Nanoscale orthogonal iron phosphate and its preparation method and preparation method of lithium iron phosphate cathode material

Abstract

This application provides a method for preparing nano-sized orthogonal iron phosphate and a method for preparing lithium iron phosphate cathode materials, relating to the field of electrode materials. The method for preparing nano-sized orthogonal iron phosphate includes: mixing a first ferrous salt solution with a first phosphorus source solution and an oxidant to perform a co-precipitation reaction to obtain amorphous iron phosphate; mixing the amorphous iron phosphate with water to form a slurry, controlling the slurry particle size, and then adding a crystal transformation aid to the slurry, followed by aging under stirring conditions at a pH of 0.8–1.5 to obtain nano-sized orthogonal iron phosphate; wherein the crystal transformation aid includes a second ferrous salt and a second phosphorus source. The iron phosphate prepared in this application is single-crystal nano-sized orthogonal iron phosphate, reducing the grinding pressure at the lithium iron phosphate end. Simultaneously, its unique octahedral structure is more stable than monoclinic iron phosphate produced by conventional processes, with fewer crystal defects and higher lattice integrity, effectively avoiding the generation of magnetic foreign matter during sintering and contributing to the performance of lithium iron phosphate materials.

Description

Technical Field

[0001] This application relates to the field of electrode materials, and in particular to a nanoscale orthogonal iron phosphate and its preparation method and a method for preparing lithium iron phosphate cathode materials. Background Technology

[0002] In recent years, with the rapid development of electric vehicles and energy storage, the market demand for lithium-ion batteries has been continuously increasing. Lithium iron phosphate cathode material is one of the mainstream cathode materials for power batteries and energy storage batteries.

[0003] As a precursor for lithium iron phosphate (LFP), the physicochemical properties (such as crystal form, purity, particle size, and morphology) directly affect the electrochemical performance of LFP. Currently, the ammonium method is commonly used industrially to synthesize monoclinic LFP. However, this route has the following drawbacks: the iron-to-phosphorus ratio is relatively low, typically between 0.960 and 0.970 for mainstream monoclinic LFP. While this characteristic helps improve the compaction density of the material, it easily generates magnetic foreign matter such as iron phosphide, which can pose safety hazards. Moreover, due to these structural defects, the capacity, rate performance, and cycle stability of the prepared LFP materials are all poor.

[0004] To address these issues, researchers discovered that orthorhombic iron phosphate exhibits higher crystallinity and structural stability, making it a potential candidate for next-generation high-energy-density lithium iron phosphate materials. However, existing orthorhombic iron phosphate preparation techniques suffer from several problems: current methods are complex, require stringent control, and suffer from poor stability in industrial production; moreover, they easily generate impurities such as monoclinic crystals during the reaction, resulting in low crystal phase purity of the final product; furthermore, the primary particle size of orthorhombic iron phosphate reported so far is mostly in the micrometer range, even exceeding 10 μm, leading to high energy consumption and difficulty in dispersion during subsequent lithium iron phosphate preparation, hindering the uniform mixing and nano-sizing of active materials and ultimately impairing the performance of lithium iron phosphate batteries.

[0005] Therefore, it is necessary to improve the preparation method of orthogonal ferric phosphate. Summary of the Invention

[0006] The purpose of this application is to provide a nanoscale orthogonal iron phosphate and its preparation method, as well as a method for preparing lithium iron phosphate cathode materials, to solve the problem that existing orthogonal iron phosphate preparation methods are difficult to achieve both high crystal phase purity and nanoscale products. Thus, when used as a lithium iron phosphate precursor, it can improve the compaction density and electrochemical performance of lithium iron phosphate cathode materials.

[0007] To achieve the above objectives, this application adopts the following technical solution: A method for preparing nanoscale orthogonal iron phosphate, comprising: The first ferrous salt solution was mixed with the first phosphorus source solution and the oxidant to carry out a co-precipitation reaction to obtain amorphous ferric phosphate; The amorphous ferric phosphate is mixed with water to form a slurry, the particle size of the slurry is adjusted, and then a crystallization aid is added to the slurry. The slurry is aged under stirring conditions with a pH of 0.8 to 1.5 to obtain nano-sized orthogonal ferric phosphate. The crystallization aid includes a second ferrous salt and a second phosphorus source.

[0008] According to embodiments of this application, the first ferrous salt and the second ferrous salt are independently selected from at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride; And / or, the concentration of the first ferrous salt solution is 0.5-3 mol / L; And / or, the pH of the first ferrous salt solution is 2.0-3.0; And / or, the first phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; And / or, the concentration of the first phosphorus source solution is 0.5–3 mol / L; And / or, the pH of the first phosphorus source solution is 6-7; And / or, the molar ratio of the first ferrous salt to the first phosphorus source is (0.95~1.05):1; And / or, the molar ratio of the oxidant to the molar ratio of the first ferrous salt is (0.5 to 0.7):1.

[0009] According to embodiments of this application, the oxidant includes at least one of oxygen, ozone, hydrogen peroxide, and ammonium persulfate; And / or, mixing the first ferrous salt solution with the first phosphorus source solution and the oxidant includes: adding the first phosphorus source solution and the oxidant to the first ferrous salt solution in a co-current feeding manner.

[0010] According to an embodiment of this application, the temperature of the coprecipitation reaction is 30–80°C, and the time of the coprecipitation reaction is 0.5–5 h; And / or, after the coprecipitation reaction is completed, the method further includes: performing a first solid-liquid separation and a first washing on the obtained precipitate in sequence, wherein the endpoint of the first washing is that the conductivity of the washing liquid is ≤2000μS / cm.

[0011] According to an embodiment of this application, the solid content of the slurry is 100–200 g / L; And / or, the control of slurry particle size includes: controlling the slurry particle size to <150 μm by using a shear pump.

[0012] According to embodiments of this application, the second phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate. And / or, during aging, the method further includes adjusting the pH of the reaction system to 0.8–1.5 by adding a sulfuric acid solution.

[0013] According to an embodiment of this application, the molar ratio of phosphorus in the second phosphorus source to the molar ratio of ferrous ions in the second ferrous salt is 1:(0.01-0.05). And / or, the ratio of the molar amount of iron in the amorphous iron phosphate to the molar amount of phosphorus in the second phosphorus source is 1:(0.1-2).

[0014] According to an embodiment of this application, the aging temperature is 80-100°C; And / or, the aging time is 0.5-4 h; And / or, the stirring speed is 250-500 rpm.

[0015] According to an embodiment of this application, after aging is completed, the method further includes: sequentially performing a second solid-liquid separation, a second washing, and drying on the aged slurry, wherein the endpoint of the second washing is that the conductivity of the filtrate is ≤600μS / cm; And / or, the drying temperature is 80-120℃, and the drying time is 0.5-6h; And / or, the method further includes: recovering the aged mother liquor and reusing the recovered mother liquor as part of the crystallization aid.

[0016] This application also provides a nano-sized orthogonal iron phosphate, which is prepared by the preparation method described above; The primary particle size of the nano-sized orthogonal iron phosphate is 80-400 nm.

[0017] This application also provides a method for preparing a lithium iron phosphate cathode material, including: The nano-sized orthogonal ferric phosphate described above was calcined to obtain anhydrous ferric phosphate. The anhydrous iron phosphate was mixed with a lithium source, a carbon source and a solvent to obtain a mixed slurry; The mixed slurry is dried to obtain a dried material; The dried material is sintered to obtain lithium iron phosphate cathode material.

[0018] Compared with the prior art, the beneficial effects of this application include: Compared with existing methods for preparing orthogonal iron phosphate, this application can stably obtain a pure phase orthogonal iron phosphate crystal structure and can control the primary particle size of iron phosphate to the nanoscale. The lithium iron phosphate cathode material prepared from the nanoscale orthogonal iron phosphate of this application has both high compaction density and excellent electrochemical performance, which solves the technical bottleneck of low compaction density and poor electrochemical performance of existing micron-sized orthogonal iron phosphate in subsequent applications.

[0019] 1. The iron phosphate prepared in this application is single-crystal nano-sized orthorhombic iron phosphate, which reduces the grinding pressure at the lithium iron phosphate end. The orthorhombic iron phosphate of this application has a unique regular octahedral structure, which is more stable than monoclinic iron phosphate produced by conventional processes, with fewer crystal defects and higher lattice integrity. It can effectively avoid the generation of magnetic foreign matter during sintering and contribute to the electrochemical performance of lithium iron phosphate materials.

[0020] 2. The iron phosphate prepared in this application is a pure orthorhombic crystal, unlike the monoclinic iron phosphate produced by conventional processes. Its unique octahedral crystal structure has higher crystallinity and lattice integrity, with fewer crystal defects. This structural feature can effectively suppress the formation of magnetic foreign matter such as iron phosphide (FeP, Fe2P) during the subsequent high-temperature solid-state reaction preparation of lithium iron phosphate, thereby significantly improving the safety, consistency, and cycle stability of the battery.

[0021] 3. The orthogonal iron phosphate prepared in this application has a high tap density, which is an ideal precursor for preparing high-taper lithium iron phosphate materials. It is beneficial to obtain electrode sheets with high tap density, which helps to improve the volumetric energy density of lithium-ion batteries and meet the high energy density requirements of power batteries and energy storage batteries.

[0022] 4. The method of this application also has the advantages of simple process and easy operation, and is easy to realize stable and continuous large-scale industrial production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, 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 application and should not be regarded as a limitation on the scope of this application.

[0024] Figure 1 These are the XRD patterns of ferric phosphate prepared in Examples 1-3 and Comparative Examples 1-4, and the standard cards for orthorhombic and monoclinic ferric phosphate. Figure 2 Here is a SEM image of the iron phosphate prepared in Example 1; Figure 3 Here is a SEM image of the ferric phosphate prepared in Example 3; Figure 4 This is a SEM image of the iron phosphate prepared in Comparative Example 1; Figure 5 This is a SEM image of the iron phosphate prepared in Comparative Example 2; Figure 6 This is a SEM image of the iron phosphate prepared in Comparative Example 3; Figure 7 This is a SEM image of the iron phosphate prepared in Comparative Example 4. Detailed Implementation

[0025] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0026] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0027] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0028] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0029] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0030] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0031] A method for preparing nanoscale orthogonal iron phosphate, comprising: The first ferrous salt solution was mixed with the first phosphorus source solution and the oxidant to carry out a co-precipitation reaction to obtain amorphous ferric phosphate; The amorphous ferric phosphate is mixed with water to form a slurry, the particle size of the slurry is adjusted, and then a crystallization aid is added to the slurry. The slurry is aged under stirring conditions with a pH of 0.8 to 1.5 (e.g., 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any value between 0.8 and 1.5) to obtain nano-sized orthogonal ferric phosphate; wherein the crystallization aid includes a second ferrous salt and a second phosphorus source.

[0032] According to embodiments of this application, the first ferrous salt and the second ferrous salt are independently selected from at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride; The concentration of the first ferrous salt solution is 0.5-3 mol / L; for example, the concentration of the first ferrous salt solution is 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or any value between 0.5-3 mol / L.

[0033] The pH of the first ferrous salt solution is 2.0-3.0. Controlling the pH of the first ferrous salt solution within this range can effectively prevent premature oxidation of the ferrous salt and effectively prevent the formation of impurities such as ferric hydroxide during the precipitation process.

[0034] For example, the pH of the first ferrous salt solution is 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 or any value between 2.0 and 3.0.

[0035] The first phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate. The concentration of the first phosphorus source solution is 0.5 to 3 mol / L; for example, the concentration of the first phosphorus source solution is 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or any value between 0.5 and 3 mol / L.

[0036] The pH of the first phosphorus source solution is 6-7; when the pH of the first phosphate salt solution is within the above range, the generation of other impurities such as ferric hydroxide and basic ferric phosphate can be effectively avoided during the precipitation process.

[0037] For example, the pH of the first phosphorus source solution is any value between 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, or 6-7.

[0038] The molar ratio of the first ferrous salt to the first phosphorus source is (0.95–1.05):1. For example, the molar ratio of the first ferrous salt to the first phosphorus source is any value between 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, or (0.95–1.05):1.

[0039] The molar ratio of the oxidant to the first ferrous salt is (0.5 to 0.7):1. For example, the molar ratio of the oxidant to the first ferrous salt is any value between 0.5:1, 0.6:1, 0.7:1, or (0.5 to 0.7):1.

[0040] According to embodiments of this application, the oxidant includes at least one of oxygen, ozone, hydrogen peroxide, and ammonium persulfate; The mixing of the first ferrous salt solution with the first phosphorus source solution and the oxidant includes adding the first phosphorus source solution and the oxidant to the first ferrous salt solution in a co-current feeding manner. This ensures the uniform distribution of elements during the oxidation and precipitation processes, guaranteeing the uniform and stable properties of the produced amorphous ferric phosphate, thus providing a prerequisite for the subsequent preparation of nano-sized orthogonal ferric phosphate.

[0041] According to an embodiment of this application, the temperature of the coprecipitation reaction is 30–80°C, and the time of the coprecipitation reaction is 0.5–5 h; for example, the temperature of the coprecipitation reaction is any value between 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 30–80°C, and the time of the coprecipitation reaction is any value between 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, or 0.5–5 h.

[0042] After the coprecipitation reaction is completed, the method further includes: sequentially performing a first solid-liquid separation and a first washing on the obtained precipitate, wherein the endpoint of the first washing is that the conductivity of the washing solution is ≤2000 μS / cm. This effectively reduces the entrainment level of impurity elements in the synthesized material, improves product quality, and avoids the formation of other impurity phases such as monoclinic ferric phosphate, basic ferric phosphate, and other hydrated phosphate complexes during the crystal transformation process.

[0043] According to embodiments of this application, the solid content of the slurry is 100–200 g / L; for example, the solid content of the slurry is any value between 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, or 100–200 g / L.

[0044] The controlled slurry particle size includes controlling the slurry particle size to <150μm using a shear pump. Compared to the traditional reaction vessel mixing method, the method of this application (controlling the slurry particle size using a shear pump) significantly shortens the pulping time, achieves finer control of the pulping particle size, and accelerates the reaction rate between the material and the crystallization aid.

[0045] According to embodiments of this application, the second phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate. During the aging process, the method further includes adjusting the pH of the reaction system to 0.8–1.5 by adding sulfuric acid solution. When the pH of the reaction system is 0.8–1.5, amorphous ferric phosphate can dissolve rapidly within 10 minutes.

[0046] According to an embodiment of this application, the molar ratio of phosphorus in the second phosphorus source to the molar ratio of ferrous ions in the second ferrous salt is 1:(0.01-0.05); for example, the molar ratio of phosphorus in the second phosphorus source to the molar ratio of ferrous ions in the second ferrous salt is any value between 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05 or 1:(0.01-0.05).

[0047] The molar ratio of iron in the amorphous ferric phosphate to phosphorus in the second phosphate salt is 1:(0.1-2). For example, the molar ratio of iron in the amorphous ferric phosphate to phosphorus in the second phosphate salt can be any value between 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:1, 1:1.5, 1:2, or 1:(0.5-2).

[0048] Under the above conditions, the supersaturation of iron and phosphorus in the system can be increased, which helps to rapidly and massively nucleate during the crystallization process, thereby forming nano-sized orthogonal iron phosphate.

[0049] According to an embodiment of this application, the aging temperature is 80-100°C; within the above temperature range, the supersaturation of iron and phosphorus in the system can be increased, which helps to rapidly and massively nucleate during the crystallization process, thereby forming nano-sized orthogonal iron phosphate.

[0050] For example, the aging temperature is 80℃, 85℃, 90℃, 95℃, 100℃ or any value between 80℃ and 100℃.

[0051] It should be noted that during the aging process, ferrous sulfate in the crystallization aid only plays a catalytic role and does not participate in the chemical reaction. It can be reused as a resource through mother liquor recycling, together with the high phosphorus content in the mother liquor.

[0052] The aging time is 0.5-4 h; for example, the aging time is any value between 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h or 0.5-4 h.

[0053] The stirring speed is 250-500 rpm. For example, the stirring speed is 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any value between 250-500 rpm.

[0054] According to an embodiment of this application, after aging is completed, the method further includes: sequentially performing a second solid-liquid separation, a second washing, and drying on the aged slurry, wherein the endpoint of the second washing is that the conductivity of the filtrate is ≤600μS / cm; The drying temperature is 80-120℃, and the drying time is 0.5-6h; for example, the drying temperature is 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ or any value between 80-120℃, and the drying time is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or any value between 0.5-6h.

[0055] The method further includes: recovering the aged mother liquor and reusing the recovered mother liquor as a partial crystallization aid. The residual phosphorus and ferrous ions in the aged mother liquor of this application can be detected by concentration analysis based on P-Fe... 2+The conservation rules are fully applied to the crystallization process, which can achieve 100% utilization of all effective elements in the aging mother liquor, greatly reduce production costs, avoid waste of iron, phosphorus and water resources, and reduce pollution.

[0056] This application also provides a nano-sized orthogonal iron phosphate, which is prepared by the preparation method described above; The primary particle size of the nano-sized orthogonal ferric phosphate is 80-400 nm. For example, the primary particle size of the nano-sized orthogonal ferric phosphate is 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 270 nm, 300 nm, 320 nm, 350 nm, 370 nm, 400 nm or any value between 80-400 nm.

[0057] The lithium iron phosphate products prepared by nanoscale orthogonal iron phosphate according to this application have the combined advantages of high compaction density, high capacity, excellent rate performance and long cycle life, which can meet the application requirements of the next generation of high energy density and high power density lithium-ion batteries.

[0058] This application also provides a method for preparing a lithium iron phosphate cathode material, including: The nano-sized orthogonal ferric phosphate described above is calcined to obtain anhydrous ferric phosphate. This step can remove the water of crystallization from the nano-sized orthogonal ferric phosphate. In some embodiments, the calcination temperature is 550-600℃, such as 550℃, 580℃, 600℃ or any value between 550-600℃, and the calcination time is any value between 1h, 2h, 3h or 1-3h. The anhydrous iron phosphate precursor is mixed with a lithium source, a carbon source, and a solvent to obtain a mixed slurry; for example, the lithium source includes lithium carbonate, and the carbon source includes at least one of sucrose and PEG; the molar ratio of Li in the lithium source to the molar ratio of Fe in the anhydrous iron phosphate is (1-1.1):1, for example, 1:1, 1.05:1, 1.1:1, or any value between (1-1.1):1, and the mass of the carbon source accounts for 6%-16% of the mass of the anhydrous iron phosphate (for example, 6%, 8%, 10%, 12%, 14%, 16%, or any value between 6-16%). The mixed slurry is dried to obtain a dried material; The dried material is sintered to obtain lithium iron phosphate cathode material. For example, the sintering temperature is 700-800℃ (e.g., 700℃, 750℃, 800℃ or any value between 700-800℃), and the time is 4-8h (e.g., 4h, 6h, 8h or any value between 4-8h).

[0059] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0060] Example 1 Example 1 provides a nanoscale orthogonal iron phosphate, the preparation method of which includes: ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.0. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 0.98:1, and the molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0061] Using hydrogen peroxide as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1, ammonium dihydrogen phosphate solution and hydrogen peroxide were added to the ferrous sulfate solution via a co-current feed method, followed by stirring at 30°C for 0.5 h. After the reaction was completed, the mixture was filtered and washed, with the conductivity controlled to be below 2000 μS / cm at the washing endpoint, to obtain amorphous ferric phosphate.

[0062] ② The above-mentioned amorphous ferric phosphate is mixed with pure water to make a slurry. The particle size of the slurry is controlled to be <150μm by a shear pump, and the solid content of the slurry is controlled to be 120g / L. Then, a crystallization aid is added and the slurry is aged.

[0063] The crystallization aid is a mixture of ammonium dihydrogen phosphate and ferrous sulfate. The molar ratio of phosphorus (P) to ferrous ions in the crystallization aid is 1:0.02. The amorphous ferric phosphate contains Fe... 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.56. Sulfuric acid solution was added to the reaction system to control the pH of the slurry to 0.8. The aging stirring speed was 300 rpm, the aging temperature was 80℃, and the holding time was 2 h. Subsequently, the slurry was filtered, washed, and the conductivity at the washing endpoint was controlled to be below 600 μS / cm. The sample was then dried at 120℃ for 6 h to obtain orthogonal ferric phosphate.

[0064] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the product prepared in Example 1 is pure-phase orthogonal ferric phosphate. Figure 2 This is a SEM image of the iron phosphate prepared in Example 1, magnified 20,000 times, showing a distinct single-crystal granular morphology.

[0065] Test results show that the product of Example 1 is a pure-phase orthorhombic ferric phosphate with an average primary particle size of 200 nm and a tap density of 1.2 g / cm³.3 .

[0066] Example 2 Example 2 provides a nanoscale orthogonal iron phosphate, the preparation method of which includes: ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.4. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 1:1. The molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0067] Using hydrogen peroxide as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1, ammonium dihydrogen phosphate solution and hydrogen peroxide were added to the ferrous sulfate solution via a co-current feed method, followed by stirring at 50°C for 0.5 h. After the reaction was completed, the mixture was filtered and washed, with the conductivity controlled to be below 2000 μS / cm at the washing endpoint, to obtain amorphous ferric phosphate.

[0068] ② The above-mentioned amorphous ferric phosphate is mixed with pure water to make a slurry. The particle size of the slurry is controlled to be <150μm by a shear pump, and the solid content of the slurry is controlled to be 120g / L. Then, a crystallization aid is added and the slurry is aged.

[0069] The crystallization aid is a mixture of ammonium dihydrogen phosphate and ferrous sulfate. The molar ratio of phosphorus (P) to ferrous ions in the crystallization aid is 1:0.02. The amorphous ferric phosphate contains Fe... 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.56. Sulfuric acid solution was added to the reaction system to control the slurry pH to 0.8. The aging process involved stirring at 300 rpm at 80℃ for 2 hours. The slurry was then filtered, washed, and the conductivity at the washing endpoint was controlled to be below 600 μS / cm. The sample was then dried at 120℃ for 6 hours to obtain ferric phosphate.

[0070] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. The test results showed that the product prepared in Example 2 was a pure-phase orthorhombic ferric phosphate with an average primary particle size of 250 nm and a tap density of 1.1 g / cm³. 3 .

[0071] Example 3 Example 3 provides a nanoscale orthogonal iron phosphate, the preparation method of which includes: ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.0. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 0.98:1, and the molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0072] Hydrogen peroxide was used as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1. Ammonium dihydrogen phosphate solution and hydrogen peroxide were added to the ferrous sulfate solution via a co-current feed method, and the reaction was carried out at 30°C with stirring for 0.5 h. After the reaction, the mixture was filtered and washed, with the conductivity controlled to be below 2000 μS / cm at the washing endpoint, to obtain amorphous ferric phosphate.

[0073] ② The above-mentioned amorphous ferric phosphate is mixed with pure water to make a slurry. The particle size of the slurry is controlled to be <150μm by a shear pump, and the solid content of the slurry is controlled to be 100g / L. Then, a crystallization aid is added and the slurry is aged.

[0074] The crystallization aid is a mixture of ammonium dihydrogen phosphate and ferrous sulfate. The molar ratio of phosphorus (P) to ferrous ions in the crystallization aid is 1:0.03. The amorphous ferric phosphate contains Fe... 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.1. Sulfuric acid solution was added to the reaction system to control the slurry pH to 0.8. The aging process involved stirring at 300 rpm at 80°C for 2 hours. The slurry was then filtered, washed, and the conductivity at the washing endpoint was controlled to be below 600 μS / cm. The sample was then dried at 120°C for 6 hours to obtain ferric phosphate.

[0075] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the product prepared in Example 3 is pure-phase orthogonal ferric phosphate. Figure 3 This is a SEM image of the iron phosphate prepared in Example 3, magnified 10,000 times, showing a distinct granular morphology. The average primary particle size is 280 nm, and the tap density is 1.1 g / cm³. 3 .

[0076] Comparative Example 1 ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.0. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 0.98:1, and the molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0077] Using hydrogen peroxide as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1, ammonium dihydrogen phosphate solution was added to the ferrous sulfate solution first, followed by hydrogen peroxide after the ammonium dihydrogen phosphate solution was added. The reaction was then stirred at 30°C for 0.5 h. After the reaction, the mixture was filtered and washed, with the conductivity controlled to be below 2000 μS / cm at the washing endpoint, to obtain amorphous ferric phosphate.

[0078] ② The above-mentioned amorphous ferric phosphate is mixed with pure water to make a slurry. The particle size of the slurry is controlled to be <150μm by a shear pump, and the solid content of the slurry is controlled to be 120g / L. Then, a crystallization aid is added and the slurry is aged.

[0079] The crystallization aid is ammonium dihydrogen phosphate, and Fe in amorphous iron phosphate. 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.56. Sulfuric acid solution was added to the reaction system to control the slurry pH to 0.8. The aging process involved stirring at 300 rpm at 80℃ for 2 hours. The slurry was then filtered, washed, and the conductivity at the washing endpoint was controlled to be below 600 μS / cm. The sample was then dried at 120℃ for 6 hours to obtain ferric phosphate.

[0080] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the iron phosphate prepared in Comparative Example 1 is an orthorhombic and monoclinic iron phosphate. Figure 4 The image shows a SEM image of the ferric phosphate prepared in Comparative Example 1, magnified 10,000 times. It exhibits distinct granular and flaky morphologies, with no unique morphology and noticeable agglomeration. The tap density of the ferric phosphate in Comparative Example 1 is 0.68 g / cm³. 3 .

[0081] The difference between Comparative Example 1 and Example 1 is that in step ①, ammonium dihydrogen phosphate solution is added first and then hydrogen peroxide is added, which results in the formation of related complexes such as ferrous ammonium phosphate before the addition of hydrogen peroxide, affecting the oxidation efficiency of the oxidant and the elemental distribution of amorphous iron phosphate material; in step ②, the crystallization aid is only ammonium dihydrogen phosphate, and the absence of ferrous phosphate makes it impossible to catalyze the complete crystallization of iron phosphate into orthorhombic iron phosphate, and under thermodynamic impetus, some crystallization is generated to form monoclinic iron phosphate.

[0082] Comparative Example 2 ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.0. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 0.98:1, and the molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0083] Using hydrogen peroxide as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1, ammonium dihydrogen phosphate solution and hydrogen peroxide were added to the ferrous sulfate solution via a co-current feed method, followed by stirring at 30°C for 0.5 h. After the reaction was completed, the mixture was filtered and washed, with the conductivity controlled to be below 2000 μS / cm at the washing endpoint, to obtain amorphous ferric phosphate.

[0084] ② Add pure water to the above amorphous ferric phosphate to make a slurry, control the solid content of the slurry to 120g / L, stir at 400rpm for 20min, and then add crystallization aid for aging.

[0085] The crystallization aid is a mixture of ammonium dihydrogen phosphate and ferrous sulfate. The molar ratio of phosphorus (P) to ferrous ions in the crystallization aid is 1:0.02. The amorphous ferric phosphate contains Fe... 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.56. Sulfuric acid solution was added to the reaction system to control the slurry pH to 2.0. The aging process involved stirring at 300 rpm at 80℃ for 2 hours. The slurry was then filtered and washed, with the final conductivity controlled below 600 μS / cm. The sample was then dried at 120℃ for 6 hours to obtain ferric phosphate.

[0086] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the product prepared in Comparative Example 2 is orthogonal iron phosphate. Figure 5 The image shown is a SEM image of the iron phosphate prepared in Comparative Example 2, magnified 10,000 times. It exhibits a distinct large single-crystal bulk morphology, with an average primary particle size of 2.5 μm. The tap density of the iron phosphate in Comparative Example 2 is 0.83 g / cm³. 3 .

[0087] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, step ② omits the step of controlling the slurry particle size to <150μm using a shear pump. Insufficient slurrying hinders the crystallization process, and the aging pH is 2.0. An excessively high aging pH results in a slow dissolution rate of amorphous ferric phosphate. Furthermore, the inability to rapidly dissolve amorphous ferric phosphate leads to a nucleation rate < growth rate during the formation of orthogonal ferric phosphate, resulting in larger orthogonal ferric phosphate particles.

[0088] Comparative Example 3 ① Prepare ferrous sulfate solution and ammonium dihydrogen phosphate solution separately. The molar concentration of the ferrous sulfate solution is 1 mol / L and the pH is 2.0. The molar ratio of ferrous sulfate solution to ammonium dihydrogen phosphate solution is 0.98:1, and the molar concentration of the ammonium dihydrogen phosphate solution is 1 mol / L and the pH is 6.0.

[0089] Using hydrogen peroxide as the oxidant, with a molar ratio of hydrogen peroxide to ferrous sulfate of 0.6:1, ammonium dihydrogen phosphate solution and hydrogen peroxide were added to the ferrous sulfate solution via a co-current feed method, followed by stirring at 30°C for 0.5 h. After the reaction was completed, the mixture was filtered and washed, with a final conductivity of over 5000 μS / cm, yielding amorphous ferric phosphate.

[0090] ② The above-mentioned amorphous ferric phosphate is mixed with pure water to make a slurry. The particle size of the slurry is controlled to be <150μm by a shear pump, and the solid content of the slurry is controlled to be 120g / L. Then, a crystallization aid is added and the slurry is aged.

[0091] The crystallization aid is a mixture of ammonium dihydrogen phosphate and ferrous sulfate. The molar ratio of phosphorus (P) to ferrous ions in the crystallization aid is 1:0.02. The amorphous ferric phosphate contains Fe... 3+ The molar ratio of phosphorus (P) in the crystallization aid was 1:0.56. Sulfuric acid solution was added to the reaction system to control the slurry pH to 0.8. The aging process involved stirring at 300 rpm at 80℃ for 2 hours. The slurry was then filtered and washed until the conductivity at the washing endpoint was above 1000 μS / cm. The sample was then dried at 120℃ for 6 hours to obtain ferric phosphate.

[0092] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the product prepared in Comparative Example 3 is an orthorhombic and monoclinic iron phosphate. Figure 6 This is a SEM image of the ferric phosphate prepared in Comparative Example 3, magnified 10,000 times. It shows thick flakes and spherical aggregates composed of flakes and granules, with an average primary particle size of 3 μm. The tap density of the ferric phosphate in Comparative Example 3 is 0.51 g / cm³. 3 .

[0093] The difference between Comparative Example 3 and Example 1 is that: in step ①, the washing process was not strictly controlled, resulting in a high level of residual soluble impurities in the amorphous ferric phosphate. This inadequate washing of the synthetic material led to the introduction of more impurities during the aging process. Residual ammonium and sulfate ions in the system participated in the aging and crystallization process, thus affecting the crystal structure after ferric phosphate crystallization. In step ②, the washing process was not controlled, posing a risk of impurity levels exceeding the standard.

[0094] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the crystallization aid in step ② is ammonium dihydrogen phosphate solution, and ferrous sulfate solution is not added to the crystallization aid.

[0095] The obtained product was subjected to SEM morphology observation, primary particle size measurement, and XRD testing. Figure 1 It can be seen that the product prepared in Comparative Example 4 is an orthogonal and monoclinic ferric phosphate. Figure 7 This is a SEM image of the ferric phosphate prepared in Comparative Example 4, magnified 10,000 times. It shows spherical aggregates composed of flakes and granules, with an average primary particle size of 3.2 μm. The tap density of the ferric phosphate in Comparative Example 4 is 0.49 g / cm³. 3 .

[0096] Application examples and application effect data Example 1 3. Comparative Example 1 The prepared ferric phosphate was calcined in a muffle furnace at 580℃ for 2 hours to remove the water of crystallization, yielding anhydrous ferric phosphate. Anhydrous ferric phosphate, lithium carbonate (Li to Fe molar ratio of 1.05:1), 8% sucrose (relative to the mass of ferric phosphate), and 6% PEG (relative to the mass of anhydrous ferric phosphate) were mixed in pure water to obtain a slurry. The slurry was dried using a spray granulation device to obtain a dry powder. Under nitrogen protection, the powder was sintered in a kiln at 750℃ for 6 hours. After cooling in the furnace, the sintered material was obtained. The sintered material was crushed, graded, and sieved to obtain lithium iron phosphate cathode material.

[0097] Method for detecting magnetic foreign matter in lithium iron phosphate cathode material: The sample is dispersed in ultrapure water medium, and the sample is rolled and adsorbed for 30 minutes using an adsorption magnetic rod with a magnetic field strength of 6000±500GS. After the surface material is washed off, the magnetic material on the adsorption magnetic rod is heated with nitric acid (1+1) and hydrochloric acid (1+1) to dissolve the magnetic material, causing it to fall off the magnetic rod and dissolve in the acid solution. The contents of iron, zinc, chromium and nickel in the sample solution are tested using ICP-OES, and the total content of these four elements is calculated.

[0098] The lithium iron phosphate cathode material prepared above was then assembled into a battery under the same conditions, specifically including: mixing the lithium iron phosphate cathode material with conductive carbon material and binder polyvinylidene chloride in a mass ratio of 90:5:5, and adding N2O2 dropwise. Methylpyrrolidone was ground into a paste and coated onto the surface of aluminum foil. After drying at 120°C, it was cut into sheets and then seamlessly rolled to obtain the positive electrode test electrode. The loading of active material on the positive electrode sheet was controlled at 9.5 mg, and the compaction density of the electrode sheet was controlled at 2.35-2.40 g / cm³. 2 The coin cell model is CR2032. The counter electrode (reference electrode) is a lithium metal sheet, and the electrolyte is a product of Shenzhen Capchem Technology Co., Ltd. The coin cells were assembled in a glove box with controlled moisture and oxygen levels. They were then placed in a 25°C constant temperature chamber for 24 hours before being connected to a blue-chip battery tester for charge-discharge testing. The coin cells were placed in a 25°C constant temperature chamber for charge-discharge testing. The nominal capacity at 1C was set at 170mAh / g. Within the range of 2.0-3.75V, the cells were first activated at 0.1C for one week, then charged and discharged at 1.0C. At a constant voltage cutoff current of 0.02C at 3.75V, the charge-discharge curves were observed.

[0099] The test results for the examples and comparative examples are shown in Table 1.

[0100] Table 1. Comparison of performance test results between the examples and comparative examples.

[0101] As shown in Table 1, the compaction density of the lithium iron phosphate cathode materials in Examples 1-3 is all higher than 2.6 g / cm³. 3 The 0.1C discharge capacity is ≥159 mAh / g, and the 1C discharge capacity is ≥142 mAh / g, which is significantly better than that of Comparative Examples 1-3. In addition, the magnetic material content of Examples 1-3 and Comparative Example 2 is significantly lower than that of Comparative Examples 1, 3, and 4. This is because the ferric phosphate phase in Examples 1-3 and Comparative Example 2 is pure phase orthorhombic ferric phosphate, while Comparative Examples 1, 3, and 4 contain monoclinic ferric phosphate phase in addition to orthorhombic ferric phosphate. Monoclinic ferric phosphate is prone to forming magnetic foreign matter such as iron phosphide (FeP, Fe2P) during high-temperature calcination.

[0102] The compaction density and discharge capacity at different rates of the lithium iron phosphate cathode materials in Comparative Examples 1, 3, and 4 are all lower than those in the Example. This may be because the products obtained in Comparative Examples 1 and 3-4 are all mixed-phase structures, containing orthorhombic and monoclinic phases. Figure 1 As shown in the figure, pure-phase orthorhombic iron phosphate was not successfully prepared, and the crystal size was not uniform, which affected the compaction performance and electrochemical performance of subsequent lithium iron phosphate materials.

[0103] Although orthorhombic iron phosphate was prepared in Comparative Example 2, the primary particle size was too large, at the micrometer level, which affected the compaction density of the lithium iron phosphate cathode material and the full utilization of its electrochemical performance.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0105] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing nano-sized orthogonal iron phosphate, characterized in that, include: The first ferrous salt solution was mixed with the first phosphorus source solution and the oxidant to carry out a co-precipitation reaction to obtain amorphous ferric phosphate; The amorphous ferric phosphate is mixed with water to form a slurry, the particle size of the slurry is adjusted, and then a crystallization aid is added to the slurry. The slurry is aged under stirring conditions with a pH of 0.8 to 1.5 to obtain nano-sized orthogonal ferric phosphate. The crystallization aid includes a second ferrous salt and a second phosphorus source.

2. The method for preparing nano-sized orthogonal iron phosphate according to claim 1, characterized in that, The first ferrous salt and the second ferrous salt are independently selected from at least one of ferrous sulfate, ferrous nitrate and ferrous chloride; And / or, the pH of the first ferrous salt solution is 2.0-3.0; And / or, the first phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; And / or, the pH of the first phosphorus source solution is 6-7; And / or, the molar ratio of the first ferrous salt to the first phosphorus source is (0.95~1.05):1; And / or, the molar ratio of the oxidant to the molar ratio of the first ferrous salt is (0.5 to 0.7):

1.

3. The method for preparing nano-sized orthogonal iron phosphate according to claim 2, characterized in that, The oxidant includes at least one of oxygen, ozone, hydrogen peroxide, and ammonium persulfate; And / or, mixing the first ferrous salt solution with the first phosphorus source solution and the oxidant includes: adding the first phosphorus source solution and the oxidant to the first ferrous salt solution in a co-current feeding manner.

4. The method for preparing nanoscale orthogonal iron phosphate according to any one of claims 1-3, characterized in that, The temperature of the coprecipitation reaction is 30–80°C, and the time of the coprecipitation reaction is 0.5–5 h. And / or, after the coprecipitation reaction is completed, the method further includes: performing a first solid-liquid separation and a first washing on the obtained precipitate in sequence, wherein the endpoint of the first washing is that the conductivity of the washing liquid is ≤2000μS / cm.

5. The method for preparing nano-sized orthogonal iron phosphate according to claim 1, characterized in that, The solid content of the slurry is 100–200 g / L; And / or, the control of slurry particle size includes: controlling the slurry particle size to <150 μm by using a shear pump.

6. The method for preparing nano-sized orthogonal iron phosphate according to claim 1, characterized in that, The second phosphorus source includes at least one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate. And / or, during aging, the method further includes adjusting the pH of the reaction system to 0.8–1.5 by adding a sulfuric acid solution.

7. The method for preparing nano-sized orthogonal iron phosphate according to claim 1, characterized in that, The ratio of the molar amount of phosphorus in the second phosphorus source to the molar amount of ferrous ions in the second ferrous salt is 1:(0.01-0.05). And / or, the ratio of the molar amount of iron in the amorphous iron phosphate to the molar amount of phosphorus in the second phosphorus source is 1:(0.1-2).

8. The method for preparing nanoscale orthogonal iron phosphate according to any one of claims 5-7, characterized in that, The aging temperature is 80-100℃; And / or, the aging time is 0.5-4 h; And / or, the stirring speed is 250-500 rpm; And / or, after aging is completed, the method further includes: sequentially performing a second solid-liquid separation, a second washing, and drying on the aged slurry, wherein the endpoint of the second washing is that the conductivity of the filtrate is ≤600μS / cm; And / or, the drying temperature is 80-120℃, and the drying time is 0.5-6h; And / or, the method further includes: recovering the aged mother liquor and reusing the recovered mother liquor as part of the crystallization aid.

9. A nanoscale orthogonal iron phosphate, characterized in that, The nano-sized orthogonal iron phosphate is prepared by the preparation method according to any one of claims 1-8; The primary particle size of the nano-sized orthogonal iron phosphate is 80-400 nm.

10. A method for preparing a lithium iron phosphate cathode material, characterized in that, include: The nano-sized orthogonal ferric phosphate described in claim 9 is calcined to obtain anhydrous ferric phosphate. The anhydrous iron phosphate was mixed with a lithium source, a carbon source and a solvent to obtain a mixed slurry; The mixed slurry is dried to obtain a dried material; The dried material is sintered to obtain lithium iron phosphate cathode material.

Images