Ferromanganese phosphate precursor, lithium iron manganese phosphate and preparation method thereof, battery cell, battery device and power device

Abstract

The present disclosure relates to a ferromanganese phosphate precursor, lithium iron phosphate and its preparation method, battery cell, battery device and electrical device. The preparation method includes: mixing a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixing an aqueous solution containing an alkaline source with a complexing agent to obtain a second mixed solution, the complexing agent including an aminocarboxylic acid compound; adding the first mixed solution and the second mixed solution to an alkaline solution containing a complexing agent for single-phase coprecipitation to obtain ferromanganese hydroxide; mixing ferromanganese hydroxide with an aqueous solution containing an antioxidant to obtain a first slurry; mixing an aqueous solution containing a phosphorus source with the first slurry to react until the system pH is 4.5-6 to obtain ferromanganese phosphate; ferromanganese phosphate is mixed with a lithium source for sintering to obtain lithium iron manganese phosphate. The preparation method can more accurately adjust the molar ratio of manganese, iron ions and phosphate ions in the precursor to obtain a higher purity precursor, and then obtain higher purity lithium iron manganese phosphate.

Description

Technical Field

[0001] The present disclosure relates to the field of batteries, and in particular to a manganese ferrophosphate precursor, lithium manganese ferrophosphate and a preparation method thereof, a battery cell, a battery device and an electrical device. Background Art

[0002] Currently, lithium-containing transition metal phosphates are important cathode active materials for lithium-ion battery cells. Due to their stable structure and high energy density, they are widely used in various lithium-ion battery cells, such as power batteries. However, the purity of lithium-containing transition metal phosphates still needs to be improved. Summary of the Invention

[0003] The present disclosure provides a ferromanganese phosphate precursor, lithium iron manganese phosphate, and a preparation method thereof, a battery cell, a battery device, and an electrical device. The ferromanganese phosphate precursor can be precisely adjusted to adjust the molar ratio of manganese ions, iron ions, and phosphate ions to prepare a high-purity ferromanganese phosphate precursor, thereby obtaining a high-purity lithium iron manganese phosphate positive electrode active material.

[0004] In a first aspect, the present disclosure provides a method for preparing a ferromanganese phosphate precursor, comprising: mixing a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixing an aqueous solution containing an alkaline source with a chelating agent to obtain a second mixed solution, wherein the chelating agent includes an aminocarboxylic acid compound; adding the first mixed solution and the second mixed solution in parallel to an alkaline solution containing a chelating agent to carry out a single-phase coprecipitation reaction to obtain a ferromanganese hydroxide slurry; mixing the ferromanganese hydroxide slurry with an aqueous solution containing an antioxidant to obtain a first slurry; mixing an aqueous solution containing a phosphorus source with the first slurry, reacting until the pH of the system is 4.5-6, to obtain a ferromanganese phosphate precursor; mixing the ferromanganese phosphate precursor with a lithium source and then sintering the mixture to obtain a lithium ferromanganese phosphate positive active material.

[0005] In some embodiments, the preparation method includes: mixing an aqueous solution containing a phosphorus source with a first slurry, and reacting until the pH of the system is 5.2-5.4 to obtain a ferromanganese phosphate precursor.

[0006] In some embodiments, the aminocarboxylic acid compound includes one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, aminotriacetic acid, and ethylenediaminediacetic acid.

[0007] In some embodiments, the amount of the complexing agent added to the second mixed solution is 1%-3% of the total molar amount of ferrous ions and manganese ions.

[0008] In some embodiments, the concentration of the complexing agent in the alkaline solution containing the complexing agent is 0.01-0.05 mol / L.

[0009] In some embodiments, the pH value of the solution during the single-phase co-precipitation reaction is 9.6-10.4.

[0010] In some embodiments, the single-phase co-precipitation reaction time is 270-300 min.

[0011] In some embodiments, the temperature of the single-phase co-precipitation reaction is 55°C-65°C.

[0012] In some embodiments, mixing the aqueous solution containing the phosphorus source with the first slurry includes adding the aqueous solution containing the phosphorus source to the first slurry.

[0013] In some embodiments, the preparation method further comprises: subjecting the ferromanganese hydroxide slurry to an impurity removal treatment.

[0014] In some embodiments, the manganese source includes one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0015] In some embodiments, the iron source includes one or more of ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous acetate.

[0016] In some embodiments, the acid in the acidic solution includes one or more of sulfuric acid, hydrochloric acid, nitric acid, and ascorbic acid.

[0017] In some embodiments, the alkaline source includes one or more of sodium hydroxide and potassium hydroxide.

[0018] In some embodiments, the antioxidant comprises one or more of ascorbic acid, erythorbic acid.

[0019] In some embodiments, the phosphorus source includes one or more of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

[0020] In the second aspect, the present disclosure provides a ferromanganese phosphate precursor, the chemical formula of the ferromanganese phosphate precursor is (Mn x Fe (1-x) )3(PO4) y nH2O, 0<x<1.00, 2.00≤y≤2.01, 0≤n≤10; the ferromanganese phosphate precursor includes primary particles and secondary particles formed by agglomeration of the primary particles; the primary particles include flaky particles, and the secondary particles include spherical particles.

[0021] In some embodiments, the volume particle size distribution Dv50 of the ferromanganese phosphate precursor is 36-44 μm.

[0022] In some embodiments, the mass content of sodium in the ferromanganese phosphate precursor is less than or equal to 35 ppm.

[0023] In some embodiments, the mass content of sulfur in the ferromanganese phosphate is less than or equal to 110 ppm.

[0024] In a third aspect, the present disclosure provides a lithium manganese iron phosphate, which is prepared by the manganese iron phosphate precursor of the second aspect of the present disclosure.

[0025] In a fourth aspect, the present disclosure provides a battery cell comprising the lithium manganese iron phosphate according to the third aspect of the present disclosure.

[0026] In a fifth aspect, the present disclosure provides a battery device comprising a plurality of battery cells according to the fourth aspect of the present disclosure.

[0027] In a sixth aspect, the present disclosure provides an electrical device comprising the battery cell of the fourth aspect of the present disclosure or the battery device of the fifth aspect of the present disclosure.

[0028] The embodiment of the present disclosure mixes a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixes an aqueous solution containing an alkaline source with a complexing agent to obtain a second mixed solution, wherein the complexing agent includes an aminocarboxylic acid compound; the first mixed solution and the second mixed solution are added to an alkaline solution containing a complexing agent in parallel to perform a single-phase coprecipitation reaction to obtain a manganese hydroxide ferromanganese slurry, thereby achieving uniform mixing of manganese ions and iron ions at the atomic level and more accurately adjusting the molar ratio of metal ions. And by mixing an aqueous solution containing a phosphorus source with the first slurry and reacting until the pH of the system is 4.5-6, the hydrogen ions in the phosphorus source can be quickly and completely ionized, thereby reducing the formation of internal impurities and residual surface impurities, and preparing a higher-purity manganese ferrophosphate precursor, thereby obtaining a higher-purity manganese iron phosphate lithium positive electrode active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on the drawings without inventive effort.

[0030] Figure 1 Schematic diagram of a battery cell provided for some embodiments of the present disclosure.

[0031] Figure 2 A schematic diagram of an electrical device provided in some embodiments of the present disclosure.

[0032] Figure 3 This is a scanning electron microscope image of the manganese ferrohydroxide prepared in Example 1 of the present disclosure.

[0033] Figure 4This is a low-magnification scanning electron microscope image of the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0034] Figure 5 This is a high-magnification scanning electron microscope image of the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0035] Figure 6 This is the EDS element distribution diagram of O, Fe, Mn, and P in the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0036] Figure 7 This is the EDS element distribution diagram of Mn in the manganese-containing ferrophosphate precursor prepared in Example 1 of the present disclosure.

[0037] Figure 8 This is the EDS element distribution diagram of Fe in the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0038] Figure 9 This is the EDS element distribution diagram of P in the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0039] Figure 10 This is the EDS element distribution diagram of O in the ferromanganese phosphate precursor prepared in Example 1 of the present disclosure.

[0040] In the accompanying drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0041] Below, with appropriate reference to the accompanying drawings, the embodiments of the manganese ferrophosphate precursor, lithium manganese ferrophosphate and its preparation method, battery cell, battery device and electrical device disclosed in the present invention are specifically disclosed in detail. 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 disclosure and are not intended to limit the subject matter described in the claims.

[0042] " scope " disclosed in the present disclosure 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 selected lower limit and upper limit define the boundary of special scope.The scope that this mode limits can be to include end value or not include end value, and can be combined arbitrarily, and promptly any lower limit can form a scope with any upper limit combination.For example, if the scope of 60-120 and 80-110 is listed for specific parameter, 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 listed, and if the maximum range value 3,4 and 5 listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.In the present disclosure, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, and 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.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of the present disclosure.

[0044] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of the present disclosure.

[0045] Unless otherwise specified, all steps of the present disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means 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.

[0046] In the present disclosure, the terms "plurality" and "multiplicity" refer to two or more.

[0047] In the description of the embodiments of the present disclosure, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0048] Unless otherwise stated, the test temperature of each parameter mentioned in this disclosure is 25°C.

[0049] Currently, the main methods for industrial-scale production of lithium manganese iron phosphate cathode active materials are solid-phase methods (e.g., high-temperature solid-phase methods and carbothermal reduction methods) and liquid-phase methods (e.g., co-precipitation methods). Solid-phase methods struggle to achieve uniform mixing of the Mn and Fe elements at the atomic / molecular level. Furthermore, the particles of cathode active materials prepared by these methods tend to agglomerate and are difficult to control, resulting in poor phase homogeneity in the cathode active materials. In contrast, co-precipitation methods, which enable the multi-phase co-precipitation of Mn and Fe elements, are currently the most promising method for industrial-scale precursor production. The quality of the precursor directly impacts the physicochemical properties and electrochemical performance of the cathode active material. The quality of precursors prepared by different methods varies significantly, making the preparation method of the precursor particularly critical.

[0050] How to make Mn and Fe elements co-precipitate homogeneously and achieve uniform mixing at the atomic / molecular level, while accurately adjusting the molar ratio of manganese ions, iron ions and phosphate ions in the ferromanganese phosphate precursor to obtain a higher purity ferromanganese phosphate precursor is also a technical problem that needs to be solved urgently.

[0051] In view of this, the present disclosure provides a ferromanganese phosphate precursor, lithium iron manganese phosphate and its preparation method, battery cell, battery device and power-consuming device, which can more accurately adjust the molar ratio of manganese ions, iron ions and phosphate ions in the ferromanganese phosphate precursor to prepare a higher-purity ferromanganese phosphate precursor, and then obtain a higher-purity lithium iron manganese phosphate positive electrode active material.

[0052] The present disclosure provides a method for preparing lithium manganese iron phosphate, which comprises the following steps: mixing a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixing an aqueous solution containing an alkaline source with a complexing agent to obtain a second mixed solution, wherein the complexing agent comprises an aminocarboxylic acid compound; adding the first mixed solution and the second mixed solution in parallel to an alkaline solution containing the complexing agent to carry out a single-phase coprecipitation reaction to obtain a ferromanganese hydroxide slurry; mixing the ferromanganese hydroxide slurry with an aqueous solution containing an antioxidant to obtain a first slurry; mixing an aqueous solution containing a phosphorus source with the first slurry, reacting until the pH of the system is 4.5-6, to obtain a ferromanganese phosphate precursor; and mixing the ferromanganese phosphate precursor with a lithium source and then sintering the mixture to obtain a lithium manganese iron phosphate positive electrode active material.

[0053] The solubility product constants of manganese and iron hydroxides are small, and the precipitation rate is fast. At the same time, the solubility product constant of iron hydroxide is much smaller than that of manganese hydroxide. Therefore, it is difficult to achieve single-phase co-precipitation by directly reacting a metal salt solution containing manganese ions and iron ions with an alkaline solution containing ammonia water. At the same time, the reaction is prone to produce a large amount of crystal nucleus colloidal precipitation, making it difficult to effectively filter and remove impurities from the product. In addition, due to the Fe 2+ It is difficult to react with ammonia water to form a stable complex, and it is impossible to directly use the NCM ternary precursor process to prepare manganese iron hydroxide.

[0054] Furthermore, ammonia is highly volatile, and its concentration fluctuates significantly over time and temperature. Furthermore, it is difficult to maintain constant concentration in storage tanks during industrial production. Therefore, using ammonia as a complexing agent can lead to significant fluctuations in the complexing agent concentration in the reaction system during continuous production, resulting in uncontrollable production.

[0055] The disclosed embodiment uses aminocarboxylic acid compounds as complexing agents, and by adjusting the precipitation rate of metal ions in the reaction system, Mn 2+ and Fe 2+ The common complexation and then slowly release with OH - A single-phase coprecipitation reaction occurs to achieve Mn 2+ 、Fe 2+ The molar ratio of manganese ions and iron ions in the ferromanganese phosphate precursor is precisely adjusted by settling at the same order of magnitude.

[0056] In addition, the aminocarboxylic acid compound itself is solid, and the purity of the aminocarboxylic acid compound changes little with time and temperature. Using the aminocarboxylic acid compound as a complexing agent can quantify the reaction materials, making the production process more stable and controllable.

[0057] The embodiment of the present disclosure mixes a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixes an aqueous solution containing an alkaline source with a complexing agent to obtain a second mixed solution, wherein the complexing agent includes an aminocarboxylic acid compound; the first mixed solution and the second mixed solution are added to an alkaline solution containing a complexing agent in parallel to perform a single-phase coprecipitation reaction to obtain a manganese hydroxide ferromanganese slurry, thereby achieving uniform mixing of manganese ions and iron ions at the atomic level and more accurately adjusting the molar ratio of metal ions. And by mixing an aqueous solution containing a phosphorus source with the first slurry and reacting until the pH of the system is 4.5-6, the hydrogen ions in the phosphorus source can be quickly and completely ionized, thereby reducing the formation of internal impurities and residual surface impurities, and preparing a higher-purity manganese ferrophosphate precursor, thereby obtaining a higher-purity manganese iron phosphate lithium positive electrode active material.

[0058] The "single-phase coprecipitation reaction" in the disclosed embodiments refers to the precipitation of divalent manganese ions and divalent iron ions at the same order of magnitude. Specifically, an alkaline solution containing a complexing agent is added to the first mixed solution and the second mixed solution in parallel. After the aminocarboxylic acid compound simultaneously complexes the divalent manganese ions and the divalent iron ions, the alkaline source acts as a precipitant to achieve the precipitation of the divalent manganese ions and the divalent iron ions at the same order of magnitude. This facilitates atomic / molecular mixing of the manganese ions and the iron ions while more accurately adjusting the molar ratio of the metal ions.

[0059] In addition, the reaction process between the aqueous solution containing the phosphorus source and the first slurry is a solid-liquid reaction, which has a fast reaction rate and high uniformity, thereby making it easier to generate well-crystallized ferromanganese phosphate.

[0060] In the embodiments of the present disclosure, the amount of the acidic solution added to the first mixed solution is not limited, as long as it can reduce the oxidation of manganese ions and iron ions. Unless otherwise specified, the manganese ions and iron ions mentioned in the embodiments of the present disclosure refer to divalent manganese ions and divalent iron ions.

[0061] In some embodiments, the preparation method may include: mixing an aqueous solution containing a phosphorus source with a first slurry, and reacting until the pH of the system is 5.2-5.4 to obtain a ferromanganese phosphate precursor. This allows the molar ratio of manganese ions, iron ions, and phosphate ions in the ferromanganese phosphate precursor to be more precisely adjusted to obtain a higher-purity ferromanganese phosphate precursor, thereby obtaining a higher-purity lithium ferromanganese phosphate positive electrode active material.

[0062] In some embodiments, the aminocarboxylic acid compound may include one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, aminotriacetic acid, and ethylenediaminediacetic acid.

[0063] In some embodiments, the amount of the complexing agent added to the second mixed solution can be 1%-3% of the total molar amount of ferrous ions and manganese ions, for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, or a range consisting of any two of the above values. Optionally, it can be 1.5%-2.5%.

[0064] By adjusting the amount of the complexing agent added to the second mixed solution within the above range, the difficulty of separating impurities from the ferromanganese hydroxide particles can be reduced, thereby reducing the impurity content in the ferromanganese hydroxide. In addition, the amount of the complexing agent added within the above range can also reduce the residual amount of manganese ions and iron ions in the reaction mother liquor, improve the utilization rate of manganese ions and iron ions, and further accurately adjust the molar ratio of metal ions in the ferromanganese phosphate precursor.

[0065] In some embodiments, the concentration of the complexing agent in the alkaline solution containing the complexing agent may be 0.01-0.05 mol / L.

[0066] The embodiment of the present disclosure adjusts the concentration of the complexing agent in the alkaline solution containing the complexing agent within the above range, so that the concentration of the complexing agent can be kept consistent during the reaction process, thereby producing a good complexing effect.

[0067] In some embodiments, the pH value of the solution during the single-phase coprecipitation reaction may be 9.6-10.4, for example, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, or a range consisting of any two of the above values, and may be 9.8-10.2.

[0068] According to crystallography, the particle size of a crystal is determined by both the nucleation rate and the growth rate. When the nucleation rate is greater than the growth rate, the product particle size is relatively small; when the nucleation rate is less than the growth rate, the crystals continue to grow, resulting in a larger particle size.

[0069] The disclosed embodiments adjust the pH value of the solution during the single-phase coprecipitation reaction within the above-mentioned range to adjust the nucleation rate and growth rate of the ferromanganese hydroxide particle crystals, thereby obtaining ferromanganese hydroxide particles with a particle size within a suitable range. Furthermore, the generated ferromanganese hydroxide slurry can be easily filtered, and the impurity content within the ferromanganese hydroxide can be reduced (such as reducing the content of sodium ions and sulfate ions). Furthermore, the oxidation resistance of the ferromanganese hydroxide particles can be improved, and the utilization rate of manganese and iron ions in the solution can be increased, further allowing for more precise adjustment of the molar ratio of manganese and iron ions in the ferromanganese phosphate precursor.

[0070] In some embodiments, the pH of the solution during the single-phase coprecipitation reaction may fluctuate within a range of ±1, or optionally ±0.05.

[0071] By adjusting the pH of the solution within the above range, the manganese ions and iron ions in the solution can be completely precipitated to form stable compounds.

[0072] In some embodiments, the volume particle size distribution Dv50 of the manganese ferrohydroxide is 4.3-10.8 μm, optionally 6-10.5 μm.

[0073] Dv50 represents the particle size at which the cumulative volume distribution percentage of a material reaches 50%. This can be measured using a laser particle size analyzer, as per GB / T19077-2016. To perform the test, place 1g of the sample to be tested in a clean small beaker, along with 20ml of deionized water. Ultrasound is then applied at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer is then turned on, the optical system cleaned, and the background automatically measured. The ultrasonically tested solution is stirred to ensure uniform dispersion, then placed in the sample cell as required, and particle size measurement begins. The testing instrument can be a MasterSizer 3000 laser particle size analyzer.

[0074] The volume particle size distribution Dv50 of the manganese ferrohydroxide is within the above range, which is conducive to filtering out impurities such as sodium ions and sulfate ions therein, and at the same time can make the manganese ferrohydroxide less susceptible to oxidation by air.

[0075] In some embodiments, the single-phase co-precipitation reaction time may be 270-300 min.

[0076] In the disclosed embodiments, the reaction time of the single-phase coprecipitation can be adjusted by adjusting the feed rate of the first mixed solution. The feed rate of the second mixed solution is used to stabilize the pH of the solution within the range of 9.6-10.4 during the single-phase coprecipitation reaction. Once the first mixed solution is fed, the feed is stopped and the reaction solution is aged.

[0077] It is understandable that the time for the single-phase co-precipitation reaction includes the time for feeding the first mixed solution and the time for aging treatment after the feeding of the first mixed solution is completed.

[0078] By adjusting the time of the single-phase coprecipitation reaction within the above range, the precipitation rate of the manganese ferrohydroxide can be adjusted, thereby further adjusting the particle size of the manganese ferrohydroxide particles.

[0079] In some embodiments, an inert gas is introduced into the alkaline solution containing the complexing agent to reduce the oxygen content in the solution, thereby further reducing the oxidation of manganese ions and iron ions in subsequent reactions.

[0080] In some embodiments, the inert gas may be one or more of nitrogen, argon, and helium.

[0081] In some embodiments, the temperature of the single-phase co-precipitation reaction can be 55-65°C.

[0082] By adjusting the temperature of the single-phase coprecipitation reaction within the above range, the collision of solute molecules can be promoted, the reaction process can be accelerated, and the self-assembly process of primary particles of manganese ferrohydroxide into secondary particles can be accelerated, thereby causing rapid precipitation.

[0083] In some embodiments, mixing the aqueous solution containing the phosphorus source with the first slurry includes adding the aqueous solution containing the phosphorus source to the first slurry.

[0084] In the disclosed embodiments, the reaction between the aqueous solution of the phosphorus source and the first slurry is a solid-liquid reaction based on an acid-base neutralization reaction. By adding the aqueous solution of the phosphorus source to the first slurry, i.e., employing a continuous acid-base addition reaction, the hydrogen ions in the aqueous solution of the phosphorus source are rapidly and completely ionized, allowing the ionized phosphate radicals to rapidly combine with metal ions to form a stable ferromanganese phosphate precipitate, further improving the purity of the ferromanganese phosphate.

[0085] In the embodiments of the present disclosure, the amount of the aqueous solution containing the phosphorus source added is adjusted according to the reaction cut-off pH.

[0086] In some embodiments, the reaction cut-off pH may fluctuate within a range of ±0.1, and may optionally be ±0.05.

[0087] The precipitate of the above reaction can be obtained by (Mn 0.6 Fe 0.4 )(OH)2、(Mn 0.6 Fe 0.4 )3(PO4)2 and (Mn 0.6 Fe 0.4 )HPO4 or two of them. The above reaction is carried out by adding acid to base, (Mn 0.6 Fe 0.4 )(OH)2 gradually reacts to form (Mn 0.6 Fe 0.4 )3(PO4)2, if phosphoric acid is added continuously, the excess phosphoric acid will react with the newly generated (Mn 0.6 Fe 0.4 )3(PO4)2 reacts again to form (Mn 0.6 Fe 0.4 )HPO4 precipitation. The disclosed embodiments adjust the cutoff pH of the reaction system to 4.5-6 and the fluctuation range of the reaction cutoff pH to further accurately adjust the molar ratio of manganese ions, iron ions, and phosphate ions in the ferromanganous phosphate precursor, thereby reducing internal crystal impurities in the ferromanganous phosphate and further improving the purity of the ferromanganous phosphate.

[0088] In some embodiments, the mass concentration of the antioxidant in the aqueous solution containing the antioxidant may be 0.5%-1.5%.

[0089] Mixing the ferromanganese hydroxide slurry with an aqueous solution containing an antioxidant can reduce the oxidation of manganese ions and iron ions in the ferromanganese hydroxide slurry, further improving the purity of ferromanganous phosphate.

[0090] In some embodiments, the preparation method may further include: subjecting the ferromanganese hydroxide slurry to an impurity removal treatment.

[0091] By removing impurities from ferromanganese hydroxide, the formation of internal impurities and residual surface impurities during the subsequent crystallization of ferromanganese phosphate can be reduced, thereby producing ferromanganese phosphate of higher purity. Furthermore, the mother liquor obtained after the reaction between the aqueous solution containing the phosphorus source and the first slurry can be recycled.

[0092] Exemplarily, the impurity removal process may include filtering and removing impurities.

[0093] In some embodiments, the manganese source may include one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0094] In some embodiments, the iron source may include one or more of ferrous sulfate, ferrous chloride, ferrous nitrate, and ferrous acetate.

[0095] In some embodiments, the acid in the acidic solution may include one or more of sulfuric acid, hydrochloric acid, nitric acid, and ascorbic acid.

[0096] In some embodiments, the alkali source may include one or more of sodium hydroxide and potassium hydroxide.

[0097] In some embodiments, the antioxidant may include one or more of ascorbic acid, erythorbic acid.

[0098] In some embodiments, the phosphorus source may include one or more of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

[0099] In some embodiments, the lithium source may include one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium nitrate, and lithium acetate.

[0100] [Ferromanganous phosphate precursor]

[0101] The present invention provides a ferromanganese phosphate precursor, the chemical formula of which is (Mn x Fe (1-x) )3(PO4) ynH2O, 0<x<1.00, 2.00≤y≤2.01, 0≤n≤10; the ferromanganese phosphate precursor includes primary particles and secondary particles formed by agglomeration of the primary particles; the primary particles include flaky particles, and the secondary particles include spherical particles.

[0102] In some embodiments, the particle size distribution Dv50 of the ferromanganese phosphate precursor may be 36-44 μm.

[0103] The volume particle size distribution Dv50 of the ferromanganese phosphate precursor is within the above range, which can facilitate filtration thereof and further remove impurities such as sodium ions and sulfate ions remaining in the filtration of the ferromanganese hydroxide.

[0104] In some embodiments, the mass content of sodium in the ferromanganese phosphate precursor may be less than or equal to 35 ppm.

[0105] In some embodiments, the mass content of sulfur in ferromanganese phosphate may be less than or equal to 110 ppm.

[0106] [Lithium manganese iron phosphate]

[0107] The present disclosure provides a lithium manganese iron phosphate, which is prepared by using the above-mentioned ferromanganese phosphate precursor.

[0108] [Positive electrode]

[0109] In addition, the present disclosure provides a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer located on at least one side of the positive electrode collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes the above-mentioned lithium manganese iron phosphate.

[0110] In some embodiments, the positive electrode active material may further include one or more of lithium transition metal oxides and modified materials thereof, lithium-containing phosphates and modified materials thereof, lithium titanate, sulfur, selenium, and tellurium.

[0111] Alternatively, the lithium transition metal oxide may include, but is 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 lithium manganese-rich based materials.

[0112] Optionally, the lithium-containing phosphate may include, but is not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese iron phosphate and carbon.

[0113] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material may also include a general formula of Li a Ni b Coc M d O e A f One or more lithium transition metal oxides and modified materials thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0114] As an example, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4 and their respective modified materials.

[0115] The modified materials of the above-mentioned positive electrode active materials may be the positive electrode active materials subjected to doping modification and / or surface coating modification.

[0116] Battery cells experience Li intercalation and deintercalation during the charge and discharge process, resulting in different molar Li contents in different discharge states. The molar Li contents listed in this disclosure for positive electrode active materials refer to the initial state of the material, i.e., the state before addition. The molar Li contents of positive electrode active materials used in battery cells will change after charge and discharge cycles. The molar O contents listed in this disclosure for positive electrode active materials are only theoretical values. Lattice oxygen release can cause changes in the molar O content, and the actual molar O content will also fluctuate.

[0117] In some embodiments, the positive electrode film layer may further include a positive electrode binder, which may include but is not limited to one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0118] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent, which may include but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor grown carbon fibers (VGCF).

[0119] In some embodiments, the positive electrode current collector may be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, the metal foil may be a pure metal, an alloy, or a surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. By way of example, the metal material may include but is not limited to one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. By way of example, the polymer substrate may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector may be formed by forming a metal material on a polymer substrate.

[0120] 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).

[0121] In some embodiments, the battery cell further includes a negative electrode sheet, a separator, and an electrolyte.

[0122] [Negative electrode]

[0123] The structure and composition of the negative electrode plate can be selected according to the type of battery cell, and the embodiments of the present disclosure are not limited thereto.

[0124] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector may have two opposing surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0125] The negative electrode active material can be a negative electrode active material for battery cells that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon beads, silicon-based materials, and tin-based materials. Silicon-based materials may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxides, and tin alloys. However, the present disclosure is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0126] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative 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.

[0127] In some embodiments, the negative electrode film layer may further include a negative electrode binder. For example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0128] In some embodiments, the negative electrode film layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0129] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the 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 other optional additives in a solvent and stirring them evenly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0130] 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) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0131] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer disposed on at least one surface of the negative electrode current collector. The metal material in the metal layer may include one or more of lithium element and lithium alloy.

[0132] A lithium alloy may be an alloy of metallic lithium and other metallic elements or non-metallic elements. For example, the other metallic elements in the lithium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the lithium alloy may include one or more of boron, carbon, and silicon.

[0133] In some embodiments, the negative electrode sheet may be a lithium sheet (foil) or a lithium alloy sheet (foil).

[0134] In some embodiments, the negative electrode plate may include a negative electrode current collector but not a metal layer, thereby forming a negative electrode-free lithium metal battery cell. During the charge and discharge cycle of the negative electrode-free lithium metal battery cell, the lithium in the positive electrode will be precipitated and stripped off in the form of lithium metal on the negative electrode side.

[0135] In some embodiments, the negative electrode current collector may include a metal foil, a conductive polymer material, a carbon material, or a composite current collector. Examples of metal foil include pure metals, alloys, and surface-treated metals, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include but are not limited to copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. Examples of polymer materials include but are not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE). The composite current collector may be formed by forming a metal material on a polymer substrate.

[0136] In some embodiments, the negative electrode plate may be made of foamed metal. The foamed metal may be nickel foam, copper foam, aluminum foam, alloy foam, or carbon foam. When the foamed metal is used as the negative electrode plate, the surface of the foamed metal may or may not be provided with a negative electrode active material.

[0137] As an example, the negative electrode active material may be filled and / or deposited in the negative electrode current collector.

[0138] [Isolation film]

[0139] In some embodiments, the separator is disposed between the positive electrode and the negative electrode. The separator of the embodiment of the present disclosure can be a porous structure separator with good chemical stability and mechanical stability.

[0140] As an example, the primary material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0141] Optionally, an inorganic particle coating, an organic particle coating or an organic / inorganic composite coating may be coated on the surface of the isolation membrane.

[0142] [Electrolytes]

[0143] Battery cells contain an electrolyte, which conducts ions between the positive and negative electrodes. The present disclosure does not specifically limit the type of electrolyte; it can be selected based on specific 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).

[0144] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0145] The type of electrolyte salt is not particularly limited and can be selected according to actual needs.

[0146] In some embodiments, 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 bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0147] The type of solvent is not particularly limited and can be selected according to actual needs.

[0148] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate (PPC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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 diethyl sulfone (ESE). The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0149] 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 the overcharge / fast charge performance of battery cells, additives that improve the high-temperature performance of battery cells, and additives that improve the low-temperature performance of battery cells.

[0150] Among them, the gel electrolyte includes a polymer as a skeleton network and can be used in combination with an ionic liquid-lithium salt.

[0151] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0152] As an example, the polymer of the polymer solid electrolyte may include polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, a polyionic liquid, cellulose, and the like.

[0153] As an example, the inorganic solid electrolyte can be one or more of an oxide solid electrolyte (crystalline perovskite, lithium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor, amorphous sulfide), a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0154] As an example, a composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0155] In some embodiments, the battery cell may further include an outer packaging. The outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0156] 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. For example, the positive electrode sheet, separator and negative electrode sheet are wound on a winding mandrel to form a cylindrical structure. After the winding mandrel is removed, the cylindrical structure is flattened to form a wound battery cell. The electrode assembly is placed in an outer packaging, dried, and then the above-mentioned electrolyte is injected. After vacuum packaging, standing, formation and other processes, a battery cell is obtained.

[0157] The battery cells mentioned in the embodiments of the present disclosure can independently realize the functions of charging and discharging. The battery cells can be rectangular or in other shapes. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0158] The battery apparatus mentioned in the embodiments of the present disclosure may include one or more battery cell assemblies to provide voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or hybrid via a busbar.

[0159] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0160] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0161] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are housed in the case.

[0162] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0163] As an example, the battery cell assembly may also be housed in the box by directly fixing the plurality of battery cells to the box.

[0164] As an example, the housing may include a first housing and a second housing. The first housing and the second housing engage to form an enclosed space within the housing to house the battery cell assembly. Enclosed here means covered or closed, and can be either sealed or unsealed. The first housing may be a top cover or a bottom plate.

[0165] As an example, the box may include a top cover, a frame, and a bottom plate, wherein the top cover and the bottom plate are respectively connected to the frame to form a closed space inside the box to accommodate the battery cell assembly.

[0166] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0167] The technical solutions described in the embodiments of this disclosure are applicable to various electrical devices that use battery cells and battery devices, including, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems. Battery cells and battery devices are used to store or provide electrical energy.

[0168] Figure 2 1 is a schematic diagram of an exemplary electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0169] Example

[0170] 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 used directly without further processing, and all instruments used in the examples are commercially available.

[0171] Test section

[0172] (1) Determination of the microstructure, elemental composition and distribution of ferromanganese hydroxide and ferromanganese hydrogen phosphate

[0173] The microstructure of ferromanganese hydroxide and ferromanganese hydrogen phosphate was observed by scanning electron microscopy (SEM), and the elemental composition and distribution of ferromanganese hydroxide and ferromanganese hydrogen phosphate were observed by energy dispersive spectrometer (EDS).

[0174] (2) Determination of element content in ferromanganese hydroxide and ferromanganese hydrogen phosphate

[0175] Weigh 0.100g of sample into a 50mL centrifuge tube, add 4mL of nitric acid (1:1 volume ratio) and 2mL of perchloric acid (1:1 volume ratio), and heat the mixture in a graphite digester at 120°C for 0.5h. Dose to volume with a 100mL volumetric flask. Then, pipette 1mL into a 100mL volumetric flask and bring to volume to obtain the test solution. Determine the manganese, iron, and phosphorus contents of the test solution using an inductively coupled plasma optical emission spectrometer (ICP-OES). Calculate the element ratios in the sample, and use the same method to determine the content of impurity elements in the sample.

[0176] Example 1

[0177] (1) Preparation of ferromanganese hydroxide

[0178] 3.20 mol of ferrous sulfate heptahydrate and 4.80 mol of manganese sulfate monohydrate were dissolved in deionized water, and the volume was adjusted to 4000 mL. The total metal ion molar concentration of ferrous ions and manganese ions was 2 mol / L. An appropriate amount of concentrated H2SO4 was added dropwise to obtain a first mixed solution.

[0179] 16.80 mol of sodium hydroxide was added to pure water, stirred to dissolve, and the volume was adjusted to 4000 mL. The concentration of sodium hydroxide was 4.2 mol / L. When the solution temperature was close to room temperature, 0.16 mol of ethylenediaminetetraacetic acid (EDTA) was added. The amount of EDTA added was 2% of the total molar amount of ferrous ions and manganese ions. The solution was stirred until completely dissolved to obtain a second mixed solution.

[0180] Under the conditions of a temperature of 60° C. and a stirring speed of 800 rpm, nitrogen gas was continuously introduced into the bottom liquid of the reactor containing EDTA, and an appropriate amount of sodium hydroxide was added to adjust the pH value of the bottom liquid to be stable within the range of 10.00±0.05 to obtain an alkaline solution containing a complexing agent, wherein the EDTA concentration was 0.02 mol / L.

[0181] The first mixed solution and the second mixed solution were respectively injected into the above-mentioned reactor in parallel via peristaltic pumps. The feed rate of the first mixed solution was set to 15.00 mL / min, and the feed rate of the second mixed solution was adjusted in conjunction to stabilize the reaction pH within the range of 10.00 ± 0.05. The feed cutoff condition was that all the first mixed solution was used up. After the feed was completed, the stirring rate was kept unchanged and the aging was continued for 30 minutes to obtain a ferromanganese hydroxide slurry.

[0182] After the ferromanganese hydroxide slurry is cooled to room temperature, it is washed with pure water and subjected to multiple solid-liquid separations to remove impurity ions such as sodium and sulfate to obtain the impurity-removed ferromanganese hydroxide wet material.

[0183] (2) Preparation of ferromanganese phosphate

[0184] The above-mentioned manganese ferrohydroxide wet material is placed in a reactor, and deionized water containing ascorbic acid is added. The mass concentration of ascorbic acid in the deionized water is 1%, the mass ratio of the wet material to the deionized water is 1:1, and the stirring speed is adjusted to ≥600 rpm to form a first slurry.

[0185] 5.60 mol of 85% mass fraction phosphoric acid was mixed with 2000 mL of deionized water and stirred evenly to prepare an aqueous solution containing a phosphorus source, which was added to the reactor containing the first slurry at a feed rate of 8.67 mL / min. To ensure that the metal ions were not oxidized during the reaction, cooling water was passed through the jacket of the reactor, and the temperature of the reaction system was ensured not to exceed 30°C. The feed cutoff condition was that the pH value of the reaction system was stable at 5.30±0.05, the stirring rate was unchanged, and aging was continued for 1 hour to obtain a slurry containing manganese ferrophosphate.

[0186] The slurry containing ferromanganese phosphate was subjected to solid-liquid separation, placed in a vacuum drying oven, and dried at a drying temperature of 90° C. and a vacuum pressure of -0.01 MPa to obtain a high-purity ferromanganese phosphate precursor.

[0187] (3) Preparation of lithium manganese iron phosphate

[0188] The manganese ferrous phosphate precursor is mixed with trilithium phosphate, carbon source glucose and dopant titanium dioxide, and the mixture is subjected to ball milling, spraying and sintering to obtain the manganese ferrous phosphate positive electrode active material.

[0189] Example 2

[0190] The preparation method of ferromanganese hydroxide was the same as that in Example 1, except that the pH of the solution during the single-phase coprecipitation reaction was 9.6.

[0191] Example 3

[0192] The preparation method of ferromanganese hydroxide was the same as that in Example 1, except that the pH of the solution during the single-phase coprecipitation reaction was 9.8.

[0193] Example 4

[0194] The preparation method of ferromanganese hydroxide was the same as that in Example 1, except that the pH of the solution during the single-phase coprecipitation reaction was 10.2.

[0195] Example 5

[0196] The preparation method of ferromanganese hydroxide was the same as that in Example 1, except that the pH of the solution during the single-phase coprecipitation reaction was 10.4.

[0197] Comparative Example 1

[0198] The preparation method of the manganese ferrohydrogen phosphate precursor is the same as that of Example 1 except for the following differences.

[0199] (1) Add 16.80 mol of sodium hydroxide to pure water, stir and dissolve, and when the solution temperature is close to room temperature, add 8.40 mol of ammonia water (mass concentration is 20%) and adjust the volume to 4000 mL to obtain a second mixed solution, in which the concentration of sodium hydroxide is 4.2 mol / L and the concentration of ammonia water is 2.1 mol / L;

[0200] (2) At a temperature of 60°C and a stirring speed of 800 rpm, nitrogen was continuously introduced into the bottom liquid of the reactor containing aqueous ammonia, and the pH value of the bottom liquid was adjusted to be stable within the range of 10.00±0.05 to obtain an alkaline solution containing a complexing agent, wherein the concentration of aqueous ammonia was 1.05 mol / L.

[0201] The particle size of the ferromanganese hydroxide prepared in Examples 1-5 and Comparative Example 1, the impurity content in the ferromanganese hydroxide, and the content of Mn and Fe remaining in the reaction mother liquor are shown in Table 1.

[0202] Table 1

[0203]

[0204] As can be seen from the test results in Table 1, in Examples 1-5, as the pH of the single-phase coprecipitation reaction increases, the nucleation of ferromanganese hydroxide particles is more favorable, and the particle size of the resulting ferromanganese hydroxide is smaller. However, this also causes problems such as difficulty in filtering the slurry and high internal impurity content. Taking into account the effects of particle size on particle antioxidant properties, impurity content, raw material utilization, and subsequent preparation of ferromanganese hydrogen phosphate, the pH value of the single-phase coprecipitation reaction can be controlled within the range of 9.80-10.20.

[0205] Example 6

[0206] The preparation method of ferromanganese hydroxide is the same as that of Example 1, except that the amount of ethylenediaminetetraacetic acid added to the second mixed solution is 1% of the total molar amount of ferrous ions and manganese ions.

[0207] Example 7

[0208] The preparation method of ferromanganese hydroxide is the same as that of Example 1, except that the amount of ethylenediaminetetraacetic acid added to the second mixed solution is 1.5% of the total molar amount of ferrous ions and manganese ions.

[0209] Example 8

[0210] The preparation method of ferromanganese hydroxide is the same as that of Example 1, except that the amount of ethylenediaminetetraacetic acid added to the second mixed solution is 2.5% of the total molar amount of ferrous ions and manganese ions.

[0211] Example 9

[0212] The preparation method of ferromanganese hydroxide is the same as that of Example 1, except that the amount of ethylenediaminetetraacetic acid added to the second mixed solution is 3% of the total molar amount of ferrous ions and manganese ions.

[0213] The particle size of the ferromanganese hydroxide prepared in Example 1 and Examples 6-9, the impurity content in the ferromanganese hydroxide, and the content of Mn and Fe remaining in the reaction mother liquor are shown in Table 2.

[0214] Table 2

[0215]

[0216] As shown in Table 2, with increasing amounts of complexing agent added, the particle size of ferromanganese hydroxide first increases and then gradually stabilizes. Simultaneously, the impurity content in ferromanganese hydroxide first decreases and then increases, demonstrating that a higher amount of complexing agent is not always better. Furthermore, excessive amounts of complexing agent can increase the difficulty of separating impurities from ferromanganese hydroxide and result in excessive residual manganese and iron ions in the mother liquor. Adding a complexing agent in the range of 1.5%-2.5% can further reduce the impurity content in ferromanganese hydroxide, as well as the Mn and Fe contents in the mother liquor.

[0217] Example 10

[0218] The preparation method of manganese hydrogen phosphate is the same as that of Example 1, except that the cutoff pH for the reaction between the aqueous solution containing the phosphorus source and the first slurry is 6.00.

[0219] Example 11

[0220] The preparation method of manganese hydrogen phosphate is the same as that of Example 1, except that the cutoff pH for the reaction between the aqueous solution containing the phosphorus source and the first slurry is 5.50.

[0221] Example 12

[0222] The preparation method of manganese hydrogen phosphate is the same as that of Example 1, except that the cutoff pH for the reaction between the aqueous solution containing the phosphorus source and the first slurry is 5.00.

[0223] Example 13

[0224] The preparation method of manganese hydrogen phosphate is the same as that of Example 1, except that the cutoff pH for the reaction between the aqueous solution containing the phosphorus source and the first slurry is 4.50.

[0225] The mass contents of manganese and iron and the content of impurities in the ferromanganese hydrogen phosphate prepared in Example 1, Examples 10-13 and Comparative Example 1 are shown in Table 3.

[0226] Table 3

[0227]

[0228] The molar ratios of Mn / (Mn+Fe), Fe / (Mn+Fe) and (Mn+Fe) / (PO4) in the manganese hydrogen phosphate prepared in Example 1, Examples 10-13 and Comparative Example 1 are shown in Table 4.

[0229] Table 4

[0230]

[0231] From the test results in Table 3 and Table 4, it can be seen that as the cut-off pH of the reaction between the aqueous solution containing the phosphorus source and the first slurry gradually decreases, the ratio of (Mn+Fe) / (PO4) first gradually approaches 1.50, and then gradually deviates from 1.5. The reason may be that the reaction precipitate can be obtained by (Mn 0.6 Fe 0.4 )(OH)2、(Mn 0.6 Fe 0.4 )3(PO4)2 and (Mn 0.6 Fe 0.4 )HPO4 or two kinds of it, phosphating reaction is carried out by acid into alkali, (Mn 0.6 Fe 0.4 )(OH)2 gradually reacts to form (Mn 0.6 Fe 0.4 )3(PO4)2, when (Mn 0.6 Fe 0.4 When the reaction of )(OH)2 is complete, the ratio of (Mn+Fe) / (PO4) is close to 1.50. If phosphoric acid is added, the excess phosphoric acid will react with the newly generated (Mn 0.6 Fe 0.4 )3(PO4)2 reacts again to form (Mn 0.6 Fe 0.4 )HPO4 precipitates, at which time the (Mn+Fe) / (PO4) ratio will gradually deviate from 1.50 and tend towards 1.00.

[0232] The molar ratio of divalent iron ions and divalent manganese ions in the first mixed solution of Example 1, Examples 10-13 and Comparative Example 1 is 2:3, but the molar ratio of divalent iron ions and divalent manganese ions in Comparative Example 1 in the obtained ferromanganese phosphate is significantly deviated from 2:3. This shows that the preparation method of the embodiment of the present disclosure can accurately adjust the molar ratio of manganese ions and iron ions in the ferromanganese phosphate precursor to prepare a ferromanganese phosphate precursor with higher purity.

[0233] Depend on Figure 3 It can be seen that the morphology of the manganese ferrohydroxide particles is uniform and no obvious difference is observed. Figure 4 and Figure 5It can be seen that the primary particles of ferromanganese phosphate are in a nanosheet structure with uniform thickness, and the secondary particles are in a spherical structure. Figures 6-10 It can be seen that the Mn, Fe, P, and O elements are evenly distributed in ferromanganese phosphate. Combined with the ICP element content determination in Tables 3 and 4, it can be fully demonstrated that the embodiment of the present disclosure successfully prepared ferromanganese phosphate particles with high purity, in which the ratio of manganese and iron can be changed as needed.

[0234] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present disclosure, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present disclosure. In addition, within the scope of the present disclosure, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present disclosure.

Claims

1. A method for preparing lithium manganese iron phosphate, characterized in that: include: Mixing a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixing an aqueous solution containing an alkali source with a complexing agent to obtain a second mixed solution, wherein the complexing agent includes an aminocarboxylic acid compound; adding the first mixed solution and the second mixed solution concurrently to an alkaline solution containing a complexing agent to perform a single-phase coprecipitation reaction to obtain a ferromanganese hydroxide slurry; wherein the concentration of the complexing agent in the alkaline solution containing the complexing agent is 0.01-0.05 mol / L; Mixing the ferromanganese hydroxide slurry with an aqueous solution containing an antioxidant to obtain a first slurry; adding an aqueous solution containing a phosphorus source to the first slurry and reacting until the pH of the system is 5.2-5.4 to obtain a ferromanganese phosphate precursor; The manganese ferrophosphate precursor is mixed with a lithium source and then sintered to obtain a manganese ferrophosphate lithium positive electrode active material.

2. The preparation method according to claim 1, characterized in that The aminocarboxylic acid compound includes one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, aminotriacetic acid and ethylenediaminediacetic acid.

3. The preparation method according to claim 1, characterized in that The amount of the complexing agent added to the second mixed solution is 1%-3% of the total molar amount of ferrous ions and manganese ions.

4. The preparation method according to claim 1, characterized in that The single-phase coprecipitation reaction satisfies one or more of the following conditions (1)-(3): (1) The pH value of the solution during the single-phase coprecipitation reaction is 9.6-10.4; (2) The single-phase coprecipitation reaction time is 270-300 min; (3) The temperature of the single-phase coprecipitation reaction is 55-65°C.

5. The preparation method according to claim 1, characterized in that The preparation method further comprises: performing impurity removal treatment on the ferromanganese hydroxide slurry.

6. The preparation method according to claim 1, characterized in that The manganese source includes one or more of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate; and / or, The iron source includes one or more of ferrous sulfate, ferrous chloride, ferrous nitrate and ferrous acetate; and / or, The acid in the acidic solution includes one or more of sulfuric acid, hydrochloric acid, nitric acid and ascorbic acid; and / or, The alkali source includes one or more of sodium hydroxide and potassium hydroxide; and / or The antioxidant includes one or more of ascorbic acid and erythorbic acid; and / or, The phosphorus source includes one or more of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

7. A ferromanganous phosphate precursor, characterized in that: The chemical formula of the manganese ferrophosphate precursor is (Mn x Fe (1-x) )3(PO4) y ·nH2O, 0<x<1.00, 2.00≤y≤2.01, 0≤n≤10; The ferromanganese phosphate precursor includes primary particles and secondary particles formed by agglomeration of the primary particles; The primary particles include flake particles, and the secondary particles include spherical particles; The ferromanganese phosphate precursor is prepared by the following method: Mixing a divalent manganese source, a divalent iron source and an acidic solution to obtain a first mixed solution; mixing an aqueous solution containing an alkali source with a complexing agent to obtain a second mixed solution, wherein the complexing agent includes an aminocarboxylic acid compound; adding the first mixed solution and the second mixed solution concurrently to an alkaline solution containing a complexing agent to perform a single-phase coprecipitation reaction to obtain a ferromanganese hydroxide slurry; wherein the concentration of the complexing agent in the alkaline solution containing the complexing agent is 0.01-0.05 mol / L; mixing the ferromanganese hydroxide slurry with an aqueous solution containing an antioxidant to obtain a first slurry; An aqueous solution containing a phosphorus source is added to the first slurry, and the reaction is carried out until the pH of the system is 5.2-5.4 to obtain a ferromanganous phosphate precursor.

8. The ferromanganous phosphate precursor according to claim 7, characterized in that The ferromanganese phosphate precursor satisfies one or more of the following conditions (1)-(3): (1) The volume particle size distribution Dv50 of the ferromanganese phosphate precursor is 36-44 μm; (2) The mass content of sodium in the ferromanganese phosphate precursor is less than or equal to 35 ppm; (3) The mass content of sulfur in the ferromanganese phosphate is less than or equal to 110 ppm.

9. A lithium manganese iron phosphate, characterized in that: It is prepared by the ferromanganese phosphate precursor according to claim 7 or 8.

10. A battery cell, characterized in that: Including the lithium manganese iron phosphate as described in claim 9.

11. A battery device, characterized in that: The invention comprises a plurality of battery cells according to claim 10.

12. An electrical device, characterized in that: The battery cell according to claim 10 or the battery device according to claim 11 is included.

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