A zirconium-doped lithium manganese iron phosphate cathode material, its preparation method and application

Abstract

This invention discloses a zirconium-doped lithium manganese iron phosphate cathode material. First, Mn is synthesized via a hydrothermal method. 0.6 Fe 0.4 A PO4 precursor was used, followed by the addition of lithium hydroxide monohydrate and zirconium oxychloride octahydrate, which were thoroughly mixed. Finally, zirconium-doped lithium manganese iron phosphate cathode material LMFP-Zr was obtained through segmented high-temperature sintering. The LMFP-Zr has a basic microstructure of granular particles with a size of 200-300 nm. Its preparation method includes the following steps: 1. Mn 0.6 Fe 0.4 Preparation of PO4 precursor; 2. Synthesis of LMFP-Zr. When used as a cathode material in lithium-ion batteries, at 1 C = 170 mA hg... ‑1 Under test conditions of 2.5–4.5 V voltage range and 1 C current density, the initial discharge specific capacity is 130–135 mA hg. ‑1 When the number of cycles is 200, the residual discharge specific capacity is 120-125 mA hg. ‑1 The capacity retention rate is 90-92%.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode materials, specifically relating to a zirconium-doped lithium manganese iron phosphate cathode material, its preparation method, and its application. Background Technology

[0002] Lithium iron manganese phosphate (LiFeMnPO4, LMFP), as a cathode material for lithium-ion batteries, combines the high safety of lithium iron phosphate (LiFePO4, LFP) with the high voltage characteristics of lithium manganese phosphate (LiMnPO4, LMP), offering advantages in high energy density and voltage plateau. However, due to the presence of Mn... 3+ The Jahn-Teller effect causes crystal deformation in LMFP, which increases the resistance to electron transport and reduces electronic conductivity. At the same time, the internal resistance of the LMFP lattice also leads to a significant decrease in the ion diffusion coefficient.

[0003] To address the low lithium-ion diffusion rate problem in LMFPs, elemental doping can be used to alter lattice vacancies or interatomic bond lengths, thereby promoting lithium diffusion. + Movement within the crystal lattice improves electrochemical performance. For example, existing literature 1 (Liu Qinzhu, Wang Feng, Deng Jianqiu, et al. Effect of niobium doping on the electrochemical performance of lithium manganese iron phosphate [J]. Electronic Components and Materials, 2025, 44 (09): 1018-1024 +1033.) uses a combination of ball milling and spray drying to prepare niobium-doped lithium manganese iron phosphate cathode material LiMn 0.5 Fe 0.485 Nb 0.015 PO4 / C yielded an initial discharge specific capacity of 137 mA hg at a current density of 0.1 C. -1 At a current density of 1 C, after 200 cycles, the capacity retention rate is 90.8%. Nb doping can reduce charge transfer resistance and accelerate Li... + Diffusion improves the conductivity of lithium manganese iron phosphate. However, Nb-doped systems suffer from poor matrix solid solution stability due to the very low solid solution saturation of Nb in the LMFP lattice. This characteristic directly leads to the inevitable spontaneous segregation of Nb at grain boundaries and the formation of inert lithium niobate impurities, even under theoretically optimal doping ratios and conventional sintering conditions. Ultimately, this results in the blockage of lithium-ion diffusion channels and an increase in bulk impedance.

[0004] To address the low lithium-ion diffusion rate of LMFPs, Co doping can be used to modulate crystal lattice parameters, band structure, and bond lengths, thereby broadening lithium-ion transport channels and suppressing transition metal dissolution. For example, existing literature 2 (Lu XC, He HJ, Jiang WQ, et al. Unveiling enhanced electrochemical performance of LiMn) 1-x Co x PO4 / C cathode materials through co-doping strategy [J]. Journal of Alloys and Compounds, 2024.) LiMn was prepared using a high-temperature solid-state sintering combined with in-situ carbon coating process. 1-x Co x The PO4 / C cathode material, under conditions of 5% Co doping and a current density of 0.5 C, maintained a current density of 116.4 mA·h·g after 100 cycles. -1 The discharge specific capacity retained at 95.4%. Research has confirmed that Co doping effectively shrinks the LMP cell volume, reduces electrode charge transfer resistance, accelerates lithium-ion lattice diffusion, and optimizes electronic conductivity through ion valence complementarity, thus suppressing manganese dissolution in the electrolyte. However, Co doping suffers from poor structural stability. Specifically, under long-term cycling conditions, Co atoms continuously induce structural distortion, leading to the formation of inert cobalt phosphate impurities, ultimately resulting in a continuously increasing interfacial impedance and reduced cycling stability.

[0005] Furthermore, Ni doping can be used to modulate the Li-O and Mn / Fe-O bond lengths, optimize the lattice structure, broaden the lithium-ion transport channels, and accelerate Li⁺ lattice migration to improve electrochemical performance, thereby increasing the lithium-ion diffusion rate of LMFPs. For example, existing literature 3 (Xue L, Liu S, Zhang S) , Qie L , et al. Effect of Ni 2+ DopingModification on the Electrochemical Performance of LiMn 0.75 Fe 0.25 PO4 CathodeMaterial [J]. Chinese Academy of Sciences, 2025, 83 (5): 853-860.) Nickel-doped lithium manganese iron phosphate cathode material LiMn was prepared using a solvothermal combined with high-temperature calcination process.0.75 Fe 0.24 Ni 0.01 PO4 / C yielded an initial discharge specific capacity of 147 mA hg at a current density of 0.1 C. -1 The technology achieved a capacity retention of 88.2% after only 150 cycles at a 0.5 C rate. Research has confirmed that Ni doping, by differentially controlling the bond lengths within the crystal and shortening the Mn / Fe-O bonds, can reconstruct the LMFP microstructure, effectively widening the lithium-ion transport channels and significantly increasing the lithium-ion lattice migration rate. However, Ni doping cannot introduce high-strength chemical bonds to build a rigid lattice framework; therefore, it lacks stress relief and lattice solidification capabilities, leading to lattice structure collapse during long cycles.

[0006] In addition to the three elements mentioned above, zirconium can also be used for doping. The basic principle is that the high bond energy of the Zr-O bond creates a rigid lattice framework, suppressing the growth of Mn. 3+ The Jahn-Teller distortion is used to prevent manganese dissolution. Simultaneously, bond length reconstruction optimizes the lithium-ion transport environment, enhancing ion diffusion and electronic conductivity. For example, existing literature 4 (Lim S, Kang Y, Jung JW, et al. Anti-dissolution framework strategy for stabilizing high-Mn olivine cathodes via Zr doping[J]. Journal of Energy Storage, 2025, 138: 118509.) uses an ethylene glycol-based solvothermal method to prepare zirconium-doped LMFP (Zr-1), achieving a discharge capacity of 125.9 mA hg after 200 cycles at 1 C current density. −1 It dropped to 116.0 mA hg −1 The existing technology achieves a capacity retention rate of 92.1%. This technology demonstrates that strong Zr-O bonds lead to a decrease in Tm-O bond distance and an increase in Li-O bond length, thereby improving structural stability and promoting lithium-ion diffusion. However, due to the use of a solvothermal method, the basic microstructure of LMFP is a rod-like structure. This rod-like morphology results in gaps formed by overlapping particles, indicating poor interparticle contact. This manifests macroscopically as increased contact resistance. Therefore, to address this issue, carbon coating is used to improve the conductivity of the composite material. However, this operation directly leads to two new technical problems:

[0007] 1. First, the carbon coating process inevitably increases the complexity and cost of the process;

[0008] 2. Secondly, since the basic microstructure of LMFP is rod-shaped, the carbon source accumulates in the interparticle spaces and at the edges of the rod-shaped particles during the carbon coating process, resulting in an excessively thick and dense carbon layer. At the same time, the carbon layer in the surface depression areas and on the surface of the rod is thin and has incomplete coating. In other words, it is impossible to achieve a uniform and complete conductive carbon layer coating. Ultimately, during the expansion and contraction of the battery during repeated charging and discharging, the carbon layer cracks and falls off, further damaging the integrity of the conductive network and causing performance degradation in the later stages of cycling. Summary of the Invention

[0009] The purpose of this invention is to provide a zirconium-doped lithium manganese iron phosphate cathode material, its preparation method, and its applications. The technical principles and specific technical effects of this invention address the technical problems existing in the prior art in the following two aspects:

[0010] 1. Preparation of Mn with uniform composition and regular grains by a controllable hydrothermal process 0.6 Fe 0.4 The PO4 precursor solves the problem of rod-shaped abnormal morphology caused by the traditional solvothermal method for direct preparation of doped materials, eliminating the problems of particle overlap gaps, loose contact and high contact resistance from the source;

[0011] 2. An ultrasonic-stirring composite dispersion process using an anhydrous ethanol system is adopted to achieve molecular-level uniform mixing of zirconium source, lithium source and precursor, ensuring uniform solid solution of Zr element in LMFP lattice without segregation or formation of inert impurity phases.

[0012] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0013] A zirconium-doped lithium iron phosphate cathode material is first synthesized by a hydrothermal method using Mn. 0.6 Fe 0.4 The PO4 precursor was then mixed with lithium hydroxide monohydrate and zirconium oxychloride octahydrate, and finally the zirconium-doped lithium manganese iron phosphate cathode material LMFP-Zr was obtained by segmented high-temperature sintering. The basic microstructure of the LMFP-Zr is granular with a size of 200-300 nm.

[0014] A method for preparing a zirconium-doped lithium manganese iron phosphate cathode material includes the following steps:

[0015] Step 1, Mn 0.6 Fe 0.4To prepare the PO4 precursor, FeSO4·7H2O and MnSO4·H2O were first added to deionized water and stirred to obtain mixture A. Then, H3PO4 was added dropwise to mixture A while stirring to obtain mixture B. Mixture B was then subjected to a hydrothermal reaction. After the reaction was complete, the resulting product was centrifuged, washed, and dried to obtain MnSO4. 0.6 Fe 0.4 PO4;

[0016] In step 1, the molar ratio of FeSO4·7H2O, MnSO4·H2O and H3PO4 is 0.4:0.6:1;

[0017] In step 1, the hydrothermal reaction conditions are: hydrothermal temperature 180℃, hydrothermal time 12 h; the centrifugal washing conditions are: centrifugal speed 5000-6000 rpm, centrifugation time 5 min, centrifugal washing 3 times, and centrifugal washing solution: first washing with deionized water, then washing with anhydrous ethanol; the drying conditions are: drying temperature 60℃, drying time 12 h.

[0018] Step 2, Synthesis of LMFP-Zr: First, the Mn obtained in Step 1 is... 0.6 Fe 0.4 PO4, LiOH·H2O and ZrOCl2·8H2O were added to anhydrous ethanol to obtain a mixture C. Then, the mixture was dispersed by first sonication and then stirring. After dispersion, the solution was filtered, dried and ground to obtain a mixture D. Finally, the mixture D was sintered under argon atmosphere using a segmented sintering method to obtain zirconium-doped lithium manganese iron phosphate cathode material LMFP-Zr.

[0019] In step 2, Mn 0.6 Fe 0.4 The mass ratio of PO4, LiOH·H2O and ZrOCl2·8H2O is 1:0.26:0.0126;

[0020] In step 2, the method of first sonicating and then stirring is as follows: under room temperature conditions, the ultrasonic power is 1500-1600 W, the ultrasonic dispersion time is 10 min, the stirring speed is 500-600 rpm, and the stirring time is 2 h.

[0021] In step 2, the filtration conditions are as follows: the filtration membrane is a 0.45 nm organic membrane; the drying conditions are as follows: the drying temperature is 60℃ and the drying time is 12 h.

[0022] In step 2, the segmented sintering method is as follows: the conditions for the first segment sintering are a heating rate of 5℃ / min, a sintering temperature of 350℃, and a sintering time of 2 h; the conditions for the second segment sintering are a heating rate of 3℃ / min, a sintering temperature of 650℃, and a sintering time of 10 h.

[0023] When used as a cathode material in lithium-ion batteries, at 1 C = 170 mA hg -1 Under test conditions of 2.5-4.5V and a current density of 1C, the initial discharge specific capacity is 130-135 mA hg. -1 When the number of cycles is 200, the residual discharge specific capacity is 120-125 mA hg. -1 The capacity retention rate is 90-92%.

[0024] The technical effects of this invention have been tested and are as follows:

[0025] EDS test results show that LMFP-1%Zr contains zirconium, manganese, phosphorus, iron and oxygen.

[0026] XRD results show that LMFP-1%Zr only has characteristic peaks of lithium manganese iron phosphate and no characteristic peaks related to Zr. However, the (131) diffraction peak shows a shift towards larger angles, which indicates that Zr... 4+ It is incorporated into the crystal lattice.

[0027] SEM test results show that the microstructure of LMFP-1%Zr is a granular structure with a size of 200-300 nm.

[0028] CV test results show that the battery assembled by LMFP-1%Zr has two active sites, Fe and Mn, and exhibits electrochemical reversibility.

[0029] Cyclic charge-discharge test results show that the battery assembled with LMFP-1%Zr can operate at 1 C = 170 mA hg. -1 Under test conditions of 2.5-4.5 V voltage range and 1 C current density, the initial discharge specific capacity is 130-135 mA hg. -1 When the number of cycles is 200, the residual discharge specific capacity is 120-125 mA hg. -1 The capacity retention rate is 90-92%.

[0030] Therefore, the present invention has the following advantages over the prior art:

[0031] 1. This invention achieves uniform and stable solid solution of Zr element in LMFP lattice by optimizing the precursor preparation and solid-phase segmented sintering process. XRD test confirms that the material retains only the characteristic peaks of pure lithium manganese iron phosphate and no zirconium-based inert impurity phases are precipitated.

[0032] 2. The microstructure is regular and controllable, reducing contact resistance from the source without the need for carbon coating modification. The LMFP-1%Zr prepared by this invention has a uniform granular structure of 200-300 nm, with uniform particle size and dense packing.

[0033] 3. High initial capacity, excellent long-term cycling stability, and slow capacity decay rate. The electrochemical performance of the modified LMFP-1%Zr cathode material of this invention is superior to most conventional doped modified LMFP materials. Attached Figure Description

[0034] Figure 1 This is the EDS diagram of LMFP-1%Zr in Embodiment 1 of the present invention;

[0035] Figure 2 XRD patterns of LMFP-1%Zr, LMFP, LMFP-0.5%Zr, and LMFP-2.0%Zr in Comparative Examples 1, 2, and 3 of this invention, for Example 1 of the present invention;

[0036] Figure 3 This is a SEM image of LMFP-1%Zr in Embodiment 1 of the present invention;

[0037] Figure 4 This is a SEM image of the LMFP in Comparative Example 1 of this invention;

[0038] Figure 5 The CV plot of LMFP-1%Zr in Embodiment 1 of the present invention;

[0039] Figure 6 This is a charge-discharge cycle diagram of LMFP-1%Zr, LMFP, LMFP-0.5%Zr, and LMFP-2.0%Zr in Embodiment 1 of the present invention, and Comparative Examples 1, 2, and 3, for 200 cycles. Detailed Implementation

[0040] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0041] Example 1

[0042] A method for preparing a zirconium-doped lithium manganese iron phosphate cathode material includes the following steps:

[0043] Step 1, Mn 0.6 Fe 0.4To prepare the PO4 precursor, firstly, 1.602 g of FeSO4·7H2O and 1.66 g of MnSO4·H2O were added to 60 mL of deionized water and stirred to obtain mixture A. Then, 1.23 mL of H3PO4 was added dropwise to mixture A and stirred to obtain mixture B. Next, mixture B was subjected to a hydrothermal reaction. After the reaction was complete, the product was centrifuged, washed, and dried to obtain MnSO4. 0.6 Fe 0.4 PO4;

[0044] In step 1, the hydrothermal reaction conditions are: hydrothermal temperature 180℃ and hydrothermal time 12 h; the centrifugal washing conditions are: centrifugal speed 6000 rpm, centrifugal time 5 min, centrifugal washing 3 times, and centrifugal washing solution is: first washing with deionized water, then washing with anhydrous ethanol; the drying conditions are: drying temperature 60℃ and drying time 12 h.

[0045] Step 2, Synthesis of LMFP-1%Zr: First, 1.00 g of Mn obtained in Step 1 was... 0.6 Fe 0.4 PO4, 0.26 g LiOH·H2O and 0.0126 g ZrOCl2·8H2O were added to 30 mL of anhydrous ethanol to obtain mixture C. Then, the mixture was dispersed by ultrasonication followed by stirring. After dispersion, the solution was filtered, dried and ground to obtain mixture D. Finally, mixture D was sintered under argon atmosphere using a segmented sintering method to obtain zirconium-doped lithium manganese iron phosphate cathode material. Because the zirconium doping amount is 1 wt.%, it is simply referred to as LMFP-1%Zr.

[0046] In step 2, the method of first sonicating and then stirring is as follows: under room temperature conditions, the ultrasonic power is 1500 W, the ultrasonic dispersion time is 10 min, the stirring speed is 600 rpm, and the stirring time is 2 h.

[0047] In step 2, the filtration conditions are as follows: the filtration membrane is a 0.45 nm organic membrane; the drying conditions are as follows: the drying temperature is 60℃ and the drying time is 12 h.

[0048] In step 2, the segmented sintering method is as follows: the conditions for the first segment sintering are a heating rate of 5℃ / min, a sintering temperature of 350℃, and a sintering time of 2 h; the conditions for the second segment sintering are a heating rate of 3℃ / min, a sintering temperature of 650℃, and a sintering time of 10 h.

[0049] To verify the zirconium doping status and composition of LMFP-1%Zr, EDS and XRD tests were performed.

[0050] EDS test results are as follows Figure 1 As shown, LMFP-1%Zr contains zirconium, manganese, phosphorus, iron, and oxygen.

[0051] XRD test results are as follows Figure 2 As shown, LMFP-1%Zr only exhibits characteristic peaks of lithium manganese iron phosphate and no characteristic peaks related to Zr. However, the (131) diffraction peak shows a shift towards larger angles, indicating that Zr... 4+ It is incorporated into the crystal lattice.

[0052] To demonstrate the microstructure of LMFP-1%Zr, SEM testing was performed. The test results are as follows: Figure 3 As shown, the microstructure of LMFP-1%Zr is a granular structure with a size of 200-300 nm.

[0053] To demonstrate the performance of LMFP-1%Zr as a cathode material for lithium-ion batteries, lithium-ion batteries were assembled and their electrochemical performance was tested.

[0054] The specific method for assembling a lithium-ion battery is as follows: First, the sample to be tested is ground with conductive carbon black and PVDF at a mass ratio of 8:1:1 and a grinding time of 30 min. The LMFP-1%Zr composite material is obtained by conventional melt diffusion method. The LMFP-1%Zr composite material is used as the positive electrode, and the lithium sheet is used as the negative electrode. The diameter of the electrode sheet is 9 mm. Celgard 2500 is used as the separator. The lithium salt concentration in the electrolyte is 1 M LiFP6. The solvent in the electrolyte is a mixture of EC, DMC and EMC. The volume ratio of EC:DMC:EMC is 1:1:1. The additive in the electrolyte is 1.0% VC. Since there is no need to distinguish them, the resulting lithium-ion battery is referred to as the positive electrode active material. That is, the lithium-ion battery obtained by Specific Example 1 based on LMFP-1%Zr as the positive electrode material is also named LMFP-1%Zr.

[0055] The CV test results of LMFP-1%Zr are as follows: Figure 5 As shown, the test voltage range is 2.5-4.5 V, and the scan rate range is 0.1-0.5 mV / s. -1 At that time, the curve showed two sets of symmetrical and independent redox peaks, and both sets of peaks exhibited a "Gaussian-like" distribution with good peak shape symmetry. The test results indicate the presence of two active sites, Fe and Mn, and that the electrochemical reversibility is present.

[0056] The cyclic charge-discharge test results of LMFP-1%Zr are as follows: Figure 6 As shown, at 1 C = 170 mA hg -1Under test conditions of 2.5-4.5 V voltage range and 1 C current density, the initial discharge specific capacity was 134.98 mA hg. -1 At 200 cycles, the remaining discharge specific capacity is 123.72 mA hg. -1 The capacity retention rate was 91.6%.

[0057] To demonstrate the effect of zirconium doping on performance, Comparative Example 1 is provided: lithium manganese iron phosphate cathode material without zirconium doping.

[0058] Comparative Example 1

[0059] A method for preparing a lithium manganese iron phosphate cathode material, the steps of which are not specifically described are the same as those in Example 1, except that ZrOCl2·8H2O is not added in step 2, and the resulting cathode material and lithium-ion battery are named LMFP.

[0060] To confirm the composition of LMFP, XRD tests were performed. The test results are as follows: Figure 2 As shown, LMFP also only has characteristic peaks of lithium manganese iron phosphate and no characteristic peaks of Zr. However, unlike Example 1, (131) the diffraction peak does not shift to a large angle.

[0061] To demonstrate the microstructure of LMFP, SEM testing was performed. The test results are as follows: Figure 4 As shown, the basic microstructure of LMFP is not substantially different from that of LMFP-1%Zr, that is, it is a granular structure with a single particle size of 200-300 nm.

[0062] The cyclic charge-discharge test results of LMFP are as follows: Figure 6 As shown, under test voltage range of 2.5-4.5 V and current density of 1 C, the initial discharge specific capacity is only 98.80 mA hg. -1 It is only 73.2% of that in Example 1; after 200 cycles, the remaining discharge specific capacity is only 81.1 mA hg. -1 The capacity retention rate was only 82.08%. Compared with Example 1, it can be seen that doping with zirconium can significantly improve the initial discharge specific capacity and cycle performance.

[0063] To demonstrate the effect of zirconium doping amount on performance, Comparative Examples 2 and 3 are provided, with zirconium-doped lithium manganese iron phosphate cathode materials having doping amounts of 0.5 wt.% and 2 wt.%, respectively.

[0064] Comparative Example 2

[0065] A method for preparing a zirconium-doped lithium manganese iron phosphate cathode material with a doping amount of 0.5 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that in step 2, the mass of ZrOCl2·8H2O is 0.0063 g, and the resulting cathode material and lithium-ion battery are named LMFP-0.5%Zr.

[0066] To confirm the composition of LMFP-0.5%Zr, XRD tests were performed. The test results are as follows: Figure 2 As shown, LMFP-0.5%Zr also only has the characteristic peak of lithium manganese iron phosphate and no characteristic peak of Zr. However, although the (131) diffraction peak is shifted to a larger angle, compared with Example 1, the shift is smaller than that of LMFP-1%Zr.

[0067] The cyclic charge-discharge test results of LMFP-0.5%Zr are as follows: Figure 6 As shown, under test conditions of a voltage range of 2.5-4.5 V and a current density of 1 C, the initial discharge specific capacity is only 118.70 mA hg. -1 It is only 87.9% of that in Example 1; after 200 cycles, the remaining discharge specific capacity is only 108.23 mA hg. -1 The capacity retention rate was only 91.17%. Compared with Comparative Example 1 and Example 1, it can be seen that when the zirconium doping amount is too small, although the initial discharge specific capacity and cycle performance can be improved, the improvement is much lower than that of LMFP-1%Zr.

[0068] Comparative Example 3

[0069] A method for preparing a zirconium-doped lithium manganese iron phosphate cathode material with a doping amount of 2 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that in step 2, the mass of ZrOCl2·8H2O is 0.0252 g, and the resulting cathode material and lithium-ion battery are named LMFP-2%Zr.

[0070] To confirm the composition of LMFP-2%Zr, XRD tests were performed. The test results are as follows: Figure 2 As shown, LMFP-2%Zr also only has the characteristic peak of lithium manganese iron phosphate and no characteristic peak of Zr. However, not only does the (131) diffraction peak show a shift to a larger angle, but compared with Example 1, the shift is greater than that of LMFP-1%Zr.

[0071] The cyclic charge-discharge test results of LMFP-2%Zr are as follows: Figure 6As shown, under test voltage ranges of 2.5–4.5 V and current densities of 1 C, the initial discharge specific capacity is only 108.39 mA hg. -1 It is only 80.3% of that in Example 1; after 200 cycles, the remaining discharge specific capacity is only 98.40 mA hg. -1 The capacity retention rate was 90.8%. Compared with Example 1, it can be seen that when the zirconium doping amount is too high, the initial discharge specific capacity and cycle performance actually deteriorate.

Claims

1. A zirconium-doped lithium iron phosphate cathode material, characterized in that: First, Mn was synthesized via a hydrothermal method. 0.6 Fe 0.4 The PO4 precursor was then mixed with lithium hydroxide monohydrate and zirconium oxychloride octahydrate, and finally the zirconium-doped lithium manganese iron phosphate cathode material LMFP-Zr was obtained by segmented high-temperature sintering. The basic microstructure of the LMFP-Zr is granular with a size of 200-300 nm.

2. A method for preparing a zirconium-doped lithium manganese iron phosphate cathode material, characterized in that... Includes the following steps: Step 1, Mn 0.6 Fe 0.4 To prepare the PO4 precursor, FeSO4·7H2O and MnSO4·H2O were first added to deionized water and stirred to obtain mixture A. Then, H3PO4 was added dropwise to mixture A while stirring to obtain mixture B. Mixture B was then subjected to a hydrothermal reaction. After the reaction was complete, the resulting product was centrifuged, washed, and dried to obtain MnSO4. 0.6 Fe 0.4 PO4; Step 2, Synthesis of LMFP-Zr: First, the Mn obtained in Step 1 is... 0.6 Fe 0.4 PO4, LiOH·H2O and ZrOCl2·8H2O were added to anhydrous ethanol to obtain a mixture C. Then, the mixture was dispersed by first sonication and then stirring. After dispersion, the solution was filtered, dried and ground to obtain a mixture D. Finally, the mixture D was sintered under argon atmosphere using a segmented sintering method to obtain zirconium-doped lithium manganese iron phosphate cathode material LMFP-Zr.

3. The preparation method according to claim 2, characterized in that: In step 1, the molar ratio of FeSO4·7H2O, MnSO4·H2O and H3PO4 is 0.4:0.6:1; In step 1, the hydrothermal reaction conditions are: hydrothermal temperature 180℃ and hydrothermal time 12 h; the centrifugal washing conditions are: centrifugal speed 5000-6000 rpm, centrifugation time 5 min, centrifugal washing 3 times, and centrifugal washing solution is: first washing with deionized water, then washing with anhydrous ethanol; the drying conditions are: drying temperature 60℃ and drying time 12 h.

4. The preparation method according to claim 2, characterized in that: In step 2, Mn 0.6 Fe 0.4 The mass ratio of PO4, LiOH·H2O and ZrOCl2·8H2O is 1:0.26:0.0126; In step 2, the method of first sonicating and then stirring is as follows: under room temperature conditions, the ultrasonic power is 1500-1600 W, the ultrasonic dispersion time is 10 min, the stirring speed is 500-600 rpm, and the stirring time is 2 h. In step 2, the filtration conditions are as follows: the filtration membrane is a 0.45 nm organic membrane; the drying conditions are as follows: the drying temperature is 60℃ and the drying time is 12 h. In step 2, the segmented sintering method is as follows: the conditions for the first segment sintering are a heating rate of 5℃ / min, a sintering temperature of 350℃, and a sintering time of 2 h; the conditions for the second segment sintering are a heating rate of 3℃ / min, a sintering temperature of 650℃, and a sintering time of 10 h.

5. The zirconium-doped lithium iron phosphate cathode material according to claim 1, characterized in that: When used as a cathode material in lithium-ion batteries, at 1 C = 170 mA hg -1 Under test conditions of 2.5-4.5 V voltage range and 1 C current density, the initial discharge specific capacity is 130-135 mA hg. -1 When the number of cycles is 200, the remaining discharge specific capacity is 120-125 mAh g. -1 The capacity retention rate is 90-92%.

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