Manganese iron phosphate and preparation method therefor, lithium manganese iron phosphate, lithium ion battery, and electric device

Abstract

Disclosed in the present disclosure are manganese iron phosphate and a preparation method therefor, lithium manganese iron phosphate, a lithium ion battery, and an electric device. Provided in the present disclosure is manganese iron phosphate. The manganese iron phosphate has an average crystallite size of 28.0 nm-40.0 nm. When the average crystallite size of the manganese iron phosphate is within the described range, it can be ensured that the manganese iron phosphate fully contacts and reacts with a carbon source and a lithium source, and it can also be ensured that the manganese iron phosphate maintains a complete structure during sintering, so that the lithium manganese iron phosphate also has a complete crystal structure, thereby improving the charge-discharge capacity and rate capability of the lithium manganese iron phosphate.

Description

A method for preparing manganese iron phosphate, lithium manganese iron phosphate, lithium-ion batteries, and related electrical equipment.

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202410857839.0, filed on June 28, 2024, entitled “A Manganese Iron Phosphate and its Preparation Method, Lithium Manganese Iron Phosphate, Lithium-ion Battery and Electrical Equipment”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium-ion battery materials technology, and more specifically, to a manganese iron phosphate and its preparation method, lithium manganese iron phosphate, lithium-ion batteries, and electrical equipment. Background Technology

[0004] 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, crystallinity, and grain size of manganese iron phosphate all have a certain influence on the performance of LFP.

[0005] Currently, few people pay attention to the grain size of ferromanganese phosphate, and most technologies synthesize ferromanganese phosphate with grain sizes larger than 100 nm. When ferromanganese phosphate with grain sizes within this range is used to prepare cathode materials, the rate performance of the cathode materials is poor. Summary of the Invention

[0006] The purpose of this disclosure is to provide a method for preparing ferromanganese phosphate, lithium manganese iron phosphate, lithium-ion batteries, and electrical equipment to solve the above-mentioned problems.

[0007] The technical problem solved by this disclosure is achieved by the following technical solution.

[0008] This disclosure provides a ferromanganese phosphate with an average grain size of 28.0 nm to 40.0 nm on the (111), (110), (-111), (021), (-202), and (022) crystal planes.

[0009] In some embodiments of this disclosure, ferromanganese phosphate satisfies one or more of the following conditions:

[0010] (1)(111) The grain size of the crystal plane is 30.0 nm-40.0 nm;

[0011] (2) The grain size of the (110) crystal plane is 40.0 nm-50.0 nm;

[0012] (3) The grain size of the (-111) crystal plane is 40.0 nm-50.0 nm;

[0013] (4)(021) The grain size of the crystal plane is 30.0 nm-40.0 nm;

[0014] (5) The grain size of the (-202) crystal plane is 25.0 nm-40.0 nm;

[0015] (6)(022) The grain size of the crystal plane is 20.0nm-30.0nm.

[0016] In some embodiments of this disclosure, ferromanganese phosphate satisfies one or more of the following conditions A to D:

[0017] A. The D50 of manganese iron phosphate is 1μm-20μm;

[0018] B. The specific surface area of ​​manganese iron phosphate is 6 m². 2 / g-20m 2 / g;

[0019] C. The pore volume of manganese iron phosphate is 0.020 cm³. 3 / g-0.030cm 3 / g;

[0020] D. The average pore size of manganese iron phosphate is 12.0 nm-20.0 nm.

[0021] In some embodiments of this disclosure, the general chemical formula of manganese iron phosphate is Mn. 1-x Fe x PO4, 0.01≤x≤0.99.

[0022] This disclosure also provides a method for preparing the above-mentioned ferromanganese phosphate, which includes: mixing an iron source and a manganese source to form a slurry, mixing it with phosphoric acid to react and obtain hydrated ferromanganese phosphate; and then heat-treating the hydrated ferromanganese phosphate to obtain ferromanganese phosphate.

[0023] In some embodiments of this disclosure, the preparation of hydrated manganese ferric phosphate includes: mixing an iron source and a manganese source to obtain a slurry with a solid content of 5%-20%, then adding the slurry to phosphoric acid, maintaining the temperature at 20℃-100℃ for reaction, controlling the slurry feeding time to be 0.5h-1.5h, and after the reaction is completed, washing, filtering and drying are performed to obtain hydrated manganese ferric phosphate.

[0024] In some embodiments of this disclosure, the molar ratio of iron source to manganese source is (1-99):(99-1); the molar ratio of phosphoric acid to the total molar ratio of iron source and manganese source is 1:(0.6-1).

[0025] In some embodiments of this disclosure, the iron source includes one or more of amorphous iron phosphate, amorphous ammonium iron phosphate, and amorphous hydroxy iron phosphate, and the manganese source includes one or more of manganese hydroxide, manganese tetroxide, manganese dioxide, hydrated manganese dioxide, manganese hydroxide, and manganese trioxide.

[0026] In some embodiments of this disclosure, the drying temperature is 80°C-120°C and the drying time is 2h-12h.

[0027] This disclosure also provides a lithium manganese iron phosphate, which is obtained by heat-treating hydrated manganese iron phosphate at 400℃-480℃ for 2h-8h.

[0028] This disclosure also provides a lithium manganese iron phosphate, wherein the raw materials for lithium manganese iron phosphate include the above-mentioned ferromanganese phosphate and ferromanganese phosphate prepared by the above-mentioned preparation method.

[0029] This disclosure also provides a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery includes the aforementioned lithium manganese iron phosphate.

[0030] This disclosure also provides an electrical device including the aforementioned lithium-ion battery.

[0031] Compared with the prior art, the beneficial effects of this disclosure include:

[0032] This disclosure provides a method for preparing ferromanganese phosphate, lithium iron phosphate, a lithium-ion battery, and related electrical equipment. The ferromanganese phosphate provided in this disclosure has a small average grain size. When the average grain size of ferromanganese phosphate is in the range of 28.0 nm to 40.0 nm, the prepared lithium iron phosphate exhibits excellent capacity, rate performance, and cycle performance. This is because: if the grain size of ferromanganese phosphate is too large, it is not conducive to the full reaction between ferromanganese phosphate and the lithium source, thus leading to a decrease in the capacity and rate performance of the prepared cathode material. If the grain size of ferromanganese phosphate is too small, it may affect the crystallinity of ferromanganese phosphate, thereby affecting the crystallinity of lithium iron phosphate. In addition, it may also cause the crystal structure to collapse during the sintering of ferromanganese phosphate and the lithium source, thus affecting the battery's capacity, rate performance, and cycle performance. Therefore, there is a suitable range for the grain size of ferromanganese phosphate. Within this range, the grain size can ensure both sufficient reaction with carbon and lithium sources and high crystallinity and a complete crystal structure, thereby improving the charge / discharge capacity and rate performance of lithium iron phosphate. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure 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.

[0034] Figure 1 is the XRD pattern of the manganese iron phosphate prepared in Example 1;

[0035] Figure 2 shows the XRD pattern of the manganese iron phosphate prepared in Comparative Example 1;

[0036] Figure 3 shows the XRD pattern of the manganese iron phosphate prepared in Comparative Example 2;

[0037] Figure 4 shows the XRD pattern of the manganese iron phosphate prepared in Comparative Example 3.

[0038] Figure 5 shows the XRD pattern of the manganese iron phosphate prepared in Comparative Example 4. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions in this disclosure 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.

[0040] The following provides a detailed description of the ferromanganese phosphate, its preparation method, lithium manganese iron phosphate, lithium-ion batteries, and related electrical equipment disclosed herein.

[0041] In a first aspect, this disclosure provides a ferromanganese phosphate having an average grain size of 28.0 nm to 40.0 nm on the (111) crystal plane, (110) crystal plane, (-111) crystal plane, (021) crystal plane, (-202) crystal plane and (022) crystal plane.

[0042] The ferromanganese phosphate disclosed herein has an average grain size of 28.0 nm to 40.0 nm. Optionally, the average grain size of ferromanganese phosphate can be 28.0 nm, 29.0 nm, 30.0 nm, 31.0 nm, 32.0 nm, 33.0 nm, 34.0 nm, 35.0 nm, 36.0 nm, 37.0 nm, 38.0 nm, 39.0 nm, 40.0 nm, or any other value between 28.0 nm and 40.0 nm.

[0043] The aforementioned grain size characteristics of ferromanganese phosphate (FMP) are beneficial for improving the charge / discharge capacity and rate performance of lithium iron phosphate (LFP). This is because: if the grain size of FMP is too large, it is not conducive to the full reaction between FMP and the lithium source, thus leading to a decrease in the capacity and rate performance of the prepared cathode material. If the grain size of FMP is too small, it may affect the crystallinity of FMP, and consequently the crystallinity of LFP. In addition, it may also cause the crystal structure to collapse during the sintering of FMP and the lithium source, thereby affecting the battery's capacity, rate performance, and cycle performance. Therefore, there is a suitable range for the grain size of FMP. Within this range, the grain size can ensure a full reaction with the carbon and lithium sources while maintaining high crystallinity and a complete crystal structure, thereby improving the charge / discharge capacity and rate performance of LFP.

[0044] In some optional embodiments, the ferromanganese phosphate satisfies one or more of the following conditions:

[0045] (1)(111) The grain size of the crystal plane is 30.0 nm-40.0 nm;

[0046] (2) The grain size of the (110) crystal plane is 40.0 nm-50.0 nm;

[0047] (3) The grain size of the (-111) crystal plane is 40.0 nm-50.0 nm;

[0048] (4)(021) The grain size of the crystal plane is 30.0 nm-40.0 nm;

[0049] (5) The grain size of the (-202) crystal plane is 25.0 nm-40.0 nm;

[0050] (6)(022) The grain size of the crystal plane is 20.0nm-30.0nm.

[0051] Optionally, (111) the grain size of the crystal plane can be 30.0 nm, 32.0 nm, 34.0 nm, 35.0 nm, 36.0 nm, 38.0 nm, 40.0 nm, or any other value between 30.0 nm and 40.0 nm; (110) the grain size of the crystal plane can be 40.0 nm, 42.0 nm, 44.0 nm, 45.0 nm, 46.0 nm, 48.0 nm, 50.0 nm, or any other value between 40.0 nm and 50.0 nm; (-111) the grain size of the crystal plane can be 40.0 nm, 42.0 nm, 44.0 nm, 45.0 nm, 46.0 nm, 48.0 nm, 50.0 nm, or any other value between 40.0 nm and 50.0 nm; (021) The grain size of the crystal plane can be 30.0 nm, 32.0 nm, 34.0 nm, 35.0 nm, 36.0 nm, 38.0 nm, 40.0 nm and any other value between 30.0 nm and 40.0 nm; (-202) The grain size of the crystal plane can be 25.0 nm, 27.0 nm, 30.0 nm, 32.0 nm, 34.0 nm, 35.0 nm, 36.0 nm, 38.0 nm, 40.0 nm and any other value between 25.0 nm and 40.0 nm; (022) The grain size of the crystal plane can be 20.0 nm, 22.0 nm, 24.0 nm, 25.0 nm, 26.0 nm, 28.0 nm, 30.0 nm and any other value between 20.0 nm and 30.0 nm.

[0052] All six diffraction peaks have very high intensities. Based on the intensity of the diffraction peaks, they can be divided into dominant peaks and secondary peaks. The diffraction peak corresponding to the (111) crystal plane is the dominant peak, and the diffraction peaks corresponding to the other crystal planes are secondary peaks. Because these diffraction peaks have high intensities, the grain size of the corresponding crystal planes plays a decisive role in the average grain size of manganese iron phosphate. Therefore, the average grain size of the crystal planes corresponding to these six diffraction peaks is used to represent the average grain size of manganese iron phosphate. If the grain size of the crystal planes corresponding to the six diffraction peaks is small, the average grain size is small; if the grain size of the crystal planes corresponding to the six diffraction peaks is large, the average grain size is large.

[0053] In some optional embodiments, in the X-ray diffraction spectrum of manganese iron phosphate powder, the first diffraction peak corresponding to the (111) crystal plane has a diffraction angle of 2θ = 25.5 ± 0.3°, and the full width at half maximum (FWHM) of the first diffraction peak is 0.3°-0.4°; the full width at half maximum (FWHM) of the first diffraction peak is 0.2°-0.3°; optionally, the full width at half maximum (FWHM) of the first diffraction peak is 0.21°-0.28°; optionally, the full width at half maximum (FWHM) of the first diffraction peak is 0.219°-0.247°.

[0054] And / or, (110) the crystal face corresponds to the second diffraction peak with a diffraction angle of 2θ = 18.3 ± 0.3°, and the full width at half maximum (FWHM) of the second diffraction peak is 0.1°-0.3°; optionally, the full width at half maximum (FWHM) of the second diffraction peak is 0.1°-0.25°; optionally, the full width at half maximum (FWHM) of the second diffraction peak is 0.172°-0.179°.

[0055] And / or, the (-111) crystal plane corresponds to the third diffraction peak with a diffraction angle of 2θ = 19 ± 0.3°, and the full width at half maximum (FWHM) of the third diffraction peak is 0.1°-0.3°; optionally, the full width at half maximum (FWHM) of the third diffraction peak is 0.1°-0.25°; optionally, the full width at half maximum (FWHM) of the third diffraction peak is 0.174°-0.191°.

[0056] And / or, (021) the crystal face corresponds to the fourth diffraction peak with a diffraction angle of 2θ = 27 ± 0.3°, the full width at half maximum (FWHM) of the fourth diffraction peak is 0.3°-0.4°; the full width at half maximum (FWHM) of the fourth diffraction peak is 0.2°-0.3°; optionally, the full width at half maximum (FWHM) of the fourth diffraction peak is 0.23°-0.29°; optionally, the full width at half maximum (FWHM) of the fourth diffraction peak is 0.259°-0.265°.

[0057] And / or, the (-202) crystal plane corresponds to the fifth diffraction peak with a diffraction angle of 2θ = 30 ± 0.3°, and the full width at half maximum (FWHM) of the fifth diffraction peak is 0.2°-0.4°; optionally, the full width at half maximum (FWHM) of the fifth diffraction peak is 0.2°-0.3°; optionally, the full width at half maximum (FWHM) of the fifth diffraction peak is 0.232°-0.289°.

[0058] And / or, (022) the crystal plane corresponds to the sixth diffraction peak with a diffraction angle of 2θ = 35.5 ± 0.3°, and the full width at half maximum (FWHM) of the sixth diffraction peak is 0.3°-0.5°; optionally, the full width at half maximum (FWHM) of the sixth diffraction peak is 0.3°-0.45°; optionally, the full width at half maximum (FWHM) of the sixth diffraction peak is 0.35°-0.386°.

[0059] Optionally, the full width at half maximum (FWHM) of the first diffraction peak can be any other value between 0.3°, 0.35°, 0.4°, and 0.3°-0.4°; alternatively, the full width at half maximum (FWHM) of the first diffraction peak can be any other value between 0.2°, 0.21°, 0.22°, 0.24°, 0.25°, 0.26°, 0.28°, 0.3°, and 0.2°-0.3°; the full width at half maximum (FWHM) of the second diffraction peak can be any other value between 0.1°, 0.15°, 0.2°, 0.25°, 0.3°, and 0.1°-0.3°; and the full width at half maximum (FWHM) of the third diffraction peak can be between 0.1°, 0.15°, 0.2°, 0.25°, 0.3°, and 0.1°-0.3°. The full width at half maximum (FWHM) of the fourth diffraction peak can be any other value between 0.3°, 0.35°, 0.4° and 0.3°-0.4°; the full width at half maximum (FWHM) of the fourth diffraction peak can be any other value between 0.2°, 0.23°, 0.24°, 0.26°, 0.27°, 0.28°, 0.3° and 0.2°-0.3°; the full width at half maximum (FWHM) of the fifth diffraction peak can be any other value between 0.2°, 0.25°, 0.3°, 0.35°, 0.4° and 0.2°-0.4°; the full width at half maximum (FWHM) of the sixth diffraction peak can be any other value between 0.3°, 0.35°, 0.4°, 0.45°, 0.5° and 0.3°-0.5°.

[0060] In the X-ray diffraction spectrum of manganese iron phosphate powder, when the full width at half maximum (FWHM) of each diffraction peak is within the above range, the average grain size of manganese iron phosphate is smaller, which is beneficial for improving magnification and capacity.

[0061] This disclosure, through extensive experimental research, has discovered that by controlling the composition of the aforementioned ferromanganese phosphate, the X-ray diffraction pattern of ferromanganese phosphate can exhibit specific characteristic peaks, full width at half maximum (FWHM), and grain size of each crystal plane. This results in ferromanganese phosphate possessing high structural stability, small grain size, and high crystallinity. After preparing lithium iron manganese phosphate from the aforementioned ferromanganese phosphate, lithium iron manganese phosphate can inherit the structural characteristics of ferromanganese phosphate, thereby improving the charge / discharge capacity and rate performance of lithium iron manganese phosphate.

[0062] In some alternative embodiments, ferromanganese phosphate satisfies one or more of the following conditions A to D:

[0063] A. The D50 of manganese iron phosphate is 1μm-20μm;

[0064] B. The specific surface area of ​​manganese iron phosphate is 6 m². 2 / g-20m 2 / g;

[0065] C. The pore volume of manganese iron phosphate is 0.020 cm³.3 / g-0.030cm 3 / g;

[0066] D. The average pore size of manganese iron phosphate is 12.0 nm-20.0 nm.

[0067] Optionally, the D50 of ferromanganese phosphate can be any other value between 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, and 1 μm-20 μm; the specific surface area of ​​ferromanganese phosphate can be 6 m². 2 / g、8m 2 / g, 10m 2 / g、12m 2 / g、14m 2 / g, 16m 2 / g、18m 2 / g、20m 2 / g and 6m 2 / g-20m 2 Any other value between / g; the pore volume of manganese ferric phosphate can be 0.020 cm³. 3 / g, 0.022cm 3 / g, 0.024cm 3 / g, 0.026cm 3 / g, 0.028cm 3 / g, 0.030cm 3 / g and 0.020cm 3 / g~0.030cm 3 The average pore size of manganese iron phosphate can be any other value between / g; the average pore size of manganese iron phosphate can be 12.0nm, 14.0nm, 16.0nm, 18.0nm, 20.0nm and any other value between 12.0nm and 20.0nm.

[0068] In some alternative embodiments, the general chemical formula for ferric manganese phosphate is Mn. 1-x Fe x PO4, 0.01 ≤ x ≤ 0.99. Optionally, x can be 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, and any other value between 0.01 and 0.99.

[0069] Secondly, this disclosure also provides a method for preparing ferromanganese phosphate, which includes: mixing an iron source and a manganese source to form a slurry, mixing it with phosphoric acid to react and obtain hydrated ferromanganese phosphate; and then heat-treating the hydrated ferromanganese phosphate to obtain ferromanganese phosphate.

[0070] In some optional embodiments, the preparation of hydrated manganese ferric phosphate includes: mixing an iron source and a manganese source to obtain a slurry with a solid content of 5%-20%, then adding the slurry to phosphoric acid, maintaining the temperature at 20℃-100℃ for reaction, controlling the slurry feeding time to be 0.5h-1.5h, and after the reaction is completed, washing, filtering and drying are performed to obtain hydrated manganese ferric phosphate.

[0071] Optionally, the solid content of the slurry is 5%, 8%, 10%, 12%, 15%, 18%, 20%, and any other value between 5% and 20%.

[0072] Optionally, the slurry feeding time can be 0.5h, 0.8h, 1.0h, 1.2h, 1.5h, or any other value between 0.5h and 1.5h.

[0073] Optionally, the reaction temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any other value between 20°C and 100°C.

[0074] In some alternative embodiments, the molar ratio of iron source to manganese source is (1-99):(99-1); the molar ratio of phosphoric acid to the total molar ratio of iron source and manganese source is 1:(0.6-1).

[0075] Optionally, the molar ratio of the iron source to the manganese source can be any other 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).

[0076] Optionally, the ratio of the amount of phosphoric acid to the total amount of iron and manganese sources can be any other value between 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, and 1:(0.6-1).

[0077] In some alternative embodiments, the iron source includes one or more of amorphous iron phosphate, amorphous ammonium iron phosphate, and amorphous hydroxy iron phosphate, and the manganese source includes one or more of manganese hydroxide, manganese tetroxide, manganese dioxide, hydrated manganese dioxide, manganese hydroxide, and manganese trioxide.

[0078] The above-disclosed method for preparing ferromanganese phosphate involves adding a slurry formed by mixing an iron source and a manganese source to phosphoric acid for reaction. The iron source and the manganese source have the same dissolution rate, which can achieve homogeneous co-precipitation of Mn and Fe, generating ferromanganese phosphate with uniform elemental distribution and a purity of over 99%.

[0079] When the reaction parameters are within the above range, it can be guaranteed that manganese iron phosphate with uniform elemental distribution, high purity, small grain size, and complete crystal structure can be prepared.

[0080] In some alternative embodiments, the drying temperature is 80°C-120°C and the drying time is 2h-12h.

[0081] Optionally, the drying temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, or any other value between 80℃ and 120℃, and the drying time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any other value between 2h and 12h.

[0082] In some alternative embodiments, hydrated manganese ferric phosphate is heat-treated at 400℃-480℃ for 2h-8h to obtain manganese ferric phosphate.

[0083] Optionally, the heat treatment temperature can be any other value between 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, and 400℃-480℃, and the heat treatment time can be any other value between 2h, 3h, 4h, 5h, 6h, 7h, 8h, and 2h-8h.

[0084] 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 crystal structure.

[0085] The amount of water of crystallization of manganese iron phosphate obtained after heat treatment is n, where n≤1.

[0086] Thirdly, this disclosure also provides a lithium manganese iron phosphate, wherein the raw material for the lithium manganese iron phosphate includes the above-mentioned ferromanganese phosphate or ferromanganese phosphate prepared by the above-mentioned preparation method.

[0087] Fourthly, this disclosure also provides a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery includes the aforementioned lithium manganese iron phosphate.

[0088] Fifthly, this disclosure also provides an electrical device, including the aforementioned lithium-ion battery.

[0089] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0090] Example 1

[0091] A nanoporous manganese iron phosphate with the chemical formula Mn 0.65 Fe 0.35 PO4, its preparation process is as follows:

[0092] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0093] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0094] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the manganese source and iron source are first mixed to form a slurry with a solid content of 20%. Then, the slurry is added to the 85% wt phosphoric acid, and the reaction is carried out at a temperature of 90℃. The feeding time of the slurry is controlled to be 1 hour. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, wherein the drying temperature is 120℃.

[0095] (4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder. The D50 of the ferromanganese phosphate powder was measured to be 5.98 μm, and the tap density TD was 1.37 g / cm³. 3 The specific surface area (BET) is 13.68 m². 2 / g.

[0096] Example 2:

[0097] A nanoporous manganese iron phosphate with the chemical formula Mn 0.6 Fe 0.4 PO4, its preparation process is as follows:

[0098] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous iron phosphate was obtained as the iron source required for the preparation of manganese iron phosphate precursor.

[0099] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. After washing and filtration, manganese hydroxide was obtained as the manganese source required for the preparation of manganese iron phosphate precursor.

[0100] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 60:40 and (Mn+Fe):P = 1:0.8, the manganese source and iron source were first mixed to form a slurry with a solid content of 20%. Then, the slurry was added to 85% wt phosphoric acid, and the temperature was maintained at 90℃ for precipitation reaction. The feeding time of the slurry was controlled to be 1 hour. After washing, filtering, and drying, hydrated manganese ferric phosphate was obtained, with the drying temperature being 120℃.

[0101] 4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder precursor. The D50 of the ferromanganese phosphate powder was measured to be 6.12 μm, and the tap density TD was 1.41 g / cm³. 3 The specific surface area (BET) is 12.34 m². 2 / g.

[0102] Example 3

[0103] A nanoporous manganese iron phosphate with the chemical formula Mn 0.65 Fe 0.35 PO4, its preparation process is as follows:

[0104] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0105] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0106] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.9, the manganese source and iron source are mixed to form a slurry with a solid content of 20%. Then, the slurry is added to the 85% wt phosphoric acid, and the reaction is carried out at a temperature of 90℃. The feeding time of the slurry is controlled to be 1 hour. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, wherein the drying temperature is 120℃.

[0107] (4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder. The D50 of the ferromanganese phosphate powder was measured to be 6.69 μm, and the tap density TD was 1.52 g / cm³. 3 The specific surface area (BET) is 9.84 m². 2 / g.

[0108] Example 4

[0109] A nanoporous manganese iron phosphate with the chemical formula Mn 0.65 Fe 0.35 PO4, its preparation process is as follows:

[0110] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0111] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0112] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.75, the manganese source and iron source were first mixed to form a slurry with a solid content of 20%. Then, the slurry was added to the 85% wt phosphoric acid, and the reaction was carried out at a temperature of 90℃. The feeding time of the slurry was controlled to be 1 hour. After the reaction was completed, the resulting material was washed, filtered, and dried to obtain hydrated manganese ferric phosphate, with the drying temperature being 120℃.

[0113] (4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder. The D50 of the ferromanganese phosphate powder was measured to be 5.59 μm, and the tap density TD was 1.23 g / cm³. 3 The specific surface area (BET) is 16.23 m². 2 / g.

[0114] Comparative Example 1

[0115] A nanoporous manganese iron phosphate with the chemical formula Mn 0.65 Fe 0.35 The only difference between PO4 and Example 1 is the feeding time in step 3). Its preparation process is as follows:

[0116] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0117] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0118] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.9, the manganese source and iron source are mixed to form a slurry with a solid content of 20%. Then, the slurry is added to the 85% wt phosphoric acid, and the reaction is carried out at a temperature of 90℃. The feeding time of the slurry is controlled to be 2 hours. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, wherein the drying temperature is 120℃.

[0119] 4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder. The D50 of the ferromanganese phosphate powder was measured to be 7.19 μm, and the tap density TD was 1.61 g / cm³. 3 The specific surface area (BET) is 8.3 m². 2 / g.

[0120] Comparative Example 2

[0121] A nanoporous manganese iron phosphate with the chemical formula Mn 0.65 Fe 0.35 The only difference between PO4 and Example 1 is the feeding time in step 3). Its preparation process is as follows:

[0122] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0123] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0124] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the manganese source and iron source are mixed to form a slurry with a solid content of 20%. Then, the slurry and phosphoric acid are simultaneously poured into water, heated, and maintained at 90°C for reaction. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, with the drying temperature being 120°C.

[0125] 4) The above-mentioned hydrated ferromanganese phosphate was heat-treated at 430℃ for 4 hours to obtain ferromanganese phosphate powder. The D50 of the ferromanganese phosphate powder was measured to be 4.31 μm, and the tap density TD was 0.86 g / cm³. 3 The specific surface area (BET) is 44.08 m². 2 / g.

[0126] Comparative Example 3

[0127] The preparation process of a nanoporous manganese iron phosphate differs from that of Example 1 only in that the heat treatment temperature in step 4) is different. The specific preparation process is as follows:

[0128] 1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. After washing and filtration, amorphous ferric phosphate was obtained as the iron source required for the preparation of manganese ferric phosphate.

[0129] 2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese ferric phosphate.

[0130] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the manganese source and iron source are first mixed to form a slurry with a solid content of 20%. Then, the slurry is added to the 85% wt phosphoric acid, and the reaction is carried out at a temperature of 90℃. The feeding time of the slurry is controlled to be 1 hour. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, wherein the drying temperature is 120℃.

[0131] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 380°C for 4 hours to obtain manganese ferric phosphate powder.

[0132] Comparative Example 4

[0133] The preparation process of a nanoporous manganese iron phosphate differs from that of Example 1 only in that the heat treatment temperature in step (4) is different. The specific preparation process is as follows:

[0134] (1) Ferrous sulfate, ammonium dihydrogen phosphate and hydrogen peroxide were used to carry out a precipitation reaction according to a stoichiometric ratio of 1:1.2:0.7. Then, after washing and filtration, amorphous iron phosphate was obtained as the iron source required for the preparation of manganese iron phosphate.

[0135] (2) Manganese sulfate, ammonia and hydrogen peroxide were used to carry out a precipitation reaction according to the stoichiometric ratio of 1:2.5:0.7. Then, manganese hydroxide was obtained by washing and filtering, which was used as the manganese source for the preparation of manganese iron phosphate.

[0136] 3) Using the above-mentioned iron source, manganese source, and 85% wt industrial phosphoric acid, with a stoichiometric ratio of Mn:Fe = 65:35 and (Mn+Fe):P = 1:0.8, the manganese source and iron source are first mixed to form a slurry with a solid content of 20%. Then, the slurry is added to the 85% wt phosphoric acid, and the reaction is carried out at a temperature of 90℃. The feeding time of the slurry is controlled to be 1 hour. After the reaction is completed, the resulting material is washed, filtered, and dried to obtain hydrated manganese ferric phosphate, wherein the drying temperature is 120℃.

[0137] 4) The above-mentioned hydrated manganese ferric phosphate was heat-treated at 500℃ for 4 hours to obtain manganese ferric phosphate powder.

[0138] Methods for preparing cathode materials:

[0139] The iron manganese phosphate in the examples and comparative examples was prepared into lithium manganese iron phosphate. The specific operation of lithium manganese iron phosphate is as follows:

[0140] 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%.

[0141] 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.

[0142] 3) The slurry with qualified particle size after grinding is then introduced into a spray dryer by a peristaltic pump for drying and molding.

[0143] 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).

[0144] Electrochemical performance testing methods:

[0145] 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 forming an LMFP / C cathode sheet. 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. The battery was then subjected to charge-discharge tests (charge-discharge window of 2.5V-4.3V) to determine the electrical performance of lithium manganese iron phosphate.

[0146] The particle size D50 was obtained by measuring the Malvern 3000 laser particle size analyzer, referring to the standard GB / T19077-2016.

[0147] XRD was obtained by X-ray diffraction, and the determination was made in accordance with the standard GA / T 2079-2023. The crystal structure of each sample was tested using a Rigaku SmartLab 9kW X-ray diffractometer (XRD, Cu Kα1), with a scanning range of 5-60° and a scanning rate of 2° / min.

[0148] Specific surface area (BET) is determined according to GB / T 19587-2017, which specifies the determination of solid substances by gas adsorption BET method.

[0149] The test reference standard for tap density (TD) is GB / T 5162-2021 Determination of tap density of metal powders.

[0150] The method for measuring grain size is as follows:

[0151] Jade 6.5 was used to refine and fit the full XRD spectrum. The full width at half maximum (FWHM) of the main diffraction peaks and their corresponding crystal plane dimensions (110, -111, 111, 021, -202, 022) were output using Jade software. The average grain size was obtained by averaging the dimensions of the six crystal planes. The calculations in Jade software are based on the Scherrer formula, which is expressed as follows:

[0152] D = Kλ / (βcosθ)

[0153] Where D is the grain size; K is a constant with a value of 0.934; λ is the X-ray wavelength, which is 0.154056 nm; β is the full width at half maximum (FWHM) of the diffraction peak, which is expressed in radians during the calculation; and θ is the diffraction angle.

[0154] The formula for calculating the average grain size is as follows:

[0155] D_flat = (D1 + D2 + D3 + D4 + D5 + D6) / 6

[0156] D_flat, D1, D2, D3, D4, D5, and D6 represent the average grain size, and the grain sizes of crystal planes 110, -111, 111, 021, -202, and 022, respectively.

[0157] Table 1 Grain size and crystallinity

[0158] Table 2 Electrochemical Performance Table

[0159] Based on Table 1 and Figures 1-5, it can be seen that the XRD spectrum in Comparative Example 1 has a smaller full width at half maximum (FWHM), indicating that its grain size is larger. The reason is that the slow slurry feeding rate reduces the overall dissolution rate of the iron and manganese sources, which is conducive to the slow growth of grains, thus resulting in a larger grain size.

[0160] The larger full width at half maximum (FWHM) of the XRD spectrum in Comparative Example 2 indicates a smaller grain size, but the sample has low crystallinity. This is because the rapid mixing of the slurry with phosphoric acid causes the dissolution of the iron and manganese sources, and the crystallization and precipitation of iron and manganese ions, to occur rapidly within a short time. This is unfavorable for the slow growth of grains and crystals, resulting in a smaller grain size and lower crystallinity.

[0161] In Comparative Example 3, hydrated manganese ferrophosphate was heat-treated at 380°C, and the resulting manganese ferrophosphate contained water of crystallization. The content of this water of crystallization was consistent with that of the untreated manganese ferrophosphate. The XRD is shown in Figure 4. The peak angle, diffraction intensity, and full width at half maximum (FWHM) of the diffraction peaks in this manganese ferrophosphate were basically unchanged from those in the hydrated manganese ferrophosphate XRD of Example 1. The difference between this and the final XRD of the manganese ferrophosphate in Example 1 was large, and the grain size was outside the range.

[0162] In Comparative Example 4, after sintering hydrated manganese ferrophosphate at 500℃, pores were generated, the material melted, the primary particle structure collapsed, and the grains broke apart. As shown in Figure 5, manganese pyrophosphate diffraction peaks appeared between 27° and 29°, indicating that some manganese ferrophosphate decomposed to form manganese pyrophosphate. Since the crystal structure of Comparative Example 4 had completely collapsed, the accurate grain size could not be calculated.

[0163] Furthermore, combining Tables 1 and 2, it can be seen that the electrochemical performance of cathode materials prepared with manganese ferrophosphate within an appropriate range of full width at half maximum (FWHM) and grain size will reach its optimal state. Changing the reaction conditions of the manganese and iron sources, the sintering temperature of hydrated manganese ferrophosphate, and other parameters will change the grain size. When the grain size is outside this range, it will lead to varying degrees of decrease in the discharge capacity of manganese ferrophosphate. When the grain size is above 28 nm, it still retains more than 95% of its capacity after 1000 cycles under 1C charge-discharge conditions.

[0164] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure. Industrial applicability

[0165] In summary, this disclosure provides a method for preparing ferromanganese phosphate, wherein the average grain size of the provided ferromanganese phosphate on the (111), (110), (-111), (021), (-202), and (022) crystal planes is 28.0 nm-40.0 nm. The ferromanganese phosphate provided in this disclosure can be used to prepare lithium iron phosphate with excellent capacity, rate capability, and cycle performance. By selecting the grain size of the ferromanganese phosphate, it is possible to ensure both sufficient reaction with carbon and lithium sources and to maintain high crystallinity and a complete crystal structure, thereby improving the charge / discharge capacity and rate capability of lithium iron phosphate.

Claims

1. A type of manganese iron phosphate, wherein, The average grain size of the manganese iron phosphate on the (111), (110), (-111), (021), (-202), and (022) crystal planes is 28.0 nm to 40.0 nm.

2. The manganese iron phosphate according to claim 1, wherein, The ferric manganese phosphate satisfies one or more of the following conditions: (1)(111) The grain size of the crystal plane is 30.0 nm-40.0 nm; (2) The grain size of the (110) crystal plane is 40.0 nm-50.0 nm; (3) The grain size of the (-111) crystal plane is 40.0 nm-50.0 nm; (4)(021) The grain size of the crystal plane is 30.0 nm-40.0 nm; (5) The grain size of the (-202) crystal plane is 25.0 nm-40.0 nm; (6)(022) The grain size of the crystal plane is 20.0nm-30.0nm.

3. The ferromanganese phosphate according to claim 1 or 2, wherein, The ferric manganese phosphate satisfies one or more of the following conditions A to D: A. The D50 of the manganese iron phosphate is 1μm-20μm; B. The specific surface area of ​​the manganese iron phosphate is 6 m². 2 / g-20m 2 / g; C. The pore volume of the manganese ferric phosphate is 0.020 cm³. 3 / g-0.030cm 3 / g; D. The average pore size of the manganese iron phosphate is 12.0 nm-20.0 nm.

4. The manganese iron phosphate according to any one of claims 1-3, wherein, The chemical formula of the manganese iron phosphate is Mn. 1-x Fe x PO4, 0.01≤x≤0.

99.

5. A method for preparing ferric manganese phosphate according to any one of claims 1-4, wherein, It includes: mixing an iron source and a manganese source to form a slurry, reacting it with phosphoric acid to obtain hydrated manganese ferric phosphate; and then heat-treating the hydrated manganese ferric phosphate to obtain manganese ferric phosphate.

6. The preparation method according to claim 5, wherein, The preparation of the hydrated manganese ferric phosphate includes: mixing an iron source and a manganese source to obtain a slurry with a solid content of 5%-20%; then adding the slurry to phosphoric acid; maintaining the temperature at 20℃-100℃ for reaction; controlling the slurry feeding time to be 0.5h-1.5h; after the reaction is completed, washing, filtering and drying are performed to obtain hydrated manganese ferric phosphate. Optionally, the molar ratio of the iron source to the manganese source is (1-99):(99-1); the molar ratio of the phosphoric acid to the total molar ratio of the iron source and the manganese source is 1:(0.6-1). Optionally, the iron source includes one or more of amorphous iron phosphate, amorphous ammonium iron phosphate, and amorphous hydroxy iron phosphate, and the manganese source includes one or more of manganese hydroxide, manganese tetroxide, manganese dioxide, hydrated manganese dioxide, manganese hydroxide, and manganese trioxide. Optionally, the drying temperature is 80℃-120℃, and the drying time is 2h-12h.

7. The preparation method according to any one of claims 5-6, wherein, The hydrated manganese ferric phosphate was heat-treated at 400℃-480℃ for 2h-8h to obtain manganese ferric phosphate.

8. A lithium manganese iron phosphate, wherein, 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 the preparation method described in any one of claims 5-7.

9. A lithium-ion battery, wherein, The cathode material of the lithium-ion battery includes lithium manganese iron phosphate as described in claim 8.

10. An electrical-related device, wherein, Including the lithium-ion battery as described in claim 9.

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