Manganese hydrogen phosphate precursor, lithium manganese iron phosphate, preparation methods of manganese hydrogen phosphate precursor and lithium manganese iron phosphate, and positive pole piece, battery and power utilization device comprising manganese hydrogen phosphate precursor and lithium manganese iron phosphate

Abstract

The invention discloses a manganese hydrogen phosphate precursor, lithium iron manganese phosphate, a preparation method of the manganese hydrogen phosphate precursor, a positive pole piece containing the lithium iron manganese phosphate, a battery containing the lithium iron manganese phosphate, and an electric device containing the lithium iron manganese phosphate. The preparation method comprises the following steps: firstly, carrying out primary precipitation reaction on soluble manganese salt and a precipitator to prepare manganese hydroxide, and then carrying out secondary precipitation reaction on the manganese hydroxide and phosphoric acid to prepare the manganese hydrogen phosphate precursor. The manganese hydrogen phosphate precursor with low impurity ion content and high yield is prepared through secondary precipitation reaction.

Description

Technical Field

[0001] The present application relates to a manganese hydrogen phosphate precursor, lithium manganese iron phosphate, a preparation method thereof, and a positive electrode plate, a battery and an electrical device containing the same. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. With the application and promotion of batteries, their safety performance has received increasing attention. Lithium manganese iron phosphate has become one of the most popular positive electrode active materials due to its advantages such as high capacity, good safety performance and abundant raw material sources. Manganese hydrogen phosphate is one of the important raw materials for the preparation of lithium manganese iron phosphate, and its performance is crucial to the performance of lithium manganese iron phosphate and batteries. However, manganese hydrogen phosphate is currently mainly obtained by reacting manganese sulfate with excess phosphoric acid or phosphate, which has problems such as difficult product precipitation, small precipitate particle size, difficulty in slurry filtration, high by-products, low yield, and low purity. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0003] The present application provides a manganese hydrogen phosphate precursor, lithium manganese iron phosphate, a preparation method thereof, and a positive electrode plate, a battery and an electrical device containing the same, which can prepare a manganese hydrogen phosphate precursor with low impurity ion content and high yield.

[0004] In a first aspect, the present application provides a method for preparing a manganese hydrogen phosphate precursor, comprising the following steps: using an aqueous complexing agent solution as a bottom liquid in a reaction vessel, and filling the reaction vessel with a protective gas; adding a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution to the reaction vessel under heating and stirring conditions, and after the feeding is completed, further aging the obtained reaction material in the reaction vessel to obtain a manganese hydroxide slurry, wherein the precipitant includes a hydroxide precipitant; filtering and washing the obtained manganese hydroxide slurry to obtain a de-impurity manganese hydroxide filter cake, or filtering and washing the obtained manganese hydroxide slurry and then mixing it with water to obtain a de-impurity manganese hydroxide slurry; mixing the obtained de-impurity manganese hydroxide filter cake or the de-impurity manganese hydroxide slurry with an aqueous phosphoric acid solution under stirring conditions to react to obtain a manganese hydrogen phosphate slurry; filtering the obtained manganese hydrogen phosphate slurry, washing with water, and drying to obtain a manganese hydrogen phosphate precursor.

[0005] The present invention provides a method for preparing a manganese hydrogen phosphate precursor with a low impurity ion content and high yield through a secondary precipitation reaction. The prepared manganese hydrogen phosphate precursor can be directly used as a manganese source for preparing lithium manganese iron phosphate. Furthermore, the preparation method provided in the present invention utilizes a wide range of raw materials, offers low manufacturing costs, and employs a simple process, making it suitable for large-scale industrial production.

[0006] In some embodiments, the protective gas in the reaction vessel includes one or more of nitrogen, argon, and helium.

[0007] In some embodiments, the complexing agent includes one or more of ammonia, ammonium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium salt, and ethylenediaminetetraacetic acid potassium salt.

[0008] In some embodiments, the precipitant comprises one or both of sodium hydroxide and potassium hydroxide.

[0009] In some embodiments, the soluble manganese salt includes one or more of industrial-grade manganese sulfate, high-purity manganese sulfate, manganese acetate, manganese chloride, and manganese nitrate.

[0010] In some embodiments, the concentration of the bottom solution in the reaction container is 0.1 mol·L -1 -5.0 mol·L -1 , which can be selected as 1 mol·L -1 -3.0 mol·L -1 .

[0011] When the concentration of the bottom liquid in the reaction vessel is within the above range, the precipitation process of manganese hydroxide will change from forming crystal nuclei to growing crystals, which is conducive to promoting the growth of manganese hydroxide particles. This is because the solubility product K of manganese hydroxide is sp Very small, soluble manganese salts react with precipitants to easily form tiny crystal nuclei. These tiny nuclei can stably exist in the solid-liquid phase, that is, the precipitation reaction is mainly characterized by the formation of crystal nuclei. Macroscopically, the precipitate is small and presents a flocculent or gel-like state, which affects the filtration effect, washing effect, and product yield. When the concentration of the bottom liquid in the reaction vessel is within the above range, these tiny crystal nuclei will be complexed and dissolved by the complexing agent. At this time, the main manifestation is the stable existence of large particles in the solid-liquid phase, causing the precipitation process to shift from mainly forming crystal nuclei to mainly causing crystal growth. Macroscopically, the manganese hydroxide particles gradually grow with increasing feeding time.

[0012] In some embodiments, the concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is 0.5 mol·L -1 -5.0 mol·L -1 , which can be selected as 1 mol·L -1 -4.0 mol·L -1 .

[0013] The concentration of the complexing agent in the mixed aqueous solution of the precipitant-complexing agent is within the above range. On the one hand, it can smoothly precipitate hydroxide and manganese ions and improve the yield. On the other hand, it can adjust the precipitation rate of hydroxide and manganese ions, thereby obtaining manganese hydroxide particles with larger particle size, which is convenient for filtration. It can also improve the oxidation resistance of manganese hydroxide when exposed to air and reduce oxidation problems during the washing process.

[0014] In some embodiments, the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution is 1.0 mol·L -1 -6.0mol·L -1 , which can be selected as 2.0 mol·L -1 -5.5 mol·L -1 .

[0015] In some embodiments, the concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is less than the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution.

[0016] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction container, the feeding method is co-current feeding.

[0017] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction container, the feeding time of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution in the reaction container is 2h-24h.

[0018] In some embodiments, in the step of adding a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution into a reaction vessel, during the feeding process, the feeding rate of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution is adjusted to adjust the pH value of the reaction system in the reaction vessel within a fluctuation range.

[0019] In some embodiments, during the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution to a reaction vessel, the pH of the reaction system in the reaction vessel is controlled to be between 7.8 and 12.0. By adjusting the pH of the reaction system in the reaction vessel within the above range, the manganese ions can be fully precipitated, the precipitate particles can be of a suitable size, and the redissolution of the manganese hydroxide precipitate can be avoided.

[0020] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into a reaction vessel, during the feeding process, the pH value of the reaction system in the reaction vessel fluctuates within a range of less than or equal to 0.1.

[0021] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction vessel under heating and stirring conditions, the stirring rate is 200 ppm-1000 rpm.

[0022] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction vessel under heating and stirring conditions, the heating temperature is 40°C-80°C.

[0023] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction vessel under heating and stirring conditions, the heating method is water bath heating or oil bath heating.

[0024] In some embodiments, the obtained reaction material is further subjected to an aging treatment in a reaction container, and the aging treatment time is 1 hour to 12 hours.

[0025] In some embodiments, the obtained reaction material is further subjected to an aging treatment in a reaction container, and the aging treatment temperature is 25° C.-80° C.

[0026] In some embodiments, in the step of further aging the obtained reaction material in the reaction container, the stirring rate is 200 rpm-1000 rpm.

[0027] In some embodiments, in the steps of filtering and washing the obtained manganese hydroxide slurry, the washing detergent is water or water containing phosphoric acid and a reducing agent.

[0028] In some embodiments, in the steps of filtering and washing the obtained manganese hydroxide slurry, the washing method is rinsing.

[0029] In some embodiments, in the steps of filtering and washing the obtained manganese hydroxide slurry, the washing detergent is water containing phosphoric acid and a reducing agent, and the reducing agent includes one or more of oxalic acid and ascorbic acid.

[0030] Water containing phosphoric acid and a reducing agent is used to wash the manganese hydroxide filter cake. On the one hand, the reducing agent can reduce a small amount of oxidized trivalent manganese ions on the surface of the manganese hydroxide filter cake to divalent manganese ions. On the other hand, phosphoric acid can also react with manganese hydroxide to generate manganese hydrogen phosphate, which is adsorbed on the surface of the manganese hydroxide filter cake. This can reduce the alkalinity of the surface of the manganese hydroxide filter cake, thereby further improving the oxidation resistance of the manganese hydroxide filter cake.

[0031] In some embodiments, the concentration of phosphoric acid in the water containing phosphoric acid and a reducing agent is 0.01 mol·L -1 -0.1 mol·L -1and / or, the concentration of the reducing agent in the water containing phosphoric acid and the reducing agent is 0.001 mol·L -1 -0.1 mol·L -1 .

[0032] Oxidation of manganese hydroxide filter cake primarily occurs on the surface of the filter cake in contact with air. Adding a small amount of phosphoric acid and a reducing agent to the water can improve the oxidation resistance of the manganese hydroxide filter cake. Furthermore, during the washing process, the detergent is in contact with the manganese hydroxide filter cake for a short time, and the concentration of phosphoric acid and reducing agent in the water containing phosphoric acid and reducing agent is too high, resulting in waste of phosphoric acid and reducing agent.

[0033] In some embodiments, the volume distribution particle size D50 of the obtained manganese hydroxide is 6 μm-25 μm.

[0034] In some embodiments, the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry is mixed with an aqueous phosphoric acid solution under stirring conditions to react to obtain a manganese hydrogen phosphate slurry, and the stirring rate is 200 ppm-1000 rpm.

[0035] In some embodiments, the concentration of phosphoric acid in the phosphoric acid aqueous solution is 0.5 mol·L -1 -6.0mol·L -1 .

[0036] In some embodiments, the molar ratio of manganese ions in the de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry to the molar ratio of phosphoric acid in the phosphoric acid aqueous solution is 1:1-1:1.2. Using a slightly excess amount of phosphoric acid can promote sufficient precipitation of manganese ions.

[0037] In some embodiments, in the step of mixing the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry with a phosphoric acid aqueous solution to react to obtain a manganese hydrogen phosphate slurry, the phosphoric acid aqueous solution is a phosphoric acid-reducing agent mixed aqueous solution.

[0038] In some embodiments, the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution includes one or more of oxalic acid and ascorbic acid.

[0039] In some embodiments, the concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution is 0.001 mol·L -1 -0.1 mol·L -1 .

[0040] The concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution is within the above range, which can reduce a small amount of trivalent manganese ions that may appear in the reaction system to divalent manganese ions, thereby improving the yield and purity of the manganese hydrogen phosphate precursor.

[0041] In some embodiments, in the step of filtering, washing, and drying the obtained manganese hydrogen phosphate slurry to obtain a manganese hydrogen phosphate precursor, the drying temperature is 80° C.-180° C.; and / or the drying time is 0.5 h-8.0 h.

[0042] In a second aspect, the present application provides a manganese hydrogen phosphate precursor, which is prepared by the preparation method of the first aspect of the present application.

[0043] In a third aspect, the present application provides a method for preparing lithium manganese iron phosphate, comprising the following steps: using a manganese hydrogen phosphate precursor prepared by the preparation method of the first aspect of the present application and a material obtained by mixing an iron source, a lithium source, and a carbon source as a raw material, and obtaining lithium manganese iron phosphate through sintering treatment.

[0044] In some embodiments, one or more of a source of doping element M, a source of doping element N, a source of doping element Q, and a source of doping element R are also added to the mixed material, where M represents a doping element at the manganese position and the iron position, N represents a doping element at the lithium position, Q represents a doping element at the phosphorus position, and R represents a doping element at the oxygen position.

[0045] In a fourth aspect, the present application provides lithium manganese iron phosphate, which is prepared by the preparation method of the third aspect of the present application.

[0046] In a fifth aspect, the present application provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes lithium manganese iron phosphate prepared by the preparation method of the third aspect of the present application.

[0047] In a sixth aspect, the present application provides a battery comprising the positive electrode sheet according to the fifth aspect of the present application.

[0048] In a seventh aspect, the present application provides an electrical device comprising the battery according to the sixth aspect of the present application, wherein the battery is used to provide electrical energy.

[0049] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0051] Figure 1 is a schematic diagram of a battery cell provided in some embodiments of the present application.

[0052] Figure 2 is a schematic diagram of a battery module provided in some embodiments of the present application.

[0053] Figure 3 is a schematic diagram of a battery pack provided in some embodiments of the present application.

[0054] Figure 4 yes Figure 3 Schematic diagram of the battery pack shown.

[0055] Figure 5 This is a schematic diagram of an exploded view of a battery cell provided in some embodiments of the present application.

[0056] Figure 6 This is a schematic diagram of an electrical device provided in some embodiments of the present application.

[0057] Figure 7 It is a process flow diagram of the preparation method provided in some embodiments of the present application.

[0058] Figure 8 This is a scanning electron microscope (SEM) image of the manganese hydroxide synthesized in Example 1-1.

[0059] Figure 9 This is a scanning electron microscope (SEM) image of the manganese hydrogen phosphate synthesized in Example 1-1.

[0060] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0061] The description of the accompanying figures is as follows: 1. battery pack; 2. upper box; 3. lower box; 4. battery module; 5. battery cell; 51. shell; 52. electrode assembly; 53. cover plate. DETAILED DESCRIPTION

[0062] Hereinafter, the embodiment of the manganese hydrogen phosphate precursor, lithium manganese iron phosphate, preparation method thereof, and positive electrode plate, battery and electric device containing the same of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0063] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0065] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0066] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0067] In this application, the terms "plurality" and "multiple" refer to two or more.

[0068] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0069] Unless otherwise stated, the numerical values of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0070] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0071] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. The battery cell can be cylindrical, rectangular or other shapes, etc., and the embodiments of the present application are not limited to this. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0072] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0073] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0074] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 2 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 2 As shown, in the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0075] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0076] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0077] Figure 3 and Figure 4 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 3 and Figure 4 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0078] The battery cells provided in the embodiments of the present application may include lithium-ion battery cells, lithium metal battery cells, negative electrode-free lithium metal battery cells, etc.

[0079] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the present embodiment.

[0080] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0081] In some embodiments, as Figure 5 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0082] Currently, manganese hydrogen phosphate is primarily produced by reacting manganese sulfate with excess phosphoric acid or phosphates. Manganese hydrogen phosphate and sulfuric acid are produced when manganese sulfate reacts with excess phosphoric acid. Due to the strong acidity of sulfuric acid, the manganese hydrogen phosphate is difficult to precipitate, requiring the addition of an alkali to raise the pH of the reaction system. Currently, the most commonly used alkalis are ammonia and sodium hydroxide.

[0083] When ammonia water is used as a pH regulator, the generated precipitate is mainly ammonium manganese phosphate. When ammonium manganese phosphate is used to prepare lithium manganese iron phosphate through a sintering method, it releases ammonia gas, thereby polluting the environment.

[0084] Using sodium hydroxide as a pH adjuster can lead to numerous side reactions and byproducts. For example, byproducts such as manganous phosphate can be generated, causing the molar ratio of phosphorus to manganese in the precipitate to deviate from the stoichiometric ratio of the target manganese hydrogen phosphate. Furthermore, sodium ions in the precipitate are difficult to wash away during filtration, making the resulting product prone to sodium contamination and resulting in low product purity. Furthermore, using sodium hydroxide as a pH adjuster can also result in a fine precipitate particle size, which can easily aggregate to form a paste-like substance, making slurry filtration difficult and resulting in low product yield.

[0085] Furthermore, industrial-grade manganese sources, such as industrial-grade manganese sulfate, have the advantages of readily available raw materials, large market availability, and high cost-effectiveness. Using this soluble manganese salt to prepare manganese hydrogen phosphate can reduce manufacturing costs. However, industrial-grade manganese sources often contain high levels of impurities, such as calcium ions. Directly reacting this with phosphoric acid or phosphates produces calcium phosphate as a byproduct, resulting in a high calcium ion content and low product purity in the resulting manganese hydrogen phosphate. Furthermore, the resulting manganese hydrogen phosphate also contains high levels of impurities such as sulfate ions and sodium ions, making it unsuitable for direct use as a manganese source for lithium iron manganese phosphate.

[0086] In view of this, an embodiment of the present application provides a method for preparing a manganese hydrogen phosphate precursor, which prepares a manganese hydrogen phosphate precursor with low impurity ion content and high yield through a secondary precipitation reaction.

[0087] The preparation method comprises the following steps: using a complexing agent aqueous solution as a bottom liquid in a reaction container, and filling the reaction container with protective gas; adding a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution to the reaction container under heating and stirring conditions; after the feeding is completed, further aging the obtained reaction material in the reaction container to obtain a manganese hydroxide slurry, wherein the precipitant includes a hydroxide precipitant; filtering and washing the obtained manganese hydroxide slurry to obtain a de-impurity manganese hydroxide filter cake, or filtering and washing the obtained manganese hydroxide slurry and then mixing it with water to obtain a de-impurity manganese hydroxide slurry; mixing the obtained de-impurity manganese hydroxide filter cake or the de-impurity manganese hydroxide slurry with a phosphoric acid aqueous solution under stirring conditions to react to obtain a manganese hydrogen phosphate slurry; filtering, washing, and drying the obtained manganese hydrogen phosphate slurry to obtain a manganese hydrogen phosphate precursor.

[0088] In the present embodiment, a soluble manganese salt is first subjected to a precipitation reaction with a precipitant to prepare manganese hydroxide, and then a manganese hydroxide is subjected to a secondary precipitation reaction with phosphoric acid to prepare a manganese hydrogen phosphate precursor.

[0089] Currently, manganese hydroxide is typically produced by directly reacting soluble manganese salts with ammonia or sodium hydroxide. However, the yield of manganese hydroxide produced by directly reacting soluble manganese salts with ammonia is relatively low, at only approximately 60%. This is because ammonia forms soluble complexes with manganese ions, preventing their full precipitation. Furthermore, ammonia is a weak base and cannot reach the pH necessary for sufficient precipitation. When manganese hydroxide is produced by directly reacting soluble manganese salts with sodium hydroxide, the precipitate produces fine particles, and the manganese ions in the product are easily oxidized. This is because the strong alkalinity of sodium hydroxide and the high hydroxide concentration in the reaction system result in a rapid precipitation rate when hydroxide reacts with manganese ions, resulting in a fine precipitate, such as particles with a volume distribution diameter (Dv50) of less than 5μm. The fine precipitate can easily lead to particle penetration during slurry filtration, resulting in low product yield. Furthermore, the smaller the precipitate, the greater its specific surface area, making it more susceptible to oxidation of the manganese ions to trivalent manganese ions upon exposure to air.

[0090] In the embodiment of the present application, a soluble manganese salt and a precipitant are subjected to a single precipitation reaction under the condition that a complexing agent is fed along with the feed to prepare manganese hydroxide. The complexing agent can help the manganese hydroxide particles grow, which can reduce the precipitation rate of manganese hydroxide and reduce the supersaturation of manganese ions in the solution, thereby preventing the generation of a large number of manganese hydroxide nuclei during the feeding process, which causes the crystals to be unable to grow. Therefore, when the soluble manganese salt and the precipitant react under the condition that the complexing agent is fed along with the feed, both hydroxide and manganese ions can be smoothly precipitated, and the precipitation rate of hydroxide and manganese ions can be reduced, thereby obtaining manganese hydroxide with a larger particle size. Due to the larger particle size of the precipitated manganese hydroxide, the manganese hydroxide slurry is easier to filter and the product yield is also higher; at the same time, the obtained manganese hydroxide has a higher antioxidant property when exposed to air. In some embodiments, the volume distribution particle size D50 of the manganese hydroxide can be 6μm-25μm.

[0091] The preparation method provided in the embodiment of the present application also uses a complexing agent aqueous solution as a base liquid. The function of the base liquid is to promote the effective dispersion of the raw material liquid in the base liquid when two raw material droplets, namely a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution, are added to the reaction container, thereby preventing the formation of fine particles due to local overconcentration.

[0092] The reaction system of the soluble manganese salt and the precipitant-complexing agent is alkaline. The calcium hydroxide formed by the impurity calcium ions in the soluble manganese salt and the hydroxide ions will be slightly soluble in water and will not enter the precipitated manganese hydroxide. At the same time, the sodium ions, sulfate ions, and ammonium ions in the reaction system are also soluble in water, and these impurity ions can be effectively removed during the filtration and washing of the manganese hydroxide slurry. Therefore, the preparation method provided in the embodiments of the present application can obtain manganese hydroxide and manganese hydrogen phosphate precursors with low impurity ion content.

[0093] The purpose of aging treatment after the feeding is to allow sufficient time for the manganese hydroxide crystals to continue to grow. In particular, small particle crystals in the solid and liquid phases will continue to dissolve into ions, and these redissolved ions will continue to grow on the surface of large particle crystals. As a result, the macroscopic manifestation is a decrease in the proportion of small particles and an increase in the size of manganese hydroxide particles. In addition, aging treatment can also reduce the surface energy of the manganese hydroxide particles. When the surface energy of the manganese hydroxide particles is reduced, the manganese hydroxide particles are exposed to higher oxidation resistance in the air during the washing process of the manganese hydroxide slurry, and are less likely to be oxidized due to contact with air.

[0094] The precipitation reaction of manganese hydroxide and phosphoric acid is an acid-base neutralization reaction. The precipitation reaction rate is fast, and the pH value at the reaction end point is 1.5-5.5, which is slightly acidic. At the same time, no by-products are generated. The manganese hydrogen phosphate precursor obtained thereby can have a low impurity ion content.

[0095] Therefore, the present invention provides a high-yield manganese hydrogen phosphate precursor with low impurity ion content through a secondary precipitation reaction. The prepared manganese hydrogen phosphate precursor can be directly used as a manganese source for preparing lithium manganese iron phosphate. Furthermore, the preparation method provided in the present invention has a wide range of raw material sources, low manufacturing costs, and a simple preparation process, making it suitable for large-scale industrial production.

[0096] Figure 7 It is a process flow diagram of the preparation method provided in some embodiments of the present application.

[0097] In some embodiments, the soluble manganese salt may include one or more of industrial-grade manganese sulfate, high-purity manganese sulfate, manganese acetate, manganese chloride, and manganese nitrate.

[0098] Optionally, the mass content of impurity calcium in industrial-grade manganese sulfate may be 0.03%-0.15%.

[0099] The reaction system of the soluble manganese salt and the precipitant-complexing agent is alkaline, and the calcium hydroxide formed by the impurity calcium ions in the soluble manganese salt and the hydroxide will be slightly soluble in water, thus not entering the precipitated manganese hydroxide. At the same time, the sodium ions, sulfate ions, and ammonium ions in the reaction system are also soluble in water, and these impurity ions can be effectively removed during the filtration and washing of the manganese hydroxide slurry. Therefore, even if the preparation method provided in the embodiment of the present application uses industrial-grade manganese sulfate with a low price and high impurity content, it can still obtain a low impurity ion content, high-purity manganese hydroxide and manganese hydrogen phosphate precursor.

[0100] In some embodiments, the concentration of the bottom solution in the reaction container, i.e., the complexing agent aqueous solution, can be 0.1 mol·L -1 -5.0 mol·L -1 , for example, it can be 0.1 mol·L -1 , 0.5 mol·L-1 , 1.0 mol·L -1 , 1.5 mol·L -1 , 2.0 mol·L -1 , 2.5 mol·L -1 、3.0mol·L -1 、3.5mol·L -1 , 4.0 mol·L -1 , 4.5 mol·L -1 , 5.0 mol·L -1 , or a range consisting of any of the above values.

[0101] The function of the base liquid is to promote the effective dispersion of the raw material liquid in the base liquid when the two raw material droplets, i.e., the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution, are added to the reaction vessel, thereby preventing the formation of fine particles due to local overconcentration, which affects the filtration effect, washing effect and product yield.

[0102] When the concentration of the bottom liquid in the reaction vessel is within the above range, the precipitation process of manganese hydroxide will change from forming crystal nuclei to growing crystals, which is conducive to promoting the growth of manganese hydroxide particles. This is because the solubility product K of manganese hydroxide is sp Very small, soluble manganese salts react with precipitants to easily form tiny crystal nuclei. These tiny nuclei can stably exist in the solid-liquid phase, that is, the precipitation reaction is mainly characterized by the formation of crystal nuclei. Macroscopically, the precipitate is small and presents a flocculent or gel-like state, which affects the filtration effect, washing effect, and product yield. When the concentration of the bottom liquid in the reaction vessel is within the above range, these tiny crystal nuclei will be complexed and dissolved by the complexing agent. At this time, the main manifestation is the stable existence of large particles in the solid-liquid phase, causing the precipitation process to shift from mainly forming crystal nuclei to mainly causing crystal growth. Macroscopically, the manganese hydroxide particles gradually grow with increasing feeding time.

[0103] When the concentration of the bottom liquid in the reaction container is within the above range, the yield of manganese hydroxide can be increased.

[0104] Alternatively, the concentration of the bottom solution in the reaction vessel can be 1 mol·L -1 -3.0 mol·L -1 .

[0105] In some embodiments, the shielding gas in the reaction vessel may include one or more of nitrogen, argon, and helium. Passing shielding gas into the reaction vessel can reduce the oxygen content of the reaction vessel. Optionally, the oxygen content of the reaction vessel can be reduced to below 500 ppm, thereby reducing the oxidation problem of manganese ions.

[0106] In some embodiments, the complexing agent may include one or more of ammonia, ammonium salt, ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, and potassium ethylenediaminetetraacetic acid. Alternatively, the ammonium salt may include one or more of ammonium chloride and ammonium sulfate.

[0107] Optionally, the complexing agent in the base solution is of the same type as the complexing agent in the precipitant-complexing agent mixed aqueous solution.

[0108] The precipitant includes a hydroxide precipitant. In some embodiments, the precipitant may include one or both of sodium hydroxide and potassium hydroxide.

[0109] In some embodiments, the concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution can be 0.5 mol·L -1 -5.0 mol·L -1 , for example, it can be 0.5 mol·L -1 , 1.0 mol·L -1 , 1.5 mol·L -1 , 2.0 mol·L -1 , 2.5 mol·L -1 、3.0mol·L -1 、3.5mol·L -1 , 4.0 mol·L -1 , 4.5 mol·L -1 , 5.0 mol·L -1 , or a range consisting of any of the above values.

[0110] The concentration of the complexing agent in the mixed aqueous solution of the precipitant-complexing agent is within the above range. On the one hand, it can smoothly precipitate hydroxide and manganese ions and improve the yield. On the other hand, it can adjust the precipitation rate of hydroxide and manganese ions, thereby obtaining manganese hydroxide particles with larger particle size, which is convenient for filtration. It can also improve the oxidation resistance of manganese hydroxide when exposed to air and reduce oxidation problems during the washing process.

[0111] Optionally, the concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is 1 mol·L -1 -4.0 mol·L -1 .

[0112] In some embodiments, the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution can be 1.0 mol·L -1 -6.0mol·L -1 , for example, it can be 1.0 mol·L -1 , 1.5 mol·L -1 , 2.0 mol·L -1 , 2.5 mol·L -1 、3.0mol·L-1 、3.5mol·L -1 , 4.0 mol·L -1 , 4.5 mol·L -1 , 5.0 mol·L -1 , 5.5 mol·L -1 、6.0mol·L -1 , or any range of the above values. Optionally, the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution is 2.0 mol·L -1 -5.5 mol·L -1 .

[0113] In some embodiments, the concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution may be less than the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution.

[0114] In some embodiments, the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution are added to the reaction container in a co-current feeding manner.

[0115] Alternatively, during the feeding process, the pH value of the reaction system in the reaction vessel can be adjusted within a fluctuation range by adjusting the feed rates of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution. For example, the feed rate of the soluble manganese salt aqueous solution can be fixed, and as the reaction proceeds, the feed rate of the precipitant-complexing agent mixed aqueous solution can be continuously adjusted to adjust the pH value of the reaction system in the reaction vessel within a fluctuation range.

[0116] Optionally, during the feeding process, the pH of the reaction system in the reaction vessel can be controlled to be 7.8-12.0, optionally 8.5-11.5, or 9.5-10.5. The pH at which manganese ions begin to precipitate is 7.8-8.2, and the pH at which precipitation is complete is 9.8-10.4. When the pH is greater than 12, the manganese hydroxide precipitate may redissolve. By adjusting the pH of the reaction system in the reaction vessel within the above range, the manganese ions can be fully precipitated, the precipitate particles can be of an appropriate size, and redissolution of the manganese hydroxide precipitate can be avoided.

[0117] Optionally, during the feeding process, the pH value of the reaction system in the reaction vessel may fluctuate within a range of less than or equal to 0.1, that is, the difference between the maximum and minimum pH values of the reaction system is less than or equal to 0.1.

[0118] Alternatively, the feeding time of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution in the reaction vessel can be 2 hours to 24 hours. The feeding time refers to the time from the start of feeding to the end of feeding.

[0119] In some embodiments, the ratio of the molar amount of hydroxide in the hydroxide precipitant to the molar amount of manganese ions in the soluble manganese salt aqueous solution in the precipitant-complexing agent mixed aqueous solution is 2.0:1-2.4:1, and can optionally be 2.05:1-2.4:1. Using a slight excess of hydroxide can promote sufficient precipitation of manganese ions. The molar amount of hydroxide in the hydroxide precipitant in the precipitant-complexing agent mixed aqueous solution and the molar amount of manganese ions in the soluble manganese salt aqueous solution refer to the amount actually added to the reaction vessel.

[0120] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction vessel under heating and stirring conditions, the stirring rate can be 200 ppm-1000 rpm.

[0121] In some embodiments, in the step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution to the reaction vessel under heating and stirring conditions, the heating temperature may be 40° C. to 80° C. Alternatively, the heating method may be water bath heating or oil bath heating.

[0122] In some embodiments, in the step of further aging the obtained reaction material in the reaction container, the aging time may be 1 hour to 12 hours.

[0123] In some embodiments, in the step of further subjecting the obtained reaction material to an aging treatment in a reaction vessel, the aging treatment temperature may be 25°C-80°C.

[0124] In some embodiments, during the step of further aging the obtained reaction material in the reaction vessel, the stirring rate may be 200 rpm-1000 rpm.

[0125] The purpose of aging treatment after the feeding is to give the manganese hydroxide crystals enough time to continue to grow. In particular, small particle crystals in the solid and liquid phases will continue to dissolve into ions, and these redissolved ions will continue to grow on the surface of large particle crystals. The macroscopic manifestation is a decrease in the proportion of small particles and an increase in the size of manganese hydroxide particles. In addition, aging treatment can also reduce the surface energy of the manganese hydroxide particles. The surface energy of the manganese hydroxide particles is reduced. During the washing process of the manganese hydroxide slurry, the manganese hydroxide particles are exposed to air and have higher oxidation resistance, and are not easily oxidized due to contact with air. As the aging time continues to increase, the growth rate of the manganese hydroxide particles will gradually decrease. At this time, continuing to increase the aging time will increase energy consumption.

[0126] Alternatively, the temperature and stirring rate of the aging treatment may be the same as the temperature and stirring rate of the precipitation reaction (ie, the precipitation reaction of the soluble manganese salt and the precipitant-complexing agent).

[0127] In some embodiments, in the steps of filtering and washing the obtained manganese hydroxide slurry, the washing agent may be water or water containing phosphoric acid and a reducing agent. The purpose of washing is to remove soluble impurities.

[0128] Optionally, the washing method can be rinse.

[0129] Optionally, the washing detergent may be water containing phosphoric acid and a reducing agent. When the manganese hydroxide filter cake is washed with water containing phosphoric acid and a reducing agent, the reducing agent can, on the one hand, reduce a small amount of oxidized trivalent manganese ions on the surface of the manganese hydroxide filter cake to divalent manganese ions. Furthermore, the phosphoric acid can react with the manganese hydroxide to form manganese hydrogen phosphate, which is adsorbed on the surface of the manganese hydroxide filter cake. This can reduce the alkalinity of the surface of the manganese hydroxide filter cake, thereby further improving the oxidation resistance of the manganese hydroxide filter cake.

[0130] Alternatively, the reducing agent in the water containing phosphoric acid and the reducing agent may include one or more of oxalic acid and ascorbic acid.

[0131] Alternatively, the concentration of phosphoric acid in the water containing phosphoric acid and a reducing agent may be 0.01 mol·L -1 -0.1 mol·L -1 , for example, it can be 0.01 mol·L -1 , 0.02 mol·L -1 , 0.03 mol·L -1 , 0.04 mol·L -1 , 0.05mol·L -1 , 0.06 mol·L -1 , 0.07 mol·L -1 , 0.08 mol·L -1 , 0.09 mol·L -1 , 0.1 mol·L -1 , or a range consisting of any of the above values.

[0132] Alternatively, the concentration of the reducing agent in the water containing phosphoric acid and the reducing agent may be 0.001 mol·L -1 -0.1 mol·L -1 , for example, it can be 0.001 mol·L -1 , 0.002mol·L -1 , 0.004 mol·L -1 , 0.006mol·L -1 , 0.008 mol·L -1 , 0.01mol·L -1 , 0.02 mol·L -1 , 0.03 mol·L -1 , 0.04 mol·L-1 , 0.05mol·L -1 , 0.06 mol·L -1 , 0.07 mol·L -1 , 0.08 mol·L -1 , 0.09 mol·L -1 , 0.1 mol·L -1 , or a range consisting of any of the above values.

[0133] Oxidation of manganese hydroxide filter cake primarily occurs on the surface of the filter cake in contact with air. Adding a small amount of phosphoric acid and a reducing agent to the water can improve the oxidation resistance of the manganese hydroxide filter cake. Furthermore, during the washing process, the detergent is in contact with the manganese hydroxide filter cake for a short time, and the concentration of phosphoric acid and reducing agent in the water containing phosphoric acid and reducing agent is too high, resulting in waste of phosphoric acid and reducing agent.

[0134] In some embodiments, the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry is mixed with an aqueous phosphoric acid solution under stirring conditions to react to obtain a manganese hydrogen phosphate slurry. The stirring rate may be 200 ppm-1000 rpm.

[0135] In some embodiments, the concentration of phosphoric acid in the phosphoric acid aqueous solution can be 0.5 mol·L -1 -6.0mol·L -1 , for example, it can be 0.5 mol·L -1 , 1.0 mol·L -1 , 1.5 mol·L -1 , 2.0 mol·L -1 , 2.5 mol·L -1 、3.0mol·L -1 、3.5mol·L -1 , 4.0 mol·L -1 , 4.5 mol·L -1 , 5.0 mol·L -1 , 5.5 mol·L -1 、6.0mol·L -1 , or a range consisting of any of the above values.

[0136] In some embodiments, the molar ratio of manganese ions in the de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry to the molar ratio of phosphoric acid in the phosphoric acid aqueous solution is 1:1-1:1.2, and can be 1:05-1:1.2. Using a slight excess of phosphoric acid can promote sufficient precipitation of manganese ions.

[0137] In some embodiments, the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry is mixed with a phosphoric acid aqueous solution for reaction under stirring to obtain a manganese hydrogen phosphate slurry. The phosphoric acid aqueous solution can be a phosphoric acid-reducing agent mixed aqueous solution.

[0138] Optionally, in some embodiments, the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution may include one or more of oxalic acid and ascorbic acid.

[0139] Alternatively, in some embodiments, the concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution may be 0.001 mol·L -1 -0.1 mol·L -1 , for example, it can be 0.001 mol·L -1 , 0.002mol·L -1 , 0.004 mol·L -1 , 0.006mol·L -1 , 0.008 mol·L -1 , 0.01mol·L -1 , 0.02 mol·L -1 , 0.03 mol·L -1 , 0.04 mol·L -1 , 0.05mol·L -1 , 0.06 mol·L -1 , 0.07 mol·L -1 , 0.08 mol·L -1 , 0.09 mol·L -1 , 0.1 mol·L -1 , or a range consisting of any of the above values.

[0140] A small amount of trivalent manganese ions formed by oxidation may also be present in the de-impurified manganese hydroxide filter cake or the de-impurified manganese hydroxide slurry, which will result in a reduction in the yield and purity of the manganese hydrogen phosphate precursor. Adding a reducing agent to the phosphoric acid aqueous solution can reduce the trivalent manganese ions to divalent manganese ions. The concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution is within the above range, which can reduce a small amount of trivalent manganese ions that may appear in the reaction system to divalent manganese ions, thereby improving the yield and purity of the manganese hydrogen phosphate precursor. At the same time, when the concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution is too high, on the one hand, it will cause waste of raw materials and increase costs. On the other hand, the excess reducing agent may also cause precipitation side reactions with the manganese ions, reducing the product purity.

[0141] In some embodiments, the obtained manganese hydrogen phosphate slurry is filtered, washed with water, and dried to obtain a manganese hydrogen phosphate precursor. The drying temperature may be 80° C.-180° C., and the drying time may be 0.5 h-8.0 h.

[0142] In the above preparation method, unless otherwise specified, all raw materials can be directly purchased.

[0143] In the above preparation method, the water used can be pure water.

[0144] The present invention also provides a manganese hydrogen phosphate precursor prepared by the above-mentioned preparation method.

[0145] The present invention also provides a method for preparing lithium manganese iron phosphate.

[0146] The preparation method comprises the steps of: using the manganese hydrogen phosphate precursor prepared by the above preparation method and a mixture of an iron source, a lithium source and a carbon source as raw materials, and obtaining lithium manganese iron phosphate through sintering treatment.

[0147] In some embodiments, one or more of a source of doping element M, a source of doping element N, a source of doping element Q, and a source of doping element R are also added to the mixed material, where M represents a doping element at the manganese position and the iron position, N represents a doping element at the lithium position, Q represents a doping element at the phosphorus position, and R represents a doping element at the oxygen position.

[0148] The iron source may be an iron-containing compound known in the art that can be used to prepare lithium manganese iron phosphate, for example, may include one or more of ferrous chloride, ferrous nitrate, ferrous sulfate, and ferrous acetate.

[0149] The lithium source may be a lithium-containing compound known in the art that can be used to prepare lithium manganese iron phosphate, for example, may include one or more of Li2CO3, LiOH, Li3PO4, and LiH2PO4.

[0150] The carbon source may include one or more of an organic carbon source and an inorganic carbon source, and may optionally include one or more of glucose, sucrose, starch, fructose, polyvinyl alcohol, polyethylene glycol, and citric acid.

[0151] M represents a doping element for manganese and iron, and may be selected from one or more of Co, Mg, Zn, Ca, Ti, V, Ni, and Cr. The source of the doping element M may include one or more of hydrochloride, nitrate, sulfate, and acetate of the doping element M.

[0152] N represents a doping element for lithium sites, which may be one or more of Zn, Al, Na, K, Mg, Nb, Mo, and W. The source of the doping element N may include one or more of hydrochloride, nitrate, sulfate, and acetate of the doping element N.

[0153] Q represents a doping element for the phosphorus site, and may be selected from one or more of B, S, Si, and N. The source of the doping element Q may include one or more of sulfates, borates, nitrates, and silicates of the doping element Q.

[0154] R represents an oxygen-site doping element, which may be one or more of S, F, Cl, and Br. The source of the doping element R may include one or more of a simple substance of the doping element R and an ammonium salt.

[0155] In the above preparation method, unless otherwise specified, all raw materials can be purchased directly.

[0156] The present application also provides a lithium manganese iron phosphate prepared by the above-mentioned preparation method.

[0157] In some embodiments, lithium manganese iron phosphate may have the chemical formula Li a N b Fe x Mn y M 1-x-y P 1-m Q m O 4-n R n , M represents the doping element for manganese and iron positions, which may be selected from one or more of Co, Mg, Zn, Ca, Ti, V, Ni, and Cr; N represents the doping element for lithium position, which may be selected from one or more of Zn, Al, Na, K, Mg, Nb, Mo, and W; Q represents the doping element for phosphorus position, which may be selected from one or more of B, S, Si, and N; R represents the doping element for oxygen position, which may be selected from one or more of S, F, Cl, and Br; 0.9≤a≤1.1, 0≤b≤0.1, 0<x<1, 0<y<1, 0≤1-xy≤0.1, 0≤m≤0.1, 0≤n≤0.1, and lithium manganese iron phosphate is electrically neutral.

[0158] The surface of lithium manganese iron phosphate is also coated with carbon, which can improve the electronic conductivity of lithium manganese iron phosphate.

[0159] The lithium manganese iron phosphate provided in the embodiment of the present application can be used in a battery cell. The battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet and a negative electrode sheet.

[0160] [Positive electrode]

[0161] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the lithium manganese iron phosphate provided in the embodiments of the present application.

[0162] In some embodiments, the positive electrode film layer may further include other positive electrode active materials. For example, other positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides and modified compounds thereof. As an example, lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. The modified compounds of the above-mentioned positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active materials.

[0163] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0164] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and one or more of carboxymethyl chitosan (CMCS).

[0165] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0166] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0167] [Negative electrode]

[0168] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector.

[0169] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0170] In some embodiments, the negative electrode active material may be a material known in the art. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0171] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. As examples, the binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0172] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. For example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0173] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC)).

[0174] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, deionized water.

[0175] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0176] [Electrolytes]

[0177] Battery cells also include an electrolyte. The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte; it can be selected based on needs. For example, the electrolyte can include one or more of a solid electrolyte, a gel electrolyte, and a liquid electrolyte (i.e., an electrolyte solution).

[0178] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0179] In some embodiments, as examples, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0180] In some embodiments, the solvent may include, but is not limited to, one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an example, the solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and one or more of diethyl sulfone (ESE).

[0181] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0182] [Isolation film]

[0183] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is placed between the positive and negative electrode sheets to prevent internal short circuits.

[0184] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0185] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of fiberglass, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0186] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with the above-mentioned electrolyte, and then subjected to packaging, standing, formation and other processes to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0187] The embodiments of the present application also provide an electrical device, which includes a battery provided in the embodiments of the present application, and the battery is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0188] The electrical device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, according to its usage requirements.

[0189] Figure 6 The diagram is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0190] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0191] Example

[0192] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0193] Example 1-1

[0194] Step 1: Prepare the materials according to the molar ratio of industrial-grade manganese sulfate to sodium hydroxide of 1:2.1.

[0195] Weigh 4.0 mol of industrial-grade manganese sulfate monohydrate, add it into pure water and stir to dissolve it, obtaining 2000 mL of a solution with a manganese ion concentration of 2.0 mol·L -1 The calcium content of industrial-grade manganese sulfate monohydrate is 816.3 ppm.

[0196] Weigh 8.4 mol of sodium hydroxide, add it to pure water, and then add 4.0 mol (based on ammonia monohydrate) of concentrated ammonia water to obtain 2000 mL of sodium hydroxide with a concentration of 4.2 mol·L -1 , ammonia monohydrate concentration is 2.0 mol·L -1 A mixed aqueous solution of precipitant and complexing agent.

[0197] Step 2: Add 3000 mL of pure water and 6.0 mol (based on ammonia monohydrate) of concentrated ammonia water into the reactor to obtain ammonia monohydrate concentration of 2.0 mol·L -1 Start stirring the reactor at a rate of 550 rpm, heat the water bath to a reaction temperature of 55°C and keep warm, and introduce nitrogen as a protective gas into the reactor at a nitrogen flow rate of 2 L min -1 , reduce the oxygen content in the reactor to less than 500ppm. At this time, the online pH meter shows that the pH value of the bottom liquid in the reactor is 10.81.

[0198] Step 3: The manganese sulfate aqueous solution and the precipitant-complexing agent mixed aqueous solution were fed into the reactor in parallel. The feeding rate of the manganese sulfate aqueous solution was fixed at 5.56 mL min. -1 Adjust the feed rate of the precipitant-complexing agent mixed aqueous solution based on the pH change to maintain the pH at 10.00 ± 0.05 during the reaction. The reaction is complete when all the manganese sulfate aqueous solution has been added, and the addition of the precipitant-complexing agent mixed aqueous solution is stopped. The feed time is 6.0 hours.

[0199] Step 4: After the feeding is completed, the reaction material is further aged in the reactor for 2 hours to obtain manganese hydroxide slurry. The aging temperature, pH value, stirring rate, and gas atmosphere are consistent with those in the feeding reaction stage.

[0200] Step 5: After filtering the manganese hydroxide slurry, continue to use water containing phosphoric acid and oxalic acid as a detergent to rinse the filter cake to remove soluble impurities and obtain a decontaminated manganese hydroxide filter cake. The concentration of phosphoric acid in the detergent is 0.05 mol·L -1 , the concentration of oxalic acid is 0.01 mol·L -1 .

[0201] In the impurity-free manganese hydroxide filter cake, the volume distribution particle size Dv50 of manganese hydroxide is 8.6 μm, the mass content of manganese hydroxide is 87.9%, and the rest is mainly free water. Figure 8 This is a scanning electron microscope (SEM) image of manganese hydroxide.

[0202] Step 6: Prepare the materials according to the molar ratio of manganese hydroxide to phosphoric acid in the decontaminated manganese hydroxide filter cake being 1:1.05 and the molar ratio of manganese hydroxide to oxalic acid being 1:0.05.

[0203] 3.15 mol of 85 wt% concentrated phosphoric acid and 0.15 mol of oxalic acid were added to pure water and stirred to dissolve to obtain 2.1 mol·L -1 of phosphoric acid and 0.1 mol·L -1 The method involves preparing a mixed solution of oxalic acid and manganese hydroxide; weighing 3.0 mol (calculated as manganese hydroxide) of the decontaminated manganese hydroxide filter cake and adding it to the mixed solution, stirring continuously to react and generate manganese hydrogen phosphate. Because the reaction between manganese hydroxide and phosphoric acid is exothermic, the reaction temperature reaches a maximum of 70°C. After 4.0 hours of reaction, a manganese hydrogen phosphate slurry is obtained for use. The slurry temperature at this point is 30°C, and the pH at the end of the reaction is 2.11.

[0204] Step 7: After filtering the manganese hydrogen phosphate slurry, rinse with pure water to obtain a manganese hydrogen phosphate filter cake. The water content of the manganese hydrogen phosphate filter cake is 18.9%.

[0205] Step 8: Dry the manganese hydrogen phosphate filter cake in a forced air drying oven for 4.5 hours at a drying temperature of 120° C. to obtain a manganese hydrogen phosphate precursor. Figure 9 This is a scanning electron microscope (SEM) image of the manganese hydrogen phosphate precursor.

[0206] Example 1-2

[0207] The preparation method of the manganese hydrogen phosphate precursor is the same as that of Example 1-1 except for the following differences.

[0208] High-purity manganese sulfate with a calcium content of 41.5 ppm was used as the soluble manganese salt instead of the industrial-grade manganese sulfate in Example 1-1.

[0209] Comparative Example 1-1

[0210] Step 1: Prepare the materials according to the molar ratio of industrial-grade manganese sulfate to phosphoric acid of 1:1.05.

[0211] Weigh 4.0 mol of industrial-grade manganese sulfate monohydrate and 4.2 mol of 85 wt% concentrated phosphoric acid, add them into pure water and stir to dissolve, to obtain 2000 mL of manganese ion concentration of 2.0 mol·L -1 , phosphoric acid concentration is 2.1 mol·L -1The calcium content of industrial-grade manganese sulfate monohydrate is 816.3 ppm.

[0212] Step 2: Prepare materials according to the molar ratio of industrial-grade manganese sulfate to sodium hydroxide of 1:2.1.

[0213] Weigh 8.4 mol of sodium hydroxide and add it to pure water, stirring and dissolving to obtain 2000 mL of a solution with a hydroxide ion concentration of 4.2 mol·L -1 of alkaline solution.

[0214] Step 3: Add 3000 mL of pure water to the reactor as the base liquid. Start stirring the reactor at a stirring rate of 550 rpm, heat the water bath to a reaction temperature of 55°C and keep warm, and at the same time, introduce nitrogen as a protective gas into the reactor at a nitrogen flow rate of 2 L min -1 , reduce the oxygen content in the reactor to less than 500ppm.

[0215] Step 4: The manganese-phosphorus mixed solution and the alkaline solution were fed into the reactor in parallel. The feeding rate of the manganese-phosphorus mixed solution was fixed at 5.56 mL min. -1 According to the change in pH, the feed rate of the alkaline solution was adjusted to maintain the pH value of the reaction at 3.50 ± 0.05. When all the manganese-phosphorus mixed solution was added, the reaction was completed and the addition of the alkaline solution was stopped. The feeding time was 6.0 hours.

[0216] Step 5: After the feeding is completed, the reaction material is further aged in the reactor for 2 hours to obtain a slurry. The aging temperature, pH value, stirring rate, and gas atmosphere are consistent with those in the feeding reaction stage.

[0217] Step 6: After filtering the slurry, rinse with pure water to obtain a filter cake having a water content of 21.3%.

[0218] Step 7: Dry the filter cake in a forced air drying oven for 4.5 h at a drying temperature of 120° C. to obtain the product.

[0219] Comparative Example 1-2

[0220] Step 1: Prepare the materials according to the molar ratio of industrial-grade manganese sulfate to phosphoric acid of 1:1.05.

[0221] Weigh 4.0 mol of industrial-grade manganese sulfate monohydrate and 4.2 mol of 85 wt% concentrated phosphoric acid, add them into pure water and stir to dissolve, to obtain 2000 mL of manganese ion concentration of 2.0 mol·L -1 , phosphoric acid concentration is 2.1 mol·L -1 The calcium content of industrial-grade manganese sulfate monohydrate is 816.3 ppm.

[0222] Step 2: Prepare the material according to the molar ratio of industrial-grade manganese sulfate to concentrated ammonia water of 1:2.1.

[0223] Weigh 8.4 mol of 20 wt% concentrated ammonia water, add it into pure water and stir evenly to obtain 2000 mL of hydroxide ion concentration of 4.2 mol·L -1 of concentrated ammonia solution.

[0224] Step 3: Add 3000 mL of pure water to the reactor as the base liquid. Start stirring the reactor at a stirring rate of 550 rpm, heat the water bath to a reaction temperature of 55°C and keep warm, and at the same time, introduce nitrogen as a protective gas into the reactor at a nitrogen flow rate of 2 L min -1 , reduce the oxygen content in the reactor to less than 500ppm.

[0225] Step 4: The manganese-phosphorus mixed solution and concentrated ammonia solution were fed into the reactor in parallel. The feeding rate of the manganese-phosphorus mixed solution was fixed at 5.56 mL min. -1 The feed rate of concentrated ammonia solution was adjusted according to the pH change to maintain the pH value at 3.50 ± 0.05 during the reaction. When all the manganese-phosphorus mixed solution was added, the reaction was completed and the addition of concentrated ammonia solution was stopped. The feed time was 6.0 hours.

[0226] Step 5: After the feeding is completed, the reaction material is further aged in the reactor for 2 hours to obtain a slurry. The aging temperature, pH value, stirring rate, and gas atmosphere are consistent with those in the feeding reaction stage.

[0227] Step 6: After filtering the slurry, rinse with pure water to obtain a filter cake having a moisture content of 25.5%.

[0228] Step 7: Dry the filter cake in a forced air drying oven for 4.5 h at a drying temperature of 120° C. to obtain the product.

[0229] The microstructure of the product was observed using a scanning electron microscope (ZEISS Sigma 300).

[0230] 0.2 g of the product obtained in each embodiment and comparative example was weighed into a 100 mL beaker, and digested with 10 mL of 10 wt% nitric acid solution at 120 ° C for 0.5 h, and the volume was fixed with a 100 mL volumetric flask; 1 mL was then pipetted into a 100 mL volumetric flask to obtain a test solution. The manganese ion content and phosphate ion content in the test solution were determined using an inductively coupled plasma emission spectrometer. The test instrument was an Agilent ICP-OES 5800 inductively coupled plasma emission spectrometer.

[0231] Table 1

[0232] Serial number Manganese ion content Phosphate ion content Molar ratio of manganese to phosphorus Example 1-1 32.41wt% 55.80wt% 1:0.996 Example 1-2 32.48wt% 56.03wt% 1:0.998 Comparative Example 1-1 32.33wt% 54.43wt% 1:0.974 Comparative Example 1-2 29.08wt% 49.87wt% 1:0.992

[0233] In the products prepared in Example 1-1 and Example 1-2, the molar ratio of manganese element to phosphorus element is close to 1:1, and the tested manganese ion content and phosphate ion content are close to the theoretical manganese ion content and theoretical phosphate ion content of manganese hydrogen phosphate monohydrate MnHPO4·H2O. This indicates that the products prepared in Example 1-1 and Example 1-2 are manganese hydrogen phosphate monohydrate MnHPO4·H2O.

[0234] In the product prepared in Comparative Example 1-1, the molar ratio of manganese to phosphorus deviates from 1:1, which is presumably due to the generation of a small amount of by-product manganous phosphate Mn3(PO4)2.

[0235] The product prepared in Comparative Examples 1-2 had a molar ratio of manganese to phosphorus close to 1:1. However, the measured manganese ion and phosphate ion contents were both lower than the theoretical manganese ion and phosphate ion contents of manganese hydrogen phosphate monohydrate (MnHPO4·H2O), and closer to the theoretical manganese ion and phosphate ion contents of manganese ammonium phosphate monohydrate (NH4MnPO4·H2O). Furthermore, when the product prepared in Comparative Examples 1-2 was mixed and ground with sodium hydroxide powder, a distinct ammonia odor was detected. Therefore, it is speculated that the product prepared in Comparative Examples 1-2 may be manganese ammonium phosphate monohydrate (NH4MnPO4·H2O).

[0236] 0.2 g of the product obtained in each example and comparative example was weighed into a 100 mL beaker and digested with 10 mL of 10 wt% nitric acid solution at 120° C. for 0.5 h. The solution was then diluted to volume with a 100 mL volumetric flask to obtain a test solution. The sulfate ion content, sodium ion content, and calcium ion content in the test solution were determined using an inductively coupled plasma optical emission spectrometer. The test instrument was an Agilent ICP-OES 5800 inductively coupled plasma optical emission spectrometer.

[0237] Table 2

[0238] Serial number Sulfate ion content (ppm) Sodium ion content (ppm) Calcium ion content (ppm) Product yield Example 1-1 377.54 19.07 41.31 93.7％ Example 1-2 406.30 15.99 32.47 93.3％ Comparative Example 1-1 3638.18 2694.26 713.16 92.1％ Comparative Example 1-2 3585.76 22.50 638.68 91.5％

[0239] From the test results of Example 1-1, Example 1-2, Comparative Example 1-1 and Comparative Example 1-2, it can be seen that by adopting the preparation method provided by the present application, even if industrial-grade manganese sulfate with a higher calcium content is directly selected as a raw material, a product with low calcium ion, low sodium ion and low sulfate ion content can be obtained. In the preparation method of the present application, when manganese hydroxide is prepared by a single precipitation reaction, soluble impurities such as sulfate ions, sodium ions, and ammonium ions are washed away during the filtration and washing process; in addition, by adopting the specific addition sequence of the present application, the obtained manganese hydroxide has good crystallinity, and impurities are not easily included in the crystal. Therefore, the product obtained by the preparation method provided by the present application has a low content of impurity ions and a high yield.

[0240] The manganese hydrogen phosphate prepared in Example 1-1 and Example 1-2 has low contents of sulfate ions, sodium ions, and calcium ions, and can be used as a manganese source for lithium manganese iron phosphate.

[0241] Comparative Example 1-1: Manganese sulfate, phosphoric acid, and sodium hydroxide were reacted together, and the sodium ion and sulfate ion contents in the product reached over 3000 ppm. This may be due to the sodium and sulfur impurities being trapped within the crystals and difficult to wash away. Alternatively, the byproduct, sodium manganese phosphate, is generated, which is insoluble in water, making it difficult for the sodium ions to be washed away.

[0242] Comparative Examples 1-3

[0243] The preparation method of the manganese hydrogen phosphate precursor is the same as that of Example 1-1 except for the following differences.

[0244] 3000 mL of pure water was used as the bottom liquid of the reactor.

[0245] Comparative Examples 1-4

[0246] The preparation method of the manganese hydrogen phosphate precursor is the same as that of Example 1-1 except for the following differences.

[0247] Weigh 8.4 mol of sodium hydroxide and add it to pure water to obtain 2000 mL of sodium hydroxide with a concentration of 4.2 mol·L -1 of an aqueous solution of precipitant.

[0248] Comparative Examples 1-5

[0249] The preparation method of the manganese hydrogen phosphate precursor is the same as that of Example 1-1 except for the following differences.

[0250] 3000 mL of pure water was used as the bottom liquid of the reactor.

[0251] Weigh 8.4 mol of sodium hydroxide and add it to pure water to obtain 2000 mL of sodium hydroxide with a concentration of 4.2 mol·L -1 of an aqueous solution of precipitant.

[0252] Table 3

[0253]

[0254] Table 4

[0255]

[0256] As can be seen from the test results in Tables 3 and 4, the present application uses a complexing agent aqueous solution as the base liquid, and allows a soluble manganese salt and a precipitant to undergo a single precipitation reaction under the condition that the complexing agent is fed together, thereby preparing manganese hydroxide with a larger particle size, thereby improving the filtering and washing effects of the manganese hydroxide slurry, and can also prepare a manganese hydrogen phosphate precursor with a low impurity ion content and a high yield.

[0257] The manganese hydroxide prepared in Comparative Examples 1-3 to 1-5 had fine particles and a flocculent or gel-like precipitate, making it difficult to filter and subject to particle percolation. Furthermore, the product was easily oxidized to form brownish-black manganese oxyhydroxide. This brownish-black manganese oxyhydroxide reacted slowly with phosphoric acid and was carried over into the manganese hydrogen phosphate precursor, affecting the purity and yield of the precursor.

[0258] Example 2-1

[0259] Step 1: Prepare the materials according to the molar ratio of industrial-grade manganese sulfate to sodium hydroxide of 1:2.1.

[0260] Weigh 4.0 mol of industrial-grade manganese sulfate monohydrate, add it into pure water and stir to dissolve it, obtaining 2000 mL of a solution with a manganese ion concentration of 2.0 mol·L -1 The calcium content of industrial-grade manganese sulfate monohydrate is 816.3 ppm.

[0261] Weigh 8.4 mol of sodium hydroxide, add it to pure water, and then add 4.0 mol (based on ammonia monohydrate) of concentrated ammonia water to obtain 2000 mL of sodium hydroxide with a concentration of 4.2 mol·L -1 , ammonia monohydrate concentration is 2.0 mol·L -1 A mixed aqueous solution of precipitant and complexing agent.

[0262] Step 2: Add 3000 mL of pure water and 3.0 mol (based on ammonia monohydrate) of concentrated ammonia water into the reactor to obtain ammonia monohydrate concentration of 1.0 mol·L -1 Start stirring the reactor at a rate of 550 rpm, heat the water bath to a reaction temperature of 55°C and keep warm, and introduce nitrogen as a protective gas into the reactor at a nitrogen flow rate of 2 L min -1 , reduce the oxygen content in the reactor to less than 500ppm.

[0263] Step 3: The manganese sulfate aqueous solution and the precipitant-complexing agent mixed aqueous solution were fed into the reactor in parallel. The feeding rate of the manganese sulfate aqueous solution was fixed at 5.56 mL min. -1 Adjust the feed rate of the precipitant-complexing agent mixed aqueous solution based on the pH change to maintain the pH at 10.00 ± 0.05 during the reaction. The reaction is complete when all the manganese sulfate aqueous solution has been added, and the addition of the precipitant-complexing agent mixed aqueous solution is stopped. The feed time is 6.0 hours.

[0264] Step 4: After the feeding is completed, the reaction material is further aged in the reactor for 2 hours to obtain manganese hydroxide slurry. The aging temperature, pH value, stirring rate, and gas atmosphere are consistent with those in the feeding reaction stage.

[0265] Step 5: After filtering the manganese hydroxide slurry, continue to use water containing phosphoric acid and oxalic acid as a detergent to rinse the filter cake to remove soluble impurities and obtain a decontaminated manganese hydroxide filter cake. The concentration of phosphoric acid in the detergent is 0.05 mol·L -1 , the concentration of oxalic acid is 0.01 mol·L -1 .

[0266] In the decontaminated manganese hydroxide filter cake, the volume distribution particle size Dv50 of manganese hydroxide is 6.4 μm, the mass content of manganese hydroxide is 71.4%, and the rest is mainly free water.

[0267] Step 6: Prepare the materials according to the molar ratio of manganese hydroxide to phosphoric acid in the decontaminated manganese hydroxide filter cake being 1:1.05 and the molar ratio of manganese hydroxide to oxalic acid being 1:0.05.

[0268] 3.15 mol of 85 wt% concentrated phosphoric acid and 0.15 mol of oxalic acid were added to pure water and stirred to dissolve to obtain 2.1 mol·L -1 of phosphoric acid and 0.1 mol·L -1 Weigh 3.0 mol (calculated as manganese hydroxide) of the above-mentioned de-mixed manganese hydroxide filter cake and add it to the mixed solution and continue stirring to react to generate manganese hydrogen phosphate. After the reaction is completed for 4.0 h, a manganese hydrogen phosphate slurry is obtained for standby use.

[0269] Step 7: After filtering the above-mentioned manganese hydrogen phosphate slurry, rinse it with pure water to obtain a manganese hydrogen phosphate filter cake.

[0270] Step 8: Dry the manganese hydrogen phosphate filter cake in a forced air drying oven for 4.5 hours at a drying temperature of 120° C. to obtain a manganese hydrogen phosphate precursor.

[0271] Example 2-2

[0272] Step 1: Prepare the materials according to the molar ratio of industrial-grade manganese sulfate to sodium hydroxide of 1:2.1.

[0273] Weigh 4.0 mol of industrial-grade manganese sulfate monohydrate, add it into pure water and stir to dissolve it, obtaining 2000 mL of a solution with a manganese ion concentration of 2.0 mol·L -1 The calcium content of industrial-grade manganese sulfate monohydrate is 816.3 ppm.

[0274] Weigh 8.4 mol of sodium hydroxide, add it to pure water, and then add 6.0 mol (based on ammonia monohydrate) of concentrated ammonia water to obtain 2000 mL of sodium hydroxide with a concentration of 4.2 mol·L -1 , ammonia monohydrate concentration is 3.0 mol·L -1 A mixed aqueous solution of precipitant and complexing agent.

[0275] Step 2: Add 3000 mL of pure water and 9.0 mol (based on ammonia monohydrate) of concentrated ammonia water into the reactor to obtain ammonia monohydrate concentration of 3.0 mol·L -1 Start stirring the reactor at a rate of 550 rpm, heat the water bath to a reaction temperature of 55°C and keep warm, and introduce nitrogen as a protective gas into the reactor at a nitrogen flow rate of 2 L min -1 , reduce the oxygen content in the reactor to less than 500ppm.

[0276] Step 3: The manganese sulfate aqueous solution and the precipitant-complexing agent mixed aqueous solution were fed into the reactor in parallel. The feeding rate of the manganese sulfate aqueous solution was fixed at 5.56 mL min. -1 Adjust the feed rate of the precipitant-complexing agent mixed aqueous solution based on the pH change to maintain the pH at 10.00 ± 0.05 during the reaction. The reaction is complete when all the manganese sulfate aqueous solution has been added, and the addition of the precipitant-complexing agent mixed aqueous solution is stopped. The feed time is 6.0 hours.

[0277] Step 4: After the feeding is completed, the reaction material is further aged in the reactor for 2 hours to obtain manganese hydroxide slurry. The aging temperature, pH value, stirring rate, and gas atmosphere are consistent with those in the feeding reaction stage.

[0278] Step 5: After filtering the manganese hydroxide slurry, continue to use water containing phosphoric acid and oxalic acid as a detergent to rinse the filter cake to remove soluble impurities and obtain a decontaminated manganese hydroxide filter cake. The concentration of phosphoric acid in the detergent is 0.05 mol·L -1 , the concentration of oxalic acid is 0.01 mol·L -1 .

[0279] In the impurity-free manganese hydroxide filter cake, the volume distribution particle size Dv50 of manganese hydroxide is 15.7 μm, the mass content of manganese hydroxide is 90.3%, and the rest is mainly free water.

[0280] Step 6: Prepare the materials according to the molar ratio of manganese hydroxide to phosphoric acid in the decontaminated manganese hydroxide filter cake being 1:1.05 and the molar ratio of manganese hydroxide to oxalic acid being 1:0.05.

[0281] 3.15 mol of 85 wt% concentrated phosphoric acid and 0.15 mol of oxalic acid were added to pure water and stirred to dissolve to obtain 2.1 mol·L -1 of phosphoric acid and 0.1 mol·L -1 Weigh 3.0 mol (calculated as manganese hydroxide) of the above-mentioned de-mixed manganese hydroxide filter cake and add it to the mixed solution and continue stirring to react to generate manganese hydrogen phosphate. After the reaction is completed for 4.0 h, a manganese hydrogen phosphate slurry is obtained for standby use.

[0282] Step 7: After filtering the above-mentioned manganese hydrogen phosphate slurry, rinse it with pure water to obtain a manganese hydrogen phosphate filter cake.

[0283] Step 8: Dry the manganese hydrogen phosphate filter cake in a forced air drying oven for 4.5 hours at a drying temperature of 120° C. to obtain a manganese hydrogen phosphate precursor.

[0284] Table 5

[0285]

[0286] Table 6

[0287]

[0288] As shown in Table 5 and Table 6 test results, under the same conditions of stirring speed, reaction temperature, aging temperature, etc., the higher the complexing agent concentration in the bottom liquid and the precipitation agent-complexing agent mixed aqueous solution, the more conducive the manganese hydroxide crystal is to grow up, and the volume distribution particle size Dv50 of manganese hydroxide also increases. The volume distribution particle size Dv50 of manganese hydroxide is large, the specific surface area of the filter cake is small, and the free water of adsorption is few, so the manganese hydroxide mass content in the filter cake is higher. In addition, the volume distribution particle size Dv50 of manganese hydroxide increases, and the filtering effect of the manganese hydroxide slurry is better, which can also improve the yield of the manganese hydrogen phosphate precursor prepared.

[0289] Example 3-1

[0290] Steps 1 to 4 are the same as those in Example 1-1.

[0291] Step 5: After filtering the manganese hydroxide slurry, continue to rinse it with pure water to remove soluble impurities and obtain a decontaminated manganese hydroxide filter cake.

[0292] In the decontaminated manganese hydroxide filter cake, the volume distribution particle size Dv50 of manganese hydroxide is 8.6 μm, the mass content of manganese hydroxide is 87.3%, and the rest is mainly free water.

[0293] Step 6: Prepare the materials according to the molar ratio of manganese hydroxide to phosphoric acid in the decontaminated manganese hydroxide filter cake being 1:1.05 and the molar ratio of manganese hydroxide to oxalic acid being 1:0.05.

[0294] 3.15 mol of 85 wt% concentrated phosphoric acid and 0.15 mol of oxalic acid were added to pure water and stirred to dissolve to obtain 2.1 mol·L -1 of phosphoric acid and 0.1 mol·L -1 Weigh 3.0 mol (calculated as manganese hydroxide) of the above-mentioned de-mixed manganese hydroxide filter cake and add it to the mixed solution and continue stirring to react to generate manganese hydrogen phosphate. After the reaction is completed for 4.0 h, a manganese hydrogen phosphate slurry is obtained for standby use.

[0295] Step 7: After filtering the above-mentioned manganese hydrogen phosphate slurry, rinse it with pure water to obtain a manganese hydrogen phosphate filter cake.

[0296] Step 8: Dry the manganese hydrogen phosphate filter cake in a forced air drying oven for 4.5 hours at a drying temperature of 120° C. to obtain a manganese hydrogen phosphate precursor.

[0297] Table 7

[0298] Serial number detergent Manganese hydroxide filter cake color Appearance of manganese hydroxide filter cake Example 1-1 Water containing phosphoric acid and oxalic acid off white Pink powder, no black impurities Example 3-1 pure water brown-black Pink powder with a small amount of black impurities

[0299] Table 8

[0300]

[0301] From the test results in Tables 7 and 8, it can be seen that Example 3-1 uses pure water to wash the manganese hydroxide filter cake. Since pure water contains oxygen, the manganese hydroxide on the surface of the manganese hydroxide filter cake will be oxidized to form brown-black manganese hydroxide. The brown-black manganese hydroxide reacts with phosphoric acid at a low rate and will be entrained in the manganese hydrogen phosphate precursor, affecting the yield and purity of the precursor. By using water containing phosphoric acid and oxalic acid to wash the manganese hydroxide filter cake, on the one hand, oxalic acid can reduce a small amount of oxidized trivalent manganese ions on the surface of the manganese hydroxide filter cake to divalent manganese ions. On the other hand, phosphoric acid can also react with manganese hydroxide to form manganese hydrogen phosphate adsorbed on the surface of the manganese hydroxide filter cake, thereby reducing the alkalinity of the manganese hydroxide filter cake surface, thereby further improving the oxidation resistance of the manganese hydroxide filter cake, and then improving the yield and purity of the manganese hydrogen phosphate precursor.

[0302] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a manganese hydrogen phosphate precursor, characterized in that: The steps include: The complexing agent aqueous solution is used as the bottom liquid of the reaction container, and the reaction container is filled with protective gas; Under heating and stirring conditions, adding a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution into a reaction vessel, and after the feeding is completed, further aging the obtained reaction mass in the reaction vessel to obtain a manganese hydroxide slurry, wherein the precipitant includes a hydroxide precipitant; The obtained manganese hydroxide slurry is filtered and washed to obtain a de-impurified manganese hydroxide filter cake, or the obtained manganese hydroxide slurry is filtered and washed and then mixed with water to obtain a de-impurified manganese hydroxide slurry; Under stirring conditions, the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry is mixed with a phosphoric acid aqueous solution to react to obtain a manganese hydrogen phosphate slurry; The obtained manganese hydrogen phosphate slurry is filtered, washed with water and dried to obtain a manganese hydrogen phosphate precursor.

2. The preparation method according to claim 1, characterized in that The protective gas in the reaction vessel includes one or more of nitrogen, argon, and helium; and / or, The complexing agent includes one or more of ammonia, ammonium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium salt, and ethylenediaminetetraacetic acid potassium salt; and / or, The precipitant comprises one or both of sodium hydroxide and potassium hydroxide; and / or, The soluble manganese salt includes one or more of industrial-grade manganese sulfate, high-purity manganese sulfate, manganese acetate, manganese chloride, and manganese nitrate.

3. The preparation method according to any one of claims 1 to 2, characterized in that The concentration of the bottom liquid in the reaction container is 0.1 mol·L -1 -5.0 mol·L -1 .

4. The preparation method according to claim 3, characterized in that The concentration of the bottom liquid in the reaction container is 1 mol·L -1 -3.0 mol·L -1 .

5. The preparation method according to any one of claims 1 to 4, characterized in that The concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is 0.5 mol·L -1 -5.0 mol·L -1 and / or, The concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution is 1.0 mol·L -1 -6.0mol·L -1 .

6. The preparation method according to claim 5, characterized in that The concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is 1 mol·L -1 -4mol·L -1 and / or, The concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution is 2.0 mol·L -1 -5.5 mol·L -1 .

7. The preparation method according to any one of claims 1 to 6, characterized in that The concentration of the complexing agent in the precipitant-complexing agent mixed aqueous solution is lower than the concentration of the precipitant in the precipitant-complexing agent mixed aqueous solution.

8. The preparation method according to any one of claims 1 to 7, characterized in that The step of adding the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution into the reaction vessel satisfies at least one of the following conditions (1) to (5): (1) The feeding method is parallel flow feeding; (2) the feeding time of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution in the reaction vessel is 2 hours to 24 hours; (3) During the feeding process, the pH value of the reaction system in the reaction vessel is adjusted within a fluctuation range by adjusting the feeding rate of the soluble manganese salt aqueous solution and the precipitant-complexing agent mixed aqueous solution; (4) During the feeding process, the pH value of the reaction system in the reaction vessel is controlled to be 7.8-12.0; (5) During the feeding process, the pH value of the reaction system in the reaction vessel fluctuates within a range of less than or equal to 0.

1.

9. The preparation method according to any one of claims 1 to 8, characterized in that In the step of adding a soluble manganese salt aqueous solution and a precipitant-complexing agent mixed aqueous solution into a reaction vessel under heating and stirring conditions, The stirring rate is 200ppm-1000rpm; and / or, The heating temperature is 40°C-80°C; and / or, The heating method is water bath heating or oil bath heating.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The obtained reaction material is further subjected to an aging step in a reaction vessel. The aging time is 1h-12h; and / or, The aging temperature is 25°C-80°C; and / or, The stirring rate is 200 rpm-1000 rpm.

11. The preparation method according to any one of claims 1 to 10, characterized in that: In the step of filtering and washing the obtained manganese hydroxide slurry, The washing detergent is water or water containing phosphoric acid and a reducing agent; and / or, The washing method is rinsing.

12. The preparation method according to claim 11, characterized in that The washing detergent is water containing phosphoric acid and a reducing agent. The reducing agent includes one or more of oxalic acid and ascorbic acid; and / or, The concentration of phosphoric acid in the water containing phosphoric acid and a reducing agent is 0.01 mol·L -1 -0.1 mol·L -1 and / or, The concentration of the reducing agent in the water containing phosphoric acid and the reducing agent is 0.001 mol·L -1 -0.1 mol·L -1 .

13. The preparation method according to any one of claims 1 to 12, characterized in that: The volume distribution particle size D50 of the obtained manganese hydroxide is 6 μm-25 μm.

14. The preparation method according to any one of claims 1 to 13, characterized in that The step of mixing the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry with a phosphoric acid aqueous solution to react under stirring conditions to obtain a manganese hydrogen phosphate slurry satisfies at least one of the following conditions (1) to (3): (1) The stirring rate is 200ppm-1000rpm; (2) The concentration of phosphoric acid in the phosphoric acid aqueous solution is 0.5 mol·L -1 -6.0mol·L -1 ; (3) The ratio of the molar amount of manganese ions in the de-impurified manganese hydroxide filter cake or the de-impurified manganese hydroxide slurry to the molar amount of phosphoric acid in the phosphoric acid aqueous solution is 1:1-1:1.

2.

15. The preparation method according to any one of claims 1 to 14, characterized in that: In the step of mixing the obtained de-impurified manganese hydroxide filter cake or de-impurified manganese hydroxide slurry with a phosphoric acid aqueous solution to react and obtain a manganese hydrogen phosphate slurry, the phosphoric acid aqueous solution is a phosphoric acid-reducing agent mixed aqueous solution, The reducing agent includes one or more of oxalic acid and ascorbic acid, and / or the concentration of the reducing agent in the phosphoric acid-reducing agent mixed aqueous solution is 0.001 mol·L -1 -0.1 mol·L -1 .

16. The preparation method according to any one of claims 1 to 15, characterized in that: In the step of filtering, washing and drying the obtained manganese hydrogen phosphate slurry to obtain a manganese hydrogen phosphate precursor, the drying temperature is 80° C.-180° C.; and / or the drying time is 0.5 h-8.0 h.

17. A manganese hydrogen phosphate precursor, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 16.

18. A method for preparing lithium manganese iron phosphate, characterized in that: The method comprises the following steps: using a mixture of a manganese hydrogen phosphate precursor prepared by the preparation method according to any one of claims 1 to 16 and an iron source, a lithium source and a carbon source as raw materials, and obtaining lithium manganese iron phosphate through sintering.

19. The preparation method according to claim 18, characterized in that One or more sources of doping elements M, N, Q, and R are also added to the mixed materials, where M represents the doping element at the manganese and iron positions, N represents the doping element at the lithium position, Q represents the doping element at the phosphorus position, and R represents the doping element at the oxygen position.

20. A lithium manganese iron phosphate, characterized in that: It is prepared by the preparation method according to any one of claims 18 to 19.

21. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, characterized in that: The positive electrode film layer comprises lithium manganese iron phosphate prepared by the preparation method according to any one of claims 18-19.

22. A battery, characterized in that: Including the positive electrode sheet according to claim 21.

23. An electrical device, characterized in that: The battery according to claim 22 is used to provide electrical energy.

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