Lithium-rich manganese-based positive electrode material and preparation method thereof, electrode sheet and battery

Abstract

The present application discloses a method for preparing a lithium-rich manganese-based positive electrode material, comprising: dissolving a soluble lithium salt, a soluble nickel salt, and a soluble manganese salt in water, adding a first organic solvent to obtain a mixed solution; dissolving oxalic acid in a second organic solvent to obtain an oxalic acid solution; adding the mixed solution to the oxalic acid solution to obtain a lithium-rich manganese oxalate precursor; calcining, heating the lithium-rich manganese oxalate precursor to 350-550°C at a heating rate V1 and maintaining the temperature to obtain a lithium-rich manganese-based material; and over-burning, heating the lithium-rich manganese-based material to 900-1000°C at a heating rate V2 and maintaining the temperature to form a transition metal oxide layer with cation vacancies on the surface of the lithium-rich manganese-based material. The transition metal oxide layer with cation vacancies can weaken or even inhibit the structural transformation of the lithium-rich manganese-based positive electrode material during the charge and discharge process, thereby improving the cycle stability and capacity retention of the lithium-rich manganese-based positive electrode material. The present application also discloses a lithium-rich manganese-based positive electrode material, an electrode sheet, and a battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a lithium-rich manganese-based positive electrode material, a method for preparing the lithium-rich manganese-based positive electrode material, an electrode sheet comprising the lithium-rich manganese-based positive electrode material, and a battery comprising the electrode sheet. Background Art

[0002] Lithium-rich manganese cathode materials have high specific capacity and are + In the test, the specific capacity exceeded 250mAh / g, which can provide electric vehicles with longer driving range and is the preferred material for the next generation of power batteries.

[0003] However, lithium-rich manganese-based cathode materials have a wide voltage window, with oxygen release in the high-voltage platform, and as lithium ions are deintercalated, transition metals migrate to the lithium layer, causing the material's crystalline structure to change. Specifically, as the charge and discharge cycles proceed, the material structure changes from the outside to the inside, from the initial layered structure to the spinel structure, and then from the spinel structure to the rock salt phase. During this process, the material's capacity will continue to decay, and the midpoint voltage platform will continue to decrease, causing the performance of the lithium-rich manganese-based cathode material to continue to decline as the charge and discharge cycles proceed, resulting in poor cycle stability and capacity retention of the lithium-rich manganese-based cathode material. Summary of the Invention

[0004] In view of this, the present application provides a lithium-rich manganese-based positive electrode material and a preparation method thereof, aiming to improve the problems of poor cycle stability and capacity retention of existing lithium-rich manganese-based positive electrode materials.

[0005] The embodiment of the present application is implemented as follows: a method for preparing a lithium-rich manganese-based positive electrode material comprises the following steps:

[0006] Dissolving a soluble lithium salt, a soluble nickel salt, and a soluble manganese salt in water, and then adding a first organic solvent to obtain a mixed solution;

[0007] dissolving oxalic acid in a second organic solvent to obtain an oxalic acid solution;

[0008] adding the mixed solution to the oxalic acid solution, co-precipitating, and drying to obtain a lithium-rich manganese oxalate precursor;

[0009] Calcination: heating the lithium-rich manganese oxalate precursor to 350-550° C. at a heating rate V1 and maintaining the temperature to obtain a lithium-rich manganese-based material;

[0010] Over-firing: heating the lithium-rich manganese-based material to 900-1000° C. at a heating rate V2 and maintaining the temperature to form a transition metal oxide layer on the surface of the lithium-rich manganese-based material, thereby obtaining a lithium-rich manganese-based positive electrode material.

[0011] Optionally, the soluble lithium salt is selected from at least one of lithium acetate, lithium carbonate, lithium nitrate, lithium sulfate and lithium chloride; and / or

[0012] The soluble nickel salt is selected from at least one of nickel acetate, nickel sulfate, nickel nitrate, nickel chloride and nickel bromide; and / or

[0013] The soluble manganese salt is at least one selected from manganese acetate, manganese sulfate, manganese nitrate, manganese chloride and manganese bromide.

[0014] Optionally, the soluble lithium salt is selected from at least one of lithium acetate, lithium carbonate, lithium nitrate, lithium sulfate and lithium chloride; and / or

[0015] The soluble nickel salt is selected from at least one of nickel acetate, nickel sulfate, nickel nitrate, nickel chloride and nickel bromide; and / or

[0016] The soluble manganese salt is at least one selected from manganese acetate, manganese sulfate, manganese nitrate, manganese chloride and manganese bromide.

[0017] Optionally, the first organic solvent is selected from at least one of ethanol, ethylene glycol, isopropanol and polyols; and / or

[0018] The second organic solvent may be selected from, but not limited to, at least one of ethanol, ethylene glycol, isopropanol, and polyols.

[0019] Optionally, the molar ratio of the soluble lithium salt, the soluble nickel salt, the soluble manganese salt and the oxalic acid is in the range of (1.2-1.3):0.2:0.6:1.

[0020] Optionally, the heating rate V1 is in the range of 1.2 to 5°C / min; and / or

[0021] The range of the heating rate V2 is 1.2-5°C / min.

[0022] Optionally, the transition metal oxide is Ni6MnO8.

[0023] Optionally, the thickness of the transition metal oxide layer is in the range of 2-10 nm.

[0024] Optionally, the chemical formula of the lithium-rich manganese-based material is Li 0.2 Ni 0.2 Mn 0.6 O2.

[0025] Correspondingly, the present application also provides a lithium-rich manganese-based material, which is prepared by the above preparation method.

[0026] Correspondingly, the present application also provides an electrode sheet, which includes the above-mentioned lithium-rich manganese-based material.

[0027] Correspondingly, the present application also provides a battery, which includes the above-mentioned electrode sheet.

[0028] The lithium-rich manganese-based positive electrode material of the present application includes a lithium-rich manganese-based material and a transition metal oxide layer coated on the surface of the lithium-rich manganese-based material. The transition metal oxide layer can effectively weaken or even inhibit the structural transformation of the lithium-rich manganese-based positive electrode material during the charge and discharge process, that is, weaken or even inhibit the transformation of the layered structure → spinel structure → rock salt structure that may occur in the lithium-rich manganese-based positive electrode material during the charge and discharge process, thereby effectively improving the cycle stability and capacity retention rate of the lithium-rich manganese-based positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a flow chart of a method for preparing a lithium-rich manganese-based positive electrode material provided in an embodiment of the present application;

[0031] Figures 2 to 5 This is an SEM image of the lithium-rich manganese-based positive electrode material of Example 1 of the present application;

[0032] Figures 6 to 9 This is a SEM image of the lithium-rich manganese-based positive electrode material of the comparative example of the present application;

[0033] Figure 10 This is a surface EDS image of the lithium-rich manganese-based positive electrode material of Example 1 of the present application;

[0034] Figure 11 This is an EDS image of the grain boundary of the lithium-rich manganese-based positive electrode material of Example 1 of the present application;

[0035] Figure 12 This is the surface EDS image of the lithium-rich manganese-based positive electrode material of the comparative example of the present application;

[0036] Figure 13 This is an EDS image of the grain boundary of the lithium-rich manganese-based positive electrode material of the comparative example of the present application;

[0037] Figure 14 1 is the XRD pattern of the lithium-rich manganese-based positive electrode material of Example 1 and the comparative example of the present application;

[0038] Figure 15 Graph showing the capacity and coulombic efficiency of the lithium-rich manganese-based cathode materials of Example 1 and the comparative example of the present application under 0.1C charge and discharge conditions;

[0039] Figure 16 2. Capacity and Coulombic efficiency of the lithium-rich manganese-based cathode material of Example 1 of the present application under 0.1C charge and discharge conditions for the first three cycles;

[0040] Figure 17 This is a graph of capacity and coulombic efficiency of the first three cycles of the lithium-rich manganese-based positive electrode material under 0.1C charge and discharge conditions in the comparative example of the present application. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application and are not used to limit the present application. In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", specifically refer to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, description of a range from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. Furthermore, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

[0042] See also Figure 1 The present invention provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising the following steps:

[0043] Step S1: dissolving a soluble lithium salt, a soluble nickel salt, and a soluble manganese salt in water, and then adding a first organic solvent to obtain a mixed solution;

[0044] Step S2: dissolving oxalic acid in a second organic solvent to obtain an oxalic acid solution;

[0045] Step S3: adding the mixed solution to the oxalic acid solution, co-precipitating, and drying to obtain a lithium-rich manganese oxalate precursor, wherein the lithium-rich manganese oxalate precursor includes oxalate;

[0046] Step S4: calcining, heating the lithium-rich manganese oxalate precursor to 350-550° C. at a heating rate V1 and maintaining the temperature for a period of time T1 to obtain a lithium-rich manganese-based material having a secondary micron-rod morphology composed of nanoparticles;

[0047] Step S5: over-firing, heating the lithium-rich manganese-based material to 900-1000° C. at a heating rate V2 and keeping the temperature for a period of time T2 to form a transition metal oxide layer on the surface of the lithium-rich manganese-based material to obtain a lithium-rich manganese-based positive electrode material.

[0048] In the step S1:

[0049] The soluble lithium salt is a soluble lithium salt conventionally used to prepare lithium-rich manganese-based positive electrode materials, for example, it can be selected from but not limited to at least one of lithium acetate, lithium carbonate, lithium nitrate, lithium sulfate and lithium chloride.

[0050] The soluble nickel salt is a soluble nickel salt conventionally used to prepare lithium-rich manganese-based positive electrode materials, and can be, for example, selected from but not limited to at least one of nickel acetate, nickel sulfate, nickel nitrate, nickel chloride and nickel bromide.

[0051] The soluble manganese salt is a soluble manganese salt conventionally used to prepare lithium-rich manganese-based positive electrode materials, and can be, for example, selected from but not limited to at least one of manganese acetate, manganese sulfate, manganese nitrate, manganese chloride and manganese bromide.

[0052] The first organic solvent may be selected from, but not limited to, at least one of ethanol, ethylene glycol, isopropanol, and polyols.

[0053] It is understood that the amount of the first organic solvent added is not limited, as long as the first organic solvent can fully dissolve the soluble lithium salt, soluble nickel salt, and soluble manganese salt. In some embodiments, the amount of the first organic solvent added is 100 to 400 g.

[0054] Firstly dissolving the soluble lithium salt, the soluble nickel salt and the soluble manganese salt in water and then adding the first organic solvent can effectively improve the solubility of the soluble lithium salt, the soluble nickel salt and the soluble manganese salt.

[0055] In the step S2:

[0056] The second organic solvent may be selected from, but not limited to, at least one of ethanol, ethylene glycol, isopropanol, and polyols.

[0057] It is understood that the second organic solvent may be the same as or different from the first organic solvent.

[0058] In some embodiments, the concentration of the oxalic acid solution ranges from 0.0001 mol / L to 3 mol / L. Too low a concentration of the oxalic acid solution results in incomplete precipitation, while too high a concentration results in waste of resources.

[0059] In some embodiments, step S3 specifically includes: slowly adding the mixed solution to the oxalic acid solution, mixing and stirring for time T3, co-precipitating, and then transferring to a forced air drying oven for drying to obtain a lithium-rich manganese oxalate precursor.

[0060] The time T3 is in the range of 6 to 24 hours. Within the time range, the soluble lithium salt, soluble nickel salt, soluble manganese salt and oxalic acid can fully react.

[0061] The oxalate may be selected from, but not limited to, at least one of lithium oxalate, nickel oxalate, and manganese oxalate.

[0062] The molar ratio of the soluble lithium salt, soluble nickel salt and soluble manganese salt in step S1 to the oxalic acid in step S2 is (1.2-1.3):0.2:0.6:1. Within the above range, the excess of the soluble lithium salt can effectively compensate for the Li + loss.

[0063] In the step S4:

[0064] The heating rate V1 ranges from 1.2°C / min to 5°C / min. Within this range, the lithium-rich manganese oxalate precursor reacts slowly and evenly, which is conducive to producing a uniform product. Below this range, energy is wasted; above this range, impurities are formed, affecting the purity of the lithium-rich manganese oxalate precursor.

[0065] Calcination within the temperature range of 350-550°C decomposes the oxalate in the lithium-rich manganese oxalate precursor, releasing carbon dioxide and forming a uniform rod-like morphology. Below this temperature range, the oxalate decomposition is incomplete, hindering the formation of the secondary micron-rod-like morphology composed of nanoparticles. Above this temperature range, the oxalate decomposition reaction is vigorous, rapidly releasing gas and destroying the secondary micron-rod-like morphology composed of nanoparticles.

[0066] The time T1 is in the range of 6 to 8 hours. Within the range, the lithium-rich manganese oxalate precursor can be completely calcined without causing energy waste.

[0067] The chemical formula of the lithium-rich manganese-based material is Li 0.2 Ni 0.2 Mn 0.6 O2.

[0068] In the step S5:

[0069] The heating rate V2 ranges from 1.2°C / min to 5°C / min. Within this range, the calcined lithium-rich manganese oxalate precursor undergoes a slow and uniform over-firing reaction, which facilitates the production of a uniform product. A heating rate below this range wastes energy, while a heating rate above this range generates impurities and affects the purity of the material.

[0070] Over-calcination within the temperature range of 900-1000°C can generate transition metal oxide Ni6MnO8, which has a Ni cation vacancy structure, so that the prepared lithium-rich manganese-based positive electrode material has the characteristics of Ni enrichment on the surface and at the grain boundaries. Below the temperature range, the prepared lithium-rich manganese-based positive electrode material will be impure. Above the temperature, Ni6MnO8 with a Ni cation vacancy structure will segregate, which is not conducive to capacity release.

[0071] The time T2 is in the range of 10 to 14 hours. Within the range, the lithium-rich manganese oxalate precursor can be completely calcined without causing energy waste.

[0072] The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material and a transition metal oxide layer coated on the surface of the lithium-rich manganese-based material. 0.2 Ni 0.2 Mn 0.6 O2, the transition metal oxide layer includes Ni6MnO8.

[0073] The transition metal oxide layer in the lithium-rich manganese-based positive electrode material can effectively weaken or even inhibit the structural transformation of the lithium-rich manganese-based positive electrode material during the charging and discharging process, that is, weaken or even inhibit the transformation of the layered structure → spinel structure → rock salt structure that may occur in the lithium-rich manganese-based positive electrode material during the charging and discharging process, thereby effectively improving the cycle stability and capacity retention rate of the lithium-rich manganese-based positive electrode material.

[0074] In some embodiments, the transition metal oxide layer has a thickness in the range of 2-10 nm. Within this thickness range, the structural transformation of the lithium-rich manganese-based cathode material during the charge and discharge process can be effectively weakened or even suppressed, while the electrical properties of the lithium-rich manganese-based cathode material will not be affected due to excessive thickness.

[0075] The present application also provides a lithium-rich manganese-based positive electrode material prepared by the preparation method. The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material and a transition metal oxide layer coated on the surface of the lithium-rich manganese-based material. The chemical formula of the lithium-rich manganese-based material is Li 0.2 Ni 0.2 Mn 0.6O2, the transition metal oxide layer comprises Ni6MnO8. In some embodiments, the thickness of the transition metal oxide layer ranges from 2 nm to 10 nm.

[0076] An embodiment of the present application further provides an electrode sheet, which includes the lithium-rich manganese-based positive electrode material.

[0077] The embodiment of the present application further provides a lithium-ion battery, wherein the lithium-ion battery includes the electrode sheet. It is understood that the electrode sheet is a positive electrode sheet.

[0078] The present application will be described in detail below through specific examples. The following examples are only some examples of the present application and are not limitations of the present application.

[0079] Example 1

[0080] Dissolve 6.1212 g of lithium acetate dihydrate (CH3COOLi·2H2O), 2.488 g of nickel acetate tetrahydrate ((CH3COO)2Ni·4H2O), and 7.3527 g of manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O) in 150 ml of deionized water, stir thoroughly to dissolve, then add 150 ml of ethanol and continue stirring for 10 min to obtain a mixed solution.

[0081] Take 9.14g of oxalic acid and dissolve it in 150ml of ethanol to obtain oxalic acid solution;

[0082] The mixed solution was slowly poured into the oxalic acid solution, and the mixed solution was stirred for 6 hours, and then transferred to a forced air drying oven for drying to obtain a lithium-rich manganese oxalate precursor;

[0083] Calcination: placing the lithium-rich manganese oxalate precursor in a muffle furnace (KSL-1100, Hefei Kejing Materials Co., Ltd.), heating it to 450° C. at a heating rate of 2° C. / min, and keeping it at that temperature for 6 h to obtain a lithium-rich manganese-based material;

[0084] The lithium-rich manganese-based material was heated to 950° C. at a heating rate of 2° C. / min and kept at that temperature for 12 hours to obtain a lithium-rich manganese-based positive electrode material.

[0085] Example 2

[0086] This embodiment is basically the same as embodiment 1, except that the calcination and over-burning steps in this embodiment are:

[0087] Calcination: placing the lithium-rich manganese oxalate precursor in a muffle furnace (KSL-1100, Hefei Kejing Materials Co., Ltd.), heating it to 450° C. at a heating rate of 2° C. / min, and keeping it at that temperature for 6 h to obtain a lithium-rich manganese-based material;

[0088] The lithium-rich manganese-based material was heated to 900° C. at a heating rate of 2° C. / min and kept at that temperature for 12 hours to obtain a lithium-rich manganese-based positive electrode material.

[0089] Example 3

[0090] This embodiment is basically the same as embodiment 1, except that, in this embodiment, the calcination and over-burning steps are as follows:

[0091] Calcination: placing the lithium-rich manganese oxalate precursor in a muffle furnace (KSL-1100, Hefei Kejing Materials Co., Ltd.), heating it to 450° C. at a heating rate of 2° C. / min, and keeping it at that temperature for 6 h to obtain a lithium-rich manganese-based material;

[0092] The lithium-rich manganese-based material was heated to 1000° C. at a heating rate of 2° C. / min and kept at that temperature for 12 h to obtain a lithium-rich manganese-based positive electrode material.

[0093] Example 4

[0094] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the mass of lithium acetate dihydrate is 122.4 g.

[0095] Example 5

[0096] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the mass of lithium acetate dihydrate is 127.5 g.

[0097] Example 6

[0098] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the mass of lithium acetate dihydrate is 132.6 g.

[0099] Comparative Example

[0100] This comparative example is basically the same as Example 1, except that, in this example, the lithium-rich manganese oxalate precursor is placed in a heating furnace, heated to 450°C at a heating rate of 2°C / min, kept warm for 6 hours, and then heated to 850°C at a heating rate of 2°C / min and kept warm for 12 hours to obtain a lithium-rich manganese-based positive electrode material.

[0101] The thickness of the transition metal oxides at the cation vacancies of the lithium-rich manganese-based positive electrode materials of Examples 1-6 was measured. The thickness measurement method was to observe the sample lattice using a transmission electron microscope (TEM). The results showed that the thickness of the transition metal oxides at the cation vacancies of the lithium-rich manganese-based positive electrode materials of Examples 1-6 was 8-10 nm, 5-6 nm, 2-4 nm, 8-10 nm, 5-6 nm, and 2-4 nm, respectively.

[0102] The lithium-rich manganese-based cathode material of Example 1 is labeled LMR-BURNT, and the lithium-rich manganese-based cathode material of the comparative example is labeled LMR. Phase analysis and electrochemical performance analysis of both were performed. Specifically:

[0103] The LMR-BURNT of Example 1 was scanned by SEM electron microscope to obtain the SEM scanning electron microscope. Figures 2 to 5 ;

[0104] The LMR of the comparative example was scanned by SEM electron microscope to obtain the SEM scanning electron microscope Figures 6 to 9 ;

[0105] The LMR-BURNT of Example 1 was subjected to EDS (Energy Dispersive Spectroscopy) analysis to obtain the surface EDS of LMR-BURNT. Figure 10 and EDS at the grain boundaries of LMR-BURNT Figure 11 ;

[0106] The surface EDS of LMR-BURNT was analyzed by EDS. Figure 12 and EDS at the grain boundaries of LMR-BURNT Figure 13 ;

[0107] X-ray diffraction was performed on the LMR-BURNT of Example 1 and the LMR of the comparative example to obtain an X-ray diffraction pattern (XRD pattern) 14;

[0108] The electrochemical performance of the LMR-BURNT of Example 1 and the LMR of the comparative example was analyzed. Specifically, the LMR-BURNT of Example 1 and the LMR of the comparative example were respectively made into electrode sheets, and then the electrode sheets were used as positive electrode materials to prepare a test battery. The test battery includes a housing and a positive electrode current collector, a positive electrode, a separator, an electrolyte, a negative electrode and a negative electrode current collector arranged in the housing. The battery was tested to obtain the capacity and coulombic efficiency of the battery made of the LMR-BURNT of Example 1 and the LMR of the comparative example under 0.1C charge and discharge conditions. Figure 15 The capacity and coulombic efficiency of the battery made of LMR-BURNT in Example 1 under 0.1C charge and discharge conditions in the first three cycles are Figure 16 The capacity and coulombic efficiency of the battery made of LMR-BURNT in the first three cycles under 0.1C charge and discharge conditions are as follows: Figure 17 .

[0109] Depend on Figures 2 to 9 It can be seen that compared with the LMR of the comparative example, the matrix porosity of the LMR-BURNT of Example 1 is increased, and the increase in porosity helps to increase the contact area between the lithium-rich manganese-based positive electrode material and the electrolyte, improve the wetting effect and thus increase the lithium ion transmission rate.

[0110] Depend on Figure 10 and Figure 12 It can be seen that Ni enrichment occurs on the surface of the LMR-BURNT of Example 1, while Ni enrichment does not occur on the surface of the LMR of the comparative example.

[0111] Depend on Figure 11 and Figure 13 It can be seen that Ni enrichment occurs at the LMR-BURNT grain boundaries of Example 1, while Ni enrichment does not occur at the LMR grain boundaries of the comparative example.

[0112] Depend on Figure 14 It can be seen that compared with the LMR of the comparative example, the LMR-BURNT of Example 1 has peaks of Ni6MnO8 and Li2MnO3 in the XRD data, which proves that after treatment, the example forms a structure of lithium-rich manganese-based positive electrode material different from that of the comparative example.

[0113] Depend on Figure 15 It can be seen that compared with the LMR in the comparative example, the specific capacity shows a trend of gradual attenuation during the cycle; while the LMR-BURNT of Example 1 requires a longer activation time due to the presence of a transition metal oxide layer, but shows excellent cycle stability and capacity retention in subsequent cycles.

[0114] Depend on Figure 16-17 It can be seen that compared with the LMR of the comparative example, the LMR-BURNT of Example 1 requires more activation cycles to release capacity due to the presence of a transition metal oxide layer on the surface. The reason is that the dense transition metal oxide layer blocks the transmission of lithium ions, resulting in the inability to exert the capacity of the material. In subsequent cycles, due to the gradual formation of lithium ion transmission channels, the discharge specific capacity of the material is gradually improved, and the capacity retention rate is maintained at a certain level to maintain a relatively stable level.

[0115] The above is a detailed introduction to the lithium-rich manganese-based positive electrode material and its preparation method provided in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a lithium-rich manganese-based positive electrode material, characterized in that: The steps include: Dissolving a soluble lithium salt, a soluble nickel salt, and a soluble manganese salt in water, and then adding a first organic solvent to obtain a mixed solution; dissolving oxalic acid in a second organic solvent to obtain an oxalic acid solution; adding the mixed solution to the oxalic acid solution, co-precipitating, and drying to obtain a lithium-rich manganese oxalate precursor; Calcination: heating the lithium-rich manganese oxalate precursor to 350-550° C. at a heating rate V1 and maintaining the temperature to obtain a lithium-rich manganese-based material; Over-firing: heating the lithium-rich manganese-based material to 900-1000° C. at a heating rate V2 and maintaining the temperature to form a transition metal oxide layer with cation vacancies on the surface of the lithium-rich manganese-based material, thereby obtaining a lithium-rich manganese-based positive electrode material; The molar ratio of the soluble lithium salt, the soluble nickel salt, the soluble manganese salt and the oxalic acid is in the range of (1.2-1.3):0.2:0.6:1; The transition metal oxide with cation vacancies is Ni6MnO8; The first organic solvent is selected from at least one of ethanol, isopropanol and polyols; the second organic solvent is selected from at least one of ethanol, isopropanol and polyols.

2. The preparation method according to claim 1, wherein: The soluble lithium salt is selected from at least one of lithium acetate, lithium carbonate, lithium nitrate, lithium sulfate and lithium chloride; and / or The soluble nickel salt is selected from at least one of nickel acetate, nickel sulfate, nickel nitrate, nickel chloride and nickel bromide; and / or The soluble manganese salt is at least one selected from manganese acetate, manganese sulfate, manganese nitrate, manganese chloride and manganese bromide.

3. The preparation method according to claim 1, wherein: The heating rate V1 is in the range of 1.2-5°C / min; and / or The range of the heating rate V2 is 1.2-5°C / min.

4. The preparation method according to claim 1, wherein: The thickness of the transition metal oxide layer is in the range of 2-10 nm.

5. A lithium-rich manganese-based material, characterized in that: The lithium-rich manganese-based material is prepared by the preparation method according to any one of claims 1 to 4.

6. An electrode sheet, characterized in that: The electrode sheet comprises the lithium-rich manganese-based material according to claim 5.

7. A battery, characterized in that: The battery comprises the electrode sheet according to claim 6.

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