Silver particle modified and carbon coated lithium manganese iron phosphate positive electrode material and preparation method thereof

Abstract

The invention discloses a silver particle modified and carbon coated lithium manganese iron phosphate positive electrode material and a preparation method thereof, and relates to the technical field of materials.The preparation method comprises the steps that a lithium source, an iron source, a manganese source and a phosphorus source are mixed and dissolved, and a mixed solution is obtained; adding a silver ion solution into the mixed solution, and carrying out a first hydrothermal reaction to obtain a reaction solution; mixing the reaction liquid with a carbon source and a reducing agent, carrying out a second hydrothermal reaction, and separating a solid phase to obtain a precursor; and sintering the precursor to obtain the lithium iron manganese phosphate positive electrode material. In the hydrothermal reaction stage, silver ions can inhibit rapid growth of high-energy crystal faces, and finally more high-energy crystal faces are exposed. And in the sintering stage, silver ions are reduced into simple substances to modify the carbon layer, a carbon-metal composite conductive network is formed, and the conductivity of the carbon layer is improved. The preparation method is simple and convenient to operate, can quickly and efficiently form the nanoscale lithium manganese iron phosphate positive electrode material with relatively good electrical properties and [001] crystal face orientation, and has a relatively good application prospect.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a silver particle-modified carbon-coated lithium manganese iron phosphate positive electrode material and a preparation method thereof. Background Art

[0002] In recent years, with the continued high consumption of traditional energy (such as oil, natural gas, etc.) and the increasingly severe environmental problems it brings, the call for accelerated transformation of energy structure has become stronger. Among the many energy conversion and storage devices, lithium-ion batteries are being widely used in various fields due to their excellent electrochemical performance, high safety, good cost performance and long life, becoming the most promising solution. x Fe 1-x PO4 e - / Li + The poor conductivity of LiMn is one of the reasons that hinder its development. x Fe 1-x Very low Li in PO4 + The ion diffusivity is mainly attributed to its one-dimensional diffusion (along the

[010] direction). Therefore, it is of great significance to design a LMFP material with a short (010) dimension to improve its rate capability and improve its electrical conductivity. Summary of the invention

[0003] The purpose of the present invention is to provide a silver particle modified carbon-coated lithium manganese iron phosphate positive electrode material and a preparation method thereof, which is simple and convenient to operate, can quickly and efficiently obtain a short (010) size LMFP material, and at the same time improve the conductivity of its carbon layer, thereby obtaining better battery performance.

[0004] The embodiment of the present invention is achieved as follows: A method for preparing a silver particle modified carbon-coated lithium manganese iron phosphate positive electrode material, comprising: Mixing and dissolving a lithium source, an iron source, a manganese source, and a phosphorus source to obtain a mixed solution; Adding a silver ion solution to the mixed solution to perform a first hydrothermal reaction to obtain a reaction solution; The reaction solution is mixed with a carbon source and a reducing agent, and a second hydrothermal reaction is performed, and a solid phase is separated to obtain a precursor; The precursor is sintered to obtain the lithium manganese iron phosphate positive electrode material.

[0005] A silver particle modified carbon-coated lithium manganese iron phosphate positive electrode material is prepared by the preparation method of the silver particle modified carbon-coated lithium manganese iron phosphate positive electrode material.

[0006] The beneficial effects of the embodiments of the present invention are: An embodiment of the present invention provides a silver particle modified carbon-coated lithium iron manganese phosphate cathode material and a preparation method thereof. In this preparation method, a lithium source, an iron source, a manganese source, and a phosphorus source are mixed and dissolved to obtain a mixed solution; a silver ion solution is added to the mixed solution, and a first hydrothermal reaction is carried out to obtain a reaction solution; the reaction solution is mixed with a carbon source and a reducing agent, and a second hydrothermal reaction is carried out, and the solid phase is separated to obtain a precursor; the precursor is sintered to obtain the lithium iron manganese phosphate cathode material. In the hydrothermal reaction stage, silver ions can inhibit the rapid growth of high-energy crystal planes and finally expose more high-energy crystal planes. In the sintering stage, silver ions are reduced to elemental silver to modify the carbon layer, forming a "carbon-metal" composite conductive network and improving the conductivity of the carbon layer. This preparation method is simple and convenient to operate, can quickly and efficiently form a nanoscale lithium iron manganese phosphate cathode material with better electrical properties and

[001] crystal plane orientation, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use 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 limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0008] Figure 1 SEM spectrum of the silver particle modified carbon-coated lithium iron manganese phosphate cathode material provided in Embodiment 1 of the present invention; Figure 2 SEM spectrum of the silver particle modified carbon-coated lithium iron manganese phosphate cathode material provided in Embodiment 2 of the present invention; Figure 3 SEM spectrum of the silver particle modified carbon-coated lithium iron manganese phosphate cathode material provided in Embodiment 3 of the present invention; Figure 4 SEM spectrum of the silver particle modified carbon-coated lithium iron manganese phosphate cathode material provided in Comparative Example 1 of the present invention Figure 5 3C charge-discharge capacity test chart of the coin cells prepared from the cathode materials of Embodiments 1-4 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0010] The following specifically describes a lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated, and its preparation method and application according to the embodiments of the present invention.

[0011] The embodiment of the present invention provides a preparation method of a lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated, which includes: S1. Mix and dissolve a lithium source, an iron source, a manganese source, and a phosphorus source to obtain a mixed solution; S2. Add a silver ion solution to the mixed solution and perform a first hydrothermal reaction to obtain a reaction solution; S3. Mix the reaction solution with a carbon source and a reducing agent, perform a second hydrothermal reaction, and separate the solid phase to obtain a precursor; S4. Sinter the precursor to obtain the lithium iron manganese phosphate cathode material.

[0012] Before sintering, partial silver ions are added in this preparation method. Since the ionic radius of Ag + (1.15 Å) is significantly different from that of other metal ions (such as Li + : 0.76 Å, Fe 2+ : 0.78 Å, Mn 2+ : 0.83 Å), it is difficult to directly replace Li⁺ or transition metal sites in the phosphate cathode material (such as LMFP). However, it can act as a surface-adsorbed ion and preferentially adsorb at the defect or step sites of specific crystal planes. At the same time, since the

[010] crystal plane of lithium iron manganese phosphate belongs to a high-energy crystal plane, its surface is rich in uncoordinated atoms and has a high surface charge density. The adsorption of Ag + can neutralize the local negative charge, reduce the surface energy, inhibit the rapid growth of the high-energy crystal plane, and finally expose more high-energy crystal planes.

[0013] Moreover, during the first hydrothermal reaction, as the lithium iron manganese phosphate crystal grows, a core is gradually formed, and Ag + , due to the mismatch of ionic radius, does not participate in crystal formation, resulting in Ag + always adsorbing on the surface of the crystal. During the second hydrothermal reaction, due to the addition of the reducing agent, Ag + is reduced to silver single particles by the reducing agent. Since Ag + is more oxidizing than Fe 2+ and Mn 2+ , Ag + will be preferentially reduced. Therefore, there is no need to worry about the over-reduction of Mn 2+ and Fe 2+ in the crystal. In the sintering process, the carbon source undergoes pyrolysis under high temperature and high pressure conditions to generate a carbon coating layer, and silver is uniformly dispersed in the carbon layer to form a "carbon-metal" composite conductive network. Since the conductivity of silver is much higher than that of carbon materials (the silver conductivity is about 6.3×10 7S / m, carbon is about 10 3 S / m), thus significantly improving the conductivity of the carbon layer.

[0014] Furthermore, the iron source includes at least one of ferrous oxalate, ferrous chloride, and ferrous nitrate; the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium dihydrogen phosphate; the manganese source includes at least one of manganese oxalate, manganese tetraoxide, manganese sulfate, manganese acetate, and manganese nitrate; the phosphorus source includes at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and lithium dihydrogen phosphate. It should be particularly noted that the iron source preferably selects an iron source with divalent iron ions because the reduction potential of trivalent iron ions is equivalent to that of silver ions, which will consume the reducing agent and affect the accurate estimation of the dosage of the reducing agent.

[0015] Optionally, the molar ratio of Li:P:(Fe + Mn) provided by the lithium source, iron source, manganese source, and phosphorus source is 0.99~1.05:0.98~1.01:0.98~1.01. The molar ratio of Mn:Fe provided by the manganese source and iron source is (5:5)~(8:2). Within the above ratio range, the overall performance of lithium iron manganese phosphate is better.

[0016] The mass of silver in the silver ion solution is 0.05%~0.5% of the total mass of the lithium source, iron source, manganese source, and phosphorus source. The content of silver ions should not be too high, as too high a content of silver ions will cause silver ions to enter the inner core crystal to form element doping, affecting the crystal structure of lithium iron manganese phosphate. Within the above dosage range, the content of silver ions is also sufficient to achieve a better crystallization induction effect and improve the conductivity of the carbon layer.

[0017] Furthermore, the temperature of the first hydrothermal reaction is 150~250 °C, and the duration is 4~16 h. Under the above reaction conditions, the crystallization process is more gentle and controllable, enabling Ag + to migrate better to the crystal surface and continuously and directionally induce the growth of crystal planes.

[0018] Optionally, the carbon source includes at least one of glucose, sucrose, polyvinylpyrrolidone, or polyethylene glycol; the total carbon content in the silver particle modified carbon-coated lithium iron manganese phosphate cathode material is 1 wt%~3 wt%. Within the above ratio range, it is beneficial to form a uniform carbon coating layer.

[0019] The reducing agent includes at least one of ascorbic acid, citric acid, oxalic acid, and formic acid. The use of the reducing agent is mainly to reduce silver ions to silver elemental particles. According to the reaction formula of the reducing agent and silver ions, the dosage of the reducing agent is 1.01 - 1.05 times its theoretical dosage. For example, taking ascorbic acid as an example, according to the redox reaction formula of silver ions and ascorbic acid, reducing 1 mole of silver ions requires 0.5 mol of ascorbic acid. Then the theoretical dosage of ascorbic acid is 0.5 mol, and the actual dosage needs to be 1% - 5% in excess. So the actual dosage of ascorbic acid is 0.505 - 0.525 mol. By selecting a mild reducing agent and controlling the dosage of the reducing agent, Fe 2+ and Mn 2+ can be prevented from being over-reduced. In addition, the temperature of the second hydrothermal reaction is 150 - 250 °C, and the duration is 4 - 16 h. Under the above conditions, the reduction process is made more mild and controllable.

[0020] Furthermore, the temperature for sintering the precursor is 400 - 800 °C, and the duration is 2 - 10 h. Under this condition, the carbon source can be better pyrolyzed to form a uniform carbon coating layer.

[0021] The embodiment of the present invention also provides a lithium iron phosphate cathode material modified with silver particles and carbon-coated, which is prepared by the preparation method of the lithium iron phosphate cathode material modified with silver particles and carbon-coated as described above.

[0022] Furthermore, the lithium iron phosphate cathode material is a

[001] crystal plane-oriented nanomaterial, which is in a rod-like structure as a whole. The growth direction of the rod-like lithium iron phosphate crystal core is the

[001] direction, and it is externally coated with a silver-modified carbon coating layer. Compared with traditional materials, this lithium iron phosphate cathode material has better rate performance and conductivity.

[0023] The features and properties of the present invention will be further described in detail below in conjunction with embodiments. Example 1

[0024] This example provides a lithium iron phosphate cathode material modified with silver particles and carbon-coated, and its preparation method is as follows: S1. Mix and dissolve manganese sulfate, ferrous sulfate, phosphoric acid, and lithium hydroxide to obtain a mixed solution, where the manganese to iron ratio is 6:4.

[0025] S2. Add the mixed solution to a high-pressure reaction kettle, add a silver nitrate solution (the mass of silver is 0.1% of the total mass of the lithium source, iron source, manganese source, and phosphorus source) to the mixed solution, and conduct the first hydrothermal reaction. The reaction temperature is 160 °C, and keep warm for 6 h to obtain a reaction solution.

[0026] S3. Mix the reaction solution with polyvinylpyrrolidone and ascorbic acid (the amount of ascorbic acid is 0.52 times the molar amount of silver ions), and conduct the second hydrothermal reaction at a reaction temperature of 180 °C for 12 h. After the reaction is completed, cool it to room temperature and centrifuge to obtain the precursor.

[0027] S4. Dry the precursor at 60 °C for 6 h, and then sinter it at 650 °C for 6 h to obtain the lithium iron manganese phosphate cathode material.

[0028] The SEM pattern of the lithium iron manganese phosphate cathode material modified with silver particles and coated with carbon prepared in this example is as Figure 1 shown. Its overall structure is rod-shaped. The growth direction of the rod-shaped lithium iron manganese phosphate crystal core is the

[001] direction. It is coated with a silver-modified carbon coating layer on the outside and has a better tap density. Example 2

[0029] This example provides a lithium iron manganese phosphate cathode material modified with silver particles and coated with carbon, and its preparation method is as follows: S1. Mix and dissolve manganese oxalate, ferrous chloride, ammonium phosphate, and lithium nitrate to obtain a mixed solution, where the manganese to iron ratio is 5:5.

[0030] S2. Add the mixed solution to a high-pressure reaction kettle, add silver nitrate solution (the mass of silver is 0.05% of the total mass of the lithium source, iron source, manganese source, and phosphorus source) to the mixed solution, and conduct the first hydrothermal reaction at a reaction temperature of 250 °C for 4 h to obtain a reaction solution.

[0031] S3. Mix the reaction solution with glucose and ascorbic acid (the amount of ascorbic acid is 0.505 times the molar mass of silver ions), and conduct the second hydrothermal reaction at a reaction temperature of 250 °C for 4 h. After the reaction is completed, cool it to room temperature and centrifuge to obtain the precursor.

[0032] S4. Dry the precursor at 60 °C for 6 h, and then sinter it at 800 °C for 2 h to obtain the lithium iron manganese phosphate cathode material.

[0033] The SEM pattern of the lithium iron manganese phosphate cathode material modified with silver particles and coated with carbon prepared in this example is as Figure 2 shown. Its overall structure is rod-shaped. The growth direction of the rod-shaped lithium iron manganese phosphate crystal core is the

[001] direction. It is coated with a silver-modified carbon coating layer on the outside and has a better tap density. Example 3

[0034] This example provides a lithium iron manganese phosphate cathode material modified with silver particles and coated with carbon, and its preparation method is as follows: S1. Mix and dissolve manganese nitrate, ferrous nitrate, phosphoric acid, and lithium carbonate to obtain a mixed solution, where the manganese to iron ratio is 7:3.

[0035] S2. Add the mixed solution into a high-pressure reactor, add silver nitrate solution (the mass of silver is 0.5% of the total mass of lithium source, iron source, manganese source, and phosphorus source) to the mixed solution, and conduct the first hydrothermal reaction at a reaction temperature of 150 °C for 16 h to obtain a reaction solution.

[0036] S3. Mix the reaction solution with polyethylene glycol and ascorbic acid (the amount of ascorbic acid is 0.51 times the molar mass of silver ions), conduct the second hydrothermal reaction at a reaction temperature of 150 °C for 16 h, cool to room temperature after the reaction is completed, and centrifuge to obtain a precursor.

[0037] S4. Dry the precursor at 60 °C for 6 h, and then sinter it at 400 °C for 10 h to obtain the lithium iron manganese phosphate cathode material.

[0038] The SEM image of the lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated prepared in this example is as Figure 3 shown. Its overall structure is rod-shaped. The growth direction of the rod-shaped lithium iron manganese phosphate crystal core is the

[001] direction, and it is externally coated with a silver-modified carbon coating layer, having a better tap density. Example 4

[0039] This example provides a lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated, and its preparation method is as follows: S1. Mix and dissolve manganese sulfate, ferrous sulfate, phosphoric acid, and lithium hydroxide to obtain a mixed solution, where the manganese to iron ratio is 6:4.

[0040] S2. Add the mixed solution into a high-pressure reactor, add silver nitrate solution (the mass of silver is 0.1% of the total mass of lithium source, iron source, manganese source, and phosphorus source) to the mixed solution, and conduct the first hydrothermal reaction at a reaction temperature of 160 °C for 6 h to obtain a reaction solution.

[0041] S3. Mix the reaction solution with polyvinylpyrrolidone and ascorbic acid (the amount of ascorbic acid is 0.52 times the molar mass of silver ions), conduct the second hydrothermal reaction at a reaction temperature of 180 °C for 12 h, cool to room temperature after the reaction is completed, and centrifuge to obtain a precursor.

[0042] S4. Dry the precursor at 60 °C for 6 h, then sinter it at 450 °C for 2 h, and then raise the temperature to 750 °C and continue sintering for 6 h to obtain the lithium iron manganese phosphate cathode material.

[0043] Comparative Example 1 This comparative example provides a carbon-coated lithium iron manganese phosphate cathode material, and its preparation method is as follows: S1. Mix and dissolve manganese sulfate, ferrous sulfate, phosphoric acid, and lithium hydroxide to obtain a mixed solution, where the manganese to iron ratio is 6:4.

[0044] S2. Add the mixed solution to a high-pressure reactor, add polyvinylpyrrolidone, and carry out a hydrothermal reaction at a reaction temperature of 180 °C for 12 h. After the reaction is completed, cool it to room temperature and centrifuge to obtain a precursor.

[0045] S4. Dry the precursor at 60 °C for 6 h, and then sinter it at 650 °C for 6 h to obtain the lithium iron manganese phosphate cathode material. As Figure 4 shown. Without the participation of silver ions, the lithium iron manganese phosphate has no ability to grow directionally during the crystallization process. The obtained cathode material is spherical as a whole and has uneven sizes, showing an obvious gap from the lithium iron manganese phosphate cathode material of the embodiment of the present invention.

[0046] Comparative Example 2 This comparative example provides a carbon-coated lithium iron manganese phosphate cathode material, and its preparation method is basically the same as that of Example 1, except that in step S2, the dosage of silver is increased to 2%.

[0047] Comparative Example 3 This comparative example provides a carbon-coated lithium iron manganese phosphate cathode material, and its preparation method is basically the same as that of Example 1, except that in step S2, the temperature of the first hydrothermal reaction is increased to 350 °C.

[0048] Comparative Example 4 This comparative example provides a carbon-coated lithium iron manganese phosphate cathode material, and its preparation method is basically the same as that of Example 1, except that in step S3, the dosage of ascorbic acid is increased to 0.65 times the molar mass of silver ions.

[0049] Test Example 1 Use the lithium iron manganese phosphate cathode materials provided in Examples 1 to 4 and Comparative Examples 1 to 4, assemble button cells with them as the battery cathode materials for testing, and respectively test their tap density, powder resistivity, and specific capacity at 0.1C, 1C, and 3C rates (refer to Figure 5 shown). The test results are shown in Table 1.

[0050] Table 1. Test results of lithium iron manganese phosphate cathode materials Compaction density (g / cc) Powder resistivity (Ω·cm) Discharge specific capacity at 0.1C (mAh / g) Discharge specific capacity at 1C (mAh / g) Discharge specific capacity at 3C (mAh / g) Example 1 2.273 24.166 152.045 148.808 146.627 Example 2 2.251 22.690 153.632 147.069 145.745 Example 3 2.204 23.896 148.378 146.393 144.527 Example 4 2.238 22.965 149.462 141.321 143.276 Comparative Example 1 2.221 35.432 149.828 138.299 132.464 Comparative Example 2 2.241 12.954 148.234 144.574 140.975 Comparative Example 3 2.214 24.451 148.724 140.540 137.538 Comparative Example 4 2.235 23.14 143.715 132.832 125.745 As can be seen from Table 1, for the lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated provided in Embodiments 1 to 4 of the present invention, its tap density reaches 2.204 - 2.273 g / cm³, and the powder resistivity reaches 11.690 - 12.965 Ω·cm. Compared with the material without silver ion modification (Comparative Example 1), the electrical conductivity has been significantly improved. In addition, compared with Comparative Example 1, its discharge specific capacity at 0.1C rate is basically the same, but the discharge specific capacity at high rates has been significantly improved, and as the rate increases, the gap becomes more significant.

[0051] In contrast, in Comparative Example 2, we increased the amount of silver. It can be seen that although the powder resistivity was further reduced, the discharge specific capacity decreased because some silver formed doping in lithium iron manganese phosphate.

[0052] In Comparative Example 3, the temperature of the first hydrothermal reaction was increased, and the crystal growth was too fast, which also led to the effect of crystal orientation growth being inferior to that of the embodiment, and there was a certain degree of silver ion doping, also resulting in a decrease in the discharge specific capacity.

[0053] In Comparative Example 4, more reducing agent was used, and some manganese and iron ions were reduced, resulting in a decrease in the discharge specific capacity. The reduction amplitude even exceeded that of Comparative Example 1. Therefore, the control of the amount of reducing agent in the embodiments of the present invention is very crucial.

[0054] In summary, the embodiments of the present invention provide a lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated and its preparation method. The preparation method mixes and dissolves a lithium source, an iron source, a manganese source, and a phosphorus source to obtain a mixed solution; adds a silver ion solution to the mixed solution and performs the first hydrothermal reaction to obtain a reaction solution; mixes the reaction solution with a carbon source and a reducing agent, performs the second hydrothermal reaction, and separates the solid phase to obtain a precursor; sinters the precursor to obtain the lithium iron manganese phosphate cathode material. In the hydrothermal reaction stage, silver ions can inhibit the rapid growth of high-energy crystal planes and finally expose more high-energy crystal planes. In the sintering stage, silver ions are reduced to elemental substances to modify the carbon layer, forming a "carbon-metal" composite conductive network to improve the conductivity of the carbon layer. The preparation method is simple and convenient to operate, and can quickly and efficiently form a nanoscale lithium iron manganese phosphate cathode material with better electrical properties and

[001] crystal plane orientation, having better application prospects.

[0055] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a lithium iron manganese phosphate cathode material modified with silver particles and carbon-coated, characterized in that, Comprising: Mixing and dissolving a lithium source, an iron source, a manganese source, and a phosphorus source to obtain a mixed solution; Adding a silver ion solution to the mixed solution to conduct a first hydrothermal reaction to obtain a reaction solution; Mixing the reaction solution with a carbon source and a reducing agent to conduct a second hydrothermal reaction, and separating the solid phase to obtain a precursor; Sintering the precursor to obtain the lithium iron manganese phosphate cathode material.

2. The preparation method according to claim 1, wherein The iron source includes at least one of ferrous oxalate, ferrous chloride, and ferrous nitrate; the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium dihydrogen phosphate; the manganese source includes at least one of manganese oxalate, manganese tetraoxide, manganese sulfate, manganese acetate, and manganese nitrate; the phosphorus source includes at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and lithium dihydrogen phosphate.

3. The preparation method according to claim 1, characterized in that, The molar ratio of Mn:Fe provided by the manganese source and the iron source is (5:5) to (8:2).

4. The preparation method according to claim 1, characterized in that, The mass of silver in the silver ion solution is 0.05% to 0.5% of the total mass of the lithium source, the iron source, the manganese source, and the phosphorus source.

5. The preparation method according to claim 1, characterized in that, The temperature of the first hydrothermal reaction is 150 to 250 °C, and the duration is 4 to 16 h.

6. The preparation method according to claim 1, characterized in that, The carbon source includes at least one of glucose, sucrose, polyvinylpyrrolidone, or polyethylene glycol; the total carbon content in the silver particle-modified carbon-coated lithium iron manganese phosphate cathode material is 1 wt% to 3 wt%.

7. The preparation method according to claim 1, characterized in that, The reducing agent includes at least one of ascorbic acid, citric acid, oxalic acid, and formic acid. According to the reaction formula of the reducing agent and silver ions, the dosage of the reducing agent is 1.01 to 1.05 times its theoretical dosage.

8. The preparation method according to claim 1, characterized in that, The temperature of the second hydrothermal reaction is 150 to 250 °C, and the duration is 4 to 16 h.

9. The preparation method according to claim 1, characterized in that, The temperature for sintering the precursor is 400 to 800 °C, and the duration is 2 to 10 h.

10. A lithium iron phosphate cathode material modified with silver particles and carbon-coated manganese phosphate, characterized in that, Prepared by the preparation method of the silver particle-modified carbon-coated lithium iron manganese phosphate cathode material according to any one of claims 1 to 9.

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