Surface titanium coated and modified lithium nickel manganese oxide positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a surface titanium coated and modified lithium nickel manganese oxide positive electrode material, a preparation method and application. The invention discloses a preparation process of lithium nickel manganese oxide positive electrode powder with uniformly distributed nickel and manganese elements, elements are kept uniformly distributed in a solution, and the obtained powder is dispersed by ball milling, so that element segregation in the lithium nickel manganese oxide positive electrode powder is further inhibited; the titanium coating treatment improves the conductivity and ionic conductivity of the lithium nickel manganese oxide powder at the same time, so that the charge-discharge and rate capability of the button battery is improved. The preparation method disclosed by the invention has general applicability and can be applied to positive electrode materials such as lithium nickel manganese oxide and lithium nickel cobalt manganese oxide, so that the conductivity and the ion transmission performance of the positive electrode materials are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and particularly relates to a lithium nickel manganate cathode material with surface titanium coating modification, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries have become indispensable energy conversion devices in human life. With the high-performance development of power batteries and 3C products, the requirement for high energy density of lithium-ion batteries has become the driving force for the research and development of cathode materials. Compared with commercial lithium iron phosphate and ternary cathode lithium batteries, the spinel-structured LiNi 0.5 Mn 1.5 O4 cathode (LNMO) is considered as the preferred research object for the cathode material of the next-generation high-energy-density lithium battery due to its advantages of high working voltage (4.7V), cobalt-free and low cost. Nevertheless, the lithium nickel manganate cathode has a spinel structure similar to that of lithium manganate, and the Jahn-Teller effect of manganese element and the resulting lattice distortion, the dissolution of nickel and manganese in the electrolyte, etc. all affect its application performance.

[0003] In order to expand the application scenarios of the spinel-structured LiNi 0.5 Mn 1.5 O4 cathode and overcome defects such as manganese dissolution, in recent years, a variety of different improvement methods have been applied to the preparation process of lithium nickel manganate cathode powder. Chinese Patent CN113178566B discloses a method for preparing lithium nickel manganate cathode material powder by coprecipitation; Chinese Patent CN103337621B discloses a method for preparing copper oxide-coated lithium nickel manganate cathode material powder; while Chinese Patent CN117699863A discloses a method for preparing a yttrium-doped lithium nickel manganate precursor by coprecipitation. In order to improve the surface stability of the obtained powder, the surface of the obtained powder also needs to be coated with nickel phosphate and manganese phosphate for the second time; however, due to the poor activity of metal oxide materials such as CuO in the coating layer on the surface of the lithium nickel manganate cathode material, the low ionic conductivity leads to an increase in the interfacial impedance during the cycling process, thereby resulting in a decrease in the discharge capacity and cycling stability of the lithium battery; in addition, due to the poor conductivity of phosphate, carbon coating is also required to improve the conductivity of the cathode material. Despite the above methods, the cycling stability, capacity and rate performance of the spinel-structured lithium nickel manganate cathode still need to be solved urgently. Therefore, a preparation method of a lithium nickel manganate cathode material with good conductivity and high structural stability is needed to solve the above technical problems. Summary of the Invention

[0004] In view of this, the present invention discloses a preparation method of a lithium nickel manganese oxide cathode material modified by surface titanium coating with uniform distribution of nickel and manganese elements. The lithium nickel manganese oxide powder obtained through a series of treatments of the present invention has stable electrochemical performance, synchronous improvement of ionic conduction and electronic conductivity on the surface of the cathode powder particles, stable cycle performance of the assembled lithium nickel manganese oxide button battery, and excellent rate performance.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The first technical object of the present invention is to provide a preparation method of a lithium nickel manganese oxide cathode material modified by surface titanium coating. First, nickel nitrate and manganese nitrate are mixed in a certain proportion and fully stirred and dissolved in a water bath with deionized water to obtain a uniformly mixed nickel manganese nitrate solution; the previously prepared PVA solution is added to the nickel manganese nitrate solution, and hydrothermally stirred until completely dissolved to form a uniformly high-density colloidal solution. Then, the solution is placed in a vacuum drying oven to be dried to obtain a colloidal viscous substance; the colloidal substance is carbonized in a muffle furnace to obtain a precursor powder, and then a lithium source is mixed in, and after sufficient grinding, it is sintered in a tube furnace; the black powder obtained by sintering is subjected to secondary ball milling, and the milled powder is then coated with a titanium-containing solution on the surface and heat-treated; the powder after heat treatment of the above processes is ground and mixed with a lithium source to replenish lithium, and after high-temperature calcination, a lithium nickel manganese oxide cathode material powder is prepared.

[0007] It should be noted that the lithium nickel manganese oxide cathode powder obtained through the present invention has good electrochemical performance and simultaneously shows high conductivity and ionic conductivity. This treatment process can improve the density, conductivity and ionic conduction performance of the cathode material, and the surface titanium doping modification improves the corrosion resistance of the cathode powder to the electrolyte, thereby improving the service life and charge-discharge performance of the battery.

[0008] Specifically, the preparation method of the lithium nickel manganese oxide cathode material modified by surface titanium coating includes the following steps:

[0009] Step 1: Form a uniformly high-viscosity solution using nickel nitrate, manganese nitrate and PVA solution

[0010] Prepare a mixture of Ni(NO3)2·6H2O and Mn(NO3)2·4H2O according to a molar ratio of Ni / Mn of 1:3 and dissolve it in 20 mL of deionized water, and then gradually add 20 mL of PVA solution, and heat and stir until the solution becomes colloidal;

[0011] It should be noted that adding a PVA solution with a certain viscosity to the nickel and manganese salt mixed solution maintains the uniform distribution of nickel and manganese elements in the solution, especially inhibits the segregation of nickel and manganese during the drying process of the solution.

[0012] Step 2: After drying the colloid obtained in step 1, LiOH·H2O in an amount having a molar ratio of Li / (Ni+Mn) not higher than a theoretical ratio of 1:2 is added, the mixture is fully ground and calcined to obtain a lithium nickel manganese oxide precursor powder; by controlling the amount of lithium added, the subsequent reaction activity of the lithium nickel manganese oxide precursor powder is ensured;

[0013] Step 3: Ball milling and titanium coating of lithium nickel manganese oxide precursor powder

[0014] The lithium nickel manganese oxide precursor powder is ball milled by high-energy ball milling to form more crystal defects in the lithium nickel manganese oxide positive electrode powder, and the powder is then coated with a titanium-containing solution and heat treated;

[0015] It should be noted that the lithium nickel manganese oxide precursor powder is amorphized by high-energy ball milling. While ensuring the uniform distribution of elements, the reaction activity of the titanium coating treatment on the powder surface is further increased, so as to facilitate the uniform diffusion of titanium elements in the lithium nickel manganese oxide powder, forming lithium nickel manganese oxide powder uniformly doped with titanium.

[0016] Step 4: Perform lithium supplementation treatment on the lithium nickel manganese oxide precursor powder after titanium coating treatment

[0017] The powder obtained in step 3 is added with a certain amount of lithium source compound for lithium replenishment and mixed, and calcined to finally obtain lithium nickel manganese oxide positive electrode material powder; the surface state of the lithium nickel manganese oxide powder particles can be modified by secondary lithium replenishment.

[0018] Preferably, in step 1, a beaker containing a mixture of Ni(NO3)2-6H2O and Mn(NO3)2-4H2O is placed in a water bath, and 20 mL of a 1788 PVA solution having a concentration of 2 to 10% is gradually added, heated and stirred, and the water bath temperature is 30 to 80°C;

[0019] In step 2, the solution is heated and stirred until it becomes a gel, and then placed in a vacuum drying oven for drying at a temperature of 100 to 150° C. for 20 to 24 hours.

[0020] Preferably, in steps 3 and 4, the high-energy ball milling time is 2 to 8 hours, the titanium coating treatment on the powder surface uses butyl titanate solution as the titanium source, the mass percentage of the titanium coating is controlled to be 2-8%, and the heat treatment after titanium coating is carried out at a heating rate of 5 to 10°C / min and a heat treatment temperature of 600 to 800°C for 2 to 3 hours; further, the powder after heat treatment is modified by lithium source lithium supplementation, and the lithium supplementation amount is the designed LiNi 0.5 Mn 1.5 The theoretical lithium content of O4 is 3-10% wt. After lithium supplementation, the calcination is heated to 900-930°C at a heating rate of 5-10°C / min, kept warm for 12 hours, and then cooled to room temperature.

[0021] The second technical object of the present invention is to provide a lithium nickel manganese oxide cathode material modified by titanium coating on the surface prepared by the above method.

[0022] It should be noted that the lithium nickel manganese oxide cathode powder prepared by the present invention has stable cycling performance and excellent rate performance after being assembled into a button battery.

[0023] Furthermore, the third technical object of the present invention is to provide a lithium battery, which uses the obtained lithium nickel manganese oxide cathode powder modified by titanium coating on the surface as the active material. The positive electrode sheet of the lithium battery is composed of an active material, a binder, and a conductive agent; the active material accounts for 80-97% of the total weight of the lithium nickel manganese oxide cathode slurry modified by titanium coating on the surface, and the conductive agent and the binder account for 3-20% of the total weight of the lithium nickel manganese oxide cathode slurry modified by titanium coating on the surface.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention discloses a preparation process of lithium nickel manganese oxide cathode powder with uniform distribution of nickel and manganese elements. The elements are kept uniformly distributed in the solution, and the obtained powder is further ball-milled and dispersed, which further inhibits the element segregation in the lithium nickel manganese oxide cathode powder; the titanium coating treatment improves the conductivity and ionic conductivity of the lithium nickel manganese oxide powder at the same time, thereby improving the charge-discharge and rate performance of the button battery.

[0026] 2. The preparation method disclosed by the present invention has general applicability and can be applied to cathode materials such as lithium nickel manganese oxide and lithium nickel cobalt manganese oxide, thereby improving the conductivity and ion transport performance of the cathode material.

[0027] 3. The preparation method of the present invention is simple to operate, the process is easy to control and the cost is low, and it is suitable for mass production. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0029] Figure 1 XRD patterns of the precursor powder, secondary ball milling and the finally obtained lithium nickel manganese oxide powder in Example 1.

[0030] Figure 2 Scanning electron microscope photos of the lithium nickel manganese oxide powder after titanium surface coating and heat treatment in Example 1.

[0031] Figure 3 SEM photograph of the lithium nickel manganese oxide cathode powder finally obtained in Example 1.

[0032] Figure 4 SEM photograph of the lithium nickel manganese oxide cathode powder finally obtained in Example 2.

[0033] Figure 5 SEM photograph of the lithium nickel manganese oxide cathode powder finally obtained in the Comparative Example.

[0034] Figure 6 Charge-discharge curves of the lithium nickel manganese oxide coin cells prepared in Example 1, Example 2 and the Comparative Example.

[0035] Figure 7 Rate performance graph of the lithium nickel manganese oxide coin cell prepared in Example 1 under the conditions of 0.1C to 5C. Detailed implementation manners

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The special term "embodiment" here, any embodiment described as "exemplary" does not have to be construed as superior to or better than other embodiments. For the performance index tests in the embodiments of the present application, unless otherwise specified, the conventional test methods in the art are adopted. It should be understood that the terms described in the present application are only for describing specific embodiments and are not used to limit the content disclosed in the present application.

[0038] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as those generally understood by those of ordinary skill in the technical field to which the present application belongs; the test methods and technical means not specifically noted in the present application are all the experimental methods and technical means generally adopted by those of ordinary skill in the art.

[0039] In order to better illustrate the content of the present application, numerous specific details are given in the following detailed embodiments. Those skilled in the art should understand that the present application can also be implemented without some specific details. In the embodiments, some methods, means, instruments, devices, etc. well known to those skilled in the art are not described in detail in order to highlight the gist of the present application.

[0040] On the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the obtained technical solutions belong to the content disclosed in the embodiments of the present application.

[0041] The present invention discloses a preparation method of a lithium nickel manganese oxide cathode material with a surface titanium coating modification.

[0042] To better understand the present invention, the following embodiments are used to further elaborate on the present invention specifically, but it should not be construed as a limitation of the present invention. For those skilled in the art, some non-essential improvements and adjustments made based on the above invention content are also considered to fall within the protection scope of the present invention.

[0043] Example 1

[0044] A preparation method of a lithium nickel manganese oxide cathode material powder specifically includes the following steps:

[0045] Step 1: A mixture of Ni(NO3)2·6H2O and Mn(NO3)2·4H2O prepared according to a molar ratio of Ni / Mn of 1:3 is dissolved in 20 mL of deionized water, and then 20 mL of a 5% PVA solution is gradually added, and the solution is heated and stirred until it becomes a high-viscosity colloid;

[0046] Step 2: After drying the colloid obtained in Step 1 at 100 °C for 24 h, LiOH·H2O close to the theoretical ratio is added, preferably adding the theoretical ratio amount with a lithium content of 95 - 105%, and more preferably adding 98% of the theoretical ratio amount of lithium, and then it is sufficiently ground and calcined at 700 °C for 3 h to obtain a lithium nickel manganese oxide precursor powder. The XRD analysis results are shown in Figure 1 the precursor spectrum;

[0047] Step 3: The above lithium nickel manganese oxide precursor powder is ball-milled for 6 hours, the selected ball-to-material ratio is 1:30, and the forward and reverse rotation speeds are both 600 r / min. The XRD analysis is used to analyze the ball-milling effect. The ideal XRD results after ball-milling are shown in Figure 1 the XRD spectrum after ball-milling in; The powder surface coating treatment uses tetrabutyl titanate solution as the titanium source, and the mass percentage content of titanium coating is controlled at 5%. After titanium coating, the powder is heated at a heating rate of 5 - 10 °C / min, held at 700 °C for 3 h, and then cooled to room temperature. The powder morphology obtained is shown in Figure 2 the scanning electron microscope photograph;

[0048] Step 4: The powder obtained in Step 3 is modified on the surface of its powder particles by the lithium source lithium supplementation method, and the lithium supplementation amount is 5% wt of the theoretical lithium content of the designed LiNi 0.5 Mn 1.5 O4. After lithium supplementation, the calcination is carried out by heating at a heating rate of 5 - 10 °C / min to 930 °C, held for 12 h, and then cooled to room temperature to obtain the final lithium nickel manganese oxide cathode powder. The powder morphology is shown in Figure 3 the scanning electron microscope photograph.

[0049] Example 2

[0050] A preparation method of lithium nickel manganese oxide cathode material powder specifically comprises the following steps:

[0051] Step 1: A mixture of Ni(NO3)2·6H2O and Mn(NO3)2·4H2O prepared according to a molar ratio of Ni / Mn of 1:3 is dissolved in 20 mL of deionized water, and then 20 mL of a 10% PVA solution is gradually added, and the mixture is heated and stirred until the solution becomes a high-viscosity colloid;

[0052] Step 2: After the colloid obtained in Step 1 is dried at 100 °C for 24 h, LiOH·H2O (100%) required by the theoretical ratio is added, and then it is sufficiently ground and calcined at 700 °C for 3 h to obtain lithium nickel manganese oxide precursor powder. The XRD analysis results are shown in the precursor pattern of Figure 1 ;

[0053] Step 3: The above lithium nickel manganese oxide precursor powder is ball-milled for 6 hours. The selected ball-to-material ratio is 1:30, and the forward and reverse rotation speeds are both 600 r / min. The ball-milling effect is analyzed by XRD. The ideal XRD results after ball-milling are shown in the XRD pattern of Figure 1 after ball-milling; The powder surface is coated with tetrabutyl titanate solution as the titanium source, and the mass percentage content of titanium coating is 8%. After titanium coating, the powder is heated at a heating rate of 5-10 °C / min, held at 700 °C for 3 h, and then cooled to room temperature. The powder morphology obtained is shown in the scanning electron microscope photograph of Figure 2 ;

[0054] Step 4: The powder obtained in Step 3 is modified by lithium source lithium supplementation to modify the surface of its powder particles. The lithium supplementation amount is 10% wt of the theoretical lithium content of the designed LiNi 0.5 Mn 1.5 O4. After lithium supplementation, the calcination is carried out at a heating rate of 5-10 °C / min to 930 °C, held for 12 h, and then cooled to room temperature to obtain the final lithium nickel manganese oxide cathode powder. The powder morphology is shown in the scanning electron microscope photograph of Figure 4 . It can be seen that there are uneven regions of residual lithium hydroxide alkali on the surface of the lithium nickel manganese oxide cathode powder.

[0055] In order to further prove the beneficial effects of the present invention and better understand the present invention, the following comparative examples are used to further clarify the technical features disclosed by the present invention, but it should not be construed as a limitation of the present invention. For other improvements made by those skilled in the art based on the above-mentioned invention content without creative work, they are also considered to fall within the protection scope of the present invention.

[0056] Comparative Example

[0057] The lithium nickel manganese oxide cathode powder is synthesized and prepared according to the steps designed as follows in the comparative example:

[0058] Step 1: Ni(NO3)2·6H2O and Mn(NO3)2·4H2O salts with a molar ratio of Ni / Mn of 1:3 were ball-milled for 8 hours to be uniformly mixed.

[0059] Step 2: The powder obtained in Step 1 was added with LiOH·H2O with a theoretical lithium content of 105% of the designed amount, and was sufficiently ground and calcined at 700 °C for 3 h to obtain lithium nickel manganate precursor powder. The powder morphology is shown in the Figure 5 scanning electron microscope image.

[0060] Test example: Assemble a button cell to test the electrochemical performance of the positive electrode.

[0061] The lithium nickel manganate positive electrode powder prepared in Example 1 was used to prepare a positive electrode sheet and assemble it into a button cell according to the following method to test the performance of the lithium nickel manganate positive electrode in Example 1.

[0062] 1 g of the lithium nickel manganate positive electrode powder synthesized in Example 1 was taken, and acetylene black and polyvinylidene fluoride binder (PVDF) were prepared according to a mass ratio of 8:1:1, and NMP solvent was added to make a slurry, which was coated on an aluminum foil to obtain a lithium nickel manganate positive electrode sheet.

[0063] The thickness of the electrode sheet was controlled to be 40 μm. The electrolyte used was a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with a volume ratio of 3:7, and LiPF6 was used as the lithium salt with a concentration of 1 mol / L; a commercial 25-μm PP separator and a 100-μm-thick lithium sheet negative electrode were selected to assemble a 2032-type button cell.

[0064] It can be seen from Figure 7 that the rate discharge performance of the lithium nickel manganate positive electrode in Example 1 is stable, and the 0.1C capacity hardly decays after 30 cycles.

[0065] Specifically, Figure 1 is the XRD comparison chart of the modified lithium nickel manganate and the original lithium nickel manganate. The XRD pattern shows that the number and diffraction angle of the X-ray diffraction peaks of the modified lithium nickel manganate positive electrode powder and the original unmodified lithium nickel manganate powder are the same, and the difference lies in the intensity of the peaks, which can be well corresponded to the diffraction indexes (111)(311)(222)(400)(331)(511)(440)(531) of LiNi 0.5 Mn 1.5 O4, and no impurity phase irrelevant to the target product is found in the pattern. In addition, the structure and properties of the lithium nickel manganate bulk material are not changed by the coating modification with titanium butoxide solution.

[0066] Combined with Figure 3 (the final positive electrode powder in Example 1),Figure 4 (Example 2 Cathode Powder) Comparison of the surface morphology and process differences of the materials. From the perspective of particle morphology, Figure 3 The particle morphology of the synthesized samples all presents a well-crystallized spinel octahedron shape, and there are obvious boundaries between the particles; while Figure 4 With the increase of the lithium compensation amount, it can be seen that the residual alkali scattered on the particle surface, the clarity of the particle surface decreases, and the particle boundary also becomes blurred.

[0067] In addition, through the analysis of the process differences between Example 1 and Example 2, it can be known that too high a coating content will lead to too thick a titanium coating layer on the particle surface, increasing the resistance of lithium ion extraction and insertion during the charge and discharge process, thus causing a decline in the performance of the lithium battery; too high a lithium compensation content will lead to the generation and deposition of irreversible by-products of excess lithium ions on the negative electrode surface during the charging process, seriously affecting the discharge capacity and cycle life of the lithium battery.

[0068] Moreover, combined with Figure 3 and Figure 4 , by analyzing Figure 5 the surface morphology of the powder, it can be known that too long a ball milling time will lead to uneven particles and particle agglomeration, which may cause a more complex SEI film at the negative electrode, reduce the reversible capacity, and be accompanied by local overcharge and over-discharge phenomena or lithium metal precipitation, forming a safety hazard; the ball milling time in Example 1 is the best, the particle morphology is evenly dispersed and there are obvious boundaries between the particles, and the battery discharge capacity presented is also the best (150 mAh / g).

[0069] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a lithium nickel manganese oxide cathode material with a surface titanium coating modification, characterized in that, First, add the PVA solution to the nickel-manganese nitrate solution to fully dissolve the nickel / manganese salts, uniformly disperse them, and form a high-viscosity solution. The obtained jelly-like substance after drying is subjected to ball milling to form more crystal defects on the surface of the lithium nickel manganese oxide cathode powder, further dispersing the originally agglomerated powder particles, and thus secondarily improving the compositional uniformity of the precursor powder. The surface of the precursor powder after lithiation treatment is doped with titanium. Secondary lithium supplementation is carried out to prepare a lithium nickel manganese oxide cathode material powder with a surface titanium-coated modification.

2. The preparation method of the lithium nickel manganese cobalt oxide cathode material with surface titanium coating modification according to claim 1, wherein, Specifically, it includes the following steps: Step 1: Dilute and stir-dissolve the nitrate compounds of the nickel source and manganese source with deionized water. Prepare a mixture of Ni(NO3)2·6H2O and Mn(NO3)2·4H2O according to a molar ratio of Ni / Mn of 1:

3. After dissolving in deionized water, gradually add a certain amount of PVA solution with a concentration of 2-10%, and heat and stir until the solution becomes jelly-like. Step 2: After drying the colloid obtained in Step 1, add a theoretical proportion of LiOH·H2O with a molar ratio of Li / (Ni + Mn) not higher than 1:2, and carry out sufficient grinding and calcination to obtain the lithium nickel manganese oxide precursor powder. Step 3: Perform ball milling and surface titanium coating treatment on the lithium nickel manganese oxide precursor powder. Carry out ball milling treatment on the lithium nickel manganese oxide precursor powder by high-energy ball milling to form more crystal defects on the surface of the lithium nickel manganese oxide cathode powder, and then coat the above powder with a titanium-containing solution and perform heat treatment. Step 4: Perform lithium supplementation treatment on the lithium nickel manganese oxide precursor powder after titanium coating treatment. Add a certain amount of lithium supplementation lithium source compound to the powder obtained in Step 3, mix them, and after calcination, finally obtain the lithium nickel manganese oxide cathode material powder.

3. The preparation method of the lithium nickel manganese oxide cathode material with surface titanium coating modification according to claim 1 or 2, characterized in that, The aqueous solutions of Ni(NO3)2·6H2O and Mn(NO3)2·4H2O must form a colloid with the PVA solution to reduce element segregation; moreover, after the colloid is dried at 100-150°C for 20-24 hours, it needs to be calcined in a muffle furnace once. The calcination temperature is 400-450°C, and after holding for 1-2 hours, it is naturally cooled to room temperature.

4. The preparation method of the surface titanium-coated modified lithium nickel manganese oxide cathode material according to claim 2, characterized in that, In Step 3, the ball milling time is 2-8 hours, the ball-to-material ratio is 1:(20-30), and the forward and reverse rotation speeds are both 600 r / min to form more crystal defects on the surface of the lithium nickel manganese oxide cathode powder.

5. The preparation method of the lithium nickel manganese oxide cathode material with a surface titanium coating modification according to claim 2, characterized in that, In Step 3, the powder surface coating treatment uses tetrabutyl titanate solution as the titanium source. Based on the mass of the obtained lithium nickel manganese oxide precursor powder, the mass percentage content of coated titanium is controlled at 2-8%. After titanium coating, heat treatment is required. The heating rate is 5-10°C / min, and the heat treatment temperature is 600-800°C, and it is held for 2-3 hours.

6. The preparation method of the lithium nickel manganese oxide cathode material with a surface titanium coating modification according to claim 2, characterized in that, In Step 4, the powder obtained in Step 3 is modified on the surface of its powder particles by the lithium source lithium supplementation method, and the lithium supplementation amount is 3-10% wt of the theoretical lithium content of the designed LiNi 0.5 Mn 1.5 O4. After lithium supplementation, the calcination is heated to 900-930 °C at a heating rate of 5-10 °C / min, kept warm for 12 h, and then cooled to room temperature.

7. A lithium nickel manganese oxide cathode material modified by surface titanium coating, characterized in that, The lithium nickel manganese oxide cathode material is prepared by the method according to any one of claims 1-6.

8. A lithium battery, characterized in that, Using the obtained lithium nickel manganese oxide cathode powder with a surface titanium-coated modification as the active material, the lithium battery cathode sheet is composed of an active material, a binder, and a conductive agent; the active material accounts for 80-97% of the total weight of the lithium nickel manganese oxide cathode slurry with a surface titanium-coated modification, and the weight of the conductive agent and the binder accounts for 3-20% of the total weight of the lithium nickel manganese oxide cathode slurry with a surface titanium-coated modification.

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