Ternary positive electrode material, preparation method and application thereof

Abstract

This invention discloses a ternary cathode material, its preparation method, and its applications. The general chemical formula of the ternary cathode material is Li. 1+ a Ni x Co y Mn z W b B c Al d O2, where x+y+z+b+c+d=1, x>0, y>0, z>0, ‑0.05≤a≤0.1, 0

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials technology, specifically to ternary cathode materials, their preparation methods, and applications. Background Technology

[0002] Ternary layered cathode materials such as lithium nickel cobalt manganese oxide (LiCO) have become one of the most important cathode materials in the field of power batteries due to their high specific capacity and good overall performance. However, during storage and cycling, lithium ions on the surface of LiCO react with water and carbon dioxide in the air to generate lithium residues such as Li₂CO₃ and LiOH. High levels of residual lithium on the surface can lead to a series of problems, including slurry gelation, battery gas generation, and cycle life degradation.

[0003] In existing technologies, methods such as water washing are commonly used to address the aforementioned problems. However, water washing can lead to lithium loss and structural damage. Therefore, developing a method for preparing ternary cathode materials that effectively reduces surface residual lithium and significantly improves cycle stability is of significant practical importance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a ternary cathode material, its preparation method, and its application, solving the technical problems of low tap density, high surface residual lithium, and poor structural stability of existing ternary cathode materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a ternary cathode material, wherein the ternary cathode material has the general chemical formula Li. 1+ a Ni x Mn y Co z W b B c Al d O2, where x+y+z+b+c+d=1, and x>0, y>0, z>0; in the ternary cathode material, -0.05≤a≤0.1, 0<b≤0.02, 0<c≤0.01, 0<d≤0.02.

[0007] Preferably, the ternary cathode material is a single crystal or polycrystalline secondary spherical particle, and the surface of the ternary cathode material particle is provided with a coating layer, the coating layer including an amorphous Li-WO layer and a surface coating layer containing aluminum, phosphorus and lithium, the amorphous Li-WO layer is located on the side close to the ternary cathode material matrix, and the surface coating layer containing aluminum, phosphorus and lithium is located outside the amorphous Li-WO layer.

[0008] Preferably, the thickness of the amorphous Li-WO layer is 1-50 nm, more preferably 2-20 nm, and the thickness of the surface coating layer containing aluminum, phosphorus, and lithium is 1-50 nm, more preferably 2-30 nm.

[0009] Preferably, the thickness of the amorphous Li-WO layer is 1-50 nm, more preferably 2-20 nm, and the thickness of the surface coating layer containing aluminum, phosphorus, and lithium is 1-50 nm, more preferably 2-30 nm.

[0010] Preferably, the median particle size D50 of the ternary cathode material is 3-20 μm, and more preferably 5-15 μm.

[0011] Preferably, the tap density of the ternary cathode material is 2.2-2.8 g / cm³. 3 The preferred value is 2.4-2.7 g / cm³. 3 .

[0012] Preferably, the molar percentage of Ni, x, is 0.8-0.95.

[0013] Preferably, the preparation method of the ternary cathode material includes the following steps:

[0014] S1. A controlled crystallization method is used to synthesize nickel-cobalt-manganese hydroxide precursors or nickel-cobalt-manganese carbonate precursors. During the co-precipitation reaction, when the median particle size D50 reaches 50%-90% of the target particle size, organic pore fillers and inorganic mineralizers are simultaneously added to the reaction system. After the reaction, a high-density ternary precursor is obtained. The role of organic pore fillers (polyethylene glycol, polyvinyl alcohol, sucrose, glucose, etc.) is to fill the micropores between primary particles during co-precipitation. They decompose and escape during subsequent washing, drying, and pre-calcination. However, their initial "occupancy" effect makes the primary particles more compact and reduces internal pores, thereby increasing the tap density and compacted density of the precursor and the final sintered product. The role of inorganic mineralizers (ammonium fluoride, ammonium chloride, lithium fluoride, etc.) is to release the F in the mineralizer during co-precipitation and subsequent low-temperature treatment. - Cl - These agents can promote the directional rearrangement and surface dissolution-redeposition process of primary particles, resulting in more regular morphology and better crystal orientation of primary particles, thereby improving the sphericity, surface density, and tap density of secondary particles. The synergistic effect of the organic pore filler addresses the problem of "numerous internal pores," while the inorganic mineralizer addresses the problem of "irregular particle packing." Together, they achieve a high-density ternary precursor characterized by "high density + high sphericity + low internal porosity."

[0015] S2. The high-density ternary precursor is uniformly mixed with a lithium source, a tungsten-containing compound, and a boron-containing compound, and then pre-fired and sintered at high temperature in an oxygen-containing atmosphere to obtain a primary product; the role of W and B doping and the segmented process of pre-firing and high-temperature sintering: W 6+ At high temperatures, some lithium ions enter the transition metal sites of the bulk material to form weak doping, while others accumulate at the primary grain boundaries to form an amorphous Li-WO phase. This stabilizes the layered structure, reduces Li / Ni cation mixing, inhibits the initiation of grain boundary microcracks, and improves the diffusion channels of lithium ions at the grain boundaries; B 3+ During sintering, it mainly accumulates at the primary grain boundaries, acting as a flux and grain boundary modifier. This helps control the growth direction of primary grains, forming a more favorable environment for Li. + The radially arranged grains of the diffusion process reduce grain boundary defects, improving the material's structural stability and rate performance. Pre-sintering allows the lithium source to fully melt and uniformly penetrate the precursor, initially forming a layered structure, avoiding phase impurities and surface residual lithium caused by uneven lithium distribution under direct high temperatures. High-temperature sintering completes the final crystallization of the layered α-NaFeO2 structure, controls the primary particle size and morphology, and promotes the uniform distribution of W and B in the bulk / grain boundaries and the formation of the amorphous Li-WO phase. An oxygen-rich atmosphere suppresses Ni... 2+ Residue, improve Ni 3+ The ratio of cations and the reduction of cation mixing are particularly critical for high-nickel systems.

[0016] S3. The primary product is mixed with an aluminum-containing compound and a phosphorus-containing compound, and annealed at 300-600℃ to obtain the ternary cathode material. The role of Al / P annealing is that, under annealing conditions at 300-600℃, the two react in a solid-state reaction on the material surface and react with residual lithium (LiOH, Li2CO3) to generate a surface coating layer containing aluminum, phosphorus, and lithium in situ (such as lithium aluminum phosphate phase), while consuming residual lithium on the surface: ① reducing residual lithium on the surface; ② forming a protective layer to suppress electrolyte side reactions; ③ improving interfacial impedance.

[0017] Preferably, in step S1, the organic pore filler is selected from at least one of polyethylene glycol, polyvinyl alcohol, sucrose, and glucose, and its addition amount is 0.1-5 wt% of the theoretical yield of the high-density ternary precursor; and / or, the inorganic mineralizer is selected from at least one of ammonium fluoride, ammonium chloride, and lithium fluoride, and its addition amount is 0.05-1 wt% of the theoretical yield of the high-density ternary precursor.

[0018] Preferably, in S1, the pH value of the coprecipitation reaction is 10.0-12.5, the reaction temperature is 40-70℃, and the ammonia concentration is 2-20g / L.

[0019] Preferably, in step S2, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium nitrate, and the total molar ratio of lithium to transition metal is (1.02-1.10):1; the tungsten-containing compound is selected from at least one of tungsten oxide, ammonium metatungstate, and tungstic acid, and its amount added, based on tungsten element, accounts for 0.1-2 mol% of the total molar amount of transition metal; the boron-containing compound is selected from at least one of boric acid, boron oxide, and lithium borate, and its amount added, based on boron element, accounts for 0.05-1 mol% of the total molar amount of transition metal.

[0020] Preferably, in S2, the process of pre-firing followed by high-temperature sintering is as follows: first, the temperature is increased to 450-550℃ at 1-5℃ / min and held for 2-6 hours for pre-firing; then, the temperature is increased to 700-850℃ at 1-5℃ / min and held for 8-20 hours for high-temperature sintering.

[0021] Preferably, the oxygen-containing atmosphere in S2 is an oxygen atmosphere or an oxygen-enriched atmosphere with an oxygen content of not less than 80% by volume.

[0022] Preferably, in step S3, the aluminum-containing compound is selected from at least one of aluminum isopropoxide, boehmite, alumina, and aluminum nitrate; the phosphorus-containing compound is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, and lithium phosphate; and the total amount of the aluminum-containing compound and the phosphorus-containing compound added accounts for 0.1-5 wt% of the mass of the primary product.

[0023] Preferably, in the aluminum-containing compound and the phosphorus-containing compound, the molar ratio of aluminum to phosphorus is (0.5-2):1, more preferably (0.8-1.2):1.

[0024] Preferably, in step S3, the annealing process is carried out in an air atmosphere, an oxygen atmosphere, or an oxygen-enriched atmosphere, and the annealing time is 2-8 hours.

[0025] Preferably, after the S3 annealing treatment, the surface coating layer containing aluminum, phosphorus and lithium is formed on the surface of the ternary cathode material particles, and the surface coating layer containing aluminum, phosphorus and lithium together with the amorphous Li-WO layer introduced in step S2 constitutes a composite coating layer.

[0026] Compared with existing technologies, it has the following beneficial effects:

[0027] This invention improves the structural and interfacial stability of ternary cathode materials through synergistic modification of W, B, and Al, as well as surface composite coating design. Specifically, W and B elements can participate in the regulation of the bulk and surface structure of the material during the sintering process, which helps to stabilize the layered crystal structure, reduce cation mixing, improve lithium-ion diffusion channels, and enhance the material's structural retention under high voltage and long cycling conditions. After annealing, Al and P elements form a surface coating layer containing aluminum, phosphorus, and lithium on the particle surface, which can effectively isolate the active material from direct contact with the electrolyte, suppress interfacial side reactions, reduce transition metal dissolution, and improve cycle stability and thermal stability. The amorphous Li-WO layer constructed in this invention, combined with a surface coating layer containing aluminum, phosphorus, and lithium, provides gradient protection for the material surface. The amorphous Li-WO layer near the substrate helps alleviate surface stress, stabilize the particle surface lattice, and improve interfacial compatibility. The outer surface coating layer containing aluminum, phosphorus, and lithium further enhances surface chemical stability, effectively suppressing surface phase transitions, impedance growth, and microcrack propagation under high temperature and high voltage conditions. Furthermore, this invention simultaneously introduces organic pore fillers and inorganic mineralizers at specific particle size stages during precursor growth, which contributes to… The invention reduces the internal porosity of the precursor, improves particle densification and morphological uniformity, and the resulting high-density ternary precursor is more likely to form dense and uniform cathode material particles during subsequent sintering, thereby improving the tap density and compaction performance of the material and improving the volumetric energy density of the battery. The preparation method of this invention has a clear process route, controllable parameters, and is suitable for industrial scale-up. By organically combining precursor densification, W / B doping modification and Al / P annealing coating, it can improve the first efficiency, cycle life, rate performance and thermal stability without significantly sacrificing the material capacity. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a ternary cathode material includes the following steps:

[0031] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyethylene glycol (PEG-4000) at 1.0 wt% of the theoretical yield and ammonium fluoride at 0.2 wt% of the theoretical yield to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P1.

[0032] S2. P1 is mixed at high speed with LiOH·H2O (Li / M=1.05), ammonium metatungstate (W element accounts for 0.5 mol% of M), and boric acid (B element accounts for 0.2 mol% of M) until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M1.

[0033] S3. Mix M1 with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 1:1, with the total amount of the two added being 1.0 wt% of the mass of M1. Heat the mixture to 450℃ at 3℃ / min in an oxygen atmosphere and hold for 5 hours to obtain the ternary cathode material A1.

[0034] Example 2

[0035] A method for preparing a ternary cathode material includes the following steps:

[0036] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and the ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyvinyl alcohol (0.8 wt% of the theoretical yield) and ammonium chloride (0.15 wt% of the theoretical yield) to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P2.

[0037] S2. P2 is mixed with LiOH·H2O (Li / M=1.05), ammonium metatungstate (W element accounts for 0.8 mol% of M), and boric acid (B element accounts for 0.3 mol% of M) at high speed until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M2.

[0038] S3. Mix M2 with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 1.2:1, with the total amount of both added being 1.5 wt% of the mass of M2. Heat the mixture to 500℃ at 3℃ / min in an oxygen atmosphere and hold for 4 hours to obtain ternary cathode material A2.

[0039] Example 3

[0040] A method for preparing a ternary cathode material includes the following steps:

[0041] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 80% of the target particle size of 10 μm (approximately 7 μm), simultaneously add sucrose (1.5 wt% of the theoretical yield) and lithium fluoride (0.1 wt% of the theoretical yield) to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P3.

[0042] S2. P3 is mixed at high speed with LiOH·H2O (Li / M=1.06), ammonium metatungstate (W element accounts for 1 mol% of M), and boric acid (B element accounts for 0.15 mol% of M) until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M3.

[0043] S3. M3 is mixed with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 0.9:1, with the total amount of the two added being 0.8 wt% of the mass of M3. The mixture is heated to 420°C at a rate of 3°C / min and held for 6 hours in an oxygen atmosphere to obtain ternary cathode material A3.

[0044] Comparative Example 1

[0045] A method for preparing a ternary cathode material includes the following steps:

[0046] S1. A 2 mol / L metal salt solution was prepared by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. This solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia solution, was pumped into a continuous stirred tank reactor. The reaction temperature was controlled at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. The reaction proceeded until the D50 reached approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, a high-density precursor, P1, was obtained.

[0047] S2. P1 is mixed at high speed with LiOH·H2O (Li / M=1.05), ammonium metatungstate (W element accounts for 0.5 mol% of M), and boric acid (B element accounts for 0.2 mol% of M) until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M1.

[0048] S3. Mix M1 with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 1:1, with the total amount of the two added being 1.0 wt% of the mass of M1. Heat the mixture to 450℃ at 3℃ / min in an oxygen atmosphere and hold for 5 hours to obtain the ternary cathode material D1.

[0049] Comparative Example 2

[0050] A method for preparing a ternary cathode material includes the following steps:

[0051] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyethylene glycol (PEG-4000) at 1.0 wt% of the theoretical yield and ammonium fluoride at 0.2 wt% of the theoretical yield to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P1.

[0052] S2. P1 is mixed with LiOH·H2O (Li / M=1.05) at high speed until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M1.

[0053] S3. Mix M1 with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 1:1, with the total amount of the two added being 1.0 wt% of the mass of M1. Heat the mixture to 450℃ at 3℃ / min in an oxygen atmosphere and hold for 5 hours to obtain the ternary cathode material D2.

[0054] Comparative Example 3

[0055] A method for preparing a ternary cathode material includes the following steps:

[0056] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyethylene glycol (PEG-4000) at 1.0 wt% of the theoretical yield and ammonium fluoride at 0.2 wt% of the theoretical yield to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P1.

[0057] S2. P1 is mixed uniformly at high speed with LiOH·H2O (Li / M=1.05), ammonium metatungstate (W element accounts for 0.5 mol% of M), and boric acid (B element accounts for 0.2 mol% of M). Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain product D3.

[0058] Comparative Example 4

[0059] A method for preparing a ternary cathode material includes the following steps:

[0060] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyethylene glycol (PEG-4000) at 1.0 wt% of the theoretical yield and ammonium fluoride at 0.2 wt% of the theoretical yield to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P1.

[0061] S2. P1 is mixed with LiOH·H2O (Li / M=1.05) and ammonium metatungstate (W element accounts for 0.5 mol% of M) at high speed until homogeneous. Under an oxygen atmosphere (O2≥99%), it is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, crushing and sieving, the primary product M1 is obtained.

[0062] S3. Mix M1 with aluminum isopropoxide and ammonium dihydrogen phosphate at a molar ratio of Al:P = 1:1, with the total amount of the two added being 1.0 wt% of the mass of M1. Heat the mixture to 450℃ at 3℃ / min in an oxygen atmosphere and hold for 5 hours to obtain the ternary cathode material D4.

[0063] Comparative Example 5

[0064] A method for preparing a ternary cathode material includes the following steps:

[0065] S1. Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. Pump this solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia, into a continuous stirred tank reactor. Control the reaction temperature at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. When the D50 reaches 70% of the target particle size of 10 μm (approximately 7 μm), simultaneously add polyethylene glycol (PEG-4000) at 1.0 wt% of the theoretical yield and ammonium fluoride at 0.2 wt% of the theoretical yield to the reaction system. Continue the reaction until the D50 reaches approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, obtain the high-density precursor P1.

[0066] S2. P1 is mixed at high speed with LiOH·H2O (Li / M=1.05), ammonium metatungstate (W element accounts for 0.5 mol% of M), and boric acid (B element accounts for 0.2 mol% of M) until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain the primary product M1.

[0067] S3. Mix M1 with aluminum isopropoxide, adding 1.0 wt% of the mass of M1. Heat the mixture to 450°C at 3°C / min in an oxygen atmosphere and hold for 5 hours to obtain the ternary cathode material D5.

[0068] Comparative Example 6

[0069] A method for preparing a ternary cathode material includes the following steps:

[0070] S1. A 2 mol / L metal salt solution was prepared by mixing NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in a molar ratio of 88:6:6. This solution, along with 4 mol / L NaOH solution and 6 mol / L ammonia solution, was pumped into a continuous stirred tank reactor. The reaction temperature was controlled at 55℃, pH at 11.2, and ammonia concentration at 10 g / L. The reaction proceeded until the D50 reached approximately 10.5 μm. After aging, filtration, washing, and drying at 120℃, a high-density precursor, P1, was obtained.

[0071] S2. P1 is mixed with LiOH·H2O (Li / M=1.05) at high speed until homogeneous. Under an oxygen atmosphere (O2≥99%), the mixture is pre-calcined at 500℃ for 4 hours at a rate of 3℃ / min, then at 780℃ for 15 hours at a rate of 3℃ / min. After natural cooling, the mixture is crushed and sieved to obtain product D6.

[0072] The performance of the ternary cathode materials prepared in the examples and comparative examples was tested, as detailed below:

[0073] 1. Physical characterization: D50 (laser particle size analyzer), tap density (GB / T5162), surface residual lithium (titration method, to determine the total amount of LiOH and Li2CO3, in wt%).

[0074] 2. Electrochemical test: Assemble a CR2032 coin cell with the positive electrode composed of NCM:SP:PVDF=96:2:2, lithium metal as the counter electrode, and 1mol / L LiPF6 electrolyte with EC / DMC / EMC (1:1:1, v / v).

[0075] First charge / discharge: 2.8-4.3V, 0.1C; Room temperature cycling: 25℃, 1C / 1C, 2.8-4.3V, 100 cycles; High temperature cycling: 45℃, 1C / 1C, 2.8-4.3V, 100 cycles; Rate of discharge: 0.2C / 0.5C / 1C / 2C / 5C.

[0076] The ternary cathode materials prepared in the examples and comparative examples were used to assemble batteries, and the performance of the batteries was tested as follows: The cathode materials prepared in the above examples and comparative examples were mixed with conductive agent acetylene black and binder PVDF at a mass ratio of 96:2:2 to form a slurry, which was then coated on aluminum foil to prepare a cathode sheet. Using lithium metal sheets as the negative electrode, CR2032 coin cells were assembled in an argon-protected glove box. The initial discharge specific capacity, 100-cycle capacity retention, and rate capability of the batteries were tested.

[0077] The following table shows the data results:

[0078] Table 1 Physical Parameters

[0079] sample D50(μm) Tap density (g / cm³) Surface residual lithium (wt%) Example 1 10.8 2.56 0.31 Example 2 11.2 2.52 0.29 Example 3 10.5 2.60 0.33 Comparative Example 1 10.9 2.33 0.38 Comparative Example 2 10.7 2.47 0.62 Comparative Example 3 10.8 2.49 0.85 Comparative Example 4 10.8 2.51 0.36 Comparative Example 5 10.7 2.53 0.55 Comparative Example 6 10.6 2.28 0.92

[0080] Table 2 Electrochemical Performance

[0081] sample First discharge specific capacity (mAh / g) First effect 25℃ 100-week capacity retention (%) 45℃ 100-week capacity retention (%) 5C / 0.2C (%) Example 1 210.3 88.9 93.8 88.1 86.2 Example 2 206.8 89.3 94.5 89.0 87.1 Example 3 212.1 88.5 93.2 87.4 86.5 Comparative Example 1 208.4 88.2 89.6 82.5 81.7 Comparative Example 2 204.9 87.8 88.7 80.9 80.3 Comparative Example 3 207.2 88.0 87.9 79.8 80.6 Comparative Example 4 208.7 88.3 91.2 84.3 82.8 Comparative Example 5 207.5 87.9 90.8 83.6 82.1 Comparative Example 6 203.6 87.4 83.5 74.6 76.6

[0082] Table 3 High Temperature Storage Performance

[0083] sample Capacity retention rate (%) Capacity recovery rate (%) DCR growth rate (%) Example 1 95.1 97.8 12.8 Example 2 95.6 98.1 11.9 Example 3 94.8 97.5 13.4 Comparative Example 1 91.7 95.2 19.6 Comparative Example 2 90.9 94.6 21.4 Comparative Example 3 90.2 93.8 22.1 Comparative Example 4 92.5 95.7 17.5 Comparative Example 5 91.8 95.0 18.9 Comparative Example 6 87.6 91.3 28.9

[0084] Results analysis:

[0085] 1. Tap density: The tap density of Examples A1-A3 is ≥2.52 g / cm³. 3 The density of particles S1 was significantly higher than that of D1 (2.33 g / cm³) and D6 (2.28 g / cm³) without precursor densification, proving that the simultaneous introduction of organic pore filler and inorganic mineralizer in S1 can significantly improve particle density, which is consistent with the expectations of the invention.

[0086] 2. Regarding residual lithium on the surface: The residual lithium on the surface of Examples 1-A and Example 3 was ≤0.33wt%, which was much lower than that of Comparative Example 3 (0.85wt%) and Comparative Example 6 (0.92wt%) without Al / P annealing. This proves that the Al / P annealing treatment in S3 can effectively consume residual lithium on the surface and form a coating layer in situ. It is worth noting that the residual lithium of Comparative Example 5 (Al only, without P) was 0.55wt%, which was significantly higher than that of Example 1 (0.31wt%). This indicates that phosphorus-containing compounds play a more important role in consuming residual lithium on the surface, verifying the advantage of "Li-Al-P surface coating layer" over "single Al2O3 coating".

[0087] 3. Cyclic stability: The retention rate of Example 4 at 45℃ for 100 cycles reached 87.4%-89.0%, significantly better than the comparative examples. Among them, Comparative Example 2 (without W / B) showed the largest decrease, indicating that W / B doping plays a key role in suppressing structural degradation during cycling; Comparative Example 4 (W only, without B) had a retention rate of 84.3%, which is between Example 1 (88.1%) and Comparative Example 2 (80.9%), indicating that there is a synergistic effect between B and W elements in terms of structural stability.

[0088] 4. High-temperature storage: The DCR growth rate of Examples 1-3 is ≤13.4%, which is much lower than the 28.9% of Comparative Example 6. This indicates that the composite coating structure composed of the Li-WO inner layer and the Li-Al-P outer layer can effectively suppress interfacial side reactions under high-temperature conditions, which is consistent with the "gradient protection" mechanism.

[0089] 5. Synergistic effect: Comparative Example 6 had the worst overall performance. The individual modification schemes (Comparative Examples 1-5) were all between Example 1 and Comparative Example 6, which proves that the comprehensive effect produced by the synergy of the three elements of "precursor densification + W / B co-doping + Li-Al-P annealing coating" in this invention is not a simple superposition of the individual methods, but rather there is a significant synergistic enhancement effect.

[0090] The present invention has been illustrated with the above embodiments to describe the detailed process flow of the present invention. However, the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A ternary cathode material, characterized in that, The ternary cathode material has the general chemical formula Li. 1+ a Ni x Mn y Co z W b B c Al d O2, where x+y+z+b+c+d=1, and x>0, y>0, z>0; in the ternary cathode material, -0.05≤a≤0.1, 0<b≤0.02, 0<c≤0.01, 0<d≤0.

02.

2. The ternary cathode material according to claim 1, characterized in that, The ternary cathode material is a single crystal or polycrystalline secondary spherical particle. The surface of the ternary cathode material particle is provided with a coating layer, which includes an amorphous Li-WO layer and a surface coating layer containing aluminum, phosphorus and lithium. The amorphous Li-WO layer is located on the side close to the ternary cathode material matrix, and the surface coating layer containing aluminum, phosphorus and lithium is located outside the amorphous Li-WO layer.

3. The ternary cathode material according to claim 2, characterized in that, The thickness of the amorphous Li-WO layer is 1-50 nm, preferably 2-20 nm, and the thickness of the surface coating layer containing aluminum, phosphorus, and lithium is 1-50 nm, preferably 2-30 nm.

4. The ternary cathode material according to claim 1, characterized in that, The median particle size D50 of the ternary cathode material is 3-20 μm, preferably 5-15 μm.

5. The ternary cathode material according to claim 1, characterized in that, The tap density of the ternary cathode material is 2.2-2.8 g / cm³, preferably 2.4-2.7 g / cm³.

6. The ternary cathode material according to claim 1, characterized in that, The molar percentage of Ni, x, is 0.8-0.

95.

7. A method for preparing a ternary cathode material according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Nickel cobalt manganese hydroxide precursor or nickel cobalt manganese carbonate precursor is synthesized by controlled crystallization. During the coprecipitation reaction, when the median particle size D50 of the particles reaches 50%-90% of the target particle size, organic pore filler and inorganic mineralizer are added to the reaction system simultaneously. After the reaction is completed, a high-density ternary precursor is obtained. S2. The high-density ternary precursor is uniformly mixed with a lithium source, a tungsten-containing compound and a boron-containing compound, and then pre-fired and sintered at high temperature in an oxygen-containing atmosphere to obtain a primary product. S3. The primary product is mixed with an aluminum-containing compound and a phosphorus-containing compound, and annealed at 300-600°C to obtain the ternary cathode material.

8. The preparation method according to claim 7, characterized in that, In step S1, the organic pore filler is selected from at least one of polyethylene glycol, polyvinyl alcohol, sucrose, and glucose, and its addition amount is 0.1-5 wt% of the theoretical yield of the high-density ternary precursor; and / or, the inorganic mineralizer is selected from at least one of ammonium fluoride, ammonium chloride, and lithium fluoride, and its addition amount is 0.05-1 wt% of the theoretical yield of the high-density ternary precursor.

9. The preparation method according to claim 7, characterized in that, In S1, the pH value of the coprecipitation reaction is 10.0-12.5, the reaction temperature is 40-70℃, and the ammonia concentration is 2-20g / L.

10. The preparation method according to claim 7, characterized in that, In S2, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium nitrate, and the total molar ratio of lithium to transition metal is (1.02-1.10):1; the tungsten-containing compound is selected from at least one of tungsten oxide, ammonium metatungstate, and tungstic acid, and its amount added, based on tungsten element, accounts for 0.1-2 mol% of the total molar amount of transition metal; the boron-containing compound is selected from at least one of boric acid, boron oxide, and lithium borate, and its amount added, based on boron element, accounts for 0.05-1 mol% of the total molar amount of transition metal.

11. The preparation method according to claim 7, characterized in that, In S2, the process of pre-firing followed by high-temperature sintering is as follows: first, the temperature is increased to 450-550℃ at 1-5℃ / min and held for 2-6 hours for pre-firing; then, the temperature is increased to 700-850℃ at 1-5℃ / min and held for 8-20 hours for high-temperature sintering.

12. The preparation method according to claim 7, characterized in that, The oxygen-containing atmosphere in S2 is an oxygen atmosphere or an oxygen-enriched atmosphere with an oxygen content of not less than 80% by volume.

13. The preparation method according to claim 7, characterized in that, In S3, the aluminum-containing compound is selected from at least one of aluminum isopropoxide, boehmite, alumina, and aluminum nitrate; the phosphorus-containing compound is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, and lithium phosphate; and the total amount of the aluminum-containing compound and the phosphorus-containing compound is 0.1-5 wt% of the mass of the primary product.

14. The preparation method according to claim 13, characterized in that, In the aluminum-containing compound and the phosphorus-containing compound, the molar ratio of aluminum to phosphorus is (0.5-2):1, preferably (0.8-1.2):

1.

15. The preparation method according to claim 7, characterized in that, In step S3, the annealing process is carried out in an air atmosphere, an oxygen atmosphere, or an oxygen-enriched atmosphere, and the annealing time is 2-8 hours.

16. The preparation method according to claim 7, characterized in that, After the S3 annealing treatment, a surface coating layer containing aluminum, phosphorus and lithium is formed on the surface of the ternary cathode material particles, and the surface coating layer containing aluminum, phosphorus and lithium together with the amorphous Li-WO layer introduced in step S2 constitutes a composite coating layer.

17. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes the ternary positive electrode material according to any one of claims 1-6.