A lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide and its preparation method

Abstract

The present invention discloses a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide, and a preparation method thereof. By combining freeze-drying and calcination techniques, dual uniform coating of molybdenum disulfide and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based cathode material is achieved. This dual coating layer can not only serve as a stable protective layer to prevent the cathode material from being eroded, but also utilize the physical and electrochemical compatibility between molybdenum and niobium, two adjacent elements in the same period, to form a stable coating structure, thereby optimizing the electrochemical performance and avoiding the occurrence of the "deoxygenation" phenomenon. Under the co-coating of molybdenum disulfide and lithium lanthanum niobium oxide, the present invention obtains a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide that can not only ensure the initial efficiency and specific capacity of the battery, but also fully optimize the cycle performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion batteries, and particularly to a lithium - rich manganese - based cathode material co - coated with molybdenum disulfide and lithium lanthanum niobium oxide and a preparation method thereof. Background Art

[0002] To achieve rechargeable batteries with high energy density of 400 Wh kg -1 and above, in addition to the continuous progress of the cell process, it also depends on the innovation of the core material system. Among them, lithium - rich manganese - based layered oxides are widely used as cathode materials for batteries due to their extremely high specific capacity (> 250 mAhg -1 ), low cost, environmental friendliness and other advantages.

[0003] Lithium - rich manganese - based materials can generally be written as xLi2MnO3·(1–x)LiTMO2. Because of their low cost (mainly manganese element with low cost and less noble metal content), high theoretical specific capacity (> 250 mAh g -1 ), high working voltage and high capacity, they have been widely studied. However, along with the high - capacity performance, lithium - rich manganese - based materials also face problems such as oxygen loss, voltage decay and structure degradation caused by cation migration in the bulk structure, lattice stress accumulation, lattice oxygen evolution and interfacial side reactions. At present, although there are methods such as doping hetero - elements or surface coating to modify them, the doping components are usually difficult to control, and may have certain side effects on the capacity of lithium - rich manganese - based cathode materials; while too thick or uneven surface coating layers will affect the intercalation and de - intercalation of lithium ions in the cathode, resulting in a decline in the rate performance of the modified materials. It is not easy to obtain a lithium - rich manganese - based material that can both inhibit oxygen loss and avoid battery performance degradation, and at the same time improve the first - cycle Coulomb efficiency, specific capacity, rate performance and cycle performance of the battery. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention proposes a lithium - rich manganese - based cathode material co - coated with molybdenum disulfide and lithium lanthanum niobium oxide, which constructs a double coating on the surface of the lithium - rich manganese - based cathode material. While improving the stability of the cathode, the complexation effect between molybdenum disulfide and lithium lanthanum niobium oxide is used to optimize the electrochemical performance, avoid the occurrence of "de - oxygenation", and thus optimize the cycle performance of the lithium - rich manganese - based cathode material when used as a cathode.

[0005] In the first aspect, the present invention proposes a lithium - rich manganese - based cathode material LRO - MLN co - coated with molybdenum disulfide and lithium lanthanum niobium oxide. The surface of the lithium - rich manganese - based cathode material has a co - coating layer containing molybdenum disulfide and lithium lanthanum niobium oxide. The general formula of the O2 - type lithium - rich manganese - based cathode material is Li 1+x Ni y Co z Mn q TM 1-y-z-qO2, where 0 < x ≤ 0.5, 0 < y ≤ 0.3, 0 < z ≤ 0.3, 0.2 < q ≤ 0.7, 1 - y - z - q ≥ 0, TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide lithium lanthanum niobium oxide is Li 4+f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or a high-valence metal substituting for niobium, specifically including one or more of titanium, zirconium, tantalum, manganese, and molybdenum. The percentage of the 5C rate discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide to the 1C rate discharge capacity is greater than or equal to 65%, and the percentage of the 10C rate discharge capacity to the 1C rate discharge capacity is greater than or equal to 45%.

[0006] As some exemplary preferred embodiments, in the lithium-rich manganese-based cathode material, it is Li 1+x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide lithium lanthanum niobium oxide is Li 4+ f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or a high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum.

[0007] As some exemplary preferred embodiments, in the lithium-rich manganese-based cathode material, it is Li 1+x Ni y Co z Mn q TM 1-y-z-qO₂, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide is Li 4+f La i-a M a Nb j- b N b O 12 , where 0.5 ≤ f < 1.5, 2.8 ≤ i - a < 3.2, 1.9 ≤ j - b < 2.1, 0 ≤ a ≤ 0.4, 0 ≤ b ≤ 0.25, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum.

[0008] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 5C rate in the discharge capacity at 1C rate is greater than or equal to 66%, 67%, 68%, 69%.

[0009] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 5C rate in the discharge capacity at 1C rate is greater than or equal to 70%.

[0010] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 10C rate in the discharge capacity at 1C rate is greater than or equal to 46%, 47%, 48%, 49%.

[0011] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 10C rate in the discharge capacity at 1C rate is greater than or equal to 50%.

[0012] As a further solution, ammonium tetrathiomolybdate is used as one of the LRO-MLN raw materials, and its mass ratio in the raw materials is 0.5 - 1.8 wt%.

[0013] As a further solution, the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw materials is 0.8 - 1.5 wt%.

[0014] As a further solution, the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.2 - 0.8 wt%.

[0015] As a further solution, the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.4 - 0.6 wt%.

[0016] As a further solution, the 5C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 165 mAh g -1 -180 mAh g -1 .

[0017] As a further solution, the 5C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 170 mAh g -1 -178 mAh g -1 .

[0018] As a further solution, the 10C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 115 mAh g -1 -125 mAh g -1 .

[0019] As a further solution, the 10C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 118 mAh g -1 -123 mAh g -1 .

[0020] In a second aspect, the present invention also provides a preparation method for a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide. The preparation steps are as follows:

[0021] S1: Mix a lithium source, a lanthanum source, ammonium niobium oxalate, ammonium tetrathiomolybdate, and a lithium-rich manganese-based cathode material in a solvent to form a homogeneous solution;

[0022] S2: Freeze-dry the mixed solution for 4 h to 8 h, then remove the solvent and perform calcination to obtain the lithium-rich manganese-based cathode material LRO-MLN co-coated with molybdenum disulfide and lithium lanthanum niobium oxide.

[0023] As a further solution, in step S1, the lithium source is selected from any one or more of lithium carbonate, lithium nitrate, lithium hydroxide, and lithium oxide.

[0024] As a further solution, in step S1, the lanthanum source is selected from any one or more of lanthanum oxide, lanthanum nitrate, lanthanum carbonate, and lanthanum acetate.

[0025] As a further solution, in step S1, the lithium-rich manganese-based cathode material is obtained by mixing a precursor lithium source and a carbonate precursor in a stoichiometric ratio, ball-milling, and calcining and annealing.

[0026] As a further solution, the precursor lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium fluoride, lithium oxide, lithium chloride, lithium dihydrogen phosphate, lithium oxalate, lithium sulfate, lithium formate, and lithium iodide.

[0027] As a further solution, the carbonate precursor satisfies the general formula Ni g Co h Mn k CO3, 0.14 ≤ g ≤ 0.18, 0.14 ≤ h ≤ 0.18, 0.52 ≤ k ≤ 0.72.

[0028] As a further solution, the stoichiometric ratio of the precursor lithium source to the carbonate precursor is 1:1.35 - 1:1.45.

[0029] As a further solution, the mixed ball milling speed is 200 - 400 r / min.

[0030] As a further solution, the calcination temperature in the preparation process of the lithium-rich manganese-based cathode material is selected from any one of low-temperature calcination (250°C to 350°C), medium-temperature calcination (500°C to 800°C), or high-temperature calcination (900°C to 1000°C).

[0031] As a further solution, the calcination temperature in the preparation process of the lithium-rich manganese-based cathode material is selected from any one of medium-temperature calcination (500°C to 800°C) or high-temperature calcination (900°C to 1000°C).

[0032] As a further solution, the calcination time in the preparation process of the lithium-rich manganese-based cathode material is 4h to 6h, and the calcination atmosphere is air.

[0033] As a further solution, in step S1, the lithium lanthanum niobium oxide raw materials (lithium source, lanthanum source, and ammonium oxalate niobate) are respectively dissolved in a solvent and then mixed to obtain a lithium lanthanum niobium oxide precursor.

[0034] As a further solution, the solvent in step S1 is selected from one or more of deionized water and ultrapure water.

[0035] As a further solution, the mixing time of the lithium lanthanum niobium oxide raw materials is 0.5h - 2h.

[0036] As a further solution, in step S1, the lithium-rich manganese-based cathode material is dispersed in deionized water.

[0037] As a further solution, the dispersion time of the lithium-rich manganese-based cathode material is 0.5h - 2h.

[0038] As a further solution, the mixing time of the lithium lanthanum niobium oxide raw materials, ammonium tetrathiomolybdate, and the lithium-rich manganese-based cathode material in step S1 is 0.5h - 2h.

[0039] As a further solution, the freeze-drying treatment time in step S2 is 5h to 7h, and the temperature is -15°C to -30°C.

[0040] As a further solution, in the step S2, the method for removing the solvent is sublimation removal, and the sublimation time is 36h - 48h.

[0041] As a further solution, in the step S2, the calcination temperature is 300°C - 330°C, and the calcination time is 4h - 6h; or the calcination temperature is 680°C - 720°C, and the calcination time is 2h - 3.5h.

[0042] As a further solution, the calcination in the step S2 is carried out in an inert atmosphere, and the inert atmosphere is selected from any one or more of argon, helium, neon, krypton, xenon, and radon.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] In the present invention, a double-layer coating layer of molybdenum disulfide and lithium lanthanum niobium oxide is constructed on the surface of the lithium-rich manganese-based cathode material by co-pyrolysis of ammonium tetrathiomolybdate with ammonium niobium oxalate, lanthanum source, and lithium source that constitute lithium lanthanum niobium oxide. By using the ammonia gas released during the high-temperature pyrolysis process of ammonium tetrathiomolybdate and ammonium niobium oxalate, a surface spinel layer and oxygen vacancies are synergistically constructed to form a mixed-phase surface layer rich in oxygen vacancies, thereby improving the Coulomb efficiency and cycle stability. The molybdenum disulfide generated after pyrolysis has a good matching effect with lithium lanthanum niobium oxide, which can fully protect the lithium-rich manganese-based cathode material from the erosion of the electrolyte and effectively improve the electrochemical performance of the lithium-rich manganese-based cathode material, thereby obtaining a cathode material with high cycle ability, good initial efficiency, and specific capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0046] In the drawings:

[0047] Figure 1 Among them, the left figure is the SEM image of Comparative Example 1, and the right figure is the SEM image of Example 1;

[0048] Figure 2 Among them, the left figure is the TEM image of Comparative Example 1, and the right figure is the TEM image of Example 1;

[0049] Figure 3 is the test result of the rate performance of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] For ease of understanding, the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide will be described more comprehensively below, and embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0051] The present invention provides a lithium-rich manganese-based cathode material (LRO-MLN) co-coated with molybdenum disulfide and lithium lanthanum niobium oxide. By combining freeze-drying and calcination techniques, molybdenum disulfide and lithium lanthanum niobium oxide are uniformly coated on the surface of the lithium-rich manganese-based cathode material. The double coating layer can not only serve as a stable protective layer to avoid the erosion of the cathode, but also form a stable coating structure by utilizing the physical and electrochemical compatibility between molybdenum and niobium, which are adjacent elements in the same period, to optimize the electrochemical performance and avoid the occurrence of 'deoxidation'.

[0052] On this basis, the present invention fully considers various parameters of LRO-MLN, analyzes in detail the influence of the freeze-drying combined with calcination technique on the formation of LRO-MLN, and expounds the influence of the double coating layer of molybdenum disulfide and lithium lanthanum niobium oxide on the performance of the lithium-rich manganese-based cathode material and their mutual interactions. By constructing a mutually cooperative double coating layer of molybdenum disulfide and lithium lanthanum niobium oxide, problems such as lattice stress accumulation and lattice oxygen precipitation when the lithium-rich manganese-based cathode material is used as the cathode of a lithium battery are solved. At the same time, the electron-conducting performance and ion-conducting performance of LRO-MLN are improved, and the first-cycle Coulomb efficiency, specific capacity, rate performance, and cycling performance of the battery are enhanced.

[0053] In the first aspect, the present invention provides a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide. The surface of the lithium-rich manganese-based cathode material has a co-coating layer containing molybdenum disulfide and lithium lanthanum niobium oxide. The general formula of the O2-type lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.5, 0 < y ≤ 0.3, 0 < z ≤ 0.3, 0.2 < q ≤ 0.7, 1 - y - z - q ≥ 0, and TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide lithium lanthanum niobium oxide is Li 4+f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or high-valent metal substituting for niobium, specifically including one or more of titanium, zirconium, tantalum, manganese, and molybdenum. The percentage of the 5C rate discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide to the 1C rate discharge capacity is greater than or equal to 65%, and the percentage of the 10C rate discharge capacity to the 1C rate discharge capacity is greater than or equal to 45%.

[0054] The coating layer on the lithium-rich manganese-based cathode material can not only fully protect the lithium-rich manganese-based cathode material from the erosion of the electrolyte, but also the interaction between the molybdenum disulfide and lithium lanthanum niobium oxide coating layers helps to further improve the electrochemical performance of the lithium-rich manganese-based cathode material. First, molybdenum and niobium are adjacent elements in the same period and have better compatibility; second, since molybdenum (Mo) ions have a high binding energy with oxygen (607 kJ mol -1 ), electrons will transfer from Mo to oxygen, thus playing an "oxygen anchor" role in stabilizing the surface oxygen. The doping of niobium (Nb) with a larger radius can effectively expand the lithium-ion transmission channel, form Nb-O bonds, and further inhibit the release of lattice oxygen, thereby improving the rate performance; finally, the layered molybdenum disulfide can provide a certain flexibility, while lithium lanthanum niobium oxide can provide a stable three-dimensional skeleton. The co-binding of molybdenum disulfide and lithium lanthanum niobium oxide can effectively reduce the mechanical stress generated during the insertion and extraction of lithium ions and avoid the generation of secondary particle cracks; generally speaking, the coating layer on the lithium-rich manganese-based cathode material can not only effectively protect the material from the erosion of the electrolyte, but also the synergistic effect of molybdenum disulfide and lithium lanthanum niobium oxide helps to significantly improve the electrochemical performance of the material.

[0055] As some exemplary preferred embodiments, in the lithium-rich manganese-based cathode material, it is Li 1+x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, and TM is a transition element, specifically including any one or several of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide lithium lanthanum niobium oxide is Li 4+ f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, and N represents a transition metal or a high-valent metal substituting niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum.

[0056] As some exemplary preferred embodiments, in the lithium-rich manganese-based cathode material, it is Li 1+x Ni y Co z Mn q TM 1-y-z-qO2, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the solid oxide is Li 4+f La i-a M a Nb j- b N b O 12 , where 0.5 ≤ f < 1.5, 2.8 ≤ i - a < 3.2, 1.9 ≤ j - b < 2.1, 0 ≤ a ≤ 0.4, 0 ≤ b ≤ 0.25, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum; the further optimization of the lithium-rich manganese-based cathode material and the general formula of the solid oxide helps to ensure that molybdenum disulfide and lithium lanthanum niobate in the co-coating layer further play their interaction, and further improve the electrochemical performance of the lithium-rich manganese-based cathode material with the co-coating layer.

[0057] As a further solution, the co-coating layer is constructed by the co-pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate, lanthanum source, and lithium source that constitute lithium lanthanum niobate. Among them, ammonium tetrathiomolybdate pyrolyzes at high temperature to obtain stable molybdenum disulfide. At the same time, the gas (NH3) released during the pyrolysis of ammonium tetrathiomolybdate can modify the surface structure of the lithium-rich manganese-based cathode material to obtain a mixed-phase surface layer rich in oxygen vacancies, which helps to improve the Coulomb efficiency and cycle stability; in addition, ammonium niobium oxalate also releases NH3 during pyrolysis. Through the NH3 released during the pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate, a surface spinel layer and oxygen vacancies can be constructed and used as the pins of the double coating layer to realize the construction of the co-coating layer. The constructed oxygen vacancies can effectively capture and stabilize surface oxygen atoms to promote the "oxygen anchor" effect, and at the same time help to form Nb-O bonds and inhibit the generation of lattice oxygen; under the double surface coating of ammonium tetrathiomolybdate and lithium lanthanum niobate, the cycle and rate performance of the lithium-rich manganese-based cathode material are effectively improved.

[0058] As a further solution, the percentage of the 5C rate discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobate to the 1C rate discharge capacity is greater than or equal to 66%, 67%, 68%, 69%.

[0059] As a further solution, the percentage of the 5C rate discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobate to the 1C rate discharge capacity is greater than or equal to 70%.

[0060] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 10C rate to the discharge capacity at 1C rate is greater than or equal to 46%, 47%, 48%, 49%.

[0061] As a further solution, the percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 10C rate to the discharge capacity at 1C rate is greater than or equal to 50%.

[0062] As a further solution, the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw material is 0.5-1.8 wt%.

[0063] As a further solution, the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw material is 0.8-1.5 wt%. When the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw material is 0.8-1.5 wt%, it helps to further optimize the cooperation effect of molybdenum disulfide and lithium lanthanum niobium oxide and improve the cycle performance of LRO-MLN.

[0064] As a further solution, the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.2-0.8 wt%.

[0065] As a further solution, the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.4-0.6 wt%. Lithium lanthanum niobium oxide can play a framework role in the coating layer of LRO-MLN. When the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.4-0.6 wt%, it helps to construct a more stable framework and avoid affecting the insertion and extraction of lithium ions, thereby improving the electrochemical performance and cycle performance of LRO-MLN.

[0066] As a further solution, the 5C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 165 mAh g -1 -180 mAh g -1 。

[0067] As a further solution, the 5C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 170 mAh g -1 -178 mAh g -1 。

[0068] As a further solution, the 10C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 115 mAh g -1 -125 mAh g -1 。

[0069] As a further solution, the reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 118 mAh g -1 -123 mAh g -1 .

[0070] As a further solution, the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is prepared by the following steps:

[0071] S1: Mix a lithium source, a lanthanum source, ammonium niobium oxalate, ammonium tetrathiomolybdate, and a lithium-rich manganese-based cathode material in a solvent to form a homogeneous solution;

[0072] S2: Freeze-dry the mixed solution for 4 h to 8 h, then remove the solvent and perform calcination to obtain LRO-MLN.

[0073] The combination of freeze-drying technology and calcination technology helps to construct a co-coated layer of molybdenum disulfide and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based material. The application of freeze-drying technology not only ensures the uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based material, but also enables ammonium tetrathiomolybdate and lithium lanthanum niobium oxide to overlap with each other to form voids, which not only avoids the problems of decreased electrochemical performance and mechanical performance caused by material accumulation and agglomeration, but also provides sufficient space for the orderly growth of spinel crystals during the subsequent calcination process. On the other hand, during the calcination process, ammonium tetrathiomolybdate is pyrolyzed to form molybdenum disulfide, and at the same time, lithium lanthanum niobium oxide is crystallized to obtain a strong layered structure with high conductivity co-coated with molybdenum disulfide and lithium lanthanum niobium oxide, reducing the surface oxygen activity and inhibiting the side reaction between the cathode and the electrolyte, thereby effectively improving the cycle performance and rate performance, etc. From Figure 2 It can be observed that through the combination of freeze-drying technology and calcination technology, a co-coated layer of molybdenum disulfide and lithium lanthanum niobium oxide is successfully formed on the surface of the lithium-rich manganese-based material, and the material maintains a good layered structure before and after modification. At the same time, the fringe spacing of 0.256 nm corresponds to the (3-11) crystal plane of the spinel phase, further proving the effectiveness of this solution in constructing the spinel structure.

[0074] As a further solution, the lithium source in step S1 is selected from any one or more of lithium carbonate, lithium nitrate, lithium hydroxide, and lithium oxide.

[0075] As a further solution, the lanthanum source in step S1 is selected from any one or more of lanthanum oxide, lanthanum nitrate, lanthanum carbonate, and lanthanum acetate.

[0076] As a further solution, the raw materials of lithium lanthanum niobium oxide in step S1 are respectively dissolved in a solvent and then mixed.

[0077] As a further solution, the solvent in step S1 is selected from one or more of deionized water and ultrapure water.

[0078] As a further solution, the mixing time of the lithium lanthanum niobium oxide raw material is 0.5 h - 2 h.

[0079] As a further solution, in step S1, the lithium-rich manganese-based cathode material is dispersed in deionized water.

[0080] As a further solution, the dispersion time of the lithium-rich manganese-based cathode material is 0.5 h - 2 h.

[0081] As a further solution, in step S1, the mixing time of the lithium lanthanum niobium oxide raw material, ammonium tetrathiomolybdate, and the lithium-rich manganese-based cathode material is 0.5 h - 2 h.

[0082] As a further solution, in step S1, the lithium-rich manganese-based cathode material is obtained by mixing a precursor lithium source and a carbonate precursor in a stoichiometric ratio of 1:1.35 - 1:1.45, followed by ball milling and calcination annealing.

[0083] As a further solution, the precursor lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium fluoride, lithium oxide, lithium chloride, lithium dihydrogen phosphate, lithium oxalate, lithium sulfate, lithium formate, and lithium iodide.

[0084] As a further solution, the carbonate precursor satisfies the general formula Ni g Co h Mn k CO3, 0.14 ≤ g ≤ 0.18, 0.14 ≤ h ≤ 0.18, 0.52 ≤ k ≤ 0.72.

[0085] As a further solution, the stoichiometric ratio of the precursor lithium source to the carbonate precursor is 1:1.35 - 1:1.45.

[0086] As a further solution, the ball milling speed is 200 - 400 r / min.

[0087] As a further solution, the calcination temperature in the preparation process of the lithium-rich manganese-based cathode material is selected from any one of low-temperature calcination (250°C - 350°C), medium-temperature calcination (500°C - 800°C), or high-temperature calcination (900°C - 1000°C).

[0088] As a further solution, the calcination temperature in the preparation process of the lithium-rich manganese-based cathode material is selected from any one of medium-temperature calcination (500°C - 800°C) or high-temperature calcination (900°C - 1000°C).

[0089] As a further solution, the calcination time in the preparation process of the lithium-rich manganese-based cathode material is 4 h - 6 h, and the calcination atmosphere is air.

[0090] As a further solution, in the step S2, the freeze-drying treatment time is 5h to 7h, and the temperature is -15°C to -30°C.

[0091] As a further solution, in the step S2, the method for removing the solvent is sublimation removal, and the sublimation time is 36h - 48h.

[0092] As a further solution, in the step S2, the calcination temperature is 300°C - 330°C, and the calcination time is 4h - 6h; or the calcination temperature is 680°C - 720°C, and the calcination time is 2h to 3.5h.

[0093] As a further solution, the calcination in the step S2 is carried out in an inert atmosphere, and the inert atmosphere is selected from any one or more of argon, helium, neon, krypton, xenon, and radon.

[0094] The chemical raw materials involved in the following examples and comparative examples are all prior arts and are obtained through commercial purchases. The experimental devices, testing devices, etc. involved in the following examples and comparative examples are all conventional devices in the art, without special requirements and limitations.

[0095] Example 1

[0096] Preparation of the original lithium-rich manganese-based cathode material

[0097] Lithium carbonate (Li2CO3) and carbonate precursor (Ni 0.16 Co 0.16 Mn 0.68 CO3) are ball-milled evenly in a ball-milling tank according to the stoichiometric ratio of 1∶1.41, and then the mixture is calcined in an air atmosphere at 700 °C for 5 h, and then annealed at 900 °C for 5 h. The heating rate of the annealing program is 5 °C min –1 . After cooling naturally to room temperature, the original lithium-rich manganese-based cathode material (Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2) is obtained.

[0098] Preparation of LRO-MLN

[0099] S1: According to the stoichiometric ratio, LiNO3, C4H4NNbO9·nH2O, and La(CH3COO)3 are dissolved in deionized water respectively, and then dropped into La(CH3COO)3 in the order of LiNO3 and C4H4NNbO9·nH2O to obtain a lithium-lanthanum-niobium-oxygen precursor (Li5La3Nb2O 12 precursor). (NH4)2MoS4 is added to the lithium-lanthanum-niobium-oxygen precursor, and after mixing evenly, Li dispersed in deionized water is added 1.2 Ni0.13 Co 0.13 Mn 0.54 Mix Co, Mn, and O2 evenly. Among them, the coating amount of lithium lanthanum niobium oxide precursor on LRO-MLN is 0.5 wt%, and ammonium tetrathiomolybdate accounts for 1 wt% of the total mass of LRO-MLN raw materials (LiNO3, C4H4NNbO9·nH2O, La(CH3COO)3, (NH4)2MoS4, and Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2).

[0100] S2: After putting the mixture solution into a freeze dryer and treating it at -20°C for 6 h and sublimating it for 40 h, calcine it in a muffle furnace under an argon atmosphere at 300°C for 5 h to obtain the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and Li5La3Nb2O 12 .

[0101] Example 2

[0102] The preparation method and steps are the same as those in Example 1, except that the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw materials is 0.8 wt%.

[0103] Example 3

[0104] The preparation method and steps are the same as those in Example 1, except that the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw materials is 1.5 wt%.

[0105] Example 4

[0106] The preparation method and steps are the same as those in Example 1, except that the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.3 wt%.

[0107] Example 5

[0108] The preparation method and steps are the same as those in Example 1, except that the coating amount of lithium lanthanum niobium oxide on LRO-MLN is 0.6 wt%.

[0109] Example 6

[0110] The preparation method and steps are the same as those in Example 1, except that Li5La3Nb2O 12 is replaced with Li 4.4 La 2.8 Nb 1.9 O 12 .

[0111] Example 7

[0112] The preparation method and steps are the same as those in Example 1, except that the freeze-drying treatment time is selected as 5 h.

[0113] Example 8

[0114] The preparation method and steps are the same as those in Example 1, except that the calcination temperature in step S3 is 700 °C and the calcination time is 3 h.

[0115] Comparative Example 1

[0116] The preparation method and steps are the same as those in Example 1, except that the originally prepared Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 is used as the cathode material.

[0117] Comparative Example 2

[0118] The preparation method and steps are the same as those in Example 1, except that Li5La3Nb2O 12 .

[0119] Comparative Example 3

[0120] The preparation method and steps are the same as those in Example 1, except that ammonium tetrathiomolybdate is not added.

[0121] Comparative Example 4

[0122] The preparation method and steps are the same as those in Example 1, except that molybdenum disulfide is used to replace ammonium tetrathiomolybdate.

[0123] Comparative Example 5

[0124] The preparation method and steps are the same as those in Example 1, except that Li7La3Zr2O 12 is used to replace Li5La3Nb2O 12 .

[0125] Comparative Example 6

[0126] The preparation method and steps are the same as those in Example 1, except that Li5La3Nb2O is coated by the sol-gel method 12 and molybdenum disulfide.

[0127] Comparative Example 7

[0128] The preparation method and steps are the same as those in Example 1, except that the mass ratio of ammonium tetrathiomolybdate in LRO-MLN is 2 wt%.

[0129] Comparative Example 8

[0130] The preparation method and steps are the same as those in Example 1, except that the coating amount of Li5La3Nb2O 12 on LRO-MLN is 1 wt%.

[0131] Comparative Example 9

[0132] The preparation method and steps are the same as those in Example 1, except that the lyophilization time is selected as 3 h.

[0133] The specific parameters of the examples and comparative examples are shown in Table 2.

[0134] Preparation of the battery:

[0135] The preparation steps of the positive electrode sheet are as follows:

[0136] The prepared LRO-MLN, conductive agent (Super P), and binder (PVDF∶NMP = 5%) were thoroughly mixed in a degassing machine for 10 min according to a mass ratio of 8:1:1; meanwhile, the coating speed of the flat coater was set to 50 mm s –1 , and the corresponding coating thickness of the blade was adjusted to 100 μm. Then the slurried paste was uniformly coated on the aluminum foil through the flat coater. After coating, the electrode sheet was placed in a blast drying oven at 80 °C for 1 h, and then transferred to a vacuum drying oven at 90 °C for 6 h. After cooling to room temperature, it was cut into circular electrode sheets with a diameter of 12 mm and weighed on an electronic analytical balance for subsequent use.

[0137] The assembly steps of the CR2032 button battery are as follows:

[0138] First, the weighed electrode sheet was placed in a glove box, and then the battery was assembled in the order of negative electrode case, electrode sheet, electrolyte (30 μL), separator (Celgard 2325), electrolyte (30 μL), lithium sheet (1 mm), gasket, spring sheet, and positive electrode case, and sealed with a sealer. After standing for about 5 h, it was tested and characterized.

[0139] The battery test conditions are shown in Table 1, and the test results are shown in Table 3.

[0140] Table 1

[0141]

[0142] Table 2

[0143]

[0144] Table 3

[0145]

[0146] In Table 3, it can be observed from Examples 1-8 and Comparative Examples 1-9 that Examples 1-8 exhibit better initial Coulombic efficiency and specific capacity than Comparative Examples 1-9, and also show much better cycling ability than Comparative Examples 1-9. This indicates that the co - coating of lithium - rich manganese - based cathode materials with molybdenum disulfide and lithium lanthanum niobium oxide can effectively optimize the electrochemical performance of the battery. While maintaining or even improving the initial Coulombic efficiency and specific capacitance of the lithium - rich manganese - based cathode material, it can inhibit oxygen loss and improve the battery cycling performance.

[0147] Figure 1 It can be observed that when the co - coating of lithium - rich manganese - based cathode materials with molybdenum disulfide and lithium lanthanum niobium oxide is not adopted, the surface of Comparative Example 1 is rougher, and Figure 2 It can be observed that the lattice fringe spacing of the bulk phase of Comparative Example 1 and Example 1 corresponds to the (003) crystal plane, indicating that the material maintains a good layered structure before and after modification. At the same time, the lattice fringe spacing of Example 1 increases from 0.480 nm to 0.486 nm, indicating that there may be Nb 5+ doping. There is a coating layer on the surface of Example 1, and the fringe spacing of 0.256 nm corresponds to the (3 - 11) crystal plane of the spinel phase. The spinel phase formed by the coating layer helps the material to still have a high discharge capacity under high - rate charge - discharge conditions, further proving that the co - action of the molybdenum disulfide and lithium lanthanum niobium oxide coating layers improves the stability and electrochemical performance of the lithium - rich manganese - based cathode material. From the data in Table 3, it can be seen that the capacity retention rate of Comparative Example 1 after 400 cycles is only 65.97%, far lower than that of Example 1 (80.71%). The 5C reversible capacity of Comparative Example 1 is only 144.8 mAh g -1 , and the 10C reversible capacity is only 78.2 mAh g -1 , while the corresponding 5C reversible capacity of Example 1 is 174.1 mAh g -1 , and the 10C reversible capacity is 120 mAh g -1 . At the same time, Figure 3 The specific capacities of Example 1 and Comparative Example 1 at different rates can be further compared. The results show that with the increase of the charge - discharge rate, the rate performance of Example 1 is significantly better than that of Comparative Example 1. Such results once again illustrate the significance of the co - coating of molybdenum disulfide and lithium lanthanum niobium oxide for improving the rate and cycling performance of lithium - rich manganese - based cathode materials.

[0148] In Example 1, Comparative Examples 2 and 3, it can be further observed that to maximize the cycling performance of the lithium-rich manganese-based cathode material, co-coating of molybdenum disulfide and lithium lanthanum niobium oxide is required. Whether lithium lanthanum niobium oxide is missing (Comparative Example 2) or molybdenum disulfide is missing (Comparative Example 3), the cycling performance of Comparative Examples 2 and 3 is much lower than that of Example 1. This may be because the synergistic effect between molybdenum disulfide and lithium lanthanum niobium oxide cannot be exerted in Comparative Examples 2 and 3 with only a single substance coated, so the cycling ability is lower than that of Example 1.

[0149] In this solution, after ammonium tetrathiomolybdate and lithium lanthanum niobium oxide were deposited on the lithium-rich manganese-based cathode material, LRO-MLN was obtained through calcination. In Comparative Example 4, molybdenum disulfide and lithium lanthanum niobium oxide were directly used to coat the lithium-rich manganese-based cathode material. It can be observed that compared with Example 1, the initial Coulombic efficiency and cycling performance in Comparative Example 4 did not show good effects as in Example 1. This may be because in this solution, co-deposition and co-pyrolysis of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide are required, and the NH3 released during the pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate is used to modify the surface structure of the lithium-rich manganese-based cathode material, so as to obtain a mixed-phase surface layer rich in oxygen vacancies, improve the Coulombic efficiency and cycling stability, and jointly construct a coating layer with ammonium niobium oxalate.

[0150] Example 1 and Comparative Example 5 further discussed the compounding effect of molybdenum disulfide and lithium lanthanum niobium oxide. It can be observed that when the niobium in lithium lanthanum niobium oxide was replaced by zirconium, the specific capacitance in Comparative Example 5 was significantly lower than that in Example 1. At the same time, the battery cycling ability also decreased significantly. This may be because compared with zirconium, molybdenum and niobium, which are adjacent elements in the same period, have higher compatibility. At the same time, the doping of niobium with a larger radius can effectively expand the lithium-ion transmission channel and form Nb-O bonds, further inhibiting the release of lattice oxygen on the basis of the "oxygen anchor" effect of Mo. In addition, when zirconium is used to replace niobium, ammonium niobium oxalate, which can cooperate with ammonium tetrathiomolybdate to release NH3, will be missing in Comparative Example 5, resulting in difficulty in constructing a surface spinel layer and oxygen vacancies in Comparative Example 5, and the cycling performance is affected. Therefore, the overall performance of Comparative Example 5 is lower than that of Example 1.

[0151] Furthermore, we discussed the influence of freeze-drying on the performance of LRO-MLN during the preparation process. From Example 1 and Comparative Example 6, it can be observed that when molybdenum disulfide and lithium lanthanum niobium oxide were coated by the sol-gel method, the overall performance of Comparative Example 6 was lower than that of Example 1. This may be because compared with Example 1, the molybdenum disulfide and lithium lanthanum niobium oxide coated in Comparative Example 6 prepared by the sol-gel method may not be uniform enough, resulting in the accumulation and agglomeration of molybdenum disulfide and lithium lanthanum niobium oxide, which affected the initial efficiency and specific capacity of Comparative Example 6. Therefore, it is necessary to adopt the freeze-drying method proposed in this solution to realize the deposition of molybdenum disulfide and lithium lanthanum niobium oxide, so as to provide guarantee for the subsequent calcination.

[0152] Examples 1, Comparative Examples 7 and 8 demonstrate the influence of the mass ratios of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide in LRO-MLN on battery performance. It can be observed from Comparative Example 7 that when the mass ratio of ammonium tetrathiomolybdate in LRO-MLN reaches 2 wt%, the cycling performance of Comparative Example 7 is significantly affected. This may be because molybdenum disulfide generated in Comparative Example 7 with a mass ratio of 2 wt% may not be able to act as a flexible layer to relieve the mechanical stress during lithium ion insertion and extraction, resulting in the generation of cracks in secondary particles. Therefore, the cycling performance of Comparative Example 7 is lower than that of Example 1. In LRO-MLN, the presence of lithium lanthanum niobium oxide also helps to provide a stable three-dimensional framework. However, when the mass ratio of lithium lanthanum niobium oxide in LRO-MLN exceeds 0.8 wt%, the hardness of the co-coated layer on the surface of the lithium-rich manganese-based cathode material may be relatively high, making it difficult to effectively relieve the mechanical stress during cycling, also resulting in the generation of cracks in secondary particles. Therefore, it is necessary to control the mass ratios of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide in LRO-MLN during the preparation process.

[0153] Examples 1 and Comparative Example 9 discuss the influence of freeze-drying conditions on the performance of LRO-MLN. When the freeze-drying treatment time is 3 h, the initial efficiency and cycling ability of Comparative Example 9 are obviously inferior to those of Example 1. This may be because the 3-h freeze-drying time is relatively short, which cannot ensure the uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based material, resulting in an uneven surface coating layer, and part of the surface is exposed to the electrolyte, thus generating irreversible side reactions during cycling and the surface coating layer cannot play an effective protective role.

[0154] In Examples 1-3, the influence of the addition amount of ammonium tetrathiomolybdate on the performance of LRO-MLN during the preparation of LRO-MLN is further explored. It can be observed that Example 1 exhibits higher cycling performance, initial Coulombic efficiency and specific capacity compared with Examples 2 and 3. This may be because when the mass ratio of ammonium tetrathiomolybdate in the LRO-MLN raw material is selected from 0.8 - 1.5 wt%, it helps to further exert the synergistic effect of molybdenum disulfide and lithium lanthanum niobium oxide, improving the cycling performance of LRO-MLN.

[0155] Examples 1, 4 and 5 demonstrate the influence of the mass ratio of lithium lanthanum niobium oxide in the LRO-MLN raw material on the performance of LRO-MLN. It can be observed that Example 1 shows better electrochemical performance than Examples 4 and 5. This may be because compared with Examples 4 and 5, the coating amount of lithium lanthanum niobium oxide in Example 1 can better relieve the stress generated during cycling, thus optimizing the performance of Example 1.

[0156] In Examples 1 and 6, the influence of the lithium lanthanum niobium oxygen ratio on the performance of LRO-MLN was discussed. It can be observed that Example 1 has better initial efficiency and cycling performance compared to Example 6. This may be because compared with Li 4.4 La 2.8 Nb 1.9 O 12 , in Example 1, the higher lithium content and more stable crystal structure can supplement the lost lithium ions during the cycling process and can better cooperate with molybdenum disulfide to optimize the electrochemical performance of Example 1. Therefore, Example 1 exhibits better cycling and electrochemical capabilities.

[0157] In Examples 1 and 7, the influence of the freeze-drying treatment time on the performance of LRO-MLN was demonstrated. It can be observed that Example 1 has better cycling ability compared to Example 7. This may be because a 6-hour freeze-drying treatment time can ensure more uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide, thereby optimizing the cycling performance of Example 1.

[0158] In Examples 1 and 8, the influence of the annealing time and temperature on the performance of LRO-MLN was demonstrated. Examples 1 and 8 exhibit equally excellent electrochemical capabilities and cycling performance. This may be because a 5-hour calcination time in Example 1 can ensure that ammonium niobium oxalate and ammonium tetrathiomolybdate are completely converted into molybdenum disulfide and lithium lanthanum niobium oxide during calcination, and at the same time construct a uniform molybdenum disulfide and lithium lanthanum niobium oxide co-coating layer. In Example 8, the calcination temperature was increased to 700 °C but the calcination time was shortened to 3 hours, which can also ensure the calcination effect.

[0159] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and deformations to the above embodiments within the scope of the present invention. In addition, without contradiction, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples.

Claims

1. A lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide, characterized in that, The surface of the lithium-rich manganese-based cathode material has a co-coating layer containing molybdenum disulfide and lithium lanthanum niobium oxide. The general formula of the lithium-rich manganese-based cathode material is Li 1+ x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.5, 0 < y ≤ 0.3, 0 < z ≤ 0.3, 0.2 < q ≤ 0.7, 1 - y - z - q ≥ 0, and TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of the lithium lanthanum niobium oxide is Li 4+f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, N represents a transition metal or a high-valence metal substituting for niobium, specifically including one or more of titanium, zirconium, tantalum, manganese, and molybdenum. The percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 5C rate to the discharge capacity at 1C rate is greater than or equal to 65%, and the percentage of the discharge capacity at 10C rate to the discharge capacity at 1C rate is greater than or equal to 45%.

2. The lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 1, characterized in that, The general formula of the lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of lithium lanthanum niobium oxide is Li 4+f La i-a M a Nb j-b N b O 12 , where 0 ≤ f < 2, 2.5 ≤ i - a < 3.5, 1.8 ≤ j - b < 2.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, and N represents a transition metal or a high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum.

3. The lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 1, characterized in that, The general formula of the lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn q TM 1-y-z-q O2, where 0 < x ≤ 0.4, 0.05 < y ≤ 0.17, 0.05 < z ≤ 0.17, 0.4 < q ≤ 0.65, 1 - y - z - q ≥ 0, and TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, and copper; the general formula of lithium lanthanum niobium oxide is Li 4+f La i-a M a Nb j-b N b O 12 , where 0.5 ≤ f < 1.5, 2.8 ≤ i - a < 3.2, 1.9 ≤ j - b < 2.1, 0 ≤ a ≤ 0.4, 0 ≤ b ≤ 0.25, M is a lanthanide or alkaline earth metal substituting for lanthanum, specifically including any one or more of yttrium, barium, strontium, europium, neodymium, and ytterbium, and N represents a transition metal or a high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum; The percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 5C rate to the discharge capacity at 1C rate is greater than or equal to 66%; The percentage of the discharge capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide at 10C rate to the discharge capacity at 1C rate is greater than or equal to 46%.

4. The lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 1, characterized in that, As one of the raw materials, ammonium tetrathiomolybdate accounts for 0.5-1.8 wt% in the raw materials of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide; The 5C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 165 mAh g -1 -180 mAh g -1 ; The 10C reversible capacity of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is 115 mAh g -1 -125 mAh g -1 .

5. A preparation method of a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide as described in claim 1, characterized in that, It includes the following steps: S1: Mix a lithium source, a lanthanum source, ammonium niobium oxalate, ammonium tetrathiomolybdate, and a lithium-rich manganese-based cathode material in a solvent to form a homogeneous solution; S2: Freeze-dry the mixed solution, then remove the solvent and conduct calcination. After calcination, a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide is obtained.

6. The preparation method of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 5, characterized in that, In the step S1, the lithium source is selected from any one or more of lithium carbonate, lithium nitrate, lithium hydroxide, and lithium oxide; In the step S1, the lanthanum source is selected from any one or more of lanthanum oxide, lanthanum nitrate, lanthanum carbonate, and lanthanum acetate; In the step S1, the lithium source, the lanthanum source, and ammonium niobium oxalate are respectively dissolved in a solvent and then mixed to obtain a lithium lanthanum niobium oxide precursor; In the step S1, the solvent is selected from one or more of deionized water and ultrapure water; The mixing time of the lithium source, the lanthanum source, and ammonium niobium oxalate after being dissolved in the solvent is 0.5 h - 2 h.

7. The preparation method of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 6, characterized in that, In the step S1, the lithium-rich manganese-based cathode material is dispersed in deionized water; The dispersion time of the lithium-rich manganese-based cathode material is 0.5 h - 2 h; In the step S1, the mixing time of the lithium lanthanum niobium oxide precursor, ammonium tetrathiomolybdate, and the lithium-rich manganese-based cathode material is 0.5 h - 2 h.

8. The preparation method of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 5, characterized in that, In the step S1, the preparation method of the lithium-rich manganese-based cathode material is: mixing a precursor lithium source and a carbonate precursor according to a stoichiometric ratio, ball-milling, and calcining and annealing to obtain; The precursor lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium fluoride, lithium oxide, lithium chloride, lithium dihydrogen phosphate, lithium oxalate, lithium sulfate, lithium formate, and lithium iodide; The carbonate precursor satisfies the general formula Ni g Co h Mn k CO3, 0.14 ≤ g ≤ 0.18, 0.14 ≤ h ≤ 0.18, 0.52 ≤ k ≤ 0.72; The stoichiometric ratio of the precursor lithium source to the carbonate precursor is 1:1.35 - 1:1.45; The ball-milling speed is 200 - 400 r / min; The calcination temperature in the preparation process of the lithium-rich manganese-based cathode material is selected from any one of low-temperature calcination at 250°C to 350°C, medium-temperature calcination at 500°C to 800°C, or high-temperature calcination at 900°C to 1000°C; The calcination time in the preparation process of the lithium-rich manganese-based cathode material is 4 h - 6 h, and the calcination atmosphere is air.

9. The preparation method of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 5, characterized in that In the step S2, the freeze-drying time is 4 h - 8 h, and the temperature is -15°C to -30°C; In the step S2, the freeze-drying treatment time is 5 h - 7 h; In the step S2, the method for removing the solvent is sublimation removal, and the sublimation time is 36 - 48 h; In the step S2, the calcination temperature is 300 - 330°C, and the calcination time is 4 h - 6 h; or the calcination temperature is 680 - 720°C, and the calcination time is 2 h - 3.5 h; The calcination in step S2 is carried out in an inert atmosphere, and the inert atmosphere is selected from any one or more of argon, helium, neon, krypton, xenon and radon; The sublimation time is 36 h to 48 h.

10. An energy storage device, having the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to any one of claims 1-4.

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