Mesoporous-spiky spherical titanium-doped iron phosphate precursor, its preparation method and application

Abstract

This invention discloses a mesoporous-spiky spherical titanium-doped iron phosphate precursor, its preparation method, and its applications. The precursor is a mesoporous-spiky spherical multi-level structure formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles, with the general chemical formula Fe. 1‑x Ti x The precursor contains PO4 (x ranges from 0.009 to 0.015), and titanium is distributed in a gradient manner within the precursor. Titanium is significantly enriched at the tips of primary particles, while the titanium distribution is uniform in near-spherical secondary particles. A mesoporous-spiky spherical titanium-doped iron phosphate precursor is obtained through reduction acid leaching, purification, selective oxidation, and rapid temperature co-precipitation processes. This precursor is then mixed with a lithium source and a carbon source and subjected to liquid nitrogen freezing, vacuum freeze-drying, and sintering to obtain lithium iron phosphate. This invention, by constructing a mesoporous-spiky spherical multi-level structure and achieving a gradient distribution of titanium, yields a mesoporous-spiky spherical titanium-doped iron phosphate precursor, enabling the lithium iron phosphate cathode material to possess excellent low-temperature performance, high rate performance, and ultra-long cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to mesoporous-spiky spherical titanium-doped iron phosphate precursors, their preparation methods, and applications. Background Technology

[0002] Lithium iron phosphate (LiFePO4) cathode materials have been widely used in power batteries and large-scale energy storage due to their advantages such as high safety, long cycle life, and abundant raw material resources. However, their low electronic conductivity and ion diffusion coefficient, especially at low temperatures, significantly increase lithium-ion migration resistance, leading to a sharp decline in battery capacity and rate performance. This severely limits their application in low-temperature and high-power scenarios.

[0003] Existing technologies typically employ ion doping to optimize the electrochemical performance of lithium iron phosphate. Among these, titanium (Ti) doping is particularly effective due to the high efficiency of Ti doping. 4+ Introducing cation vacancies into the crystal lattice can help improve lithium-ion migration rates and has attracted much attention. However, in currently disclosed low-concentration titanium doping, there is too little Ti... 4+ The inability to form a continuous and efficient ion migration network in the lithium iron phosphate lattice results in insufficient cation vacancy concentration, limiting the improvement in electronic conductivity and ion diffusion capacity, and making it difficult to meet the stringent rate performance requirements of high-performance batteries. Therefore, researchers employ high-concentration titanium doping to further improve the electronic conductivity of the material. To achieve effective doping, introducing titanium at a high concentration (>3000 ppm) into the lithium iron phosphate precursor is a key technical challenge. However, when the titanium concentration in the liquid phase is too high, Ti... 4+ Under weakly acidic to near-neutral conditions, it readily undergoes hydrolysis to form Ti(OH)4 colloid. This colloid can clog reactors and pipelines, leading to production interruptions and uncontrolled coprecipitation reactions, making it impossible to obtain well-crystallized precursors. At the same time, high-concentration titanium-doped iron phosphate readily forms a dense structure, reducing ion transport efficiency. Furthermore, the efficiency of titanium dissolution in conventional titanium concentrate acid leaching solutions is extremely low, with a titanium dissolution rate of only 20-30%. Therefore, it is difficult to use titanium concentrate acid leaching solutions as raw materials for high-concentration titanium doping, requiring the use of external titanium sources, which greatly increases raw material costs.

[0004] Therefore, there is an urgent need in this field for a method that can achieve uniform and stable high-concentration titanium doping at low cost, so as to improve the electronic conductivity, ion diffusion rate and interface stability of lithium iron phosphate materials and promote the application of lithium iron phosphate materials in low-temperature environments. Summary of the Invention

[0005] In view of the above, the present invention provides a mesoporous-spiky spherical titanium-doped iron phosphate precursor, its preparation method and application, which can achieve uniform and stable high-concentration titanium doping under low cost, so as to improve the intrinsic conductivity, ion diffusion rate and interface stability of lithium iron phosphate materials, and promote the application of lithium iron phosphate materials in low-temperature environments.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] This invention provides a mesoporous-spiky spherical titanium-doped iron phosphate precursor, wherein the precursor is a mesoporous-spiky spherical hierarchical structure formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles, and its general chemical formula is Fe. 1-x Ti x The precursor contains PO4, where x is 0.009~0.015, and titanium exhibits a gradient distribution in the precursor particles. The titanium in the needle-shaped primary particles is significantly enriched at their tips, while the titanium concentration in the near-spherical secondary particles is uniformly distributed. The needle-shaped primary particles have a diameter of 50~100 nm and a length of 500~1000 nm. The particle size distribution D50 of the near-spherical secondary particles is 2.5~3.5 μm. Mesoporous channels are formed between adjacent needle-shaped primary particles in the precursor. The diameter of the mesoporous channels is 20~30 nm. The porosity of the mesoporous channels in the precursor is 35~45%. The specific surface area of ​​the precursor is 45~60 m². 2 / g; the titanium concentration at the tip of the needle-shaped primary particles is not less than 6000ppm; the titanium concentration of the near-spherical secondary particles is 3000~4000ppm; in the precursor, the molar ratio of iron to titanium is 70~110∶1.

[0008] It should be noted that the general chemical formula described in this invention is Fe. 1-x Ti x PO4, at its core, reflects the molar ratio of "Fe:Ti:P:O" rather than a precise single valence state; furthermore, the general formula omits the water of crystallization (the actual precursor expression is Fe). 1-x Ti x PO4·2H2O (co-precipitated), the core is to highlight the core composition ratio of Fe-Ti-PO, rather than denying the actual structure. As long as the core molar ratio Fe∶Ti∶P=(1-x)∶x∶1 remains unchanged, the precursor conforms to this general chemical formula.

[0009] In this invention, the molar ratio of iron to doped titanium in the iron phosphate precursor is 70-110:1, achieving effective high-concentration titanium doping. The precursor with a mesoporous-spiky spherical multi-level structure constructed in this invention features nanoscale needle-like primary particles that minimize the diffusion distance of lithium ions from the interior to the surface of the precursor particles, reducing the activation energy for lithium ion diffusion and enabling rapid migration of lithium ions even at low temperatures, thereby improving low-temperature capacity and rate performance. The mesoporous channels are intrinsic structures formed by the natural stacking of needle-like primary particles. Abundant mesoporous channels and a high specific surface area ensure that the electrolyte can fully wet the electrode material, providing ample liquid-phase transport channels for lithium ions and effectively compensating for slow solid-phase diffusion at low temperatures, thus improving the rate performance of the material. The spherical secondary particles are micron-sized particles assembled from nanoscale primary particles; this morphology is beneficial for high compaction density. Using the mesoporous-spiky spherical titanium-doped iron phosphate precursor provided in this invention as a precursor, lithium iron phosphate cathode materials with excellent low-temperature performance, high rate performance, and ultra-long cycle life can be prepared.

[0010] This invention provides a method for preparing a mesoporous, spiky, spherical titanium-doped iron phosphate precursor, which is carried out according to the following steps:

[0011] (1) Reduction acid leaching: After mixing titanium concentrate with hydrochloric acid solution, SO2 is introduced to carry out a reduction reaction, so that the titanium in the mineral phase is converted into Ti 3+ The titanium is dissolved in the form of solid-liquid separation to obtain an acid leaching solution with a titanium dissolution rate of greater than 80%.

[0012] (2) Purification and impurity removal: Add sulfuric acid solution with a mass fraction of 10-30% to the acid leaching solution to control SO4. 2- With Ca 2+ The molar ratio is 1.2~1.5∶1, and the mixture is stirred for 30 minutes to allow Ca to... 2+ CaSO4·2H2O precipitate is generated and removed by solid-liquid separation to obtain the first purified solution. Then, a 5-15% (w / w) ammonia solution is added to the first purified solution to adjust the pH to 3.5-4.0, and simultaneously 0.1-0.2 g / L citric acid is added. The mixture is stirred for 30-60 minutes to allow Al to precipitate. 3+ Cr 3+ Hydrolysis produces Al(OH)3 and Cr(OH)3 precipitates, which are removed by solid-liquid separation to obtain a second purified solution. Finally, the second purified solution is cooled to -10 to 0℃ and kept at this temperature for 1 to 3 hours to allow the Mg content in the solution to decrease. 2+ and Mn 2+ MgSO4·nH2O and MnSO4·nH2O crystals were generated, and a high-purity ferrous chloride solution with a titanium concentration of 3000~5000ppm and magnesium and manganese impurity concentrations of less than 100ppm was obtained by solid-liquid separation.

[0013] (3) Selective oxidation: Hydrogen peroxide solution is added to the high-purity ferrous chloride solution to carry out an oxidation reaction, thereby reducing the Ti content. 3+ Selective oxidation to Ti 4+ Among them, Ti 3+ To Ti 4+ The conversion rate is no less than 99%;

[0014] (4) Co-precipitation: The reactor is precooled to 0~10℃, and then the high-purity ferrous chloride solution is used as the iron source and titanium source. After being preheated to 70~90℃ with phosphoric acid, it is quickly injected into the precooled reactor. The supersaturation of more than 300% generated instantaneously is used to carry out the co-precipitation reaction to generate mesoporous-spiky spherical titanium-doped iron phosphate precursor.

[0015] Further, in step (1), the hydrochloric acid solution has a mass fraction of 15-25 wt%, the liquid-solid mass ratio of titanium concentrate to hydrochloric acid solution is 3.5-5.5:1, the SO2 introduction rate is 0.4-0.6 L / min, the reduction reaction temperature is 110-130℃, and the reaction time is 2-4 h. This step uses a 15-25 wt% hydrochloric acid solution and introduces SO2 reducing gas to dissolve the iron or titanium oxides in the titanium concentrate, thus reducing the Fe content. 2+ and Ti 3+ The ionic form of the substance enters the solution and maintains a strongly acidic environment, preventing Ti from entering the solution. 3+ A hydrolysis reaction occurs, ensuring a high titanium leaching rate and yielding an acid leaching solution with a titanium leaching rate greater than 80%. A titanium leaching rate greater than 80% guarantees sufficient titanium can be obtained directly from titanium concentrate without the need for purchasing titanium sources. This allows for the preparation of a high titanium concentration (3000~5000ppm) acid leaching solution at the lowest cost, providing raw materials for subsequent high-concentration titanium doping. After the reaction, solid-liquid separation is performed to remove insoluble substances (mainly SiO2 and unreacted minerals).

[0016] In this invention, step (2) aims to remove heavy metal impurities (such as Al) from the solution. 3+ Cr 3+ Mg 2+ Ca 2+ Mn 2+ (etc.) to create a pure reaction environment for subsequent high-concentration titanium targeted doping, ensuring high-purity titanium doping and electrochemical stability of lithium iron phosphate. ICP-OES analysis showed that the Ca in the first purification solution... 2+ The concentration was reduced to 200-300 ppm; Al in the second purification solution 3+ ≤20ppm, Cr 3+ ≤10ppm, Fe 2+ Retention rate ≥95%, Ti 3+ Retention rate > 90%; Mg in high-purity ferrous chloride solution 2+≤100ppm, Mn 2+ ≤100ppm. The SO4 supplied by the sulfuric acid (H2SO4) solution in this step. 2- Able to react with Ca in solution 2+ The reaction produces CaSO4 precipitate; the ammonia solution (NH3·H2O) provides OH-. - Able to react with Al in solution 3+ and Cr 3+ The reaction produces Al(OH)3 and Cr(OH)3 precipitates; citric acid can react with Ti 3+ Complexation prevents hydrolysis to form Ti(OH)3 or TiO(OH)2 precipitates, thus avoiding their consumption in subsequent solid-liquid separation operations. Finally, the solution is forcibly cooled to -10 to 0°C and held at this temperature through freeze crystallization, reducing the solubility of MgSO4 and MnSO4 below their precipitation points, allowing them to selectively crystallize as MgSO4·7H2O and MnSO4 crystals, which can then be completely removed by simple solid-liquid separation. This step, through chemical precipitation and freeze crystallization, reduces the impurity concentration to extremely low levels, ensuring the purity and effectiveness of subsequent high-concentration titanium doping. Furthermore, after cooling and crystallization, the concentrations of other impurities such as calcium (Ca) and aluminum (Al) in the solution are all below 50 ppm, and the total impurity concentration is below 200 ppm.

[0017] Furthermore, in step (3), the mass fraction of the hydrogen peroxide solution is 30%, and H2O2 and Ti 3+ The molar ratio is 1.1~1.3:1, the oxidation reaction temperature is 50~70℃, and the reaction time is 20~40 min. This step aims to remove Ti from the high-purity ferrous chloride solution. 3+ Convert to Ti 4+ Because H2O2 oxidizes Ti at temperatures of 50~70℃. 3+ The reaction rate is higher than that of Fe oxidation 2+ H2O2 will preferentially react with Ti at a speed of more than an order of magnitude faster. 3+ The reaction resulted in over 99% of the Ti in the solution being concentrated in the solution. 3+ Convert to Ti 4+ At the same time, avoid excessive oxidation of Fe by H2O2. 2+ This causes Fe in the solution 2+ It is not oxidized or is only slightly oxidized. If the oxidation reaction temperature is too low (<50℃), the oxidation reaction rate is too slow; if the temperature is too high (>70℃), it will accelerate the ineffective decomposition of H2O2 and Fe. 2+ Oxidation.

[0018] Further, in step (4), the mass fraction of phosphoric acid is 20-30%; the molar ratio of high-purity ferrous chloride solution to phosphoric acid in step (4) is (Fe+Ti):P = 1:1.0-1.05. In step (4) of this invention, co-precipitation occurs through a sudden temperature change, and the air environment promotes Fe... 2+ Oxidized to Fe 3+ Simultaneously, a supersaturation exceeding 300% is instantaneously triggered, inducing a "micro-burst crystallization effect," constructing a mesoporous-spiky spherical multi-level structure and achieving a gradient distribution of titanium, thus obtaining a mesoporous-spiky spherical titanium-doped iron phosphate precursor. The construction of the mesoporous-spiky spherical multi-level structure: On the one hand, when reactants at 70~90℃ are injected into a pre-cooled reactor (0~10℃), the solution temperature drops sharply, and FePO4 and Ti... 4+ The solubility of the hydrolysis products decreases sharply, and the instantaneous supersaturation exceeding 300% provides a huge driving force for crystallization, causing the solute to nucleate explosively and simultaneously at multiple sites in the system, forming a large number of crystal nuclei. These crystal nuclei rapidly aggregate and self-assemble to reduce surface energy, thereby forming uniformly sized spherical secondary particles; on the other hand, Ti 4+ Due to its higher charge and stronger hydrolysis tendency, Ti preferentially accumulates at the gas-liquid interface or the active tips of crystal growth. 4+ It can act as a "structure directing agent," guiding phosphate ions to grow rapidly and directionally along specific crystal planes, forming nanoscale needle-like primary particles (500~1000nm) on the surface of near-spherical secondary particles. The gaps between these needle-like primary particles naturally form mesoporous channels of 20~30nm. The gradient distribution of titanium: due to the... 4+ During the crystallization process, titanium accumulates at the growth interface (especially at the tips of needle-shaped primary particles), resulting in the highest titanium concentration at the tips of needle-shaped primary particles (>6000ppm), while the titanium distribution in spherical secondary particles is more uniform (3000~4000ppm).

[0019] This invention also provides the application of mesoporous-spiky spherical titanium-doped iron phosphate precursor in lithium iron phosphate cathode materials. The mesoporous-spiky spherical titanium-doped iron phosphate precursor, lithium source and carbon source are mixed, and the mixed material is then subjected to liquid nitrogen quick-freezing and vacuum freeze-drying. Finally, it is sintered under an inert atmosphere to obtain lithium iron phosphate cathode material.

[0020] Furthermore, the general chemical formula of the lithium iron phosphate cathode material is LiFe. 1-x Ti xPO4 / C, where x is 0.009~0.015; the lithium source is lithium carbonate or lithium hydroxide, and the carbon source is one or more of glucose, sucrose, citric acid, polyethylene glycol, ascorbic acid, or starch; the molar ratio of the lithium source to the iron source is Li∶Fe=1~1.04∶1; the amount of carbon source added is 8~15% of the total mass of the lithium source and iron source; the carbon source forms a uniform and dense thin coating layer on the surface of the lithium iron phosphate cathode material; the liquid nitrogen freezing conditions are: the mixed material is spread into a thin layer with a thickness of 3~10 mm. The material is rapidly frozen in a liquid nitrogen environment at -196℃ to -80℃ for 1 to 5 minutes to achieve instantaneous freezing. The conditions for vacuum freeze drying are: freezing temperature of -80℃ to -50℃, vacuum degree of less than 10Pa, and drying time of 12 to 36 hours. The conditions for sintering treatment are: heating to 650 to 750℃ at a heating rate of 1 to 3℃ / min under a nitrogen or argon atmosphere, and holding at this temperature for 10 to 14 hours. After 5000 cycles at -20℃ and 1C rate, the capacity retention rate of the lithium iron phosphate cathode material is not less than 80%.

[0021] In this invention, liquid nitrogen rapid freezing and vacuum freeze-drying are used to maintain the inherent mesoporous-spiky spherical titanium-doped iron phosphate structure, preventing precursor particle agglomeration and mesoporous structure collapse, and ensuring that the final lithium iron phosphate possesses the ion transport channels and high specific surface area of ​​the precursor. Through sintering under an inert atmosphere, mesoporous-spiky spherical titanium-doped iron phosphate (Fe...) is... 1-x Ti x PO4 reacts with a lithium source in a solid-state reaction to form titanium-doped lithium iron phosphate (LiFe). 1-x Ti x The lithium iron phosphate (LiFePO4 / C) material, after pyrolysis of the carbon source, forms a uniform and dense conductive carbon coating layer on the surface of the material, which greatly improves the electronic conductivity of the material. This results in the lithium iron phosphate material having excellent low-temperature performance, high rate performance, and ultra-long cycle life.

[0022] The technical solution of this application has at least the following beneficial effects:

[0023] This invention utilizes an SO2 reduction acid leaching process to increase the titanium leaching rate from titanium concentrate from 20-30% in traditional processes to over 80%, directly obtaining sufficient titanium from the concentrate without the need for an external titanium source. This significantly reduces raw material costs and makes high-concentration titanium doping economically feasible for industrial application. The titanium in the titanium concentrate is then treated with Ti... 3+ The form of dissolution and the preparation of the precursor via a temperature-change co-precipitation reaction avoids the Ti 4+In conventional co-precipitation, the formation of Ti(OH)4 colloids through hydrolysis easily leads to reactor blockage, ensuring the continuity and stability of the process. This invention addresses this issue by constructing a mesoporous-spiky spherical multi-level structure and achieving a gradient distribution of titanium through rapid temperature-change co-precipitation, resulting in a mesoporous-spiky spherical titanium-doped iron phosphate precursor. Using this precursor to prepare lithium iron phosphate cathode materials, liquid nitrogen rapid freezing-vacuum freeze-drying technology ensures that the lithium iron phosphate and the precursor have the same morphological and structural characteristics. Specifically, the nanoneedle-like primary particles and mesoporous channels significantly shorten the lithium-ion solid-phase diffusion distance, providing excellent electrolyte wetting channels; the near-spherical secondary particles give the material high compaction density and good electrode processing performance; and the gradient distribution of titanium, characterized by tip enrichment and uniform bulk distribution, improves intrinsic conductivity while forming a more stable interface. Thus, the synergistic effect of the mesoporous-spiky spherical multi-level structure and the gradient distribution of titanium enables the lithium iron phosphate cathode material to possess excellent low-temperature performance, high rate performance, and ultra-long cycle life. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention for preparing mesoporous-spiky spherical titanium-doped iron phosphate precursors.

[0025] Figure 2 This is a SEM image of the mesoporous-spiky spherical titanium-doped iron phosphate precursor of Embodiment 2 of the present invention.

[0026] Figure 3 a is a SEM image of needle-like primary particles in the mesoporous-spiky titanium-doped iron phosphate precursor of Example 2 of the present invention; Figure 3 b is an EDS diagram showing the Ti element distribution of needle-shaped primary particles in the mesoporous-spiky titanium-doped iron phosphate precursor of Example 2 of the present invention.

[0027] Figure 4 This is a SEM image of titanium-doped lithium iron phosphate in Example 2 of this invention. Detailed Implementation

[0028] The embodiments of this application will now be described in more detail. This application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to provide a more thorough and complete understanding of the application. It should be understood that the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0029] The term "comprising" as used in this application is an open-ended inclusion, meaning "including but not limited to". The term "according to" means "at least in part according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment". Definitions of other terms will be given in the description below.

[0030] Example 1: (Preparation of an iron phosphate precursor with a titanium concentration of 3065 ppm)

[0031] 1. The process flow diagram for the preparation of mesoporous-spiky spherical titanium-doped iron phosphate precursor is as follows: Figure 1 As shown, the specific steps include:

[0032] (1) Reduction Acid Leaching: Titanium concentrate and hydrochloric acid solution were mixed and then SO2 was introduced to carry out the reduction reaction. The mass fraction of hydrochloric acid solution was 15 wt%, the liquid-solid mass ratio of titanium concentrate to hydrochloric acid solution was 5.5:1, the SO2 introduction rate was 0.4 L / min, the reaction temperature of the reduction reaction was 110℃, and the reaction time was 2 h, so that the titanium in the mineral phase was converted into Ti 3+ The titanium concentrate is dissolved in the form of leaching, and after filtration, an acid leaching solution with a titanium dissolution rate of greater than 80% is obtained; wherein, the molar ratio of iron to titanium in the titanium concentrate is Fe∶Ti=0.9002;

[0033] (2) Purification and impurity removal: Add a 10% sulfuric acid solution to the acid leaching solution to control SO4 levels. 2- With Ca 2+ The molar ratio was 1.2:1, and the mixture was stirred for 30 minutes to allow Ca to... 2+ CaSO4·2H2O precipitate is generated and removed by solid-liquid separation to obtain the first purified solution. Then, a 5% (w / w) ammonia solution is added to the first purified solution to adjust the pH to 3.5, and 0.1 g / L citric acid is added simultaneously. The mixture is stirred for 30 minutes to allow Al to precipitate. 3+ Cr 3+ Hydrolysis produces Al(OH)3 and Cr(OH)3 precipitates, which are removed by solid-liquid separation to obtain a second purified solution. Finally, the second purified solution is cooled to 0℃ and kept at that temperature for 1 hour to allow the Mg content in the solution to decrease. 2+ and Mn 2+ MgSO4·nH2O and MnSO4·nH2O crystals were generated, and a high-purity ferrous chloride solution with a titanium concentration of 3227 ppm and magnesium and manganese impurity concentrations of less than 100 ppm was obtained by solid-liquid separation.

[0034] (3) Selective oxidation: Hydrogen peroxide solution was added to the obtained high-purity ferrous chloride solution to carry out the oxidation reaction. The mass fraction of the hydrogen peroxide solution was 30%. H2O2 reacted with Ti 3+ The molar ratio of Ti to Ti is 1.1:1, the reaction temperature of the oxidation reaction is 50℃, and the reaction time is 20 min. 3+ Selective oxidation to Ti 4+ Among them, Ti 3+ To Ti 4+ The conversion rate is no less than 99%;

[0035] (4) Co-precipitation: The reactor was precooled to 0°C. The obtained high-purity ferrous chloride solution was used as the iron and titanium source. After preheating to 70°C with 20% phosphoric acid, the molar ratio of high-purity ferrous chloride solution to phosphoric acid was (Fe+Ti):P=1:1. The solution was quickly injected into the precooled reactor. The co-precipitation reaction was carried out using the instantaneously generated supersaturation of over 300%. The titanium loss rate during the co-precipitation process was 5%±0.02%, generating a mesoporous-spiky titanium-doped iron phosphate precursor with a titanium doping concentration of 3065ppm. The titanium loss rate was calculated as (total mass of titanium in the high-purity ferrous chloride solution - total mass of titanium in the precursor) / total mass of titanium in the high-purity ferrous chloride solution × 100%, which was obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) to test the titanium concentration in the solution and the precursor.

[0036] The general chemical formula of the iron phosphate precursor prepared in this embodiment is Fe. 1-x Ti x PO4, x is approximately 0.0097. The x value is derived from the molar ratio of Fe to Ti in the precursor, x = Ti / (Fe+Ti), and calculated based on the titanium and iron concentrations in the precursor obtained from ICP-OES testing. The precursor is a mesoporous-spiky spherical multi-level structure formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles. The particle size of the spherical secondary particles, the diameter and length of the primary particles, the diameter of the mesoporous channels, and the porosity are shown in Table 1.

[0037] 2. Preparation of Titanium-Doped Lithium Iron Phosphate: The obtained mesoporous-spiky spherical titanium-doped lithium iron phosphate precursor, lithium source, and carbon source were mixed. The lithium source was lithium carbonate, and the carbon source was glucose. The molar ratio of lithium source to iron source was Li:Fe = 1:1. The amount of carbon source added was 8% of the total mass of lithium source and iron source. The mixed material was then spread into a thin layer with a thickness of 3 mm and rapidly frozen in a liquid nitrogen environment at -196℃ for 1 min to achieve instantaneous freezing. Vacuum freeze-drying was then performed at a freezing temperature of -80℃, a vacuum degree below 10 Pa, and a drying time of 12 h. Finally, under a nitrogen atmosphere, the temperature was raised to 650℃ at a heating rate of 1℃ / min and held at this temperature for 10 h for sintering to obtain the lithium iron phosphate cathode material. The general chemical formula of the lithium iron phosphate cathode material is LiFe. 1-x Ti x PO4 / C, where x is approximately 0.0097, the carbon source forms a uniform and dense thin coating layer on the surface of the lithium iron phosphate cathode material;

[0038] Example 2: (Preparation of an iron phosphate precursor with a titanium concentration of 3735 ppm)

[0039] 1. The process flow diagram for the preparation of mesoporous-spiky spherical titanium-doped iron phosphate precursor is as follows: Figure 1 As shown, the specific steps include:

[0040] (1) Reduction acid leaching: Titanium concentrate and hydrochloric acid solution are mixed and then SO2 is introduced to carry out the reduction reaction. The mass fraction of hydrochloric acid solution is 20wt%, the liquid-solid mass ratio of titanium concentrate to hydrochloric acid solution is 4.5∶1, the SO2 introduction rate is 0.5L / min, the reaction temperature of the reduction reaction is 120℃, and the reaction time is 3h, so that the titanium in the mineral phase is converted into Ti 3+ The titanium concentrate was dissolved in the form of leaching, and after filtration, an acid leaching solution with a titanium dissolution rate of greater than 80% was obtained; wherein, the molar ratio of iron to titanium in the titanium concentrate was Fe∶Ti=0.8917;

[0041] (2) Purification and impurity removal: Add a 20% sulfuric acid solution to the acid leaching solution to control SO4 levels. 2- With Ca 2+ The molar ratio was 1.3:1, and the mixture was stirred for 30 minutes to allow Ca to... 2+ CaSO4·2H2O precipitate is generated and removed by solid-liquid separation to obtain the first purified solution. Then, a 10% (w / w) ammonia solution is added to the first purified solution to adjust the pH to 3.7, and 0.15 g / L citric acid is added simultaneously. The mixture is stirred for 45 minutes to allow Al to precipitate. 3+ Cr 3+ Hydrolysis produces Al(OH)3 and Cr(OH)3 precipitates, which are removed by solid-liquid separation to obtain a second purified solution. Finally, the second purified solution is cooled to -5℃ and kept at that temperature for 2 hours to remove Mg from the solution. 2+ and Mn 2+ MgSO4·nH2O and MnSO4·nH2O crystals were generated, and a high-purity ferrous chloride solution with a titanium concentration of 3932 ppm and magnesium and manganese impurity concentrations of less than 100 ppm was obtained by solid-liquid separation.

[0042] (3) Selective oxidation: Hydrogen peroxide solution was added to the obtained high-purity ferrous chloride solution to carry out the oxidation reaction. The mass fraction of the hydrogen peroxide solution was 30%. H2O2 reacted with Ti 3+ The molar ratio of Ti to Ti is 1.2:1, the reaction temperature of the oxidation reaction is 60℃, and the reaction time is 30 min. 3+ Selective oxidation to Ti 4+ Among them, Ti 3+ To Ti 4+ The conversion rate is no less than 99%;

[0043] (4) Co-precipitation: The reactor was precooled to 5°C. The obtained high-purity ferrous chloride solution was used as the iron and titanium source. After preheating to 80°C with 25% phosphoric acid, the molar ratio of high-purity ferrous chloride solution to phosphoric acid was (Fe+Ti):P=1:1.02. The solution was quickly injected into the precooled reactor. The co-precipitation reaction was carried out using the instantaneously generated supersaturation of over 300%. The titanium loss rate during the co-precipitation process was 5%±0.02%, generating a mesoporous-spiky titanium-doped iron phosphate precursor with a titanium doping concentration of 3735ppm. The titanium loss rate was calculated as (total mass of titanium in the high-purity ferrous chloride solution - total mass of titanium in the precursor) / total mass of titanium in the high-purity ferrous chloride solution × 100%, which was obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) to test the titanium concentration in the solution and the precursor.

[0044] The general chemical formula of the iron phosphate precursor prepared in this embodiment is Fe. 1-x Ti x PO4, x is approximately 0.012. The x value is derived from the molar ratio of Fe to Ti in the precursor, x = Ti / (Fe+Ti), and calculated based on the titanium and iron concentrations in the precursor obtained from ICP-OES testing. The precursor is a mesoporous-spiky spherical multi-level structure formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles. The particle size of the spherical secondary particles, the diameter and length of the primary particles, the diameter of the mesoporous channels, and the porosity are shown in Table 1.

[0045] 2. Preparation of Titanium-Doped Lithium Iron Phosphate: The obtained mesoporous-spiky spherical titanium-doped lithium iron phosphate precursor, lithium source, and carbon source were mixed. The lithium source was lithium hydroxide, and the carbon source was sucrose. The molar ratio of lithium source to iron source was Li:Fe = 1.02:1. The amount of carbon source added was 12% of the total mass of lithium source and iron source. The mixed material was then spread into a thin layer with a thickness of 6 mm and rapidly frozen in a liquid nitrogen environment at -120℃ for 1-5 min to achieve instantaneous freezing. Vacuum freeze-drying was then performed at a freezing temperature of -60℃, a vacuum degree below 10 Pa, and a drying time of 24 h. Finally, under an argon atmosphere, the temperature was increased to 700℃ at a heating rate of 2℃ / min and held at this temperature for 12 h for sintering to obtain the lithium iron phosphate cathode material. The general chemical formula of the lithium iron phosphate cathode material is LiFe. 1-x Ti x PO4 / C, where x is approximately 0.012, the carbon source forms a uniform and dense thin coating layer on the surface of the lithium iron phosphate cathode material;

[0046] Example 3: (Preparation of an iron phosphate precursor with a titanium concentration of 4439 ppm)

[0047] 1. The process flow diagram for the preparation of mesoporous-spiky spherical titanium-doped iron phosphate precursor is as follows: Figure 1 As shown, the specific steps include:

[0048] (1) Reduction acid leaching: Titanium concentrate and hydrochloric acid solution are mixed and then SO2 is introduced to carry out the reduction reaction. The mass fraction of hydrochloric acid solution is 25wt%, the liquid-solid mass ratio of titanium concentrate to hydrochloric acid solution is 3.5:1, the SO2 introduction rate is 0.6L / min, the reaction temperature of the reduction reaction is 130℃, and the reaction time is 4h, so that the titanium in the mineral phase is converted into Ti 3+ The titanium concentrate was dissolved in the form of leaching and filtered to obtain an acid leaching solution with a titanium dissolution rate of greater than 80%; wherein, the molar ratio of iron to titanium in the titanium concentrate was Fe∶Ti=0.8718.

[0049] (2) Purification and impurity removal: Add a 30% sulfuric acid solution to the acid leaching solution to control SO4 levels. 2- With Ca 2+ The molar ratio was 1.5:1, and the mixture was stirred for 30 minutes to allow Ca to... 2+ CaSO4·2H2O precipitate is generated and removed by solid-liquid separation to obtain the first purified solution. Then, a 15% (w / w) ammonia solution is added to the first purified solution to adjust the pH to 4.0, and 0.2 g / L citric acid is added simultaneously. The mixture is stirred for 60 min to allow Al to precipitate. 3+ Cr 3+ Hydrolysis produces Al(OH)3 and Cr(OH)3 precipitates, which are removed by solid-liquid separation to obtain a second purified solution. Finally, the second purified solution is cooled to -10℃ and kept at that temperature for 3 hours to allow the Mg content in the solution to decrease. 2+ and Mn 2+ MgSO4·nH2O and MnSO4·nH2O crystals were generated, and a high-purity ferrous chloride solution with a titanium concentration of 4673 ppm and magnesium and manganese impurity concentrations of less than 100 ppm was obtained by solid-liquid separation.

[0050] (3) Selective oxidation: Hydrogen peroxide solution was added to the obtained high-purity ferrous chloride solution to carry out the oxidation reaction. The mass fraction of the hydrogen peroxide solution was 30%. H2O2 reacted with Ti 3+ The molar ratio of Ti to Ti is 1.3:1, the reaction temperature of the oxidation reaction is 70℃, and the reaction time is 40 min. 3+ Selective oxidation to Ti 4+ Among them, Ti 3+ To Ti 4+ The conversion rate is no less than 99%;

[0051] (4) Co-precipitation: The reactor was precooled to 10°C. The obtained high-purity ferrous chloride solution was used as the iron and titanium source. After preheating to 90°C with 30% phosphoric acid, the molar ratio of high-purity ferrous chloride solution to phosphoric acid was (Fe+Ti):P=1:1.05. The solution was quickly injected into the precooled reactor. The co-precipitation reaction was carried out using the instantaneous supersaturation of over 300%. The titanium loss rate during the co-precipitation process was 5%±0.02%, generating a mesoporous-spiky titanium-doped iron phosphate precursor with a titanium doping concentration of 4439ppm. The titanium loss rate was calculated as (total mass of titanium in the high-purity ferrous chloride solution - total mass of titanium in the precursor) / total mass of titanium in the high-purity ferrous chloride solution × 100%, which was obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) to test the titanium concentration in the solution and the precursor.

[0052] The general chemical formula of the iron phosphate precursor prepared in this embodiment is Fe. 1-x Ti x PO4, x is approximately 0.014. The x value is derived from the molar ratio of Fe to Ti in the precursor, x = Ti / (Fe + Ti), and calculated based on the titanium and iron concentrations in the precursor obtained from ICP-OES testing. This precursor is a mesoporous-spiky spherical multi-level structure formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles. The particle size of the spherical secondary particles, the diameter and length of the primary particles, the diameter of the mesoporous channels, and the porosity are shown in Table 1.

[0053] 2. Preparation of Titanium-Doped Lithium Iron Phosphate: The obtained mesoporous-spiky spherical titanium-doped lithium iron phosphate precursor, lithium source, and carbon source were mixed. The lithium source was lithium carbonate, and the carbon source was polyethylene glycol. The molar ratio of lithium source to iron source was Li:Fe = 1.04:1. The amount of carbon source added was 15% of the total mass of lithium source and iron source. The mixed material was then spread into a thin layer with a thickness of 10 mm and rapidly frozen in a liquid nitrogen environment at -80℃ for 5 min to achieve instantaneous freezing. Vacuum freeze-drying was then carried out at a freezing temperature of -50℃, a vacuum degree below 10 Pa, and a drying time of 36 h. Finally, under a nitrogen atmosphere, the temperature was raised to 750℃ at a heating rate of 3℃ / min and held at this temperature for 14 h for sintering to obtain the lithium iron phosphate cathode material. The general chemical formula of the lithium iron phosphate cathode material is LiFe. 1-x Ti x PO4 / C, where x is approximately 0.014, the carbon source forms a uniform and dense thin coating layer on the surface of the lithium iron phosphate cathode material;

[0054] Comparative Example 1: (Conventional acid leaching treatment)

[0055] 1. Preparation of titanium-doped iron phosphate precursor:

[0056] (1) Acid leaching treatment: Titanium concentrate was mixed with hydrochloric acid solution with a mass fraction of 20 wt% and a liquid-solid mass ratio of 4.5:1. No SO2 was introduced. The mixture was stirred at 120℃ for 3 h and filtered to obtain an acid leaching solution with a titanium dissolution rate of 28.5%. The molar ratio of iron to titanium in the titanium concentrate was Fe:Ti = 0.8976.

[0057] (2) Selective oxidation: Experimental conditions were the same as in Example 2;

[0058] (3) Freeze-crystallization for impurity removal: Experimental conditions are the same as in Example 2;

[0059] (4) Coprecipitation: The experimental conditions were the same as in Example 2, and a coprecipitation reaction was carried out to generate titanium-doped iron phosphate precursor.

[0060] The lithium iron phosphate precursor prepared by the above steps has no obvious spherical secondary particles, and the primary particles have an irregular morphology and no mesoporous structure.

[0061] 2. Preparation of titanium-doped lithium iron phosphate:

[0062] The obtained titanium-doped iron phosphate precursor, lithium source and carbon source were mixed. All subsequent steps, including liquid nitrogen quick-freezing, vacuum freeze drying, sintering treatment and other process parameters and raw material ratios, were completely consistent with those in Example 2.

[0063] Comparative Example 2: (Conventional coprecipitation reaction)

[0064] 1. Preparation of titanium-doped iron phosphate precursor:

[0065] (1) Reduction leaching: Experimental conditions are the same as in Example 2;

[0066] (2) Selective oxidation: Experimental conditions were the same as in Example 2;

[0067] (3) Freeze-crystallization for impurity removal: Experimental conditions are the same as in Example 2;

[0068] (4) Coprecipitation: The temperature change operation was eliminated, and the temperature of the reactor was kept constant at 60°C. Then, the obtained high-purity ferrous chloride solution was used as the iron source and titanium source, and added to the reactor in parallel flow with phosphoric acid at 60°C. The feeding time was controlled to be 1 hour, and a conventional coprecipitation reaction was carried out to generate titanium-doped iron phosphate precursor.

[0069] The lithium iron phosphate precursor prepared in the above steps has a spherical secondary particle distribution D50 of 4.0~5.0μm, and the primary particles are blocky with no needle-like structure and no obvious mesoporous channels.

[0070] 2. Preparation of titanium-doped lithium iron phosphate:

[0071] The obtained titanium-doped iron phosphate precursor, lithium source and carbon source were mixed. All subsequent steps, including liquid nitrogen quick-freezing, vacuum freeze drying, sintering treatment and other process parameters and raw material ratios, were completely consistent with those in Example 2.

[0072] Test methods: The elemental concentrations in the solutions and precursors of the examples and comparative examples were tested using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0073] The test results for titanium-doped iron phosphate precursors and lithium iron phosphate in Examples 1-3 and Comparative Examples 1-2 are shown in Tables 1 and 2, respectively. Figure 2 As shown, the iron phosphate precursor prepared in Example 2 has a clear mesoporous-spiky spherical hierarchical structure, which is formed by the self-assembly of needle-like primary particles on the surface of spherical secondary particles; as Figure 3 As shown, the needle-shaped primary particles in the iron phosphate precursor prepared in Example 2 clearly show Ti, Fe, and P elements distributed on their surface. This indicates that titanium was successfully doped into the iron phosphate precursor and effectively coexisted and distributed with Fe and P elements, thus proving that the mesoporous-spiky spherical titanium-doped iron phosphate precursor of this invention was successfully prepared. Further, Table 1 shows that the titanium concentrations of the mesoporous-spiky spherical titanium-doped iron phosphate precursors prepared in Examples 1, 2, and 3 are 3065 ppm, 3735 ppm, and 4439 ppm, respectively, showing a gradually increasing trend. Furthermore, the titanium concentration at the tips of the needle-shaped primary particles in the iron phosphate precursors of Examples 1, 2, and 3 is significantly higher than the titanium concentration in the spherical secondary particles. This indicates that the embodiments of this invention successfully obtained sufficient titanium from titanium concentrate to prepare a high-concentration titanium-doped iron phosphate precursor and achieved a gradient distribution of titanium elements in the precursor, exhibiting enrichment at the tips of primary particles and uniform distribution in the bulk phase. Figure 4 As shown, in Example 2, the lithium iron phosphate further prepared from the mesoporous-spiky spherical titanium-doped iron phosphate precursor consists of regular, dense spherical particles. It retains the spherical morphology of the precursor, has a uniform particle size distribution, and maintains a mesoporous structure on its surface, which is beneficial for electrolyte wetting and lithium-ion transport. Figure 2 The precursor structure is consistent.

[0074] As shown in Table 2, the 1C discharge ratio and 5C discharge ratio of the titanium-doped lithium iron phosphate in Example 1 at -20℃ were 142.6 mAh / g and 132.6 mAh / g, respectively; the 1C discharge ratio and 5C discharge ratio of the titanium-doped lithium iron phosphate in Example 2 at -20℃ were 142.9 mAh / g and 133 mAh / g, respectively; and the 1C discharge ratio and 5C discharge ratio of the titanium-doped lithium iron phosphate in Example 3 at -20℃ were 141.8 mAh / g and 131.6 mAh / g, respectively. This indicates that the titanium-doped lithium iron phosphate prepared in Examples 1-3 of this invention can still maintain excellent electrochemical performance at a low temperature of -20℃. This may be due to the mesoporous-spiky spherical multi-level structure and the gradient distribution of titanium elements, which give lithium iron phosphate better lithium-ion migration rate and structural stability under low temperature charge and discharge conditions.

[0075] As can be seen from Table 2, the titanium-doped lithium iron phosphate in Examples 1-3 maintained a capacity retention of over 80% after 5000 cycles at -20°C and 1C rate, indicating that the material has excellent cycling stability in low-temperature environments.

[0076] More importantly, as shown in Table 2, the compaction density, 1C discharge ratio, 5C discharge ratio, and capacity retention of the titanium-doped lithium iron phosphate in Examples 1-3 are significantly higher than those in Comparative Examples 1 and 2. This is because the mesoporous-spiky multi-level structure of the iron phosphate precursor in Examples 1-3 significantly improves the compaction density of lithium iron phosphate. The synergy between the nanoneedle-shaped primary particles and the mesoporous channels in the lithium iron phosphate prepared in Examples 1-3 greatly shortens the solid-phase diffusion distance of lithium ions and improves the ion migration rate, thereby achieving high rate performance of lithium iron phosphate. At the same time, the significant enrichment of titanium elements at the tips of primary particles and the uniform gradient distribution in the bulk phase of the lithium iron phosphate prepared in Examples 1-3 improves the interfacial stability of lithium iron phosphate, thereby improving the cycling stability of lithium iron phosphate in low-temperature environments. In Comparative Example 1, the titanium concentrate was treated with conventional acid leaching, but the dissolution rate of titanium was too low to achieve high titanium doping, and it was impossible to form a mesoporous-spiky spherical multi-level structure in subsequent steps. In Comparative Example 2, the conventional co-precipitation reaction resulted in the inability to form a micro-explosive crystallization effect with an instantaneous supersaturation of >300%, and it was impossible to prepare a precursor with a mesoporous-spiky spherical multi-level structure. As a result, the compaction density, rate performance, and low-temperature cycling stability of Comparative Example 1 and Comparative Example 2 were relatively low.

[0077] Table 1. Test results of titanium-doped iron phosphate precursors in different embodiments of the present invention.

[0078]

[0079] Table 2 Performance test results of titanium-doped lithium iron phosphate in different embodiments of the present invention

[0080]

[0081] Testing equipment:

[0082] Particle size distribution (D50): Laser particle size analyzer (Malvin Mastersizer 3000);

[0083] Primary particle size and mesopore size: Scanning electron microscope (SEM, Thermo Fisher Apreo2), transmission electron microscope (TEM, JEOL JEM-2100).

[0084] Porosity: The mesopore volume (Vp) is calculated using the nitrogen adsorption-desorption method (BET, Quantachrome Autosorb-iQ) through the BJH model, combined with the precursor true density (ρtrue, tested by helium displacement method) and bulk density (ρbulk), and is calculated according to the formula: Porosity = Vp × ρtrue / (1 / ρbulk) × 100%.

[0085] Element concentration: Inductively coupled plasma optical emission spectrometer (ICP-OES, Thermo Fisher iCAP 7600);

[0086] Compacted density: Powder tablet press (pressure 20MPa, holding pressure 30s);

[0087] Electrochemical performance: coin cell (CR2032), charge / discharge tester (Landian CT2001A).

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A mesoporous-spiky spherical titanium-doped iron phosphate precursor, characterized in that, The precursor is a mesoporous-spiked globular multi-level structure formed by self-assembly of needle-like primary particles on the surface of a quasi-spherical secondary particle, and has a chemical formula of Fe 1-x Ti x PO4, wherein x is 0.009-0.015, and the titanium element is distributed in a gradient in the precursor, the titanium element of the needle-like primary particles being significantly enriched at the tips thereof, and the titanium element of the quasi-spherical secondary particles being uniformly distributed.

2. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, The needle-shaped primary particles have a diameter of 50-100 nm and a length of 500-1000 nm.

3. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, The particle size distribution D50 of the spherical secondary particles is 2.5~3.5μm.

4. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1 or 2, characterized in that, Mesoporous channels are formed between adjacent needle-like primary particles in the precursor.

5. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1 or 4, characterized in that, The diameter of the mesoporous channel is 20~30nm.

6. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, 4, or 5, characterized in that, The porosity of the intermediate pore channel in the precursor is 35-45%.

7. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, The specific surface area of the precursor is 45-60 m 2 / g.

8. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, The titanium concentration at the tip of the needle-shaped primary particles is not less than 6000 ppm.

9. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, The titanium concentration of the spherical secondary particles is 3000~4000ppm.

10. The mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 1, characterized in that, In the precursor, the molar ratio of iron to titanium is 70~110:

1.

11. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to any one of claims 1 to 10, characterized in that, Follow these steps: (1) Reductive acid leaching: after mixing the titanium concentrate with hydrochloric acid solution, SO2 is introduced for reduction reaction, so that titanium in the mineral phase is dissolved in the form of Ti 3+ , and after solid-liquid separation, an acid leaching solution with titanium dissolution rate greater than 80% is obtained; (2) Purification and impurity removal: Add sulfuric acid solution with a mass fraction of 10-30% to the acid leaching solution to control SO4. 2- With Ca 2+ The molar ratio is 1.2~1.5∶1, and the mixture is stirred for 30 minutes to allow Ca to... 2+ CaSO4·2H2O precipitate is generated and removed by solid-liquid separation to obtain the first purified solution. Then, a 5-15% (w / w) ammonia solution is added to the first purified solution to adjust the pH to 3.5-4.0, and simultaneously 0.1-0.2 g / L citric acid is added. The mixture is stirred for 30-60 minutes to allow Al to precipitate. 3+ Cr 3+ Hydrolysis produces Al(OH)3 and Cr(OH)3 precipitates, which are removed by solid-liquid separation to obtain a second purified solution. Finally, the second purified solution is cooled to -10 to 0℃ and kept at this temperature for 1 to 3 hours to allow the Mg content in the solution to decrease. 2+ and Mn 2+ MgSO4·nH2O and MnSO4·nH2O crystals were generated, and a high-purity ferrous chloride solution with a titanium concentration of 3000~5000ppm and magnesium and manganese impurity concentrations of less than 100ppm was obtained by solid-liquid separation. (3) Selective oxidation: Hydrogen peroxide solution is added to the high-purity ferrous chloride solution to carry out an oxidation reaction, thereby reducing the Ti content. 3+ Selective oxidation to Ti 4+ Among them, Ti 3+ To Ti 4+ The conversion rate is no less than 99%; (4) Co-precipitation: The reactor is precooled to 0~10℃, and then the high-purity ferrous chloride solution is used as the iron source and titanium source. After being preheated to 70~90℃ with phosphoric acid, it is quickly injected into the reactor. The supersaturation of more than 300% generated instantaneously is used to carry out the co-precipitation reaction to generate mesoporous-spiky spherical titanium-doped iron phosphate precursor.

12. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, The hydrochloric acid solution in step (1) has a mass fraction of 15~25wt%.

13. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, In step (1), the liquid-solid mass ratio of titanium concentrate to hydrochloric acid solution is 3.5~5.5∶1.

14. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, In step (1), the SO2 introduction rate is 0.4~0.6 L / min.

15. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, The reduction reaction in step (1) is carried out at a temperature of 110-130°C for 2-4 hours.

16. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, The mass fraction of hydrogen peroxide solution in step (2) is 30%.

17. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, In step (2), H2O2 and Ti 3+ The molar ratio is 1.1~1.3∶1.

18. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, The oxidation reaction in step (2) is carried out at a temperature of 50-70°C for 20-40 minutes.

19. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, In step (4), the mass fraction of phosphoric acid is 20-30%.

20. The method for preparing the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 11, characterized in that, In step (4), the molar ratio of high-purity ferrous chloride solution to phosphoric acid is (Fe+Ti):P = 1:1.0~1.

05.

21. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor as described in any one of claims 1 to 10 in the preparation of lithium iron phosphate cathode materials, characterized in that, The mesoporous-spiky spherical titanium-doped iron phosphate precursor, lithium source, and carbon source are mixed, and then the mixed material is subjected to liquid nitrogen quick-freezing and vacuum freeze-drying. Finally, it is sintered under an inert atmosphere to obtain lithium iron phosphate cathode material.

22. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The general chemical formula of the lithium iron phosphate cathode material is LiFe. 1-x Ti x PO4 / C, where x is 0.009~0.

015.

23. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The lithium source is lithium carbonate or lithium hydroxide, and the carbon source is one or more of glucose, sucrose, citric acid, polyethylene glycol, ascorbic acid, or starch.

24. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The molar ratio of the lithium source to the iron source is Li:Fe = 1~1.04:

1.

25. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The amount of carbon source added is 8-15% of the total mass of lithium source and iron source; wherein, the carbon source forms a uniform and dense thin coating layer on the surface of the lithium iron phosphate cathode material.

26. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The conditions for liquid nitrogen freezing are as follows: the mixed material is spread into a thin layer with a thickness of 3~10mm, and then rapidly frozen in a liquid nitrogen environment of -196℃~-80℃ for 1~5min to make the material freeze instantly.

27. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The conditions for vacuum freeze drying are: freezing temperature of -80℃ to -50℃, vacuum degree of less than 10Pa, and drying time of 12 to 36 hours.

28. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The sintering conditions are as follows: under a nitrogen or argon atmosphere, the temperature is increased to 650-750°C at a heating rate of 1-3°C / min, and held at this temperature for 10-14 hours.

29. The application of the mesoporous-spiky spherical titanium-doped iron phosphate precursor according to claim 21 in lithium iron phosphate cathode materials, characterized in that, The lithium iron phosphate cathode material retains no less than 80% of its capacity after 5000 cycles at -20°C and 1C rate.

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