CN104852046B - Nanometer piece shaped LMFP material, and manufacturing method and application thereof - Google Patents

Abstract

The invention discloses a nano-sheet-shaped lithium manganese iron phosphate material, which is composed of sheet-like structure LiFe _0.1 Mn _0.9 PO ₄ , and Fe is evenly distributed in the lattice position of Mn, and the sheet-like structure of LiFe _0.1 Mn _0.9 PO ₄ presents a cuboid shape with a size of nanometers, the length and width of which are both less than 100 nanometers, and the thickness is less than 20 nanometers. The present invention prepares the LiFe _0.1 Mn _0.9 PO ₄ material with a nanosheet structure and LiFePO ₄ /LiMnPO ₄ in solid solution through a small amount of iron doping (10%) and by optimizing the synthesis process. The material has excellent Excellent high current cycle stability and rate performance. The preparation method has simple and controllable process, low energy consumption and low cost, and is suitable for large-scale industrial production.

Description

Nano-flaky lithium manganese iron phosphate material and its preparation method and application

technical field

The invention relates to the technical field of positive electrode materials for lithium ion batteries, in particular to a nanosheet-shaped lithium manganese iron phosphate material and a preparation method and application thereof.

Background technique

Lithium-ion batteries have the advantages of high working voltage, high energy density, and good safety performance. Therefore, they are widely used in portable electronic products such as digital cameras, mobile phones, and notebook computers. They also have application prospects for electric bicycles and electric vehicles. Lithium-ion batteries currently commercialized generally use lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), and lithium iron phosphate (LiFePO ₄ ) as positive electrode materials. Among the above materials, LiFePO ₄ material has been used as the positive electrode material for electric vehicle batteries due to its advantages of safety, environmental protection and low price. However, the working voltage of this material is relatively low, only 3.5V, while the working voltage of LiMnPO ₄ , which is also an olive-shaped structure, is 4.1V, which has a higher energy density and has attractive application prospects in electric vehicles. Therefore, in recent years Come get noticed. However, compared with LiFePO ₄ , LiMnPO ₄ has lower electronic conductivity and lithium ion diffusion rate, resulting in poorer electrochemical performance, especially poorer rate performance and cycle stability under high current.

Recent studies have found that substituting part of Mn with Fe (LiF _x Mn _1–x PO ₄ ) can significantly improve the electrochemical performance of LiMnPO ₄ , while a small amount of Fe doping has little effect on the energy density of LiMnPO ₄ .

For example, the Chinese patent document whose publication number is CN104466161A discloses a solid-phase synthesis method of lithium manganese iron phosphate material, after mixing the precursor materials iron source, lithium source, phosphorus source, and manganese source in proportion, adding a dispersant for ball milling, Drying, and performing primary sintering and secondary sintering respectively under a nitrogen protective atmosphere, finally obtaining LiMn _x Fe _1-x PO ₄ material.

As another example, the Chinese patent document with the publication number CN103762362A discloses a hydrothermal preparation method of a nano-lithium manganese iron phosphate cathode material. The precursor is prepared by mixing H ₃ PO ₄ solution and Mix LiOH·H ₂ O; add concentrated ammonia water, the pH value is 9~10; heat up to 180°C, add the molar ratio (Fe+Mn):Ti:P=0.99:0.01:1 into deionized water, and pump the mixed solution into the reaction In the kettle, control the temperature at 170-200°C; heat to 200°C and keep it warm for 7-10 hours; wash and coat with carbon; when cooled to below 60°C, wash with deionized water until there are no sulfate groups, and add soluble organic matter carbon source, Spray drying, heat treatment for 7 to 10 hours, and cooling to obtain LiMn _x Fe _0.99-x Ti _0.01 PO ₄ powder.

However, the lithium manganese iron phosphate material prepared by the above method still faces challenges. One of the disadvantages is that the structure is unstable, the capacity decays quickly after repeated charge and discharge, and the rate performance is not ideal.

Contents of the invention

The present invention prepares the LiFe _0.1 Mn _0.9 PO ₄ material with a nanosheet structure and LiFePO ₄ /LiMnPO ₄ in solid solution through a small amount of iron doping (10%) and by optimizing the synthesis process. The material has excellent Excellent high current cycle stability and rate performance. The preparation method has simple and controllable process, low energy consumption and low cost, and is suitable for large-scale industrial production.

A nano-sheet-like lithium manganese iron phosphate material, which is composed of sheet-like structure LiFe _0.1 Mn _0.9 PO ₄ , and Fe is evenly distributed in the lattice position of Mn, and the sheet-like structure of LiFe _0.1 Mn _0.9 PO ₄ presents a cuboid shape , the size is nanoscale, the length and width are less than 100 nanometers, and the thickness is less than 20 nanometers.

Preferably, the length and width of the sheet-like LiFe _0.1 Mn _0.9 PO ₄ are 40-100 nanometers, and the thickness is 10-20 nanometers.

In the sheet-like structure of LiFe _0.1 Mn _0.9 PO ₄ , Fe is evenly distributed in the lattice positions of Mn, that is, LiFePO ₄ /LiMnPO ₄ in LiFe _0.1 Mn _0.9 PO ₄ is in a solid solution state. Due to its unique nanosheet structure and solid solution of LiFePO ₄ /LiMnPO ₄ , it is beneficial to electron conduction, lithium ion insertion/extraction, electrolyte infiltration and structural stability.

The present invention also discloses a preparation method of the nanosheet lithium manganese iron phosphate material, comprising the following steps:

1) Prepare LiOH/ethylene glycol solution I and H ₃ PO ₄ /ethylene glycol solution I respectively, and mix them to obtain a suspension a1; mix MnSO ₄ with a mixed solvent of ethylene glycol/deionized water to obtain a solution b1; Then drop the solution b1 into the solution a1 drop by drop, and stir evenly to obtain the solution c1;

2) Prepare LiOH/ethylene glycol solution II and H ₃ PO ₄ /ethylene glycol solution II respectively, and mix them to obtain suspension a2; mix FeSO ₄ and ethylene glycol to obtain solution b2; then add solution b2 drop by drop into solution a2, and stir to obtain solution c2;

3) Add the solution c2 dropwise into the solution c1, stir evenly to obtain a precursor solution, and obtain the nanosheet-shaped lithium manganese iron phosphate material through solvothermal reaction and post-treatment.

The present invention prepares and synthesizes the precursor solutions of LiMnPO ₄ and LiFePO ₄ respectively, and then mixes the two for solvothermal reaction. Through the optimization of the preparation process, LiFe _0.1 Mn _0.9 PO ₄ materials with flake nanostructures are prepared, which is conducive to the formation of LiFePO ₄ /LiMnPO ₄ solid solution structure, and it is beneficial to inhibit the growth of LiFe _0.1 Mn _0.9 PO ₄ grains, and the use of nano-sheet structure and LiFePO ₄ /LiMnPO ₄ solid solution can significantly improve the electronic conductance of LiFe _0.1 Mn _0.9 PO ₄ rate, lithium ion diffusion rate and structural stability, thereby improving the electrochemical performance of LiFe _0.1 Mn _0.9 PO ₄ materials, especially high-current cycle stability and rate performance, and opening up for the improvement of electrochemical performance of LiFe _0.1 Mn _0.9 PO ₄ materials a new way. However, when the precursor of LiFe _0.1 Mn _0.9 PO ₄ is synthesized by the conventional one-pot method, the solvothermal reaction will cause the growth of LiFe _0.1 Mn _0.9 PO ₄ grains and the phase separation of LiFePO ₄ /LiMnPO ₄ , resulting in Deterioration of electrochemical performance.

Preferably, in step 1), the molar concentration of the LiOH/ethylene glycol solution I is 1-4 mol/L, and the molar ratio of MnSO ₄ , H ₃ PO ₄ to LiOH is 1:1.1-1.16:3. It is further preferable that the molar concentration of LiOH/ethylene glycol solution I is 2-3 mol/L, too low concentration is not conducive to the crystallization of LiFe _0.1 Mn _0.9 PO ₄ , and too high concentration will cause insufficient dissolution of LiOH and incomplete chemical reaction.

As preferably, in step 1), in the mixed solvent, the volume ratio of ethylene glycol to deionized water is 1:1;

The volume ratio of the LiOH/ethylene glycol solution I, the H ₃ PO ₄ /ethylene glycol solution I to the solution b1 is 1:1:1.

As a preference, in step 2), the molar concentration of the LiOH/ethylene glycol solution II is 1/9 of the molar concentration of the LiOH/ethylene glycol solution I, and the molar concentration of the H ₃ PO ₄ /ethylene glycol solution II is 1/9 of the molar concentration _of H3PO4/ethylene glycol solution I, the molar concentration of _FeSO4 in solution b2 is 1/9 of the molar concentration of _MnSO4 in solution b1 _;

The volume ratio of the LiOH/ethylene glycol solution II, the H ₃ PO ₄ /ethylene glycol solution II and the solution b2 is 1:1:1.

Preferably, in step 3), solution c1 and solution c2 are mixed in equal volumes.

Preferably, in step 3), the solvothermal reaction is carried out at 140-170° C. for 6-9 hours. More preferably, the solvothermal reaction is carried out at 160-170° C. for 8-9 hours. The study found that the higher the reaction temperature and the longer the time, the better the crystallinity of LiFe _0.1 Mn _0.9 PO ₄ , but too high temperature (such as ≥180°C) and too long reaction time (such as ≥10h) will cause LiFe The obvious growth of _0.1 Mn _0.9 PO ₄ grains leads to the deterioration of electrochemical performance.

The post-treatment includes cooling precipitation, centrifugation and drying. The cooling temperature is not strictly limited, and it is mainly based on suitable operation. Generally, it can be cooled to an ambient temperature of 15-30°C.

The sheet-like LiFe _0.1 Mn _0.9 PO ₄ material prepared above has good electrochemical performance, especially high-current cycle stability and rate performance, so it can be used or prepared as anode material for lithium-ion batteries.

Compared with prior art, the present invention has following advantage:

1. The present invention adopts low-temperature liquid phase method to prepare LiFe _0.1 Mn _0.9 PO ₄ material, which has the advantages of simple and controllable process, low cost, short cycle, low energy consumption and suitable for industrial production.

2. The LiFe _0.1 Mn _0.9 PO ₄ material prepared by the present invention has a sheet-like nanostructure, which is beneficial to electron conduction, lithium ion insertion/extraction, and electrolyte infiltration, so it is beneficial to the improvement of the electrochemical performance of the material, especially the rate performance .

3. The LiFe _0.1 Mn _0.9 PO ₄ material prepared by the present invention, due to its flake structure and solid solution structure of LiFePO ₄ /LiMnPO ₄ , exhibits relatively high structural stability during charging and discharging, and therefore has high cycle stability properties, especially high-current cycle stability, and can be used or prepared as anode materials for lithium-ion batteries.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the _{LiFe0.1Mn0.9PO4} material that embodiment _{1 prepares} ;

Fig. 2 is the scanning electron _micrograph of the _{LiFe0.1Mn0.9PO4} material that embodiment ₁ prepares;

Fig. 3 is the transmission electron microscope picture of the _{LiFe0.1Mn0.9PO4} material that embodiment _{1 prepares} ;

Fig. ₄ is the element distribution figure of Mn and _Fe in the _{LiFe0.1Mn0.9PO4} that embodiment 1 prepares;

Fig. 5 is respectively with embodiment 1 (A), the LiFe _0.1 Mn _0.9 PO material prepared by comparative example ₁ (B) The electrochemical performance figure of the lithium-ion battery assembled as positive electrode material;

Figure a is the cycle performance diagram, and picture b is the rate performance diagram;

FIG. 6 is a scanning electron micrograph of the LiFe _0.1 Mn _0.9 PO ₄ material prepared in Comparative Example 1.

detailed description

Example 1

Dissolve 0.027mol LiOH in 10mL ethylene glycol, stir well to obtain a LiOH solution with a concentration of 2.7mol/L, dissolve 0.0099mol H ₃ PO ₄ in 10mL ethylene glycol, and stir well to obtain a H ₃ PO ₄ solution , then add the H ₃ PO ₄ solution dropwise into the LiOH solution, stir evenly to obtain a suspension a1; dissolve 0.009mol MnSO ₄ in a mixed solvent of 5mL ethylene glycol and 5mL deionized water to obtain a solution b1, and then Drop b1 into a1 drop by drop, stir evenly to obtain solution c1; dissolve 0.003mol LiOH in 10mL ethylene glycol, stir well to obtain LiOH solution, dissolve 0.0011mol H ₃ PO ₄ in 10mL ethylene glycol, stir homogeneously to obtain H ₃ PO ₄ solution, then add H ₃ PO ₄ solution dropwise into LiOH solution, stir evenly to obtain suspension a2; dissolve 0.001mol FeSO ₄ in 10mL ethylene glycol to obtain solution b2, and then Drop b2 into a2 dropwise and stir evenly to obtain solution c2; drop c2 into c1 dropwise and stir evenly to obtain a precursor solution, then seal the precursor solution in a reaction kettle and react at 170°C for 9 Hours, the precipitate was obtained by cooling, and then centrifuged and dried to obtain LiFe _0.1 Mn _0.9 PO ₄ nanosheets.

The X-ray diffraction pattern, scanning electron micrograph, and transmission electron micrograph of the obtained material are shown in Figure 1, Figure 2 and Figure 3, respectively, where the X-ray diffraction peak can be attributed to LiFe _0.1 Mn _0.9 PO ₄ . It is known from the scanning electron microscope and the transmission electron microscope that the obtained material presents a flake structure and a cuboid shape, the length and width of which are 40-100 nanometers, and the thickness is 10-20 nanometers. The elemental distribution of Mn and Fe of the obtained material is shown in Fig. 4. It can be seen from the figure that the Fe element is uniformly dispersed in the Mn lattice, that is, LiFePO ₄ /LiMnPO ₄ is in a solid solution state.

The LiFe _0.1 Mn _0.9 PO ₄ material was subjected to carbon coating treatment before the electrochemical test (mixed LiFe _0.1 Mn _0.9 PO ₄ and glucose at a mass ratio of 2:1, and reacted for 4 hours at 600 °C under an argon atmosphere to obtain LiFe _0.1 Mn _0.9 PO ₄ /C composite, the composite contains 9wt% carbon, and maintains a sheet-like nanostructure). The obtained carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets were used as the positive electrode material of lithium-ion batteries for electrochemical performance testing (constant current charge and discharge within a certain voltage range), and the cycle performance diagram of the obtained material is shown in Figure 5a (curve A ), constant current charge and discharge (current density 1C = 170mA/g, voltage range 2 ~ 4.5V) tests show that when the number of cycles is 1, the capacity of carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets is 140mAh/g, When the number of cycles is 100, the capacity of the material remains at 130mAh/g, showing higher capacity and better cycle performance. The rate performance diagram of the obtained material is shown in Figure 5b (curve A). It can be seen from the figure that the material also has excellent rate performance, and the capacity is still close to 120mAh/g at 10C.

Comparative example 1

The precursor solution for the synthesis of LiFe _0.1 Mn _0.9 PO ₄ was prepared by a one-pot method. Dissolve 0.03mol LiOH in 20mL of ethylene glycol, stir evenly to obtain a LiOH solution with a concentration of 3mol/L, dissolve 0.011mol H ₃ PO ₄ in 20mL of ethylene glycol, and stir evenly to obtain a H ₃ PO ₄ solution, Then add the H ₃ PO ₄ solution dropwise into the LiOH solution and stir evenly to obtain a suspension a3; dissolve 0.009mol MnSO ₄ and 0.001mol FeSO ₄ in a mixed solvent of 15mL ethylene glycol and 5mL deionized water to obtain a solution b3, then drop b3 into a3 drop by drop, stir evenly to obtain solution c3; then seal the precursor solution in the reaction kettle, react at 170°C for 9 hours, obtain a precipitate after cooling, and then centrifuge and dry to obtain _{LiFe0.1Mn0.9PO4 nanosheets .}

The X-ray diffraction pattern of the obtained material can be attributed to LiFe _0.1 Mn _0.9 PO ₄ . From the scanning electron microscope photo in Figure 6, it can be seen that the obtained material has an irregular shape, most of the particle size is greater than 100 nanometers, and the thickness is greater than 20 nanometers. The element distribution analysis of Mn and Fe shows that LiFePO ₄ /LiMnPO ₄ presents a phase-separated structure.

Similar carbon encapsulation and electrochemical tests were carried out on the LiFe _0.1 Mn _0.9 PO ₄ nanosheets obtained above. The test results show that the electrochemical performance of LiFe _0.1 Mn _0.9 PO ₄ prepared by this process is obviously inferior to that of Example 1. When charging and discharging at a constant current of 1C, the capacity of carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets is 118mAh/g when the number of cycles is 1, and the capacity of the material is only 102mAh/g when the number of cycles is 100, see Figure 5a (curve B). The rate performance graph of the obtained material is shown in Figure 5b (curve B). It can be seen from the figure that the capacity is only 71mAh/g at 10C. It can be seen that the precursor preparation process during synthesis affects the structure and electrochemical properties of the product. It also shows that the synthetic technique of the present invention is reasonable.

Comparative example 2

The method of Example 1 prepares undoped LiMnPO ₄ , that is, in the process of preparing the b2 solution, FeSO ₄ is not used, but MnSO ₄ is used, and the solvent used is a mixed solvent of 5 mL ethylene glycol and 5 mL deionized water. Other steps same. Carbon coating and electrochemical tests were performed in a similar manner. The method can be used to prepare pure-phase flake LiMnPO ₄ , which is in the shape of a cuboid, with a length and width of 40-100 nanometers and a thickness of 10-20 nanometers. Electrochemical tests show that the cycle stability and rate performance of carbon-coated LiMnPO ₄ are inferior to those of Fe-doped LiMnPO ₄ . This indicates that doping Fe can improve the cycle stability and rate performance of LiMnPO4 _.

Example 2

Dissolve 0.027mol LiOH·H ₂ O in 10mL of ethylene glycol, stir evenly to obtain a LiOH solution with a concentration of 2.7mol/L, dissolve 0.01008mol H ₃ PO ₄ in 10mL of ethylene glycol, and stir evenly to obtain H ₃ PO ₄ solution, and then add H ₃ PO ₄ solution dropwise into the LiOH solution, and stir evenly to obtain a suspension a1; dissolve 0.009mol MnSO ₄ in a mixed solvent of 5mL ethylene glycol and 5mL deionized water to obtain Solution b1, then drop b1 into a1 drop by drop, stir evenly to get solution c1; dissolve 0.003mol LiOH·H ₂ O in 10mL ethylene glycol, stir evenly to get LiOH solution, add 0.00112mol H ₃ PO ₄ Dissolve in 10mL ethylene glycol, stir evenly to obtain H ₃ PO ₄ solution, then add H ₃ PO ₄ solution dropwise to LiOH solution, stir evenly, obtain suspension a2; dissolve 0.001mol FeSO ₄ in 10mL ethyl alcohol diol to obtain solution b2, then drop b2 into a2 drop by drop, stir evenly to obtain solution c2; drop c2 dropwise into c1, stir evenly to obtain a precursor solution, and then seal the precursor solution in the reaction In the kettle, react at 160°C for 8 hours, cool to obtain a precipitate, and then centrifuge and dry to obtain LiFe _0.1 Mn _0.9 PO ₄ nanosheets.

The X-ray diffraction peak of the obtained material can be attributed to LiFe _0.1 Mn _0.9 PO ₄ . It is known from the scanning electron microscope and the transmission electron microscope that the obtained material presents a flake structure and a cuboid shape, the length and width of which are 40-100 nanometers, and the thickness is 10-20 nanometers. The elemental distribution of Mn and Fe in the obtained material shows that the Fe element is uniformly dispersed in the Mn lattice, that is, LiFePO ₄ /LiMnPO ₄ is in a solid solution state.

The LiFe _0.1 Mn _0.9 PO ₄ material was subjected to carbon coating treatment before the electrochemical test (mixed LiFe _0.1 Mn _0.9 PO ₄ and glucose at a mass ratio of 2:1, and reacted for 4 hours at 600 °C under an argon atmosphere to obtain LiFe _0.1 Mn _0.9 PO ₄ /C composite, the composite contains 9wt% carbon, and maintains a sheet-like nanostructure). The obtained carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets are used as lithium-ion battery cathode materials for electrochemical performance testing (constant current charge and discharge within a certain voltage range), constant current charge and discharge (current density 1C=170mA/g , voltage range 2 ~ 4.5V) test shows that when the number of cycles is 1, the capacity of carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets is 138mAh/g, when the number of cycles is 100, the capacity of the material is still maintained at 126mAh /g, showing higher capacity and better cycle performance. The rate test of the obtained material shows that the material also has excellent rate performance. At 10C, the capacity is still close to 120mAh/g.

Example 3

Dissolve 0.027mol LiOH·H ₂ O in 10mL of ethylene glycol and stir evenly to obtain a LiOH solution with a concentration of 2.7mol/L. Dissolve 0.01026mol H ₃ PO ₄ in 10mL of ethylene glycol and stir evenly to obtain H ₃ PO ₄ solution, then add H ₃ PO ₄ solution dropwise into LiOH solution, stir evenly to obtain suspension a1; dissolve 0.009mol MnSO ₄ ·H ₂ O in 5mL ethylene glycol and 5mL deionized water solvent to obtain solution b1, and then drop b1 into a1 drop by drop, and stir evenly to obtain solution c1; dissolve 0.003mol LiOH·H ₂ O in 10mL ethylene glycol, and stir uniformly to obtain LiOH solution, and mix 0.00114molH ₃ PO ₄ was dissolved in 10mL of ethylene glycol, stirred evenly to obtain H ₃ PO ₄ solution, and then H ₃ PO ₄ solution was added dropwise to LiOH solution, stirred evenly to obtain suspension a2; 0.001mol FeSO ₄ was dissolved In 10mL of ethylene glycol, get solution b2, then drop b2 into a2 drop by drop, stir evenly to get solution c2; drop c2 into c1 drop by drop, stir evenly to get precursor solution, then put the precursor solution Sealed in a reaction kettle, reacted at 165°C for 8.5 hours, cooled to obtain a precipitate, and then centrifuged and dried to obtain LiFe _0.1 Mn _0.9 PO ₄ nanosheets.

The X-ray diffraction peak of the obtained material can be attributed to LiFe _0.1 Mn _0.9 PO ₄ . It is known from the scanning electron microscope and the transmission electron microscope that the obtained material presents a flake structure and a cuboid shape, the length and width of which are 40-100 nanometers, and the thickness is 10-20 nanometers. The elemental distribution of Mn and Fe in the obtained material shows that the Fe element is uniformly dispersed in the Mn lattice, that is, LiFePO ₄ /LiMnPO ₄ is in a solid solution state.

The LiFe _0.1 Mn _0.9 PO ₄ material was subjected to carbon coating treatment before the electrochemical test (mixed LiFe _0.1 Mn _0.9 PO ₄ and glucose at a mass ratio of 2:1, and reacted for 4 hours at 600 °C under an argon atmosphere to obtain LiFe _0.1 Mn _0.9 PO ₄ /C composite, the composite contains 9wt% carbon, and maintains a sheet-like nanostructure). The obtained carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets are used as lithium-ion battery cathode materials for electrochemical performance testing (constant current charge and discharge within a certain voltage range), constant current charge and discharge (current density 1C=170mA/g , voltage range 2 ~ 4.5V) test shows that when the number of cycles is 1, the capacity of carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets is 137mAh/g, when the number of cycles is 100, the capacity of the material is still maintained at 128mAh /g, showing higher capacity and better cycle performance. The rate test of the obtained material shows that the material also has excellent rate performance. At 10C, the capacity is still close to 120mAh/g.

Example 4

Dissolve 0.027mol LiOH in 10mL of ethylene glycol, stir evenly to obtain a LiOH solution with a concentration of 2.7mol/L, dissolve 0.01044mol H ₃ PO ₄ in 10mL of ethylene glycol, and stir evenly to obtain a H ₃ PO ₄ solution , then add the H ₃ PO ₄ solution dropwise into the LiOH solution, and stir evenly to obtain a suspension a1; dissolve 0.009mol MnSO ₄ ·H ₂ O in a mixed solvent of 5mL ethylene glycol and 5mL deionized water to obtain Solution b1, then drop b1 into a1 drop by drop, stir evenly to obtain solution c1; dissolve 0.003mol LiOH in 10mL ethylene glycol, stir evenly to obtain LiOH solution, dissolve 0.00116mol H ₃ PO ₄ in 10mL ethyl alcohol Diol, stir evenly to obtain H ₃ PO ₄ solution, then add H ₃ PO ₄ solution dropwise into LiOH solution, stir evenly, obtain suspension a2; dissolve 0.001mol FeSO ₄ ·7H ₂ O in 10mL diol to obtain solution b2, then drop b2 into a2 drop by drop, stir evenly to obtain solution c2; drop c2 dropwise into c1, stir evenly to obtain a precursor solution, and then seal the precursor solution in the reaction In the kettle, react at 170°C for 8 hours, cool to obtain a precipitate, and then centrifuge and dry to obtain LiFe _0.1 Mn _0.9 PO ₄ nanosheets.

The X-ray diffraction peak of the obtained material can be attributed to LiFe _0.1 Mn _0.9 PO ₄ . It is known from the scanning electron microscope and the transmission electron microscope that the obtained material presents a flake structure and a cuboid shape, the length and width of which are 40-100 nanometers, and the thickness is 10-20 nanometers. The elemental distribution of Mn and Fe in the obtained material shows that the Fe element is uniformly dispersed in the Mn lattice, that is, LiFePO ₄ /LiMnPO ₄ is in a solid solution state.

The LiFe _0.1 Mn _0.9 PO ₄ material was subjected to carbon coating treatment before the electrochemical test (mixed LiFe _0.1 Mn _0.9 PO ₄ and glucose at a mass ratio of 2:1, and reacted for 4 hours at 600 °C under an argon atmosphere to obtain LiFe _0.1 Mn _0.9 PO ₄ /C composite, the composite contains 9wt% carbon, and maintains a sheet-like nanostructure). The obtained carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets are used as lithium-ion battery cathode materials for electrochemical performance testing (constant current charge and discharge within a certain voltage range), constant current charge and discharge (current density 1C=170mA/g , voltage range 2 ~ 4.5V) test shows that when the number of cycles is 1, the capacity of carbon-coated LiFe _0.1 Mn _0.9 PO ₄ nanosheets is 141mAh/g, when the number of cycles is 100, the capacity of the material is still maintained at 131mAh /g, showing higher capacity and better cycle performance. The rate test of the obtained material shows that the material also has excellent rate performance. At 10C, the capacity is still close to 120mAh/g.

Claims (9)

1. a kind of nano-sheet iron manganese phosphate lithium material is it is characterised in that life by laminated structure_0.1mn_0.9po₄Composition, and fe It is uniformly distributed in the lattice position of mn, the life of described laminated structure_0.1mn_0.9po₄Assume cuboid, long and wide size is equal Less than 100 nanometers, thickness is less than 20 nanometers.

2. nano-sheet iron manganese phosphate lithium material according to claim 1 is it is characterised in that described laminated structure life_0.1mn_0.9po₄Length and wide size be 40～100 nanometers, thickness be 10～20 nanometers.

3. a kind of preparation method of nano-sheet iron manganese phosphate lithium material according to claim 1 is it is characterised in that include Following steps:

1) lioh/ ethylene glycol solution and h are prepared respectively₃po₄/ ethylene glycol solution, obtains suspension a1 after mixing；By mnso₄With The mixed solvent mixing of ethylene glycol/deionized water, obtains solution b1；Again solution b1 is dropwise instilled in solution a1, stir Obtain solution c1；

2) lioh/ ethylene glycol solution and h are prepared respectively₃po₄/ ethylene glycol solution, obtains suspension a2 after mixing；By feso₄ Mix with ethylene glycol, obtain solution b2；Again solution b2 is dropwise instilled in solution a2, be uniformly mixing to obtain solution c2；

3) solution c2 is dropwise instilled in solution c1, be uniformly mixing to obtain precursor solution, obtain through solvent thermal reaction and post processing To described nano-sheet iron manganese phosphate lithium material.

4. the preparation method of nano-sheet iron manganese phosphate lithium material according to claim 3 is it is characterised in that step 1) In, the molar concentration of described lioh/ ethylene glycol solution is 1～4mol/l, mnso₄、h₃po₄Mol ratio with lioh is 1:1.1 ～1.16:3.

5. the preparation method of nano-sheet iron manganese phosphate lithium material according to claim 3 is it is characterised in that step 1) In, in described mixed solvent, ethylene glycol is 1:1 with the volume ratio of deionized water；

Described lioh/ ethylene glycol solution, h₃po₄/ ethylene glycol solution is 1:1:1 with the volume ratio of solution b1.

6. the preparation method of nano-sheet iron manganese phosphate lithium material according to claim 3 is it is characterised in that step 2) In, the molar concentration of described lioh/ ethylene glycol solution is the 1/9, h of the molar concentration of lioh/ ethylene glycol solution₃po₄/ second two The molar concentration of alcoholic solution is h₃po₄The 1/9 of the molar concentration of/ethylene glycol solution, feso in solution b2₄Molar concentration be Mnso in solution b1₄Molar concentration 1/9；

Described lioh/ ethylene glycol solution, h₃po₄The volume ratio of/ethylene glycol solution and solution b2 is 1:1:1.

7. the preparation method of nano-sheet iron manganese phosphate lithium material according to claim 3 is it is characterised in that step 3) In, solution c1 is mixed with solution c2 equal-volume.

8. the preparation method of nano-sheet iron manganese phosphate lithium material according to claim 3 is it is characterised in that step 3) In, described solvent thermal reaction reacts 6～9h at 140～170 DEG C.

9. a kind of nano-sheet iron manganese phosphate lithium material according to claim 1 answering in anode material for lithium-ion batteries With.