Method for coating a lithium nickel cobalt manganese oxide cathode material in a v-sm single crystal form

Abstract

This invention relates to a method for V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material, belonging to the field of battery cathode material synthesis technology. The method includes the following steps: S1, adding the monocrystalline lithium nickel cobalt manganese oxide cathode material to an ethanol solution and stirring vigorously to obtain suspension one; S2, taking vanadium solution and samarium solution and adding them dropwise to suspension one obtained in step S1, and stirring vigorously for 30-40 minutes to obtain suspension two; S3, centrifuging suspension two obtained in step S2, collecting the solid product, washing it with ethanol solution, vacuum drying it, and calcining it under an O2 atmosphere to obtain V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material. The V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material obtained by this invention greatly improves the electrochemical performance and structural stability of the cathode material, further extending its service life.

Description

Technical Field

[0001] This invention relates to the field of battery cathode material synthesis technology, and in particular to a method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material. Background Technology

[0002] Monocrystalline lithium nickel cobalt manganese oxide (LCO) cathode materials are composed of unique micron-sized particles, exhibiting high mechanical strength. During the rolling process, the material has a low breakage rate, and it is less prone to intergranular cracks during charge-discharge cycles, resulting in superior cycle stability. Therefore, monocrystalline LCO cathode materials hold promise for replacing traditional polycrystalline LCO cathode materials to some extent.

[0003] Due to the relatively small size of single-crystal particles, their high specific surface area increases the likelihood of electrode-electrolyte side reactions. Without appropriate surface modification, single-crystal particles can easily interact directly with the electrolyte, leading to a series of interface problems. For example, the corrosive hydrofluoric acid (HF) produced during electrolyte decomposition can adversely react with the cathode material, and the resulting thick surface film may hinder lithium-ion diffusion, thus increasing the battery's internal resistance. After long-term charge-discharge cycles, due to the continuous loss of lithium ions, the cathode material's structure may transform from a layered structure to a spinel structure or even a rock salt phase structure. These changes further affect the material's electrochemical performance.

[0004] Existing technologies generally employ doping and coating methods to modify single-crystal lithium nickel cobalt manganese oxide cathode materials. The purpose of doping is to stabilize the crystal structure and reduce Li... + and Ni 2+ Mixing, improving electronic conductivity, and strengthening chemical bonds between transition metals to suppress oxygen release; in addition, adjusting the interlayer distance by introducing ions with larger radii, thus enabling Li... + The coating process facilitates easier navigation. The purpose of coating is to construct a protective film on the surface of single-crystal lithium nickel cobalt manganese oxide cathode material particles to isolate the material from direct contact with the electrolyte, thereby reducing the chance of side reactions. Additionally, the coating layer serves as a channel for high-speed lithium-ion diffusion and promotes lithium-ion migration. However, the coating material is difficult to maintain its shape during electrochemical cycling, and this can even affect rate performance. To address the aforementioned technical problems, the inventors provide a novel preparation process for single-crystal lithium nickel cobalt manganese oxide cathode materials for lithium batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a method for V-Sm coating of monocrystalline lithium nickel cobalt manganese oxide cathode material. The method uses monocrystalline lithium nickel cobalt manganese oxide cathode material as the main body and performs V-Sm double coating modification on the surface of the monocrystalline lithium nickel cobalt manganese oxide cathode material to improve the electrochemical performance and structural stability of the monocrystalline lithium nickel cobalt manganese oxide cathode material.

[0006] The present invention provides a method for coating single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm, which adopts the following technical solution:

[0007] A method for coating single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm includes the following steps:

[0008] S1. Add the single-crystal lithium nickel cobalt manganese oxide cathode material to an ethanol solution and stir vigorously to obtain suspension one;

[0009] S2. Take vanadium solution and samarium solution and add them dropwise to the suspension one prepared in step S1, and stir vigorously for 30-40 minutes to obtain suspension two.

[0010] S3. Centrifuge the suspension II obtained in step S2, collect the solid product, wash it with ethanol solution, vacuum dry it, and calcine it under O2 atmosphere to obtain V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material.

[0011] Preferably, the mass concentration of the single-crystal lithium nickel cobalt manganese oxide cathode material in the suspension in step S1 is 30-100 mg / mL.

[0012] Preferably, the mass concentration of VCl3 in the vanadium solution in step S2 is 1-3 mg / mL;

[0013] The vanadium solution in step S2 is prepared by reacting VCl3 with an ethanol solution.

[0014] Preferably, the mass concentration of Sm(NO3)3•6H2O in the samarium solution in step S2 is 1-4 mg / mL;

[0015] The samarium solution in step S2 is prepared by reacting Sm(NO3)3·6H2O with an ethanol solution.

[0016] Preferably, in step S2, the mass ratio of VCl3 to Sm(NO3)3·6H2O in suspension II is (1-2.5):(1-3).

[0017] Preferably, the stirring speed in steps S1 and S2 is 500-1000 rpm;

[0018] The stirring time in steps S1 and S2 is 30-60 minutes.

[0019] Preferably, in step S3, the mass percentages of V and Sm in the single-crystal lithium nickel cobalt manganese oxide cathode material are 1-5 wt%.

[0020] Preferably, the vacuum drying temperature in step S3 is 70-100℃, and the vacuum drying time is 6-15h.

[0021] In step S3, the calcination temperature is 400-600℃ and the calcination time is 3-6 hours.

[0022] On the other hand, the present invention also provides a single-crystal lithium nickel cobalt manganese oxide cathode material obtained by the above-described method of coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm.

[0023] Furthermore, the present invention also provides the application of the aforementioned single-crystal lithium nickel cobalt manganese oxide cathode material in the preparation of lithium batteries.

[0024] In summary, the present invention has the following beneficial technical effects:

[0025] 1. This invention effectively reduces Li-Sm content by introducing an appropriate amount of V-Sm coating layer onto the surface of a single-crystal lithium nickel cobalt manganese oxide cathode material. + / Ni 2+ The degree of mixing increases the Li + The diffusion rate of Li + The transmission during charging and discharging is smoother, thereby improving the battery's charging and discharging capacity and coulombic efficiency. The V-Sm coating layer forms a uniform amorphous coating on the surface of the monocrystalline nickel-cobalt-manganese lithium cathode material. The amorphous coating layer can effectively avoid direct contact between the cathode material and the electrolyte, preventing the electrolyte from corroding and damaging the cathode material, thereby improving the structural stability of the material. The V-Sm coating layer can also prevent the attack of harmful substances such as HF, further extending the battery's service life.

[0026] 2. In cycle performance testing, the V-Sm-coated modified single-crystal lithium nickel cobalt manganese oxide cathode material prepared in this invention exhibits significantly reduced polarization and higher cycle stability. The presence of the V-Sm coating layer not only reduces side reactions between the electrolyte and the electrode but also inhibits the unstable growth of the SEI film, thereby mitigating damage to the particle surface structure. Furthermore, in performance tests at different rates, the V-Sm-coated modified single-crystal lithium nickel cobalt manganese oxide cathode material demonstrates excellent rate performance. Especially at high current densities, due to the coating layer's effect on Li... + The positive effect of migration allows the material to maintain a high discharge specific capacity at high rates. At the same time, the discharge specific capacity of the material can also be quickly recovered after the current density recovers, showing good reversibility. Attached Figure Description

[0027] Figure 1 These are the XRD diffraction patterns of Embodiments 1-3 and Comparative Example 1 of the present invention.

[0028] Figure 2 These are XPS scan spectra of the products in this embodiment of the invention, where a is the total XPS scan spectrum of this embodiment, b is the Ni 2p fine energy spectrum, c is the V 2p fine spectrum, and d is the Sm 3d fine spectrum.

[0029] Figure 3 These are high-resolution transmission electron microscope images of an embodiment of the present invention, wherein a, b, and c are electron microscope images of NCM, and d, e, and f are electron microscope images of NCM-2.

[0030] Figure 4 These are electrochemical performance curves of embodiments of the present invention, wherein: a is the first-cycle capacity-voltage curve of NCM, NCM-1, NCM-2 and NCM-3 at 2.75-4.3V voltage range, 25℃, and 0.1C (1C=160mAh•g-1); b is the cycling curve of NCM, NCM-1, NCM-2 and NCM-3 at 2.75-4.3V voltage range, 25℃, and 1C (1C=160mAh•g-1); c is the rate performance test of NCM, NCM-1, NCM-2 and NCM-3 at 25℃ voltage range; and d is the curve of average discharge capacity retention of NCM, NCM-1, NCM-2 and NCM-3. Detailed Implementation

[0031] The following is in conjunction with the embodiments and appendices Figure 1-4 The present invention will be described in further detail below.

[0032] Example 1

[0033] This embodiment provides a method for V-Sm coating of single-crystal lithium nickel cobalt manganese oxide cathode material, including the following steps:

[0034] S1. Add 1g of single-crystal lithium nickel cobalt manganese oxide cathode material to 20mL of ethanol solution at room temperature, and stir vigorously at a speed of 500-1000rpm for 30-60min to obtain suspension one.

[0035] S2. Dissolve 17 mg VCl3 in 10 mL of ethanol to prepare a vanadium solution, and dissolve 18.02 mg Sm(NO3)3·6H2O in 10 mL of ethanol to prepare a samarium solution. Add the vanadium solution and samarium solution dropwise to the suspension one prepared in step S1 at a rate of 20-60 drops / min, and stir continuously at a stirring speed of 500-1000 rpm for 30-60 min to obtain suspension two.

[0036] S3. Centrifuge the suspension II obtained in step S2, collect the solid product, wash it with ethanol solution, vacuum dry it at 80°C for 12 hours, take it out, and calcine it in O2 atmosphere for 3 hours at a calcine temperature of 3g to obtain V-Sm coated single crystal lithium nickel cobalt manganese oxide cathode material, labeled as NCM-2.

[0037] Example 2

[0038] This embodiment provides a method for V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material. The difference from Embodiment 1 is that in step S2, 28 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution, and 12 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The vanadium solution and samarium solution are then added dropwise to the suspension one prepared in step S1 at a rate of 20-60 drops / min, with continuous stirring at a speed of 500-1000 rpm for 30-60 min to obtain suspension two. The V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material obtained in step S3 is labeled NCM-1, and the remaining steps are the same as in Embodiment 1.

[0039] Example 3

[0040] This embodiment provides a method for V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material. The difference from Embodiment 1 is that in step S2, 13 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution, and 37 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The vanadium solution and samarium solution are then added dropwise to the suspension one prepared in step S1 at a rate of 20-60 drops / min, with continuous stirring at a speed of 500-1000 rpm for 30-60 min to obtain suspension two. The V-Sm-coated monocrystalline lithium nickel cobalt manganese oxide cathode material obtained in step S3 is labeled NCM-3, and the remaining steps are the same as in Embodiment 1.

[0041] Comparative Example 1

[0042] This comparative example is a single-crystal lithium nickel cobalt manganese oxide cathode material that has not undergone V-Sm coating treatment, labeled as NCM.

[0043] Comparative Example 2

[0044] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. The difference from Example 1 is that in step S2, 17 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution. The vanadium solution is added dropwise to the suspension one prepared in step S1 at a rate of 20-60 drops / min, and the mixture is continuously stirred at a speed of 500-1000 rpm for 30-60 min to obtain suspension two. The remaining steps are the same as in Example 1.

[0045] Comparative Example 3

[0046] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. The difference from Example 1 is that in step S2, 18.02 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The samarium solution is added dropwise to the suspension one prepared in step S1 at a rate of 20-60 drops / min, and the mixture is continuously stirred at a speed of 500-1000 rpm for 30-60 min to obtain suspension two. The remaining steps are the same as in Example 1.

[0047] Comparative Example 4

[0048] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. Unlike Example 1, in step S2, 5 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution, and 5 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The vanadium solution and samarium solution are added dropwise to the first suspension prepared in step S1 at a rate of 20-60 drops / min, and the mixture is continuously stirred at a speed of 500-1000 rpm for 30-60 min to obtain a second suspension. The mass ratio of VCl3 to Sm(NO3)3·6H2O is 1:1. The remaining steps are the same as in Example 1.

[0049] Comparative Example 5

[0050] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. Unlike Example 1, in step S2, 50 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution, and 50 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The vanadium solution and samarium solution are added dropwise to the first suspension prepared in step S1 at a rate of 20-60 drops / min, and the mixture is continuously stirred at a speed of 500-1000 rpm for 30-60 min to obtain a second suspension. The mass ratio of VCl3 to Sm(NO3)3·6H2O is 1:1. The remaining steps are the same as in Example 1.

[0051] Comparative Example 6

[0052] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. Unlike Example 1, in step S2, 30 mg of VCl3 is dissolved in 10 mL of ethanol to prepare a vanadium solution, and 1 mg of Sm(NO3)3·6H2O is dissolved in 10 mL of ethanol to prepare a samarium solution. The vanadium solution and samarium solution are added dropwise to the first suspension prepared in step S1 at a rate of 20-60 drops / min, and the mixture is continuously stirred at a speed of 500-1000 rpm for 30-60 min to obtain a second suspension. The mass ratio of VCl3 to Sm(NO3)3·6H2O is 30:1. The remaining steps are the same as in Example 1.

[0053] Comparative Example 7

[0054] This comparative example provides a method for V-Sm coating of single-crystal lithium nickel cobalt manganese oxide cathode material, including the following steps:

[0055] S1. Add 0.5g of single-crystal lithium nickel cobalt manganese oxide cathode material to 20mL of ethanol solution at room temperature, and stir vigorously at a speed of 500-1000rpm for 30-60min to obtain suspension one.

[0056] S2. Dissolve 20 mg VCl3 in 10 mL of ethanol to prepare a vanadium solution, and dissolve 20 mg Sm(NO3)3·6H2O in 10 mL of ethanol to prepare a samarium solution. Add the vanadium solution and samarium solution dropwise to the first suspension prepared in step S1 at a rate of 20-60 drops / min, and stir continuously at a stirring speed of 500-1000 rpm for 30-60 min to obtain the second suspension, wherein the mass ratio of VCl3 to Sm(NO3)3·6H2O is 1:1.

[0057] S3. Centrifuge the second suspension obtained in step S2, collect the solid product, wash it with ethanol solution, vacuum dry it at 80°C for 12 hours, take it out, and calcine it in O2 atmosphere for 3 hours at a calcine temperature of 3g to obtain V-Sm coated single crystal lithium nickel cobalt manganese oxide cathode material one.

[0058] Comparative Example 8

[0059] This comparative example provides a method for coating a single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm. The difference from Comparative Example 7 is that in step S1, 2g of single-crystal lithium nickel cobalt manganese oxide cathode material is added to 20mL of ethanol solution at room temperature and stirred vigorously at a stirring speed of 500-1000rpm for 30-60min to obtain suspension one. The remaining steps are the same as in Example 1.

[0060] Performance testing

[0061] Single-crystal lithium nickel cobalt manganese oxide cathode materials were prepared according to the methods of Examples 1-3 and Comparative Examples 1-8, and then cured. The materials were then mixed with conductive carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1, and N-methylpyrrolidone was added and stirred for 6 hours. The resulting slurry was uniformly coated onto aluminum foil, dried in an oven at 110°C for 12 hours, and then cut into 12mm circular electrode sheets. The electrodes were then charged and discharged at 2.75-4.3V with a 1C charge / discharge rate (1C = 160mAh•g) at 25°C. -1 Cycle performance tests were conducted on coin cells made from the monocrystalline lithium nickel cobalt manganese oxide cathode materials prepared in Examples 1-3 and Comparative Examples 1-8. The capacity retention rate after 450 cycles was calculated using the following formula: Capacity retention rate = Specific capacity at 450th discharge / Specific capacity at first discharge * 100%. The test results are shown in Table 1.

[0062]

[0063] As can be seen from the test data in Table 1, the single-crystal lithium nickel cobalt manganese oxide cathode materials prepared in Examples 1-3 of this application all have good capacity retention.

[0064] Reference Figure 1 The XRD diffraction patterns show that all samples belong to the hexagonal α-NaFeO2 structure of the R-3m space group, and the sharp diffraction peaks indicate that they have high crystallinity. No impurity peaks appeared in the XRD pattern, indicating that the V-Sm coating has no effect on the lattice structure of the cathode material.

[0065] Reference Figure 2 Figure a shows the total XPS scan spectrum of NCM-2, from which elements such as nickel (Ni), cobalt (Co), manganese (Mn), oxygen (O), samarium (Sm) and vanadium (V) can be clearly detected.

[0066] Reference Figure 2 b is the fine energy spectrum of Ni 2p for NCM and NCM-2. It can be observed that the Ni 2p spectrum is divided into two peaks, corresponding to Ni 2p... 1 / 2 and Ni 2p 3 / 2 Both energy level orbitals are around 871 eV and 854 eV, with Ni 2p orbital being the most common. 3 / 2 It splits into two peaks, corresponding to Ni. 2+ and Ni 3+ Furthermore, fitting analysis shows that Ni in NCM-2 2+ The proportion has decreased.

[0067] Reference Figure 2c represents the fine spectrum of V 2p, with the peak at 513.2 eV representing V0. Due to spin-orbit coupling, V 2p is divided into V 2p... 1 / 2 and V 2p 3 / 2 Two sublevels. In the case of V 2p... 3 / 2 The sub-energy level analysis revealed three distinct peaks, each corresponding to a different valence state of vanadium. Specifically, the peak at 516.1 eV corresponds to the +3 valence state of vanadium (Vo). 3 + At 516.95 eV and 517.45 eV, the values ​​correspond to a +4 valence (V), respectively. 4+ ) and +5 price (V 5+ vanadium.

[0068] Reference Figure 2 d represents the fine 3d spectrum of Sm, and we can see that Sm is present at the position of 1083.2 eV. 3+ The diffraction peaks further prove that V-Sm has been successfully coated onto the surface of the single crystal of the single-crystal lithium cobalt oxide cathode material.

[0069] Reference Figure 3 a, b, and c are electron microscope images of NCM, showing a smooth material surface and clearly identifiable lattice fringes of approximately 0.4738 nm, which correspond to the crystal planes of the hexagonal α-NaFeO2 structure, exhibiting typical layered structure characteristics.

[0070] Reference Figure 3 Images d, e, and f are electron microscope images of NCM-2. A film covers the surface of the single-crystal lithium nickel cobalt manganese oxide particles, indicating the formation of a V-Sm coating. Under magnification, a relatively uniform amorphous coating with a thickness of approximately 1-3 nm can be observed. This amorphous coating helps to isolate the cathode material from direct contact with the electrolyte, thereby improving the structural stability of the material and potentially enhancing the battery's cycle performance. Furthermore, lattice fringes with a spacing of approximately 0.4745 nm can be clearly observed beneath the coating, corresponding to the hexagonal layered structure of LiNiO2 crystal planes, indicating that the material's structure remains unaffected.

[0071] Reference Figure 4 a represents NCM, NCM-1, NCM-2, and NCM-3 at 25°C and a voltage range of 2.75–4.3V, at 0.1C (1C = 160 mAh·g). -1 The initial discharge specific capacity of NCM, NCM-1, NCM-2, and NCM-3 under the given conditions is 121.8 mAh·g. -1 123.8mAh·g -1 149.7mAh·g -1 139.6mAh·g-1 The corresponding coulombic efficiencies were 84.3%, 84.4%, 87.2%, and 86.5%, respectively. The discharge specific capacity of NCM-1 was almost unchanged compared to NCM, possibly due to insufficient coating and failure to form a complete coating layer. However, overall, the single-crystal materials modified with V-Sm coating exhibited higher discharge capacity and coulombic efficiency, especially NCM-2, which showed the best charge-discharge performance. This is likely because the V-Sm coating layer effectively suppressed Li in the material. + / Ni 2+ Mixed arrangement reduces irreversible volume loss of materials.

[0072] Reference Figure 4 b represents NCM, NCM-1, NCM-2, and NCM-3 within a voltage range of 2.75-4.3V, at 1C (1C = 160mAh·g). -1 Cycling curves at 25℃; initial discharge specific capacities of NCM, NCM-1, NCM-2, and NCM-3 were 116.7 mAh·g. -1 111.1mAh·g -1 115.3mAh·g -1 111.6mAh·g -1 After 450 cycles, the discharge specific capacities of NCM, NCM-1, NCM-2, and NCM-3 were 94.7 mAh·g⁻¹. -1 93mAh·g -1 99.7mAh·g -1 94.7mAh·g -1 The corresponding capacity retention rates were 81.1%, 83.7%, 86.5%, and 84.9%, respectively. Among them, NCM-2 exhibited the best cycle stability and the highest discharge specific capacity. This excellent cycle performance is attributed to the uniformly distributed V-Sm coating layer on the particle surface, which not only facilitates lithium-ion diffusion but also prevents side reactions caused by direct contact between the electrolyte and the electrode, thereby reducing damage to the particle structure.

[0073] Reference Figure 4 Table c shows the rate performance tests conducted on NCM, NCM-1, NCM-2, and NCM-3 at a voltage range of 2.75-4.3V and 25℃, with test current densities (i.e., rates) of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, respectively. From... Figure 4 As can be observed in diagram c, the battery's discharge specific capacity gradually decreases as the current density increases from 0.1C to 5C. This phenomenon is due to the fact that at high current densities, lithium ions (Li...)... +The reduced diffusion rate of Li₂ led to a decrease in discharge specific capacity. However, the specific capacity recovered after the current density returned to 0.1C. NCM-2 maintained a high discharge specific capacity at all rates. The discharge specific capacity of NCM-3 decreased at the same current density, possibly because excessive coating hindered the diffusion of Li₂. + The transfer of current led to an increase in impedance. Furthermore, when the current density returned to 0.1C, the discharge specific capacity of the NCM and NCM-2 samples recovered to 127.28 mAh·g⁻¹. -1 and 132.7 mAh·g -1 .

[0074] Reference Figure 4 As shown in Figure d, the average discharge capacity retention rate of NCM-2 is higher than that of NCM. This result clearly indicates that the V-Sm coating layer plays a positive role in promoting lithium-ion diffusion, thereby improving the rate performance of the modified sample. The improvement in cycle and rate performance is mainly due to the fact that the V-Sm coating layer can maintain a good ion conduction channel, reduce the interfacial impedance between the electrode material and the electrolyte, and ensure the performance stability of the battery during rapid charge and discharge.

[0075] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for coating single-crystal lithium nickel cobalt manganese oxide cathode material with V-Sm, characterized in that, Includes the following steps: S1. Add the single-crystal lithium nickel cobalt manganese oxide cathode material to an ethanol solution and stir vigorously to obtain suspension one; S2. Take vanadium solution and samarium solution and add them dropwise to the suspension one prepared in step S1, and stir vigorously for 30-40 minutes to obtain suspension two. S3. Centrifuge the suspension II obtained in step S2, collect the solid product, wash it with ethanol solution, vacuum dry it, and calcine it under O2 atmosphere to obtain V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material.

2. The method for V-Sm-coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, The mass concentration of the single-crystal lithium nickel cobalt manganese oxide cathode material in the suspension in step S1 is 30-100 mg / mL.

3. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, The mass concentration of VCl3 in the vanadium solution in step S2 is 1-3 mg / mL; The vanadium solution in step S2 is prepared by reacting VCl3 with an ethanol solution.

4. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, The mass concentration of Sm(NO3)3•6H2O in the samarium solution in step S2 is 1-4 mg / mL; The samarium solution in step S2 is prepared by reacting Sm(NO3)3·6H2O with an ethanol solution.

5. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, In step S2, the mass ratio of VCl3 to Sm(NO3)3·6H2O in suspension II is (1-2.5):(1-3).

6. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, The stirring speed in steps S1 and S2 is 500-1000 rpm; The stirring time in steps S1 and S2 is 30-60 minutes.

7. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, In step S3, the mass percentages of V and Sm in the single-crystal lithium nickel cobalt manganese oxide cathode material are 1-5 wt%.

8. The method for V-Sm coated single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1, characterized in that, In step S3, the vacuum drying temperature is 70-100℃ and the vacuum drying time is 6-15h. In step S3, the calcination temperature is 400-600℃ and the calcination time is 3-6 hours.

9. A single-crystal lithium nickel cobalt manganese oxide cathode material obtained by the method of V-Sm coating of single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 1.

10. The application of the single-crystal lithium nickel cobalt manganese oxide cathode material according to claim 9 in the preparation of lithium batteries.

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