Manganese iron phosphate, preparation method thereof, lithium manganese iron phosphate and lithium ion battery, and electrical equipment

Abstract

The application discloses a manganese iron phosphate, a preparation method of the manganese iron phosphate, a lithium iron manganese phosphate and a lithium ion battery, and an electrical equipment. The manganese iron phosphate provided by the application comprises secondary agglomerates, the secondary agglomerates are formed by aggregation of a plurality of primary particles, and the primary particles comprise at least two or more nanosheet units stacked in layers. The manganese iron phosphate provided by the application has a morphology of nanosheet units stacked in layers, which is beneficial to lithium insertion during sintering of the positive electrode material and is beneficial to lithium ion transmission during an electrochemical process, so that the charge and discharge capacity and the rate performance of the lithium iron manganese phosphate are improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials technology, specifically to manganese iron phosphate, lithium manganese iron phosphate, lithium-ion batteries, and electrical equipment. Background Technology

[0002] Compared to lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LFP) partially replaces Fe with Mn, increasing the discharge plateau voltage (from 3.4V to 4.1V) and improving energy density (15%-20%), making it one of the most promising cathode materials for power batteries. As a precursor to LFP, the morphology, particle size, specific surface area, pore size, and purity of manganese iron phosphate all have a certain impact on the performance of LFP.

[0003] Currently, the morphologies of prepared ferromanganese phosphate disclosed include spherical, flake-like, and irregular shapes. CN105449207A discloses ferromanganese phosphate with primary particles in flake form, and CN116826040A discloses porous nanoscale ferromanganese phosphate with secondary particles in irregular shapes. However, these morphologies only represent primary particles and secondary agglomerates. When ferromanganese phosphate is ground to the nanoscale, the morphology of the secondary agglomerates is completely destroyed, and the morphology of the primary particles is also damaged to varying degrees. After preparing lithium iron phosphate from ferromanganese phosphate with destroyed morphology, the electrochemical performance of lithium iron phosphate decreases. Summary of the Invention

[0004] The purpose of this application is to provide a manganese iron phosphate, a lithium manganese iron phosphate, a lithium-ion battery, and electrical equipment to solve the above-mentioned problems.

[0005] The technical problem solved by this application is achieved by the following technical solution.

[0006] This application provides a ferromanganese phosphate, which includes a secondary agglomerate formed by the aggregation of multiple primary particles, wherein each primary particle includes at least two layered stacked nanosheet units.

[0007] Optionally, the nanosheet unit has a square-like morphology and an average side length of 350-450 nm.

[0008] Optionally, the chemical formula of the manganese iron phosphate is Mn. 1-x Fe x PO4, 0.01≤x≤0.99, the manganese iron phosphate satisfies one or more of the following conditions A to D:

[0009] A. The D50 of the manganese iron phosphate is 1-20 μm;

[0010] B. The specific surface area of ​​the aforementioned manganese ferric phosphate is 6-20 m². 2 / g;

[0011] C. The pore volume of the aforementioned manganese ferric phosphate is 0.020–0.030 cm³. 3 / g;

[0012] D. The average pore size of the ferromanganese phosphate is 12-20 nm;

[0013] E. The primary particle comprises at least three layered stacked nanosheet units, optionally, the number of layered stacked nanosheet units is 3-30.

[0014] This application also provides a method for preparing ferromanganese phosphate, comprising: mixing an amorphous ferric phosphate and manganese hydroxide to form a slurry, and then mixing it with phosphoric acid to react and obtain hydrated ferromanganese phosphate;

[0015] The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate.

[0016] Optionally, it includes: adding a slurry formed by mixing amorphous ferric phosphate and manganese hydroxide into a phosphoric acid solution for reaction, and then washing, filtering and drying to obtain hydrated manganese ferric phosphate;

[0017] The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate;

[0018] Optionally, the molar ratio of the amorphous ferric phosphate to the manganese hydroxide is (1-99):(99-1), and the molar ratio of the phosphoric acid to the total molar ratio of the amorphous ferric phosphate and manganese hydroxide is 1:(0.6-1).

[0019] Optionally, the solid content of the slurry is 5%-20%, the slurry is added at a time of 0.5-1.5 hours, and the reaction temperature is 20-100°C.

[0020] Optionally, the drying temperature is 80℃-120℃, and the drying time is 2h-12h;

[0021] Optionally, the heat treatment temperature is 400℃-480℃, and the heat treatment time is 2h-8h.

[0022] Optionally, the method for preparing manganese hydroxide includes: adding soluble manganese salt, a first oxidant and ammonia water in parallel to a base liquid to carry out a first reaction, followed by aging, washing and filtration to obtain manganese hydroxide;

[0023] Optionally, the base solution is dilute ammonia water with a pH of 8-11, the temperature of the first reaction is 5-50℃, the pH of the first reaction is 8.5-10, and the pH of the aging is 8.5-10;

[0024] Optionally, the molar ratio of the soluble manganese salt, the first oxidant, and ammonia is 1:

[0025] (2.5-3.5): (0.4-1.0); the soluble manganese salt includes one or more of manganese sulfate, manganese chloride, and manganese nitrate; the first oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

[0026] Optionally, the method for preparing amorphous ferric phosphate includes: mixing a soluble iron salt, a phosphate, and a second oxidant to carry out a second reaction, followed by washing and filtration to obtain amorphous ferric phosphate;

[0027] Optionally, the temperature of the second reaction is 5-50°C, and the pH of the second reaction is 1.5-3.0;

[0028] Optionally, the molar ratio of the soluble iron salt, the phosphate, and the second oxidant is 1:(1.0-1.4):(0.5-0.9); the soluble iron salt includes one or more of ferrous sulfate, ferrous chloride, and ferrous oxalate; the phosphate includes one or more of ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; and the second oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

[0029] This application also provides a lithium manganese iron phosphate, wherein the raw material for lithium manganese iron phosphate includes the aforementioned manganese iron phosphate.

[0030] This application also provides a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery includes the aforementioned lithium manganese iron phosphate.

[0031] This application also provides an electrical device, which includes the aforementioned lithium-ion battery.

[0032] Compared with the prior art, the beneficial effects of this application include:

[0033] This application provides a manganese iron phosphate, lithium manganese iron phosphate, and lithium-ion batteries and related electrical devices. The manganese iron phosphate provided in this application includes a secondary agglomerate, which is formed by the aggregation of multiple primary particles. Each primary particle includes at least two layered stacked nanosheet units. In the above structure, the internal arrangement of the primary particles is more compact and regular, which can reduce the space waste caused by the irregular stacking of nanosheet units. In addition, the morphology of the layered stacking of near-square nanosheet units is conducive to the intercalation of lithium during the sintering of the cathode material and to the transport of lithium ions during the electrochemical process, thereby improving the charge and discharge capacity and rate performance of lithium manganese iron phosphate. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 SEM image of the secondary agglomerates in the manganese iron phosphate prepared in Example 1;

[0036] Figure 2 TEM images of primary particles and nanosheet units in the manganese iron phosphate prepared in Example 1;

[0037] Figure 3 The XRD pattern of the manganese iron phosphate prepared in Example 1 is shown below.

[0038] Figure 4 The image shows a TEM image of the manganese iron phosphate prepared in Comparative Example 1.

[0039] Figure 5 The image shows the XRD pattern of the manganese iron phosphate prepared in Comparative Example 1. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] The following provides a detailed description of the manganese iron phosphate, lithium manganese iron phosphate, lithium-ion batteries, and electrical equipment provided in this application.

[0042] In a first aspect, embodiments of this application provide a ferromanganese phosphate, wherein the ferromanganese phosphate comprises a secondary agglomerate, the secondary agglomerate being formed by the aggregation of multiple primary particles, and the primary particles comprising at least two layered stacked nanosheet units.

[0043] This application provides a lithium manganese iron phosphate, comprising a secondary agglomerate formed by the aggregation of multiple primary particles. Each primary particle includes at least two layered stacked nanosheet units. In this structure, the internal arrangement of the primary particles is denser and more regular, reducing space waste caused by the irregular stacking of nanosheet units. Furthermore, the layered stacking morphology of the near-square nanosheet units facilitates lithium intercalation during cathode material sintering and lithium ion transport during electrochemical processes, thereby improving the charge / discharge capacity and rate performance of lithium manganese iron phosphate.

[0044] In an optional embodiment, the nanosheet unit has a near-square morphology and the average side length of the nanosheet unit is 350-450 nm.

[0045] Optionally, the average side length can be any value between 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, and 350-450nm.

[0046] In an optional embodiment, the chemical formula of the manganese iron phosphate is Mn. 1-x Fe x PO4, 0.01≤x≤0.99, the manganese iron phosphate satisfies one or more of the following conditions A to D:

[0047] A. The D50 of the manganese iron phosphate is 1-20 μm;

[0048] B. The specific surface area of ​​the aforementioned manganese ferric phosphate is 6-20 m². 2 / g;

[0049] C. The pore volume of the aforementioned manganese ferric phosphate is 0.020–0.030 cm³. 3 / g;

[0050] D. The average pore size of the ferromanganese phosphate is 12-20 nm;

[0051] E. The primary particle comprises at least three layered stacked nanosheet units, optionally, the number of layered stacked nanosheet units is 3-30.

[0052] Optionally, D50 can be any value between 1μm, 2μm, 5μm, 7μm, 9μm, 11μm, 13μm, 15μm, 17μm, 19μm, 20μm, and 1-20μm.

[0053] Optionally, the specific surface area can be 6m². 2 / g、8m 2 / g, 10m 2 / g、12m 2 / g、14m 2 / g, 16m 2 / g、18m 2 / g、20m 2 / g and 6-20m 2 Any value between / g.

[0054] Optionally, the pore volume can be 0.020 cm³. 3 / g, 0.025cm 3 / g, 0.030cm 3 / g and 0.020~0.030cm 3 Any value between / g.

[0055] Optionally, the average aperture can be any value between 12nm, 14nm, 16nm, 18nm, 20nm, and 12-20nm.

[0056] Optionally, the layered stacked nanosheet units can be any number of 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, or between 3 and 30.

[0057] The ferromanganese phosphate provided in this application includes secondary agglomerates, which are formed by the aggregation of multiple primary particles. These secondary agglomerates have a large average pore size and pore volume, forming a loose and porous structure that is easy to grind, thus improving the processing performance of ferromanganese phosphate. In the process of preparing lithium iron phosphate, ferromanganese phosphate has a large contact area with the lithium source and high reactivity. The prepared ferromanganese phosphate cathode material has good wettability with the electrolyte, which can significantly improve the electrochemical performance.

[0058] Excessive pore volume and pore size exacerbate interfacial side reactions between the electrolyte and the cathode material of manganese iron phosphate; insufficient pore volume and pore size result in poor wettability inside the cathode material of manganese iron phosphate; appropriate pore volume and pore size can better improve electrochemical performance and processing performance.

[0059] Secondly, embodiments of this application also provide a method for preparing ferromanganese phosphate, comprising: mixing amorphous ferric phosphate and manganese hydroxide to form a slurry, and reacting it with phosphoric acid to obtain hydrated ferromanganese phosphate;

[0060] The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate.

[0061] When a slurry formed by mixing amorphous ferric phosphate and manganese hydroxide reacts with phosphoric acid, the dissolution rates of the two are consistent, which can achieve homogeneous co-precipitation of Mn and Fe, generating a uniformly distributed manganese ferric phosphate precursor with a purity of over 99%.

[0062] In an optional embodiment, phosphorus includes adding a slurry formed by mixing amorphous ferric phosphate and manganese hydroxide into a phosphoric acid solution for reaction, followed by washing, filtering, and drying to obtain hydrated manganese ferric phosphate.

[0063] The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate;

[0064] Optionally, the molar ratio of the amorphous ferric phosphate to the manganese hydroxide is (1-99):(99-1), and the molar ratio of the phosphoric acid to the total molar ratio of the amorphous ferric phosphate and manganese hydroxide is 1:(0.6-1).

[0065] Optionally, the solid content of the slurry is 5%-20%, the slurry is added at a time of 0.5-1.5 hours, and the reaction temperature is 20-100°C.

[0066] Optionally, the drying temperature is 80℃-120℃, and the drying time is 2h-12h;

[0067] Optionally, the heat treatment temperature is 400℃-480℃, and the heat treatment time is 2h-8h.

[0068] Optionally, the molar ratio of amorphous ferric phosphate to manganese hydroxide can be any value between 1:99, 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, 99:1 and (1-99):(99-1), and the molar ratio of phosphoric acid to the total molar ratio of amorphous ferric phosphate and manganese hydroxide can be any value between 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 and 1:(0.6-1).

[0069] Optionally, the solid content of the slurry can be any value between 5%, 8%, 10%, 12%, 15%, 18%, 20%, and 5%-20%, the slurry addition time can be any value between 0.5h, 1.0h, 1.5h, and 0.5-1.5h, and the reaction temperature can be any value between 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, and 20-100℃.

[0070] Optionally, the drying temperature can be any value between 80℃, 90℃, 100℃, 110℃, 120℃, and 80℃-120℃, and the drying time can be any value between 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, and 2h-12h.

[0071] Optionally, the heat treatment temperature can be any value between 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃ and 400℃-480℃, and the heat treatment time can be any value between 2h, 3h, 4h, 5h, 6h, 7h, 8h and 2h-8h.

[0072] When hydrated manganese ferric phosphate is dehydrated within the above temperature range, most of the water of crystallization can be removed while maintaining the integrity of the precursor crystal structure.

[0073] In an optional embodiment, the method for preparing manganese hydroxide includes: adding soluble manganese salt, a first oxidant and ammonia water in parallel to a base liquid to carry out a first reaction, followed by aging, washing and filtration to obtain manganese hydroxide;

[0074] In an optional embodiment, the base solution is dilute ammonia water with a pH of 8-11, the temperature of the first reaction is 5-50°C, the pH of the first reaction is 8.5-10, and the pH of the aging process is 8.5-10.

[0075] Optionally, the pH of the base solution can be any value between 8, 9, 10, 11 and 8-11; the temperature of the first reaction can be any value between 5℃, 10℃, 20℃, 30℃, 40℃, 50℃ and 5-50℃; the pH of the first reaction can be any value between 8.5, 9.0, 9.5, 10 and 8.5-10; and the pH of aging can be any value between 8.5, 9.0, 9.5, 10 and 8.5-10.

[0076] In an optional embodiment, the molar ratio of the soluble manganese salt, the first oxidant, and ammonia is 1:(2.5-3.5):(0.4-1.0); the soluble manganese salt includes one or more of manganese sulfate, manganese chloride, and manganese nitrate; the first oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

[0077] Optionally, the molar ratio of the soluble manganese salt, the primary oxidant, and the pH adjuster is any value between 1:2.5:0.4, 1:2.8:0.6, 1:3.0:0.8, 1:3.5:1.0, and 1:(2.5-3.5):(0.4-1.0).

[0078] In an optional embodiment, the method for preparing amorphous iron phosphate includes: mixing a soluble iron salt, a phosphate, and a second oxidant to carry out a second reaction, followed by washing and filtration to obtain amorphous iron phosphate;

[0079] In an optional embodiment, the temperature of the second reaction is 5-50°C, and the pH of the second reaction is 1.5-3.0.

[0080] Optionally, the temperature of the second reaction can be any value between 5°C, 10°C, 20°C, 30°C, 40°C, 50°C and 5-50°C, and the pH of the second reaction can be any value between 1.5, 2.0, 2.5, 3.0 and 1.5-3.0.

[0081] In an optional embodiment, the molar ratio of the soluble iron salt, phosphate, and second oxidant is 1:(1.0-1.4):(0.5-0.9); the soluble iron salt includes one or more of ferrous sulfate, ferrous chloride, and ferrous oxalate; the phosphate includes one or more of ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; and the second oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

[0082] Optionally, the molar ratio of the soluble iron salt, phosphate, and second oxidant can be any value between 1:1.0:0.5, 1:1.1:0.6, 1:1.2:0.7, 1:1.3:0.8, 1:1.4:0.9, and 1:(1.0-1.4):(0.5-0.9).

[0083] Thirdly, embodiments of this application also provide lithium manganese iron phosphate, wherein the raw material for lithium manganese iron phosphate includes the aforementioned iron manganese phosphate.

[0084] Fourthly, embodiments of this application also provide a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery includes the lithium manganese iron phosphate.

[0085] Fifthly, this application also provides an electrical device, which includes the aforementioned lithium-ion battery.

[0086] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0087] Example 1

[0088] Preparation method of ferric manganese phosphate, the chemical formula of ferric manganese phosphate is Mn 0.65 Fe 0.35 PO4, its preparation process is as follows:

[0089] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were mixed in parallel at a stoichiometric ratio of 1:1.2:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 2.0. After the reaction was completed, the mixture was washed and filtered to obtain the amorphous ferric phosphate required for manganese ferric phosphate.

[0090] 2) Manganese sulfate, ammonia, and hydrogen peroxide were added concurrently to dilute ammonia water with a pH of 8 at a stoichiometric ratio of 1:2.5:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 8.5. After the reaction was completed, the mixture was aged (the pH during the aging stage was 8.5). After aging, the mixture was washed and filtered to obtain manganese hydroxide required for manganese ferric phosphate.

[0091] 3) Using a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the above-mentioned amorphous ferric phosphate, the above-mentioned manganese hydroxide, and 85% wt industrial phosphoric acid were used. First, manganese hydroxide and amorphous ferric phosphate were mixed to form a mixed slurry with a solid content of 20%. Then, the mixed slurry was added to the phosphoric acid solution, and the reaction was carried out at a temperature of 90℃. The feeding time of the mixed slurry was 1 hour. After washing, filtering, and drying (drying temperature was 120℃), hydrated manganese ferric phosphate was obtained.

[0092] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 430℃ for 4 hours to obtain manganese ferric phosphate powder precursor.

[0093] The morphology of the nanosheet-like manganese iron phosphate prepared above is as follows: Figure 1 , Figure 2 As shown, it can be seen that square-like nanosheets are stacked to form primary particles. XRD pattern as follows... Figure 3 As shown, XRD results indicate that ferric manganese phosphate is free of impurities and has high phase purity, exceeding 99%.

[0094] Example 2

[0095] The preparation method of ferric manganese phosphate is basically the same as that in Example 1, except that the manganese-iron ratio is different in step 3). The preparation process is as follows:

[0096] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were mixed in parallel at a stoichiometric ratio of 1:1.2:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 2.0. After the reaction was completed, the mixture was washed and filtered to obtain the amorphous ferric phosphate required for manganese ferric phosphate.

[0097] 2) Manganese sulfate, ammonia, and hydrogen peroxide were added concurrently to dilute ammonia water with a pH of 8 at a stoichiometric ratio of 1:2.5:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 8.5. After the reaction was completed, the mixture was aged (the pH during the aging stage was 8.5). After aging, the mixture was washed and filtered to obtain manganese hydroxide required for manganese ferric phosphate.

[0098] 3) According to the stoichiometric ratio of Mn:Fe = 60:40 and (Mn+Fe):P = 1:0.8, the above-mentioned amorphous ferric phosphate, the above-mentioned manganese hydroxide, and 85% wt industrial phosphoric acid were used. First, manganese hydroxide and amorphous ferric phosphate were mixed into a mixed slurry with a solid content of 20%. Then, the mixed slurry was added to the phosphoric acid solution, and the reaction was carried out at a temperature of 90℃. The feeding time of the mixed slurry was 1 hour. After washing, filtering, and drying (drying temperature was 120℃), hydrated manganese ferric phosphate was obtained.

[0099] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 430℃ for 4 hours to obtain manganese ferric phosphate powder precursor.

[0100] The morphology and stacking method of the manganese iron phosphate nanosheet unit are consistent with those of Example 1.

[0101] Example 3

[0102] The preparation method of ferric manganese phosphate is basically the same as that in Example 1, except that the manganese-iron ratio is different in step 3). The preparation process is as follows:

[0103] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were mixed in parallel at a stoichiometric ratio of 1:1.2:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 2.0. After the reaction was completed, the mixture was washed and filtered to obtain the amorphous ferric phosphate required for manganese ferric phosphate.

[0104] 2) Manganese sulfate, ammonia, and hydrogen peroxide were added concurrently to dilute ammonia water with a pH of 8 at a stoichiometric ratio of 1:2.5:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 8.5. After the reaction was completed, the mixture was aged (the pH during the aging stage was 8.5). After aging, the mixture was washed and filtered to obtain manganese hydroxide required for manganese ferric phosphate.

[0105] 3) Using the stoichiometric ratios Mn:Fe = 50:50 and (Mn+Fe):P = 1:0.8, the above-mentioned amorphous ferric phosphate, the above-mentioned manganese hydroxide, and 85% wt industrial phosphoric acid were used. First, manganese hydroxide and amorphous ferric phosphate were mixed into a mixed slurry with a solid content of 20%. Then, the mixed slurry was added to the phosphoric acid solution, and the reaction was carried out at a temperature of 90℃. The feeding time of the mixed slurry was 1 hour. After washing, filtering, and drying (drying temperature was 120℃), hydrated manganese ferric phosphate was obtained.

[0106] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 430℃ for 4 hours to obtain manganese ferric phosphate powder precursor.

[0107] The morphology and stacking method of the manganese iron phosphate nanosheet unit are consistent with those of Example 1.

[0108] Comparative Example 1

[0109] The preparation method of manganese iron phosphate is basically the same as that in Example 1, except that a different pH adjuster is used in step 2). The preparation process is as follows:

[0110] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were mixed in parallel at a stoichiometric ratio of 1:1.2:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 2.0. After the reaction was completed, the mixture was washed and filtered to obtain the amorphous ferric phosphate required for manganese ferric phosphate.

[0111] 2) Manganese sulfate, sodium hydroxide and hydrogen peroxide were added in parallel to dilute ammonia water with pH 8 at a stoichiometric ratio of 1:2.5:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 8.5. After the reaction was completed, the mixture was aged (pH 8.5 during the aging stage). After aging, the mixture was washed and filtered to obtain manganese tetroxide.

[0112] 3) Using the stoichiometric ratios Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the above-mentioned amorphous ferric phosphate, the above-mentioned manganese tetroxide, and 85% wt industrial phosphoric acid were first mixed to form a mixed slurry with a solid content of 20%. Then, the mixed slurry was added to the phosphoric acid solution, and the reaction was carried out at a temperature of 90℃. The feeding time of the mixed slurry was 1 hour. After washing, filtering, and drying, hydrated manganese ferric phosphate was obtained, with the drying temperature being 120℃.

[0113] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 430℃ for 4 hours to obtain manganese ferric phosphate powder precursor.

[0114] The morphology of the manganese iron phosphate prepared above is as follows: Figure 4 As shown in the TEM image, the nanosheet units have an ellipsoidal morphology and exhibit disordered aggregation. The XRD pattern is as follows: Figure 5 As shown in the XRD pattern, the prepared product is manganese iron phosphate.

[0115] Comparative Example 2

[0116] The preparation method of manganese ferric phosphate is basically the same as that in Example 1, except that different pH adjusters are used in step 2) and different manganese-iron ratios are used in step (3). The specific preparation process is as follows:

[0117] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were mixed in parallel at a stoichiometric ratio of 1:1.2:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 2.0. After the reaction was completed, the mixture was washed and filtered to obtain the amorphous ferric phosphate required for manganese ferric phosphate.

[0118] 2) Manganese sulfate, sodium hydroxide and hydrogen peroxide were added in parallel to dilute ammonia water with pH 8 at a stoichiometric ratio of 1:2.5:0.7 to carry out a precipitation reaction. The reaction temperature was controlled at 30℃ and the pH was 8.5. After the reaction was completed, the mixture was aged (pH 8.5 during the aging stage). After aging, the mixture was washed and filtered to obtain manganese tetroxide.

[0119] 3) Using the stoichiometric ratios Mn:Fe = 60:40 and (Mn+Fe):P = 1:0.8, the above-mentioned amorphous ferric phosphate, the above-mentioned manganese tetroxide, and 85% wt industrial phosphoric acid were first mixed to form a mixed slurry with a solid content of 20%. Then, the mixed slurry was added to the phosphoric acid solution, and the reaction was carried out at a temperature of 90℃. The feeding time of the mixed slurry was 1 hour. After washing, filtering, and drying, hydrated manganese ferric phosphate was obtained, with the drying temperature being 120℃.

[0120] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 430℃ for 4 hours to obtain manganese ferric phosphate powder precursor.

[0121] The morphology and stacking pattern of the nanosheet units in the manganese iron phosphate powder are consistent with those in Comparative Example 1.

[0122] Preparation method of lithium manganese iron phosphate:

[0123] Lithium manganese iron phosphate was prepared from the iron manganese phosphate in the examples and comparative examples, and the specific operations are as follows:

[0124] 1) Mix lithium carbonate, ferromanganese phosphate, and other ingredients such as titanium dioxide, magnesium oxide, lithium carbonate, glucose, and PEG in a Li / (Mn+Fe) molar ratio of 1.04, and add deionized water to prepare a slurry with a solid content of 28%.

[0125] 2) After mixing and stirring for 30 minutes, grind the slurry in a sand mill, and control the grinding D50 at 0.24~0.25μm.

[0126] 3) The slurry with qualified particle size after grinding is then introduced into a spray dryer by a peristaltic pump for drying and molding.

[0127] 4) Transfer the dried powder to a box furnace and sinter it under a nitrogen atmosphere. Control the heating rate to 2℃ / min, hold at 480℃ for 2h, hold at 680℃ for 8h, and then let it cool naturally to room temperature to obtain carbon-coated lithium manganese iron phosphate (LMFP / C).

[0128] Electrochemical performance testing methods:

[0129] The aforementioned LMFP / C cathode materials were combined with conductive carbon nanotubes, conductive carbon black, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (N-Methylpyrrolidone) solvent to form a cathode slurry. The mass ratio of LMFP / C cathode material to conductive carbon nanotubes, conductive carbon black, and PVDF binder was 91.5:1.5:1.0:6.0. The cathode slurry was coated onto aluminum foil, followed by vacuum baking, stamping, and finally fabrication of LMFP / C cathode sheets. Using LMFP / C as the cathode, lithium foil as the anode, and a 1 mol / L LiPF6 EC / DMC / EMC solution as the electrolyte, a button cell was assembled. Charge-discharge tests were performed on the battery (charge-discharge window 2.5V–4.3V) to determine the electrical performance of lithium manganese iron phosphate.

[0130] The length and width of the grains were measured in the TEM image, and the pore volume, pore size, and BET were measured by nitrogen adsorption.

[0131] The test results of the examples and comparative examples are shown in Tables 1 and 2:

[0132] Table 1 shows the BET, pore volume, average pore size, and average particle size after grinding in the examples.

[0133]

[0134] Table 2 Electrochemical Performance

[0135]

[0136] Combining the data in Tables 1 and 2, and Figure 1-5 It can be seen that: in the examples, ammonia water was selected to react with a soluble manganese source and an oxidant to prepare manganese hydroxide; in the comparative example, sodium hydroxide was selected to react with a soluble manganese source and an oxidant to prepare manganese tetroxide. Manganese hydroxide and manganese tetroxide were then reacted with amorphous iron phosphate to prepare iron manganese phosphate with different morphologies. The primary particles of iron manganese phosphate in Examples 1-3 were all composed of stacked, near-square nanosheet units. This stacked, near-square nanosheet morphology facilitates lithium-ion insertion / extraction, improves lithium-ion transport efficiency, and thus enhances the charge / discharge capacity and rate performance of lithium iron phosphate. Furthermore, this iron manganese phosphate also has high BET, pore volume, and average pore size, making it easy to grind and improving its processing performance. During the preparation of the cathode material, the precursor has a large contact area with the lithium and carbon sources, resulting in high reactivity. After preparation, the cathode material exhibits good electrolyte wettability, improving electrochemical performance.

[0137] In Comparative Examples 1-2, the nanosheet units have an ellipsoidal morphology and are in a disordered aggregated state. This morphology is not conducive to lithium ion insertion / extraction, resulting in lower discharge capacity and worse rate performance.

[0138] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A type of manganese iron phosphate, characterized in that, The manganese iron phosphate includes a secondary agglomerate, which is formed by the aggregation of multiple primary particles. Each primary particle includes at least two layered stacked nanosheet units, and the nanosheet units have a square-like morphology.

2. The manganese iron phosphate according to claim 1, characterized in that, The average side length of the nanosheet unit is 350-450 nm.

3. The manganese iron phosphate according to claim 1, characterized in that, The chemical formula of the manganese iron phosphate is Mn. 1- x Fe x PO4, 0.01≤x≤0.99, the manganese iron phosphate satisfies one or more of the following conditions A to E: A. The D50 of the manganese iron phosphate is 1-20 μm; B. The specific surface area of ​​the manganese ferric phosphate is 6-20 m². 2 / g; C. The pore volume of the aforementioned manganese ferric phosphate is 0.020~0.030 cm³. 3 / g; D. The average pore size of the ferromanganese phosphate is 12-20 nm; E. The primary particle comprises at least three layered, stacked nanosheet units.

4. The manganese iron phosphate according to claim 3, characterized in that, The number of layered, stacked nanosheet units ranges from 3 to 30.

5. A method for preparing ferric manganese phosphate, characterized in that, include: A slurry formed by mixing amorphous ferric phosphate and manganese hydroxide is reacted with phosphoric acid to obtain hydrated manganese ferric phosphate. The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate.

6. The preparation method according to claim 5, characterized in that, This includes adding a slurry formed by mixing amorphous ferric phosphate and manganese hydroxide into a phosphoric acid solution for reaction, followed by washing, filtration, and drying to obtain hydrated manganese ferric phosphate; The hydrated manganese ferric phosphate was subjected to heat treatment to obtain manganese ferric phosphate.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the amorphous ferric phosphate to the manganese hydroxide is (1-99):(99-1), and the molar ratio of the phosphoric acid to the total molar ratio of the amorphous ferric phosphate and manganese hydroxide is 1:(0.6-1).

8. The preparation method according to claim 6, characterized in that, The slurry has a solid content of 5%-20%, the slurry is added at a time of 0.5-1.5 hours, and the reaction temperature is 20-100℃.

9. The preparation method according to claim 6, characterized in that, The drying temperature is 80℃-120℃, and the drying time is 2h-12h.

10. The preparation method according to claim 6, characterized in that, The heat treatment temperature is 400℃-480℃, and the heat treatment time is 2h-8h.

11. The preparation method according to any one of claims 5-6, characterized in that, The method for preparing manganese hydroxide includes: adding soluble manganese salt, a first oxidant and ammonia water in parallel to a base liquid to carry out a first reaction, followed by aging, washing and filtration to obtain manganese hydroxide, wherein: the base liquid is dilute ammonia water with a pH of 8-11.

12. The preparation method according to claim 11, characterized in that, The temperature of the first reaction is 5-50℃, the pH of the first reaction is 8.5-10, and the pH of the aging process is 8.5-10.

13. The preparation method according to claim 11, characterized in that, The molar ratio of the soluble manganese salt, the first oxidant, and ammonia is 1:(2.5-3.5):(0.4-1.0); the soluble manganese salt includes one or more of manganese sulfate, manganese chloride, and manganese nitrate; the first oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

14. The preparation method according to any one of claims 5-6, characterized in that, The method for preparing amorphous ferric phosphate includes: mixing soluble iron salt, phosphate, and a second oxidant to carry out a second reaction, followed by washing and filtration to obtain amorphous ferric phosphate.

15. The preparation method according to claim 14, characterized in that, The temperature of the second reaction is 5-50℃, and the pH of the second reaction is 1.5-3.

0.

16. The preparation method according to claim 14, characterized in that, The molar ratio of the soluble iron salt, the phosphate, and the second oxidant is 1:(1.0-1.4):(0.5-0.9); the soluble iron salt includes one or more of ferrous sulfate, ferrous chloride, and ferrous oxalate; the phosphate includes one or more of ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; the second oxidant includes one or more of hydrogen peroxide, ozone, sodium peroxide, ammonium persulfate, and ammonium percarbonate.

17. A lithium manganese iron phosphate, characterized in that, The raw materials for the lithium manganese iron phosphate include the ferromanganese phosphate described in any one of claims 1-4 or the ferromanganese phosphate prepared by any one of claims 5-16.

18. A lithium-ion battery, characterized in that, The cathode material of the lithium-ion battery includes lithium manganese iron phosphate as described in claim 17.

19. An electrical-related device, characterized in that, Including the lithium-ion battery as described in claim 18.

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