Preparation method of carbon nanotube network reinforced lithium iron phosphate positive electrode material

Abstract

The application relates to a preparation method of a carbon nanotube network reinforced lithium iron phosphate positive electrode material, and the lithium iron phosphate positive electrode material core has an olivine structure with a chemical formula of LiFe1-x-y-zMgxMnyVzPO4, wherein 0.04<=x<=0.06, 0.02<=y<=0.04, and 0.01<=z<=0.03; the lithium iron phosphate positive electrode material core surface contains a gradient coating layer; the gradient coating layer comprises two layers, an amorphous carbon layer close to the core, and an outer N / S co-doped carbon nanotube layer; the prepared lithium iron phosphate positive electrode material has excellent cycle stability and rate performance, a 1C initial discharge specific capacity of 150-160 mAh / g, a 10C initial discharge specific capacity of 88-94 mAh / g, and a capacity retention rate of 89-96.2% after 1000 cycles.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a method for preparing a carbon nanotube network-enhanced lithium iron phosphate cathode material. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, energy storage devices, and other fields due to their advantages such as high energy density and long cycle life. Lithium iron phosphate (LFP) has become a core cathode material for new energy vehicles and energy storage systems due to its high safety, long cycle life, and low cost. However, LFP suffers from poor electronic conductivity and a low lithium-ion diffusion coefficient, leading to performance degradation during high-current charge and discharge. Furthermore, during long-term cycling, the material undergoes volume changes due to lithium-ion insertion and extraction, resulting in structural instability and affecting cycle life.

[0003] Existing lithium iron phosphate (LFP) cathode materials suffer from poor conductivity and low lithium-ion diffusion rates, limiting their high-rate charge-discharge performance. The weak bonding between a single carbon coating layer and the active material leads to easy detachment during cycling, affecting long-term stability. Traditional single-element doping methods struggle to simultaneously optimize electron conduction and ion diffusion, and excessive doping can compromise the structural stability of the cathode material. While carbon nanotube coating can enhance the electrochemical performance of the cathode material, direct coating is prone to aggregation, failing to form a uniform conductive network. Therefore, there is an urgent need to develop a novel LFP cathode material enhanced with a carbon nanotube network to improve its electrochemical performance. Summary of the Invention

[0004] This invention provides a method for preparing a carbon nanotube network-reinforced lithium iron phosphate cathode material, addressing the problems of easy agglomeration and insufficient conductivity in current lithium iron phosphate cathode materials with carbon nanotube coatings, and significantly improving the material's cycle stability and rate performance. The lithium iron phosphate cathode material prepared by this invention has a 1C initial discharge specific capacity of 150–160 mAh / g, a 10C initial discharge specific capacity of 88–94 mAh / g, and a capacity retention rate of 89–96.2% after 1000 cycles.

[0005] In a first aspect, the present invention relates to a method for preparing a carbon nanotube network-reinforced lithium iron phosphate cathode material, wherein the core of the lithium iron phosphate cathode material has the chemical formula LiFe 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where 0.04≤x≤0.06, 0.02≤y≤0.04, and 0.01≤z≤0.03; The core surface of the lithium iron phosphate cathode material contains a gradient coating layer: The gradient coating layer consists of two layers: an amorphous carbon layer near the core and an N / S co-doped carbon nanotube layer on the outside. Includes the following steps: Step 1, co-precipitation doping: Weigh iron source, phosphorus source, lithium source, magnesium acetate, manganese acetate and ammonium metavanadate according to stoichiometric ratio, add dispersant, and perform hydrothermal reaction in citric acid buffer solution with pH=4.5-5.5 to obtain the precursor; Step 2: Step-by-step coating and sintering: (1) The precursor and the amorphous carbon source are ball-milled and mixed, and pre-sintered at 450-500℃ for 3-4h in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallization product is obtained. The surface of the primary crystallization product contains an amorphous carbon layer with a thickness of 5-15nm. (2) Mix pyridine, thiourea and carbon nanotubes, dissolve in anhydrous ethanol, add the first crystallization product, disperse evenly by ultrasonication, stir at 60°C until the ethanol is completely evaporated; sinter at 700-750°C for 3-5 hours in an argon atmosphere to form a 5-12 nm thick N / S co-doped carbon nanotube outer layer, and obtain the second crystallization product after cooling. (3) Anneal the secondary crystallization product at 300-350℃ for 2-3 hours, cool it to room temperature, crush it and sieve it to obtain carbon nanotube network reinforced lithium iron phosphate cathode material.

[0006] Preferably, the mass ratio of the carbon nanotubes, pyridine, and thiourea is 1:(0.6-0.7):(0.3-0.4).

[0007] Preferably, the total mass of the gradient coating layer accounts for 2%-5% of the cathode material.

[0008] Preferably, the core of the lithium iron phosphate cathode material has the chemical formula LiFe. 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where x=0.05, y=0.03, z=0.02.

[0009] Preferably, the dispersant is a mixture of sodium dodecylbenzenesulfonate and polyethylene glycol.

[0010] Preferably, the carbon source of the amorphous carbon is selected from one or more of sucrose, polyacrylonitrile, glucose, and pitch.

[0011] Preferably, the lithium source is any one or a combination of at least two of lithium carbonate, lithium acetate, or lithium chloride.

[0012] Preferably, the iron source is any one or a combination of at least two of ferrous sulfate, ferrous oxalate, and ferrous chloride.

[0013] Preferably, the phosphorus source is any one or a combination of at least two of phosphoric acid, lithium dihydrogen phosphate, sodium phosphate, or ammonium dihydrogen phosphate.

[0014] Secondly, the present invention relates to a carbon nanotube network-enhanced lithium iron phosphate cathode material, which is prepared by the aforementioned preparation method.

[0015] The beneficial effects of this invention are as follows: By designing a gradient coating structure using specific amounts of Mg, Mn, and V doping in lithium iron phosphate, along with an amorphous carbon layer and an N / S-doped carbon nanotube coating layer, the mass ratio of carbon nanotubes, pyridine, and thiourea was further optimized, improving the electrochemical and rate performance of the cathode material. The lithium iron phosphate cathode material prepared by this invention exhibits excellent cycle stability and rate performance, with a 1C initial discharge specific capacity of 150–160 mAh / g, a 10C initial discharge specific capacity of 88–94 mAh / g, and a capacity retention of 89–96.2% after 1000 cycles. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the process flow for preparing a carbon nanotube network-enhanced lithium iron phosphate cathode material disclosed in an embodiment of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Existing lithium iron phosphate (LFP) cathode materials suffer from poor conductivity and low lithium-ion diffusion rates, limiting their high-rate charge-discharge performance. Traditional single-element doping methods struggle to simultaneously optimize electron conduction and ion diffusion, and excessive doping can compromise the structural stability of the cathode material. Carbon nanotube coating can enhance the electrochemical performance of the cathode material, but direct coating is prone to agglomeration, failing to form a uniform conductive network. Therefore, there is an urgent need to develop a novel LFP cathode material enhanced with a carbon nanotube network to improve its cycle stability and rate performance.

[0020] In response to the above technical problems, such as Figure 1 As shown, this invention provides a method for preparing a carbon nanotube network-reinforced lithium iron phosphate cathode material. The core of the lithium iron phosphate cathode material has the chemical formula LiFe. 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where 0.04≤x≤0.06, 0.02≤y≤0.04, and 0.01≤z≤0.03; The core surface of the lithium iron phosphate cathode material contains a gradient coating layer: The gradient coating layer consists of two layers: an amorphous carbon layer near the core and an N / S co-doped carbon nanotube layer on the outside. Includes the following steps: Step 1, co-precipitation doping: Weigh iron source, phosphorus source, lithium source, magnesium acetate, manganese acetate and ammonium metavanadate according to stoichiometric ratio, add dispersant, and perform hydrothermal reaction in citric acid buffer solution with pH=4.5-5.5 to obtain the precursor; Step 2: Step-by-step coating and sintering: (1) The precursor and the amorphous carbon source are ball-milled and mixed, and pre-sintered at 450-500℃ for 3-4h in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallization product is obtained. The surface of the primary crystallization product contains an amorphous carbon layer with a thickness of 5-15nm. (2) Mix pyridine, thiourea and carbon nanotubes, dissolve in anhydrous ethanol, add the first crystallization product, disperse evenly by ultrasonication, stir at 60°C until the ethanol is completely evaporated; sinter at 700-750°C for 3-5 hours in an argon atmosphere to form a 5-12 nm thick N / S co-doped carbon nanotube outer layer, and obtain the second crystallization product after cooling. (3) Anneal the secondary crystallization product at 300-350℃ for 2-3 hours, cool it to room temperature, crush it and sieve it to obtain carbon nanotube network reinforced lithium iron phosphate cathode material.

[0021] In one embodiment, the mass ratio of the carbon nanotubes, pyridine, and thiourea is 1:(0.6-0.7):(0.3-0.4).

[0022] In one embodiment, the total mass of the gradient coating layer accounts for 2%-5% of the cathode material.

[0023] In one embodiment, the lithium iron phosphate cathode material core has the chemical formula LiFe. 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where x=0.05, y=0.03, z=0.02.

[0024] The core of the lithium iron phosphate cathode material employs synergistic doping with Mg, Mn, and V. Mg partially replaces Fe sites, expanding the Li-ion diffusion channel while suppressing lattice contraction during charge and discharge. Mn enhances the material's electronic conductivity and structural stability. V increases the lithium vacancy concentration in the lattice through a charge compensation mechanism, thereby improving the Li-ion migration rate. This synergistic doping optimizes lattice parameters—slightly expanding the a-axis and b-axis while contracting the c-axis—lowering the lithium-ion diffusion barrier and suppressing Fe-ion dissolution and Jahn-Teller distortion, significantly improving cycle life. The optimal doping effect is achieved when 0.04 ≤ x ≤ 0.06, 0.02 ≤ y ≤ 0.04, and 0.01 ≤ z ≤ 0.03.

[0025] Employing a gradient coating structure, the amorphous carbon source undergoes pyrolysis at low temperatures to form amorphous carbon, which uniformly covers the core surface, providing initial electron conduction channels and buffering volume changes during charge and discharge. The amorphous carbon layer strongly bonds to the core surface, and its thickness is controlled between 5-15 nm to balance electron conduction and lithium-ion penetration resistance, thereby improving the material's rate performance.

[0026] Besides enhancing the conductivity of the carbon layer through valence band transfer, sulfur (S) doping can effectively suppress irreversible reactions between carbon materials and electrolytes, thereby improving the cycle stability and rate performance of the cathode material. Pyridine (N) contributes electrons to the π-conjugated system of carbon, belonging to the p-type doping class, which enhances electron doping and can introduce active sites and defects, becoming an additional reservoir for lithium ions. Nitrogen (N) doping can enhance electronic conductivity by forming covalent bonds and increasing the graphitization level of the carbon layer. Nitrogen atoms can also inhibit the growth and aggregation of nanoparticles, shortening the solid-state diffusion path of lithium ions. The NC bond formed between nitrogen atoms and carbon enters the LiFePO4 core structure, reducing the band gap and combining with the external carbon nanotube conductive network to achieve excellent electrochemical performance.

[0027] The outer N / S co-doped carbon nanotubes form a three-dimensional conductive network, connecting isolated core particles and significantly improving electronic conductivity. The carbon nanotubes are N / S co-doped, with pyridine decomposition providing the N source and thiourea decomposition providing the S source and a partial N source. When the mass ratio of carbon nanotubes, pyridine, and thiourea is controlled at 1:(0.6-0.7):(0.3-0.4), the N and S doping amounts are optimal, synergistically reducing the charge transfer resistance at the electrolyte / electrode interface. Simultaneously, it enhances the interfacial bonding between the carbon nanotubes and the amorphous carbon layer, forming the optimal defect concentration, improving the adsorption capacity and reactivity of Li ions. Compared to adding N or S alone, N / S co-doping significantly improves the cycle stability and rate performance of the cathode material.

[0028] Step 1: Precipitation and doping: Weigh iron source, phosphorus source, lithium source, magnesium acetate, manganese acetate, and ammonium metavanadate according to stoichiometric ratio, add dispersant, and obtain a nanoscale uniform precursor through hydrothermal reaction in a citric acid buffer solution with pH=4.5-5.5.

[0029] The precursor was ball-milled and mixed with an amorphous carbon source, and then pre-sintered at 450-500℃ for 3-4 hours in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallized product was obtained. The reducing environment of hydrogen prevented Fe oxidation; the low-temperature pre-sintering at 450-500℃ avoided premature crystallization of the olivine structure and promoted densification of the amorphous carbon layer.

[0030] Pyridine, thiourea, and carbon nanotubes were mixed and dissolved in anhydrous ethanol. The primary crystallization product was then added, and the mixture was ultrasonically dispersed until homogeneous. The mixture was stirred at 60°C until the ethanol completely evaporated. Sintering was then carried out at 700-750°C for 3-5 hours in an argon atmosphere to form a 5-12 nm thick N / S co-doped carbon nanotube outer layer. Cooling yielded the secondary crystallization product. Sintering at 700-750°C promotes the chemical bonding of N / S atoms with the carbon nanotubes and simultaneously completes the crystallization of the core. Excessively high temperatures lead to increased graphitization of the carbon nanotubes and reduced surface activity.

[0031] The secondary crystallization product is annealed at 300-350℃ for 2-3 hours. Annealing can eliminate internal stress generated during sintering, improve the crystal structure and interfacial bonding of the material, optimize the interfacial structure, and enhance the crystallinity and electrochemical stability of the material.

[0032] In one embodiment, the dispersant is a mixture of sodium dodecylbenzenesulfonate and polyethylene glycol.

[0033] Sodium dodecylbenzenesulfonate, a dispersant, can be combined with polyethylene glycol to reduce particle agglomeration.

[0034] In one embodiment, the carbon source of the amorphous carbon is selected from one or more of sucrose, polyacrylonitrile, glucose, and pitch.

[0035] In one embodiment, the lithium source is any one or a combination of at least two of lithium carbonate, lithium acetate, or lithium chloride.

[0036] In one embodiment, the iron source is any one or a combination of at least two of ferrous sulfate, ferrous oxalate, and ferrous chloride.

[0037] In one embodiment, the phosphorus source is any one or a combination of at least two of phosphoric acid, lithium dihydrogen phosphate, sodium phosphate, or ammonium dihydrogen phosphate.

[0038] An embodiment of the present invention provides a carbon nanotube network-enhanced lithium iron phosphate cathode material, which is prepared using the aforementioned preparation method.

[0039] By designing a gradient coating structure using specific amounts of Mg, Mn, and V doping in lithium iron phosphate, along with an amorphous carbon layer and an N / S-doped carbon nanotube coating layer, the mass ratio of carbon nanotubes, pyridine, and thiourea was further optimized, improving the electrochemical and rate performance of the cathode material. The lithium iron phosphate cathode material prepared by this invention exhibits excellent cycle stability and rate performance, with a 1C initial discharge specific capacity of 150–160 mAh / g, a 10C initial discharge specific capacity of 88–94 mAh / g, and a capacity retention of 89–96.2% after 1000 cycles.

[0040] The embodiments of the present invention are described in detail below. The composition of the lithium iron phosphate cathode material of Embodiments 1 to 5 and Comparative Examples 1 to 2 is shown in Table 1.

[0041] The preparation methods used in the examples and comparative examples are as follows: A method for preparing a carbon nanotube network-reinforced lithium iron phosphate cathode material, characterized in that: the core of the lithium iron phosphate cathode material is an olivine structure with the chemical formula LiFe1-xy-zMgxMnyVzPO4, wherein 0.04≤x≤0.06, 0.02≤y≤0.04, and 0.01≤z≤0.03; The core surface of the lithium iron phosphate cathode material contains a gradient coating layer: The gradient coating layer consists of two layers: an amorphous carbon layer near the core and an N / S co-doped carbon nanotube layer on the outside. Includes the following steps: Step 1, co-precipitation doping: Weigh iron source, phosphorus source, lithium source, magnesium acetate, manganese acetate and ammonium metavanadate according to stoichiometric ratio, add dispersant, and perform hydrothermal reaction in citric acid buffer solution with pH=4.5-5.5 to obtain the precursor; Step 2: Step-by-step coating and sintering: (1) The precursor and the amorphous carbon source are ball-milled and mixed, and pre-sintered at 450-500℃ for 3-4h in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallization product is obtained. The surface of the primary crystallization product contains an amorphous carbon layer with a thickness of 5-15nm. (2) Mix pyridine, thiourea and carbon nanotubes, dissolve in anhydrous ethanol, add the first crystallization product, disperse evenly by ultrasonication, stir at 60°C until the ethanol is completely evaporated; sinter at 700-750°C for 3-5 hours in an argon atmosphere to form a 5-12 nm thick N / S co-doped carbon nanotube outer layer, and obtain the second crystallization product after cooling. (3) Anneal the secondary crystallization product at 300-350℃ for 2-3 hours, cool it to room temperature, crush it and sieve it to obtain carbon nanotube network reinforced lithium iron phosphate cathode material.

[0042] The mass ratio of the carbon nanotubes, pyridine, and thiourea is 1:(0.6-0.7):(0.3-0.4). The total mass of the gradient coating layer accounts for 2%-5% of the cathode material.

[0043] The dispersant is a mixture of sodium dodecylbenzenesulfonate and polyethylene glycol in a weight ratio of 1:1.

[0044] Table 1: Lithium iron phosphate cathode materials of Examples 1-5 and Comparative Examples 1-5

[0045] The process parameters used in the preparation methods of Examples 1-5 and Comparative Examples 1-5 of this invention are shown in Table 2.

[0046] Table 2: Process parameters used in the preparation methods of Examples 1-5 and Comparative Examples 1-5

[0047] Comparative Example 4 did not undergo N / S co-doped carbon nanotube outer layer coating. The main difference between the preparation method used and Example 3 is: Step 2, stepwise coating and sintering: (1) The precursor and the amorphous carbon source are ball-milled and mixed, and pre-sintered at 730°C for 4 hours in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallization product is obtained. The surface of the primary crystallization product contains an outer layer of amorphous carbon layer with a thickness of 5-15 nm. (2) The primary crystallization product was annealed at 330°C for 2.5 h, cooled to room temperature, crushed and sieved to obtain carbon nanotube network reinforced lithium iron phosphate cathode material.

[0048] The lithium iron phosphate positive electrode active materials of the above comparative examples and comparative examples were prepared into positive electrode sheets, assembled into soft-pack batteries, and their performance was measured. The results are shown in Table 3.

[0049] Table 3: Performance data of examples and comparative examples

[0050] As can be seen from Table 3, the lithium iron phosphate cathode material prepared by the present invention has excellent cycle stability and rate performance, with a first discharge specific capacity of 150-160 mAh / g at 1C, a first discharge specific capacity of 88-94 mAh / g at 10C, and a capacity retention rate of 89-96.2% after 1000 cycles.

[0051] Compared with Examples 1 to 4, Example 5 changed the mass ratio of carbon nanotube:pyridine:thiourea to not satisfy the range of 1:(0.6-0.7):(0.3-0.4), the N / S co-doping synergistic effect was weakened, and the capacity retention rate of the first discharge specific capacity at 1C and the first discharge specific capacity at 10C after 1000 cycles both decreased slightly.

[0052] After adjusting the doping content of the core, Comparative Examples 1 and 2 showed a significant decrease in the first discharge specific capacity at 1C and the capacity retention rate of the first discharge specific capacity at 10C after 1000 cycles.

[0053] Comparative Example 3 adjusted the coating thickness and the proportion of the total mass of the coating, resulting in a significant decrease in the capacity retention rate of the first discharge specific capacity at 1C and the first discharge specific capacity at 10C after 1000 cycles.

[0054] Comparative Example 4 only contains an amorphous carbon coating layer. Comparative Example 5 changed the temperature parameters of pre-sintering and sintering, which caused the lithium iron phosphate core to not crystallize sufficiently. The 1C first discharge specific capacity and the 10C first discharge specific capacity after 1000 cycles of capacity retention both decreased significantly.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for preparing a carbon nanotube network-reinforced lithium iron phosphate cathode material, characterized in that: The core of the lithium iron phosphate cathode material has the chemical formula LiFe. 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where 0.04≤x≤0.06, 0.02≤y≤0.04, and 0.01≤z≤0.03; The core surface of the lithium iron phosphate cathode material contains a gradient coating layer: The gradient coating layer consists of two layers: an amorphous carbon layer near the core and an N / S co-doped carbon nanotube layer on the outside. Includes the following steps: Step 1, co-precipitation doping: Weigh iron source, phosphorus source, lithium source, magnesium acetate, manganese acetate and ammonium metavanadate according to stoichiometric ratio, add dispersant, and perform hydrothermal reaction in citric acid buffer solution with pH=4.5-5.5 to obtain the precursor; Step 2: Step-by-step coating and sintering: (1) The precursor and the amorphous carbon source are ball-milled and mixed, and pre-sintered at 450-500℃ for 3-4h in a mixed atmosphere of hydrogen and argon. After cooling to room temperature, a primary crystallization product is obtained. The surface of the primary crystallization product contains an amorphous carbon layer with a thickness of 5-15nm. (2) Mix pyridine, thiourea and carbon nanotubes, dissolve in anhydrous ethanol, add the first crystallization product, disperse evenly by ultrasonication, stir at 60°C until the ethanol is completely evaporated; sinter at 700-750°C for 3-5 hours in an argon atmosphere to form a 5-12 nm thick N / S co-doped carbon nanotube outer layer, and obtain the second crystallization product after cooling. (3) Anneal the secondary crystallization product at 300-350℃ for 2-3 hours, cool it to room temperature, crush it and sieve it to obtain carbon nanotube network reinforced lithium iron phosphate cathode material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the carbon nanotubes, pyridine, and thiourea is 1:(0.6-0.7):(0.3-0.4).

3. The preparation method according to claim 1, characterized in that, The total mass of the gradient coating layer accounts for 2%-5% of the cathode material.

4. The preparation method according to claim 1, characterized in that, The core of the lithium iron phosphate cathode material has the chemical formula LiFe. 1-x-y-z Mg x Mn y V z The olivine structure of PO4, where x=0.05, y=0.03, z=0.

02.

5. The preparation method according to claim 1, characterized in that, The dispersant is a mixture of sodium dodecylbenzenesulfonate and polyethylene glycol.

6. The preparation method according to claim 1, characterized in that, The carbon source for the amorphous carbon is selected from one or more of sucrose, polyacrylonitrile, glucose, and pitch.

7. The preparation method according to claim 1, characterized in that, The lithium source is any one or a combination of at least two of lithium carbonate, lithium acetate, or lithium chloride.

8. The preparation method according to claim 1, characterized in that, The iron source is any one or a combination of at least two of ferrous sulfate, ferrous oxalate, and ferrous chloride.

9. The preparation method according to claim 1, characterized in that, The phosphorus source is any one or a combination of at least two of phosphoric acid, lithium dihydrogen phosphate, sodium phosphate, or ammonium dihydrogen phosphate.

10. A carbon nanotube network-reinforced lithium iron phosphate cathode material, characterized in that, It is prepared by any one of the preparation methods according to claims 1-9.

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