A surface-modified lithium-rich manganese oxide material, and a preparation method and application thereof

Abstract

The application relates to a surface-modified lithium-rich manganese oxide material and a preparation method and application thereof, and belongs to the technical field of lithium ion battery cathode materials. The material comprises a layered lithium-rich manganese oxide base material and a layered spinel heterostructure uniformly distributed on the surface of the lithium-rich manganese oxide base material; the spinel heterojunction is one or both of LiMn2O4 and Li4Mn5O 12 , and the thickness is 5nm-10nm; the surface of the modified lithium-rich manganese oxide material also contains an oxygen vacancy structure. Thanks to the existence of the heterostructure and the oxygen vacancy structure, the material disclosed by the application has high capacity and rate performance; the release of oxygen, interface side reactions and the irreversible phase transition of the layered phase-spinel phase-rock salt phase are all inhibited in the electrochemical cycle process. The lithium ion battery assembled by using the material as a cathode has high first-cycle coulomb efficiency, and the capacity attenuation problem in the cycle is also alleviated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery material preparation, and particularly relates to preparation and application of surface-modified lithium-rich manganese oxide material. BACKGROUND

[0002] Lithium ion batteries are widely used in 3C mobile intelligent terminals, electric vehicles and energy storage fields due to their high working voltage, small size, long cycle life, high energy density and low self-discharge. In recent years, in order to meet the requirements of long-range electric vehicles, it is predicted that the energy density of battery monomer needs to reach 350 Wh / kg by 2025, and the energy density of lithium ion batteries mainly depends on the positive electrode material. Therefore, the development of positive electrode materials with high energy density has become the focus of attention. Lithium-rich manganese-based layered oxides with high discharge specific capacity, high working voltage and low cost gradually come into people's field of vision, and the typical layered lithium-rich manganese oxide positive electrode material is basically composed of xLi2MnO3·(1-x)LiMO2, M is selected from a mixture of transition metals (TMs) such as Ni, Mn and Co, which is considered to be a new generation of positive electrode material with great development prospects.

[0003] However, the lithium-rich manganese oxide positive electrode material also has some problems, including low first coulomb efficiency, capacity and voltage decay during the cycle process, which greatly limits its commercial application. In addition, the Li2MnO3 phase has low electronic conductivity, so it also has the problem of poor rate performance.

[0004] The current common improvement strategies mainly include: 1. Physical coating of lithium-rich oxide positive electrode material, such as coating oxides such as ZrO2 and fluorides such as AlF3 to prevent side reactions; 2. Gradient structure design, gradient design of each element in the material to inhibit oxygen release and transition metal ion dissolution; 3. Element doping occupies Li / TM / O lattice sites to stabilize the structure and inhibit phase change; 4. Constructing oxygen vacancy defects, reducing the electronic density of surface O 2p state, and relieving the irreversible release of surface oxygen.

[0005] Considering that the current single modification method still cannot fundamentally solve the problems faced by lithium-rich oxide positive electrode materials, it is necessary to adopt a method combining multiple modification methods. It is extremely necessary to use a simple and efficient method to comprehensively improve the electrochemical performance of lithium-rich manganese oxide positive electrode materials for the commercial application of high-capacity lithium-rich manganese oxide materials. SUMMARY

[0006] To address the shortcomings of the existing technology, this invention provides a surface-modified lithium-rich manganese oxide material and its preparation method, thus solving the problems in the prior art. Benefiting from the presence of heterostructure and oxygen vacancy structure, the material disclosed in this invention exhibits excellent cycling performance; oxygen release, interfacial side reactions, and irreversible phase transitions between the layered phase, spinel phase, and rock salt phase are suppressed during electrochemical cycling. Lithium-ion batteries assembled from electrodes prepared using this material exhibit high first-cycle coulombic efficiency and excellent capacity retention.

[0007] The specific implementation plan is as follows:

[0008] A surface-modified lithium-rich manganese oxide material is characterized in that the material comprises a layered lithium-rich manganese oxide substrate, a layered spinel heterostructure uniformly distributed on the surface of the lithium-rich manganese oxide substrate, and an oxygen vacancy structure on the surface; the general structural formula of the layered lithium-rich manganese oxide substrate is xLi2MnO3·(1-x)LiMO2, where M is selected from one or more of Ni, Mn, Co, Cr, Fe, and Al, and 0≤x≤1; the particle size of the layered lithium-rich manganese oxide substrate is 1μm~15μm.

[0009] The spinel structure in the layered spinel heterostructure is LiMn2O4 or Li4Mn5O4. 12 One or two of these structures share a common oxygen lattice framework with the lithium-rich manganese oxide substrate, and are tightly bonded.

[0010] The thickness of the layered spinel heterostructure is 5 nm to 10 nm.

[0011] The oxygen vacancy structure on the surface is located at a depth of 5 nm to 10 nm from the surface.

[0012] The present invention also discloses a method for preparing the surface-modified lithium-rich manganese oxide material, as follows:

[0013] Step 1: Immerse the lithium-rich manganese oxide substrate in an organic weak acid solution for thorough wetting, and then separate it;

[0014] Step 2: Annealing is performed in an inert atmosphere to obtain a modified lithium-rich oxide material that has both a layered spinel heterostructure and surface oxygen vacancies.

[0015] The concentration of the organic weak acid solution is 0.05 mol / L to 0.15 mol / L, the solvent is 95 wt% ethanol, and the volume of the solution used is 60 ml to 100 ml; the lithium-rich manganese oxide substrate is immersed in the above organic weak acid treatment solution for 0.5 h to 1 h, and then separated by vacuum filtration.

[0016] The heating rate during the annealing process is 3℃ / min, the annealing temperature is 500℃, the holding time is 5h, and the working atmosphere is either argon or nitrogen.

[0017] The preparation method disclosed in this invention uses layered lithium-rich manganese oxide substrate as raw material and performs post-treatment with an organic weak acid solution (sorbic acid, salicylic acid, etc.). During the treatment process, the raw material can react with the weak acid solution to form H+. + / Li + Ion exchange occurs, forming lithium vacancies, while some organic molecules adsorb onto the substrate surface. During the annealing process, the lithium vacancies formed on the surface undergo atomic rearrangement, and transition metal ions occupy the sites of the lithium vacancies, thus forming a layered spinel heterostructure. This structure exhibits excellent ionic conductivity, which can improve the rate performance of the material. Furthermore, since the annealing is performed under an inert atmosphere, the weak acid molecules adsorbed on the substrate surface extract some of the lattice oxygen on the substrate surface during oxidation, thereby forming oxygen vacancies. The construction of the surface oxygen vacancy structure reduces the electron density of the O 2p state, thereby suppressing irreversible precipitation of surface lattice oxygen and improving cycle stability. Compared to pure solid-phase interfacial reactions, this treatment method is carried out in solution, resulting in a more thorough treatment effect, thus producing a more uniform layered spinel heterostructure and surface oxygen vacancies.

[0018] Preferably, the lithium-rich manganese oxide substrate in the embodiments of the present invention has the chemical formula Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, with a particle size D50 of 10 μm.

[0019] Experiments revealed that, in the preparation method of this invention, the thickness of the layered spinel heterostructure and the depth of surface oxygen vacancies can be controlled by adjusting the concentration of the organic weak acid solution. In the surface-modified lithium-rich manganese oxide material obtained using the above preparation method, the thickness of the layered spinel heterostructure is 5 nm to 10 nm; and the depth of the surface oxygen vacancies is 5 nm to 10 nm.

[0020] More preferably, in the preparation method of the lithium-rich manganese oxide material with surface modification treatment described above, the organic weak acid in step 1 is either sorbic acid or salicylic acid, and the volume of the weak acid solution is 60 ml to 100 ml.

[0021] More preferably, in the preparation method of the lithium-rich manganese oxide material with the above-described surface modification treatment, the immersion treatment time in step 1 is 0.5h to 1h.

[0022] Further preferably, the preparation method of the surface-modified lithium-rich manganese oxide material, the input amount of the lithium-rich manganese oxide material in step 1 is 0.5 g.

[0023] Further preferably, the preparation method of the surface-modified lithium-rich manganese oxide material, the separation in step 1 is vacuum filtration, and the lithium-rich manganese oxide material is washed with deionized water and ethanol alternately for 3-5 times.

[0024] Further preferably, the preparation method of the surface-modified lithium-rich manganese oxide material, the annealing treatment in step 2 is performed at a heating rate of 3 ℃ / min, an annealing temperature of 500 ℃, and an annealing time of 5 h, and the working atmosphere is one of argon and nitrogen.

[0025] By controlling the above parameters, the thickness of the layered spinel heterostructure and the depth of the surface oxygen vacancy structure of the finally prepared lithium-rich manganese oxide material can be controlled, and with the continuous optimization of the above process parameters, the electrochemical performance of the finally prepared product is continuously optimized.

[0026] The application further discloses application of the surface-modified lithium-rich manganese oxide positive electrode material in lithium ion batteries, and the lithium ion batteries are obtained by assembling positive electrode sheets prepared from the surface-modified lithium-rich manganese oxide positive electrode material, and the batteries have high first-cycle coulombic efficiency and excellent cycle stability.

[0027] Compared with the existing lithium-rich manganese oxide material, the application has the following advantages and progress:

[0028] The application uses an organic weak acid solution to perform surface modification treatment on the lithium-rich manganese oxide material, and the modified lithium-rich manganese oxide positive electrode material prepared has a 5-10 nm thick layered spinel heterostructure and a surface oxygen vacancy structure. Compared with solid-solid interface modification treatment, liquid-solid interface modification treatment has the advantages of being more sufficient and more uniform. Benefiting from the layered spinel heterostructure and the surface oxygen vacancy, the surface-modified lithium-rich manganese oxide positive electrode material has less oxygen release and interface side reaction during long-term electrochemical cycling, and the structural stability of the lithium-rich manganese oxide matrix material during the cycle process is improved. The spinel heterojunction and the bulk layered structure share the lattice oxygen framework, and the combination is very close, which is conducive to improving the cycle stability of the material, inhibiting the dissolution of transition metal ions and the irreversible conversion of the layered phase to the rock salt phase, and inhibiting the rapid decay of the voltage and capacity of the lithium-rich manganese oxide material. In addition, the construction of the surface oxygen vacancy reduces the electron density of O 2p on the material surface, greatly inhibits the oxygen release during the first cycle, and improves the first-cycle coulombic efficiency and the reversibility of the lattice oxygen redox during the cycle process.

[0029] The preparation method discloses in the application takes layered lithium-rich manganese oxide material as a base material and takes organic weak acid solution as a treatment liquid. Compared with solid-solid interface modification, liquid-solid interface modification can make the surface of the lithium-rich manganese oxide base material react more fully, and the generated spinel heterostructure and oxygen vacancy structure of the surface layer are more uniform. The preparation method is simple, controllable and can be used for large-scale preparation.

[0030] The lithium ion battery assembled by the positive electrode sheet prepared from the surface-modified lithium-rich manganese oxide positive electrode material prepared in the application has high initial coulomb efficiency and excellent cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Fig. 1 is a SEM image of a surface-modified lithium-rich manganese oxide material prepared in Example 1 of the application at different magnifications;

[0032] Figure 2 Fig. 2 is an XRD image of a surface-modified lithium-rich manganese oxide material prepared in Example 1 of the application;

[0033] Figure 3 Fig. 3 is an HRTEM (a) and TEM-EDS (b) of a surface-modified lithium-rich manganese oxide material prepared in Example 1 of the application;

[0034] Figure 4 Fig. 4 is an atomic-scale HADDF-STEM image (a) and corresponding O and Mn element EELS spectra (b) of a surface-modified lithium-rich manganese oxide material prepared in Example 1 of the application;

[0035] Figure 5 Fig. 5 is an Mn2p XPS spectrum of a surface-modified lithium-rich manganese oxide material prepared in Example 1 of the application;

[0036] Figure 6 Fig. 6 is a first cycle charge-discharge curve (a) of a battery assembled from the surface-modified lithium-rich manganese oxide material in Example 1 at 0.1C (1C=200mA / g) and a cycle performance curve (b) at 0.1C current density;

[0037] Figure 7 Fig. 7 is a SEM image of a lithium-rich manganese oxide material prepared in Comparative Example 1 at different magnifications;

[0038] Figure 8 Fig. 8 is an XRD image of a lithium-rich manganese oxide material prepared in Comparative Example 1;

[0039] Figure 9 Fig. 9 is an HRTEM (a) and TEM-EDS (b) of a lithium-rich manganese oxide material prepared in Comparative Example 1;

[0040] Figure 10 is an atomic scale HADDF-STEM image (a) and corresponding EELS spectra of O and Mn elements (b) of the lithium-rich manganese oxide material prepared in Comparative Example 1;

[0041] Figure 11 is an XPS energy spectrum of Mn 2p of the lithium-rich manganese oxide material prepared in Comparative Example 1;

[0042] Figure 12 is the first cycle charge-discharge curve (a) and the cycle performance curve (b) at 0.1C current density of the battery assembled by using the lithium-rich manganese oxide material prepared in Comparative Example 1;

[0043] Figure 13 is the cycle performance curve at 1C rate of the battery assembled by using the lithium-rich manganese oxide materials prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0044] The application will be further described below in conjunction with specific examples and drawings. It should be noted that the specific implementation methods described herein are only for the purpose of illustrating and explaining the application, and are not used to limit the protection scope of the application.

[0045] Example 1:

[0046] Step (1): A lithium-rich manganese oxide cathode material is prepared by using a conventional co-precipitation method to synthesize a precursor material, and then combining a high-temperature sintering method. Specifically, the sulfate salts of Mn, Ni and Co are dissolved in deionized water in a proportion of stoichiometric numbers to form a 2 mol / L metal ion solution A. Then a mixed solution B of 2.1 mol / L Na2CO3 and 0.2 mol / L ammonia water is prepared. 200 ml of deionized water is added as a bottom liquid in a co-precipitation reactor, the water bath is kept at 55°C, and argon gas is introduced for inert protection. The pump-in speed of the A solution and the B solution is adjusted, the pH during the reaction process is monitored by a pH meter, and is kept at about 7.7-7.8. After 12 h of reaction, the mother liquor is discharged, the precipitate is left to stand, and then washed 2-3 times to obtain the precursor material;

[0047] Step (2): The precursor material obtained in step (1) is mixed with a certain amount of Li2CO3 according to the stoichiometric ratio, pre-sintered at 500°C for 5 h, and then sintered at 800°C for 12 h to obtain a lithium-rich manganese oxide material with a composition of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, and a particle size of about 10 μm;

[0048] Step (3): The above obtained lithium-rich manganese oxide material (0.5 g) was put into 0.1 mol / L sorbic acid solution (60 ml) and stirred magnetically for 0.5 h, then vacuum filtered and washed with deionized water and ethanol alternately for 3-5 times. The filtered material was dried and then annealed at 500 °C for 5 h in argon atmosphere to obtain the final surface-modified lithium-rich manganese oxide material.

[0049] Figure 1 The SEM image of the surface-modified lithium-rich manganese oxide cathode material prepared in this example shows that the morphology of the treated material particles remains very complete. It is a kind of spherical secondary particles assembled by a large number of primary particles, with a size of about 10 μm.

[0050] Figure 2 The XRD spectrum of the surface-modified lithium-rich manganese oxide cathode material prepared in this example shows that the diffraction peaks of the prepared lithium-rich manganese oxide cathode material are sharp, with good crystallinity, and exhibit the characteristic peaks of the typical layered α-NaFeO2structure. The weak diffraction peaks between 2θ = 20-25° belong to the Li2MnO3phase of the C2 / m space group.

[0051] Figure 3 The HRTEM (a) and TEM-EDS (b) of the surface-modified lithium-rich manganese oxide cathode material prepared in this example. From the lattice fringe spacing of the (a) figure and the selected electron diffraction plane calibration, the modified material still maintains the layered phase (A area) inside, and a 10 nm thick spinel structure (B area) is formed on the surface of the layered phase matrix. In addition, EDS spectrum analysis was performed on the surface-modified lithium-rich manganese oxide cathode material prepared in this example. The results show that the elements Mn, Ni, Co, O, etc. are uniformly distributed in the treated material.

[0052] Figure 4 The atomic-scale HADDF-STEM (a) image and the corresponding O and Mn element EELS spectra (b) of the surface-modified lithium-rich manganese oxide material prepared in this example. Figure a shows that the surface region of the modified material is composed of two structures, including the typical layered structure of the bulk phase and the about 10 nm thick surface spinel heterostructure. The two structures share the oxygen lattice framework and are combined very closely, which ensures the stability and reliability during long-term cycling. The EELS test results also show that the pre-edge peak intensity of O gradually increases from the surface to the bulk phase, and the L3 edge peak of Mn gradually shifts to high energy. However, the range of change is about 5 nm from the surface, which also shows that there are some oxygen vacancies in this range, and further affect the valence state of the Mn element.

[0053] Figure 5 XPS spectra of Mn 2p(a) and Mn 3s(b) of the surface-modified lithium-rich manganese oxide material prepared in this example. Compared with the Mn 2p spectrum of Comparative Example 1 in Figure 12 Compared with the Mn 2p spectrum of Comparative Example 1 in

[0054] Performance test:

[0055] The surface-modified lithium-rich manganese oxide positive electrode material prepared in this example was fully ground with SuperP conductive agent and PVDF binder in a mass ratio of 8:1:1, then a certain volume of solvent NMP was added and stirred to mix uniformly, and then coated on an aluminum foil current collector, vacuum dried at 120°C for 12h to obtain a positive electrode sheet. A 2032 button cell was used, with a lithium metal sheet as the reference electrode and counter electrode, and a Celgard-2400 separator was used to assemble the cell in a glove box. The electrolyte was LiPF6(1.15mol / L) / EC+DMC+EMC (volume ratio of 1:2:2). The test voltage window was 2.0-4.8V, and the battery was subjected to electrochemical performance testing in a constant current charge-discharge mode.

[0056] Figure 6 Electrochemical performance of the battery assembled in this example, (a) is the first cycle charge-discharge curve of the battery at a current density of 0.1C, and the first cycle coulombic efficiency can reach 88.3%, and the reversible capacity of the first cycle is 314.5mAh / g. (b) is the cycle performance curve of the battery at a current density of 0.1C, and after 100 cycles, the battery still has a discharge capacity of 276.9mAh / g, and the capacity retention rate is 88.2%.

[0057] Comparative Example 1

[0058] Steps (1) and (2) are exactly the same as in Example 1, and a lithium-rich manganese oxide positive electrode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0059] Figure 7 SEM image of the lithium-rich manganese oxide positive electrode material prepared in this comparative example, which is basically consistent with the morphology observed in Example 1, and the particle size is about 10μm.

[0060] Figure 8 XRD spectrum of the lithium-rich manganese oxide positive electrode material prepared in this comparative example, which also shows a good layered structure and has a very strong crystallinity.

[0061] Figure 9 HRTEM (a) and TEM-EDS (b) of the lithium-rich manganese oxide positive electrode material prepared for the present comparative example. From the lattice fringe spacing of the (a) figure, the material inside and the surface layer maintain the typical layered phase. In addition, EDS energy spectrum analysis was performed on the lithium-rich manganese oxide positive electrode material prepared for the present comparative example. The results show that the elements Mn, Ni, Co, O and the like in the material are uniformly distributed.

[0062] Figure 10 HADDF-STEM image (a) at the atomic scale and the corresponding EELS spectra (b) of O and Mn elements of the lithium-rich manganese oxide positive electrode material prepared for the present comparative example. Figure a shows that the material of the present example is a typical layered structure. From the test results of EELS, the pre-edge peak intensity of O from the surface to the bulk phase and the position of the L3 edge peak of Mn do not change substantially, which indicates that the composition structure and composition of the material are uniform and consistent.

[0063] Figure 11 XPS energy spectrum of Mn 2p (a) and Mn 3s (b) of the lithium-rich manganese oxide positive electrode material prepared for the present comparative example. Compared with the Mn 2p spectrum of the material of Example 1 in Figure 5 Compared with the Mn 2p spectrum of Example 1, the binding energy of each peak of the Mn 2p spectrum of the lithium-rich manganese oxide material of the present comparative example is higher, indicating that the valence state of Mn is higher than that of the material of Example 1.

[0064] The same method as Example 1 was used to assemble test batteries and test their electrochemical performance.

[0065] Figure 12 The electrochemical performance of the battery assembled for the lithium-rich manganese oxide positive electrode material prepared for the present comparative example, (a) figure is the first cycle charge-discharge curve of the battery at a current density of 0.1C, and the first cycle coulombic efficiency can reach 78.3%, and the reversible capacity of the first cycle is 270.1 mAh / g. (b) figure is the cycle performance curve of the battery at a current density of 0.1C, and after 100 cycles, the battery has a discharge capacity of 190 mAh / g, and the capacity retention rate is 70.2%.

[0066] Figure 13 is the cycle performance curve of the battery assembled from the lithium-rich manganese oxide material prepared in Example 1 and Comparative Example 1 at a rate of 1C. The test results show that the discharge specific capacity of the material of Example 1 after 150 cycles is 207.5 mAh / g, and the capacity retention rate reaches 87.91%. While the capacity of the material of Comparative Example 1 after cycling is only 160.7 mAh / g, and the retention rate is 78.4%. Therefore, due to the multifunctional interface layer of the spinel heterojunction and oxygen vacancy structure obtained by the modification treatment of sorbic acid solution, the cycle stability of the material of Example 1 is greatly improved.

[0067] In summary, the present application uses organic weak acid sorbic acid solution to perform surface modification treatment on the lithium-rich manganese oxide positive electrode material, which is an effective method for improving the comprehensive electrochemical performance of the lithium-rich manganese oxide positive electrode material. The concentration of the sorbic acid solution and the treatment time will affect the heterostructure and the thickness of the oxygen vacancy, and will also have different effects on the performance. The concentration and time of the treatment solution need to be regulated. According to the above examples, the present application can be well implemented. It needs to be further explained that the examples of the present application do not cover all the selected combinations in the technical solutions. For the materials, amount, process conditions and the like involved in the technical solutions, as long as they are within the technical solutions of the present application, they are the same as the results of the embodiments of the present application. At the same time, the embodiments of the present application are not used to limit the protection scope of the present application. Any obvious adjustment and modification of the technical solutions of the present application which belongs to the technical concept of the present application should also belong to the protection scope of the present application.

Claims

1. A method for producing a surface-modified, lithium-rich manganese oxide material, characterized by, The material comprises a layered lithium-rich manganese oxide substrate, a layered spinel heterostructure uniformly distributed on the surface of the lithium-rich manganese oxide substrate, and a surface oxygen vacancy structure; The layered lithium-rich manganese oxide substrate has a general structure of xLi2MnO3·(1-x)LiMO2, M is selected from one or more of Ni, Mn, Co, Cr, Fe, and Al, and 0≤x≤1; The spinel structure in the described layered spinel heterostructure is LiMn2O4 or Li4Mn5O4. 12 One or two of them, the structure and the lithium-rich manganese oxide substrate share the same oxygen lattice framework and are tightly bonded; The particle size of the layered lithium-rich manganese oxide substrate is 1 μm-15 μm; The method comprises the following steps: Step (1): the lithium-rich manganese oxide substrate is immersed in an organic weak acid solution for sufficient soaking treatment, and then separated; Step (2): the material separated in step (1) is annealed in an inert atmosphere to obtain a modified lithium-rich manganese oxide material with a layered spinel heterostructure and a surface oxygen vacancy structure; In step (1), the organic weak acid solution is sorbic acid.

2. The method of producing a surface-modified, lithium-rich manganese oxide material according to claim 1, wherein The thickness of the layered spinel heterostructure is 5 nm-10 nm, and the thickness of the surface oxygen vacancy structure is 5 nm-10 nm.

3. The method of claim 1, wherein the surface-modified, lithium-rich manganese oxide material is prepared by a method comprising: a) providing a lithium-rich manganese oxide material; b) contacting the lithium-rich manganese oxide material with a solution comprising a transition metal salt; and c) drying the lithium-rich manganese oxide material. The soaking treatment time in step (1) is 0.5 h-1 h.

4. The method of claim 1, wherein the surface-modified, lithium-rich manganese oxide material is prepared by a method comprising: providing a lithium-rich manganese oxide material; and contacting the lithium-rich manganese oxide material with a surface modification agent. The separation mode in step (1) is vacuum filtration, and the material is washed with deionized water and ethanol alternately for 3-5 times.

5. The method of claim 1, wherein the surface-modified, lithium-rich manganese oxide material is prepared by a method comprising: a) providing a lithium-rich manganese oxide material; b) contacting the lithium-rich manganese oxide material with a solution comprising a transition metal salt; and c) drying the lithium-rich manganese oxide material. In step (1), the concentration of the organic weak acid is 0.05 mol / L-0.15 mol / L, the solvent is 95 wt% ethanol, and the volume of the solution used is 60 ml-100 ml.

6. The method of claim 1, wherein the surface-modified, lithium-rich manganese oxide material is prepared by a method comprising: a) providing a lithium-rich manganese oxide material; b) contacting the lithium-rich manganese oxide material with a solution comprising a transition metal salt; and c) drying the lithium-rich manganese oxide material. In step (2), the heating rate during the annealing process is 3℃ / min, the annealing temperature is 500℃, and the holding time is 5 h.

7. The method of claim 1, wherein the surface-modified, lithium-rich manganese oxide material is prepared by a method comprising: a) providing a lithium-rich manganese oxide material; b) contacting the lithium-rich manganese oxide material with a solution comprising a transition metal salt; and c) drying the lithium-rich manganese oxide material. The inert atmosphere in step (2) is one of argon or nitrogen.

8. Application of the surface-modified lithium-rich manganese oxide material prepared by the method of any one of claims 1-7 in lithium ion batteries.

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