Phosphate positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion battery positive electrode materials, in particular to a phosphate positive electrode material and a preparation method and application thereof. The phosphate positive electrode material provided by the invention comprises first particles obtained from a precursor prepared by a solid-phase method and second particles obtained from a precursor prepared by a liquid-phase method, and the first particles and the second particles both contain rare earth doping elements. The first particles are large-particle-size particles and have good structural stability and mechanical strength, and the second particles are nanoscale small-particle-size particles, so that more uniform element distribution can be realized, and the reaction activity of the material is improved; through compounding of two kinds of particles and introduction of a rare earth doping element, the electronic structure and an ion diffusion channel of the material can be optimized, the conductivity and the lithium ion diffusion rate of the material can be enhanced, and lattice distortion can be inhibited, so that the overall electrochemical performance of the positive electrode material is improved, including improvement of the specific discharge capacity, the cycling stability, the rate capability and the like; the comprehensive performance of the lithium ion battery is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery cathode materials, and particularly relates to a phosphate-based cathode material and a preparation method and application thereof. BACKGROUND

[0002] With the vigorous development of the new energy automobile industry and the wide application of large-scale energy storage systems, the market puts forward more stringent requirements for the energy density, cycle life and safety performance of lithium ion batteries. As a core component of lithium ion batteries, the performance of cathode materials directly determines the comprehensive indicators such as the energy density and charge-discharge efficiency of the battery, and becomes a key factor restricting the breakthrough of lithium ion battery technology.

[0003] Among many cathode materials, lithium iron phosphate (LFP) has become one of the mainstream cathode materials in the field of power batteries due to its excellent thermal stability, long cycle life and low cost. However, there are two technical bottlenecks in traditional LFP materials. Firstly, due to the influence of its own olivine structure, the intrinsic electrical conductivity of LFP is low, which limits the transmission efficiency of lithium ions and electrons and results in poor rate performance of LFP batteries during high-current charge and discharge. Secondly, the volume energy density of traditional LFP materials is low, and the tap density of commercial lithium iron phosphate is usually only 1.0-1.4 g / cm 3 , and the electrode compaction density is generally lower than 2.6 g / cm 3 , which makes it difficult to break through 450 Wh / kg in terms of battery volume specific capacity. If the compaction density is simply increased, although the volume energy density can be improved to a certain extent, it will cause problems such as increased inter-particle contact resistance, deteriorated electronic conduction network, difficult electrolyte infiltration, blocked lithium ion transmission path, etc. At the same time, the accumulation of lattice stress will also cause particle breakage, which will greatly reduce the overall electrochemical performance of the battery.

[0004] Therefore, it is urgent to provide a new method for compounding large particle materials and small particle materials to solve the contradiction between capacity and performance when increasing the compaction density of traditional phosphate-based materials. SUMMARY

[0005] The application aims to provide a phosphate-based cathode material and a preparation method and application thereof, and aims to solve the problem that the phosphate-based cathode material prepared by a single preparation method and compounded with large particles and small particles in the prior art cannot simultaneously improve the compaction density and electrochemical performance.

[0006] To achieve the above application purposes, the technical solutions adopted by the application are as follows:

[0007] In a first aspect, the present application provides a phosphate-based positive electrode material, comprising: first phosphate-based particles obtained by preparing a precursor by a solid-phase method and second phosphate-based particles obtained by preparing a precursor by a liquid-phase method, wherein both the first phosphate-based particles and the second phosphate-based particles contain rare earth doping elements.

[0008] In some embodiments, the particle size of the phosphate-based first particles is 800-2000 nm.

[0009] In some embodiments, the particle size of the phosphate-based second particles is ≤100 nm.

[0010] In some embodiments, the mass ratio of the first phosphate-based particles to the second phosphate-based particles is (90-97):(3-10).

[0011] In some embodiments, the rare earth doping element includes at least one of lanthanum, cerium, and praseodymium.

[0012] In some embodiments, when the phosphate-based cathode material is lithium iron phosphate, the compaction density is 2.60-2.68 g / cm 3 The discharge capacity at 1C is ≥142mAh / g.

[0013] In a second aspect, the present application provides a method for preparing a phosphate-based positive electrode material, comprising the following steps:

[0014] A first phosphate-based precursor is prepared by a solid-phase method, and the first phosphate-based precursor is subjected to a first sintering treatment to obtain a first particle semi-finished product;

[0015] A second phosphate-based precursor is prepared by a liquid phase method, and the second phosphate-based precursor is subjected to a second sintering treatment to obtain a second particle semi-finished product;

[0016] The first semi-finished particle product, the second semi-finished particle product and a rare earth doping element are mixed and then calcined to obtain a phosphate-based positive electrode material.

[0017] In some embodiments, the step of preparing the first phosphate-based precursor by a solid-phase method includes: mixing at least iron phosphate, a carbon source, a lithium source, and a doping source, and then performing a drying process to obtain the first phosphate-based precursor.

[0018] In some embodiments, the step of preparing the phosphate-based second precursor by a liquid phase method includes: mixing at least a soluble lithium source, a soluble dopant source, a soluble phosphorus source, and a soluble iron source, then adding a carbon source, and drying to obtain the phosphate-based second precursor.

[0019] In some embodiments, the rare earth doping element is also included in the doping source and the soluble doping source, and the content of the rare earth doping element in the phosphate-based first precursor and the phosphate-based second precursor is the same.

[0020] In some embodiments, the step of mixing the first granular semi-product, the second granular semi-product and the rare earth doping element further includes adding a complementary doping source; the amount of the complementary doping source added is 300-2500 ppm, based on the total mass of the first granular semi-product and the second granular semi-product being 100%.

[0021] In some embodiments, the temperature of the first sintering treatment is 700-800℃, and the holding time is 4-8 hours.

[0022] In some embodiments, the temperature of the second sintering treatment is 680-720℃, and the holding time is 2-6 hours.

[0023] In some embodiments, the calcination treatment adopts a two-stage calcination treatment, wherein the temperature of the first calcination treatment is 700-780℃, and the time is 3-5 hours; the temperature of the second calcination treatment is 680-750℃, and the time is 3-7 hours.

[0024] In some embodiments, the mass ratio of the first granular semi-product to the second granular semi-product is (90-97) : (3-10).

[0025] In some embodiments, the doping amount of the rare earth doping element is 300-1000 ppm, based on the total mass of the first granular semi-product and the second granular semi-product being 100%.

[0026] In a third aspect, the embodiments of the present application provide a lithium ion battery, which comprises a positive electrode material, wherein the positive electrode material comprises the above phosphate-based positive electrode material or is prepared by the above preparation method of the phosphate-based positive electrode material.

[0027] The phosphate-based positive electrode material provided in the first aspect of the present application comprises first particles obtained from a precursor prepared by a solid phase method and second particles obtained from a precursor prepared by a liquid phase method, and both contain rare earth doping elements. The first particles are large-particle-size particles, have good structural stability and mechanical strength, can ensure that the positive electrode material maintains a stable crystal structure during the charging and discharging process, and reduces performance degradation caused by structural collapse; the second particles are nano-level small-particle-size particles, can realize more uniform element distribution, improve the reaction activity of the material, promote the rapid embedding and extraction of lithium ions, and improve the charging and discharging performance of the material; the combination of the two types of particles can balance high tap density and ion diffusion rate, and improve the energy density and rate performance of the positive electrode material; at the same time, the introduction of rare earth doping elements can optimize the electronic structure and ion diffusion channel of the material, enhance the electrical conductivity and lithium ion diffusion rate of the material, and inhibit lattice distortion, thereby improving the overall electrochemical performance of the positive electrode material, including improving the discharge specific capacity, cycle stability and rate performance, and effectively improving the comprehensive performance of the lithium ion battery.

[0028] The preparation method of the phosphate-based positive electrode material provided in the second aspect of the present application uses a solid phase method and a liquid phase method to prepare different precursors, respectively, to obtain particles with different characteristics, and then mixes and calcines them with rare earth doping elements; wherein the solid phase method is mature, simple to operate, and has low production cost, and can prepare first particle semi-products with stable structure and large particle size; the liquid phase method can realize uniform mixing of raw materials at the molecular or ionic level, accurately control the composition and structure of the precursor, and prepare nano-level second particle semi-products with good dispersibility and high reaction activity; by combining the two methods, their respective advantages are fully utilized, and rare earth elements are doped, to prepare phosphate-based positive electrode materials with excellent comprehensive performance. This preparation method has the advantages of strong process controllability, stable product performance, good repeatability, etc., is conducive to realizing large-scale industrial production, reducing production cost, and improving production efficiency.

[0029] The lithium ion battery provided in the third aspect of the present application uses the positive electrode material prepared by the above-mentioned phosphate-based positive electrode material or its preparation method, which can fully utilize the excellent performance of the positive electrode material. Due to the advantages of the positive electrode material such as high discharge specific capacity, good cycle stability and rate performance, the lithium ion battery has higher energy density, can store more electric energy, prolongs the use time of the battery, meets the needs of long-range electric vehicles, long-time work of portable electronic devices, etc.; at the same time, good cycle stability can reduce the performance degradation of the battery during the charging and discharging process, prolong the service life of the battery, and reduce the replacement cost and maintenance cost of the battery; excellent rate performance enables the battery to work normally under large-current charging and discharging conditions, meets the needs of application scenarios such as fast charging and high-power output, improves the practicability and applicability of the battery, and enhances the competitiveness of the lithium ion battery in the market. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0031] Figure 1 is a scanning electron microscope analysis diagram of the phosphate-based positive electrode material provided by Embodiment 1 of the present application.

[0032] Figure 2 is a scanning electron microscope analysis diagram of the phosphate-based positive electrode material provided by Embodiment 2 of the present application.

[0033] Figure 3 is a scanning electron microscope analysis diagram of the phosphate-based positive electrode material provided by Embodiment 3 of the present application.

[0034] Figure 4 is a scanning electron microscope analysis diagram of the phosphate-based second particles provided by Embodiment 1 of the present application. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0036] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0037] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0038] It should be understood that the magnitude of the serial number of each process described above in various embodiments of the present application does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0039] The terms used in the embodiments of the present application are merely for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0040] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0041] The terms "first", "second" are only for the purpose of description, used to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more of the features.

[0042] The first aspect of the embodiments of the present application provides a phosphate-based positive electrode material, which comprises: phosphate-based first particles obtained by preparing a precursor by a solid phase method and phosphate-based second particles obtained by preparing a precursor by a liquid phase method, wherein the phosphate-based first particles and the phosphate-based second particles both contain rare earth doping elements.

[0043] The phosphate-based positive electrode material provided by the first aspect of the embodiments of the present application comprises first particles obtained from a precursor prepared by a solid phase method and second particles obtained from a precursor prepared by a liquid phase method, and both contain rare earth doping elements. The first particles are large-diameter particles, have good structural stability and mechanical strength, can ensure that the positive electrode material maintains a stable crystal structure during charging and discharging, and reduces performance degradation caused by structural collapse; the second particles are nano-level particles, can realize more uniform element distribution, improve the reaction activity of the material, promote the rapid embedding and extraction of lithium ions, and improve the charging and discharging performance of the material; the combination of the two types of particles can balance high tap density and ion diffusion rate, and improve the energy density and rate performance of the positive electrode material; at the same time, the introduction of rare earth doping elements can optimize the electronic structure and ion diffusion channel of the material, enhance the electrical conductivity and lithium ion diffusion rate of the material, and inhibit lattice distortion, thereby improving the overall electrochemical performance of the positive electrode material, including improving the discharge specific capacity, cycle stability and rate performance, and effectively improving the comprehensive performance of the lithium ion battery.

[0044] In some embodiments, the particle size of the phosphate-based first particles is 800-2000 nm. The phosphate-based first particles are obtained from a precursor prepared by a solid phase method, and the particle size of the phosphate-based first particles is relatively large. The first particles with a larger particle size help to improve the tap density of the material, thereby improving the volume energy density of the battery and enabling the battery to store more electrical energy in a limited space. At the same time, a suitable particle size range can ensure good contact between particles and reduce the internal resistance of the material.

[0045] In some embodiments, the particle size of the phosphate-based second particles is ≤100 nm. The phosphate-based second particles are obtained from a precursor prepared by a liquid phase method, and the particle size of the phosphate-based second particles is relatively small. The particle size of the phosphate-based second particles is ≤100 nm, and the second particles with a small particle size can greatly increase the specific surface area of the material, provide more active sites, accelerate the diffusion and reaction kinetics process of lithium ions, and significantly improve the rate performance of the material, enabling the battery to maintain good performance under large-current charging and discharging conditions.

[0046] In some embodiments, the mass ratio of the phosphate-based first particles to the phosphate-based second particles is (90-97):(3-10). Limiting the mass ratio of the phosphate-based first particles to the phosphate-based second particles to (90-97):(3-10) can fully utilize the advantages of the particles obtained by the two preparation methods, on the basis of ensuring the structural stability and high tap density of the material, the reaction activity and rate performance of the material are enhanced by the appropriate amount of small-diameter second particles, the performance of the positive electrode material is optimized and balanced, and the comprehensive performance and practical application value of the battery are improved.

[0047] In some embodiments, the rare earth doping element includes at least one of lanthanum, cerium, and praseodymium. The rare earth doping element is selected from at least one of lanthanum, cerium, and praseodymium, which have special electronic layer structures and chemical properties. Lanthanum can improve the crystal structure of the material, enhance the stability of the material, inhibit the phase transition of the crystal structure during charging and discharging, thereby improving the cycle stability of the material; cerium has a variable oxidation state, can participate in redox reactions during charging and discharging, promote the insertion and extraction of lithium ions, and improve the specific capacity and rate performance of the material; praseodymium can optimize the electronic conductivity of the material, reduce the internal resistance of the material, accelerate the electron transport rate, and improve the overall electrochemical performance of the material. The use of different rare earth elements alone or in combination can optimize and improve the performance of the positive electrode material according to actual needs, meeting the performance requirements of lithium ion batteries in different application scenarios.

[0048] In some embodiments, when the phosphate-based positive electrode material is lithium iron phosphate, the compaction density is 2.60-2.68 g / cm 3 ; and the specific capacity under 1C condition is ≥ 142 mAh / g. The appropriate density helps to improve the volumetric energy density of the battery, so that the battery can accommodate more active substances under the same volume, thereby increasing the power storage capacity of the battery, meeting the application requirements of high-energy-density batteries, such as in electric vehicles, portable electronic devices, etc., effectively prolonging the endurance time of the equipment. Under 1C condition, the specific capacity is specified to be ≥ 142 mAh / g, and the higher specific capacity means that the positive electrode material can release more electrical energy, improve the energy output of the battery, directly improve the performance of the lithium ion battery, enhance the competitiveness of the battery in practical application, and meet the market demand for high-performance batteries.

[0049] The second aspect of the embodiments of the present application provides a preparation method of a phosphate-based positive electrode material, including the following steps:

[0050] S01. A phosphate-based first precursor is prepared by a solid-phase method, and the phosphate-based first precursor is subjected to first sintering treatment to obtain a first particle semi-finished product;

[0051] S02. A phosphate-based second precursor is prepared by a liquid-phase method, and the phosphate-based second precursor is subjected to second sintering treatment to obtain a second particle semi-finished product;

[0052] S03. The first particle semi-finished product, the second particle semi-finished product, and a rare earth doping element are mixed and subjected to calcination treatment to obtain a phosphate-based positive electrode material.

[0053] The preparation method of the phosphate-based positive electrode material provided in the second aspect of the embodiments of the present application uses solid-phase method and liquid-phase method to prepare different precursors, and then obtains two kinds of particles with different characteristics, and then mixes and calcines them with rare earth doping elements; wherein, the solid-phase method is mature in process, simple in operation, and low in production cost, and can prepare the first particle semi-finished product with stable structure and large particle size; the liquid-phase method can realize uniform mixing of raw materials at the molecular or ionic level, accurately control the composition and structure of the precursor, and prepare the second particle semi-finished product with good dispersibility and high reactivity; by combining the two methods, the advantages of each method are fully utilized, and the rare earth elements are doped to widen the lithium ion transmission channel, so that the phosphate-based positive electrode material with excellent comprehensive performance can be prepared. The preparation method has the advantages of strong process controllability, stable product performance, good repeatability, etc., is conducive to realizing large-scale industrial production, reducing production cost, and improving production efficiency.

[0054] In step S01, the phosphate-based first precursor is prepared by using the solid-phase method, and the phosphate-based first precursor is subjected to first sintering treatment to obtain the first particle semi-finished product. The solid-phase method for preparing the phosphate-based positive electrode material is a commonly used method in industry, and is especially suitable for large-scale production. The core is to make the raw materials uniformly mixed and form the target crystal structure through high-temperature solid-phase reaction.

[0055] In some embodiments, the tap density of the obtained first particle semi-finished product is > 2.55 g / cm3. 3 Under the condition of 1C, the discharge specific capacity is > 138 mAh / g.

[0056] In some embodiments, in the step of preparing the phosphate-based first precursor by using the solid-phase method, at least the iron phosphate, the carbon source, the lithium source and the doping source are mixed, and then subjected to drying treatment to obtain the phosphate-based first precursor.

[0057] In some embodiments, the molar ratio of the iron phosphate and the lithium source is (1:1)~(1:1.1).

[0058] In some embodiments, the total mass of the iron source is 100%, and the addition amount of the carbon source is 3wt%~15wt%. In some embodiments, the carbon source includes but is not limited to at least one of glucose, polyethylene glycol, sucrose, starch, lactic acid, methanol, ethanol, propanol, and butanol.

[0059] In some embodiments, the doping source includes but is not limited to a titanium source and a vanadium source; other types of transition metal elements can also be selected. In some specific embodiments, when the doping source is selected from a mixture of the titanium source and the vanadium source, the doping amount of the titanium source is 1500~7000 ppm, and the doping amount of the vanadium source is 300~3000 ppm.

[0060] In some embodiments, the lithium source includes, but is not limited to, at least one of lithium dihydrogen phosphate, lithium carbonate, lithium phosphate, lithium acetate, lithium hydroxide.

[0061] In some embodiments, the titanium source includes, but is not limited to, at least one of titanium dioxide, titanium sesquioxide, titanium trichloride, titanium fluoride, barium titanate, strontium titanate, phthalate.

[0062] In some embodiments, the vanadium source includes, but is not limited to, at least one of vanadium pentoxide, vanadium dioxide, divanadium trioxide, ammonium metavanadate, sodium vanadate, vanadium monoxide.

[0063] In some embodiments, after mixing the iron phosphate, the carbon source, the lithium source and the doping source, the mixing step is performed by using a sand mill, and then a spray drying process is performed.

[0064] Further, the phosphate-based first precursor is subjected to a first sintering process to obtain a first particle semi-product.

[0065] In some embodiments, the temperature of the first sintering process is 700-800°C, and the holding time is 4-8 hours. By controlling the temperature of the first sintering process to be 700-800°C and the holding time to be 4-8 hours, the phosphate-based first precursor can be fully reacted to form a stable crystal structure, ensuring that the first particle semi-product has good structural stability and mechanical strength, while avoiding problems such as excessive particle growth and grain coarsening caused by excessively high temperature or long time, which affect the performance of the material.

[0066] In step S02, the phosphate-based second precursor is prepared by a liquid phase method, and the phosphate-based second precursor is subjected to a second sintering process to obtain a second particle semi-product. The obtained second particle semi-product is a nano-sized small particle, and the proportion of small particles with a single particle size ≤100nm is 95% or more, and the 1C discharge specific capacity is >155mAh / g.

[0067] In some embodiments, in the step of preparing the phosphate-based second precursor by a liquid phase method, at least a soluble lithium source, a soluble doping source, a soluble phosphorus source, and a soluble iron source are mixed, and then a carbon source is added, and the phosphate-based second precursor is obtained by drying.

[0068] In the step of preparing the phosphate-based second precursor by a liquid phase method, the soluble lithium source is selected from the lithium sources with solubility in the raw materials prepared by the solid phase method described above; the soluble doping source is selected from the doping sources with solubility in the raw materials prepared by the solid phase method described above. The carbon source is selected from the carbon sources in the raw materials prepared by the solid phase method described above.

[0069] In some embodiments, the soluble phosphorus source and the soluble iron source are selected; wherein the phosphorus source includes but is not limited to (NH4)H2PO4, Na3PO4, and the like typical but non-limiting materials, and the iron source includes but is not limited to ferric chloride, ferric nitrate, and the like materials.

[0070] In some embodiments, after the raw materials are mixed in solution, a pre-sintering treatment is performed, and then the phosphated second precursor is obtained after separation and drying. The pre-sintering treatment is a low-temperature sintering treatment, and the specific steps include: treating at 380-450°C for 3-5 hours to remove volatile components.

[0071] Further, the phosphated second precursor is subjected to a second sintering treatment to obtain a second particle semi-finished product.

[0072] In some embodiments, the temperature of the second sintering treatment is 680-720°C, and the holding time is 2-6 hours. The second sintering treatment temperature is set to 680-720°C, and the holding time is 2-6 hours. Lower temperature and shorter time can prevent the second particles from excessive agglomeration and growth, maintain the advantages of small particle size, fully exert the characteristics of small particle size particles, such as large specific surface area and high reactivity, and improve the rate performance and charge-discharge efficiency of the material.

[0073] In some embodiments, the doping source and the soluble doping source further include a rare earth doping element, and the content of the rare earth doping element in the phosphated first precursor and the phosphated second precursor is the same.

[0074] In step S03, the first particle semi-finished product, the second particle semi-finished product, and the rare earth doping element are mixed and then subjected to a calcination treatment to obtain a phosphated positive electrode material.

[0075] In some embodiments, in the step of mixing the materials, the mixing method includes but is not limited to at least one of airflow mill mixing, soybean milk machine mixing, high-mixing machine mixing, double-cone mixing, drum mixing, plow blade mixing, mechanical grinding mixing, and nested mill mixing.

[0076] In some embodiments, the calcination treatment adopts a two-stage calcination treatment, wherein the temperature of the first calcination treatment is 700-780°C, and the holding time is 3-5 hours; the temperature of the second calcination treatment is 680-750°C, and the holding time is 3-7 hours. The total time of the calcination treatment adopted in the embodiments of the present application is 16-24 hours, which includes the heating stage, the holding stage, and the cooling stage of the first-stage calcination treatment, the holding stage of the second-stage calcination treatment, and the cooling stage after calcination.

[0077] The calcination method can optimize the material in stages. The first stage of calcination at a high temperature for a long time can promote the full reaction and fusion between different particles and rare earth elements, forming a stable composite structure. The second stage of calcination at a low temperature can fine-tune the material structure, eliminate internal stress, further improve the crystallinity and structural stability of the material, and help improve the overall compaction density and capacity of the compacted material, while inhibiting the generation of magnetic substances, so that the finally prepared positive electrode material has more excellent comprehensive performance.

[0078] In some embodiments, the temperature difference of the two-stage calcination process is generally 20-30℃.

[0079] In some embodiments, a small amount of a doping element (such as a vanadium source or a titanium source) can be added before the calcination process. Adding a small amount of a doping element is more conducive to lithium ion transmission and reduces the generation of magnetic substances during sintering. In some specific embodiments, if the added doping element is titanium, the amount of titanium added can be selected from 1000-2500 ppm; if the added doping element is vanadium, the amount of vanadium added can be selected from 300-1000 ppm.

[0080] In some embodiments, the mass ratio of the first particle semi-product and the second particle semi-product is (90-97) : (3-10). By limiting the mass ratio of the first particle semi-product and the second particle semi-product, the electrode compaction density and the electrochemical activity can be maximized.

[0081] In some embodiments, the total mass of the first particle semi-product and the second particle semi-product is 100%, and the doping amount of the rare earth doping element is 300-1000 ppm. Limiting the doping amount of the rare earth element can significantly improve the electrical conductivity and avoid phase separation caused by excessive doping.

[0082] In some specific embodiments, the obtained phosphate-based positive electrode material is doped with a rare earth element. The rare earth element can be added and mixed during the compounding of the "phosphate first particles and phosphate second particles", or the rare earth element can be added to the raw materials for preparing the first precursor and the second precursor to prepare them first, and then added again during the compounding of the "phosphate first particles and phosphate second particles".

[0083] The third aspect of the embodiments of the present application provides a lithium ion battery, which comprises a positive electrode material. The positive electrode material comprises the phosphate-based positive electrode material described above or is prepared by the preparation method of the phosphate-based positive electrode material described above.

[0084] The lithium-ion battery provided in the third aspect of the embodiment of the present application adopts the above-mentioned phosphate-based positive electrode material or the positive electrode material obtained by its preparation method, which can give full play to the excellent performance of the positive electrode material. Due to the advantages of the positive electrode material such as high discharge specific capacity, good cycle stability and rate performance, the lithium-ion battery has a higher energy density, can store more electrical energy, extend the battery life, and meet the needs of long-term battery life of electric vehicles and long-term operation of portable electronic devices; at the same time, good cycle stability can reduce the performance degradation of the battery during the charge and discharge process, extend the service life of the battery, and reduce the replacement cost and maintenance cost of the battery; the excellent rate performance enables the battery to work normally under high current charge and discharge conditions, meet the application scenario requirements of fast charging and high power output, improve the practicality and applicability of the battery, and enhance the competitiveness of the lithium-ion battery in the market.

[0085] The following describes the details in conjunction with specific embodiments.

[0086] Example A1

[0087] A phosphate-based positive electrode material

[0088] The phosphate-based positive electrode material includes: first phosphate-based particles obtained by preparing a precursor by a solid-phase method and second phosphate-based particles obtained by preparing a precursor by a liquid-phase method, wherein both the first phosphate-based particles and the second phosphate-based particles contain rare earth doping elements.

[0089] Preparation method:

[0090] 1. Preparation of the first semi-finished particle: 3000g of anhydrous ferric phosphate, 747g of lithium carbonate, 12g of TiO2, 4g of V2O5, 11g of lithium dihydrogen phosphate, and 275g of glucose were weighed and dissolved in water to a slurry solid content of 40%. After stirring evenly in a mixing bucket, sand milling was started, and the sand milling particle size was set to 0.36-0.40μm. After the sand milling particle size was qualified, spray drying was performed; the prepared spray-dried material was transferred to a graphite sagger and sintered in a high-pressure sand kiln at a sintering temperature of 780°C and a sintering time of 20h. After sintering, the material was transferred to a jet mill for pulverization at a pulverization frequency of 57Hz to obtain the first semi-finished particle; the specific particle size was 800-2000nm;

[0091] 2. Preparation of the second granular semi-finished product: 3000 g of liquid phase precursor, 30 g of sucrose, 60 g of citric acid, and 60 g of PEG were weighed respectively and dissolved in water to set the slurry solid content to 40%. After uniform stirring with a stirring barrel, sand milling was started. The sand milling particle size was set to 0.1-0.15 μm. After the sand milling particle size was qualified, spray drying was started. The spray-dried material was transferred to a graphite crucible and sintered in a high-sand kiln. The sintering temperature was set to 700°C, and the total sintering time was 13 h. After sintering, the material was transferred to an air jet mill for crushing. The crushing frequency was set to 57 Hz. The second granular semi-finished product was obtained, with a specific particle size of 50-100 nm.

[0092] 3. 1900 g of the first granular semi-finished product, 100 g of the second granular semi-finished product, 5.0 g of TiO2, and 2.5 g of lanthanum oxide were added to a high-speed mixer, which was set to rotate at 1300 r / min for 20 min. The mixed material was then transferred to a graphite crucible and calcined in a high-sand kiln. The first-stage high-temperature holding zone calcination temperature was set to 750°C, the second-stage high-temperature holding zone calcination temperature was set to 720°C, and the total calcination time was 20 h. After calcination, the material was transferred to an air jet mill for crushing. The crushing frequency was set to 55 Hz. The crushed material was the rare earth element-doped compounded small granular material for preparing high-pressure high-capacity phosphate-based positive electrode materials.

[0093] Example A2

[0094] A phosphate-based positive electrode material

[0095] The phosphate-based positive electrode material comprises a phosphate-based first granular material prepared by a solid phase method and a phosphate-based second granular material prepared by a liquid phase method. Both the phosphate-based first granular material and the phosphate-based second granular material contain rare earth doping elements.

[0096] Preparation method

[0097] 1. Preparation of the first granular semi-finished product: 3000 g of anhydrous iron phosphate, 745 g of lithium carbonate, 14 g of TiO2, 4 g of V2O5, 13 g of lithium dihydrogen phosphate, and 280 g of glucose were weighed respectively and dissolved in water to set the slurry solid content to 40%. After uniform stirring with a stirring barrel, sand milling was started. The sand milling particle size was set to 0.36-0.40 μm. After the sand milling particle size was qualified, spray drying was started. The spray-dried material was transferred to a graphite crucible and sintered in a high-sand kiln. The sintering temperature was set to 785°C, and the sintering time was 20 h. After sintering, the material was transferred to an air jet mill for crushing. The crushing frequency was set to 57 Hz. The first granular semi-finished product was obtained, with a specific particle size of 800-2000 nm.

[0098] 2. Preparation of the second granular semi-finished product: 3000 g of liquid phase precursor, 30 g of sucrose, 40 g of citric acid, 30 g of glucose, dissolved in water, respectively, set the slurry solid content to 40%, after uniform stirring with the stirring barrel, start sanding, set the sanding particle size to 0.1-0.15 μm, after the sanding particle size is qualified, spray drying can be started; the spray-dried material is transferred to a graphite crucible and sintered in a high-sand kiln, the sintering temperature is set to 720°C, the total sintering time is 14 h, after sintering, the material is transferred to an air jet mill for crushing, the crushing frequency is set to 57 Hz, and the second granular semi-finished product is obtained; the specific particle size is 50-100 nm;

[0099] 3. Take 1840 g of the first granular semi-finished product, 160 g of the second granular semi-finished product, 5.0 g of TiO2, and 1.25 g of cerium oxide, and add them to a high-speed mixer, set the rotation speed to 1300 r / min, and mix for 20 min; transfer all the mixed materials to a graphite crucible and calcine in a high-sand kiln, set the calcination temperature of the first high-temperature holding zone to 760°C, and the calcination temperature of the second high-temperature holding zone to 730°C, the total calcination time is 20 h; after discharging, the material is transferred to an air jet mill for crushing, the crushing frequency is set to 55 Hz; the crushed material is the rare earth element doped and compounded small particle preparation of high-pressure high-capacity phosphate-based positive electrode material.

[0100] Example A3

[0101] A phosphate-based positive electrode material

[0102] The phosphate-based positive electrode material comprises a phosphate-based first particle prepared by a solid phase method and a phosphate-based second particle prepared by a liquid phase method, wherein the phosphate-based first particle and the phosphate-based second particle both contain a rare earth doping element.

[0103] Preparation method:

[0104] 1. First granular semi-finished product: 3000 g of anhydrous iron phosphate, 745 g of lithium carbonate, 14 g of TiO2, 4 g of V2O5, 13 g of lithium dihydrogen phosphate, 280 g of glucose, dissolved in water, respectively, set the slurry solid content to 40%, after uniform stirring with the stirring barrel, start sanding, set the sanding particle size to 0.36-0.40 μm, after the sanding particle size is qualified, spray drying can be started; the spray-dried material is transferred to a graphite crucible and sintered in a high-sand kiln, the sintering temperature is set to 785°C, the sintering time is 20 h, after sintering, the material is transferred to an air jet mill for crushing, the crushing frequency is set to 57 Hz, and the first granular semi-finished product is obtained; the specific particle size is 800-2000 nm;

[0105] 2. Preparation of the second granular semi-finished product: ③ 3000 g of liquid phase precursor, 20 g of sucrose, 50 g of citric acid, 30 G peg, and 30 g of glucose were dissolved in water, the slurry solid content was set to 40%, and after uniform stirring with a stirring barrel, sand milling was started, the sand milling particle size was set to 0.1-0.12 μm, and after the sand milling particle size was qualified, spray drying was started; the spray-dried material was transferred to a graphite crucible and sintered in a high-sand kiln, the sintering temperature was set to 710°C, the sintering time was 13.5 h, and after sintering, the material was transferred to an air jet mill for crushing, the crushing frequency was set to 57 Hz, and the second granular semi-finished product was obtained; the specific particle size was 50-100 nm;

[0106] 3. 1840 g of the first granular semi-finished product, 160 g of the second granular semi-finished product, 5.0 g of TiO2, and 1.25 g of cerium oxide were added to a high-speed mixer, the rotation speed was set to 1300 r / min, and the mixing time was 20 min; the mixed material was transferred to a graphite crucible and calcined in a high-sand kiln, the first-stage high-temperature holding zone calcination temperature was set to 760°C, the second-stage high-temperature holding zone calcination temperature was set to 730°C, and the total calcination time was 20 h; after calcination, the material was transferred to an air jet mill for crushing, the crushing frequency was set to 55 Hz, and the crushed material was the rare earth element-doped compounded small granular high-pressure compact high-capacity phosphate-based positive electrode material.

[0107] Comparative Example A1

[0108] A phosphate-based positive electrode material

[0109] The phosphate-based positive electrode material comprises a phosphate-based first granule and a phosphate-based second granule, wherein the phosphate-based first granule and the phosphate-based second granule are both prepared by a solid phase method, and the particle size is adjusted by sand milling post-processing, and the phosphate-based first granule and the phosphate-based second granule both contain rare earth doping elements.

[0110] Preparation method:

[0111] 1. Preparation of the first granular semi-finished product: 3000 g of anhydrous iron phosphate, 747 g of lithium carbonate, 12 g of TiO2, 4 g of V2O5, 11 g of lithium dihydrogen phosphate, and 275 g of glucose were dissolved in water, the slurry solid content was set to 40%, and after uniform stirring with a stirring barrel, sand milling was started, the sand milling particle size was set to 0.36-0.40 μm, and after the sand milling particle size was qualified, spray drying was started; the spray-dried material was transferred to a graphite crucible and sintered in a high-sand kiln, the sintering temperature was set to 780°C, the sintering time was 20 h, and after sintering, the material was transferred to an air jet mill for crushing, the crushing frequency was set to 57 Hz, and the first granular semi-finished product was obtained; the specific particle size was 800-2000 nm;

[0112] 2. Preparation of a second semi-finished particle: Grinding the first semi-finished particle to obtain a second semi-finished particle with a small particle size, specifically 50-100 nm;

[0113] 3. Take 1840g of the first semi-finished product, 160g of the second semi-finished product, 5.0g of TiO2, and 1.25g of cerium oxide, and add them together to a high-speed mixer, set the speed to 1300r / min, and the high-speed mixing time to 20min; transfer all the mixed materials to a graphite sagger and place them in a high-sand kiln for calcination, set the calcination temperature of the first high-temperature insulation zone of the kiln to 760℃, and the calcination temperature of the second high-temperature insulation zone to 730℃, and the total calcination time is 20h; after discharging, the material can be transferred to a jet mill for crushing, and the crushing frequency is set to 55Hz; the crushed material obtained is the rare earth element-doped composite small particles for preparing high-density and high-capacity phosphate-based positive electrode materials.

[0114] Comparative Example A2

[0115] A phosphate-based positive electrode material

[0116] The phosphate-based positive electrode material includes first phosphate-based particles and second phosphate-based particles, wherein the first phosphate-based particles and the second phosphate-based particles are both prepared by a liquid phase method, and both the first phosphate-based particles and the second phosphate-based particles contain rare earth doping elements.

[0117] Preparation method:

[0118] 1. Preparation of the first semi-finished particle: 3000g of liquid precursor, 30g of sucrose, 60g of citric acid, and 60g of PEG were weighed and dissolved in water to a slurry solid content of 40%. After stirring evenly in a mixing bucket, sand milling was started, and the sand milling particle size was set to 0.1-0.15μm. After the sand milling particle size was qualified, spray drying was performed. The spray-dried material was transferred to a graphite sagger and sintered in a high-pressure sand kiln at a sintering temperature of 700°C for a total sintering time of 13 hours. After sintering, the material was transferred to a jet mill for pulverization at a pulverization frequency of 57Hz to obtain the first semi-finished particle with a specific particle size of 800-2000nm.

[0119] 2. Preparation of a second semi-finished particle: Grinding the first semi-finished particle to obtain a second semi-finished particle with a small particle size, specifically 50-100 nm;

[0120] 3. Take 1840g of the first granular semi-finished product, 160g of the second granular semi-finished product, 5.0g of TiO2, and 1.25g of cerium oxide, and add them into a high-speed mixer, set the rotating speed to 1300r / min, and high-mix for 20min; transfer all the mixed materials into a graphite crucible, and place the crucible in a high-sand kiln for calcination, set the calcination temperature of the first high-temperature holding zone to 760℃, the calcination temperature of the second high-temperature holding zone to 730℃, and the total calcination time to 20h; after discharging, transfer the material to a jet mill for crushing, and set the crushing frequency to 55Hz; the crushed material obtained is a rare earth element doped and compounded small granular phosphate-based positive electrode material with high compaction and high capacity.

[0121] Comparative Example A3

[0122] A phosphate-based positive electrode material

[0123] The phosphate-based positive electrode material comprises phosphate-based first particles and phosphate-based second particles, wherein the phosphate-based first particles are prepared by a solid-phase method, and the phosphate-based second particles are all prepared by a liquid-phase method.

[0124] Preparation method:

[0125] 1. Prepare the first granular semi-finished product: respectively weigh 3000g of anhydrous iron phosphate, 745g of lithium carbonate, 14g of TiO2, 4g of V2O5, 13g of lithium dihydrogen phosphate, and 280g of glucose, and dissolve them in water, set the solid content of the slurry to 40%, and then start sand milling after uniformly stirring the slurry using a stirring barrel; set the sand milling particle size to 0.36-0.40μm, and then transfer the material to a jet mill for crushing after the sand milling particle size is qualified; set the crushing frequency to 57Hz. Z ;

[0126] 2. Prepare the second granular semi-finished product: respectively weigh 3000g of a liquid-phase precursor, 30g of sucrose, 60g of citric acid, and 60g of PEG, and dissolve them in water, set the solid content of the slurry to 40%, and then start sand milling after uniformly stirring the slurry using a stirring barrel; set the sand milling particle size to 0.1-0.15μm, and then transfer the material to a jet mill for crushing after the sand milling particle size is qualified; set the crushing frequency to 57Hz.

[0127] 3. Take 1840 g of the first particle semi-finished product, 160 g of the second particle semi-finished product, and 5.0 g of TiO2, and add them into a high-speed mixer, set the rotating speed to 1300 r / min, and high-speed mix for 20 min; transfer all the high-speed mixed material into a graphite crucible, and place the graphite crucible in a high-sand kiln to sinter, set the sintering temperature of the first high-temperature holding zone to 760 DEG C, set the sintering temperature of the second high-temperature holding zone to 730 DEG C, and set the total sintering time to 20 h.

[0128] Comparative Example A4

[0129] A phosphate-based positive electrode material

[0130] The phosphate-based positive electrode material includes phosphate-based first particles, wherein the phosphate-based first particles are prepared by a solid-phase method.

[0131] Preparation method:

[0132] 1. Prepare a first particle precursor: weigh 3000 g of anhydrous iron phosphate, 745 g of lithium carbonate, 14 g of TiO2, 4 g of V2O5, 13 g of lithium dihydrogen phosphate, and 280 g of glucose, respectively, dissolve them in water, set the solid content of the slurry to 40%, and then start sanding after uniform stirring by using a stirring barrel; set the sanding particle size to 0.36-0.40 μm, and then transfer to spray drying after the sanding particle size is qualified; transfer the spray-dried material to a graphite crucible, place the graphite crucible in a high-sand kiln to sinter, set the sintering temperature to 785 DEG C, set the sintering time to 20 h, transfer to a jet mill for crushing after sintering, and set the crushing frequency to 57 Hz;

[0133] 3. Take 2000 g of the first particle precursor, 5.0 g of TiO2, and 1.25 g of cerium oxide, and add them into a high-speed mixer, set the rotating speed to 1300 r / min, and high-speed mix for 20 min; transfer all the high-speed mixed material into a graphite crucible, and place the graphite crucible in a high-sand kiln to sinter, set the sintering temperature of the first high-temperature holding zone to 760 DEG C, set the sintering temperature of the second high-temperature holding zone to 730 DEG C, and set the total sintering time to 20 h.

[0134] Examples B1-B3 and Comparative Examples B1-B4

[0135] A lithium ion battery

[0136] Each lithium ion battery is assembled according to the following method:

[0137] 1. The phosphate-based positive electrode material obtained in Examples A1-A3 and Comparative Examples A1-A4 is used as the positive electrode material. The positive electrode material, Super P conductive agent, PVDF binder, and positive electrode lithium supplement additive are mixed in a specific mass ratio (8:1:1:1) in an appropriate amount of NMP to prepare a positive electrode slurry. Subsequently, the positive electrode slurry is subjected to the processes of homogenization, coating, drying, and cutting to complete the production of the positive electrode sheet. Finally, the positive electrode sheet is placed in a vacuum oven at 100°C to remove residual moisture.

[0138] 2. Negative electrode sheet: lithium sheet.

[0139] 3. Separator: polyethylene (PE) separator is used.

[0140] 4. Electrolyte: the electrolyte is a 1 mol / L LiPF6 solution, and the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1.

[0141] 5. Assembly of secondary battery:

[0142] The above positive electrode sheet, metal lithium lithium sheet, electrolyte, and separator are assembled into a lithium ion battery according to the assembly requirements of the lithium ion battery.

[0143] Performance test

[0144] (I) The phosphate-based positive electrode material obtained in Examples A1-A3 and Comparative Examples A1-A4 is subjected to the following performance tests. The specific test methods include:

[0145] 1. Specific surface area: tested by N adsorption method.

[0146] 2. Compaction density: tested by a compaction machine, and the test pressure is 3 tons.

[0147] 3. Scanning electron microscope analysis of the obtained material

[0148] (II) The lithium ion batteries of each example and comparative example are subjected to the following performance tests. The specific test methods are as follows:

[0149] 1. Charge-discharge capacity retention rate: tested by a blue electric test system.

[0150] 2. 3.2V interval capacity ratio: tested by a blue electric test system.

[0151] Result analysis

[0152] (I) The results of the performance tests of the phosphate-based positive electrode material obtained in Examples A1-A3 and Comparative Examples A1-A4 are shown in Tables 1 and 2. It can be seen that,

[0153] Table 1

[0154]

[0155] Table 2

[0156]

[0157] According to Table 1 and Table 2, it can be found that the examples (1-3) are superior to the comparative examples in terms of key parameters such as pH value (9.20-10.14), carbon content (1.31%-1.61%), resistivity (11.3-25.4 Ω·cm), particle size D50 (0.81-0.97 μm), and compacted density (2.606-2.634 g / cm 3 Among them, example 3 (pH = 9.86, C% = 1.31%, D50 = 0.84 μm) has the best overall performance, with a 1C discharge capacity of 143.0 mAh / g and a 3.2V discharge platform ratio as high as 91.25%, which is significantly higher than that of the comparative examples (135.26-141.33 mAh / g, 87.93%-88.35%).

[0158] It can be seen that the phosphate-based positive electrode material provided by the embodiments of the present application comprises first particles obtained from a precursor prepared by a solid phase method and second particles obtained from a precursor prepared by a liquid phase method, and both contain rare earth doping elements. The first particles are large-particle-size particles, which have good structural stability and mechanical strength, can ensure that the positive electrode material maintains a stable crystal structure during charging and discharging, and reduces performance degradation caused by structural collapse; the second particles are nano-particles, which can achieve more uniform element distribution, improve the reaction activity of the material, promote the rapid embedding and extraction of lithium ions, and improve the charging and discharging performance of the material; the combination of the two types of particles can balance high tap density and ion diffusion rate, and improve the energy density and rate performance of the positive electrode material; at the same time, the introduction of rare earth doping elements can optimize the electronic structure and ion diffusion channel of the material, enhance the electrical conductivity and lithium ion diffusion rate of the material, and inhibit lattice distortion, thereby improving the overall electrochemical performance of the positive electrode material, including improving the discharge specific capacity, cycle stability, and rate performance, and effectively improving the comprehensive performance of the lithium ion battery.

[0159] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phosphate-based cathode material, characterized in that: The phosphate-based positive electrode material includes: first phosphate-based particles obtained by preparing a precursor through a solid-phase method and second phosphate-based particles obtained by preparing a precursor through a liquid-phase method, wherein both the first phosphate-based particles and the second phosphate-based particles contain rare earth doping elements.

2. The phosphate-based cathode material according to claim 1, wherein The particle size of the first phosphate particles is 800-2000 nm; and / or, The particle size of the second phosphate-based particles is ≤100 nm; and / or, The mass ratio of the first phosphate-based particles to the second phosphate-based particles is (90-97):(3-10).

3. The phosphate-based positive electrode material according to claim 1 or 2, characterized in that: The rare earth doping element includes at least one of lanthanum, cerium, and praseodymium.

4. The phosphate-based positive electrode material according to claim 1 or 2, characterized in that: When the phosphate-based cathode material is lithium iron phosphate, the compaction density is 2.60-2.68 g / cm 3 ; Discharge capacity at 1C is ≥142mAh / g.

5. A method for preparing a phosphate-based positive electrode material, characterized in that: The steps include: A first phosphate-based precursor is prepared by a solid-phase method, and the first phosphate-based precursor is subjected to a first sintering treatment to obtain a first particle semi-finished product; A second phosphate-based precursor is prepared by a liquid phase method, and the second phosphate-based precursor is subjected to a second sintering treatment to obtain a second particle semi-finished product; The first semi-finished particle product, the second semi-finished particle product and a rare earth doping element are mixed and then calcined to obtain a phosphate-based positive electrode material.

6. The method for preparing a phosphate-based cathode material according to claim 5, wherein: The step of preparing the first phosphate precursor by a solid phase method includes: mixing at least iron phosphate, a carbon source, a lithium source and a doping source, and then drying to obtain the first phosphate precursor; and / or, The steps of preparing the second phosphate precursor by liquid phase method include: mixing at least a soluble lithium source, a soluble doping source, a soluble phosphorus source, and a soluble iron source, adding a carbon source, and drying to obtain the second phosphate precursor.

7. The method for preparing a phosphate-based cathode material according to claim 6, wherein: The doping source and the soluble doping source further include the rare earth doping element, and the content of the rare earth doping element in the first phosphate-based precursor and the second phosphate-based precursor is the same; and / or, The step of mixing the first semi-finished particle, the second semi-finished particle and the rare earth doping element also includes adding a supplementary doping source; taking the total mass of the first semi-finished particle and the second semi-finished particle as 100%, the added amount of the supplementary doping source is 300 to 2500 ppm.

8. The method for preparing a phosphate-based cathode material according to claim 5, wherein: The temperature of the first sintering treatment is 700-800° C. and the holding time is 4-8 hours; and / or, The temperature of the second sintering treatment is 680-720° C. and the holding time is 2-6 hours; and / or, The calcination treatment adopts a two-stage calcination treatment, wherein the temperature of the first calcination treatment is 700-780°C and the holding time is 3-5 hours; the temperature of the second calcination treatment is 680-750°C and the holding time is 3-7 hours.

9. The method for preparing a phosphate-based cathode material according to claim 5, wherein: The mass ratio of the first semi-finished particle product to the second semi-finished particle product is (90-97): (3-10); and / or, Taking the total mass of the first semi-finished particle product and the second semi-finished particle product as 100%, the doping amount of the rare earth doping element is 300 to 1000 ppm.

10. A lithium ion battery, characterized in that: The lithium-ion battery includes a positive electrode material, wherein the positive electrode material includes the phosphate-based positive electrode material according to any one of claims 1 to 4 or is prepared by the method for preparing the phosphate-based positive electrode material according to any one of claims 5 to 9.

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