Lithium vanadate-coated NCA ternary positive electrode material and preparation method thereof

Abstract

The application relates to a lithium vanadate-coated NCA ternary positive electrode material and a preparation method. x Co y Al 1‑x‑y (OH)2 and a vanadium source are simultaneously added into a container containing an organic solvent, wherein 0 x Co y Al 1‑x‑y (OH)2 and the vanadium source are mixed, and then the organic solvent is removed to obtain the mixed material; S3, the mixed material is subjected to high-temperature insulation, so that the vanadium source is converted into V2O5, and the V2O5 coats the Ni x Co y Al 1‑x‑y (OH)2 and the vanadium source are mixed, and then the organic solvent is removed to obtain the mixed material; S3, the mixed material is subjected to high-temperature insulation, so that vanadium source is converted into V2O5, and the V2O5 coats the x Co y Al 1‑x‑y (OH)2, to obtain a precursor coating; S4, the precursor coating and LiOH.H2O are mixed in proportion and then calcined to obtain the lithium vanadate-coated NCA ternary positive electrode material. In the preparation method, the advantages of a wet chemical method and the advantages of a solid-phase method are combined, the uniformity and effectiveness of coating are ensured, and the performance of the ternary positive electrode material is improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion material technology, specifically relating to a lithium vanadate-coated NCA ternary cathode material and its preparation method. Background Technology

[0002] High-nickel ternary cathode materials for lithium-ion batteries are a new type of cathode material characterized by high energy density, good stability, and low cost. Due to their high theoretical capacity and good stability, a large number of ternary cathode materials have been commercialized and are widely used in portable electronic devices, electric vehicles, and other applications.

[0003] A lithium-ion battery structure consists of several parts: a positive electrode, a negative electrode, a separator, and an electrolyte. The specific capacity of the positive and negative electrode materials determines the energy density of the lithium-ion battery. Compared to the rapidly developing negative electrode materials, positive electrode materials have consistently faced challenges such as low energy density, poor stability, and high cost, resulting in slower development. This has led to the slow growth of lithium-ion batteries, whose capacity and lifespan are no longer sufficient to meet the ever-increasing societal demand for energy storage. Therefore, developing high-capacity, high-stability, and low-cost positive electrode materials is essential.

[0004] To improve the performance of cathode materials, numerous researchers have devoted tremendous effort. Since its inception, lithium-ion cathode materials have undergone three generations of technological innovation. The first generation, represented by lithium cobalt oxide and lithium nickel oxide, boasted high capacity but suffered from poor stability and prohibitively high cost. The second generation, represented by lithium iron phosphate, offered low cost, long lifespan, and high safety, but its relatively low capacity failed to meet current societal demands. The third generation, represented by high-nickel ternary cathode materials, is inexpensive, offers high stability and safety, and theoretically possesses high capacity, thus gaining favor among researchers. However, its excessively high nickel content leads to rapid capacity decay, necessitating further research and improvement.

[0005] Currently known modification methods mainly include doping and coating, with coating being more effective than doping. Coating introduces a coating material onto the surface of the cathode material, preventing direct contact between the cathode material and the electrolyte, inhibiting interfacial reactions, and thus improving the cycle stability of the cathode material. Coating materials mainly include oxides and polymers. While oxides and polymers can improve cycle stability due to their poor conductivity, they also reduce the specific capacity of the cathode material to some extent, affecting the material's overall performance. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a lithium vanadate-coated NCA ternary cathode material and its preparation method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing lithium vanadate-coated NCA ternary cathode material, comprising the following steps:

[0008] S1. Weigh the material Ni according to the proportion. x Co y Al 1-x-y (OH)2 and vanadium source, Ni x Co y Al 1-x-y (OH)2 and vanadium source are added simultaneously to a container containing organic solvent, where 0 < x < 1 and 0 < y < 1.

[0009] S2. Heat and stir the material, so that the Ni x Co y Al 1-x-y (OH)2 is mixed with the vanadium source, and then the organic solvent is removed to obtain the mixed material;

[0010] S3. The mixed material is kept at a high temperature to convert the vanadium source into V2O5, and the V2O5 coats the Ni. x Co y Al 1-x-y (OH)2, to obtain the precursor coating;

[0011] S4. The precursor coating and LiOH·H2O are mixed in a certain proportion and then calcined to obtain NCA ternary cathode material coated with lithium vanadate.

[0012] In one embodiment of the present invention, the Ni x Co y Al 1-x-y The molar ratio of (OH)2 to the vanadium source is 1:a, where 0.00 < a ≤ 0.03.

[0013] In one embodiment of the present invention, the vanadium source includes one or more of NH4VO3 and vanadium acetylacetonate.

[0014] In one embodiment of the present invention, the organic solvent includes one or more of anhydrous ethanol, ethylene glycol, and methanol.

[0015] In one embodiment of the present invention, step S1 includes:

[0016] According to a molar ratio of 1:a, the materials Ni were weighed separately. 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3, and the Ni 0.8 Co 0.15 Al0.05 (OH)2 and NH4VO3 are added simultaneously to a beaker containing 40-50 ml of anhydrous ethanol; wherein, 0.00 < a ≤ 0.03.

[0017] In one embodiment of the present invention, step S2 includes:

[0018] S21. Place the container containing the material in a 65°C water bath and stir the material for more than 1 hour, so that the Ni... 0.8 Co 0.15 Al 0.05 (OH)2 is mixed with the NH4VO3;

[0019] S22. Place the container containing the material in a 75°C water bath and stir the material until the anhydrous ethanol evaporates, to obtain the mixture to be dried.

[0020] S23. The mixture to be dried is placed at 60-120℃ for vacuum drying to obtain the mixed material.

[0021] In one embodiment of the present invention, step S3 includes:

[0022] The mixed material is placed in a muffle furnace and held at 300°C for 4 hours in air atmosphere, causing the vanadium source to decompose into V₂O₅, and the V₂O₅ to coat the Ni. x Co y Al 1-x-y (OH)2 is used to obtain the precursor coating.

[0023] In one embodiment of the present invention, step S4 includes:

[0024] S41. Weigh the precursor coating material and the LiOH·H2O in a molar ratio of 1:(1.05-1.07, and grind the precursor coating material and the LiOH·H2O in a mortar to mix them, so as to obtain the mixed precursor coating material.

[0025] S42. The mixed precursor coating material is placed in a tube furnace and first held at 500°C for 5 hours, then held at 750-900°C for 720-1000 minutes in an oxygen atmosphere to obtain the calcined material.

[0026] S43. Grind and sieve the calcined material to obtain the NCA ternary cathode material coated with lithium vanadate.

[0027] Another embodiment of the present invention provides a lithium vanadate-coated NCA ternary cathode material, comprising: Li(Ni) x Co yAl 1-x-y O2 spherical secondary particles and coated on the Li(Ni) x Co y Al 1-x-y Lithium vanadate coating on the surface of O2 spherical secondary particles.

[0028] In one embodiment of the present invention, the Li(Ni) x Co y Al 1-x-y The diameter of the O2 spherical secondary particles is 250-300 nm, and the thickness of the lithium vanadate coating is 4-5 nm.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. In the preparation method of the present invention, the precursor Ni is prepared in an organic solvent using a wet chemical method. x Co y Al 1-x-y (OH)2 and vanadium source are mixed to initially coat the vanadium source onto the surface of the precursor. Then, the precursor coating is mixed with LiOH·H2O and calcined using a solid-state method to prepare lithium vanadate-coated NCA ternary cathode material. This method organically combines the advantages of wet chemical method and solid-state method, which not only simplifies the preparation process but also ensures the uniformity and effectiveness of coating, thereby improving the performance of ternary cathode material.

[0031] 2. The raw materials used in the preparation method of the present invention are readily available, the preparation process is simple, the manufacturing cost is low, the repeatability is good, and it is conducive to mass production.

[0032] 3. The lithium vanadate-coated NCA ternary cathode material of the present invention has a significantly reduced content of residual lithium compounds on the surface, resulting in better storage performance and a significant improvement in the cycle stability of the material. Attached Figure Description

[0033] Figure 1 This is a schematic flowchart illustrating a method for preparing a lithium vanadate-coated NCA ternary cathode material according to an embodiment of the present invention.

[0034] Figure 2 SEM images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material when the molar ratio of NH4VO3 added is 2% as provided in the embodiments of the present invention;

[0035] Figure 3 TEM and EDS images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material when the molar ratio of NH4VO3 added is 2% as provided in the embodiments of the present invention;

[0036] Figure 4The XRD pattern of the lithium vanadate-coated NCA cathode material provided in the embodiments of the present invention;

[0037] Figure 5 XPS images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material when the molar ratio of NH4VO3 added is 2% as provided in the embodiments of the present invention;

[0038] Figure 6 The graph shows the retention rates of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material after 100 cycles at 1C when the molar ratio of NH4VO3 added is 2%, as provided in the embodiments of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0040] Example 1

[0041] Please see Figure 1 , Figure 1 This is a schematic flowchart illustrating a method for preparing a lithium vanadate-coated NCA ternary cathode material according to an embodiment of the present invention. The method uses lithium vanadate, a fast-ion conductor, as the coating material, aiming to improve cycle stability without affecting the material's inherent performance. The preparation method mainly consists of two steps: first, a wet chemical method is used to initially coat the vanadium source onto the precursor surface in an organic solvent; then, a solid-state method is used to treat the precursor coating and LiOH·H2O to obtain the lithium vanadate-coated NCA ternary cathode material.

[0042] The preparation method specifically includes the following steps:

[0043] S1. Weigh the material Ni according to the proportion. x Co y Al 1-x-y (OH)2 and vanadium source, Ni x Co y Al 1-x-y (OH)2 and vanadium source are added simultaneously to a container containing organic solvent, where 0 < x < 1 and 0 < y < 1.

[0044] Specifically, Ni x Co y Al 1-x-y (OH)₂ is used as a precursor to generate NCA cathode materials; specifically, it includes Ni. 0.8 Co 0.15 Al 0.035 (OH)2, Ni 0.815 Co 0.15 Al 0.05One or more of (OH)₂. The vanadium source is used to generate lithium vanadate and coat it onto the surface of the NCA cathode material; specifically, it includes one or more of NH₄VO₃ and vanadium acetylacetonate. The organic solvent must be able to dissolve metavanadate and not affect Ni. x Co y Al 1-x-y The (NCA) material has an impact, including one or more of anhydrous ethanol, ethylene glycol, and methanol.

[0045] S2. Heat and stir the material, so that the Ni x Co y Al 1-x-y (OH)2 is mixed with the vanadium source, and then the organic solvent is removed to obtain the mixed material.

[0046] In one specific embodiment, the container containing the material can be heated in a water bath while the material is stirred during heating, so that Ni x Co y Al 1-x-y (OH)2 is initially mixed evenly with the vanadium source; then, the container can be heated in a water bath and the material stirred until the organic solvent is completely evaporated.

[0047] It should be noted that this embodiment is not limited to water bath heating, as long as Ni can be achieved. x Co y Al 1-x-y Both heating methods that allow (OH)2 to be initially and evenly mixed with the vanadium source and heating methods that allow the organic solvent to completely evaporate are acceptable.

[0048] Furthermore, when water bath heating is used, the material will absorb moisture. Therefore, after the organic solvent evaporates, the mixture needs to be vacuum dried to reduce the impact on the performance of the cathode material caused by the absorption of moisture during stirring in the water bath.

[0049] S3. The mixed material is kept at a high temperature to convert the vanadium source into V2O5, and the V2O5 coats the Ni. x Co y Al 1-x-y (OH)2 is used to obtain the precursor coating.

[0050] Specifically, the mixed materials are kept at a temperature sufficient to decompose the vanadium source into V₂O₅, preparing for the next step of lithium vanadate formation. For example, when the vanadium source is NH₄VO₃, the holding temperature is 300℃. Simultaneously, after this step, V₂O₅ is initially coated onto Ni. x Co y Al 1-x-yThe surface of (OH)2 was used to initially coat the vanadium source onto the precursor surface.

[0051] S4. The precursor coating and LiOH·H2O are mixed and calcined to obtain NCA ternary cathode material coated with lithium vanadate.

[0052] In one specific embodiment, the precursor coating and LiOH·H2O are mixed uniformly by grinding; however, the mixing method in this embodiment is not limited to grinding. Furthermore, the mixed material can be placed in a tube furnace and calcined for a period of time in an oxygen atmosphere to obtain lithium vanadate-coated NCA ternary cathode material.

[0053] In this embodiment, the wet chemical method can make vanadium more uniformly coated on the material surface, while the solid-state method has a simple preparation process. This preparation method makes full use of the advantages of the two processes, which not only makes the preparation process simple, but also ensures the uniformity and effectiveness of the coating, thereby improving the performance of the ternary cathode material.

[0054] The raw materials used in the preparation method of this embodiment are readily available, the preparation process is simple, the manufacturing cost is low, the repeatability is good, and it is conducive to mass production.

[0055] Example 2

[0056] Based on Example 1, this example uses Ni as the precursor. 0.8 Co 0.15 Al 0.05 The preparation method is illustrated using (OH)2, NH4VO3 as the vanadium source, and anhydrous ethanol as the organic solvent as an example.

[0057] The preparation method specifically includes the following steps:

[0058] S1. Weigh the material Ni according to the proportion. x Co y Al 1-x-y (OH)2 and vanadium source, Ni x Co y Al 1-x-y (OH)₂ and a vanadium source are simultaneously added to a container containing an organic solvent, where 0 < x < 1 and 0 < y < 1.

[0059] Specifically, Ni was weighed out according to a molar ratio of 1:a. 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3, and the Ni 0.8 Co 0.15 Al 0.05(OH)2 and NH4VO3 are added simultaneously to a beaker containing 40-50 ml of anhydrous ethanol; wherein, 0.00 < a ≤ 0.03.

[0060] Specifically, when a is 0, i.e. NH4VO3 is 0, no vanadium source is added, and the reaction in step S4 is carried out directly, resulting in a pure-phase NCA cathode material.

[0061] Preferably, the volume of anhydrous ethanol is 50 ml.

[0062] S2. Heat and stir the material, so that the Ni x Co y Al 1-x-y (OH)₂ is mixed with the vanadium source, and then the organic solvent is removed to obtain the mixed material. The specific steps include:

[0063] S21. Place the container containing the material in a 65°C water bath and stir the material for more than 1 hour, so that the Ni... 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3 are initially mixed evenly. Preferably, the stirring time is 1 hour.

[0064] In this embodiment, the material is stirred at 65°C for 1 hour to ensure that NH4VO3 is fully dissolved in anhydrous ethanol.

[0065] S22. Place the container containing the material in a 75°C water bath and stir the material until the anhydrous ethanol is completely evaporated, to obtain the mixture to be dried.

[0066] S23. The mixture to be dried is placed at 60-120℃ for vacuum drying to obtain the mixed material.

[0067] In this embodiment, drying the mixture in a vacuum drying oven at 120°C for 12 hours is to reduce the impact on the performance of the cathode material caused by the absorption of moisture during stirring in the water bath.

[0068] S3. The mixed material is kept at a high temperature to convert the vanadium source into V2O5, and the V2O5 coats the Ni. x Co y Al 1-x-y (OH)2 is used to obtain the precursor coating.

[0069] Specifically, the mixed material is placed in a muffle furnace and held at 300°C for 4 hours in an air atmosphere, causing the vanadium source to decompose into V₂O₅, and the V₂O₅ to coat the Ni. x Co yAl 1-x-y (OH)2 was used to obtain the precursor coating. The heating rate of the muffle furnace was 5 °C / min.

[0070] In this embodiment, the mixed materials are kept at high temperature to convert NH4VO3 into V2O5, in preparation for the next step of generating lithium vanadate.

[0071] S4. The precursor coating and LiOH·H2O are mixed in a certain proportion and then calcined to obtain lithium vanadate-coated NCA ternary cathode material. Specific steps include:

[0072] S41. Weigh the precursor coating material and the LiOH·H2O in a molar ratio of 1:(1.05-1.07, and grind the precursor coating material and the LiOH·H2O in a mortar to mix them, so as to obtain the mixed precursor coating material.

[0073] Preferably, the molar ratio of the precursor coating to the LiOH·H2O is 1:1.07.

[0074] In this embodiment, LiOH·H2O and Ni added throughout the experiment 0.8 Co 0.15 Al 0.05 The ratio of (OH)2 was always 1.07:1, and LiOH·H2O was not added again during the reaction.

[0075] S42. The mixed precursor coating material is placed in a tube furnace and first held at 500°C for 5 hours, then held at 750-900°C for 720-1000 minutes in an oxygen atmosphere to obtain the calcined material.

[0076] Preferably, the mixed precursor coating material is first kept at 500°C for 5 hours, and then kept at 750°C for 900 minutes to obtain the calcined material, wherein the heating rate of the tube furnace is 5°C / min.

[0077] S43. Grind and sieve the calcined material to obtain the NCA ternary cathode material uniformly coated with lithium vanadate.

[0078] In this embodiment, the preparation method uses NH4VO3 as the vanadium source and Ni 0.8 Co 0.15 Al 0.05 Pure-phase NCA was prepared using (OH)2 and LiOH·H2O as raw materials. A combination of wet chemical and solid-phase methods was used to prepare lithium vanadate-coated NCA cathode materials, which can uniformly coat lithium vanadate on the surface of NCA cathode materials, thereby achieving better cycle stability.

[0079] Example 3

[0080] This embodiment provides a lithium vanadate-coated NCA ternary cathode material, which is prepared by the method of Example 1 or Example 2. The lithium vanadate-coated NCA ternary cathode material includes: Li(Ni) x Co y Al 1-x-y O2 spherical secondary particles and coated on the Li(Ni) x Co y Al 1-x-y Lithium vanadate coating on the surface of O2 spherical secondary particles.

[0081] In one specific embodiment, Li(Ni) x Co y Al 1-x-y The diameter of the O2 spherical secondary particles is 250-300 nm, and the thickness of the lithium vanadate coating is 4-5 nm.

[0082] In this embodiment, the content of residual lithium compounds on the surface of the lithium vanadate-coated NCA ternary cathode material is significantly reduced, resulting in better storage performance and a substantial improvement in the material's cycle stability.

[0083] Example 4

[0084] Based on Examples 1 and 2, this example further illustrates the preparation method of lithium vanadate-coated NCA ternary cathode material by using different vanadium source ratios.

[0085] Comparative Example 1

[0086] Ni 0.8 Co 0.15 Al 0.05 Weigh out (OH)₂ and LiOH·H₂O in a molar ratio of 1:1.07 and grind them in a mortar for 30 minutes until uniformly mixed. Place the uniformly mixed material in a tube furnace and first hold it at 500℃ for 5 hours, then at 750℃ for 900 minutes. The heating rate for the above process is 5℃ / min, and the atmosphere is oxygen. Grind and sieve the resulting material to obtain pure-phase NCA cathode material, denoted as S0.

[0087] Example 1

[0088] Ni was weighed according to a molar ratio of 1:0.02. 0.8 Co 0.15 Al 0.05(OH)2 and NH4VO3 were added simultaneously to a small beaker containing 50 mL of anhydrous ethanol. The beaker containing the materials was placed in a 65°C water bath and stirred for 1 hour to achieve initial homogeneity. Then, it was stirred continuously in a 75°C water bath until the anhydrous ethanol was completely evaporated.

[0089] The uniformly mixed material was dried in a vacuum drying oven at 120℃ for 12 hours. The resulting material was then removed and placed in a crucible, which was then placed in a muffle furnace and kept at 300℃ for 4 hours in air atmosphere, with a heating rate of 5℃ / min. The resulting material and LiOH·H2O were weighed out in a molar ratio of 1:1.07 and ground in a mortar for 30 minutes until uniformly mixed.

[0090] The uniformly mixed material was placed in a tube furnace and first held at 500℃ for 5 hours, then at 750℃ for 900 minutes. The heating rate was 5℃ / min, and the atmosphere was oxygen. The resulting material was ground and sieved to obtain a uniformly coated NCA cathode material of 2M% lithium vanadate, denoted as S2.

[0091] The performance of S0 and S2 was characterized, and the results are as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown.

[0092] Figure 2 SEM images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material obtained when the molar ratio of NH4VO3 added is 2% according to the embodiments of the present invention.

[0093] Figure 2 In the diagram, (A) and (B) are schematic diagrams of NCA coating, with (A) being an overall schematic diagram and (B) being a magnified view of a portion of the NCA coating. (C) and (D) are schematic diagrams of pure-phase NCA. Figure 2 The main purpose was to observe the effect of coating on the morphology of NCA. It can be seen that the surface of coated NCA particles is more blurred than that of pure phase NCA, which indicates that there is a batch of coating material on the surface of coated NCA.

[0094] Figure 3 TEM and EDS images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material obtained when the molar ratio of NH4VO3 added is 2% are provided in the embodiments of the present invention.

[0095] Figure 3In the images, (A) is a TEM image of pure-phase NCA, showing a smooth particle surface. (B) is a HRTEM image of pure-phase NCA, clearly showing that there is no obvious boundary between the pure-phase NCA particles and the surrounding environment. (C) is a TEM image of coated NCA, showing a transparent coating layer on the surface. (D) is a HRTEM image of coated NCA, clearly showing a 4-5 nm coating layer between the NCA particles and the surrounding environment, indicating that the preparation method in this embodiment does indeed introduce a coating material. (E)(F)(G)(H)(I) are EDS images of coated NCA, mainly demonstrating that V is uniformly present on the surface of coated NCA.

[0096] Figure 4 The image shows the XRD pattern of the lithium vanadate-coated NCA cathode material provided in the embodiments of the present invention.

[0097] Figure 4 In the diagram, the upper curve is the XRD pattern of coated NCA, which shows impurity peaks belonging to Li3VO4, while the lower curve represents the XRD pattern of pure phase NCA, which does not show impurity peaks belonging to Li3VO4. This indicates that the method in this embodiment successfully prepared Li3VO4.

[0098] Figure 5 XPS images of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material obtained when the molar ratio of NH4VO3 added is 2% according to embodiments of the present invention.

[0099] Figure 5 In the figure, (A) represents C1s, with the peak at 289.9 representing the residual lithium content. The upper part of the figure represents coated NCA, where the peak at 289.9 decreases significantly, indicating that the residual lithium is eliminated. (B) represents O1s, with 533.4 representing adsorbed oxygen, 532.4 representing active oxygen, and 529.9 representing lattice oxygen. The figure shows that the adsorbed oxygen ratio of NCA decreases after coating, while the lattice oxygen peak increases, indicating that the method in this embodiment increases the hydrophobicity of the material while strengthening the lattice structure. (C) represents Ni 2p, with the upper part representing coated NCA. 2+ The decrease in content proves that its lithium-nickel mixture is smaller. (D) is V 2p, and the above is the coated NCA, which shows the V5+ characteristic peak, while pure NCA does not, which further confirms that Li3VO4 is coated.

[0100] Figure 6 The graph shows the retention rates of lithium vanadate-coated NCA cathode material and pure-phase NCA cathode material after 100 cycles at 1C when the molar ratio of NH4VO3 added is 2%, as provided in the embodiments of the present invention.

[0101] Figure 6 The graph shows the retention rate of NCA (non-carbonyl chloride) after 100 cycles of 1C charge-discharge on the battery. The top curve represents the NCA retention rate for a 2M% Li3VO4 coating, while the bottom curve represents the NCA retention rate for a pure phase. Figure 6 This demonstrates that NCA cycle performance is significantly improved when Li3VO4 is coated.

[0102] Example 2

[0103] Ni was weighed according to a molar ratio of 1:0.03. 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3 were simultaneously added to a small beaker containing 50 mL of anhydrous ethanol. The beaker containing the materials was placed in a 65°C water bath and stirred for 1 hour to achieve initial uniform mixing. Then, it was stirred continuously in a 75°C water bath until the anhydrous ethanol was completely evaporated.

[0104] The uniformly mixed material was dried in a vacuum drying oven at 120℃ for 12 hours. The resulting material was then removed and placed in a crucible, which was then placed in a muffle furnace and kept at 300℃ for 4 hours in air atmosphere, with a heating rate of 5℃ / min. The resulting material and LiOH·H2O were weighed out in a molar ratio of 1:1.07 and ground in a mortar for 30 minutes until uniformly mixed.

[0105] The uniformly mixed material was placed in a tube furnace and first held at 500℃ for 5 hours, then at 750℃ for 900 minutes. The heating rate was 5℃ / min, and the atmosphere was oxygen. The resulting material was ground and sieved to obtain a 3M% lithium vanadate uniformly coated NCA cathode material.

[0106] The lithium vanadate-coated NCA cathode material prepared in this embodiment has a significantly reduced content of residual lithium compounds on its surface, resulting in better storage performance and a substantial improvement in cycle stability.

[0107] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing lithium vanadate-coated NCA ternary cathode material, characterized in that, Including the following steps: S1. Weigh the material Ni according to the proportion. x Co y Al 1-x-y (OH)2 and vanadium source, Ni x Co y Al 1-x-y (OH)2 and vanadium source are added simultaneously to a container containing organic solvent, where 0 < x < 1 and 0 < y < 1. S2. Heat and stir the material, so that the Ni x Co y Al 1-x-y (OH)2 is mixed with the vanadium source, and then the organic solvent is removed to obtain the mixed material; S3. The mixed material is kept at a high temperature to convert the vanadium source into V2O5, and the V2O5 coats the Ni. x Co y Al 1-x-y (OH)2, to obtain the precursor coating; S4. The precursor coating and LiOH·H2O are mixed in a certain proportion and then calcined to obtain NCA ternary cathode material coated with lithium vanadate.

2. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, The Ni x Co y Al 1-x-y The molar ratio of (OH)2 to the vanadium source is 1:a, where 0.00 < a ≤ 0.

03.

3. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, The vanadium source includes one or more of NH4VO3 and vanadium acetylacetonate.

4. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, The organic solvent includes one or more of anhydrous ethanol, ethylene glycol, and methanol.

5. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, Step S1 includes: According to a molar ratio of 1:a, the materials Ni were weighed separately. 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3, and the Ni 0.8 Co 0.15 Al 0.05 (OH)2 and NH4VO3 are simultaneously added to a beaker containing 40-50 ml of anhydrous ethanol; wherein, 0.00 < a ≤ 0.

03.

6. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 5, characterized in that, Step S2 includes: S21. Place the container containing the material in a 65°C water bath and stir the material for more than 1 hour, so that the Ni... 0.8 Co 0.15 Al 0.05 (OH)2 is mixed with the NH4VO3; S22. Place the container containing the material in a 75°C water bath and stir the material until the anhydrous ethanol evaporates, to obtain the mixture to be dried. S23. The mixture to be dried is placed at 60-120℃ for vacuum drying to obtain the mixed material.

7. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, Step S3 includes: The mixed material is placed in a muffle furnace and held at 300°C for 4 hours in air atmosphere, causing the vanadium source to decompose into V₂O₅, and the V₂O₅ to coat the Ni. x Co y Al 1-x-y (OH)2 is used to obtain the precursor coating.

8. The method for preparing lithium vanadate-coated NCA ternary cathode material according to claim 1, characterized in that, Step S4 includes: S41. Weigh the precursor coating material and the LiOH·H2O in a molar ratio of 1:(1.05-1.07, and grind the precursor coating material and the LiOH·H2O in a mortar to mix them, so as to obtain the mixed precursor coating material. S42. The mixed precursor coating material is placed in a tube furnace and first held at 500°C for 5 hours, then held at 750-900°C for 720-1000 minutes in an oxygen atmosphere to obtain the calcined material. S43. Grind and sieve the calcined material to obtain the NCA ternary cathode material coated with lithium vanadate.

9. A lithium vanadate-coated NCA ternary cathode material, characterized in that, Prepared by the preparation method according to any one of claims 1-8, comprising: Li(Ni x Co y Al 1-x-y O2 spherical secondary particles and coated on the Li(Ni) x Co y Al 1-x-y The lithium vanadate coating on the surface of O2 spherical secondary particles, wherein 0 < x < 1, 0 < y < 1.

10. The lithium vanadate-coated NCA ternary cathode material according to claim 9, characterized in that, The Li(Ni) x Co y Al 1-x-y The diameter of the O2 spherical secondary particles is 250-300 nm, and the thickness of the lithium vanadate coating is 4-5 nm.

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