Preparation method of ternary positive electrode material, ternary positive electrode material and power battery

Abstract

A method for preparing a ternary cathode material, the ternary cathode material itself, and a power battery are disclosed. The ternary cathode material comprises particles with a central porous structure and has the general chemical formula LiNi. x CoyMnzM p O2, wherein M is at least two elements selected from W, Al, Ti, and B, and a combination of at least two elements selected from Al, Zr, and P; wherein at least two elements selected from W, Al, Ti, and B are doped into the particles, while metal oxides of at least two elements selected from Al, Zr, and P are coated on the outside of the particles. This ternary cathode material can improve the high-rate charge-discharge performance of power batteries and enhance cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium battery manufacturing technology, and in particular to a method for preparing a ternary cathode material, the ternary cathode material, and a power battery. Background Technology

[0002] Hybrid electric vehicles (HEVs) have stringent requirements for the high-rate charge-discharge performance (≥10C) and long cycle life of their power batteries. Medium-nickel ternary materials (Ni content 40%-60%), such as NCM523 (Ni:Co:Mn=5:2:3), have become the mainstream choice for HEV batteries due to their advantages of high energy density (160-180mAh / g) and low cost (20% cobalt content). However, they suffer from high lithium-ion diffusion resistance and high interfacial impedance at high discharge rates. Existing technologies modify the surface of the ternary precursor with metal oxides, such as Al2O3 or ZrO2, to suppress side reactions. However, single coating layers have defects such as uneven thickness and weak interfacial adhesion, leading to poor 10C high-rate cycling performance and failing to meet the operating requirements of HEVs. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for preparing a ternary cathode material, the ternary cathode material itself, and a power battery. This ternary cathode material can improve the high-rate charge-discharge performance of the power battery and enhance cycle stability.

[0004] This invention provides a ternary cathode material comprising particles with a central porous structure, having the chemical formula LiNi. x CoyMnzM p O2, wherein M is at least two elements selected from W, Al, Ti, and B, and a combination of at least two elements selected from Al, Zr, and P; wherein at least two elements selected from W, Al, Ti, and B are doped into the particles, and metal oxides of at least two elements selected from Al, Zr, and P are coated on the outside of the particles.

[0005] This invention also provides a method for preparing a ternary cathode material, comprising the following steps: Prepare a metal salt ion solution containing nickel, cobalt and manganese sources, and a dispersant solution containing urea and polyvinylpyrrolidone. The metal salt solution and the dispersant solution are mixed and the pH is adjusted to produce a precipitate, which is then washed and dried to obtain a ternary precursor having a hollow core-shell structure. Prepare a doping element solution containing a doping element, and use the doping element solution to dope the ternary precursor to form a doped ternary precursor; A coating layer is formed outside the doped ternary precursor to form a coated precursor; The coated precursor is mixed and ground with the lithium source, and then sintered and cooled to obtain a ternary cathode material.

[0006] Furthermore, the molar ratio of the nickel source, the cobalt source, and the manganese source is 3-6:1-3.5:1-4.

[0007] Furthermore, the concentration of urea is 0.8 mol%-1.2 mol, and the concentration of polyvinylpyrrolidone is 0.08 mol%-0.12 mol.

[0008] Furthermore, when mixing the metal salt solution with the dispersant solution, the volume ratio of the metal salt solution to the dispersant solution is 1:0.8-1.2.

[0009] Furthermore, in the hollow core-shell structure of the ternary precursor, the porosity is greater than 80%, and the porosity is 30%-40%.

[0010] Furthermore, the doping element is at least two of tungsten, aluminum, titanium, and boron.

[0011] Furthermore, during the coating process, the coating layer is formed using oxides of at least two of the elements selected from aluminum, zirconium, and phosphorus.

[0012] Furthermore, when sintering the coated precursor with the lithium source, the method includes the following steps: The temperature is raised from the first temperature to the second temperature at the first heating rate, and then kept at that temperature in an N2 atmosphere. The temperature is raised from the second temperature to the third temperature at a second heating rate, and then held at that temperature in an O2 atmosphere. Stop heating, and when the temperature drops back to the second temperature, switch back to the N2 atmosphere and cool to room temperature to complete sintering.

[0013] The present invention also provides a power battery comprising the above-mentioned ternary cathode material.

[0014] In summary, this invention utilizes urea to assist in the co-precipitation method for preparing a hollow core-shell structure of the ternary precursor by adding urea during the preparation process. Elemental doping and double-layer coating are then performed. After sintering, the ternary cathode material forms secondary particles with porous centers. This porous structure shortens the lithium-ion diffusion path, reduces bulk diffusion resistance, and decreases high-rate polarization voltage. Furthermore, the porous surface of the ternary cathode material provides more active sites, which, combined with the surface coating, form "ion sieve" channels, promoting rapid lithium-ion transport. Additionally, the hollow structure buffers volume expansion, reduces microcrack formation, and improves the structural integrity of the power battery during cycling.

[0015] Furthermore, by doping the ternary precursor with multiple elements, the ternary precursor can be modified to improve the characteristics of the cathode material. Taking tungsten, aluminum, and titanium as examples, tungsten ions can enter the Ni site to form a strong covalent Ni-O bond, inhibiting nickel ion migration and reducing bulk mixing; aluminum ions can occupy the edge of the Li site to reduce lattice distortion during lithium ion insertion / extraction; and titanium ions can form a stable transition metal layer to inhibit Mn dissolution during cycling and improve high-temperature structural stability.

[0016] Furthermore, employing a multi-layer coating approach can suppress interfacial side reactions and improve cycle capacity retention through the combined effect of various coating layers. Taking aluminum and zirconium metal oxide coatings as an example, the inner Al2O3 layer can chemically adsorb HF in the electrolyte, inhibiting the formation of residual lithium on the surface, while the outer ZrO2 layer has a high-density lattice, which can physically block the penetration of the electrolyte and improve the mechanical strength of the coating layer. The combined effect of these two factors can further isolate the electrolyte and suppress the coating layer shedding rate during battery cycling.

[0017] Furthermore, by employing a gradient sintering process, segmented atmosphere control can suppress excessive oxidation of the cathode material surface during formation, reduce residual lithium content, and improve initial coulombic efficiency. During the heating sintering stage (i.e., the S51 stage), the carbon dioxide generated from the decomposition of Li2CO3 creates micro-pressure within the porous structure, aiding pore formation while reducing lithium volatilization during sintering, promoting dopant diffusion, and preventing element segregation caused by high-temperature sintering.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Detailed Implementation

[0019] Specific embodiments of the present invention will now be described in detail. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0021] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar attributes, not to indicate or imply relative importance or a specific order.

[0022] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0023] This invention provides a method for preparing a ternary cathode material, the ternary cathode material, and a power battery. The ternary cathode material can improve the high-rate charge-discharge performance of the power battery and enhance the cycle stability.

[0024] The method for preparing ternary cathode material provided by this invention includes the following steps: S1: Prepare a metal salt mixture containing nickel, cobalt and manganese sources, and prepare a dispersant solution containing urea and polyvinylpyrrolidone (PVP).

[0025] In this embodiment, the nickel source can be NiSO4. 6H2O; the cobalt source can be CoSO4 7H2O; the manganese source can be MnSO4 H₂O. The ratio of nickel, cobalt, and manganese sources, by molar amount, is 3-6:1-3.5:1-4, such as 3:3:4, 3:3.5:3.5, 4:2:4, 4:3:3, 4:3.5:2.5, 5:2:3, 6:1.5:2.5, 6:3:1, etc. Preferably, the ratio of nickel, cobalt, and manganese sources fluctuates around 5:2:3. All three can be dissolved simultaneously in deionized water to form a metal salt solution.

[0026] The concentration of urea can range from 0.8 mol% to 1.2 mol%, such as 0.8 mol%, 0.9 mol%, 1 mol%, 1.1 mol%, 1.2 mol%, etc., while the concentration of polyvinylpyrrolidone (PVC) ranges from 0.08 mol% to 0.12 mol%, such as 0.08 mol%, 0.09 mol%, 0.1 mol%, 0.11 mol%, 0.12 mol%, etc. Both can be dissolved simultaneously in deionized water to form a dispersant solution.

[0027] S2: The metal salt mixture and dispersant solution are mixed; a pH adjuster is added to produce a precipitate, which is then washed and dried to obtain a ternary precursor. This ternary precursor has a hollow core-shell structure.

[0028] In this embodiment, the metal salt mixture and the dispersant solution can be added dropwise to the reaction vessel at the same time, with a volume ratio of 1:0.8-1.2, such as 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc.

[0029] In this embodiment, the pH adjuster can be NaOH, and its pH range can be 9-10, such as 9, 9.2, 9.5, 9.8, 10, etc.

[0030] During the precipitation process, the reaction system can be heated and stirred. Heating temperatures range from 50-70℃, such as 50℃, 55℃, 60℃, 65℃, and 70℃. Stirring speeds range from 450-550 rpm, such as 450 rpm, 470 rpm, 500 rpm, 530 rpm, and 550 rpm. The reaction time ranges from 4-8 hours, such as 4 hours, 5 hours, 6 hours, 7 hours, and 8 hours, to promote the generation of carbon dioxide gas in the reaction system.

[0031] During the nucleation process of ternary precursors, the generation of a large amount of carbon dioxide enables the formation of ternary precursor nuclei with a porous center.

[0032] In this embodiment, the hollow core-shell structure of the ternary precursor has a hollow core-shell structure with a void ratio greater than 80%, more preferably greater than 85%. This data can be determined by observation using an electron microscope. In this embodiment, the D50 of the ternary precursor is 5-7 μm, such as 5 μm, 6 μm, 7 μm, etc. The porosity is 30%-40%, such as 30%, 33%, 35%, 38%, 40%, etc.

[0033] S3: Prepare a doping element solution and use the doping element solution to dope the ternary precursor to form a doped ternary precursor.

[0034] In this embodiment, the doping element can be at least two of the elements such as tungsten, aluminum, titanium, and boron, preferably three of tungsten, aluminum, titanium, and boron. For example, the doping element can be tungsten, aluminum, and titanium. The molar ratio of tungsten, aluminum, and titanium is (0.5-2):(0.5-2):(0.3-1), such as 0.5:0.5:0.3, 0.5:0.5:0.5, 0.5:0.5:0.7, 0.5:0.5:1, 0.5:1:0.3, 0.5:1:0.5, 0.5:1:0.7, 0.5:1:1, 0.5:1.5:0.3, 0.5:1.5:0.5, 0.5:1.5:0.7, 0. 0.5:1.5:1, 0.5:2:0.3, 0.5:2:0.5, 0.5:2:0.7, 0.5:2:1, 1:0.5:0.3, 1:0.5:0.5, 1:0.5:0.7, 1:0.5:1, 1.5:1:0.3, 1.5:1:0.5, 1.5:1:0.7, 1.5:1:1, 2:1.5:0.3, 2:1.5:0.5, 2:1.5:0.7, 2:1.5:1, 2:2:1, etc.

[0035] The tungsten source can be (NH4)2WO4; the aluminum source can be Al(NO3)3. 9H2O and the titanium source can be Ti(OC4H9)4.

[0036] Compounds containing various doping elements can be added to ethanol to prepare solutions with a total concentration of 0.05 mol% to 0.15 mol%, such as 0.05 mol%, 0.07 mol%, 0.1 mol%, 0.15 mol%, etc.

[0037] By mass, the solid-liquid ratio of the ternary precursor to the dopant solution is 1:5.

[0038] The ternary precursor and the dopant element solution can be mixed by ultrasonic dispersion. The ultrasonic dispersion time is 25-35 min, such as 25 min, 27 min, 30 min, 33 min, 35 min, etc.

[0039] Then, spin-coating evaporation is performed at temperatures of 70-90℃, such as 70℃, 75℃, 80℃, 85℃, 90℃, etc., to obtain the doped ternary precursor.

[0040] S4: A coating layer is formed outside the doped ternary precursor to form a coated precursor.

[0041] In this embodiment, the coating layer can be formed using oxides of at least two of the elements selected from aluminum, zirconium, and phosphorus. For example, an Al2O3 layer and a ZrO2 layer can be used to form the coating layer.

[0042] In this embodiment, trimethylaluminum and H2O can be used as raw materials, and atomic layer deposition can be used to deposit 2-4 cycles at 140℃-160℃, such as 140℃, 145℃, 150℃, 155℃, 160℃, etc., to form an Al2O3 layer on the surface of the ternary precursor.

[0043] Using zirconium tetratert-butoxide and H2O as raw materials, atomic layer deposition is employed to deposit 1-3 cycles at temperatures ranging from 140℃ to 160℃, such as 140℃, 145℃, 150℃, 155℃, and 160℃, to form a ZrO2 layer outside the Al2O3 layer.

[0044] The order of the oxide coating layers of each element is not limited during the coating process.

[0045] In this embodiment, the thickness of the aluminum oxide coating layer is 2-5 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, etc.; the thickness of the zirconium oxide coating layer is 1-3 nm, such as 1 nm, 2 nm, 3 nm, etc.; and the thickness of the phosphorus oxide coating layer is 1-4 nm, such as 1 nm, 2 nm, 3 nm, 4 nm, etc.

[0046] S5: The coated precursor is mixed and ground with the lithium source, and then sintered. After cooling, a ternary cathode material is obtained.

[0047] In this embodiment, the purity of the lithium source is not less than 99.9%. The lithium source can be Li2CO3. In terms of molar amount, the ratio of the sum of the amounts of the transition metals in the precursor to the amount of lithium in the lithium source is 100:103-100:106, such as 100:103, 100:105, 100:105, 100:106, etc.

[0048] This method uses gradient sintering and includes the following steps: S51: The temperature is increased from a first temperature, such as 400℃, to a second temperature, such as 500℃, at a first heating rate, such as 4℃-6℃, preferably 4℃, 5℃, or 6℃, and held at this temperature for 1-3 hours, such as 1 hour, 2 hours, or 3 hours, under a N2 atmosphere. This causes partial decomposition of Li2CO3 into LiO. - It reacts with the hydroxyl groups on the surface of the coated precursor to generate a LiOH transition layer. S52: Switch to O2 atmosphere and raise the temperature from the second temperature, such as 500℃, to the third temperature, such as 850℃, at the second heating rate, such as 2℃-4℃, preferably 2℃, 3℃, 4℃, etc., and hold for 8-12 hours, such as 8h, 9h, 10h, 11h, 12h, etc., to complete the diffusion of bulk doped elements and lattice reconstruction. S53: Stop heating, and when the temperature drops to the second temperature, such as 500℃, switch to N2 atmosphere and cool the furnace to room temperature to obtain ternary cathode material.

[0049] In this invention, urea is added during the preparation of the ternary precursor to assist in the co-precipitation method to prepare a precursor with a hollow core-shell structure. Then, elemental doping and double-layer coating are performed. After sintering, the ternary cathode material forms secondary particles with porous centers. The porous structure can shorten the diffusion path of lithium ions, reduce bulk diffusion resistance, and decrease high-rate polarization voltage. Furthermore, the porous surface of the ternary cathode material can provide more active sites, which, combined with the surface coating layer, can form "ion sieve" channels to promote rapid lithium ion transport. Furthermore, the hollow structure can also buffer volume expansion, reduce microcrack formation, and improve the structural integrity of the power battery during cycling.

[0050] Furthermore, by doping the ternary precursor with multiple elements, the ternary precursor can be modified to improve the characteristics of the cathode material. Taking tungsten, aluminum, and titanium as examples, tungsten ions can enter the Ni site to form a strong covalent Ni-O bond, inhibiting nickel ion migration and reducing bulk mixing; aluminum ions can occupy the edge of the Li site to reduce lattice distortion during lithium ion insertion / extraction; and titanium ions can form a stable transition metal layer to inhibit Mn dissolution during cycling and improve high-temperature structural stability.

[0051] Furthermore, employing a multi-layer coating approach can suppress interfacial side reactions and improve cycle capacity retention through the combined effect of various coating layers. Taking aluminum and zirconium metal oxide coatings as an example, the inner Al2O3 layer can chemically adsorb HF in the electrolyte, inhibiting the formation of residual lithium on the surface, while the outer ZrO2 layer has a high-density lattice, which can physically block the penetration of the electrolyte and improve the mechanical strength of the coating layer. The combined effect of these two factors can further isolate the electrolyte and suppress the coating layer shedding rate during battery cycling.

[0052] Furthermore, by employing a gradient sintering process, segmented atmosphere control can suppress excessive oxidation of the cathode material surface during formation, reduce residual lithium content, and improve initial coulombic efficiency. During the heating sintering stage (i.e., the S51 stage), the carbon dioxide generated from the decomposition of Li2CO3 creates micro-pressure within the porous structure, aiding pore formation while reducing lithium volatilization during sintering, promoting dopant diffusion, and preventing element segregation caused by high-temperature sintering.

[0053] The following describes the preparation method of the ternary cathode material provided by the present invention using specific embodiments.

[0054] Example 1: NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water in a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); and a dispersant solution containing urea solution (concentration 1 mol%) and polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared.

[0055] The metal salt solution and the dispersant solution were simultaneously added dropwise to the reactor (50L), the temperature was controlled at 60℃, the pH was 9.5 (adjusted by NaOH), the stirring speed was 500rpm, and the reaction was carried out for 6h until D50=6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12h, the ternary precursor was obtained.

[0056] (NH4)2WO4, Al(NO3)3 9H2O and Ti(OC4H9)4 (W:Al:Ti = 1:0.5:0.3 by molar amount) were dissolved in ethanol to form a dopant solution (concentration of 0.1 mol%). The mixture was then mixed at a solid-liquid ratio of 1:5 by mass, ultrasonically dispersed for 30 min, and rotary evaporated at 80 °C to dryness, so that the dopant element was uniformly adsorbed on the surface and pore walls of the ternary precursor.

[0057] Using trimethylaluminum and H2O as raw materials, an atomic deposition process was employed at 150°C for 2–4 cycles to form a 3 nm Al2O3 layer. Using tetratert-butoxide zirconium and H2O as raw materials, a 2 nm ZrO2 layer was formed by deposition at 150°C for 1–3 cycles.

[0058] The coating precursor and Li2CO3 (the molar ratio of coating precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0059] Example 2: NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water in a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); and a dispersant solution containing urea solution (concentration 1 mol%) and polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared.

[0060] The metal salt solution and the dispersant solution were simultaneously added dropwise to the reactor (50L), the temperature was controlled at 60℃, the pH was 9.5 (adjusted by NaOH), the stirring speed was 500rpm, and the reaction was carried out for 6h until D50=6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12h, the ternary precursor was obtained.

[0061] (NH4)2WO4, Al(NO3)3 9H2O and Ti(OC4H9)4 (W:Al:Ti = 2:0.5:2 by molar amount) were dissolved in ethanol to form a dopant solution (concentration of 0.1 mol%). The mixture was then mixed at a solid-liquid ratio of 1:5 by mass, ultrasonically dispersed for 30 min, and rotary evaporated at 80 °C to dryness, so that the dopant element was uniformly adsorbed on the surface and pore walls of the ternary precursor.

[0062] Using trimethylaluminum and H2O as raw materials, an atomic deposition process was employed at 150°C for 2–4 cycles to form a 3 nm Al2O3 layer. Using tetratert-butoxide zirconium and H2O as raw materials, a 2 nm ZrO2 layer was formed by deposition at 150°C for 1–3 cycles.

[0063] The coating precursor and Li2CO3 (the molar ratio of coating precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0064] Example 3: NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water in a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); and a dispersant solution containing urea solution (concentration 1 mol%) and polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared.

[0065] The metal salt solution and the dispersant solution were simultaneously added dropwise to the reactor (50L), the temperature was controlled at 60℃, the pH was 9.5 (adjusted by NaOH), the stirring speed was 500rpm, and the reaction was carried out for 6h until D50=6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12h, the ternary precursor was obtained.

[0066] (NH4)2WO4, Al(NO3)3 9H2O and Ti(OC4H9)4 (W:Al:Ti ratio of 1.5:0.5:0.3 by molar amount) were dissolved in ethanol to form a dopant solution (concentration of 0.1 mol%). The mixture was then mixed at a solid-liquid ratio of 1:5 by mass, ultrasonically dispersed for 30 min, and rotary evaporated at 80 °C to dryness, so that the dopant element was uniformly adsorbed on the surface and pore walls of the ternary precursor.

[0067] Using trimethylaluminum and H2O as raw materials, an atomic deposition process was employed at 150°C for 2–4 cycles to form a 3 nm Al2O3 layer. Using tetratert-butoxide zirconium and H2O as raw materials, a 2 nm ZrO2 layer was formed by deposition at 150°C for 1–3 cycles.

[0068] The coating precursor and Li2CO3 (the molar ratio of coating precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0069] Comparative Example 1 (without any modification): NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water at a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); a polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared separately as a dispersant solution.

[0070] The metal salt solution and dispersant solution were added dropwise to a 50L reactor. The temperature was controlled at 60℃ and the pH at 9.5 (adjusted with NaOH). The stirring speed was 500rpm, and the reaction was carried out for 6 hours until the D50 reached 6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12 hours, the ternary precursor was obtained.

[0071] The precursor and Li2CO3 (the molar ratio of precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0072] Comparative Example 2 (coated with only a single layer of Al2O3): NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water in a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); a dispersant solution containing urea solution (concentration 1 mol%) and polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared separately.

[0073] The metal salt solution and the dispersant solution were simultaneously added dropwise to the reactor (50L), and the temperature was controlled at 60℃, pH=9.5 (adjusted by NaOH), the stirring speed was 500rpm, and the reaction was carried out for 6h until D50=6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12h, the ternary precursor was obtained.

[0074] ((NH4)2WO4, Al(NO3)3 9H2O and Ti(OC4H9)4 (W:Al:Ti ratio of 1.5:0.5:0.3 by molar amount) were dissolved in ethanol to form a dopant solution (concentration of 0.1 mol%). The mixture was then mixed at a solid-liquid ratio of 1:5 by mass, ultrasonically dispersed for 30 min, and rotary evaporated at 80 °C to dryness, so that the dopant element was uniformly adsorbed on the surface and pore walls of the ternary precursor.

[0075] Using trimethylaluminum and H2O as raw materials, an atomic deposition method was used to deposit 2 to 4 cycles at 150°C to form a 3nm Al2O3 layer.

[0076] The coating precursor and Li2CO3 (the molar ratio of coating precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0077] Comparative Example 3 (doped with only tungsten): NiSO4 6H2O, CoSO4 7H2O and MnSO4 H2O was dissolved in deionized water in a molar ratio of 5:2:3 to form a metal salt solution (concentration 1.5 mol%); a dispersant solution containing urea solution (concentration 1 mol%) and polyvinylpyrrolidone solution (concentration 0.1 mol%) was prepared separately.

[0078] The metal salt solution and the dispersant solution were simultaneously added dropwise to the reactor (50L), and the temperature was controlled at 60℃, pH=9.5 (adjusted by NaOH), the stirring speed was 500rpm, and the reaction was carried out for 6h until D50=6μm. After centrifugation and washing (three times with deionized water) and drying at 120℃ for 12h, the ternary precursor was obtained.

[0079] (NH4)2WO4 was dissolved in ethanol to form a dopant solution (concentration of 0.1 mol%). The solution was mixed at a solid-liquid ratio of 1:5 by mass, ultrasonically dispersed for 30 min, and then rotary evaporated at 80 °C to dryness, so that the dopant element was uniformly adsorbed on the surface and pore walls of the ternary precursor.

[0080] Using trimethylaluminum and H2O as raw materials, an atomic deposition process was employed at 150°C for 2–4 cycles to form a 3 nm Al2O3 layer. Using tetratert-butoxide zirconium and H2O as raw materials, a 2 nm ZrO2 layer was formed by deposition at 150°C for 1–3 cycles.

[0081] The coating precursor and Li2CO3 (the molar ratio of coating precursor to lithium source is 100:105) are ground and mixed. The temperature is raised from 400℃ to 500℃ (heating rate 5℃ / min), and held at N2 atmosphere for 2 hours. Then, the O2 atmosphere is switched, and the temperature is raised to 850℃ (heating rate 3℃ / min), held for 10 hours, and then cooled to 500℃. The N2 atmosphere is switched back, and the furnace is cooled to room temperature to obtain the finished product.

[0082] After obtaining the cathode materials of each embodiment and comparative example, they were prepared into power batteries and subjected to rate testing and cycle testing.

[0083] During the rate test, each group of power batteries is charged at 1C to 4.25V, left to rest for 10 minutes, and then discharged at a set current N to 2.8V. Capacity retention rate at N rate = N rate discharge capacity / 1C discharge capacity. For example, 10C capacity retention rate = 10C discharge capacity / 1C discharge capacity.

[0084] During the cycle test, each group of power batteries was charged at 10C to 4.25V, rested for 10 minutes, discharged at 10C to 2.8V, and rested for 10 minutes, for a total of 100 charge-discharge cycles. The capacity retention rate after 100 cycles = discharge capacity on the 100th cycle / discharge capacity on the 1st cycle.

[0085] Table 1: Comparison of Multiplier Tests for Each Group

[0086] Table 2: Volume retention rate after 100 cycles for each group

[0087] As can be seen from Tables 1 and 2 above, the cathode material provided by the present invention has significantly improved high-rate charge-discharge performance and cycle stability compared with Comparative Examples 1 to 3.

[0088] This invention also provides a ternary cathode material, which is prepared by the above-described method for preparing ternary cathode materials. The ternary cathode material comprises particles with a central porous structure and has the general chemical formula LiNi. x Co y Mn z M p O2, wherein M is a combination of at least two of W, Al, Ti, and B, and at least two of Al, Zr, and P, and x+y+z+p=1; wherein at least two of W, Al, Ti, and B are doped into the particles, and metal oxides of at least two of Al, Zr, and P are coated on the outside of the particles.

[0089] The present invention also provides a power battery comprising the aforementioned positive electrode material. For other technical features of this power battery, please refer to the prior art, which will not be repeated here. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A ternary cathode material, characterized in that: The ternary cathode material comprises particles with a central porous structure, and its general chemical formula is LiNi. x CoyMnzM p O2, wherein M is at least two elements selected from W, Al, Ti, and B, and a combination of at least two elements selected from Al, Zr, and P; wherein at least two elements selected from W, Al, Ti, and B are doped into the particles, and metal oxides of at least two elements selected from Al, Zr, and P are coated on the outside of the particles.

2. A method for preparing a ternary cathode material, characterized in that: Includes the following steps: Prepare a metal salt ion solution containing nickel, cobalt and manganese sources, and a dispersant solution containing urea and polyvinylpyrrolidone. The metal salt solution and the dispersant solution are mixed and the pH is adjusted to produce a precipitate, which is then washed and dried to obtain a ternary precursor having a hollow core-shell structure. Prepare a doping element solution containing a doping element, and use the doping element solution to dope the ternary precursor to form a doped ternary precursor; A coating layer is formed outside the doped ternary precursor to form a coated precursor; The coated precursor is mixed and ground with the lithium source, and then sintered and cooled to obtain a ternary cathode material.

3. The method for preparing the ternary cathode material according to claim 2, characterized in that: The molar ratio of the nickel source, the cobalt source, and the manganese source is 3-6:1-3.5:1-4.

4. The method for preparing the ternary cathode material according to claim 2, characterized in that: The concentration of urea is 0.8 mol%-1.2 mol, and the concentration of polyvinylpyrrolidone is 0.08 mol%-0.12 mol.

5. The method for preparing the ternary cathode material according to claim 2, characterized in that: When the metal salt solution is mixed with the dispersant solution, the volume ratio of the metal salt solution to the dispersant solution is 1:0.8-1.

2.

6. The method for preparing the ternary cathode material according to claim 2, characterized in that: In the hollow core-shell structure of the ternary precursor, the porosity is greater than 80%, and the porosity is 30%-40%.

7. The method for preparing the ternary cathode material according to claim 1, characterized in that: The doping element is at least two of tungsten, aluminum, titanium, and boron.

8. The method for preparing the ternary cathode material according to claim 2, characterized in that: During the coating process, the coating layer is formed using oxides of at least two of the elements selected from aluminum, zirconium, and phosphorus.

9. The method for preparing the ternary cathode material according to claim 1, characterized in that: When sintering the coated precursor with a lithium source, the method includes the following steps: The temperature is raised from the first temperature to the second temperature at the first heating rate, and then kept at that temperature in an N2 atmosphere. The temperature is raised from the second temperature to the third temperature at a second heating rate, and then held at that temperature in an O2 atmosphere. Stop heating, and when the temperature drops back to the second temperature, switch back to the N2 atmosphere and cool to room temperature to complete sintering.

10. A power battery, characterized in that: Includes the ternary cathode material as described in claim 1.

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