Molybdenum disulfide and lithium lanthanum niobium oxygen co-coated lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention discloses a molybdenum disulfide and lithium-lanthanum-niobium-oxygen co-coated lithium-rich manganese-based positive electrode material and a preparation method thereof, and realizes double uniform coating of molybdenum disulfide and lithium-lanthanum-niobium-oxygen on the surface of the lithium-rich manganese-based positive electrode material by combining freeze drying and calcining technologies. The double coating layer not only can be used as a stable protective layer to prevent the positive electrode material from being eroded, but also can form a stable coating structure by utilizing the physical and electrochemical compatibility between two adjacent elements of molybdenum and niobium in the same period, so that the electrochemical performance is optimized, the'deoxidation 'phenomenon is avoided, and the service life of the positive electrode material is prolonged. Under co-coating of the molybdenum disulfide and the lithium lanthanum niobium oxide, the lithium-rich manganese-based positive electrode material co-coated with the molybdenum disulfide and the lithium lanthanum niobium oxide is obtained, and the lithium-rich manganese-based positive electrode material co-coated with the molybdenum disulfide and the lithium lanthanum niobium oxide can guarantee the first effect and the specific capacity of the battery and can 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 relates 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 a high energy density of 400 Wh / kg and above, in addition to the continuous progress of the battery cell process, it also depends on the innovation of the core material system. Among them, lithium-rich manganese-based layered oxides have been widely used as cathode materials for batteries due to their extremely high specific capacity (>250 mAh / g), low cost, and environmental friendliness. -1 ), low cost, and environmental friendliness, etc., are widely used in battery cathode materials. -1

[0003] Lithium-rich manganese-based materials can generally be written as xLi 2 MnO 3 ·(1–x)LiTMO 2 . Because of its low cost (mainly manganese element with low cost and less precious metal content), high theoretical specific capacity (>250 mAh / g -1 ), high working voltage and high capacity, it has 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 structural 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 heteroelements or surface coating to modify it, the doping components are usually difficult to control and may have certain side effects on the capacity of the lithium-rich manganese-based cathode material; and too thick or uneven surface coating layer will affect the insertion and extraction process of lithium ions in the cathode, resulting in a decline in the rate performance of the modified material. 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, and constructs a double coating on the surface of the lithium-rich manganese-based cathode material by using molybdenum disulfide and lithium lanthanum niobium oxide. 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 "deoxidation" situation, 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-q O 2 , 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, magnesium, 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 O 2 , 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, magnesium, 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 Mnq TM 1-y-z-q O 2 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, magnesium, 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, and 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 to 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 to 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 to 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 to 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 proportion in the raw materials is 0.5 - 1.8 wt%.

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

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

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

[0016] As a further embodiment, 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 embodiment, 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 embodiment, 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 embodiment, 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 method for preparing a lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide. The preparation steps are as follows: S1: Mix a lithium source, a lanthanum source, ammonium oxalate niobate, ammonium tetrathiomolybdate, and a lithium-rich manganese-based cathode material in a solvent to form a homogeneous solution; S2: Freeze-dry the mixed solution for 4 h to 8 h, then remove the solvent and perform calcination to obtain a lithium-rich manganese-based cathode material LRO-MLN co-coated with molybdenum disulfide and lithium lanthanum niobium oxide.

[0021] As a further embodiment, the lithium source in step S1 is selected from any one or more of lithium carbonate, lithium nitrate, lithium hydroxide, and lithium oxide.

[0022] As a further embodiment, the lanthanum source in step S1 is selected from any one or more of lanthanum oxide, lanthanum nitrate, lanthanum carbonate, and lanthanum acetate.

[0023] As a further embodiment, the lithium-rich manganese-based cathode material in step S1 is obtained by mixing a precursor lithium source and a carbonate precursor (Ni 0.16 Co 0.16 Mn 0.68 CO 3 ) according to the stoichiometric ratio, mixing and ball-milling, and then performing calcination and annealing.

[0024] As a further embodiment, 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.

[0025] As a further embodiment, the carbonate precursor satisfies the general formula Ni g Co h Mn k CO 3 , 0.14 ≤ g ≤ 0.18, 0.14 ≤ h ≤ 0.18, 0.52 ≤ k ≤ 0.72.

[0026] As a further embodiment, the stoichiometric ratio of the precursor lithium source to the carbonate precursor is 1:1.35 - 1:1.45.

[0027] As a further embodiment, the mixed ball milling speed is 200 - 400 r / min.

[0028] As a further embodiment, 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).

[0029] As a further embodiment, 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).

[0030] As a further embodiment, the calcination time in the preparation process of the lithium-rich manganese-based cathode material is 4h - 6h, and the calcination atmosphere is air.

[0031] As a further embodiment, 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.

[0032] As a further embodiment, the solvent in step S1 is selected from one or more of deionized water and ultrapure water.

[0033] As a further embodiment, the mixing time of the lithium lanthanum niobium oxide raw materials is 0.5h - 2h.

[0034] As a further embodiment, in step S1, the lithium-rich manganese-based cathode material is dispersed in deionized water.

[0035] As a further embodiment, the dispersion time of the lithium-rich manganese-based cathode material is 0.5h - 2h.

[0036] As a further solution, in the 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.

[0037] As a further solution, in the step S2, the freeze-drying treatment time is 5 h - 7 h, and the temperature is -15°C - -30°C.

[0038] As a further solution, in the step S2, the method for removing the solvent is sublimation removal, and the sublimation time is 36 h - 48 h.

[0039] As a further solution, in the step S2, the calcination temperature is 300°C - 330°C, and the calcination time is 4 h - 6 h; or the calcination temperature is 680°C - 720°C, and the calcination time is 2 h - 3.5 h.

[0040] 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.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects: 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 the 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 coordination effect with lithium lanthanum niobium oxide, 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

[0042] 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 to the present invention.

[0043] In the drawings: Figure 1 in, the left figure is the SEM image of Comparative Example 1, and the right figure is the SEM image of Example 1; Figure 2 in, the left figure is the TEM image of Comparative Example 1, and the right figure is the TEM image of Example 1; Figure 3 is Example 1, and the rate performance test results of Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] For the convenience of understanding, a more comprehensive description of the lithium-rich manganese-based cathode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide will be given below, and embodiments of the present invention are provided, but the scope of the present invention is not limited thereby.

[0045] 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, double-layer uniform coating of molybdenum disulfide and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based cathode material is achieved. 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'.

[0046] On the above 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 elaborates on 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 and ion-conducting properties of LRO-MLN are improved, and the first-cycle Coulombic efficiency, specific capacity, rate performance, and cycling performance of the battery are enhanced.

[0047] In a 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 O 2 , 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 several of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, magnesium, 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 \(0\leq f \lt 2\), \(2.5\leq i - a \lt 3.5\), \(1.8\leq j - b \lt 2.2\), \(0\leq a \leq 1\), \(0\leq b \leq 0.5\), \(M\) 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-valent 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 niobate 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%.

[0048] The coating layer coated 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 niobate 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, due to the high binding energy (607 kJ mol -1 ) between molybdenum (Mo) ions and oxygen, electrons will transfer from Mo to oxygen, thus playing the role of "oxygen anchor" to stabilize the surface oxygen. The doping of niobium (Nb) with a larger radius can effectively expand the lithium ion transport channels, 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 niobate oxide can provide a stable three-dimensional framework. The co-binding of molybdenum disulfide and lithium lanthanum niobate 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 coated 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 niobate oxide helps to significantly improve the electrochemical performance of the material.

[0049] As some exemplary preferred embodiments, in the lithium-rich manganese-based cathode material is Li 1+x Ni y Co z Mn q TM 1-y-z-q O 2 , where \(0 \lt x \leq 0.4\), \(0.05 \lt y \leq 0.17\), \(0.05 \lt z \leq 0.17\), \(0.4 \lt q \leq 0.65\), \(1 - y - z - q \geq 0\), \(TM\) is a transition element, specifically including any one or several of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, magnesium, and copper; the general formula of the solid oxide lithium lanthanum niobate 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 high-valence metal substituting for niobium, specifically including any one or more of titanium, zirconium, tantalum, manganese, and molybdenum.

[0050] 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 O 2 , 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 several of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, magnesium, 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, and 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; 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 niobium oxide in the co-coating layer further exert their interaction, further improving the electrochemical performance of the lithium-rich manganese-based cathode material with the co-coating layer.

[0051] As a further solution, the co-coating layer is constructed by co-pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate, lanthanum source, and lithium source that constitute lithium lanthanum niobium oxide. Among them, ammonium tetrathiomolybdate pyrolyzes at high temperature to obtain stable molybdenum disulfide. At the same time, the gas (NH 3 ) 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 NH 3 , and through the NH 3 released during the pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate, a surface spinel layer and oxygen vacancies can be constructed, which serve as the pins of the double coating layer to achieve 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 niobium oxide, the cycling and rate performance of the lithium - rich manganese - based cathode material are effectively improved.

[0052] 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 to the discharge capacity at 1C rate is greater than or equal to 66%, 67%, 68%, 69%.

[0053] 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 to the discharge capacity at 1C rate is greater than or equal to 70%.

[0054] 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%.

[0055] 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%.

[0056] As a further solution, the mass ratio of ammonium tetrathiomolybdate in the LRO - MLN raw material is 0.5 - 1.8 wt%.

[0057] 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 cycling performance of LRO - MLN.

[0058] As a further solution, the coating amount of lithium lanthanum niobium oxide on LRO - MLN is 0.2 - 0.8 wt%.

[0059] 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 cycling performance of LRO - MLN.

[0060] 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 at 5C is 165 mAh g -1 -180 mAh g -1 。

[0061] 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 at 5C is 170 mAh g -1 -178 mAh g -1 。

[0062] 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 at 10C is 115 mAh g -1 -125 mAh g -1 。

[0063] 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 at 10C is 118 mAh g -1 -123 mAh g -1 。

[0064] 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: S1: Mix a lithium source, a lanthanum source, ammonium niobium oxalate, ammonium tetrathiomolybdate, and the lithium-rich manganese-based cathode material in a solvent to form a homogeneous solution; S2: Lyophilize the mixed solution for 4 h to 8 h, then remove the solvent and perform calcination to obtain LRO-MLN.

[0065] The combination of the lyophilization technique and the calcination technique 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 the lyophilization technique ensures the uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based material, while enabling 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 caking, 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 2It can be observed that by combining freeze-drying technology with calcination technology, a coating layer has been successfully formed on the surface of the lithium-rich manganese-based material with molybdenum disulfide and lithium lanthanum niobium oxide. Moreover, before and after modification, the material maintains a good layered structure. Meanwhile, the fringe spacing of 0.256 nm corresponds to the (3-11) crystal plane of the spinel phase, further demonstrating the effectiveness of this solution in constructing the spinel structure.

[0066] 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.

[0067] 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.

[0068] As a further solution, in step S1, the lithium lanthanum niobium oxide raw materials are respectively dissolved in a solvent and then mixed.

[0069] As a further solution, in step S1, the solvent is selected from one or more of deionized water and ultrapure water.

[0070] As a further solution, the mixing time of the lithium lanthanum niobium oxide raw materials is 0.5 h - 2 h.

[0071] As a further solution, in step S1, the lithium-rich manganese-based cathode material is dispersed in deionized water.

[0072] As a further solution, the dispersion time of the lithium-rich manganese-based cathode material is 0.5 h - 2 h.

[0073] As a further solution, in step S1, the mixing time of the lithium lanthanum niobium oxide raw materials, ammonium tetrathiomolybdate, and the lithium-rich manganese-based cathode material is 0.5 h - 2 h.

[0074] As a further solution, in step S1, the lithium-rich manganese-based cathode material is obtained by mixing the precursor lithium source with a carbonate precursor (Ni 0.16 Co 0.16 Mn 0.68 CO 3 ) in a stoichiometric ratio of 1:1.35 - 1:1.45, followed by ball milling and calcination annealing.

[0075] 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.

[0076] 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.

[0077] As a further solution, the stoichiometric ratio of the precursor lithium source to the carbonate precursor is 1:1.35 - 1:1.45.

[0078] As a further solution, the mixing ball milling speed is 200 - 400 r / min.

[0079] 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).

[0080] 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).

[0081] 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.

[0082] 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.

[0083] As a further solution, in step S2, the method for removing the solvent is sublimation removal, and the sublimation time is 36h - 48h.

[0084] As a further solution, in 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.

[0085] As a further solution, 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.

[0086] The chemical raw materials involved in the following examples and comparative examples are all prior art and are obtained through commercial purchase. 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.

[0087] Example 1 Preparation of the original lithium-rich manganese-based cathode material Lithium carbonate (Li 2 CO 3 ) and carbonate precursor (Ni0.16 Co 0.16 Mn 0.68 CO 3 (7) The mixture was ball-milled evenly in a ball-milling jar according to a stoichiometric ratio of 1:1.41, then 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 was 5 °C / min. –1 After natural cooling to room temperature, the original lithium-rich manganese-based cathode material (Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 ) was obtained.

[0088] Preparation of LRO-MLN S1: LiNO 3 , C 4 H 4 NNbO 9 ·nH 2 O and La(CH 3 COO) 3 were dissolved separately in deionized water. Then, according to the order of LiNO 3 , C 4 H 4 NNbO 9 ·nH 2 O, they were added dropwise to La(CH 3 COO) 3 in sequence to obtain a lithium lanthanum niobium oxide precursor (Li 5 La 3 Nb 2 O 12 precursor). (NH 4 ) 2 MoS 4 was added to the lithium lanthanum niobium oxide precursor. After mixing evenly, Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 dispersed in deionized water was added and stirred evenly. Among them, the coating amount of the lithium lanthanum niobium oxide precursor on LRO-MLN was 0.5 wt%, and ammonium tetrathiomolybdate accounted for the LRO-MLN raw materials (LiNO 3 , C 4 H 4 NNbO 9 ·nH 2 O, La(CH 3 COO) 3 , (NH 4 ) 2 MoS 4and Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 1 wt% of the total mass.

[0089] S2: The mixture solution is placed in a freeze dryer and treated at -20 °C for 6 h and sublimated for 40 h, and then calcined in a muffle furnace with an argon atmosphere at 300 °C for 5 h to obtain the molybdenum disulfide and Li 5 La 3 Nb 2 O 12 co-coated lithium-rich manganese-based cathode material.

[0090] Example 2 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 material is 0.8 wt%.

[0091] Example 3 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 material is 1.5 wt%.

[0092] Example 4 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%.

[0093] Example 5 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%.

[0094] Example 6 The preparation method and steps are the same as those in Example 1, except that Li 5 La 3 Nb 2 O 12 is replaced by Li 4.4 La 2.8 Nb 1.9 O 12 .

[0095] Example 7 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.

[0096] Example 8 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.

[0097] Comparative Example 1 The preparation method and steps are the same as those in Example 1, except that the originally prepared Li1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 as the cathode material.

[0098] Comparative Example 2 The preparation method and steps are the same as those in Example 1, except that Li 5 La 3 Nb 2 O 12 .

[0099] Comparative Example 3 The preparation method and steps are the same as those in Example 1, except that ammonium tetrathiomolybdate is not added.

[0100] Comparative Example 4 The preparation method and steps are the same as those in Example 1, except that molybdenum disulfide is used to replace ammonium tetrathiomolybdate.

[0101] Comparative Example 5 The preparation method and steps are the same as those in Example 1, except that Li 7 La 3 Zr 2 O 12 is used to replace Li 5 La 3 Nb 2 O 12 .

[0102] Comparative Example 6 The preparation method and steps are the same as those in Example 1, except that the sol-gel method is used to coat Li 5 La 3 Nb 2 O 12 and molybdenum disulfide.

[0103] Comparative Example 7 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%.

[0104] Comparative Example 8 The preparation method and steps are the same as those in Example 1, except that the coating amount of Li 5 La 3 Nb 2 O 12 on LRO-MLN is 1 wt%.

[0105] Comparative Example 9 The preparation method and steps are the same as those in Example 1, except that the freeze-drying time is selected as 3 h.

[0106] The specific parameters of the examples and comparative examples are shown in Table 2.

[0107] Preparation of the battery: The preparation steps of the positive electrode sheet are as follows: The prepared LRO-MLN, conductive agent (Super P), and binder (PVDF∶NMP = 5%) were fully 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 doctor blade was adjusted to 100 μm. Then the slurried paste was evenly coated on the aluminum foil through the flat coater. After coating, the electrode sheet was placed in a forced-air 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.

[0108] The assembly steps of the CR2032 button battery are as follows: First, the weighed electrode sheet was put into a glove box, and then the battery was assembled in the order of the 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. The battery was sealed using a sealer and left to stand for about 5 h before being tested and characterized.

[0109] The battery test conditions are shown in Table 1, and the test results are shown in Table 3.

[0110] Table 1

[0111] Table 2

[0112] Table 3

[0113] In Table 3, it can be observed from Examples 1-8 and Comparative Examples 1-9 that Examples 1-8 exhibited better first-week Coulombic efficiency and specific capacity than Comparative Examples 1-9, and also showed far better cycling ability than Comparative Examples 1-9. This indicates that the use of molybdenum disulfide and lithium lanthanum niobium oxide co-coated lithium-rich manganese-based cathode materials can effectively optimize the electrochemical performance of the battery, inhibit oxygen loss while maintaining or even improving the first Coulombic efficiency and specific capacitance of the lithium-rich manganese-based cathode material, and enhance the cycling performance of the battery.

[0114] Figure 1 It can be observed that when the molybdenum disulfide and lithium lanthanum niobium oxide co-coated lithium-rich manganese-based cathode material is not used, the surface of Comparative Example 1 is rougher, and from Figure 2It can be observed that the lattice fringe spacings of the bulk phases of Comparative Example 1 and Example 1 correspond 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 and discharge conditions, further proving that the molybdenum disulfide and lithium lanthanum niobium oxide coating layer enhance the stability and electrochemical performance of the lithium-rich manganese-based cathode material through mutual synergistic effects. 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 and discharge rate, the rate performance of Example 1 is significantly better than that of Comparative Example 1. Such results once again illustrate that the co-coating of molybdenum disulfide and lithium lanthanum niobium oxide is of great significance for improving the rate and cycle performance of the lithium-rich manganese-based cathode material.

[0115] In Example 1, Comparative Examples 2 and 3, it can be further observed that to maximize the cycle performance of the lithium-rich manganese-based cathode material, the co-coating of molybdenum disulfide and lithium lanthanum niobium oxide is required. Whether lacking lithium lanthanum niobium oxide (Comparative Example 2) or lacking molybdenum disulfide (Comparative Example 3), Comparative Examples 2 and 3 both show far lower cycle performance than 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 cycle ability is lower than that of Example 1.

[0116] In this scheme, after ammonium tetrathiomolybdate and lithium lanthanum niobium oxide are deposited on the lithium-rich manganese-based cathode material and then calcined, LRO-MLN is obtained. In Comparative Example 4, molybdenum disulfide and lithium lanthanum niobium oxide are directly used to coat the lithium-rich manganese-based cathode material. It can be observed that compared with Example 1, the initial Coulomb efficiency and cycle performance in Comparative Example 4 do not show good effects as in Example 1. This may be because in this scheme, it is necessary to co-deposit and co-pyrolyze ammonium tetrathiomolybdate and lithium lanthanum niobium oxide, and use the NH released during the pyrolysis of ammonium tetrathiomolybdate and ammonium niobium oxalate 3Modify the surface structure of the lithium-rich manganese-based cathode material to obtain a mixed-phase surface layer rich in oxygen vacancies, improve the Coulomb efficiency and cycle stability, and jointly construct a coating layer with ammonium niobium oxalate.

[0117] Examples 1 and Comparative Example 5 further discuss the compounding effect of molybdenum disulfide and lithium lanthanum niobium oxide. It can be observed that when niobium in lithium lanthanum niobium oxide is replaced by zirconium, the specific capacitance in Comparative Example 5 is significantly lower than that in Example 1. At the same time, the battery cycling ability also decreases significantly. This may be because, compared with zirconium, molybdenum and niobium, as adjacent elements in the same period, have higher compatibility. At the same time, niobium doping with a larger radius can effectively expand the lithium-ion transport channels, form Nb-O bonds, and further inhibit 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 that can cooperate with ammonium tetrathiomolybdate to release NH 3 will be lacking in Comparative Example 5, resulting in difficulty in constructing a surface spinel layer and oxygen vacancies in Comparative Example 5, and affecting the cycling performance. Therefore, the overall performance of Comparative Example 5 is lower than that of Example 1.

[0118] 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 are coated by the sol-gel method, the overall performance of Comparative Example 6 is 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, affecting the initial efficiency and specific capacitance of Comparative Example 6. Therefore, it is necessary to use the freeze-drying method proposed in this scheme to achieve the deposition of molybdenum disulfide and lithium lanthanum niobium oxide to ensure the subsequent calcination.

[0119] Examples 1, Comparative Examples 7 and 8 show the influence of the mass ratio of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide in LRO-MLN on the 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 the 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 of 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 skeleton. However, when the mass ratio of lithium lanthanum niobium oxide in LRO-MLN exceeds 0.8 wt%, the hardness of the co-coating 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 ratio of ammonium tetrathiomolybdate and lithium lanthanum niobium oxide in LRO-MLN during the preparation process.

[0120] In Example 1 and Comparative Example 9, the influence of freeze-drying conditions on the performance of LRO-MLN was discussed. When the freeze-drying treatment time was 3 h, the first efficiency and cycling ability of Comparative Example 9 were obviously inferior to those of Example 1. This may be because the 3-h freeze-drying time was relatively short, which could not ensure the uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobate oxide on the surface of the lithium-rich manganese-based material, resulting in an uneven surface coating layer. Part of the surface was exposed to the electrolyte, leading to irreversible side reactions during cycling, and the surface coating layer could not play an effective protective role.

[0121] In Examples 1-3, the influence of the addition amount of ammonium tetrathiomolybdate on the performance of LRO-MLN was further explored during the preparation of LRO-MLN. It can be observed that Example 1 showed higher cycling performance, first-cycle 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 was selected from 0.8-1.5 wt%, it was helpful to further exert the synergistic effect of molybdenum disulfide and lithium lanthanum niobate oxide, improving the cycling performance of LRO-MLN.

[0122] Examples 1, 4, and 5 demonstrated the influence of the mass ratio of lithium lanthanum niobate oxide in the LRO-MLN raw material on the performance of LRO-MLN. It can be observed that Example 1 exhibited better electrochemical performance than Examples 4 and 5. This may be because compared with Examples 4 and 5, the coating amount of lithium lanthanum niobate oxide in Example 1 could better relieve the stress generated during cycling, thus optimizing the performance of Example 1.

[0123] Examples 1 and 6 discussed the influence of the lithium lanthanum niobate oxide ratio on the performance of LRO-MLN. It can be observed that Example 1 had better first efficiency and cycling performance compared with Example 6. This may be because compared with Li 4.4 La 2.8 Nb 1.9 O 12 , the higher lithium content and more stable crystal structure in Example 1 could supplement the lost lithium ions during cycling and could cooperate with molybdenum disulfide to better optimize the electrochemical performance of Example 1. Therefore, Example 1 exhibited better cycling and electrochemical performance.

[0124] Examples 1 and 7 demonstrated the influence of the freeze-drying treatment time on the performance of LRO-MLN. It can be observed that Example 1 had better cycling ability compared with Example 7. This may be because the 6-h freeze-drying treatment time could ensure the more uniform deposition of ammonium tetrathiomolybdate and lithium lanthanum niobate oxide, thus optimizing the cycling performance of Example 1.

[0125] Examples 1 and 8 show the effects of annealing time and temperature on the performance of LRO-MLN. Examples 1 and 8 exhibit equally excellent electrochemical capabilities and cycling performance, which may be because the 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, while constructing a uniform co-coating layer of molybdenum disulfide and lithium lanthanum niobium oxide. In Example 8, the calcination temperature is increased to 700 °C but the calcination time is shortened to 3 hours, which can also ensure the calcination effect.

[0126] 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 as 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 mutual 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 positive electrode 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. TM is a transition element, specifically including any one or more of nickel, cobalt, manganese, iron, titanium, chromium, vanadium, molybdenum, magnesium, 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 positive electrode 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, magnesium, 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 positive electrode 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, magnesium, 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 5C rate discharge capacity of the lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide to the 1C rate discharge capacity is greater than or equal to 66%; The percentage of the 10C rate discharge capacity of the lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide to the 1C rate discharge capacity is greater than or equal to 46%.

4. The lithium-rich manganese-based positive electrode 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 0.5-1.8wt% of the raw materials of lithium-rich manganese-based positive electrode materials co-coated with molybdenum disulfide and lithium lanthanum niobium oxide; The lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide has a 5C reversible capacity of 165 mAh g -1 -180mAh g -1 ; The lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide has a 10C reversible capacity of 115 mAh g -1 -125mAh g -1 .

5. A method for preparing the lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 1, characterized in that: The steps include: S1: mixing a lithium source, a lanthanum source, ammonium niobium oxalate, ammonium tetrathiomolybdate, and a lithium-rich manganese-based positive electrode material in a solvent to form a uniform solution; S2: freeze-drying the mixed solution, then removing the solvent and calcining, to obtain a lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide.

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

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

8. The method for preparing a lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide according to claim 5, characterized in that: In step S1, the method for preparing the lithium-rich manganese-based positive electrode material is: a precursor lithium source and a carbonate precursor (Ni 0.16 Co 0.16 Mn 0.68 CO3) according to the stoichiometric ratio, ball milled and calcined; 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 mixing ball milling speed is 200-400 r / min; The calcination temperature in the preparation process of the lithium-rich manganese-based positive electrode 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 of the lithium-rich manganese-based positive electrode material preparation process is 4h~6h, and the calcination atmosphere is air.

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

10. An energy storage device comprising the lithium-rich manganese-based positive electrode material co-coated with molybdenum disulfide and lithium lanthanum niobium oxide as claimed in any one of claims 1 to 4.

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