Lithium-rich manganese oxide positive electrode material, preparation method therefor, and use thereof, and positive electrode sheet and use thereof

Abstract

Disclosed are a lithium-rich manganese oxide positive electrode material, a preparation method therefor, and a use thereof, and a positive electrode sheet and a use thereof. The chemical composition of the positive electrode material is xLi[Li1 / 3(Mn1-aMa)2 / 3]O2·(1-x)LiMn1-bM'bO2; an XRD pattern of the positive electrode material has a diffraction peak P(1) in a range that a diffraction angle 2θ1 is that: [43.5(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°; and the XRD pattern of the positive electrode material has a diffraction peak P(2) in a range that a diffraction angle 2θ2 is that: [17.7(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°, wherein 0.35≤x≤0.63. The positive electrode material has high initial efficiency, high discharge capacity, high energy efficiency, high rate performance, and high cycle performance.

Description

Lithium-rich manganese oxide positive electrode material and preparation method and application thereof, positive electrode sheet and application thereof Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a lithium-rich manganese oxide positive electrode material and a preparation method and application thereof, a positive electrode sheet and application thereof. Background Art

[0002] In recent years, new energy vehicles, as a national strategic emerging industry to cope with environmental pollution and energy crisis, have shown a good situation of vigorous development. Lithium-ion batteries, as a new energy carrier with excellent comprehensive performance, are widely used in electric vehicles, energy storage power stations, communications and digital electronic products and other markets.

[0003] In lithium-ion batteries, the positive electrode is the core key material of lithium-ion batteries and directly determines the technical performance level of the battery. Among the traditional lithium-ion positive electrode materials, LiCoO2 is expensive and is mainly used in 3C digital electronic products; multi-element LiNi 1-x-y Co x Mn y O2 and LiNi 1-x-y Co x Al y O2 has significantly improved cycle performance due to the synergistic effect between elements and is widely used in new energy power batteries, but its energy density can no longer meet people's demand for long-range driving. LiFePO4 has the advantages of low price, high safety performance and long cycle life, and is mainly used in power batteries and energy storage fields, but its specific capacity is low and close to the theoretical value, making it difficult to achieve a breakthrough. LiMn2O4 is cheap, but is prone to manganese dissolution and Jahn-Teller effect, resulting in poor high-temperature cycle performance. It is mainly used in two-wheeled vehicles and power tools. Layered lithium-rich manganese-based materials (LMR) are expected to become the cathode materials for the next generation of lithium-ion batteries due to their high specific capacity and low cost. However, the severe voltage decay during cycling, poor rate performance, low density, and unstable electrolyte at high voltage have seriously hindered their commercialization.

[0004] Therefore, developing new LMR materials with special microstructures and enhancing the solid solution effect of the two phases of LMR materials are of great significance for achieving long cycle life, high specific capacity, and high rate performance of batteries.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of low first coulombic efficiency, low discharge capacity, low energy efficiency, poor rate performance, and poor cycle performance of lithium-rich manganese oxide positive electrode materials in the prior art, and to provide a lithium-rich manganese oxide positive electrode material and its preparation method and application, a positive electrode sheet and its application. The lithium-rich manganese metal oxide positive electrode material has high first efficiency, high discharge capacity, high energy efficiency, high rate performance and high cycle performance.

[0007] In order to achieve the above object, the first aspect of the present invention provides a lithium-rich manganese oxide positive electrode material, wherein the chemical composition of the positive electrode material is: xLi[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2·(1-x)LiMn 1-b M′ b O2;

[0008] The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ1 of [43.5(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°. (1) ;

[0009] The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ2 of [17.7(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°. (2) ;

[0010] Wherein, x satisfies: 0.35≤x≤0.63.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned lithium-rich manganese oxide positive electrode material, wherein a precursor containing manganese and M1, a lithium source, and an additive optionally containing element M2 are uniformly mixed, and the mixed material is subjected to a two-stage temperature-raising sintering to obtain the lithium-rich manganese oxide positive electrode material;

[0012] The amount of the lithium source, the amount of the precursor, and the amount of the additive containing the element M2 are such that n(Li) / [n(Mn)+n(M1)+n(M2)] is 1.28-1.5;

[0013] The two-stage temperature rise sintering includes the following steps: heating from room temperature to a first sintering temperature at a first heating rate, performing a first sintering, and then heating to a second sintering temperature at a second heating rate, performing a second sintering; wherein the first heating rate is greater than or equal to the second heating rate.

[0014] A third aspect of the present invention provides a positive electrode sheet, wherein the positive electrode sheet includes a positive electrode active material, wherein the positive electrode active material includes a lithium-rich manganese oxide positive electrode material, a conductive agent, and a binder; wherein the content of the lithium-rich manganese oxide positive electrode material is not less than 90 wt % based on the total weight of the positive electrode active material;

[0015] Wherein, the lithium-rich manganese oxide positive electrode material is the above-mentioned lithium-rich manganese oxide positive electrode material.

[0016] A fourth aspect of the present invention provides a use of the above-mentioned lithium-rich manganese oxide positive electrode material or the above-mentioned positive electrode sheet in a lithium-ion battery.

[0017] Through the above technical solution, the lithium-rich manganese oxide positive electrode material and its preparation method and application, positive electrode sheet and its application provided by the present invention achieve the following beneficial effects:

[0018] (1) The lithium-rich manganese oxide positive electrode material provided by the present invention is composed of monoclinic Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b The two-phase structure of O2 is solid-solution composite, and the two-phase structure has a specific content ratio. In addition, the positive electrode material has a specific microstructure, which makes the positive electrode material have high first efficiency, high discharge capacity, high energy efficiency, high rate performance and high cycle performance.

[0019] (2) The lithium-rich manganese oxide positive electrode material provided by the present invention uses specific elements to achieve localized lattice substitution in the two phases, which can modulate the electronic structure of the two-phase microstructure of the material, form vacancy defects and enhance the bond energy of the metal-oxygen bond, which helps to improve electron and ion transport, inhibit the release of oxygen under high voltage, and further improve the structural reversible stability of the positive electrode material during the electrochemical cycle, thereby improving the discharge specific capacity, energy efficiency, rate performance and cycle performance of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is an XRD spectrum of the positive electrode material S-1 of Example 1;

[0021] FIG2 is an XRD spectrum of the positive electrode material S-2 of Example 2;

[0022] FIG3 is an XRD spectrum of the positive electrode material S-3 of Example 3;

[0023] FIG4 is an XRD spectrum of the positive electrode material S-4 of Example 4;

[0024] FIG5 is an XRD spectrum of the positive electrode material D-2 of Comparative Example 2;

[0025] FIG6 is a SEM image of the positive electrode material S-5 of Example 5;

[0026] FIG7 is a graph showing the first charge and discharge curves of a lithium-ion battery assembled from positive electrode material S-1, positive electrode material S-4, and positive electrode material D-2;

[0027] FIG8 is a graph showing the first charge and discharge curves of a lithium-ion battery assembled from positive electrode material S-1, positive electrode material S-5, and positive electrode material S-6;

[0028] FIG9 is a graph showing the first charge and discharge curves of a lithium-ion battery assembled from positive electrode material S-5 and positive electrode material D-3;

[0029] FIG10 is a voltage cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material S-5;

[0030] FIG11 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material S-5;

[0031] FIG12 is a voltage cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material D-2;

[0032] FIG13 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material D-2;

[0033] FIG14 is a voltage cycle diagram of a lithium-ion battery assembled from positive electrode material S-5 and positive electrode material D-3;

[0034] FIG15 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-5 and positive electrode material D-3. DETAILED DESCRIPTION

[0035] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0036] The first aspect of the present invention provides a lithium-rich manganese oxide positive electrode material, characterized in that the chemical formula of the lithium-rich manganese oxide positive electrode material is: xLi[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2·(1-x)LiMn 1-b M′ b O2;

[0037] The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ1 of [43.5(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°. (1) ;

[0038] The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ2 of [17.7(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°. (2) .

[0039] Wherein, x satisfies: 0.35≤x≤0.63.

[0040] In the present invention, the lithium-rich manganese oxide positive electrode material is composed of monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b The two-phase structure of O2 is solid-solution composite, and the two-phase structure has a specific content ratio. In addition, the positive electrode material has a specific microstructure, which makes the positive electrode material have high first efficiency, high discharge capacity, high energy efficiency, good rate performance and excellent cycle performance.

[0041] Specifically, in the present invention, the diffraction peak P in the XRD spectrum of the positive electrode material (1) And the diffraction peak P (2) When the position of satisfies the above conditions, it indicates that the monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b The content ratio of the two O2 phases is appropriate, the solid solution effect is good, and the structure is stable, which makes the material have high initial efficiency, high discharge capacity, high energy efficiency, good rate performance and excellent cycle performance.

[0042] In the present invention, the monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b The content ratio (x) of the two O2 phases was determined based on the XRD and ICP element measurement results and then by quantitative calculation.

[0043] Further, [43.6(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°.

[0044] Further, [17.8(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°.

[0045] Further, 0.4≤x≤0.55.

[0046] According to the present invention, 0≤a≤0.1, 0.15≤b≤0.85, M is selected from at least one element of Nb, Ru, Mo, Co, Ti and Zr; M′ is selected from at least one element of Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, Na, La, Os, Pr, Re, Ru, Sr, Sm, Ta and B.

[0047] In the present invention, for the content ratio (x), a and b specific values ​​in the chemical formula composition of the lithium-rich manganese oxide positive electrode material, the two-phase ratio (x) is determined according to the ratio of Li in the positive electrode material to the other transition metal elements in the positive electrode material except Li in the preparation method; if the doping elements M1 and M2 can be doped into both phases at the same time, the doping amount is distributed according to the ratio of the two phases; if they can only enter one phase, all of them are doped into the phase; specifically within each phase, the doping elements are replaced by the transition metal main elements according to the ratio of the other transition metal main elements except Li in the phase, and the specific values ​​of a and b in each phase are determined.

[0048] In the present invention, the positive electrode material is composed of monoclinic Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b The two-phase structure of O2 is formed by solid solution composite. The inventors have found that by directional element lattice substitution, M elements (such as Nb, Ru, Mo, Co, Ti or Zr, etc.) are used to replace Li [Li 1 / 3 Mn 2 / 3 ]Mn position in O2, to obtain Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2; replace the Mn position in LiMnO2 with M' elements (such as Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, Na, La, Os, Pr, Re, Ru, Sr, Sm or Ta, etc.) to obtain LiMn 1-b M′ b O2 components, Li[Li1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and LiMn 1-b M′ b The O2 two-phase components form a uniform and stable solid solution composite structure with a specific content ratio, which is the lithium-rich manganese oxide positive electrode material provided by the present invention.

[0049] In the present invention, the inventors have found that the lithium-rich manganese oxide positive electrode material provided by the present invention can effectively stabilize the crystal structure of the positive electrode material, improve the material microstructure, and achieve the improvement of the electrochemical performance of the material due to the presence of directional element lattice substitution. 1 / 3 Mn 2 / 3 ] Partial substitution of Mn in O2 can form Nb-O bonds, Ru-O bonds and Mo-O bonds with stronger bond energy, thus stabilizing the O 2- The oxidation reaction of anions inhibits the generation and precipitation of oxygen, and performs charge compensation during the discharge process to avoid excessive Mn 3+ The cycle performance deteriorates due to the generation of 1 / 3 Mn 2 / 3 ] Partial substitution of Mn sites in O2 can inhibit the migration of manganese ions and enhance the conductivity of the material, thereby improving the cycle performance and rate performance of the material. 1-b M′ b The introduction of M' elements (Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, La, Os, Pr, Re, Ru, Sr, Sm, Ta and B, etc.) in O2 can modulate the local electronic structure, stabilize the crystal structure of the material, and improve the initial efficiency, discharge capacity, rate performance and cycle life of the material. Doping with elements such as Ti, Zr, Nb, La, W, Co, and B will form lithium-containing compounds (such as LiNbO3 or Li2ZrO3 or Li4Ti5O 12 or Li3BO3 or LaNiO3, etc.), stabilize the surface structure of the positive electrode material particles or the interface strength between the particles or the grain boundary structure between the primary grains, improve the cycle life of the lithium ion battery containing the positive electrode material, and accelerate the transmission of lithium ions between the particles and between the interfaces, thereby improving the rate performance and cycle performance of the lithium ion battery containing the positive electrode material.

[0050] According to the present invention, the XRD spectrum of the positive electrode material has a diffraction peak P in the diffraction angle range of 2θ1. (1) The half-peak width meets the following requirements: 0.35≤FWHM (1) ≤0.50.

[0051] In the present invention, when the diffraction peak P exists within the range of diffraction angle 2θ1 (1) When the half-peak width falls within the above range, it indicates that the material has appropriate crystallinity and orderly atomic arrangement, thus achieving higher capacity, better rate performance, and better cycle performance. If the half-peak width is too large, the crystal structure is poor, the atomic arrangement is poorly ordered, and the electrochemical performance of the material will deteriorate significantly. If the half-peak width is too small, the material is too crystallinity, the primary particle size increases, the impedance increases, and ion diffusion becomes difficult, resulting in poor capacity, rate performance, and cycle performance.

[0052] Furthermore, the XRD spectrum of the positive electrode material has a diffraction peak P in the diffraction angle range of 2θ1. (1) The half-peak width satisfies: 0.38≤FWHM (1) ≤0.45.

[0053] According to the present invention, the XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the diffraction angle range of 2θ2. (2) FWHM (2) Satisfies: 0.17 ≤ FWHM (2) ≤0.28.

[0054] Furthermore, the XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the diffraction angle range of 2θ2. (2) FWHM (2) Satisfies: 0.18 ≤ FWHM (2) ≤0.24.

[0055] According to the present invention, the XRD spectrum of the positive electrode material has a diffraction peak P in the diffraction angle range of 2θ2. (2) The peak area S (2) The diffraction peak P exists in the diffraction angle range of 2θ1 (1) Peak area S (1) The following conditions are met:

[0056] 1.1≤S (2) / S (1) ≤1.8.

[0057] In the present invention, when the diffraction peak P (2) Peak area S (2) With diffraction peak P (1) Peak area S (1) When the ratio satisfies the above range, the material has better two-phase solid solubility and two-phase content ratio, and at the same time has better crystallinity, thus showing good electrochemical properties.

[0058] Furthermore, 1.2≤S (2) / S(1) ≤1.7.

[0059] In the present invention, the half-maximum width (FWHM) and peak area (S) of the diffraction peak are measured by XRD, and then the data is read by Rigaku Integral Int. Calculation software.

[0060] According to the present invention, the compaction density of the positive electrode material is ≥2.2g / cm 3 , preferably ≥2.5g / cm 3 , more preferably ≥2.8g / cm 3 .

[0061] According to the present invention, the specific surface area SSA of the positive electrode material satisfies: 0.3m 2 / g≤SSA≤3m 2 / g, preferably 0.5m 2 / g≤SSA≤2.5.

[0062] According to the present invention, the surface Li2CO3 content of the positive electrode material is less than or equal to 2700 ppm, preferably less than or equal to 2400 ppm, and more preferably less than or equal to 2000 ppm; the surface LiOH content of the positive electrode material is less than or equal to 1600 ppm, preferably less than or equal to 1400 ppm, and more preferably less than or equal to 1200 ppm.

[0063] A second aspect of the present invention provides a method for preparing the above-mentioned lithium-rich manganese oxide positive electrode material, characterized in that the preparation method comprises the following steps:

[0064] The precursor containing manganese and M1, a lithium source and an additive optionally containing element M2 are uniformly mixed, and the mixed material is subjected to a two-stage temperature-raising sintering to obtain the lithium-rich manganese oxide positive electrode material;

[0065] The amount of the lithium source, the amount of the precursor, and the amount of the additive containing the element M2 are such that n(Li) / [n(Mn)+n(M1)+n(M2)] is 1.28-1.5;

[0066] The two-stage temperature rise sintering includes the following steps: heating from room temperature to a first sintering temperature at a first heating rate, performing a first sintering, and then heating to a second sintering temperature at a second heating rate, performing a second sintering; wherein the first heating rate is greater than or equal to the second heating rate.

[0067] In the present invention, the monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn1-b M′ b The M and M′ in O2 are derived from the M1 element in the precursor and the additive containing the element M2.

[0068] In the present invention, the inventors have found that by regulating the lithium ratio (n(Li) / [n(Mn)+n(M1)+n(M2)]) and sintering system in the preparation method, monoclinic Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b O2 two-phase solid solution composite cathode material xLi[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2·(1-x)LiMn 1-b M′ b O2, and controlling the content of the two phases in an appropriate ratio, the cathode material thus prepared exhibits excellent comprehensive performance, for example, high initial coulombic efficiency, high discharge capacity, high energy efficiency, high rate performance and high cycle performance. If the lithium ratio does not meet the range defined by the present invention, the two phases in the cathode material cannot form a stable solid solution structure, and phase separation occurs, resulting in a significant decrease in the initial coulombic efficiency, discharge capacity, energy efficiency, rate performance and cycle performance of the lithium ion battery containing the cathode material.

[0069] In the present invention, the inventors have found that the monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 and hexagonal LiMn 1-b M′ b O2 two-phase solid solution composite cathode material xLi[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2·(1-x)LiMn 1-b M′ b O2, and controlling the content of the two phases in an appropriate ratio, the resulting positive electrode material exhibits excellent comprehensive performance, for example, high first coulombic efficiency, high discharge capacity, high energy efficiency, high rate performance and high cycle performance.

[0070] Furthermore, the amount of the lithium source, the amount of the precursor and the amount of the additive containing the element M2 are such that n(Li) / [n(Mn)+n(M1)+n(M2)] is 1.28-1.5, preferably 1.3-1.45.

[0071] According to the present invention, M1 and M2 are the same or different and are each independently selected from at least one element of Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, Na, La, Os, Pr, Re, Ru, Sr, Sm, Ta and B.

[0072] In the present invention, when the mixed materials are sintered, some elements in M1 and M2 can achieve directional element lattice substitution, such as Nb, Ru, Mo, Co, Ti or Zr can be directionally doped into the monoclinic phase Li[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2 neutralizes hexagonal LiMn 1-b M′ b O2, and other elements in M1 and M2 except Nb, Ru, Mo, Co, Ti or Zr can only be doped into the hexagonal phase LiMn 1-b M′ b O2 structure, and then the lithium-rich manganese oxide positive electrode material of the present invention is prepared.

[0073] In the present invention, there is no particular limitation on the type of additive containing element M2, as long as it can provide element M2, for example, it contains at least one of oxides, hydroxides, oxyhydroxides, phosphates, fluorides, borides, and carbonates of element M2.

[0074] According to the present invention, the amount of the additive containing the element M2 and the amount of the precursor are such that: n(M2) / [n(Mn)+n(M1)+n(M2)] is 0-0.1.

[0075] In the present invention, when the amount of the additive containing element M2 is controlled to meet the above range, the element can be doped into the interior of the crystal lattice as much as possible and the doping can be uniform, avoiding residue on the surface of the material and local enrichment, so that the material can exhibit higher capacity and better cycle performance.

[0076] Furthermore, the amount of the additive containing the element M2 and the amount of the precursor are such that: n(M2) / [n(Mn)+n(M1)+n(M2)] is 0.001-0.05.

[0077] In the present invention, the M1 element in the precursor is introduced by adding sulfate, chloride, nitrate, acetate, citrate, carbonate, phosphate, oxalate or fluoride containing the M1 element during the co-precipitation of the precursor.

[0078] According to the present invention, the chemical formula of the precursor is Mn v M 1γ (OH) 2±δ or Mn v M 1γ CO3;

[0079] Among them, 0.4≤v≤0.8, 0.2≤γ≤0.6, 0≤δ≤0.1.

[0080] In the present invention, there is no particular limitation on the preparation method of the precursor, and the precursor can be prepared by conventional methods in the art.

[0081] In the present invention, there is no particular limitation on the lithium source, and conventional lithium sources in the art may be used, such as at least one of lithium hydroxide, lithium carbonate, and lithium nitrate.

[0082] According to the present invention, during the two-stage temperature-raising sintering process, the second sintering temperature is controlled to be 800-1050° C., and the two-stage temperature-raising sintering is performed in an oxygen-containing atmosphere.

[0083] Furthermore, the two-stage temperature rising sintering includes the following steps: heating from room temperature to a first sintering temperature at a first heating rate of ≥5°C / min, performing a first sintering, and then heating to a second sintering temperature at a second heating rate of ≤5°C / min, performing a second sintering, and the temperature of the second sintering is 800-1050°C.

[0084] In the present invention, further controlling the first heating rate and the second heating rate to meet the above-mentioned range will help the positive electrode material provided by the present invention to have appropriate crystallinity and primary particle size, orderly atomic arrangement, and at the same time, it can help to uniformly lithiation during the reaction, avoid the situation where the material is lithium-rich on the outside and lithium-poor on the inside, and enhance the degree and effect of two-phase solid solubility, thereby making the prepared positive electrode material exhibit excellent comprehensive performance, for example, high first coulombic efficiency, high discharge capacity, high energy efficiency, high rate performance and high cycle performance.

[0085] Furthermore, the first heating rate is 5°C / min-10°C / min, and the second heating rate is 1°C / min-4°C / min.

[0086] According to the present invention, the first sintering temperature is 300-600° C., and the first sintering time is 2-6 hours.

[0087] Furthermore, the first sintering temperature is 400-550° C., and the first sintering time is 3-5 hours.

[0088] According to the present invention, the second sintering temperature is 800-1050° C., and the second sintering time is 6-15 hours.

[0089] Furthermore, the second sintering temperature is 800-950° C., and the second sintering time is 6-12 hours.

[0090] According to the present invention, the sintering is performed in an oxygen-containing atmosphere.

[0091] In the present invention, the oxygen-containing atmosphere is selected from one of air, a mixture of oxygen and air, or a mixture of air and carbon dioxide.

[0092] In a more preferred embodiment of the present invention, the lithium ratio (n(Li) / [n(Mn)+n(M1)+n(M2)]), the sintering step, and the types of M1 and M2 simultaneously meet the requirements of the present invention, which can further improve the comprehensive performance of the positive electrode material obtained thereby.

[0093] A third aspect of the present invention provides a positive electrode sheet, wherein the positive electrode sheet includes a positive electrode active material, wherein the positive electrode active material includes a lithium-rich manganese oxide positive electrode material, a conductive agent, and a binder; wherein the content of the lithium-rich manganese oxide positive electrode material is not less than 90 wt % based on the total weight of the positive electrode active material;

[0094] Wherein, the lithium-rich manganese oxide positive electrode material is the above-mentioned lithium-rich manganese oxide positive electrode material.

[0095] A fourth aspect of the present invention provides a use of the above-mentioned lithium-rich manganese oxide positive electrode material or the above-mentioned positive electrode sheet in a lithium-ion battery.

[0096] The present invention will be described in detail below through examples.

[0097] In the following examples and comparative examples:

[0098] Unless otherwise specified, all raw materials are commercially available.

[0099] Unless otherwise specified, all ratios and dosage ratios are molar ratios.

[0100] In the following examples, the performance involved is achieved by:

[0101] (1) XRD phase analysis: The XRD results were obtained using a 9kW X-ray diffractometer from Rigaku Corporation (X-ray wavelength: 0.154 nm), with a scanning range of 17–22° and 42–47°, a step size of 0.02°, and a scanning rate of 1° / min.

[0102] (2) Specific surface area: measured by a Tristar II 3020 surface area tester from Micromertics, USA;

[0103] (3) Compacted density: obtained by using a powder impedance tester MCP-PD51 manufactured by Mitsubishi Chemical of Japan, with a test pressure of 20 kN;

[0104] (4) Surface residual alkali test: measured by titration with a Swiss Metrohm Mystic intelligent potentiometric titrator using 0.1 mol / L standard hydrochloric acid solution;

[0105] (5) Morphology test: obtained by scanning electron microscope S-4800 model of Hitachi HITACHI Company, Japan;

[0106] (6) Electrochemical performance test:

[0107] The electrochemical performance of the prepared lithium-rich manganese oxide cathode material was tested on 2025-type button batteries using the Xinwei battery testing system. Specifically:

[0108] 1) The preparation process of 2025 button battery is as follows:

[0109] Preparation of pole pieces: The lithium-rich manganese oxide positive electrode material, conductive agent carbon black, binder polyvinylidene fluoride are mixed thoroughly with an appropriate amount of N-methylpyrrolidone in a mass ratio of 95:3:2 to form a uniform slurry, which is then coated on aluminum foil, dried at 120°C, rolled, and punched to form a positive electrode piece with a diameter of 11 mm.

[0110] Assemble the battery: the negative electrode uses a Li metal sheet with a diameter of 17 mm and a thickness of 1 mm; the separator uses a polyethylene porous membrane with a thickness of 25 μm; the electrolyte uses an equal mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC).

[0111] The positive electrode sheet, separator, negative electrode sheet and electrolyte were assembled into a 2025 button cell in an Ar glove box with a water and oxygen content of less than 5 ppm. The cell at this point was considered an unactivated cell.

[0112] 2) Electrochemical performance test:

[0113] The button cell test conditions are as follows: After making the button cell, let it sit for 2 hours. After the open-circuit voltage stabilizes, it is charged to a cutoff voltage of 4.6V at a current density of 0.1C at the positive electrode. Then, it is charged at a constant voltage of 0.02C for 30 minutes, and then discharged to a cutoff voltage of 2V at the same current density. This process is repeated once, and the battery at this point is considered an activated battery. Using the activated battery, charge and discharge tests are conducted in the voltage range of 2-4.6V, at 25°C, in the charge and discharge range of 2-4.6V, and at 0.1C to evaluate the charge and discharge capacity of the material. Using the activated battery, charge and discharge tests are conducted at 0.1C, 0.2C, 0.33C, 0.5C, and 1C, and the ratio of 1C capacity to 0.1C capacity is used to evaluate the material's rate performance. The material's cyclic performance is evaluated by 80 charge and discharge cycles at 1C in the range of 2-4.6V.

[0114] The following preparation examples are used to illustrate the preparation of the precursor containing manganese and M1 in the present invention.

[0115] Preparation Example 1

[0116] Manganese sulfate and nickel sulfate (M1 element is Ni) are dissolved in a molar ratio of Mn to Ni of 2:1 to obtain a sulfate solution, sodium hydroxide is dissolved into an alkaline solution with a concentration of 6 mol / L, and ammonia water is dissolved into a complexing agent solution with a concentration of 5 mol / L. The sulfate solution, alkaline solution, and complexing agent solution are then added to a 20L reactor in parallel for reaction. The stirring speed is kept constant at 600 rpm during the process, while the flow rate of the mixed salt solution is controlled to 300 mL / h, the reaction pH is controlled to 11.6, the reaction temperature is 40°C, and the ammonia concentration in the reaction system is controlled to 2 g / L. The entire reaction process is carried out in N2 gas, and the reaction is maintained for 60 hours. The slurry obtained by the precipitation crystallization reaction is subjected to solid-liquid separation and washing, and then dried at 105°C for 10 hours. After sieving, a slurry with a composition of Mn 0.667 Ni 0.333 (OH)2 precursor material, denoted as P-1.

[0117] Preparation Example 2

[0118] The precursor was prepared according to the method of Preparation Example 1, except that the ratio of manganese sulfate to nickel sulfate was different. Specifically, manganese sulfate and nickel sulfate were dissolved in a molar ratio of Mn to Ni of 3:2 to obtain a sulfate solution. 0.6 Ni 0.4 (OH)2 precursor material, denoted as P-2.

[0119] Preparation Example 3

[0120] The precursor was prepared according to the method of Preparation Example 1, except that the ratio of manganese sulfate to nickel sulfate was different. Specifically, manganese sulfate and nickel sulfate were dissolved in a molar ratio of Mn to Ni of 3:1 to obtain a sulfate solution. 0.75 Ni 0.25 (OH)2 precursor material, denoted as P-3.

[0121] The following examples are used to illustrate the lithium-rich manganese oxide positive electrode material prepared by the present invention.

[0122] Example 1

[0123] The precursor P-1, lithium hydroxide, additive Al2O3 and Co(OH)2 were mixed uniformly in a high-pressure mixer according to n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.4, n(Al):[n(Ni)+n(Mn)+n(Al)+n(Co)]=0.002, n(Co):[n(Ni)+n(Mn)+n(Al)+n(Co)]=0.002; in an air atmosphere, the temperature was first increased from room temperature to 400°C at a first heating rate of 5°C / min, kept warm for 5 hours, and then increased to 900°C at a second heating rate of 3°C / min, kept warm for 10 hours, and cooled naturally to obtain the positive electrode material S-1.

[0124] The chemical formula of the positive electrode material S-1 is: 0.5Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.5LiMn 0.4423 Ni 0.5529 Al 0.0032 Co 0.0016 O2.

[0125] Example 2

[0126] A method similar to that of Example 1 was used, except that the amount of lithium salt added was different, specifically:

[0127] n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.3. Positive electrode material S-2 was obtained.

[0128] The chemical formula of the positive electrode material S-2 is: 0.391Li[Li 1 / 3 (Mn 0.99745 Co 0.00255 ) 2 / 3 ]O2·0.609LiMn 0.5214 Ni 0.4740 Al 0.0029 Co 0.0017 O2.

[0129] Example 3

[0130] A method similar to that of Example 1 was used, except that the amount of lithium salt added was different, specifically:

[0131] n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.45, and the positive electrode material S-3 was obtained.

[0132] The chemical formula of the positive electrode material S-3 is: 0.551Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.449LiMn 0.3919 Ni 0.6029 Al 0.0036 Co 0.0016 O2.

[0133] Example 4

[0134] A method similar to that of Example 1 was used, except that the amount of lithium salt added was different, specifically: n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.5. The positive electrode material S-4 was obtained. The chemical formula of the positive electrode material S-4 is: 0.6Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.4LiMn 0.3314 Ni 0.6630 Al 0.004 Co 0.0016 O2.

[0135] Example 5

[0136] A method similar to that of Example 1 was used, except that the precursor P-1, lithium hydroxide and additive Co(OH)2 were uniformly mixed in a high-speed mixer according to n(Li):[n(Ni)+n(Mn)+n(Co)]=1.40, n(Co):[n(Ni)+n(Mn)+n(Co)]=0.002 to obtain the positive electrode material S-5.

[0137] The chemical formula of the positive electrode material S-5 is: 0.5Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.5LiMn 0.4437 Ni 0.5547 Co 0.0016 O2.

[0138] The SEM image of the positive electrode material S-5 is shown in FIG6 , from which it can be seen that the positive electrode material is spherical particles.

[0139] Example 6

[0140] A method similar to that of Example 1 was used, except that the precursor P-1, lithium hydroxide, and the additive Al2O3 were uniformly mixed in a high-speed mixer at a ratio of n(Li):[n(Ni)+n(Mn)+n(Al)]=1.40 and n(Al):[n(Ni)+n(Mn)+n(Al)]=0.002. This yielded the positive electrode material S-6.

[0141] The chemical formula of the positive electrode material S-6 is: 0.5Li[Li 1 / 3 (Mn1) 2 / 3 ]O2·0.5LiMn 0.4429 Ni 0.5538 Al 0.0033 O2.

[0142] Example 7

[0143] The same synthesis method and conditions as in Example 1 were used, except that the precursor P-1 and lithium hydroxide were mixed uniformly in a high-pressure mixer according to n(Li):[n(Ni)+n(Mn)]=1.40 to obtain the positive electrode material S-7. The chemical formula of the positive electrode material S-7 is: 0.5Li[Li 1 / 3 (Mn1) 2 / 3 ]O2·0.5LiMn 0.4444 Ni 0.5556 O2.

[0144] Example 8

[0145] The precursor P-2, lithium hydroxide, additive tungsten oxide and titanium dioxide were mixed uniformly in a high-pressure mixer according to n(Li):[n(Mn)+n(Ni)+n(W)+n(Ti)]=1.35, n(W):[n(Mn)+n(Ni)+n(W)+n(Ti)]=0.002, n(Ti):[n(Mn)+n(Ni)+n(W)+n(Ti)]=0.005. In an oxygen atmosphere, the temperature was first increased from room temperature to 600°C at a first heating rate of 8°C / min, kept warm for 5 hours, and then increased to 850°C at a second heating rate of 3°C / min, kept warm for 10 hours, and naturally cooled to obtain the positive electrode material S-8.

[0146] The chemical formula of the positive electrode material S-8 is: 0.447Li[Li 1 / 3 (Mn 0.99355 Ti 0.00645 ) 2 / 3]O2·0.553LiMn 0.3818 Ni 0.6108 Ti 0.0043 W 0.0031 O2.

[0147] Example 9

[0148] The precursor P-3, lithium hydroxide, additives molybdenum oxide and cobalt oxide were mixed uniformly in a high-pressure mixer according to n(Li):[n(Mn)+n(Ni)+n(Co)+n(Mo)]=1.38, n(Mo):[n(Mn)+n(Ni)+n(Co)+n(Mo)]=0.02, n(Co):[n(Mn)+n(Ni)+n(Co)+n(Mo)]=0.05. In an air atmosphere, the temperature was first increased from room temperature to 500°C at a first heating rate of 10°C / min, kept warm for 4 hours, and then heated to 1000°C at a second heating rate of 4°C / min, and kept warm for 10 hours to obtain the positive electrode material S-9.

[0149] Among them, the chemical formula of the positive electrode material S-9 is: 0.479Li[Li 1 / 3 (Mn 0.9118 Co 0.063 Mo 0.0252 ) 2 / 3 ]O2·0.521LiMn 0.5617 Ni 0.3795 Co 0.042 Mo 0.0168 O2.

[0150] Comparative Example 1

[0151] A method similar to that of Example 1 was used, except that the amount of lithium salt added was different, specifically:

[0152] n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.55. The positive electrode material D-1 was obtained. The chemical formula of the positive electrode material is: 0.647Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.353LiMn 0.2577 Ni 0.7362 Al 0.0044 Co 0.0016 O2.

[0153] Comparative Example 2

[0154] A method similar to that of Example 1 was used, except that the amount of lithium salt added was different, specifically: n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.25. A positive electrode material D-2 was obtained, and the chemical formula of the positive electrode material was: 0.333Li[Li 1 / 3 (Mn 0.9973 Co 0.0027 ) 2 / 3 ]O2·0.667LiMn 0.5531 Ni 0.4424 Al 0.0027 Co 0.0018 O2.

[0155] Comparative Example 3

[0156] A method similar to that of Example 5 was used, except that the temperature was directly raised to 900°C at 5°C / min and kept at this temperature for 10 hours to obtain the positive electrode material D-3. The chemical formula of the positive electrode material is: 0.5Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.5LiMn 0.4437 Ni 0.5547 Co 0.0016 O2.

[0157] Comparative Example 4

[0158] A method similar to that of Example 5 was used, except that the temperature was first increased from room temperature to 400°C at a first heating rate of 3°C / min and kept at that temperature for 5 h, and then increased to 900°C at a second heating rate of 10°C / min and kept at that temperature for 10 h to obtain a positive electrode material D-4. The chemical formula of the positive electrode material is: 0.5Li[Li 1 / 3 (Mn 0.9976 Co 0.0024 ) 2 / 3 ]O2·0.5LiMn 0.4437 Ni 0.5547 Co 0.0016 O2.

[0159] The XRD spectra of the positive electrode materials S-1 to S-4 of Examples 1 to 4 and the positive electrode material D-2 of Comparative Example 2 are shown in Figures 1 to 5, respectively. As can be seen from Figures 1 to 5, the two-phase ratio and two-phase solid solubility in the positive electrode materials provided by the present invention are good. Specifically, the XRD P (1) The peak is a single peak with good symmetry, while the peak in the XRD pattern of the positive electrode material of Comparative Example 2 is split, indicating that the ratio of the two phases is inappropriate and the solid solubility of the two phases is poor.

[0160] Test Example 1

[0161] The structures and properties of the lithium-rich manganese oxide positive electrode materials prepared in Examples 1-9 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0162] Table 1

[0163] It can be seen from the results in Table 1 that compared with Comparative Examples 1-4, the P (1) , P (2) , FWHM (1) , FWHM (2) and S (2) / S (1) All of them are within the required range of the present invention, and therefore have good electrochemical performance.

[0164] Test Example 2

[0165] The lithium-rich manganese oxide positive electrode materials prepared in Examples 1-9 and Comparative Examples 1-4 were used as positive electrode sheets of lithium-ion batteries to prepare lithium-ion batteries. The performance of the lithium-ion batteries was tested, and the results are shown in Table 2.

[0166] Table 2

[0167] It can be seen from Table 2 that by comparing Example 1, Example 2, Example 3 and Example 4, the capacity, energy efficiency, rate performance and cycle performance of the positive electrode material can be regulated, and the performance is optimal when n(Li):[n(Ni)+n(Mn)+n(Al)+n(Co)]=1.4; by comparing Example 1 and Example 5, it is found that doping Al in the hexagonal phase can significantly improve the discharge capacity and cycle performance of the material; by comparing Example 1 and Example 6, it is found that increasing Co doping in the monoclinic phase and the hexagonal phase can significantly improve the discharge capacity, rate performance and cycle performance of the material; by comparing Example 1 and Example 7, it is found that doping Co in the monoclinic phase and doping Co and Al in the hexagonal phase at the same time play an important role in improving the discharge capacity, rate performance and cycle performance of the material; by comparing Examples 1-4 and Comparative Examples 1-2, it is found that the content ratio of the two phases has a great influence on the capacity, rate and cycle of the material, and the performance is significantly better within the range provided by the present invention. By comparing Example 5 with Comparative Examples 3-4, it is found that the two-stage sintering system and the appropriate heating rate can improve the capacity, rate and cycle performance of the material.

[0168] The first charge and discharge curves of Example 1, Example 4 and Comparative Example 2 are shown in FIG7 . As can be seen from FIG7 , the discharge capacity of the lithium-ion batteries assembled with the positive electrode materials of Example 1 and Example 4 is significantly higher than that of Comparative Example 2, indicating that the appropriate two-phase content ratio and the degree of solid solubility of the two phases are crucial to the performance of the material, otherwise the capacity will be very low.

[0169] The initial charge and discharge curves for Examples 1, 5, and 6 are shown in Figure 8. As can be seen from Figure 8, compared with Example 5, the addition of Al doping to the hexagonal phase in Example 1 does not reduce the discharge capacity, but the charge-discharge voltage difference decreases, indicating that the polarization of the material is reduced and the kinetics are improved. Compared with Example 1 and Example 6, the addition of Co lattice doping to the monoclinic and hexagonal phases further increases the discharge capacity and improves the material reaction kinetics.

[0170] The first charge and discharge curves of Example 5 and Comparative Example 3 are shown in FIG9 . As can be seen from FIG9 , the use of two-stage temperature increase and control of the reaction rate can significantly improve the discharge capacity of the material.

[0171] Figure 10 shows the voltage cycle diagram of a lithium-ion battery assembled from cathode materials S-1 and S-5. As can be seen from Figure 10, adding Al doping to the hexagonal phase can effectively improve the voltage retention of the cathode material.

[0172] FIG11 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material S-5. As can be seen from FIG11 , adding Al doping to the hexagonal phase can effectively improve the capacity retention rate of the positive electrode material.

[0173] FIG12 is a voltage cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material D-2. As can be seen from FIG12 , controlling the ratio of the two phases and the degree of solid solubility of the two phases can effectively improve the voltage retention rate of the positive electrode material.

[0174] FIG13 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-1 and positive electrode material D-2. As can be seen from FIG13 , regulating the ratio of the two phases and the degree of solid solubility of the two phases can effectively improve the capacity retention rate of the positive electrode material.

[0175] FIG14 is a voltage cycle diagram of a lithium-ion battery assembled from positive electrode material S-5 and positive electrode material D-3. FIG14 shows that the voltage retention rate of the positive electrode material can be effectively improved by adopting two-stage heating and controlling the reaction rate.

[0176] FIG15 is a capacity cycle diagram of a lithium-ion battery assembled from positive electrode material S-5 and positive electrode material D-3. As can be seen from FIG15 , the capacity retention rate of the positive electrode material can be effectively improved by adopting two-stage heating and controlling the reaction rate.

[0177] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A lithium-rich manganese oxide positive electrode material, characterized in that: The chemical formula of the lithium-rich manganese oxide positive electrode material is: xLi[Li 1 / 3 (Mn 1-a M a ) 2 / 3 ]O2·(1-x)LiMn 1-b M′ b O2; The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ1 of [43.5(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°. (1) ; The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the range of diffraction angle 2θ2 of [17.7(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°. (2) . Among them, x satisfies: 0.35≤x≤0.

63.

2. The lithium-rich manganese oxide positive electrode material according to claim 1, wherein: [43.6(1-x)+44x]°≤2θ1≤[44(1-x)+45x]°; Preferably, [17.8(1-x)+18.3x]°≤2θ2≤[19.2(1-x)+19.8x]°; Preferably, 0.4≤x≤0.

55.

3. The lithium-rich manganese oxide positive electrode material according to claim 1, wherein: 0≤a≤0.1, 0.15≤b≤0.85, M is selected from at least one element of Nb, Ru, Mo, Co, Ti and Zr; M′ is selected from at least one element of Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, Na, La, Os, Pr, Re, Ru, Sr, Sm, Ta and B.

4. The lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 3, wherein: The XRD spectrum of the positive electrode material obtained by XRD has a diffraction peak P in the diffraction angle range of 2θ1. (1) The half-peak width meets: 0.35≤FWHM (1) ≤0.50, preferably 0.38≤FWHM (1) ≤0.45; Preferably, the positive electrode material has a diffraction peak P in the diffraction angle range of 2θ2 in the XRD spectrum obtained by XRD. (2) FWHM (2) Satisfy: 0.17 ≤ FWHM (2) ≤0.28, preferably 0.18≤FWHM (2) ≤0.

24.

5. The lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 4, wherein: The positive electrode material has a diffraction peak P in the diffraction angle range of 2θ2 obtained by XRD. (2) The peak area S (2) The diffraction peak P exists within the diffraction angle range of 2θ1 (1) The peak area S (1) The following conditions are met: 1.1≤S (2) / S (1) ≤1.8, preferably 1.2≤S (2) / S (1) ≤1.

7.

6. The lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 5, wherein: The compaction density of the positive electrode material is ≥2.2g / cm 3 , preferably ≥2.5g / cm 3 , more preferably ≥2.8g / cm 3 ; Preferably, the specific surface area SSA of the positive electrode material satisfies: 0.3 m 2 / g≤SSA≤3m 2 / g, preferably 0.5m 2 / g≤SSA≤2.5; Preferably, the surface Li2CO3 content of the positive electrode material is less than or equal to 2700 ppm, preferably less than or equal to 2400 ppm, more preferably less than or equal to 2000 ppm; the surface LiOH content of the positive electrode material is less than or equal to 1600 ppm, preferably less than or equal to 1400 ppm, more preferably less than or equal to 1200 ppm.

7. A method for preparing the lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The precursor containing manganese and M1, the lithium source and the additive optionally containing the element M2 are uniformly mixed, and the mixed material is subjected to two-stage temperature-raising sintering to obtain the lithium-rich manganese oxide positive electrode material; The amount of the lithium source, the amount of the precursor and the amount of the additive containing the element M2 are such that n(Li) / [n(Mn)+n(M1)+n(M2)] is 1.28-1.5; The two-stage temperature rise sintering includes the following steps: heating from room temperature to a first sintering temperature at a first heating rate to perform a first sintering, and then heating to a second sintering temperature at a second heating rate to perform a second sintering; wherein the first heating rate is greater than or equal to the second heating rate.

8. The preparation method according to claim 7, wherein: The amount of the lithium source, the amount of the precursor and the amount of the additive containing the element M2 are such that n(Li) / [n(Mn)+n(M1)+n(M2)] is 1.3-1.45; Preferably, M1 and M2 are the same or different and are each independently selected from at least one element of Ni, Co, Al, Zr, Nb, Ti, Sc, Y, Sn, Cr, W, Mg, Mo, Na, La, Os, Pr, Re, Ru, Sr, Sm, Ta and B; Preferably, the amount of the additive containing the element M2 and the amount of the precursor are such that: n(M2) / [n(Mn)+n(M1)+n(M2)] is 0-0.1, preferably 0.001-0.05; Preferably, the chemical formula of the precursor is Mn v M 1γ (OH) 2±δ or Mn v M 1γ CO3; Among them, 0.4≤v≤0.8, 0.2≤γ≤0.6, 0≤δ≤0.

1.

9. The preparation method according to claim 7 or 8, wherein: The second stage of temperature rising sintering is carried out in an oxygen-containing atmosphere; Preferably, the second sintering temperature is controlled to be 800-1050°C; Preferably, the two-stage temperature rise sintering comprises the following steps: heating from room temperature to a first sintering temperature at a first heating rate of ≥5°C / min; The first sintering is performed at a temperature of 800-1050°C, and then the temperature is raised to a second sintering temperature at a second heating rate of ≤5°C / min, and the second sintering is performed. Preferably, the first sintering temperature is 300-600° C., and the first sintering time is 2-6 hours; Preferably, the second sintering temperature is 800-1050° C., and the second sintering time is 6-15 hours; Preferably, the sintering is performed in an oxygen-containing atmosphere.

10. A positive electrode sheet, characterized in that: The positive electrode sheet comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-rich manganese oxide positive electrode material, a conductive agent and a binder; wherein the content of the lithium-rich manganese oxide positive electrode material is not less than 90wt% based on the total weight of the positive electrode active material; Wherein, the lithium-rich manganese oxide positive electrode material is the lithium-rich manganese oxide positive electrode material according to any one of claims 1-6.

11. Use of the lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 6 or the positive electrode sheet according to claim 10 in a lithium-ion battery.

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