A lithium-rich manganese-based positive electrode material modified by a metal phosphide and a preparation method and application thereof

Abstract

The application discloses a metal phosphide modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The lithium-rich manganese-based positive electrode material comprises a metal phosphide and a lithium-rich manganese positive electrode base material, the metal phosphide is doped in the lithium-rich manganese positive electrode base material, or the lithium-rich manganese positive electrode base material is surface modified. The lithium-rich manganese-based positive electrode material has excellent cycle stability and rate performance, and the capacity does not obviously decrease after 800 cycles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a metal phosphide modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Developing new positive electrode materials with high performance and low cost has always been a hot and important topic in the field of lithium ion batteries. Compared with lithium cobaltate, lithium iron phosphate and high-nickel ternary positive electrode materials, lithium-rich manganese-based positive electrode material xLiMO2·(1-x)Li2MnO3 is expected to become the positive electrode material of the next generation of commercial high-energy lithium ion batteries due to its high specific capacity, low price and good thermal stability. However, as a positive electrode material of lithium ion batteries, lithium-rich manganese-based material has serious voltage hysteresis and capacity / voltage decay, which leads to limited cycle life and needs to be improved.

[0003] At present, domestic and foreign researchers have explored the O 2- failure mechanisms of lithium-rich manganese materials, including peroxide, phase structure evolution, lattice displacement / strain, etc. Various modification methods have been designed and developed, including ion doping, surface modification, pre-lithiation, morphology control, ion exchange, chemical composition and defect structure design, which effectively improve the electrochemical performance of lithium-rich manganese positive electrode materials. Although researchers have gradually deepened their understanding of lithium-rich manganese-based positive electrode materials for lithium ion batteries and made significant improvements, the voltage decay and performance decline caused by the irreversible oxidation and reduction of oxygen in the material still pose challenges to its industrial application.

[0004] The patent with publication number CN118281208A discloses a lithium-rich manganese-based positive electrode material, which comprises a substrate and a coating layer. The chemical formula of the substrate is mLi2MnO3·(1-m)LiTMO2, wherein 0 3-x M 0.05 BS3, x is 0.05 or 0.1 or 0.2 or 0.25, and M is at least one of Cu, Zn, Sn and P. By doping and coating the lithium-rich manganese-based positive electrode material, the structural reversibility of the positive electrode material and the initial coulombic efficiency of the battery are improved. However, the capacity retention of the modified material is about 90% after 100 cycles, and the cycle stability needs to be further improved.

[0005] The patent with publication number CN118507698A uses NaMF4 to coat the lithium-rich manganese-based positive electrode material, where M is one or more of Co, Sc and Y. By coating, the lithium-rich manganese material is protected from corrosion by the electrolyte, and the decomposition of the electrolyte is inhibited, improving the electrochemical performance of the battery. However, the preparation method is hydrothermal method and liquid phase coating method, which needs to be optimized to realize simple preparation of high-performance lithium-rich manganese-based positive electrode materials.

[0006] Therefore, there is an urgent need for an efficient preparation method of lithium-rich manganese-based positive electrode material to solve the problem that the high energy density and long cycle life of the current positive electrode material cannot be considered, and to realize the breakthrough of the energy density, cycle stability and rate performance of lithium ion batteries. SUMMARY

[0007] The application provides a metal phosphide modified lithium-rich manganese-based positive electrode material, which has excellent cycle stability and rate performance, and the capacity does not decrease obviously after 800 cycles.

[0008] The application provides a metal phosphide modified lithium-rich manganese-based positive electrode material, which comprises a metal phosphide and a lithium-rich manganese positive electrode base material, and the metal phosphide is doped in the lithium-rich manganese positive electrode base material or surface-modifies the lithium-rich manganese positive electrode base material.

[0009] Preferably, the metal phosphide is selected from one or more of iron phosphide, nickel phosphide, cobalt phosphide, manganese phosphide, molybdenum phosphide, copper phosphide, titanium phosphide, zinc phosphide, chromium phosphide, vanadium phosphide, scandium phosphide, lithium phosphide, aluminum phosphide, ruthenium phosphide, sodium phosphide and potassium phosphide.

[0010] The application utilizes phosphorus anions and metal cations to cooperatively stabilize the oxygen structure of the lithium-rich manganese positive electrode base material. The phosphorus anions can play the role of redox pairs, improve the charge distribution in the crystal, regulate the distribution of oxygen ions and the local electronic structure, increase the migration energy barrier of the crystal oxygen, and reduce the reaction activity of the crystal oxygen; the metal cations further enhance the bonding strength between oxygen and the crystal metal, cooperatively prevent the peroxidation of oxygen and the migration of transition metal ions, inhibit the release of oxygen at high voltage and the irreversible phase transition from the layered structure to the spinel or rock salt phase, and improve the stability of the crystal structure of the material. In addition, the phosphorus anions and metal cations jointly act at the interface to reduce the side reaction between the electrolyte and the lithium-rich manganese-based material, optimize the migration channel of lithium ions, and enhance the lithium ion diffusion rate and electrical conductivity.

[0011] Further preferably, the metal phosphide is selected from one or more of iron phosphide, manganese phosphide and molybdenum phosphide.

[0012] The iron cations and phosphorus anions in the iron phosphide have multiple valence states, form an electronic coupling effect with transition metals (such as Mn and Ni) in the charging and discharging process, relieve the lattice stress and strain, and enhance the stability of the oxygen structure. In addition, the chemical stability and low interface impedance of the iron phosphide can stabilize the electrode / electrolyte interface and improve the interface compatibility.

[0013] The introduction of manganese phosphide can adjust the coordination environment of manganese in lithium-rich manganese materials, reduce the breaking of Mn-O bonds and the tendency of oxygen release through phosphatization, and maintain the integrity of the layered structure. The high conductivity of manganese phosphide helps form an electron transfer network in the positive electrode material, while optimizing the diffusion path of lithium ions, improving the rate performance and overall conductivity of the material.

[0014] The surface of molybdenum phosphide has high active sites that can promote the kinetics of redox reactions, and the high-valence molybdenum ions in molybdenum phosphide can compensate for the charge balance during the charging and discharging process of lithium-rich manganese-based materials, preventing the overoxidation of oxygen. Molybdenum phosphide has high conductivity and unique electronic structure, which improves the electronic conductivity of lithium-rich manganese positive electrode materials through electronic coupling, optimizes the lithium ion migration path, and reduces the polarization effect during charging and discharging.

[0015] Phosphides of iron, manganese, and molybdenum all have high chemical stability and electronic conductivity, which can maintain their structural integrity in a high-voltage range, while forming chemical bonds with the lithium-rich manganese matrix to stabilize the oxygen structure, effectively improving the electronic conductivity of lithium-rich manganese positive electrodes. In addition, a stable protective layer can be formed at the interface of lithium-rich manganese materials, effectively suppressing electrolyte decomposition and side reactions.

[0016] Further preferably, the metal phosphide is molybdenum phosphide, and the mass percentage of the molybdenum phosphide in the lithium-rich manganese-based positive electrode material is 0.01-0.03%.

[0017] Molybdenum phosphide has the best effect in lithium-rich manganese-based positive electrode materials, due to the combined action of its chemical stability, high conductivity, redox activity, and interface protection ability. Molybdenum phosphide has high chemical and thermal stability, which can maintain stability under high voltage (~4.8V) and multiple cycles; the phosphorus and molybdenum elements in molybdenum phosphide can easily form strong covalent bonds with oxygen atoms in lithium-rich manganese positive electrode materials, significantly enhancing the stability of oxygen and reducing oxygen release; the redox pair of molybdenum (Mo 3+ / Mo 6+ ) and the multi-electron pair of phosphorus anions can effectively compensate for the charge balance and slow down the structural stress when the oxidation state of transition metals changes, maintaining structural stability; the high electronic conductivity and interface stability of molybdenum phosphide effectively improve the electronic and ionic transport properties of lithium-rich manganese positive electrode materials, inhibit the dissolution of transition metal ions, and enhance the interface compatibility of lithium-rich manganese materials.

[0018] At a content of 0.01-0.03%, molybdenum phosphide can be uniformly distributed in the lithium-rich manganese-based material without damaging the crystal structure of the material itself. Too high a content of molybdenum phosphide can cause local distortion of the crystal structure of the lithium-rich manganese material, increase the lattice stress, and reduce the electrochemical performance. When the content of molybdenum phosphide is too high, a too thick protective layer of molybdenum phosphide and impurities such as molybdenum oxide or phosphorus compounds can be formed on the surface of the lithium-rich manganese positive electrode, hindering the diffusion and migration of lithium ions and causing additional side reactions, resulting in poor electrochemical performance. A proper content of molybdenum phosphide can significantly improve the overall conductivity of the lithium-rich manganese positive electrode material and effectively stabilize the surface oxygen structure without excessively changing the intrinsic properties of the material. Within this range, the content of molybdenum phosphide is moderate, which can fully exert the synergistic modification effect of molybdenum and phosphorus elements, and can also avoid negative effects such as ion channel blockage, lattice distortion, or generation of impurities. Therefore, at a proper content, the electrochemical performance of the material is maximally improved.

[0019] Preferably, the mass percentage of the metal phosphide in the lithium-rich manganese-based positive electrode material is 0.01-10%.

[0020] A content that is too low (<0.01%) cannot significantly improve the oxygen structure stability and electrochemical performance of the lithium-rich manganese material, and the improvement in conductivity and interface compatibility is limited, and the performance improvement of the material is not obvious. A content that is too high (>10%) can introduce impurities or interface side reactions, damage the crystal structure stability, hinder the migration of lithium ions, increase the interface impedance, and reduce the rate performance and energy density. Within a content range of 0.01-10%, the metal phosphide can be uniformly distributed, significantly improve the oxygen stability, conductivity, and interface compatibility, and avoid excessive side effects. This range achieves the best balance between performance improvement and material economy.

[0021] Preferably, the structure general formula of the lithium-rich manganese positive electrode substrate is xLi2MnO3-(1-x)LiMO2; wherein M is selected from one or more of Ni, Co, Mn, Ti, Cr, Fe, Al, Nb, Mo, Ru, and 0≤x≤1.

[0022] In another aspect, the present application also provides a preparation method of the lithium-rich manganese-based positive electrode material modified by the metal phosphide, comprising:

[0023] After pyrolysis of the lithium-rich manganese positive electrode substrate precursor, the lithium-rich manganese positive electrode substrate precursor is mixed with the metal phosphide to obtain a lithium-rich manganese-based positive electrode material doped with the metal phosphide after high-temperature calcination;

[0024] Alternatively, the lithium-rich manganese positive electrode substrate, the metal phosphide, the conductive agent, the binder, and the solvent are uniformly mixed to form a slurry, and the slurry is coated on the current collector to obtain the lithium-rich manganese-based positive electrode material modified by the surface of the metal phosphide after drying.

[0025] The lithium-rich manganese-based positive electrode material provided by the application has simple preparation process and high efficiency, and is expected to realize commercial application of high-capacity lithium-rich manganese-based materials.

[0026] The preparation method of the disclosed metal phosphide modified lithium-rich manganese-based positive electrode material is a conventional mixing and coating method in the art, and the positive electrode material is obtained by introducing the metal phosphide in the calcination process of the lithium-rich manganese-based positive electrode material or the electrode preparation process, so that the method is simple, the material preparation is controllable, and the method is suitable for industrial production.

[0027] In the process of preparing the metal phosphide doped lithium-rich manganese-based positive electrode material, the following steps are performed:

[0028] Preferably, the method for preparing the lithium-rich manganese positive electrode base material precursor comprises a spray drying method, a coprecipitation method, a sol-gel method, a combustion method, a solid phase method or a molten salt method.

[0029] Further preferably, the lithium-rich manganese positive electrode base material precursor prepared by the spray drying method comprises the following steps:

[0030] The raw materials are proportioned according to the molar percentage of each component of the lithium-rich manganese positive electrode base material, and then added into deionized water to form a mixed solution, a complexing agent is added into the mixed solution, and the mixed solution is stirred uniformly to obtain a metal salt precursor solution;

[0031] The metal salt precursor solution is sprayed, dried and ground by using the spray drying method to obtain the lithium-rich manganese positive electrode base material precursor.

[0032] By using the spray drying method, the raw materials are mixed in a liquid, and compared with the existing solid mixing, the distribution of Li elements in the prepared lithium-rich manganese positive electrode base material precursor is more uniform.

[0033] Further preferably, the raw materials are acetate, nitrate, sulfate, carbonate, oxalate or metal oxide.

[0034] Further preferably, the raw materials are acetate.

[0035] The acetate salt (such as manganese acetate, nickel acetate, etc.) has good solubility in water or an organic solvent, can form a uniform precursor solution, ensures uniform distribution of ions in the atomization process, avoids agglomeration between metal ions, and ensures uniform particle composition; the melting point of the acetate salt is low, and the acetate salt can be decomposed into a metal oxide at a lower temperature, so that the calcination stage after spray drying is easier to control; the acetate salt solution has low viscosity and can be uniformly evaporated, has relatively strong surface tension, and is easy to form regular particles, so that the obtained precursor with good bulk density can optimize the reaction efficiency of subsequent calcination; the decomposition product of the acetate salt is relatively simple, and it is difficult to generate by-products (such as sulfate) that are difficult to remove (such as sulfate), thereby reducing the influence on the subsequent battery performance; the purity of the acetate salt is high, and the sulfate salt may introduce residual sulfate, and the chloride generates corrosive chloride ions, and the products (such as CO2 and H2O) released in the decomposition process of the acetate salt are harmless to the environment. As an industrial chemical, the acetate salt is widely available and moderately priced, and is more suitable for large-scale production.

[0036] Preferably, the pyrolysis temperature is 200-700℃, and the heat treatment time is 0.5-8 hours.

[0037] Preferably, the method for uniformly mixing the lithium-rich manganese positive electrode substrate precursor after pyrolysis with the metal phosphide includes grinding, ball milling, mechanical stirring, or magnetic stirring.

[0038] Preferably, the calcination atmosphere is air, oxygen, or vacuum, the calcination temperature is 600-1100℃, and the treatment time is 2-24h.

[0039] Preferably, the lithium-rich manganese positive electrode substrate material is selected from a cobalt-free lithium-rich manganese-based positive electrode material 0.5Li2MnO3-0.5LiNi 0.5 Mn 0.5 O2.

[0040] Preferably, the metal phosphide is selected from one or more of iron phosphide, manganese phosphide, and molybdenum phosphide.

[0041] In the preparation of the lithium-rich manganese-based positive electrode material with a metal phosphide surface modification process of the present application:

[0042] Preferably, the lithium-rich manganese positive electrode substrate material is selected from a cobalt-free lithium-rich manganese-based positive electrode material 0.5Li2MnO3-0.5LiNi 0.5 Mn 0.5 O2.

[0043] Preferably, the metal phosphide is selected from one or more of iron phosphide, manganese phosphide, and molybdenum phosphide.

[0044] Preferably, the conductive agent is selected from one or more of graphite, acetylene black, Super P, carbon nanotubes, graphene, and Ketjen black.

[0045] Preferably, the binder is selected from one or more of vinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene butadiene rubber, sodium carboxymethyl cellulose, sodium alginate.

[0046] Preferably, the current collector is one or more of aluminum foil, carbon-coated aluminum foil, nickel foil.

[0047] Preferably, the solvent is selected from water or a mixed solvent composed of water and an organic solvent, which is adaptively selected according to the type of binder used.

[0048] Further, the binder is selected from sodium carboxymethyl cellulose, and the solvent is selected from water.

[0049] In another aspect, the present application also provides a use of the metal phosphide-modified lithium-rich manganese-based positive electrode material in a lithium ion battery, comprising:

[0050] An anode sheet prepared from the metal phosphide-modified lithium-rich manganese-based positive electrode material is assembled with a negative electrode and an electrolyte to obtain a lithium ion battery.

[0051] Preferably, the negative electrode is a graphite-based carbon negative electrode, a silicon-based negative electrode, a metal oxide negative electrode, or a lithium metal negative electrode, etc.

[0052] Preferably, the electrolyte also uses an organic electrolyte commonly used in the art, which comprises a lithium salt and an organic solvent, the lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis-trifluoromethylsulfonylimide (LiTFSI); the organic solvent is one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC).

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] The present application regulates the bulk structure or the surface and interface structure of the lithium-rich manganese-based positive electrode material by introducing a metal phosphide, the metal cation and the phosphorus anion jointly stabilize the oxygen structure of the lithium-rich manganese material, prevent the peroxidation of oxygen and the migration of transition metal, improve the crystal structure stability of the material, and effectively improve the capacity retention rate, voltage retention rate, and rate performance of the lithium-rich manganese-based positive electrode material in the process of charge and discharge long cycle. The lithium ion battery assembled with the lithium-rich manganese-based positive electrode material has no obvious loss in capacity after 800 cycles at a current density of 1C (1C = 200 mA / g). BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The charge and discharge and cycle performance curves of the battery assembled in Example 1 of the present application, wherein, Figure 1 (a) is the first charge and discharge curve; Figure 1(b) is a plot of 0.1 C cycle performance; Figure 1 (c) is a plot of 1 C cycle performance;

[0056] Figure 2 Plot of discharge median voltage during cycling for a battery assembled according to Example 1 of the invention;

[0057] Figure 3 Plot of positive active material energy density cycling for a battery assembled according to Example 1 of the invention;

[0058] Figure 4 Plot of first charge-discharge at a current density of 0.1 C (20 mA / g) for a battery assembled according to Example 2 of the invention;

[0059] Figure 5 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 2 of the invention;

[0060] Figure 6 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 4 of the invention;

[0061] Figure 7 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 5 of the invention;

[0062] Figure 8 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 7 of the invention;

[0063] Figure 9 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 8 of the invention;

[0064] Figure 10 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 9 of the invention;

[0065] Figure 11 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 11 of the invention;

[0066] Figure 12 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Example 12 of the invention;

[0067] Figure 13 Plot of cycle performance at a current density of 1 C (200 mA / g) for a battery assembled according to Comparative Example 1 of the invention;

[0068] Figure 14 The cycle performance curve of the battery assembled for Invention Comparative Example 2 at a current density of 1C (200 mA / g). DETAILED DESCRIPTION

[0069] The application will be further described in conjunction with the following examples, which are not intended to limit the scope of the application. The materials involved in the examples are commercially available products.

[0070] Example 1

[0071] (1) The lithium-rich manganese-based positive electrode material was prepared by spray drying combined with high-temperature solid-phase sintering. Specifically, 29.19 g of CH3COOLi·2H2O (99.9%), 11.19 g of Ni(CH3COO)2·4H2O (99.9%), and 33.08 g of Mn(CH3COO)2·4H2O (99.9%) were weighed according to the molar ratio Li:Ni:Mn = 1.272:0.2:0.6, added to 1.5 L of deionized water to form a 0.15 mol / L aqueous solution, and then 94.56 g of C6H8O7·H2O (99.5%, 0.3 mol / L) was added as a complexing agent. The transparent metal salt precursor solution was obtained by mechanical stirring combined with ultrasonic treatment for 10 min. Then the reaction solution was sent to the nozzle of the spray dryer using a peristaltic pump, the pump speed was set to 15 rpm, the inlet temperature was set to 230°C, and the outlet temperature was set to 100°C. The spray-dried precursor was collected, ground and crushed, and then placed in an alumina crucible and heated in a muffle furnace under air atmosphere at 900°C for 10 h, with a heating rate of 3°C / min, and the furnace was cooled to obtain Li -1 Mn -1 Ni -1 O2 positive electrode material. 1.2 0.6 0.2

[0072] Li 1.2 Mn 0.6 Ni 0.2 O2 and conductive agent Super P were weighed according to a mass ratio of 8:1, and 3wt% of Mn3P2 (accounting for Li 1.2 Mn 0.6 Ni 0.2 ​​​The Li2CO3, Mn3P2, and conductive agent Super P were weighed according to the mass ratio of 8:1:1, and 5wt% and 1wt% of Mn3P2 were added, respectively, to obtain 1wt% Mn3P2 and 5wt% Mn3P2 surface-modified lithium-rich manganese positive electrode sheets, respectively, denoted as 5wt% Mn3P2-Li and 1wt% Mn3P2-Li. 1.2 Mn 0.6 Ni 0.2 O2.

[0073] The electrochemical performance of the positive electrode sheets prepared in this example was characterized using a Cr2025 button cell. Li 1.2 Mn 0.6 Ni 0.2 O2 positive electrode sheets were cut into 10mm electrode sheets, weighed, and placed in a vacuum oven at 110°C to remove moisture on the surface of the electrode sheets, and then assembled in an argon-filled glove box (water and oxygen content is less than 0.1ppm). A metal lithium sheet was used as the counter electrode, the separator was Celgard-2400, and the electrolyte was an EC / DEC / EMC (volume ratio of 1:1:1) solution containing LiPF6 (1mol L -1 ). The active material loading of all electrode sheets was 2.0±0.5mg cm -2 . The electrochemical performance of the button cell was tested by constant current charge and discharge, and the test voltage range was 2.0-4.8V.

[0074] Example 2-3

[0075] The preparation process of the lithium-rich manganese positive electrode sheets of Example 2-3 and the assembly and test conditions of the button cell thereof were the same as those of Example 1, except that the Li 1.2 Mn 0.6 Ni 0.2 O2 powder and conductive agent Super P were weighed according to the mass ratio of 8:1, and 5wt% and 1wt% of Mn3P2 were added, respectively, to obtain 1wt% Mn3P2 and 5wt% Mn3P2 surface-modified lithium-rich manganese positive electrode sheets, respectively, denoted as 5wt% Mn3P2-Li and 1wt% Mn3P2-Li. 1.2 Mn 0.6 Ni 0.2 O2 and 1wt% Mn3P2-Li 1.2 Mn 0.6 Ni 0.2 O2.

[0076] Example 4

[0077] Example 2-3 Preparation process of lithium-rich manganese positive plate and assembly test conditions of its button cell are the same as those of Example 1, except that Li 1.2 Mn 0.6 Ni 0.2 O2 powder and conductive agent Super P, 4wt% Fe3P was added to obtain 4wt% Fe3P surface modified lithium-rich manganese positive plate, marked as 4wt% Fe3P-Li 1.2 Mn 0.6 Ni 0.2 O2.

[0078] Example 5-7

[0079] Example 5-7 Preparation process of lithium-rich manganese positive plate and assembly test conditions of its button cell are the same as those of Example 1, except that Li 1.2 Mn 0.6 Ni 0.2 O2 powder and conductive agent Super P, 3wt%, 2wt%, 1wt% Fe3P was added respectively to obtain Fe3P surface modified lithium-rich manganese positive plate, marked as 3wt% Fe3P-Li 1.2 Mn 0.6 Ni 0.2 O2, 2wt% Fe3P-Li 1.2 Mn 0.6 Ni 0.2 O2 and 1wt% Fe3P-Li 1.2 Mn 0.6 Ni 0.2 O2.

[0080] Example 8

[0081] Example 8 Preparation process of lithium-rich manganese spray drying precursor and assembly test conditions of its button cell are the same as those of Example 1, except that the lithium-rich manganese precursor after spray drying was calcined at 500°C for 5h with a temperature rising rate of 3°C / min -1 , and then cooled in the furnace and ground. After that, the MoP was fully mixed with the lithium-rich manganese material according to the ratio of Ni:Mn:MoP=0.2:0.6:0.005, and the obtained mixture was put into a muffle furnace and calcined at 900°C for 10h with a temperature rising rate of 3°C / min -1 , and then cooled in the furnace and ground to obtain MoP doped Li 1.2 Mn 0.6 Ni 0.2 O2 positive electrode material, marked as Li 1.2 Mn 0.6 Ni 0.2 O2-0.005MoP.

[0082] Examples 9-10

[0083] The preparation process of the lithium-rich manganese spray-dried precursor in Examples 9-10 and the assembly and testing conditions of its coin cells are the same as in Example 1. The difference from Example 1 is that the spray-dried lithium-rich manganese precursor is subjected to a temperature of 3°C for 1 minute. -1 The mixture was heated to 500℃ and calcined for 5 hours. After cooling and grinding in the furnace, it was mixed with MoP at Ni:Mn:MoP molar ratios of 0.2:0.6:0.01 and 0.2:0.6:0.03, respectively. The resulting mixture was placed in a muffle furnace under air atmosphere and heated at 3℃ for 1 minute. -1 The Li was calcined at 900℃ for 10 hours, then cooled and ground in the furnace to obtain MoP-doped Li. 1.2 Mn 0.6 Ni 0.2 O2 cathode materials, denoted as Li 1.2 Mn 0.6 Ni 0.2 O2-0.01MoP and Li 1.2 Mn 0.6 Ni 0.2 O2-0.03MoP.

[0084] Example 11

[0085] Example 11: The preparation process of the lithium-rich manganese spray-dried precursor and the assembly and testing conditions of its coin cell are the same as in Example 1. The difference is that the spray-dried lithium-rich manganese precursor is subjected to a temperature of 3°C for 1 minute. -1 The mixture was heated to 500℃ and calcined for 5 hours. After cooling and grinding in the furnace, it was thoroughly mixed with Fe3P at a ratio of Ni:Mn:Fe3P = 0.2:0.6:0.005. The resulting mixture was then placed in a muffle furnace and heated at 3℃ for 1 minute under an air atmosphere. -1 Calcination was carried out at 900℃ for 10 hours, followed by furnace cooling and grinding to obtain Fe3P-doped Li. 1.2 Mn 0.6 Ni 0.2 O2 cathode material, denoted as Li 1.2 Mn 0.6 Ni 0.2 O2-0.005Fe3P.

[0086] Examples 12-13

[0087] The preparation process of the lithium-rich manganese spray-dried precursor in Examples 9-10 and the assembly and testing conditions of its coin cells are the same as in Example 1. The difference from Example 1 is that the spray-dried lithium-rich manganese precursor is subjected to a temperature of 3°C for 1 minute. -1heated to 500℃ and calcined for 5h, cooled in the furnace and grinded, then mixed with Fe3P at the molar ratio of Ni:Mn:Fe3P of 0.2:0.6:0.01 and 0.2:0.6:0.03 respectively, the obtained mixture was put into a muffle furnace under air atmosphere at the rate of 3℃min -1 heated to 900℃ and calcined for 10h, cooled in the furnace and grinded to obtain Fe3P doped Li 1.2 Mn 0.6 Ni 0.2 O2 cathode material, respectively denoted as Li 1.2 Mn 0.6 Ni 0.2 O2-0.01Fe3P and Li 1.2 Mn 0.6 Ni 0.2 O2-0.03Fe3P.

[0088] Comparative Example 1

[0089] Comparative Example 1 spray-dried lithium-rich manganese precursor is the same as Example 1, which is different from Example 1 that the lithium-rich manganese precursor is put into a muffle furnace under air atmosphere at the rate of 3℃min -1 heated to 900℃ and calcined for 10h, cooled in the furnace and grinded to obtain Li 1.2 Mn 0.6 Ni 0.2 O2 cathode material,

[0090] Comparative Example 2

[0091] Comparative Example 2 spray-dried lithium-rich manganese precursor is the same as Example 1, which is different from Example 1 that the spray-dried lithium-rich manganese precursor is put into a muffle furnace under air atmosphere at the rate of 3℃min -1 heated to 500℃ and calcined for 5h, cooled in the furnace and grinded, then put into a muffle furnace under air atmosphere at the rate of 3℃min -1 heated to 900℃ and calcined for 10h, cooled in the furnace and grinded to obtain Li 1.2 Mn 0.6 Ni 0.2 O2 cathode material.

[0092] As Figure 1 shown, Figure 1In the figures, (a) shows the initial charge-discharge curve of the battery assembled in Example 1 at a current density of 0.1C (20 mA / g), with an initial discharge specific capacity as high as 290 mAh / g and an initial coulombic efficiency of 82%. (b) shows the rate performance curve of the battery assembled in Example 1, exhibiting high discharge specific capacities at 0.1C, 0.5C, 1C, 2C, 5C, and 10C. It still delivers specific capacities of 175 mA / g and 146 mAh / g at high rates of 5C and 10C, respectively, demonstrating excellent rate performance. (c) shows the cycle performance curve of the battery assembled in Example 1 at a current density of 1C (200 mA / g). During cycling, the discharge specific capacity increases slowly in the initial stage, and after approximately 400 cycles, it still delivers a specific capacity of 207 mAh / g, with a capacity retention of 97%, demonstrating excellent cycle stability.

[0093] Figure 2 The image shows the median discharge voltage curve during the cycling process of the battery assembled in Example 1. The results show that the median discharge voltage of the material in this example is 2.98V after 400 cycles, with a retention rate of 85%. Figure 3 The energy density cycling curve of the positive electrode active material of the battery assembled in Example 1 shows that the energy density of the active material after 400 cycles is 649 Wh / kg, with a retention rate of 86%, demonstrating good voltage retention and energy density retention.

[0094] Figure 4 The first charge-discharge curve of the battery assembled in Example 2 at a current density of 0.1C (20mA / g) shows that the first discharge specific capacity is 261mAh / g. Figure 5 The image shows the cycling performance curves of the battery assembled in Example 2 at a current density of 1C (200 mA / g). During cycling, the discharge specific capacity increases slowly in the initial stage, and after 400 cycles, it can still release a specific capacity of 208 mAh / g, with a capacity retention rate of 87%, demonstrating good cycling stability.

[0095] Figure 6 The cycling performance curve of the battery assembled in Example 4 at a current density of 1C (200mA / g) shows that after 450 cycles, it can still release a specific capacity of 188mAh / g, with a capacity retention rate of 91%, demonstrating good cycling stability.

[0096] Figure 7 The image shows the cycling performance curves of the battery assembled in Example 5 at a current density of 1C (200 mA / g). During cycling, the discharge specific capacity increases slowly in the initial stage, and after 450 cycles, it can still release a specific capacity of 155 mAh / g, with a capacity retention of 85%, indicating that the proportion of metal phosphide introduced affects the cycling stability. Figure 7The cycle performance curve of the battery assembled for Example 5 at a current density of 1C (200 mA / g) is shown. During the cycle process, the initial stage discharge specific capacity slowly increases, and after 450 cycles, the specific capacity of 155 mAh / g can still be released, and the capacity retention rate is 85%, indicating that the proportion of the introduced metal phosphide affects the cycle stability.

[0097] Figure 8 The cycle performance curve of the battery assembled for Example 7 at a current density of 1C (200 mA / g) is shown. After 450 cycles, the specific capacity of 171 mAh / g can still be released, and the capacity retention rate is 92%, showing good cycle stability.

[0098] Figure 9 The cycle performance curve of the battery assembled for Example 8 at a current density of 1C (200 mA / g) is shown. During the cycle process, the initial stage discharge specific capacity slowly increases, and after 800 cycles, the specific capacity of 180 mAh / g can still be released, and the capacity does not obviously decay, showing excellent cycle stability.

[0099] Figure 10 The cycle performance curve of the battery assembled for Example 9 at a current density of 1C (200 mA / g) is shown. During the cycle process, the initial stage discharge specific capacity slowly increases, and after 800 cycles, the specific capacity of 176 mAh / g can still be released, and the capacity does not obviously decay, showing excellent cycle stability.

[0100] Figure 11 The cycle performance curve of the battery assembled for Example 11 at a current density of 1C (200 mA / g) is shown. During the cycle process, the initial stage discharge specific capacity slowly increases, and after 450 cycles, the specific capacity of 179 mAh / g can still be released, and the capacity retention rate is 98%, showing excellent cycle stability.

[0101] Figure 12 The cycle performance curve of the battery assembled for Example 12 at a current density of 1C (200 mA / g) is shown. During the cycle process, the initial stage discharge specific capacity slowly increases, and after 450 cycles, the specific capacity of 152 mAh / g can still be released, and the capacity retention rate is 86%, indicating that the proportion of the introduced metal phosphide affects the cycle stability.

[0102] Figure 13 The cycle performance curve of the battery assembled for Comparative Example 1 at a current density of 1C (200 mA / g) is shown. During the cycle process, the discharge specific capacity rapidly decays, and after 450 cycles, the discharge specific capacity is close to zero.

[0103] Figure 14The cycle performance curve of the battery assembled for Comparative Example 2 at a current density of 1C (200 mA / g) is shown in Figure 2. During the cycle process, the capacity gradually decays, and a specific capacity of 92 mAh / g is released after 700 cycles, and the capacity retention rate is 50%, indicating that the lithium-rich manganese-based material without the addition of metal phosphide has poor cycle stability.

Claims

1. A lithium-rich manganese-based cathode material modified with metal phosphide, characterized in that, The lithium-rich manganese-based cathode material includes a metal phosphide and a lithium-rich manganese cathode substrate, wherein the metal phosphide is doped into the lithium-rich manganese cathode substrate or the lithium-rich manganese cathode substrate is surface-modified. The metal phosphide is selected from one or more of the following: iron phosphide, nickel phosphide, cobalt phosphide, manganese phosphide, molybdenum phosphide, copper phosphide, titanium phosphide, zinc phosphide, chromium phosphide, vanadium phosphide, scandium phosphide, lithium phosphide, aluminum phosphide, ruthenium phosphide, sodium phosphide, and potassium phosphide. The metal phosphide in the lithium-rich manganese-based cathode material has a mass percentage of 0.01-10%. The general structural formula of the lithium-rich manganese cathode substrate is xLi2MnO3-(1-x)LiMO2; wherein M is selected from one or more of Ni, Co, Mn, Ti, Cr, Fe, Al, Nb, Mo, and Ru, and 0≤x≤1.

2. The lithium-rich manganese-based cathode material modified with metal phosphide according to claim 1, characterized in that, The metal phosphide is selected from one or more of iron phosphide, manganese phosphide, and molybdenum phosphide.

3. The lithium-rich manganese-based cathode material modified with metal phosphide according to claim 2, characterized in that, The metal phosphide is molybdenum phosphide, and the mass percentage of molybdenum phosphide in the lithium-rich manganese-based cathode material is 0.01-0.03%.

4. A method for preparing a lithium-rich manganese-based cathode material modified with metal phosphide according to any one of claims 1-3, characterized in that, include: The lithium-rich manganese cathode substrate precursor was pyrolyzed and then mixed with metal phosphide. After high-temperature calcination, the lithium-rich manganese-based cathode material doped with metal phosphide was obtained. Alternatively, a lithium-rich manganese cathode substrate, a metal phosphide, a conductive agent, a binder, and a solvent are mixed evenly to form a slurry. The slurry is then coated onto a current collector and dried to obtain the metal phosphide-modified lithium-rich manganese-based cathode material.

5. The method for preparing the phosphide-modified lithium-rich manganese-based cathode material according to claim 4, characterized in that, The lithium-rich manganese cathode substrate precursor prepared by spray drying includes the following steps: The raw materials are prepared according to the molar percentage of each component of the lithium-rich manganese cathode substrate, and then added to deionized water to form a mixed solution. A complexing agent is added to the mixed solution and stirred evenly to obtain a metal salt precursor solution. A lithium-rich manganese cathode substrate precursor was obtained by spray drying, drying, and grinding a metal salt precursor solution.

6. The method for preparing the phosphide-modified lithium-rich manganese-based cathode material according to claim 5, characterized in that, The raw materials are acetates, nitrates, sulfates, carbonates, oxalates, or metal oxides.

7. The application of a lithium-rich manganese-based cathode material modified with metal phosphide according to any one of claims 1-3 in a lithium-ion battery, characterized in that, include: A lithium-ion battery is obtained by assembling a positive electrode sheet prepared with the lithium-rich manganese-based positive electrode material modified with the metal phosphide, along with a negative electrode and an electrolyte.

Images