A LiFe x M 1-x PO4@MoO2 in-situ composite material and preparation and application thereof

Abstract

This invention relates to the field of cathode materials, specifically disclosing a LiFe... x M 1‑x The preparation method of PO4@MoO2 in-situ composite material, which contains LiFe x M 1‑x The mixture of PO4 and ammonium molybdate was heated to temperature T1 under a carrier gas flow and held for the first stage of heat treatment. Then, the carrier gas flow was turned off, and the temperature was further increased to T2 and held for the second stage of heat treatment, thus obtaining the LiFe. x M 1‑x PO4@MoO2 in-situ composite material; wherein M is a transition metal element, and 0

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery materials, and particularly relates to the technical field of positive electrode active materials. BACKGROUND

[0002] Under the increasing prevalence of new energy batteries, the lithium iron phosphate (LFP) positive electrode material has the characteristics of stable structure, excellent charge-discharge platform, high capacity, good cycle performance, safety, non-toxicity, low cost and the like, so that it has an absolute market that cannot be completely replaced. In the past 2022, the LFP positive electrode material has grown rapidly and become the main installed material of vehicle-mounted power batteries, with a market share of more than 60%. However, in the actual application process, the LFP positive electrode material still faces main problems such as low discharge platform, low compaction, insufficient battery energy density and the like. These problems limit its development to some extent. As an iterative product of LFP, lithium manganese iron phosphate (LMFP) has a higher voltage platform, but due to its poor electrical conductivity, the primary particles of the material need to be made smaller, and the surface needs to be coated with more carbon than LFP to improve the electrical conductivity, thus resulting in a too large specific surface area which brings a severe test to the later processing process, and the too small primary particles of the material and the need to coat more carbon on the surface result in insufficient high compaction density, which finally has an important influence on the energy density of the battery. SUMMARY

[0003] The application aims to provide a LiFe x M 1-x PO4@MoO2 in-situ composite material and a preparation method thereof.

[0004] The second purpose of the application is to provide the LiFe x M 1-x PO4@MoO2 in-situ composite material prepared by the preparation method and application thereof in a lithium secondary battery positive electrode active material.

[0005] The third purpose of the application is to provide a lithium secondary battery comprising the LiFe x M 1-x PO4@MoO2 in-situ composite material and a positive electrode thereof.

[0006] A preparation method of a LiFe x M 1-x PO4@MoO2 in-situ composite material, wherein a mixture containing LiFe x M 1-x PO4 and ammonium molybdate is heated to a T1 temperature under a carrier gas flow and is kept for a first-stage heat treatment, then the carrier gas flow is closed, and heating is continued to a T2 temperature and is kept for a second-stage heat treatment, so that the LiFex M 1-x PO4@MoO2 in-situ composite material;

[0007] The M is a transition metal element, and 0 < x ≤ 1.

[0008] The T1 temperature is 80-170 DEG C, and the T2 temperature is 300-700 DEG C.

[0009] In order to solve the preparation difficulty of the material, such as the difficulty in uniform coating of the MoO2 coated material, the non-ideal coating stability, and the difficulty in controlling the phase purity of the coating, the application innovatively finds that, by using LiFe x M 1-x PO4 and ammonium molybdate in the two-stage heat treatment in the gas changing technology, and by further combining the joint control of the preparation heat treatment temperature, the effective control of the MoO2 phase can be realized based on the self-reaction mode, and the coating uniformity and stability are improved, and the electrochemical performance of the prepared material is improved.

[0010] In the application, the LiFe x M 1-x The joint of the LiFe PO4 and the ammonium molybdate and the two-stage heat treatment and the joint control of the gas changing technology and the temperature in the process are the key to improve the phase purity of the material, the coating stability and the uniformity. On this basis, by further controlling the coating amount of Mo and the compounding mode of the precursor raw material, the performance of the prepared material can be further improved.

[0011] In the application, the ammonium molybdate can be ammonium molybdate and polymolybdate thereof.

[0012] As preferred, the molar ratio of the transition metal element (referring to the element of Fe+M) in the LiFe x M 1-x PO4 and the Mo element in the ammonium molybdate is 1:0.001-0.1; preferably 1:0.01-0.05.

[0013] In the application, the LiFe x M 1-x PO4 and the ammonium molybdate are mixed by a dry mixing method or a wet mixing method, preferably a wet mixing method;

[0014] Preferably, the wet mixing method comprises the steps of mixing the LiFe x M 1-x PO4 and the ammonium molybdate in a liquid phase and drying.

[0015] In the wet mixing method, the drying method is spray drying.

[0016] In the present application, the liquid phase mixing process in the wet mixing method is carried out under the assistance of ultrasonic and / or negative pressure, preferably under the assistance of negative pressure.

[0017] In the present application, the heat treatment process can be carried out in a conventional tube furnace, for example, the mixed material is placed in the tube furnace, the carrier gas is introduced from the gas inlet of the tube furnace, flows through the chamber of the tube furnace and is output from the gas outlet, forming a carrier gas flow, under the carrier gas flow, the mixed material is heated to T1 and kept for the first stage treatment, then the carrier gas flow is closed (that is, the gas inlet and the gas outlet are closed to form a closed system), and then heated to T2 under the closed system for the second stage heat treatment. That is, the temperature rising from T1 to T2 and the temperature keeping stage at T2 can be carried out in a closed system, which can be in a vacuum state or a non-continuous flow protective atmosphere. In the present application, based on the combination of the two-stage heat treatment with changing gas and temperature, the phase and morphology can be unexpectedly controlled, and the performance of the prepared material can be improved.

[0018] In the present application, the carrier gas is a protective gas, preferably at least one of nitrogen and inert gas.

[0019] Preferably, the temperature of T1 is 100-150℃, and the temperature keeping time at T1 is preferably 0.5-2.0h.

[0020] Preferably, the temperature of T2 is 500-650℃, and the temperature keeping time at T2 is preferably 1.0-8h.

[0021] In the present application, the LiFe x M 1-x PO4 can be a commercially available product, or can be prepared based on the existing known method.

[0022] For example, the LiFe x M 1-x PO4, the M is at least one element of Mn, Co, Ni and Ti.

[0023] Preferably, the x is 0.2-1, and further preferably, x=1 or 0.2-0.5.

[0024] For example, the LiFe x M 1-x PO4 is obtained by sintering the mixed raw materials containing Li source, Fe source, optional M source and phosphorus source.

[0025] The Fe source can be an iron-containing raw material known in the industry, for example, can be one or more of iron phosphate, ferrous phosphate, ferrous oxalate, iron oxide;

[0026] The M source can be an M-containing raw material known in the industry, for example, can be at least one of an oxide, a carbonate, a phosphate, an acetate, a nitrate, a sulfate of M metal;

[0027] The P source can be a P-containing raw material known in the industry, for example, can be at least one of phosphoric acid, ammonium phosphate, di-ammonium phosphate, hydrogen phosphate;

[0028] In the present application, in the mixed raw material, Fe, M and P are proportioned according to stoichiometric ratio, and the excess coefficient of Li is 1-1.2, preferably stoichiometric ratio;

[0029] Preferably, the mixed raw material further comprises a carbon source, and further preferably, the carbon source is at least one of glucose, sucrose, polyethylene glycol, carbon nanotube;

[0030] Preferably, the raw materials are mixed in liquid phase, and then spray-dried to obtain the mixed raw material;

[0031] Preferably, the solvent for liquid phase mixing is at least one of deionized water, methanol, ethanol;

[0032] Preferably, the sintering temperature is 700-880°C;

[0033] Preferably, the sintering time is 6-12h;

[0034] Preferably, the atmosphere in the sintering stage is a protective atmosphere, for example, at least one of nitrogen, inert gas.

[0035] The present application also provides a LiFe x M 1-x PO4@MoO2 in-situ composite material prepared by the preparation method.

[0036] In the present application, due to the control of the innovative preparation method, the material can be endowed with special physicochemical and structural characteristics, and the material can exhibit excellent electrochemical performance.

[0037] The present application also provides a lithium secondary battery positive electrode material, which comprises a positive electrode active material, and the positive electrode active material is the LiFe x M 1-x PO4@MoO2 in-situ composite material.

[0038] The positive electrode material further comprises a conductive agent and a binder.

[0039] The application further provides a lithium secondary battery positive electrode comprising the LiFe x M 1- x PO4@MoO2 in-situ composite material.

[0040] The application further provides a lithium secondary battery comprising the positive electrode.

[0041] The lithium secondary battery, the positive electrode and the positive electrode material of the application comprise the LiFe x M 1-x PO4@MoO2 in-situ composite material, and other material compositions and contents can be known or adjusted based on known technology.

[0042] Advantages

[0043] The application innovatively performs two-stage heat treatment on LiFe x M 1-x PO4 and ammonium molybdate in the variable atmosphere technology, and further cooperates with the joint control of the preparation and heat treatment temperature, so that the MoO2 phase can be effectively controlled based on the self-reaction mode, the uniformity and stability of the coating are improved, and the electrochemical performance of the prepared material is improved.

[0044] In the application, the mixture obtained based on the preferred liquid phase compounding mode can be further combined with the two-stage variable atmosphere heat treatment to further improve the performance of the prepared material. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A scanning electron microscope image of the lithium ion positive electrode material obtained in Example 1 of the application; DETAILED DESCRIPTION

[0046] The technical solutions of the application will be further described in the specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0047] The above technical objects of the application are achieved by the following technical solutions:

[0048] In the application, the LiFe x M 1-xM in PO4@MoO2 can be a metal element allowed to be doped in the industry. For example, when M is Mn, the specific typical embodiment is, for example:

[0049] S1, adopt the conventional industrial synthesis of lithium ion material LiFe x Mn 1-x PO4:

[0050] The iron source, manganese source, lithium source, phosphorus source, and carbon source are weighed according to the proportion, dispersed in the solvent, and then subjected to sand milling, spray drying, sintering, crushing, and sieving to obtain the lithium ion material LiFe x Mn 1-x PO4;

[0051] In step S1, the iron source is one or more of iron phosphate, ferrous phosphate, ferrous oxalate, and iron oxide, the manganese source is one or more of manganese phosphate, manganese carbonate, and manganese oxide, the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium phosphate, and lithium dihydrogen phosphate, the phosphorus source is at least one of phosphoric acid, ammonium phosphate, dihydrogen ammonium phosphate, and hydrogen dihydrogen ammonium phosphate, the carbon source (for example, selectively added when reduction of Fe(III) is required) is at least one of glucose, sucrose, polyethylene glycol, and carbon nanotubes, and the solvent is at least one of deionized water, methanol, and ethanol. The preparation method of the lithium ion positive electrode material is characterized in that: the sintering temperature in step S1 is 700-880°C, the sintering time is 6-12h, and the sintering atmosphere is nitrogen or argon.

[0052] S2:

[0053] The LiFe x Mn 1-x PO4 prepared in S1 is dispersed in deionized water, and then a certain amount of ammonium molybdate compound is added. After stirring uniformly, spray drying treatment is performed. The ammonium molybdate compound is one of ammonium molybdate and ammonium heptamolybdate tetrahydrate, and is preferably ammonium heptamolybdate tetrahydrate. The molar ratio of the transition metal element in LiFe x M 1-x PO4 to the Mo element in the ammonium molybdate compound = 1:0.001-0.1, and the ammonium molybdate is added.

[0054] S3:

[0055] The spray-dried material in S2 is placed in an atmosphere furnace for two-stage variable atmosphere sintering to obtain the MoO2-coated positive electrode material LiFe x Mn 1-x PO4.

[0056] The process involves two stages of gas-modified sintering. The first stage sintering temperature is 80–170℃, and the sintering time is 0.5–2.0 h. During this period, nitrogen or argon gas is continuously introduced (the flow rate is not particularly required, for example, it can be 100–1000 sccm). After the first stage sintering is completed, the gas supply is stopped (the reaction chamber of the sealed atmosphere furnace is closed), and the temperature is raised to the second stage sintering temperature and held at that temperature. The second stage sintering temperature is 300–700℃, and the sintering time is 1.0–8 h.

[0057] Example 1

[0058] S1, Preparation of active matrix materials:

[0059] According to the stoichiometric ratio of LiFePO4, the corresponding masses of iron phosphate, lithium carbonate and glucose (where the molar ratio of transition metal element (iron in this case) to glucose is 12:1) are weighed and dispersed in deionized water. The solid content of the slurry is controlled to be 35%. The slurry is sand-milled to a particle size of 0.42 μm and then spray-dried. The spray-dried material is placed in an atmosphere furnace and sintered at 780℃ for 8 hours under nitrogen protection. After pulverization and sieving, LiFePO4 cathode material is obtained.

[0060] S2, Coating treatment:

[0061] Ammonium heptamolybdate tetrahydrate (transition metal element (iron in this case) / Mo molar = 1:0.045) was weighed at 5% of the mass of LiFePO4 cathode material, dispersed in deionized water, and the solid content was controlled at 40%. After stirring for 0.5 h (liquid phase composite), it was spray dried to obtain the precursor.

[0062] S3, two-stage variable gas sintering:

[0063] The precursor obtained in S2 was placed in an atmosphere furnace and nitrogen gas was introduced. The temperature was raised to 120℃ (marked as T1) under the flowing nitrogen gas and sintered at that temperature for 1 hour (marked as t1). After that, the nitrogen gas was stopped, the reaction chamber of the atmosphere furnace was sealed, and the temperature was raised to 650℃ (marked as T2) under the sealed system and sintered at that temperature for 5 hours (marked as t2) to obtain a LiFePO4 cathode material with MoO2 uniformly coated on the surface.

[0064] Example 2

[0065] Compared to Example 1, the only difference is that the active material is changed similarly, and the experimental groups are as follows:

[0066] A: The active material obtained from S1 is LiFe 0.4 Mn 0.6 PO4:

[0067] The difference in S1 is: according to LiFe 0.4 Mn0.6 The stoichiometric ratio of PO4 was determined by weighing out the corresponding masses of ferrous oxalate, manganese carbonate, lithium phosphate, phosphoric acid, and glucose, and dispersing them in deionized water. The solid content of the slurry was controlled at 38%. The slurry was then milled to a particle size of 0.28 μm, followed by spray drying. The spray-dried material was then placed in an atmosphere furnace under nitrogen protection and sintered at 760℃ for 9 hours. Afterward, it was pulverized and sieved to obtain LiFe. 0.4 Mn 0.6 PO4 cathode material. Other operations and parameters are the same as in Example 1.

[0068] B: The active material obtained from S1 is LiFe 0.3 Mn 0.7 PO4:

[0069] According to LiFe 0.3 Mn 0.7 The stoichiometric ratio of PO4 was determined by weighing out the appropriate masses of ferrous oxalate, manganese carbonate, lithium phosphate, phosphoric acid, and glucose, dispersing them in deionized water. The solid content of the slurry was controlled at 38%. The slurry was then milled to a particle size of 0.36 μm, followed by spray drying. The spray-dried material was then placed in an atmosphere furnace under nitrogen protection and sintered at 800℃ for 7 hours. Afterward, it was pulverized and sieved to obtain LiFe. 0.3 Mn 0.7 PO4 cathode material;

[0070] Other operations and parameters are the same as in Example 1.

[0071] Example 3

[0072] Compared to Example 1, the only difference is that the molar ratio of Fe / Mo in S2 is changed, and the experimental groups are as follows:

[0073] A: The molar ratio of Fe to Mo is 1:0.02.

[0074] B: The molar ratio of Fe / Mo is 1:0.01.

[0075] All other operations and parameters are the same as in Example 1.

[0076] Example 4

[0077] Compared with Example 1, the only difference is the process of the liquid phase recombination stage in S2. The experimental groups are as follows:

[0078] Group A: The liquid-phase recombination stage of S2 was carried out with the assistance of ultrasound (power of 200W, time of 0.5h), and other operations and parameters were the same as in Example 1;

[0079] Group B: The liquid phase recombination stage of S2 was carried out under negative pressure (0.5 atm, time 0.5 h), and other operations and parameters were the same as in Example 1.

[0080] Example 5

[0081] Compared to Example 1, the only difference is that the two gas transformation conditions were changed, and the experimental groups were as follows:

[0082] Group A: T1 is 100℃, T2 is 600℃;

[0083] Group B: T1 is 150℃, T2 is 550℃;

[0084] Other operations and parameters are the same as in Example 1.

[0085] Comparative Example 1

[0086] Compared with Example 1, the only difference is that the subsequent S2 and S3 steps are not performed, and the material obtained in S1 is directly used as the active material.

[0087] Comparative Example 2

[0088] Compared with Example 1, the only difference is that the material obtained in S1 is ball-milled and mixed with an equimolar amount of MoO2 to obtain a composite active material.

[0089] Comparative Example 3

[0090] Compared to Example 1, the only difference is that an equimolar amount of sodium molybdate is used instead of the ammonium molybdate. All other operations and parameters are the same as in Example 1.

[0091] Comparative Example 4

[0092] Compared with Example 1, the only difference is that in S3, the pre-treatment in segment T1 is not performed, but the temperature is maintained for time t2 under the condition of T2.

[0093] Comparative Example 5

[0094] Compared with Example 1, the only difference is that in S3, no airflow is introduced into section T1, and the two-stage treatment of T1 and T2 is carried out in a closed system.

[0095] Comparative Example 6

[0096] Compared with Example 1, the only difference is that in S3, airflow is introduced into both T1 and T2 sections.

[0097] Comparative Example 7

[0098] Compared with Example 1, the only difference is that in S3, the temperature of T1 is 280°C and the temperature of T2 is 750°C. Other operations and parameters are the same as in Example 1.

[0099] Powder compaction test: 1g of the positive electrode material products provided in Examples 1-5 and Comparative Examples 1-7 were weighed respectively, and the compaction density was tested using a 3T pressure sensor at a pressure of 16Mpa, as shown in Table 1.

[0100] Table 1 Comparison of compaction density of active materials in Examples 1-5 and Comparative Examples 1-7

[0101]

[0102]

[0103] Electrical performance testing

[0104] (1) Preparation of the positive electrode sheet:

[0105] The positive electrode materials prepared by the above method in Examples 1-5 and Comparative Examples 1-7 were used as positive electrode active materials. A slurry of positive electrode active material: SP (superconducting carbon black):PVDF (polyvinylidene fluoride) at a mass ratio of 90:5:5 was homogenized and coated onto a 20 μm thick aluminum foil to produce a positive electrode sheet with an areal density of 8 mg / cm³. 2 Then, through drying, rolling, die cutting, and punching, it is formed into positive electrode sheets.

[0106] (2) Battery fabrication: A button cell casing of R2032 was used for coin cell assembly. Lithium foil was used as the negative electrode, and a PE separator was employed. 80 μmL of electrolyte was added. The test temperature was 25℃. The LFP active material was tested at a voltage range of 2.0V to 3.9V, charged to 3.9V using a constant current / constant voltage charging method, and discharged to 2.0V using a constant current discharging method. The LMFP active material (referring to Example 2) was tested at a voltage range of 2.0V to 4.5V, charged to 4.5V using a constant current / constant voltage charging method, and discharged to 2.0V using a constant current discharging method. The charge / discharge currents for the first four cycles were 0.1C, 0.2C, 0.5C, and 1C, respectively. Subsequent cycles were performed using a 1C charge / discharge current for 100 cycles. The test results are shown in Table 2.

[0107] Table 2 Comparison of electrochemical performance of active materials in Examples 1-5 and Comparative Examples 1-7

[0108]

[0109]

[0110] The test results above show that while conventional carbon coating processes can ensure the electrochemical performance of materials, they reduce the compaction density, resulting in a lower energy density. Because phosphate active materials have poor conductivity, not coating them with conductive materials leads to poor electrochemical performance, rendering them unusable. Direct mixing and coating with molybdenum dioxide is difficult to achieve uniform coating, resulting in poor electrochemical performance. The technical solution of this invention utilizes the high-temperature decomposition and self-reducing properties of molybdate compounds to in-situ coat the surface of the active material with a layer of highly conductive molybdenum dioxide, ensuring excellent electrochemical performance while simultaneously improving the compaction density of the active material.

[0111] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A LiFe x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, Will contain LiFe x M 1-x The mixture of PO4 and ammonium molybdate was heated to temperature T1 under a carrier gas flow and held for the first stage of heat treatment. Then, the carrier gas flow was turned off, and the temperature was further increased to T2 and held for the second stage of heat treatment, thus obtaining the LiFe. x M 1-x PO4@MoO2 in-situ composite material; M is a transition metal element, and 0 <x≤1; The carrier gas is a protective gas; The heating process from T1 to T2 and the subsequent holding at T2 are carried out in a closed system; the closed system is either a vacuum or a non-continuously flowing protective atmosphere. The temperature of T1 is 100~150℃; the holding time at temperature T1 is 0.5~2.0h; The temperature of T2 is 500~650℃; the holding time at T2 temperature is 1.0~8h.

2. The LiFe as described in claim 1 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The LiFe x M 1-x The molar ratio of transition metal elements in PO4 to Mo in ammonium molybdate is 1:0.001~0.

1.

3. The LiFe as described in claim 2 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The LiFe x M 1-x The molar ratio of transition metal elements in PO4 to Mo in ammonium molybdate is 1:0.01~0.

05.

4. The LiFe as described in claim 1 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The LiFe x M 1-x PO4 and ammonium molybdate can be mixed by dry or wet methods.

5. The LiFe as described in claim 4 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The wet mixing method includes mixing LiFe x M 1-x The steps of liquid-phase mixing and drying of PO4 and ammonium molybdate; In the aforementioned wet mixing method, the drying method is spray drying.

6. The LiFe as described in claim 5 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, In the aforementioned wet mixing method, the liquid phase mixing process is carried out under ultrasonic and negative pressure assistance.

7. The LiFe as described in any one of claims 1 to 6 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, M is at least one element selected from Mn, Co, Ni, and Ti.

8. The LiFe as described in claim 7 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The value of x is 0.2 to 1.

9. The LiFe as described in claim 8 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The x=1, or is 0.2~0.

5.

10. The LiFe according to any one of claims 1 to 6 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The LiFe x M 1-x PO4 is obtained by sintering a mixture of raw materials including a Li source, an Fe source, and selectively included M and phosphorus sources.

11. The LiFe as described in claim 10 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The Fe source is one or more of ferric phosphate, ferrous phosphate, ferrous oxalate, and ferric oxide; The M source is at least one of the following: oxide, carbonate, phosphate, acetate, nitrate, and sulfate of the M metal; The phosphorus source is at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; In the mixed raw materials, Fe, M and P are proportioned according to stoichiometric ratio, and the excess coefficient of Li is 1~1.

2.

12. The LiFe as described in claim 11 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The mixed raw materials also contain a carbon source.

13. The LiFe as described in claim 12 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The carbon source is at least one of glucose, sucrose, polyethylene glycol, and carbon nanotubes.

14. The LiFe as described in claim 10 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The liquid phases of the raw materials are mixed and then spray-dried to obtain the mixed raw material. The solvent for the liquid phase mixture is at least one of deionized water, methanol, and ethanol.

15. The LiFe as described in claim 10 x M 1-x The method for preparing PO4@MoO2 in-situ composite material is characterized by, The sintering temperature is 700–880℃; The sintering time is 6–12 hours; The atmosphere during the sintering stage is a protective atmosphere.

16. A LiFe alloy prepared by the method according to any one of claims 1 to 15 x M 1-x PO4@MoO2 in-situ composite material.

17. A positive electrode for a lithium secondary battery, characterized in that, It comprises LiFe obtained by the preparation method according to any one of claims 1 to 15. x M 1-x PO4@MoO2 in-situ composite material.

18. A lithium secondary battery, characterized in that, It comprises the positive electrode as described in claim 17.

Images