Lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, preparation method thereof, positive plate and lithium ion battery

Abstract

The invention provides a lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, a preparation method thereof, a positive plate and a lithium ion battery. The chemical structural formula of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is LiMn1-xFexPO4 / Ti3C2, wherein x is more than or equal to 0.1 and less than or equal to 0.9. In the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, a part of titanium ions occupy an M site in lithium manganese iron phosphate to form a metal-hole pair, so that the Jahn-Teller effect can be reduced, the dissolution of manganese ions caused by lattice distortion in the circulation process can be reduced, and the service life of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is prolonged. Further, the structural stability and the cycle performance of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material can be improved. Besides, reversible high capacity is realized by constructing a heterostructure and titanium carbide absorbing and utilizing lattice oxygen, and a stable positive electrode / electrolyte interface is obtained, so that a positive electrode system is favorably stabilized, and stable output of electrochemical performance is favorably promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery. BACKGROUND

[0002] Lithium manganese iron phosphate has an olivine structure similar to lithium iron phosphate, and the electrode potential of lithium manganese iron phosphate relative to Li + / Li is 4.1V, which is much higher than 3.4V of lithium iron phosphate. It has attracted wide attention due to its high theoretical capacity, moderate working voltage platform, widely available raw materials, and green environmental protection. However, the poor conductivity and slow lithium ion diffusion rate of lithium manganese iron phosphate make it difficult to achieve its full capacity. In addition, the Jahn-Teller effect of lithium manganese iron phosphate greatly affects its cycle performance during the cycle process, which limits the further promotion and application of lithium manganese iron phosphate in positive electrode materials.

[0003] A Chinese patent application with application number 202110289750.5 discloses a synthesis method of a novel lithium iron manganese phosphate positive electrode material, which comprises the following steps: S1, stirring manganese dioxide, phosphoric acid and water in a container, adding aniline, and continuing to stir to obtain polyaniline; S2, weighing iron source, lithium source, carbon source and organic auxiliary agent, and adding them to the polyaniline for grinding and stirring; S3, drying and calcining under air atmosphere to obtain a precursor; S4, adding carbon source and grinding medium to the precursor again, and grinding to obtain a grinding slurry; S5, vacuum drying the grinding slurry to obtain a reaction powder; S6, sintering the reaction powder under a protective atmosphere, cooling to room temperature, crushing and sieving to obtain a lithium ion battery positive electrode material of lithium iron manganese phosphate coated with polyaniline / carbon.

[0004] A Chinese patent application with application number 201510329476.4 discloses a preparation method of a lithium manganese iron phosphate positive electrode material. First, lithium hydroxide solution and phosphoric acid solution are uniformly mixed to form solution A after adding carbon source and surfactant. Then, divalent iron salt solution and divalent manganese salt solution are uniformly mixed to form solution B. Solution B is added dropwise into solution A to form suspension C. Suspension C is transferred to a magnetic stirring hydrothermal kettle to obtain a precursor slurry of in-situ carbon-coated lithium manganese iron phosphate. The precursor slurry is quenched to room temperature with cooling water and filtered. The filter cake after filtration is washed with an aqueous solution for 3-5 times. The washed filter cake is placed in a vacuum drying oven to finally obtain the in-situ carbon-coated lithium manganese iron phosphate positive electrode material. The positive electrode material prepared by this method has the characteristics of uniform thickness of carbon coating layer, uniform particle size distribution and nanoscale, good cycle stability and excellent rate performance.

[0005] The Chinese patent application No. 202410312566.1 discloses a lithium manganese iron phosphate composite positive electrode material, and a preparation method thereof. The preparation method comprises the following steps: a precursor formed by using sodium tripolyphosphate as a phosphorus source, in combination with a manganese source, an iron source and a doping element, is mixed with a lithium source, biomass carbon quantum dots and chitosan, and a lithium manganese iron phosphate composite positive electrode material is synthesized by high-temperature pyrolysis.

[0006] Although the above-mentioned patent application partially improves the conductivity and specific capacity of lithium manganese iron phosphate, it is still difficult to effectively solve the problems of poor lithium ion conductivity and manganese dissolution caused by Jahn-Teller effect of lithium manganese iron phosphate during the cycle process. SUMMARY

[0007] The main purpose of the present application is to provide a lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery, so as to solve the problems of poor lithium ion conductivity and high manganese ion dissolution of lithium manganese iron phosphate positive electrode material in the prior art during the cycle process.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is provided, and the chemical structural formula of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is LiMn 1-x Fe x PO4 / Ti3C2, 0.1≤x≤0.9.

[0009] Further, the mass ratio of the above-mentioned Ti3C2 to LiMn 1-x Fe x PO4 is 1:(10-1000), preferably 1:(100-1000).

[0010] Further, the above-mentioned lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is obtained by in-situ growth of LiMn 1-x Fe x PO4 on the surface of Ti3C2; and / or, the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is a sheet-shaped stacking structure; the average planar face diameter of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is 400-700 nm; preferably, the Ti3C2 in the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is a sheet-shaped structure with 1-10 layers; and / or, the average particle size of LiMn 1-x Fe x PO4 in the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is 10-100 nm; and / or, the powder resistivity of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material is 10-600 Ω / m.

[0011] According to another aspect of the present application, there is provided a preparation method of the aforementioned lithium iron manganese phosphate / titanium carbide heterojunction positive electrode material, which comprises: step S1, mixing raw materials comprising a lithium source, Ti3C2, a surfactant and water to obtain a first mixed solution; step S2, mixing raw materials comprising a manganese source, a ferrous source and water to obtain a second mixed solution; step S3, mixing the first mixed solution and the second mixed solution, then adjusting pH with a phosphoric acid aqueous solution, and then performing a hydrothermal reaction to obtain a precursor product; and step S4, performing a sintering treatment on the precursor product under a protective gas to obtain the lithium iron manganese phosphate / titanium carbide heterojunction positive electrode material.

[0012] Further, in the aforementioned step S3, the target pH value of the pH adjustment is 3-6; and / or, the concentration of the phosphoric acid aqueous solution is 1.0-2.0 mol / L; and / or, the temperature of the hydrothermal reaction is 160-200℃; and / or, the time of the hydrothermal reaction is 16-24 h.

[0013] Further, in the aforementioned step S4, the temperature of the sintering treatment is 700-800℃; and / or, the time of the sintering treatment is 4-10 h.

[0014] Further, in the aforementioned step S1, the preparation method of Ti3C2 comprises: sequentially mixing Ti3AlC2 and a HF solution, performing a heating reaction and performing ultrasonic treatment to obtain Ti3C2, wherein the temperature of the mixing is 0-10℃; and / or, the time of the mixing is 30-120 min; and / or, the temperature of the heating reaction is 30-60℃; and / or, the time of the heating reaction is 24-48 h; and / or, the temperature of the ultrasonic treatment is 0-10℃; and / or, the time of the ultrasonic treatment is 0.1-3 h; and / or, the frequency of the ultrasonic treatment is 10-1000 kHz; preferably, the mixing and the heating reaction are both performed under stirring, and the stirring speed of the mixing and the heating reaction is independently 500-10000 r / min.

[0015] Further, the mass ratio of the aforementioned Ti3C2 to the surfactant is 0.167:(2-3); preferably, the lithium source is selected from any one or more of lithium hydroxide, lithium carbonate, lithium oxalate and lithium dihydrogen phosphate; and / or, the surfactant is selected from any one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, polyvinylpyrrolidone, polyethylene glycol and mercapto polyethylene glycol; and / or, the manganese source is selected from any one or more of manganese dioxide, manganese chloride, manganous sulfate, manganous oxalate, manganous acetate and manganous nitrate; and / or, the ferrous source is selected from any one or more of ferrous chloride, ferrous sulfate, ferrous oxalate, ferrous acetate and ferrous nitrate.

[0016] According to another aspect of the present application, a positive electrode sheet is provided, comprising a positive electrode active layer and a current collector, the positive electrode active layer containing the aforementioned lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material.

[0017] According to another aspect of the present application, a lithium ion battery is provided, comprising a positive electrode sheet, an electrolyte and a negative electrode sheet, the positive electrode sheet being the aforementioned positive electrode sheet.

[0018] According to the technical solution of the present application, the titanium carbide has a hydrophilic surface, good electronic conductivity and electrochemical stability, and the presence of the titanium carbide in the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material of the present application helps to form an efficient ion and electron transport channel, thereby helping to improve the electrical conductivity of the lithium manganese iron phosphate and the transmission rate of lithium ions. At the same time, in the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, part of the titanium ions occupy the M site in the lithium manganese iron phosphate, forming a metal-hole pair, which helps to reduce the Jahn-Teller effect, thereby helping to reduce the dissolution of manganese ions caused by lattice distortion during the cycle process, and further helping to improve the structural stability and cycle performance of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material. In addition, by constructing a heterostructure, the titanium carbide absorbs and utilizes lattice oxygen to achieve reversible high capacity and obtain a stable positive electrode / electrolyte interface, which helps to stabilize the positive electrode system, thereby helping to promote the stable output of the electrochemical performance. Therefore, the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material of the present application has high electrical conductivity, lithium ion conductivity, specific capacity and cycle life, and low manganese dissolution. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, and the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0020] Figure 1 The SEM image of the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0021] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] As analyzed in the background art of the present application, the existing lithium manganese iron phosphate positive electrode material has the problems of poor lithium ion conductivity and high manganese ion dissolution during the cycle process. In order to solve the above problems, the present application provides a lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery.

[0023] In one typical embodiment of this application, a lithium manganese iron phosphate / titanium carbide heterojunction cathode material is provided, the chemical structural formula of which is LiMn. 1-x Fe x PO4 / Ti3C2, 0.1≤x≤0.9.

[0024] Titanium carbide possesses a hydrophilic surface, good electronic conductivity, and electrochemical stability. In the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application, the presence of titanium carbide facilitates the formation of efficient ion and electron transport channels, thereby improving the conductivity and lithium-ion transport rate of lithium manganese iron phosphate. Simultaneously, in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material, some titanium ions occupy the M sites in lithium manganese iron phosphate, forming metal-hole pairs. This helps reduce the Jahn-Teller effect, thereby reducing manganese ion dissolution due to lattice distortion during cycling, and further improving the structural stability and cycle performance of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material. Furthermore, by constructing a heterostructure, titanium carbide absorbs and utilizes lattice oxygen to achieve reversible high capacity and obtains a stable cathode / electrolyte interface, contributing to the stability of the cathode system and thus promoting stable electrochemical performance output. Therefore, the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application exhibits high conductivity, lithium-ion conductivity, specific capacity, and cycle life, with low manganese dissolution.

[0025] In one embodiment of this application, the above-mentioned LiMn 1-x Fe x PO4 / Ti3C2, 0.4≤x≤0.5.

[0026] Controlling the x value within the above range helps optimize the ratio of Mn and Fe elements, thereby further improving the electronic conductivity of lithium manganese iron phosphate, enhancing the synergistic effect between lithium manganese iron phosphate and titanium carbide, and thus helping to improve the lithium-ion transport efficiency and electron transport efficiency of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material.

[0027] In one embodiment of this application, the above-mentioned Ti3C2 and LiMn 1-x Fe x The mass ratio of PO4 is 1:(10 to 1000), preferably 1:(100 to 1000), and can specifically be 1:100, 1:200, 1:300, 1:400, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, and any range between two ratios.

[0028] Control of Ti3C2 and LiFe 1-x Mn xWhen the mass ratio of PO4 is within the above range, it helps to form a highly efficient conductive network in lithium manganese iron phosphate materials, reducing the resistance to electron transport, thereby helping to improve the discharge efficiency and charging efficiency of lithium-ion batteries, and enabling lithium manganese iron phosphate / titanium carbide heterojunction cathode materials to maintain a high specific capacity.

[0029] In one embodiment of this application, the above-mentioned lithium manganese iron phosphate / titanium carbide heterojunction cathode material is formed by in-situ growth of LiMn on the surface of Ti3C2. 1-x Fe x PO4 is obtained; and / or, the lithium manganese iron phosphate / titanium carbide heterojunction cathode material has a sheet-like stacked structure; the average planar diameter of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material is 400-700 nm; preferably, the Ti3C2 in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material has a sheet-like structure of 1-10 layers; and / or, the LiMn in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material is... 1-x Fe x The average particle size of PO4 is 10–100 nm; and / or the powder resistivity of lithium manganese iron phosphate / titanium carbide heterojunction cathode material is 10–600 Ω / m.

[0030] LiMn was formed on the Ti3C2 surface through in-situ growth. 1-x Fe x PO4 yields a lithium manganese iron phosphate (LFP) / titanium carbide (TiCarbide) heterojunction cathode material. The LFP is more uniformly distributed on the TiCarbide surface, and the bonding between LFP and TiCarbide is tighter, which helps to further improve lithium-ion and electron transport efficiency. The sheet-like stacked structure facilitates lithium-ion insertion and extraction, thereby improving the rate performance and cycle stability of the LFP / TiCarbide heterojunction cathode material. Controlling the average thickness of the LFP / TiCarbide heterojunction cathode material within the aforementioned range helps to balance its electrochemical activity and lithium-ion and electron transport capabilities. Controlling the average planar diameter of the LFP / TiCarbide heterojunction cathode material within the aforementioned range helps to increase the surface area of ​​the material, thereby increasing the contact area between the electrode active material and the electrolyte, which in turn helps to improve the battery's capacity and power density. Controlling the number of titanium carbide layers and the average planar diameter within the aforementioned range helps to increase the specific surface area of ​​titanium carbide, providing more growth sites for lithium manganese iron phosphate (LMP), thereby contributing to further improvements in the conductivity, lithium-ion conductivity, specific capacity, and cycle life of the LMP / TIC heterojunction cathode material. Controlling the average particle size of LMP in the LMP / TIC heterojunction cathode material within the aforementioned range helps to further shorten the lithium-ion transport path, thus contributing to further improvements in lithium-ion transport efficiency. LMP / TIC heterojunction cathode materials with the aforementioned powder resistivity exhibit higher specific capacity and rate performance.

[0031] In another typical embodiment of this application, a method for preparing the aforementioned lithium manganese iron phosphate / titanium carbide heterojunction cathode material is provided. The preparation method includes: step S1, mixing raw materials including a lithium source, Ti3C2, a surfactant, and water to obtain a first mixture; step S2, mixing raw materials including a manganese source, a divalent iron source, and water to obtain a second mixture; step S3, mixing the first mixture and the second mixture, adjusting the pH using a phosphoric acid aqueous solution, and then performing a hydrothermal reaction to obtain a precursor product; step S4, sintering the precursor product under a protective gas to obtain the lithium manganese iron phosphate / titanium carbide heterojunction cathode material.

[0032] In step S1, lithium source, Ti3C2, surfactant, and water are mixed to obtain a first mixture. The presence of surfactant helps to control the particle size and morphology of lithium manganese iron phosphate. In step S2, manganese source, ferrous iron source, and water are mixed to obtain a second mixture. In step S3, mixing the first and second mixtures helps to improve the uniformity of dispersion among the components. A phosphoric acid aqueous solution is used for pH adjustment. Phosphoric acid serves as both a phosphorus source and a solution pH adjuster. pH adjustment helps to reduce side reactions, thereby improving the purity of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material. Through hydrothermal reaction, the lithium manganese iron phosphate precursor grows in situ on the titanium carbide surface, resulting in a more uniform distribution of lithium manganese iron phosphate on the titanium carbide surface and a tighter bond between lithium manganese iron phosphate and titanium carbide, which helps to further improve lithium-ion transport efficiency and electron transport efficiency. Sintering the precursor products under a protective gas atmosphere helps remove impurity elements, improves the crystallinity of lithium manganese iron phosphate, and forms a lithium manganese iron phosphate / titanium carbide heterojunction cathode material with high conductivity, lithium-ion conductivity, specific capacity and cycle life, and low manganese dissolution.

[0033] In one embodiment of this application, the product of the hydrothermal reaction in step S3 is sequentially washed and dried to obtain the precursor product. The washing agent is selected from any one or more of water, ethanol, and acetone; the drying temperature is 60–100°C, and the drying time is 5–48 hours.

[0034] Including but not limited to, the protective gas mentioned above is selected from any one or more of nitrogen, argon and helium.

[0035] In one embodiment of this application, in step S3 above, the target pH value for pH adjustment is 3 to 6; and / or, the concentration of the phosphoric acid aqueous solution is 1.0 to 2.0 mol / L; and / or, the temperature of the hydrothermal reaction is 160 to 200°C; and / or, the time of the hydrothermal reaction is 16 to 24 h.

[0036] Controlling the target pH value within the aforementioned range helps control the growth rate and morphology of the lithium manganese iron phosphate precursor, forming a more uniform lamellar stacking structure. This structure is beneficial for increasing the specific surface area of ​​the material and optimizing the lithium-ion insertion and extraction channels. Controlling the concentration of the phosphoric acid aqueous solution within the aforementioned range helps promote the uniform nucleation and growth of the lithium manganese iron phosphate precursor, thereby contributing to improving the discharge capacity and cycle performance of the lithium-ion battery. Controlling the temperature and time of the hydrothermal reaction within the aforementioned range helps form a tight heterojunction interface, while controlling the material at a suitable particle size, thereby contributing to improving the discharge capacity and cycle stability of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material.

[0037] In order to improve the crystallinity of lithium manganese iron phosphate and the tightness of the bond between lithium manganese iron phosphate and titanium carbide, in one embodiment of this application, it is preferred that the sintering temperature in step S4 is 700-800°C; and / or the sintering time is 4-10 hours.

[0038] To further improve the specific surface area and electrical conductivity of Ti3C2, in one embodiment of this application, preferably, the preparation method of Ti3C2 in step S1 includes: sequentially mixing Ti3AlC2 and HF solution, heating reaction, and ultrasonic treatment to obtain Ti3C2, wherein the mixing temperature is 0-10℃; and / or, the mixing time is 30-120 min; and / or, the heating reaction temperature is 30-60℃; and / or, the heating reaction time is 24-48 h; and / or, the ultrasonic treatment temperature is 0-10℃; and / or, the ultrasonic treatment time is 0.1-3 h; and / or, the ultrasonic treatment frequency is 10-1000 kHz; preferably, both the mixing and heating reactions are carried out under stirring, and the stirring speeds of the mixing and heating reactions are each independently 500-10000 r / min.

[0039] The above HF solution is obtained by reacting LiF with hydrochloric acid aqueous solution.

[0040] In one embodiment of this application, the suspension after ultrasonic treatment is sequentially washed and freeze-dried to obtain Ti3C2. The washing agent is selected from any one or more of water, ethanol, and acetone.

[0041] In one embodiment of this application, the mass ratio of Ti3C2 to surfactant is 0.167:(2-3); preferably, the lithium source is selected from any one or more of lithium hydroxide, lithium carbonate, lithium oxalate, and lithium dihydrogen phosphate; and / or, the surfactant is selected from any one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinylpyrrolidone, polyethylene glycol, and mercapto polyethylene glycol; and / or, the manganese source is selected from any one or more of manganese dioxide, manganese chloride, manganese sulfate, manganese oxalate, manganese acetate, and manganese nitrate; and / or, the ferrous source is selected from any one or more of ferrous chloride, ferrous sulfate, ferrous oxalate, ferrous acetate, and ferrous nitrate.

[0042] The presence of surfactants helps improve the dispersibility of Ti3C2, thereby promoting the uniform growth of lithium manganese iron phosphate on the Ti3C2 surface. Controlling the mass ratio of Ti3C2 to surfactant within the aforementioned range helps reduce Ti3C2 agglomeration, controls the morphology and size of the lithium manganese iron phosphate precursor, and forms a dense heterostructure, thus improving the electron and ion transport capabilities of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material. Controlling the types of manganese source, lithium source, surfactant, and divalent iron source within the aforementioned range helps improve the synergistic effect between the components, thereby contributing to the formation of a structurally stable lithium manganese iron phosphate / titanium carbide heterojunction cathode material with high electrochemical activity.

[0043] In one embodiment of this application, the surfactant is polyethylene glycol, and the weight-average molecular weight of polyethylene glycol is 1000-20000 g / mol.

[0044] Polyethylene glycol (PEG), as a nonionic surfactant, exhibits excellent water solubility and chemical stability, significantly improving the dispersibility and flowability of solutions. Controlling the weight-average molecular weight of PEG within the aforementioned range helps reduce the surface tension between Ti3C2 particles, preventing Ti3C2 aggregation. This facilitates the uniform distribution of Ti3C2 in the solution, promoting the formation of a dense and uniform heterojunction structure. Furthermore, it aids in the formation of lithium manganese iron phosphate precursors with suitable particle sizes, thereby further enhancing lithium-ion transport efficiency.

[0045] In another typical embodiment of this application, a positive electrode sheet is provided, including a positive electrode active layer and a current collector, wherein the positive electrode active layer contains the aforementioned lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material.

[0046] Because the above-mentioned cathode contains the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application, the cathode has high rate performance and cycle stability.

[0047] In another typical embodiment of this application, a lithium-ion battery is provided, including a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode is the aforementioned positive electrode.

[0048] Because the positive electrode of the above-mentioned lithium-ion battery contains the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material of this application, the lithium-ion battery has high specific capacity, cycle life and safety.

[0049] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0050] Example 1

[0051] Weigh 1g of LiF powder and add it in small amounts several times to 20mL of 9M hydrochloric acid aqueous solution under ice bath and stirring conditions to obtain HF solution. Weigh 1g of Ti3AlC2 powder and add it in small amounts several times to the above HF solution under ice bath and stirring conditions. The mixing temperature is 0℃, the mixing time is 30min, and the stirring speed is 1000r / min. After the mixing treatment, the temperature is increased to 35℃ for heating reaction, the heating time is 24h, and the stirring speed is 1000r / min to obtain product Ti3C2.

[0052] The Ti3C2 product was washed with deionized water, and the product and washing liquid were separated by centrifugation at 4000 rpm. Centrifugation was repeated for 5 min in several cycles until the pH reached 5, at which point the washing process was stopped. The precipitate obtained by centrifugation was resuspended in deionized water. The Ti3C2 suspension was then sonicated in an ice bath to obtain a suspension with 1–10 Ti3C2 layers. The sonication temperature was 10 °C, the sonication time was 2 h, and the sonication frequency was 60 kHz. Finally, lyophilization was used to obtain sheet-like samples with 1–10 Ti3C2 layers. The average planar diameter of the Ti3C2 was 1 μm. Both the number of layers and the planar diameter were measured using SEM.

[0053] First, prepare a 2 mol / L lithium hydroxide aqueous solution, add 0.167 g of the above-mentioned Ti3C2 flake sample and 2.5 g of surfactant polyethylene glycol (weight average molecular weight of 2000 g / mol) to form the first mixture; then prepare a 0.4 mol / L ferrous chloride aqueous solution and a 0.6 mol / L manganese chloride aqueous solution, and mix them evenly to form the second mixture.

[0054] The first and second mixtures were thoroughly stirred and sonicated for 30 minutes to disperse them evenly. Then, the second mixture was added dropwise to the first mixture to form the third mixture. Phosphoric acid aqueous solution was added to control the pH of the third mixture to 4. The concentration of the phosphoric acid aqueous solution was 1.0 mol / L. The mixture was stirred and sonicated until completely dissolved.

[0055] The third mixture was transferred to a magnetically stirred hydrothermal reactor and hydrothermally reacted at 170°C for 20 hours. After the reaction was completed, the precursor slurry was obtained.

[0056] The precursor slurry was filtered, washed with water, dried at 60°C for 12 hours, sintered at 750°C for 6 hours under nitrogen protection, and then naturally cooled to room temperature to obtain LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:1000. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 550 nm, and that of LiMn... 0.6 Fe 0.4 The average particle size of PO4 is 71 nm. The planar diameter and particle size were both obtained by SEM measurement.

[0057] Example 2

[0058] The difference from Example 1 is that 1g of LiF powder was weighed and added in small amounts several times to 20mL of 9M hydrochloric acid aqueous solution under ice bath and stirring conditions to obtain an HF solution. 1g of Ti3AlC2 powder was weighed and added in small amounts several times to the above HF solution under ice bath and stirring conditions for mixing. The mixing temperature was 0℃, the mixing time was 30min, and the stirring speed was 1000r / min. After the mixing treatment, the temperature was increased to 35℃ for a heating reaction, the heating time was 24h, and the stirring speed was 1000r / min to obtain the product Ti3C2.

[0059] The Ti3C2 product was washed with deionized water, and the product and washing liquid were separated by centrifugation at 4000 rpm. Centrifugation was repeated for 5 min several times until the pH reached 6, at which point the washing process was stopped. The precipitate obtained by centrifugation was resuspended in deionized water. The Ti3C2 suspension was then sonicated in an ice bath at 10℃ for 2 h at a frequency of 60 kHz to obtain Ti3C2 suspensions with 1–10 layers. Finally, freeze-drying was used to obtain Ti3C2 sheet-like samples with 1–10 layers, the average planar diameter of which was 1 μm.

[0060] First, prepare a 2 mol / L lithium hydroxide aqueous solution, add 0.167 g of the above-mentioned Ti3C2 flake sample and 2.5 g of surfactant polyethylene glycol (weight average molecular weight of 2000 g / mol) to form the first mixture; then prepare a 0.5 mol / L ferrous chloride aqueous solution and a 0.5 mol / L manganese chloride aqueous solution, and mix them evenly to form the second mixture.

[0061] The first and second mixtures were thoroughly stirred and sonicated for 30 minutes to disperse them evenly. Then, the second mixture was added dropwise to the first mixture to form the third mixture. Phosphoric acid aqueous solution was added to control the pH of the third mixture to 4. The concentration of the phosphoric acid aqueous solution was 1.0 mol / L. The mixture was stirred and sonicated until completely dissolved.

[0062] The third mixture was transferred to a magnetically stirred hydrothermal reactor and hydrothermally reacted at 170°C for 20 hours. After the reaction was completed, the precursor slurry was obtained.

[0063] The precursor slurry was filtered, washed with water, dried at 60°C for 12 hours, sintered at 750°C for 6 hours under nitrogen protection, and then naturally cooled to room temperature to obtain LiMn. 0.5 Fe 0.5 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.5 Fe 0.5 The mass ratio of PO4 to LiMn is 1:1000. 0.5 Fe 0.5 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 670 nm, and that of LiMn... 0.5 Fe 0.5 The average particle size of PO4 is 86 nm.

[0064] Example 3

[0065] The difference from Example 1 is that 1g of LiF powder was weighed and added in small amounts several times to 20mL of 9M hydrochloric acid aqueous solution under ice bath and stirring conditions to obtain an HF solution. 1g of Ti3AlC2 powder was weighed and added in small amounts several times to the above HF solution under ice bath and stirring conditions for mixing. The mixing temperature was 0℃, the mixing time was 30min, and the stirring speed was 1000r / min. After the mixing treatment, the temperature was increased to 35℃ for a heating reaction, the heating time was 24h, and the stirring speed was 1000r / min to obtain the product Ti3C2.

[0066] The Ti3C2 product was washed with deionized water, and the product and washing liquid were separated by centrifugation at 4000 rpm. Centrifugation was repeated for 5 min in several cycles until the pH reached 5, at which point the washing process was stopped. The precipitate obtained by centrifugation was resuspended in deionized water. The Ti3C2 suspension was then sonicated in an ice bath at 10 °C for 2 h at a frequency of 60 kHz to obtain Ti3C2 suspensions with 1–10 layers. Finally, freeze-drying was used to obtain Ti3C2 sheet-like samples with 1–10 layers, the average planar diameter of which was 1 μm.

[0067] First, prepare a 2 mol / L lithium hydroxide aqueous solution, add 1.67 g of the above-mentioned Ti3C2 flake sample and 25 g of surfactant polyethylene glycol (weight average molecular weight of 2000 g / mol) to form the first mixture; then prepare a 0.4 mol / L ferrous chloride aqueous solution and a 0.6 mol / L manganese chloride aqueous solution, and mix them evenly to form the second mixture.

[0068] The first and second mixtures were thoroughly stirred and sonicated for 30 minutes to disperse them evenly. Then, the second mixture was added dropwise to the first mixture to form the third mixture. Phosphoric acid aqueous solution was added to control the pH of the third mixture to 4. The concentration of the phosphoric acid aqueous solution was 1.0 mol / L. The mixture was stirred and sonicated until completely dissolved.

[0069] The third mixture was transferred to a magnetically stirred hydrothermal reactor and hydrothermally reacted at 170°C for 20 hours. After the reaction was completed, the precursor slurry was obtained.

[0070] The precursor slurry was filtered, washed with water, dried at 60°C for 12 hours, sintered at 750°C for 6 hours under nitrogen protection, and then naturally cooled to room temperature to obtain LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:100. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 620 nm, and that of LiMn... 0.6 Fe 0.4 The average particle size of PO4 is 78 nm.

[0071] Example 4

[0072] The difference from Example 1 is that the added mass of Ti3C2 sheet sample was 16.7g, and the final LiMn 0.6 Fe 0.4Ti3C2 and LiMn in PO4 / Ti3C2 heterojunction cathode materials 0.6 Fe 0.4 The mass ratio of PO4 is 1:10.

[0073] Example 5

[0074] The difference from Example 1 is that the added mass of Ti3C2 sheet sample was 33.4 g, and the final LiMn 0.6 Fe 0.4 Ti3C2 and LiMn in PO4 / Ti3C2 heterojunction cathode materials 0.6 Fe 0.4 The mass ratio of PO4 is 1:5.

[0075] Example 6

[0076] The difference from Example 1 is that the concentration of the ferrous chloride aqueous solution is 0.9 mol / L, and the concentration of the manganese chloride aqueous solution is 0.1 mol / L, ultimately yielding LiMn. 0.1 Fe 0.9 PO4 / Ti3C2 heterojunction cathode material.

[0077] Example 7

[0078] The difference from Example 1 is that the hydrothermal reaction temperature was 160°C and the hydrothermal reaction time was 24 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:1000. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 580 nm, and that of LiMn... 0.6 Fe 0.4 The average particle size of PO4 is 57 nm.

[0079] Example 8

[0080] The difference from Example 1 is that the hydrothermal reaction temperature was 200°C and the hydrothermal reaction time was 16 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:1000. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 680 nm, and that of LiMn... 0.6Fe 0.4 The average particle size of PO4 is 97 nm.

[0081] Example 9

[0082] The difference from Example 1 is that the hydrothermal reaction temperature was 250°C and the hydrothermal reaction time was 12 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:1000. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 760 nm, and that of LiMn... 0.6 Fe 0.4 The average particle size of PO4 is 130 nm.

[0083] Example 10

[0084] The difference from Example 1 is that the sintering temperature was 700℃ and the sintering time was 10 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material.

[0085] Example 11

[0086] The difference from Example 1 is that the sintering temperature was 800℃ and the sintering time was 4 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material.

[0087] Example 12

[0088] The difference from Example 1 is that the sintering temperature was 900℃ and the sintering time was 2 hours, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material.

[0089] Example 13

[0090] The difference from Example 1 is that the mass of polyethylene glycol is 4g, ultimately yielding LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material.

[0091] Example 14

[0092] The difference from Example 1 is that the ultrasonic treatment was omitted, and the product Ti3C2 was washed and directly added to an aqueous lithium hydroxide solution to finally obtain LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material.

[0093] Example 15

[0094] The difference from Example 1 is that 1g of LiF powder was weighed and added in small amounts several times with 20mL of 9M hydrochloric acid solution under ice bath and stirring conditions to obtain an HF solution. 1g of Ti3AlC2 powder was weighed and added in small amounts several times with the above HF solution under ice bath and stirring conditions for mixing. The mixing temperature was 10℃, the mixing time was 120min, and the stirring speed was 500r / min. After the mixing treatment, the temperature was increased to 60℃ for a heating reaction for 48h, with a stirring speed of 500r / min, to obtain the product Ti3C2.

[0095] The Ti3C2 product was washed with deionized water, and the product and washing liquid were separated by centrifugation at 4000 rpm. Centrifugation was repeated for 1 hour each time until the pH reached 6, at which point the washing process was stopped. The precipitate was resuspended in deionized water, and the Ti3C2 suspension was sonicated in an ice bath to obtain a suspension with 1–7 Ti3C2 layers. The sonication temperature was 10℃, the sonication time was 3 hours, and the sonication frequency was 100 kHz. Finally, freeze-drying was used to obtain sheet-like samples with 1–7 Ti3C2 layers, with an average planar diameter of 500 nm.

[0096] First, prepare a 2 mol / L lithium carbonate aqueous solution, add 0.167 g of the above-mentioned Ti3C2 flake sample and 2.5 g of the surfactant sodium dodecylbenzenesulfonate to form the first mixture; prepare a 0.4 mol / L ferrous acetate aqueous solution and a 0.6 mol / L manganese oxalate aqueous solution, and mix them evenly to form the second mixture.

[0097] The first and second mixtures were thoroughly stirred and sonicated for 30 minutes to disperse them evenly. Then, the second mixture was added dropwise to the first mixture to form the third mixture. Phosphoric acid aqueous solution was added to control the pH of the third mixture to 6. The concentration of the phosphoric acid aqueous solution was 2.0 mol / L. The mixture was stirred and sonicated until completely dissolved.

[0098] The third mixture was transferred to a magnetically stirred hydrothermal reactor and hydrothermally reacted at 170°C for 20 hours. After the reaction was completed, the precursor slurry was obtained.

[0099] The precursor slurry was filtered, washed with water, dried at 60°C for 12 hours, sintered at 750°C for 6 hours under nitrogen protection, and then naturally cooled to room temperature to obtain LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 heterojunction cathode material, Ti3C2 and LiMn 0.6 Fe 0.4 The mass ratio of PO4 to LiMn is 1:1000. 0.6 Fe 0.4 The average planar diameter of the PO4 / Ti3C2 heterojunction cathode material is 400 nm, and the average particle size of lithium manganese iron phosphate is 65 nm.

[0100] Comparative Example 1

[0101] The difference from Example 1 is that 2.5g of glucose was used to replace 0.167g of Ti3C2 flake sample, ultimately yielding Mn. 0.6 Fe 0.4 PO4@C cathode material.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that the addition of Ti3C2 sheet-like sample was omitted, ultimately yielding Mn. 0.6 Fe 0.4 PO4 cathode material.

[0104] Comparative Example 3

[0105] The difference from Example 1 is that 1g of LiF powder was weighed and added in small amounts several times to 20mL of 9M hydrochloric acid aqueous solution under ice bath and stirring conditions to obtain an HF solution. 1g of Ti3AlC2 powder was weighed and added in small amounts several times to the above HF solution under ice bath and stirring conditions for mixing. The mixing temperature was 0℃, the mixing time was 30min, and the stirring speed was 1000r / min. After the mixing treatment, the temperature was increased to 35℃ for a heating reaction, the heating time was 24h, and the stirring speed was 1000r / min to obtain the product Ti3C2.

[0106] The Ti3C2 product was washed with deionized water, and the product and washing liquid were separated by centrifugation at 4000 rpm. Centrifugation was repeated for 5 min in several cycles until the pH reached 5, at which point the washing process was stopped. The precipitate obtained by centrifugation was resuspended in deionized water. The Ti3C2 suspension was then sonicated in an ice bath at 10 °C for 2 h at a frequency of 60 kHz to obtain Ti3C2 suspensions with 1–10 layers. Finally, freeze-drying was used to obtain Ti3C2 sheet-like samples with 1–10 layers, the average planar diameter of which was 10 μm.

[0107] First, prepare a 2 mol / L lithium hydroxide aqueous solution to obtain the first mixture; then prepare a 0.4 mol / L ferrous chloride aqueous solution and a 0.6 mol / L manganese chloride aqueous solution, and mix them evenly to form the second mixture.

[0108] The first and second mixtures were thoroughly stirred and sonicated for 30 minutes to disperse them evenly. Then, the second mixture was added dropwise to the first mixture to form the third mixture. Phosphoric acid aqueous solution was added to control the pH of the third mixture to 4. The concentration of the phosphoric acid aqueous solution was 1.0 mol / L. The mixture was stirred and sonicated until completely dissolved.

[0109] The third mixture was transferred to a magnetically stirred hydrothermal reactor and hydrothermally reacted at 170°C for 20 hours. After the reaction was completed, the precursor slurry was obtained.

[0110] The precursor slurry was filtered, washed with water, dried at 60°C for 12 hours, and then mixed with 0.167 g of the above-mentioned Ti3C2 flake sample. The mixture was sintered at 750°C for 6 hours under nitrogen protection and then naturally cooled to room temperature to obtain LiMn. 0.6 Fe 0.4 PO4.

[0111] The above LiMn 0.6 Fe 0.4 PO4 and the above-mentioned Ti3C2 flake sample were ball-milled at a mass ratio of 1:1000 to obtain LiMn. 0.6 Fe 0.4 PO4 / Ti3C2 cathode material.

[0112] Performance testing

[0113] The positive electrode materials prepared in the examples and comparative examples were subjected to powder resistivity testing. The positive electrode materials prepared in the examples and comparative examples were used to prepare positive electrode sheets, which were then assembled into batteries with separators, negative electrode sheets and electrolytes. The 0.2C discharge capacity, 1C discharge capacity and 1C cycle 500 cycles capacity retention were tested. The batteries after 500 cycles were disassembled and the manganese content in the electrolyte was measured. The test results are shown in Table 1.

[0114] Table 1

[0115]

[0116] Figure 1 This is a SEM image of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material in Example 1 of this application. Figure 1 As can be seen from the above, the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application is a uniform two-dimensional heterojunction material without obvious boundaries.

[0117] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0118] Titanium carbide possesses a hydrophilic surface, good electronic conductivity, and electrochemical stability. In the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application, the presence of titanium carbide facilitates the formation of efficient ion and electron transport channels, thereby improving the conductivity and lithium-ion transport rate of lithium manganese iron phosphate. Simultaneously, in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material, some titanium ions occupy the M sites in lithium manganese iron phosphate, forming metal-hole pairs. This helps reduce the Jahn-Teller effect, thereby reducing manganese ion dissolution due to lattice distortion during cycling, and further improving the structural stability and cycle performance of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material. Furthermore, by constructing a heterostructure, titanium carbide absorbs and utilizes lattice oxygen to achieve reversible high capacity and obtains a stable cathode / electrolyte interface, contributing to the stability of the cathode system and thus promoting stable electrochemical performance output. Therefore, the lithium manganese iron phosphate / titanium carbide heterojunction cathode material of this application exhibits high conductivity, lithium-ion conductivity, specific capacity, and cycle life, with low manganese dissolution.

[0119] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium manganese iron phosphate / titanium carbide heterojunction cathode material, characterized in that, The chemical structural formula of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material is LiMn. 1-x Fe x PO4 / Ti3C2, 0.1≤x≤0.

9.

2. The lithium manganese iron phosphate / titanium carbide heterojunction cathode material according to claim 1, characterized in that, The Ti3C2 and the LiMn 1-x Fe x The mass ratio of PO4 is 1:(10 to 1000), preferably 1:(100 to 1000).

3. The lithium manganese iron phosphate / titanium carbide heterojunction cathode material according to claim 1 or 2, characterized in that, The lithium iron phosphate / titanium carbide heterojunction cathode material is formed by in-situ growth of LiMn on the Ti3C2 surface. 1-x Fe x PO4 is obtained; and / or, the lithium manganese iron phosphate / titanium carbide heterojunction cathode material has a sheet-like stacked structure; the average planar diameter of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material is 400-700 nm; preferably, the Ti3C2 in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material has a sheet-like structure of 1-10 layers; and / or, the LiMn in the lithium manganese iron phosphate / titanium carbide heterojunction cathode material... 1-x Fe x The average particle size of PO4 is 10–100 nm; and / or the powder resistivity of the lithium manganese iron phosphate / titanium carbide heterojunction cathode material is 10–600 Ω / m.

4. A method for preparing a lithium manganese iron phosphate / titanium carbide heterojunction cathode material according to any one of claims 1 to 3, characterized in that, The preparation method includes: Step S1: Mix the raw materials including lithium source, Ti3C2, surfactant and water to obtain a first mixture; Step S2: The raw materials including manganese source, ferrous iron source and water are mixed to obtain a second mixture. Step S3: After mixing the first mixture and the second mixture, the pH is adjusted using a phosphoric acid aqueous solution, and then a hydrothermal reaction is carried out to obtain the precursor product. Step S4: The precursor product is sintered under a protective gas to obtain the lithium manganese iron phosphate / titanium carbide heterojunction cathode material.

5. The preparation method according to claim 4, characterized in that, In step S3, the target pH value for pH adjustment is 3-6; and / or, the concentration of the phosphoric acid aqueous solution is 1.0-2.0 mol / L; and / or, the temperature of the hydrothermal reaction is 160-200℃; and / or, the time of the hydrothermal reaction is 16-24 h.

6. The preparation method according to claim 4 or 5, characterized in that, In step S4, the sintering temperature is 700–800°C; and / or the sintering time is 4–10 h.

7. The preparation method according to any one of claims 4 to 6, characterized in that, In step S1, the method for preparing Ti3C2 includes: sequentially mixing Ti3AlC2 and HF solution, heating reaction, and ultrasonic treatment to obtain Ti3C2, wherein the mixing temperature is 0-10℃; and / or, the mixing time is 30-120 min; and / or, the heating reaction temperature is 30-60℃; and / or, the heating reaction time is 24-48 h; and / or, the ultrasonic treatment temperature is 0-10℃; and / or, the ultrasonic treatment time is 0.1-3 h; and / or, the ultrasonic treatment frequency is 10-1000 kHz; preferably, the mixing and heating reactions are both carried out under stirring, and the stirring speed of the mixing and heating reactions is independently 500-10000 r / min.

8. The preparation method according to any one of claims 4 to 7, characterized in that, The mass ratio of Ti3C2 to the surfactant is 0.167:(2-3); Preferably, the lithium source is selected from any one or more of lithium hydroxide, lithium carbonate, lithium oxalate, and lithium dihydrogen phosphate; And / or, the surfactant is selected from any one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinylpyrrolidone, polyethylene glycol, and mercapto polyethylene glycol; And / or, the manganese source is selected from any one or more of manganese dioxide, manganese chloride, manganese sulfate, manganese oxalate, manganese acetate, and manganese nitrate; And / or, the ferrous iron source is selected from any one or more of ferrous chloride, ferrous sulfate, ferrous oxalate, ferrous acetate, and ferrous nitrate.

9. A positive electrode sheet, comprising a positive electrode active layer and a current collector, characterized in that, The positive electrode active layer contains the lithium manganese iron phosphate / titanium carbide heterojunction positive electrode material as described in any one of claims 1 to 3.

10. A lithium-ion battery, comprising a positive electrode, an electrolyte, and a negative electrode, characterized in that, The positive electrode is the positive electrode as described in claim 9.

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