, meaning that the mass fraction of impurities is 0.5% or less.

[0070] In these embodiments, the purity of the reaction product, lithium sulfide, can be improved, and the introduction of impurities can be reduced.

[0071] In some embodiments, the magnetic foreign matter content of the first lithium source and the first sulfur source is less than 1 ppm. This magnetic foreign matter content also refers to the mass content; that is, the mass content of magnetic foreign matter in the first lithium source and the first sulfur source is less than 1 ppm, meaning the mass content of magnetic foreign matter is 1 ppm or less.

[0072] In these embodiments, controlling the magnetic foreign matter content of the first lithium source and the first sulfur source to less than 1 ppm is advantageous in reducing the magnetic foreign matter content, thereby reducing the magnetic foreign matter content in the final product or reducing the difficulty of removing magnetic foreign matter from the final product.

[0073] In some embodiments, the temperature of the first reaction treatment may be 30°C to 60°C, and the duration may be 30 min to 60 min. For example, the temperature of the first reaction treatment may be 30°C, 40°C, 50°C, or 60°C, and the duration may be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min.

[0074] In these embodiments, by controlling the temperature of the first reaction process to 30°C to 60°C and the time to 30 min to 60 min, the first sulfur source and the first lithium source can be reacted rapidly, thereby improving the reaction efficiency.

[0075] In step S12, the first reaction solution is mixed with a reducing agent, a pH adjuster, and a second sulfide to obtain a mixture, and a first purification treatment is performed to obtain a sulfide composite material, the second sulfide being at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides.

[0076] By adding a reducing agent, oxidation of sulfur ions is effectively avoided, and the performance stability of the first and second sulfides in the sulfide composite material is maintained. Since the first and second sulfides hydrolyze with water to produce hydroxides, the pH adjusting agent may also contain hydroxides, and by adding hydroxides, the hydrolysis of the first and second sulfides during the first purification process can be effectively suppressed. The presence of a reducing agent and hydroxides is advantageous for the purification of the first and second sulfides and reduces impurities.

[0077] In some embodiments, the reducing agent may include at least one of hydrazine hydrate and sulfite.

[0078] In these embodiments, hydrazine hydrate can generate nitrogen gas as a reducing agent without introducing new impurities into the sulfide composite material.

[0079] Furthermore, the concentration and amount of the reducing agent are not particularly limited as long as they achieve the reducing effect and prevent oxidation of the sulfide composite material.

[0080] In some embodiments, when the reducing agent contains hydrazine hydrate, the hydrazine hydrate solution is mixed with the first reaction solution, the pH adjuster, and the second sulfide. In the hydrazine hydrate solution, the mass fraction of hydrazine hydrate may be 20% to 30%. For example, in the hydrazine hydrate solution, the mass fraction of hydrazine hydrate may be 20%, 22%, 25%, 28%, or 30%. The solvent used in the hydrazine hydrate solution may be the same as the solvent in the first reaction solution.

[0081] In some embodiments, the pH adjuster includes a hydroxide, which is selected from metal hydroxides corresponding to metal sulfides other than lithium hydroxide and / or lithium sulfide.

[0082] In these embodiments, the addition of hydroxides can effectively suppress the hydrolysis of the corresponding metal sulfides and / or lithium sulfides.

[0083] In some embodiments, the hydroxide may be a battery-grade hydroxide to further reduce the introduction of impurities.

[0084] In some embodiments, the metal sulfide used in the second sulfide comprises at least one of sodium sulfide, calcium sulfide, and potassium sulfide, and the organic sulfide used in the second sulfide comprises at least one of ammonium sulfide, sodium dithiocarbamate, and sodium potassium dithiocarbamate.

[0085] In some examples, the molar ratios of the reducing agent, hydroxide ions in the hydroxide, lithium sulfide, and sulfur in the disulfide are (0.05~0.1):(0.02~0.05):(1.0~1.1):(0.1~0.31). Exemplary examples include: 0.05:0.02:1.0:0.1, 0.05:0.03:1.0:0.1, 0.05:0.05:1.0:0.1, 0.05:0.02:1.1:0.1, 0.05:0.02:1.0:0.2, 0.05:0.02:1.0:0.31, 0.05:0.03:1.1:0.2, and 0.05:0.03:1.1:0. .31, 0.05:0.05:1.1:0.2, 0.05:0.05:1.1:0.31, 0.08:0.02:1.0:0.1, 0.08:0.03:1.0:0.1, 0.08:0.03:1.1:0.1, 0.08:0.03:1.1:0.2, 0.1:0.02:1.0:0.1, 0.1:0.05:1.0:0.1, 0.1:0.05:1.1:0.2, or 0.1:0.05:1.0:0.31, etc. are also acceptable.

[0086] In these embodiments, by controlling the molar ratios of the reducing agent, hydroxide ions in the hydroxide, lithium sulfide, and sulfur element in the disulfide to the above range, it is possible to effectively prevent oxidation and hydrolysis of lithium sulfide and disulfide while minimizing the introduction of impurities.

[0087] In some embodiments, the first purification step in S12 is: The process includes concentrating the mixture to obtain crystals of the first and second sulfides, and purifying the first and second sulfides.

[0088] In these examples, the first and second sulfides can be purified by dissolving them in a first reaction solution and crystallizing them. This first purification process can improve the purity of the sulfide composite material when the process is simple, easy to implement, and low-cost.

[0089] In some examples, the concentration described above is performed under vacuum, and the concentration temperature is 50°C to 80°C.

[0090] In some embodiments, the Baumé degree of the concentrated solution after concentration is 45 to 50. For example, the concentration temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. Furthermore, for example, the Baumé degree of the final concentrated solution after concentration may be 45, 46, 47, 48, 49, or 50.

[0091] In these embodiments, vacuum concentration effectively lowers the concentration temperature, reducing damage to the sulfide composite material due to high temperatures. Furthermore, by controlling the temperature and the Baumé degree of the final concentrate after concentration, the crystal precipitation of lithium sulfide and disulfide can be effectively promoted, and the precipitation of impurities can be reduced.

[0092] In some embodiments, crystals of the first sulfide and the second sulfide can be obtained by lowering the temperature of the concentrate; that is, the first sulfide and the second sulfide can be crystallized by lowering the temperature, the crystallization temperature being 10°C to 25°C, and the rate of lowering the temperature being 10°C / h to 15°C / h. Exemplarily, the crystallization temperature may be 10°C, 12°C, 15°C, 17°C, 19°C, 20°C, 22°C, 24°C, or 25°C. Furthermore, exemplarily, the rate of lowering the temperature may be 10°C / h, 12°C / h, 13°C / h, 14°C / h, or 15°C / h.

[0093] In these embodiments, the first sulfide and the second sulfide are crystallized by cooling, with a crystallization temperature of 10°C to 25°C and a cooling rate of 10°C / h to 15°C / h. This allows for proportional crystallization of lithium sulfide and the second sulfide from the mixture, thereby reducing losses.

[0094] In some embodiments, the method for producing the lithium replenisher further includes the steps of solid-liquid separation of the crystallized material, washing the separated solid material, and drying it.

[0095] In these examples, a mixed crystalline material of primary and secondary sulfides with high purity can be obtained by solid-liquid separation of the crystallized material, washing the separated solid material, and drying it. The solid-liquid separation process, washing, and drying process are simple and convenient.

[0096] To further reduce the introduction of impurities, the manufacturing method may further include a step of filtering the mixture through a filter element with a pore size of 20 nm to 50 nm to remove impurities from the mixture before crystallizing the mixture from the mixture by concentration to obtain a sulfide composite material.

[0097] In some embodiments, the solid-liquid separation described above may be performed by centrifugal force. Separating the material after crystallization by centrifugal force is convenient and can reduce impurities.

[0098] In some embodiments, the separated solid material is washed with a first solvent, which may contain at least one of methanol, ethanol, and glycerin, and the volume of the first solvent is 3 to 6 times the volume of the solid material. Illustratively, the volume of the first solvent may be 3, 4, 5, or 6 times the volume of the solid material.

[0099] In these embodiments, moisture residue can be reduced by washing the solid material separated with the first solvent. At the same time, by controlling the volume of the first solvent, moisture in the solid material can be effectively washed away, further reducing moisture residue.

[0100] In some embodiments, the drying temperature is 50°C to 80°C, the time is 3 to 6 hours, and the drying method may be vacuum drying or atmospheric pressure drying under protective gas protection. Illustratively, the drying temperature may be 50°C, 51°C, 53°C, 55°C, 56°C, 58°C, 60°C, 62°C, 65°C, 67°C, 69°C, 70°C, 71°C, 74°C, 76°C, 78°C, 79°C, or 80°C, and the drying time may be 3 hours, 4 hours, 5 hours, or 6 hours. The protective gas used during atmospheric pressure drying may be at least one selected from the group consisting of nitrogen gas, argon gas, and helium gas.

[0101] In some examples, the residual amount (as a mass fraction) of the first solvent in the solid material after the drying process is less than 0.3%.

[0102] Furthermore, the solvent used in the first reaction treatment in step S11 is not particularly limited, and any solvent that can dissolve lithium sulfide and dissolve disulfide, and that can proportionally crystallize lithium sulfide and disulfide by concentration, is within the scope of protection of this application.

[0103] In some embodiments, the solvent used in the first reaction treatment may include at least one of distilled water, deionized water, pure water, methanol, ethanol, and glycerin. That is, the solvent in the first reaction solution may be at least one selected from the group consisting of distilled water, deionized water, pure water, methanol, ethanol, and glycerin.

[0104] In these examples, the low boiling points of methanol, ethanol, and glycerin facilitate subsequent concentration and crystallization.

[0105] In some embodiments, as shown in Figure 1, the method for producing the lithium replenisher may further include the following step S13.

[0106] In step S13, the carbon material and the sulfide composite material are mixed and a second reaction treatment is performed to produce a lithium replenisher.

[0107] In these examples, the lithium replenisher can be produced by mixing a carbon material and a sulfide composite material and performing a second reaction treatment. This second reaction treatment is a simple process and can produce a high-purity carbon-coated material.

[0108] The specific composition of the carbon material is not limited. In some embodiments, the carbon material includes CNTs (Carbon Nanotubes) and / or graphene.

[0109] In some embodiments, the mass ratio of the sulfide composite material to the carbon material when mixed may be (90-95):(5-10). Illustratively, the mass ratio of the sulfide composite material to the carbon material when mixed may be 90:5, 90:6, 90:7, 90:8, 90:9, 90:10, 91:5, 91:6, 91:7, 91:8, 91:9, 91:10, 92:5, 92:6, 92:7, 92:8, 92:9, 92:10, 95:5, 95:6, 95:7, 95:8, 95:9, or 95:10, etc.

[0110] In some embodiments, the second reaction treatment includes polishing and calcination.

[0111] In these embodiments, by processing by polishing and calcination, on the one hand, the sulfide composite material can be further fused to produce a more uniformly mixed sulfide composite material, and on the other hand, the sulfide composite material can be coated with a carbon coating layer, thereby improving the electron conduction efficiency of the lithium replenisher. By calcining under a protective gas, humidity and oxygen content can be further controlled, and hydrolysis and oxidation of the sulfide composite material can be reduced.

[0112] In some embodiments, the polishing time may be 1 to 2 hours. Polishing may also be performed by ball milling to mix the carbon material with a mixed crystal of lithium sulfide and disulfide.

[0113] In some embodiments, the balls used in the ball milling process may be ceramic balls, and the material can be polished until its particle size is between 2 μm and 10 μm.

[0114] In some embodiments, the baking temperature may be 200°C to 300°C, and the time may be 5 to 8 hours. For example, the baking temperature may be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C, and the time may be 5 hours, 6 hours, 7 hours, or 8 hours, etc.

[0115] Furthermore, in some embodiments, in order to further reduce hydrolysis and oxidation of the sulfide composite material, the humidity inside the calcination furnace is less than 0.1%, the oxygen content is less than 1 ppm, and the furnace pressure is 200 Pa to 400 Pa during calcination. At the same time, in order to further reduce impurities introduced during calcination, the manufacturing method may further include the step of discharging the exhaust gas out of the furnace in a timely manner using an induced draft fan during calcination, and discharging the material after the calcination is complete and the temperature of the material has cooled to 50°C or below. The calcination may be carried out under a protective atmosphere. The protective atmosphere may include at least one of nitrogen gas, argon gas, and helium gas.

[0116] Furthermore, in order to reduce iron impurities in the lithium replenisher and produce a lithium replenisher that meets the requirements, the manufacturing method may further include the step of sieving and iron removal treatment of the discharged material after discharge to obtain the lithium replenisher.

[0117] To avoid hydrolysis and oxidation of the sulfide composite material in the lithium replenisher, the above sieving and iron removal processes can both be performed in a constant temperature and humidity chamber. The humidity in the constant temperature and humidity chamber is 10% or less, and the temperature is 20°C to 30°C.

[0118] During the sieving process, the lithium replenisher can be obtained by sieving using sieves with a mesh size of 100 to 200.

[0119] When removing iron, an electromagnetic iron remover can be used. Furthermore, the process from discharge to sieving described above can be carried out by negative pressure conveying.

[0120] In some embodiments, the method for manufacturing a lithium replenisher according to the present invention is applied to the manufacture of the above-mentioned lithium replenisher.

[0121] In the method for producing a lithium replenisher according to the embodiment of the present application, a first reaction solution containing a first sulfide containing lithium sulfide is produced, and then the first reaction solution and a second sulfide are mixed in the presence of a reducing agent and a pH adjuster, and a first purification treatment is performed to produce a sulfide composite material of high purity. The production method is simple, and the obtained sulfide composite material has high purity.

[0122] According to a third aspect, an embodiment of the present application provides a positive electrode sheet comprising a current collector and a positive electrode material comprising a lithium replenisher as described in the first aspect, provided on at least one side in the thickness direction of the current collector.

[0123] According to the fourth aspect, an embodiment of the present application provides a secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator as described in the third aspect.

[0124] The following are some specific examples. These examples are illustrative and intended only to interpret this application, and should not be considered limiting. Unless otherwise specified, specific techniques and conditions in the examples are carried out in accordance with the techniques and conditions described in the relevant art literature or in accordance with product specifications. Unless otherwise specified, the reagents and equipment used are all commercially available and commonly used.

[0125] (Example 1) The method for producing the lithium replenisher according to Example 1 is as follows.

[0126] Barium sulfide, lithium sulfate, and methanol are mixed and reacted by stirring at 45°C for 45 minutes to obtain a precipitate and a first reaction solution. The mixture is filtered, and 25% (mass fraction) hydrazine hydrate and battery-grade lithium hydroxide are added to the first reaction solution. Sodium sulfide (disulfide) is then added and stirred to dissolve. The mixture is then microfiltered through a 30 nm filter element, and the resulting microfiltrate is concentrated using vacuum concentration at a concentration temperature of 70 ± 1°C, with the final concentrated solution having a Baumé degree of 47.3. The mixture was concentrated until it reached a certain consistency, then cooled to a temperature of 20°C at a cooling rate of 13°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol, with the volume of anhydrous methanol used for washing being five times the volume of the crystals. Subsequently, the mixture was dried under vacuum / or under the protection of nitrogen gas at a drying temperature of 70°C for 5 hours. Drying was stopped after the methanol content in the crystals was less than 0.3% (mass fraction), and a sulfide composite material was obtained. After drying was complete, the sulfide composite material and graphene were mixed in a mass ratio of 92:8 for 1.5 hours. Ceramic balls were added during the mixing process and polished until the particle size of the material was 6.1 μm. After polishing was completed, the material was placed in a nitrogen gas protected atmosphere furnace and calcined. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 300 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 250°C, and the calcination time was 6 hours. After calcination was completed, the material was cooled to below 50°C before being discharged. The discharged material was sieved, iron removed, and then packaged to obtain a lithium replenisher. Sieving was performed using a 150-mesh sieve, and iron removal was performed using an electromagnetic iron remover. Sieving, iron removal, and packaging were all performed in a constant temperature and humidity room, with humidity controlled to below 10% and temperature controlled to 25±5°C.

[0127] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, and the molar ratio of added barium sulfide, lithium sulfate, hydrazine hydrate, and lithium hydroxide is 1:1.05:0.08:0.04. In the lithium replenisher, the molar ratio of lithium sulfide to sodium sulfide is 1:0.18.

[0128] (Example 2) The method for producing the lithium replenisher according to Example 2 is as follows.

[0129] Barium sulfide, lithium sulfate, and methanol were mixed and reacted by stirring at 30°C for 30 minutes to obtain a precipitate and a first reaction solution. The mixture was filtered, and 20% (mass fraction) hydrazine hydrate and battery-grade lithium hydroxide were added to the first reaction solution. Sodium sulfide (disulfide) was then added and stirred to dissolve. The mixture was then microfiltered through a 20 nm filter element, and the resulting microfiltrate was concentrated using vacuum concentration at a concentration temperature of 50°C until the final concentrate had a Baumé degree of 45. The mixture was then cooled to 10°C at a cooling rate of 10°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol. The volume of anhydrous methanol used for washing was 6 times the volume of the crystals. Subsequently, the material was dried under vacuum drying / or nitrogen gas protection at a drying temperature of 50°C for 6 hours until the methanol content in the crystals was less than 0.3% (mass fraction), at which point drying was stopped to obtain a sulfide composite material. After drying was complete, the sulfide composite material and CNTs were mixed in a mass ratio of 90:10 for 1 hour. During the mixing process, ceramic balls were added and polished until the particle size of the material was 2.6 μm. After polishing was complete, the material was calcined in a nitrogen gas protected atmosphere furnace. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 200 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 200°C, and the calcination time was 5 hours. After calcination was complete, the material was cooled to below 50°C before being discharged. The discharged material was sieved, iron was removed, and then it was packaged to obtain a lithium replenisher. The sieving is performed using a 100-mesh sieve, and iron removal is performed using an electromagnetic iron remover. The sieving, iron removal, and packaging are all carried out in a constant temperature and humidity room, with humidity controlled to 10% or less and temperature controlled to 25±5℃.

[0130] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, and the molar ratio of added barium sulfide, lithium sulfate, reducing agent, and lithium hydroxide is 1:1.0:0.05:0.02. In the lithium replenisher, the molar ratio of lithium sulfide to sodium sulfide is 1:0.29.

[0131] (Example 3) The method for producing the lithium replenisher according to Example 3 is as follows.

[0132] Barium sulfide, lithium sulfate, and methanol were mixed and reacted by stirring at 60°C for 60 minutes to obtain a precipitate and a first reaction solution. The mixture was filtered, and 30% (mass fraction) hydrazine hydrate and battery-grade lithium hydroxide were added to the first reaction solution. Sodium sulfide (disulfide) was then added and stirred to dissolve. The mixture was then microfiltered using a 50 nm filter element, and the resulting microfiltrate was concentrated using vacuum concentration at a concentration temperature of 80°C until the final concentrate had a Baumé degree of 50. The mixture was then cooled to 25°C at a cooling rate of 15°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol. The volume of anhydrous methanol used for washing was three times the volume of the crystals. Subsequently, the material was dried under vacuum drying / or nitrogen gas protection at a drying temperature of 80°C for 3 hours until the methanol content in the crystals was less than 0.3% (mass fraction), at which point drying was stopped to obtain a sulfide composite material. After drying was complete, the sulfide composite material and graphene were mixed in a mass ratio of 95:5 for 2 hours. During the mixing process, ceramic balls were added and polished until the particle size of the material was 10 μm. After polishing was complete, the material was calcined in a nitrogen gas protected atmosphere furnace. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 400 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 300°C, and the calcination time was 8 hours. After calcination was complete, the material was cooled to below 50°C before being discharged. The discharged material was sieved, iron was removed, and then it was packaged to obtain a lithium replenisher. The sieving is performed using a 200-mesh sieve, and iron removal is performed using an electromagnetic iron remover. The sieving, iron removal, and packaging are all carried out in a constant temperature and humidity room, with humidity controlled to 10% or less and temperature controlled to 25±5℃.

[0133] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, and the molar ratio of added barium sulfide, lithium sulfate, reducing agent, and lithium hydroxide is 1:1.1:0.1:0.05. In the lithium replenisher, the molar ratio of lithium sulfide to sodium sulfide is 1:0.1.

[0134] (Example 4) The method for producing the lithium replenisher according to Example 4 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that the molar ratio of the added barium sulfide, lithium sulfate, reducing agent, and lithium hydroxide is 1:0.9:0.05:0.02.

[0135] (Example 5) The method for producing the lithium replenisher according to Example 5 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that the molar ratio of the added barium sulfide, lithium sulfate, reducing agent, and lithium hydroxide is 1:1.0:0.04:0.02.

[0136] (Example 6) The method for producing the lithium replenisher according to Example 6 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that the molar ratio of the added barium sulfide, lithium sulfate, reducing agent, and lithium hydroxide is 1:1.0:0.05:0.01.

[0137] (Example 7) The method for producing the lithium replenisher according to Example 7 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that sodium sulfite is used as the reducing agent instead of hydrazine hydrate.

[0138] (Example 8) The method for producing the lithium replenisher according to Example 8 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that sodium hydroxide is used instead of lithium hydroxide.

[0139] (Example 9) The method for producing the lithium replenisher according to Example 9 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that the molar ratio of barium sulfide to sodium sulfide is 1:0.05.

[0140] (Example 10) The method for producing the lithium replenisher according to Example 10 is the same as the method for producing the lithium replenisher according to Example 1, and the difference is: The only difference is that the molar ratio of barium sulfide to sodium sulfide is 1:0.32.

[0141] (Example 11) The method for producing the lithium replenisher according to Example 11 is as follows.

[0142] Barium sulfide, lithium sulfate, and methanol were mixed and reacted with stirring at 45°C for 45 minutes to obtain a precipitate and a first reaction solution. The mixture was filtered, and 25% (mass fraction) hydrazine hydrate and battery-grade calcium hydroxide were added to the first reaction solution. Further addition of calcium sulfide (disulfide) was added, and after stirring to dissolve, the mixture was microfiltered through a 30 nm filter element. The resulting microfiltrate was concentrated using vacuum concentration at a concentration temperature of 70 ± 1°C until the final concentrate had a Baumé degree of 47.3. The mixture was then cooled to 20°C at a cooling rate of 13°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol. The volume of anhydrous methanol used for washing was 5 times the volume of the crystals. Subsequently, the material was dried under vacuum drying / or nitrogen gas protection at a drying temperature of 70°C for 5 hours until the methanol content in the crystals was less than 0.3% (mass fraction), at which point drying was stopped to obtain a sulfide composite material. After drying was complete, the sulfide composite material and graphene were mixed in a mass ratio of 92:8 for 1.5 hours. During the mixing process, ceramic balls were added and polished until the particle size of the material was 6.1 μm. After polishing was complete, the material was calcined in a nitrogen gas protected atmosphere furnace. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 300 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 250°C, and the calcination time was 6 hours. After calcination was complete, the material was cooled to below 50°C before being discharged. The discharged material was sieved, iron was removed, and then it was packaged to obtain a lithium replenisher. The sieving is performed using a 150-mesh sieve, and iron removal is performed using an electromagnetic iron remover. The sieving, iron removal, and packaging are all carried out in a constant temperature and humidity room, with humidity controlled to 10% or less and temperature controlled to 25±5℃.

[0143] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, the molar ratio of added barium sulfide, lithium sulfate, reducing agent and calcium hydroxide is 1:1.05:0.08:0.04, and the molar ratio of lithium sulfide to calcium sulfide is 1:0.18.

[0144] (Example 12) The method for producing the lithium replenisher according to Example 12 is as follows.

[0145] Barium sulfide, lithium sulfate, and methanol were mixed and reacted with stirring at 45°C for 45 minutes to obtain a precipitate and a first reaction solution. The mixture was filtered, and 25% (mass fraction) hydrazine hydrate and battery-grade potassium hydroxide were added to the first reaction solution. Potassium sulfide (disulfide) was then added and stirred to dissolve. The mixture was then microfiltered using a 30 nm filter element, and the resulting microfiltrate was concentrated using vacuum concentration at a concentration temperature of 70 ± 1°C until the final concentrate had a Baumé degree of 47.3. The mixture was then cooled to 20°C at a cooling rate of 13°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol. The volume of anhydrous methanol used for washing was 5 times the volume of the crystals. Subsequently, the material was dried under vacuum drying / or nitrogen gas protection at a drying temperature of 70°C for 5 hours until the methanol content in the crystals was less than 0.3% (mass fraction). After drying was stopped, the sulfide composite material was obtained. After drying was complete, the sulfide composite material and graphene were mixed in a mass ratio of 92:8 for 1.5 hours. During the mixing process, ceramic balls were added and polished until the particle size of the material was 6.1 μm. After polishing was complete, the material was calcined in a nitrogen gas protected atmosphere furnace. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 300 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 250°C, and the calcination time was 6 hours. After calcination was complete, the material was cooled to below 50°C before being discharged. The discharged material was sieved, iron was removed, and then it was packaged to obtain a lithium replenisher. The sieving was performed using a 150-mesh sieve, and iron removal was carried out using an electromagnetic iron remover. The sieving, iron removal, and packaging were all performed in a constant temperature and humidity room, with humidity controlled to 10% or less and temperature controlled to 25±5℃.

[0146] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, the molar ratio of added barium sulfide, lithium sulfate, reducing agent and potassium hydroxide is 1:1.05:0.08:0.04, and the molar ratio of lithium sulfide to potassium sulfide is 1:0.18.

[0147] (Comparative Example 1) The method for producing the lithium replenishment agent according to Comparative Example 1 is as follows.

[0148] Barium sulfide, lithium sulfate, and methanol were mixed and reacted with stirring at 45°C for 45 minutes to obtain a precipitate and a first reaction solution. The mixture was filtered, and 25% (mass fraction) hydrazine hydrate and battery-grade lithium hydroxide were added to the first reaction solution. After stirring to dissolve, the mixture was microfiltered through a 30 nm filter element. The resulting microfiltrate was concentrated using vacuum concentration at a concentration temperature of 70 ± 1°C until the final concentrate had a Baumé degree of 47.3. The mixture was then cooled to 20°C at a cooling rate of 13°C / h. The resulting crystals were centrifuged and shaken off, then washed with anhydrous methanol. The volume of anhydrous methanol used for washing was 5 times the volume of the crystals. The mixture was then dried under vacuum / or under nitrogen gas protection at a drying temperature of 70°C for 5 hours until the methanol content in the crystals was less than 0.3% (mass fraction). Drying was then stopped to obtain lithium sulfide. After drying was complete, lithium sulfide and graphene were mixed in a mass ratio of 92:8 for 1.5 hours. During the mixing process, ceramic balls were added and polished until the particle size of the material was 6.1 μm. After polishing was complete, the material was calcined in a nitrogen gas protected atmosphere furnace. During calcination, the amount of nitrogen gas introduced was adjusted so that the humidity inside the furnace was less than 0.1% and the oxygen content was less than 1 ppm. The furnace pressure was set to 300 Pa, the exhaust gas was discharged outside the furnace by an induced draft fan, the calcination temperature was set to 250°C, and the calcination time was 6 hours. After calcination was complete, the material was cooled to below 50°C before being discharged. The discharged material was sieved to remove iron and then packaged to obtain a lithium replenisher. The sieving was performed using a 150-mesh sieve, and iron removal was carried out using an electromagnetic iron remover. The sieving, iron removal, and packaging were all performed in a constant temperature and humidity room, with humidity controlled to 10% or less and temperature controlled to 25±5℃.

[0149] The main content of barium sulfide and lithium sulfate is 99.5% or more (as mass fraction), the content of magnetic foreign matter is less than 1 ppm, and the molar ratio of added barium sulfide, lithium sulfate, hydrazine hydrate, and lithium hydroxide is 1:1.05:0.08:0.04.

[0150] Test methods and test results 1. Chemical and physicochemical index tests of lithium replenishers. Chemical component index and physicochemical index tests were performed on the lithium replenishers according to Examples 1 to 12 and Comparative Example 1, and the specific test results are shown in Table 1 below.

[0151] [Table 1] TIFF2026071134000003.tif39170

[0152] In Table 1 above, the calcium, magnesium, zinc, copper, nickel, and cobalt content of the lithium replenisher was measured by inductively coupled plasma atomic emission spectroscopy, the barium content was measured by sulfuric acid titration, and the lithium hydroxide content was measured by potentiometric automatic titration.

[0153] In Table 1, the water content in the lithium replenisher was measured by the KF method, magnetic foreign matter in the lithium replenisher was collected using a magnet, dissolved in aqua regia, and measured with an atomic absorption spectrophotometer, the BET specific surface area was measured using a BET measuring instrument by the nitrogen multi-point adsorption method, the pH value of the lithium replenisher was measured with a pH meter by acid-base potentiometric titration, and the D50 particle size was measured with a laser particle size analyzer. The D50 particle size represents the particle size corresponding to when the cumulative volume distribution percentage of the lithium replenisher reaches 50%.

[0154] In Table 1, the compression density was measured using a compression densimeter, with a test pressure of 3T and a pressing time of 30S.

[0155] As can be seen from Table 1, the D50 particle size of the lithium replenishers in Examples 1 to 12 is between 3.2 μm and 11.5 μm, and is mostly concentrated between 6.2 μm and 7.2 μm, and the specific surface area of ​​the lithium replenishers in Examples 1 to 12 is 2 m². 2 / g~10m 2 It is between / g and mostly 6.1m 2 / g~6.8m 2The concentration is between / g, and the compressed density of the lithium replenisher according to Examples 1 to 12 is 2.01 g / mL to 2.15 g / mL. It has an appropriate D50 particle size, specific surface area, and compressed density, which is advantageous for improving energy density when the lithium replenisher is applied to secondary batteries, and provides a good lithium replenishment effect.

[0156] The lithium replenishers according to Examples 1 to 12 have low levels of both magnetic foreign matter and water content. For example, the magnetic foreign matter content is less than 0.18 ppm in all cases, and even lower, down to 0.12 ppm. The water content is less than 550 ppm in all cases, and even lower, down to 201 ppm. This is advantageous in reducing the degradation of the lithium replenisher's performance due to the introduction of magnetic foreign matter and water.

[0157] The pH values ​​of the lithium replenishers in Examples 1-5 and Examples 7-12 were all controlled to 12.8 or less, and the LiOH content was also basically controlled to ppm grade. This suppressed to some extent the hydrolysis of lithium sulfide to produce LiOH, thereby maintaining a high lithium replenishment effect and avoiding a decrease in the initial charge-discharge ratio capacity.

[0158] The lithium replenisher according to Example 6 has a high LiOH content, reaching 8.70%. This is because, when the pH adjusting agent is low, the hydrolysis of lithium sulfide is not easily suppressed during the reaction process, which can lead to the generation of more LiOH, and consequently, the pH value also rises.

[0159] Comparing Example 4 with Example 1, when the amount of lithium sulfate is low in Example 4, the amount of element Ba in the lithium replenisher increases. This indicates that when the amount of the first lithium source added is small, impurities are more easily introduced into the lithium replenisher.

[0160] Comparing Example 5 with Example 1, in Example 5, when the amount of reducing agent is small, the water content, pH value, and LiOH content of the lithium replenisher all increase. This indicates that lithium sulfide and sodium sulfide are oxidized and hydrolyzed in small amounts, and the impurity LiOH is introduced.

[0161] Comparing Example 6 with Example 1, in Example 6, when the amount of pH adjusting agent is small, the hydrolysis of lithium sulfide is not easily suppressed during the reaction process, resulting in the generation of more LiOH and a corresponding increase in the pH value.

[0162] Comparing Example 9 with Example 1, when the amount of sodium sulfide is low in Example 9, the water content and pH value of the lithium replenisher are clearly higher, and the LiOH content also tends to be higher. This indicates that the addition of sodium sulfide has an inhibitory effect on both the water content and LiOH content, and can adjust the pH value.

[0163] Comparing Example 10 with Example 1, when the amount of sodium sulfide is high in Example 10, the pH value and water content of the lithium replenisher are clearly lower, as is the LiOH content. This indicates that sodium sulfide has a modulating effect on the pH value, water content, and LiOH content of the lithium replenisher.

[0164] 2. Electrical performance index test of lithium replenisher (1) Positive electrode materials were manufactured using lithium replenishers according to Examples 1 to 12 and Comparative Example 1 as positive electrode active materials. The positive electrode material was prepared by mixing the positive electrode active material with SP and PVDF in a mass ratio of 80:10:10. After coating the positive electrode current collector with this material, a button-type battery was manufactured using 1 mol / L lithium hexafluoride phosphate as the electrolyte and a lithium sheet as the negative electrode. A charge-discharge test was performed at a rate of 0.1C (voltage range of 2V to 4.0V), and the test results are shown in Table 2 below.

[0165] [Table 2]

[0166] As can be seen from Table 2, since the lithium replenisher in Examples 1 to 12 is a composite material of lithium sulfide and disulfide, the initial charge ratio capacity and initial discharge ratio capacity of Examples 1 to 12 are both lower than those of Comparative Example 1. As can be seen from Tables 2 and 1, in Examples 1 to 3, Examples 7 to 9, and Examples 11 to 12, when the molar ratio of the reducing agent, hydroxide ions in the hydroxide, lithium sulfide, and sulfur element in the disulfide is (0.05 to 0.1):(0.02 to 0.05):(1.0 to 1.1):(0.1 to 0.31), the initial charge ratio capacity of the lithium replenisher according to the present application can be maintained at 600 mAh / g or more, and it can have an initial charge ratio capacity and initial discharge ratio capacity equivalent to Comparative Example 1, thus maintaining that the lithium replenisher has a good lithium replenishment effect.

[0167] As can be seen by comparing Example 4 with Comparative Example 1, in Example 4, when the amount of lithium sulfate is small, a certain amount of barium sulfide is introduced as an impurity, and the lithium sulfide content is reduced, so both the initial charge ratio capacity and the initial discharge ratio capacity of the lithium replenisher decrease to some extent.

[0168] As can be seen by comparing Example 5 with Comparative Example 1, in Example 5, when the amount of reducing agent is small, lithium sulfide and sodium sulfide undergo hydrolysis and oxidation to some extent, and the initial charge ratio capacity and initial discharge ratio capacity of the lithium replenisher decrease.

[0169] As can be seen by comparing Example 6 with Comparative Example 1, in Example 6, when the amount of lithium hydroxide is small, a large amount of lithium sulfide undergoes hydrolysis, generating a large amount of lithium hydroxide, which significantly reduces both the initial charge ratio capacity and the initial discharge ratio capacity of the lithium replenisher.

[0170] (2) The lithium replenisher according to Examples 1 to 12 and the lithium replenisher according to Comparative Example 1 were mixed with lithium iron phosphate in a mass ratio of 3:97. Then, the mixture, SP, and PVDF were mixed in a mass ratio of 90:5:5 to produce a positive electrode sheet. After that, a button cell was produced in the same manner as in (1) for the remaining steps. First, it was charged at 25°C with a voltage of 2V to 4.0V and 1C, then discharged at 1C, and then cycled from the second time onwards with a voltage of 2V to 3.75V. After charging and discharging the button-type batteries for 100 cycles at 25°C and 1C, the separators of the button-type batteries were disassembled, and the number of black dots on the separators was counted. The number of black dots on the separators of the button-type batteries corresponding to Examples 1 to 3 was 1, 1, and 2, respectively. The number of black dots on the separator of the button-type battery corresponding to the lithium replenisher in Comparative Example 1 was 23. The amount of elemental sulfur dissolved in the electrolyte of the button-type batteries was measured, and the measurement results are shown in Table 3 below.

[0171] [Table 3]

[0172] As can be seen from Table 3, the elemental sulfur content in the electrolyte of button-type batteries having lithium replenishers according to Examples 1 to 12 is 300 ppm or less, which is far lower than the elemental sulfur content in the electrolyte of Comparative Example 1 (1058 ppm). Therefore, the lithium replenishers according to Examples 1 to 12 can significantly reduce the generation of elemental sulfur, thereby improving the overall performance of the battery.

[0173] As can be seen from a comparison between the button-type battery having the lithium replenisher according to Example 5 and the button-type battery having the lithium replenisher according to Example 1, when the amount of reducing agent is small in Example 5, the lithium sulfide and sodium sulfide are hydrolyzed and oxidized to some extent, thereby reducing the amount of sulfur element fixed by sodium sulfide and increasing the amount of elemental sulfur in the electrolyte of the button-type battery having the lithium replenisher according to Example 5.

[0174] As can be seen from a comparison between the button-type battery having the lithium replenisher according to Example 6 and the button-type battery having the lithium replenisher according to Example 1, when the amount of lithium hydroxide is small in Example 6, a large amount of lithium sulfide undergoes hydrolysis, and some of the sodium sulfide also undergoes hydrolysis. As a result, the amount of elemental sulfur in the electrolyte of the button-type battery having the lithium replenisher according to Example 6 is clearly higher than the amount of elemental sulfur in the electrolyte of the button-type battery having the lithium replenisher according to Example 1.

[0175] As can be seen from a comparison between the button-type battery having a lithium replenisher according to Example 9 and the button-type battery having a lithium replenisher according to Example 1, when the amount of sodium sulfide is small in Example 9, the proportion of lithium sulfide is large, and when the amount of sodium sulfide is small, it is difficult to fix the sulfur element to the maximum extent. Therefore, the amount of elemental sulfur in the electrolyte of the button-type battery having a lithium replenisher according to Example 9 is higher than the amount of elemental sulfur in the electrolyte of the button-type battery having a lithium replenisher according to Example 1.

[0176] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the technical scope of this application and produces similar effects is included within the technical scope of the present invention. In addition, as long as they do not depart from the spirit of this application, various modifications to these embodiments that a person skilled in the art could conceive, or other forms constructed by combining some of the components of the embodiments, are also included within the scope of this application.

Claims

1. A lithium replenisher comprising a sulfide composite material, wherein the sulfide composite material comprises a first sulfide and a second sulfide doped with the first sulfide, A lithium replenisher characterized in that the first sulfide contains lithium sulfide, and the second sulfide is at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides.

2. The aforementioned metal sulfide comprises at least one of sodium sulfide, calcium sulfide, and potassium sulfide, and / or The organic sulfide comprises at least one of ammonium sulfide, sodium dithiocarbamate, and potassium dithiocarbamate, and / or In the sulfide composite material, the mass ratio of the first sulfide to the second sulfide is (60-80):(15-30) and / or The lithium replenisher according to claim 1, characterized in that, in the sulfide composite material, the molar ratio of sulfur elements in the second sulfide to the first sulfide is (0.1 to 0.31):(1.0 to 1.1).

3. The sulfide composite material further comprises a carbon coating layer applied to its surface, The lithium replenisher according to claim 1, characterized in that the mass ratio of the carbon coating layer is 5% to 10%.

4. The D50 particle size of the lithium replenisher is 3 μm to 12 μm, and / or The specific surface area of ​​the lithium replenisher is 2 m². ２ / g to 10m ２ The lithium replenisher according to claim 1, characterized in that it is / g.

5. The first step is to mix a first lithium source and a first sulfur source and perform a first reaction treatment to obtain a first reaction solution, The process includes the steps of: mixing the first reaction solution with a reducing agent, a pH adjuster, and a second sulfide to obtain a mixture, and then performing a first purification treatment to obtain a sulfide composite material; A method for producing a lithium supplement, characterized in that the first reaction solution contains a first sulfide, the first sulfide contains lithium sulfide, and the second sulfide is at least one selected from the group consisting of metal sulfides other than lithium sulfide and organic sulfides.

6. The first purification step is: The process includes the step of concentrating the mixture to obtain crystals of the first sulfide and the second sulfide, and / or The method for producing the lithium replenisher is as follows: The process further includes the steps of separating the material after crystallization into solid and liquid, washing the separated solid material, and / or drying it. The method for producing the lithium replenisher is as follows: The process further includes the step of mixing a carbon material and the sulfide composite material and performing a second reaction treatment to produce the lithium replenisher, and / or The method for producing a lithium replenisher according to claim 5, characterized in that the second reaction treatment includes polishing and calcination, the polishing time being 1 to 2 hours, the calcination being carried out in a protective atmosphere, the calcination temperature being 200°C to 300°C, and the time being 5 to 8 hours.

7. The method for producing the lithium replenisher is as follows: (1) The temperature of the first reaction treatment is 30°C to 60°C, and the time is 30 min to 60 min. (2) The concentration is performed under the conditions that the concentration temperature is 50°C to 80°C and / or the Baumé degree of the concentrated solution after concentration is 45 to 50. (3) Conditions for obtaining crystals of the first sulfide and the second sulfide by subjecting the concentrated solution to a cooling treatment, (4) The method for producing a lithium replenisher according to claim 6, characterized in that the mass ratio of the sulfide composite material to the carbon material satisfies at least one of the conditions that is (90-95):(5-10).

8. The method for producing the lithium replenisher is as follows: (1) The first lithium source comprises at least one of lithium sulfate, lithium oxalate, and lithium carbonate, and the first sulfur source comprises at least one of barium sulfide and calcium sulfide, (2) The purity of both the first lithium source and the first sulfur source is 99.5% or higher. (3) The content of magnetic foreign matter in the first lithium source and the first sulfur source is less than 1 ppm. (4) The reducing agent contains at least one of hydrazine hydrate and sulfite, (5) The pH adjusting agent contains a hydroxide, and the hydroxide is selected from the hydroxides of metals corresponding to the metal sulfide other than lithium hydroxide and / or lithium sulfide. (6) The method for producing a lithium replenisher according to 6 or 7, characterized in that the carbon material satisfies at least one of the conditions including CNTs and / or graphene.

9. A positive electrode sheet comprising a current collector and a positive electrode material provided on at least one side in the thickness direction of the current collector, the positive electrode material containing a lithium replenisher according to any one of claims 1 to 4.

10. A secondary battery characterized by comprising a positive electrode sheet, a negative electrode sheet, and a separator as described in claim 9.

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