Ternary positive electrode material, preparation method thereof, positive electrode sheet and lithium ion battery

Abstract

The application discloses a ternary positive electrode material and a preparation method thereof, a positive electrode sheet and a lithium ion battery, and relates to the technical field of lithium ion batteries.The sum Y of the products of the valence of the element M and the mole proportion of the element M in the ternary positive electrode material provided by the application is 0.01-0.15, which ensures that the charge compensation mechanism of the doped element is in the best state, inhibits the cation mixing (especially Li + / Ni 2+ ), and avoids the introduction of too many defects due to excessive doping, thereby achieving the best balance between structural stability and lithium ion diffusion kinetics, making the ternary positive electrode material have lower impedance, achieving the purpose of fast charging and low impedance, and better structural stability being conducive to ensuring the service life.

Description

Technical Field

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

[0002] As a highly efficient electrochemical energy storage device, the performance of lithium-ion batteries hinges on the cathode material. Layered high-nickel ternary materials (LiNi) are particularly important. x Co y Mn z O2 (x>0.5) exhibits high specific capacity (>190mAh / g) and superior rate performance. With breakthroughs in fast charging infrastructure and fast charging cell technology, the demand for fast charging is increasing. However, fast charging cells exceeding 4C generate excessive heat, leading to a deterioration in their lifespan. This excessive heat generation problem is particularly pronounced in high-nickel ternary cathode materials. Therefore, it is necessary to reduce the heat generated during fast charging, which can be achieved by reducing the direct current resistance (DCR) during the fast charging process.

[0003] The current methods to reduce DCR are mainly: (1) reducing the sintering temperature to achieve grain refinement and reduce DCR, but grain refinement will result in a higher specific surface area, worsening the degree of side reaction and thus reducing the lifetime; (2) using fast ion conductor coating or electronic conductor coating to reduce DCR, but conductor coating often improves the extent or causes different degrees of capacity decay.

[0004] Therefore, there is an urgent need to improve ternary cathode materials to achieve fast charging with low impedance and low surface side reactions, thereby enabling long-life fast charging applications.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide ternary cathode materials and their preparation methods, cathode sheets, and lithium-ion batteries, aiming to achieve fast charging and low impedance while ensuring service life.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a ternary cathode material with the chemical formula Li. 1+x Ni a Co b Mn c M d O2; Where a+b+c+d=1, a is 0.50-0.90, b is 0.05-0.20, c is 0.05-0.35, d is 0.004-0.040, and x is 0.01-0.08; Element M is a combination of two to eight elements selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce, and Mg, where the molar percentage of each element in the total amount of nickel, cobalt, manganese, and M is M. i The stable oxidation state of each element in the compound is N. i Y=ΣM i ×N i And Y satisfies: 0.01≤Y≤0.15.

[0008] In an optional embodiment, the lithium-ion diffusion coefficient of the ternary cathode material is 10. -11 -10 -7 cm 2 The formula for calculating the lithium-ion diffusion coefficient is as follows: / s ; In the formula, m B This indicates the number of moles, expressed in mol. V m The molar volume of the electrode material is expressed in m³. 3 / mol; S represents the electrode / electrolyte contact area, in m². 2 ; Δ E s This represents the total voltage change caused by the pulse, expressed in V. Δ E τ This represents the voltage change during constant current charging and discharging, with the unit being V; τ This represents the relaxation time, measured in seconds (s).

[0009] In an optional embodiment, the crystallinity ratio of the ternary cathode material is 0.02-0.06, and the formula for calculating the crystallinity ratio is as follows: Crystallinity ratio = D1 / D2; In the formula, D1 represents the grain size of the (003) crystal plane in XRD, in nm; D2 represents the average size of primary particles in SEM, in nm.

[0010] In an optional implementation, the roundness of the ternary cathode material is 0.5-0.9, and the roundness is calculated as follows: Roundness = (4π × s) / c 2 ; In the formula, s represents the cross-sectional area of ​​the ternary cathode material, with units of μm. 2 ; c represents the cross-sectional perimeter of the ternary cathode material, in μm.

[0011] In a second aspect, the present invention provides a method for preparing any of the ternary cathode materials in the foregoing embodiments, comprising: mixing a nickel-cobalt-manganese precursor with a first M source and sintering at a first sintering temperature to obtain a pre-sintered material; The pre-burned material and lithium source are mixed and sintered at a second sintering temperature to obtain the sintered material; After the sintered material is crushed, single-crystal materials with a particle size of 2.0μm-4.5μm are obtained; The single crystal material is mixed with the second M source and sintered at the third sintering temperature. The second sintering temperature is greater than the first sintering temperature, and the second sintering temperature is greater than the third sintering temperature.

[0012] In an optional embodiment, the metal elements in the first M source and the second M source are each independently selected from two to eight combinations of elements selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Y, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce and Mg. And / or, the first M source and the second M source are each independently selected from at least one of oxides, carbonates, phosphates, nitrates and lithium-containing complex oxides; And / or, the molar ratio of the total amount of metal elements in the first M source and the second M source is 1:(0.4-3). And / or, during the preparation of the pre-sintered material, the sintering atmosphere is air or oxygen, the sintering temperature is controlled at 350℃-750℃, and the sintering time is 4h-20h; preferably, the sintering temperature is controlled at 500℃-700℃, and the sintering time is 4h-10h. And / or, the particle size D50 of the nickel-cobalt-manganese precursor is 2.0 μm - 4.5 μm; And / or, the BET of the nickel-cobalt-manganese precursor is 5m. 2 / g-20m 2 / g; And / or, the whisker thickness of the nickel-cobalt-manganese precursor is 0.1 μm - 1.5 μm.

[0013] In an optional embodiment, during the process of preparing the sintered material from the pre-sintered material, the sintering temperature is controlled at 750℃-1050℃ and the sintering time is controlled at 6h-16h; preferably, the sintering temperature is controlled at 850℃-1000℃ and the sintering time is controlled at 10h-15h. And / or, during the preparation of sintered products from pre-sintered products, the sintering atmosphere requires an oxygen volume fraction greater than 90%; And / or, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is controlled to be (1.00-1.08):1, preferably (1.02-1.08):1; And / or, the lithium source is selected from at least one of lithium hydroxide monohydrate, lithium carbonate, lithium oxide, and lithium hydroxide.

[0014] In an optional embodiment, the single crystal material is mixed with the second M source and sintered in an oxygen-containing atmosphere at a sintering temperature of 300℃-750℃ for 3h-15h; preferably, the sintering temperature is 400℃-750℃ and the sintering time is 5h-12h. Preferably, the oxygen volume fraction in the oxygen-containing atmosphere is greater than 90%.

[0015] Thirdly, the present invention provides a positive electrode sheet, comprising any of the ternary positive electrode materials in the foregoing embodiments or ternary positive electrode materials prepared by any of the preparation methods in the foregoing embodiments.

[0016] Fourthly, the present invention provides a lithium-ion battery, including the positive electrode sheet of the aforementioned embodiments.

[0017] The present invention has the following beneficial effects: In the ternary cathode material provided by the present invention, the sum of the products of the valence state of element M and the molar proportion of element M is 0.01-0.15, ensuring that the charge compensation mechanism of the doping element is in the optimal state, thus suppressing cation mixing (especially Li). + / Ni 2+ This approach avoids introducing too many defects due to excessive doping, thus achieving the best balance between structural stability and lithium-ion diffusion kinetics. This results in ternary cathode materials having lower impedance, enabling fast charging with low impedance, while better structural stability helps ensure service life. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 SEM image of the ternary cathode material obtained in Example 1; Figure 2 The number and particle size distribution diagram of the ternary cathode material obtained in Example 1; Figure 3 The XRD pattern of the ternary cathode material obtained in Example 1; Figure 4SEM images of the ternary cathode material were obtained for Comparative Example 1; Figure 5 The number particle size distribution of the ternary cathode material was obtained as a comparative example 1. Detailed Implementation

[0020] 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 will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0021] To address the issue that ternary cathode materials cannot simultaneously achieve fast charging, low impedance, and long lifespan, this invention provides a ternary cathode material that can achieve a balance between structural stability and lithium-ion diffusion kinetics, thus achieving both fast charging, low impedance, and long lifespan.

[0022] The chemical formula of the ternary cathode material provided in this embodiment of the invention is Li 1+x Ni a Co b Mn c M d O2; where a+b+c+d=1, a is 0.50-0.90, such as 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, etc.; b is 0.05-0.20, such as 0.05, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20, etc.; c is 0.05-0.35, such as 0.05, 0.10, 0. 15, 0.20, 0.25, 0.30, 0.35, etc.; d is 0.004-0.040, such as 0.004, 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, etc.; x is 0.01-0.08, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, etc. a, b, c, d, and x can also be any value between the above adjacent values.

[0023] Element M is a combination of two to eight elements selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce, and Mg. It can be a combination of three, four, five, six, seven, or eight elements, etc. The molar percentage of each element in the total amount of nickel, cobalt, manganese, and M in the combination is M. i The stable oxidation state of each element in the compound is N.i M i and N i The sum of the products of is Y, that is, Y = ΣM i ×N i And Y satisfies: 0.01≤Y≤0.15. Specifically, the value of Y can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, etc., or any value between the above adjacent values. In the ternary cathode material provided by the embodiments of the present invention, the sum of the product of the valence state of element M and the molar proportion of element M is 0.01-0.15, ensuring that the charge compensation mechanism of the doped element is in the optimal state, which suppresses cation mixing (especially Li). + / Ni 2+ This approach avoids introducing too many defects due to excessive doping, thus achieving the best balance between structural stability and lithium-ion diffusion kinetics, which is beneficial for achieving fast charging and low impedance without affecting service life.

[0024] Stable oxidation states of different elements (N) in compounds i The following values ​​are used: Zr is +4, Sr is +2, Ni is +(2, 3), Co is +2, Mn is +(2, 4, 7), Al is +3, Ti is +4, Mo is +6, Nb is +5, W is +6, Ca is +2, Na is +1, Sb is +(3, 5), Cu is +(1, 2), Fe is +(2, 3), Ta is +5, Ce is +4, and Mg is +2. When calculating the Y value, it is based on the valence state of the additive compounds added during the preparation process. For example, the valence state corresponding to the addition of CuO is Cu. 2+ The oxidation state corresponding to the addition of Cu₂O is Cu. 1+ .

[0025] In some embodiments, the lithium-ion diffusion coefficient of the ternary cathode material is 10. -11 -10 -7 cm 2 / s, such as 1×10 -11 cm 2 / s, 5×10 -11 cm 2 / s, 1×10 -10 cm 2 / s, 5×10 -10 cm 2 / s, 1×10 -9 cm 2 / s, 5×10 -9 cm 2 / s, 1×10-8 cm 2 / s, 5×10 -8 cm 2 / s, 1×10 -7 cm 2 / s, etc., can also be any value between the above adjacent values. Based on controlling the Y value, the lithium-ion diffusion coefficient can be further controlled within the above range to achieve high-rate charging and discharging. The formula for calculating the lithium-ion diffusion coefficient is as follows: ; In the formula, m B This indicates the number of moles, expressed in mol. V m The molar volume of the electrode material is expressed in m³. 3 / mol; S represents the electrode / electrolyte contact area, in m². 2 ; Δ E s This represents the total voltage change caused by the pulse, expressed in V. Δ E τ This represents the voltage change during constant current charging and discharging, with the unit being V; τ This indicates the relaxation time, measured in seconds (s).

[0026] In some embodiments, the crystallinity ratio of the ternary cathode material is 0.02-0.06, such as 0.02, 0.03, 0.04, 0.05, 0.06, etc., or any value between these adjacent values. The formula for calculating the crystallinity ratio is as follows: Crystallinity ratio = D1 / D2; In the formula, D1 represents the grain size of the (003) crystal plane in XRD, in nm; D2 represents the average size of primary particles in SEM, in nm.

[0027] The crystallinity ratio is calculated by the ratio of the (003) grain size in XRD to the primary particle size in SEM. If the crystallinity ratio is within the above range, it proves that each primary particle visible in SEM is a highly crystalline single crystal with no internal grain boundaries. This ensures that all particles have a uniform lithium-ion migration rate and structural stability.

[0028] In some embodiments, the roundness of the ternary cathode material is 0.5-0.9, such as 0.5, 0.6, 0.7, 0.8, 0.9, etc., or any value between these adjacent values. The formula for calculating the roundness is as follows: Roundness = (4π × s) / c 2 ; In the formula, s represents the cross-sectional area of ​​the ternary cathode material, with units of μm. 2 ; c represents the cross-sectional perimeter of the ternary cathode material, in μm.

[0029] It should be noted that the roundness of ternary cathode material refers to the roundness of the particles in the ternary cathode material. A roundness of 0.5-0.9 means that the particle surface is smooth and has few defects, which can reduce the impedance of the passivation film (CEI film) formed by the side reaction at the electrode / electrolyte interface, which is conducive to the rapid exchange of lithium ions on the surface and further improves the fast charging performance of the battery.

[0030] This invention also provides a method for preparing a ternary cathode material. The staged sintering process (pre-sintering → high-temperature sintering (or high-temperature crystallization) → low-temperature sintering (or low-temperature annealing)) ensures sufficient crystal growth, uniform element distribution, and controllable surface state. This method can produce single-crystal cathode materials with high lithium-ion diffusion coefficients and high crystallinity ratios. Testing shows that the prepared ternary cathode material meets the requirements for fast charging and low impedance, while also achieving long-life fast charging. The steps of the preparation method provided in this invention are as follows: S1, Pre-sintering The nickel-cobalt-manganese precursor is mixed with a first M source and sintered at a first sintering temperature to obtain a pre-sintered product A. The M source is added in two steps, S1 and S4. In step S1, the first M source forms an internal dopant, and in step S4, the second M source forms a surface coating.

[0031] Specifically, the nickel-cobalt-manganese precursor is nickel-cobalt-manganese hydroxide, which can be a commercially available material or synthesized independently through co-precipitation. The molar ratio of nickel, cobalt, and manganese meets the requirements of the nickel-cobalt-manganese ratio in the product's chemical formula.

[0032] In some embodiments, the metal element in the first M source is selected from two to eight element combinations selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce, and Mg, such as a combination of three, four, five, six, seven, or eight elements. The first M source is selected from at least one of oxides, carbonates, phosphates, nitrates, and lithium-containing composite oxides, and the first M source can be any one or more of the above.

[0033] Furthermore, after the nickel-cobalt-manganese precursor is uniformly mixed with the first M source, it is placed in a box furnace for sintering. The sintering atmosphere is air or oxygen, and the sintering temperature (i.e., the first sintering temperature) is controlled at 350℃-750℃, such as 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, etc., preferably 500℃-700℃; the sintering time is controlled at 4h-20h, such as 4h, 5h, 8h, 10h, 13h, 15h, 18h, 20h, etc., preferably 4h-10h.

[0034] Furthermore, the particle size D50 (the particle size corresponding to 50% of the cumulative volume distribution in the volumetric particle size distribution curve) of the nickel-cobalt-manganese precursor is 2.0 μm-4.5 μm, such as 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, etc.; the BET of the nickel-cobalt-manganese precursor is 5 μm. 2 / g-20m 2 / g, such as 5m 2 / g、8m 2 / g, 10m 2 / g、13m 2 / g, 15m 2 / g、18m 2 / g、20m 2 / g, etc.; the whisker thickness of the nickel-cobalt-manganese precursor is 0.1μm-1.5μm, such as 0.1μm, 0.3μm, 0.5μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm, etc. "Whisker thickness" refers to the stacking thickness of the precursor in a certain direction of the wafer, which can be manually measured using NanoMeasurer software.

[0035] S2, High-temperature sintering The pre-calcined material and lithium source are mixed evenly, and the resulting mixture is placed in an atmosphere furnace and sintered at a high temperature at a second sintering temperature to obtain the sintered material (single crystal material B). The second sintering temperature is higher than the first sintering temperature.

[0036] In some embodiments, during the high-temperature sintering process, the sintering temperature is controlled at 750℃-1050℃, such as 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, etc., preferably 850℃-1000℃; the sintering time is 6h-16h, such as 6h, 8h, 10h, 12h, 15h, etc., preferably 10h-15h.

[0037] Furthermore, during the process of preparing sintered materials from pre-burned materials, the sintering atmosphere requires an oxygen volume fraction greater than 90%, such as a pure oxygen atmosphere, but not limited to this.

[0038] Furthermore, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, and manganese in the pre-calcined product is controlled to be (1.00-1.08):1, such as 1.00:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, etc., preferably (1.02-1.08):1. The lithium source is selected from at least one of lithium hydroxide monohydrate, lithium carbonate, lithium oxide, and lithium hydroxide, and the lithium source can be any one or more of the above.

[0039] S3, Broken The sintered material obtained in step S2 is crushed to obtain single-crystal material C with a particle size of 2.0μm-4.5μm. Specifically, particle size refers to the average particle size D50, and the particle size can be 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm, etc. The crushing method is not limited, as long as the particle size meets the requirements after crushing.

[0040] S4, Low-temperature sintering The single-crystal material is uniformly mixed with a second M source and then sintered at a low temperature in a box furnace at a third sintering temperature. The second sintering temperature is higher than the third sintering temperature. Low-temperature sintering can further improve other electrical properties, and different additives can be applied depending on the desired effect.

[0041] In some embodiments, the metal element in the second M source is selected from two to eight element combinations chosen from Zr, Sr, Ni, Co, Mn, Al, Ti, Y, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce, and Mg, such as combinations of three, four, five, six, seven, or eight elements. The second M source is selected from at least one of oxides, carbonates, phosphates, nitrates, and lithium-containing composite oxides, and the second M source can be any one or more of the above. The molar ratio of the total metal elements in the first M source and the second M source is 1:(0.4-3), such as 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.5, 1:2.0, 1:3.0, etc. By adjusting the amount of the first M source and the second M source, the amount of M elements in the internal doping and surface coating of the ternary cathode material can be controlled. Within this range, it is beneficial to further improve the electrochemical performance of the battery. In the target product Li... 1+x Ni a Co b Mn c M d In O2, the amount of M refers to the total amount of metallic elements in the first M source and the second M source.

[0042] In some embodiments, after the single-crystal material is uniformly mixed with the second M source, it is sintered at a low temperature in an oxygen-containing atmosphere. The sintering temperature is 300℃-750℃, such as 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, etc., preferably 400℃-750℃; the sintering time is 3h-15h, such as 3h, 5h, 8h, 10h, 13h, 15h, etc., preferably 5h-12h. The oxygen volume fraction in the oxygen-containing atmosphere is greater than 90%, such as a pure oxygen atmosphere, but not limited to this.

[0043] The method for preparing ternary cathode materials provided in this invention has the following advantages: (1) This invention combines the relationship between the metal valence state and molar ratio of the initiator M source to regulate the precursor index (D50 is 2.5μm-4.5μm, BET is 5m). 2 / g-20m 2 With a grain size of / g and a whisker thickness of 0.5μm-1.5μm, materials with high roundness, low aspect ratio, and high crystallinity can be obtained. (2) By controlling the precursor parameters (D50 is 2.5-4.5μm, BET is 5-20 and whisker thickness is 0.5μm-1.5μm, etc.) and constructing the relationship between the metal valence state of the structure guide M source and its molar ratio in the ternary cathode material (i.e., the sum of element valence state × molar ratio of M combination is in the range Y of 0.01-0.15), and combining it with three-step sintering, a high crystallinity single crystal material can be obtained. It has the dual advantages of low impedance and low side reaction brought about by high ion diffusion coefficient and low surface roughness, which makes it have good advantages of low temperature rise and long life in fast charging cell applications.

[0044] (3) Through the synergistic improvement of the entire chain from composition design (M combination and Y value) → structural control (diffusion coefficient, crystallinity ratio, roundness) → process realization (three-step sintering), a single-crystal ternary cathode material with high safety, long life, good fast charging performance and excellent consistency was finally obtained. The process method provided by this invention is simple and easy to implement, has low manufacturing cost and good reproducibility, and is convenient for large-scale industrial production.

[0045] This invention provides a positive electrode sheet, including the above-mentioned ternary positive electrode material, and may also include a positive electrode current collector. A positive electrode active coating is formed on at least one surface of the positive electrode current collector, and the ternary positive electrode material exists in the positive electrode active coating as a positive electrode active material.

[0046] This invention also provides a lithium-ion battery, including the above-mentioned positive electrode, and may further include a negative electrode, electrolyte, separator, etc. to form a complete battery structure.

[0047] Specifically, there are no restrictions on the specific types of negative electrode plates, electrolytes, and diaphragms.

[0048] This invention provides a device including the aforementioned lithium-ion battery. The lithium-ion battery can serve as a power source for the device or as an energy storage unit. This device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0049] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0050] The ternary cathode materials obtained in the examples and comparative examples were respectively prepared into coin cells and pouch cells, and their electrochemical performance was tested.

[0051] Test Method: Using lithium metal sheets as the counter electrode, ternary cathode materials, commonly used electrolytes, and double-sided ceramic-coated separators, coin cells were assembled in an argon-filled glove box. The coin cells were subjected to electrical performance testing. Capacity testing was conducted at a 0.1C rate at 25℃, with a charge / discharge range of 2.8–4.4V. Soft-pack preparation: Ternary cathode materials were mixed with conductive agents and binders to form a slurry (mass ratio of ternary cathode material, conductive agent, and binder was 95:2:3). The anode was prepared by mixing graphite, conductive agents (CNTs, etc.), binders (SBR), and thickeners (CMC) in deionized water (mass ratio of graphite, conductive agent, binder, and thickener was 95.5:1.5:1.5:1.5), using an aqueous process, with a solid content of approximately 52%. Coating: The slurry was uniformly coated onto the current collector (aluminum foil for the cathode, copper foil for the anode), with a thickness deviation ≤3μm. Drying: Segmented heating drying, positive electrode temperature 80°C→100°C→120°C, negative electrode temperature controlled below 80°C. Rolling: Controlled compaction density, positive electrode 3.4-3.8 g / cm³, negative electrode 1.5-1.7 g / cm³. Die-cutting: negative electrode dimension is more than 1.5 mm wider than positive electrode, with a length allowance ≥2 mm to prevent edge lithium plating. Testing conditions for soft-pack: 45°C, 1C rate cycle test (charge / discharge range 2.8V-4.4V).

[0052] Roundness: Roundness was tested using AI measurement software (purchased from Shenzhen Shenshi Company), and the calculation logic formula is as described above.

[0053] Lithium-ion diffusion coefficient: obtained by GITT test, which consists of a series of "pulse + constant current + relaxation" and is calculated using the above formula.

[0054] Crystallinity ratio: The ratio of the grain size obtained through XRD refinement to the average particle size of a single particle obtained through SEM.

[0055] Table 1. Parameters and performance test results of the ternary cathode materials obtained in the examples and comparative examples.

[0056] As can be seen from Table 1, the embodiment exhibits superior capacity and cycle performance, while having a low DCR, which meets the requirements for application in fast charging scenarios.

[0057] The preparation methods of the ternary cathode materials provided in the embodiments and comparative examples are described below.

[0058] Example 1 This embodiment provides a ternary cathode material and its preparation method, including the following steps: Step (1): Mix 1 kg of nickel-cobalt-manganese precursor, 3 g of zirconium oxide (ZrO2), 1 g of titanium oxide (TiO2), and 1 g of yttrium oxide (Y2O3), and sinter in an air atmosphere in a box furnace at 550°C for 4 h to obtain pre-calcined product A. The chemical formula of the nickel-cobalt-manganese precursor is Ni. 0.6 Co 0.2 Mn 0.2 (OH)2, particle size D50 is 3.8 μm, BET is 8 μm 2 / g, whisker thickness is 0.5μm.

[0059] Step (2): Mix the obtained pre-calcined material and lithium source evenly, wherein the lithium source is lithium hydroxide monohydrate, and the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is 1.03:1. Place the obtained mixture in a box furnace and sinter at 890℃ for 12h, keeping the oxygen concentration >90%, to obtain single crystal material B.

[0060] Step (3): The single crystal material obtained above is subjected to air jet milling, and the D50 is controlled at 2.6-2.7μm to obtain single crystal material C.

[0061] Step (4): Mix 1 kg of single crystal material C, 1.44 g of alumina (Al2O3, the same below) and 1.66 g of titanium oxide (TiO2, the same below) with a mixer, place them in a box furnace, keep the oxygen concentration >90%, and sinter at 400℃ for 4 hours to obtain fast-charging single crystal material with high roundness and high ion diffusion.

[0062] Depend on Figures 1-3 It can be seen that the cathode material particles have a high degree of single crystallization, are ellipsoidal in shape, and exhibit relatively rounded and well-dispersed characteristics. This is due to the Ti... 4+ and Y 3+The synergistic effect of metal ions inhibits the growth of high surface energy crystal planes, resulting in a small aspect ratio in single crystals. Furthermore, Zr... 4+ The introduction of these elements has the effect of refining the grains and improving the crystallinity of the crystal. The synergistic effect of these three elements can effectively stabilize lattice oxygen, reduce oxygen release during charging and discharging, and improve structural stability.

[0063] Example 2 This embodiment provides a ternary cathode material and its preparation method, including the following steps: Step (1): Mix 1 kg of nickel-cobalt-manganese precursor, 2 g of zirconium oxide, 1 g of alumina, and 3 g of titanium oxide using a mixer, and then sinter the mixture in an air atmosphere in a box furnace at 550°C for 4 h to obtain pre-sintered product A. The chemical formula of the nickel-cobalt-manganese precursor is Ni 0.6 Co 0.2 Mn 0.2 (OH)2, particle size D50 is 3.8 μm, BET is 8 μm 2 / g, whisker thickness is 0.5μm.

[0064] Step (2): Mix the obtained pre-calcined material and lithium source evenly, wherein the lithium source is lithium carbonate, and the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is 1.03:1. Place the obtained mixture in a box furnace and sinter at 890℃ for 12h, keeping the oxygen concentration >90%, to obtain single crystal material B.

[0065] Step (3): The single crystal material obtained above is subjected to air jet milling, and the D50 is controlled at 2.6-2.7μm to obtain single crystal material C.

[0066] Step (4): Mix 1 kg of single crystal material C, 1.44 g of alumina, and 1.66 g of titanium oxide using a mixer, place the mixture in a box furnace, maintain an oxygen concentration >90%, and sinter at 400°C for 4 hours to obtain a fast-charging single crystal material Li with high roundness and high ion diffusion. 1.03 Ni 0.5929 Co 0.1976 Mn 0.1976 Zr 0.0016 Al 0.0046 Ti 0.0057 O2.

[0067] The molar ratio of the total amount of metal elements in the M source used in step (1) and the M source used in step (4) of this embodiment is 1:0.67.

[0068] Example 3 This embodiment provides a ternary cathode material and its preparation method, including the following steps: Step (1): 1 kg of nickel-cobalt-manganese precursor, 2 g of alumina, 2.4 g of cerium oxide (CeO2), and 1.18 g of strontium carbonate (SrCO3) were mixed using a mixer and then sintered in a box furnace at 550°C for 4 h in air atmosphere to obtain pre-calcined product A. The chemical formula of the nickel-cobalt-manganese precursor is Ni. 0.6 Co 0.2 Mn 0.2 (OH)2, particle size D50 is 3.8 μm, BET is 8 μm 2 / g, whisker thickness is 0.5μm.

[0069] Step (2): Mix the obtained pre-calcined material and lithium source evenly, wherein the lithium source is lithium oxide, and the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is 1.03:1. Place the obtained mixture in a box furnace and sinter at 900℃ for 12h, keeping the oxygen concentration >90%, to obtain single crystal material B.

[0070] Step (3): The single crystal material obtained above is subjected to air jet milling, and the D50 is controlled at 2.6-2.7μm to obtain single crystal material C.

[0071] Step (4): Mix 1 kg of single crystal material C, 1.44 g of alumina, and 1.66 g of titanium oxide using a mixer, place the mixture in a box furnace, maintain an oxygen concentration >90%, and sinter at 400°C for 4 hours to obtain a fast-charging single crystal material Li with high roundness and high ion diffusion. 1.03 Ni 0.5936 Co 0.1979 Mn 0.1979 Al 0.0065 Ce 0.0013 Sr 0.0008 Ti 0.0020 O2.

[0072] The molar ratio of the total amount of metal elements in the M source used in step (1) and the M source used in step (4) of this embodiment is 1:0.8.

[0073] Example 4 This embodiment provides a ternary cathode material and its preparation method, including the following steps: Step (1): Mix 1 kg of nickel-cobalt-manganese precursor, 3 g of zirconium oxide, 2.6 g of aluminum oxide, and 1 g of magnesium oxide (MgO) using a mixer, and then sinter the mixture in a box furnace at 550°C for 4 h under air atmosphere to obtain pre-sintered product A. The chemical formula of the nickel-cobalt-manganese precursor is Ni. 0.6 Co 0.2 Mn 0.2 (OH)2, particle size D50 is 3.8 μm, BET is 8 μm 2 / g, whisker thickness is 0.5μm.

[0074] Step (2): Mix the obtained pre-calcined material and lithium source evenly, wherein the lithium source is lithium hydroxide monohydrate, and the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is 1.03:1. Place the obtained mixture in a box furnace and sinter at 900℃ for 12h, keeping the oxygen concentration >90%, to obtain single crystal material B.

[0075] Step (3): The single crystal material obtained above is subjected to air jet milling, and the D50 is controlled at 2.6-2.7μm to obtain single crystal material C.

[0076] Step (4): Mix 1 kg of single crystal material C, 1.44 g of alumina, and 1.66 g of titanium oxide using a mixer, place the mixture in a box furnace, maintain an oxygen concentration >90%, and sinter at 400°C for 4 hours to obtain a fast-charging single crystal material Li with high roundness and high ion diffusion. 1.03 Ni 0.5915 Co 0.1971 Mn 0.1971 Zr 0.0023 Al 0.0076 Mg 0.0024 Ti 0.0020 O2.

[0077] The molar ratio of the total amount of metal elements in the M source used in step (1) and the M source used in step (4) of this embodiment is 1:0.49.

[0078] Example 5 This embodiment provides a ternary cathode material and its preparation method, including the following steps: Step (1): 1 kg of nickel-cobalt-manganese precursor, 3 g of zirconium oxide, 1.6 g of alumina, and 2 g of molybdenum oxide (MoO3) were mixed using a mixer and then sintered in a box furnace at 550°C for 4 h in air atmosphere to obtain pre-sintered product A. The chemical formula of the nickel-cobalt-manganese precursor is Ni 0.6 Co 0.2 Mn 0.2 (OH)2, particle size D50 is 3.8 μm, BET is 8 μm 2 / g, whisker thickness is 0.5μm.

[0079] Step (2): Mix the obtained pre-calcined material and lithium source evenly, wherein the lithium source is lithium hydroxide monohydrate, and the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is 1.03:1. Place the obtained mixture in a box furnace and sinter at 900℃ for 12h, keeping the oxygen concentration >90%, to obtain single crystal material B.

[0080] Step (3): The single crystal material obtained above is subjected to air jet milling, and the D50 is controlled at 2.6-2.7μm to obtain single crystal material C.

[0081] Step (4): Mix 1 kg of single crystal material C, 1.44 g of alumina, and 1.66 g of titanium oxide using a mixer, place the mixture in a box furnace, maintain an oxygen concentration >90%, and sinter at 400°C for 6 hours to obtain a fast-charging single crystal material Li with high roundness and high ion diffusion. 1.03 Ni 0.5931 Co 0.1977 Mn 0.1977 Zr 0.0023 Al 0.0057 Mo 0.0014 Ti 0.0021 O2.

[0082] The molar ratio of the total amount of metal elements in the M source used in step (1) and the M source used in step (4) of this embodiment is 1:0.7.

[0083] Example 6 The difference between this comparative example and Example 1 is that the oxygen concentration in step (2) is 70%.

[0084] Example 7 The only difference between this comparative example and Example 1 is that the low-temperature pre-firing in step (1) is omitted, and high-temperature sintering is carried out directly.

[0085] Comparative Example 1 The difference between this comparative example and Example 1 is that no structure inducer was used, and calcination was performed directly. The steps are as follows: the precursor was sintered at 550°C for 4 hours in air atmosphere, and then mixed with the lithium source and sintered at 900°C for 12 hours.

[0086] Comparative Example 2 The only difference between this comparative example and Example 1 is that the amounts of zirconium oxide, titanium oxide, and yttrium oxide were adjusted so that the sum of the product of the metal valence state of element M and the molar percentage of the metal in the ternary cathode material was 0.302.

[0087] Comparative Example 3 The only difference between this comparative example and Example 1 is that the amounts of zirconium oxide, titanium oxide, and yttrium oxide are adjusted so that the sum of the product of the metal valence state of element M and the molar percentage of the metal in the ternary cathode material is 0.008.

[0088] The SEM images, particle size distribution map, and XRD patterns of the ternary cathode material prepared in Example 1 are shown below. Figures 1-3 As shown; the SEM images and particle size distribution diagrams of the ternary cathode material prepared in Comparative Example 1 are shown. Figures 4-5 As shown.

[0089] Depend on Figures 1-3 It can be seen that the cathode material particles have a high degree of single crystallization, are ellipsoidal in shape, and are relatively round and well dispersed.

[0090] Figure 4 The image shows a SEM image of ternary single-crystal particles without the introduction of a structure inducer. As can be seen from the image, the resulting cathode material particles are irregular in shape, have poor roundness, agglomerate, and have poor processing performance. This indicates that the growth direction of the cathode particles is irregular during the sintering process.

[0091] Figure 5 The graph shows the number and size distribution of single crystal particles without the introduction of a structure inducer. As can be seen from the graph, it exhibits a bimodal distribution and a relatively wide overall particle size distribution, indicating that the primary particle sizes are not uniform.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary cathode material, characterized in that, Its chemical formula is Li 1+x Ni a Co b Mn c M d O2; Where a+b+c+d=1, a is 0.50-0.90, b is 0.05-0.20, c is 0.05-0.35, d is 0.004-0.040, and x is 0.01-0.08; Element M is a combination of two to eight elements selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce, and Mg, where the molar percentage of each element in the total amount of nickel, cobalt, manganese, and M is M. i The stable oxidation state of each element in the compound is N. i Y=ΣM i ×N i And Y satisfies: 0.01≤Y≤0.

15.

2. The ternary cathode material according to claim 1, characterized in that, The lithium-ion diffusion coefficient of the ternary cathode material is 10. -15 -10 -11 m 2 / s, the formula for calculating the lithium-ion diffusion coefficient is as follows: ； In the formula, m B This indicates the number of moles, expressed in mol. V m The molar volume of the electrode material is expressed in m³. 3 / mol; S represents the electrode / electrolyte contact area, in m². 2 ; Δ E s This represents the total voltage change caused by the pulse, expressed in V. Δ E τ This represents the voltage change during constant current charging and discharging, with the unit being V; τ This represents the relaxation time, measured in seconds (s).

3. The ternary cathode material according to claim 1 or 2, characterized in that, The crystallinity ratio of the ternary cathode material is 0.02-0.06, and the formula for calculating the crystallinity ratio is as follows: Crystallinity ratio = D1 / D2; In the formula, D1 represents the grain size of the (003) crystal plane in XRD, in nm; D2 represents the average size of primary particles in SEM, in nm.

4. The ternary cathode material according to claim 3, characterized in that, The roundness of the ternary cathode material is 0.5-0.9, and the formula for calculating the roundness is as follows: Roundness = (4π × s) / c 2 ; In the formula, s represents the cross-sectional area of ​​the ternary cathode material, with units of μm. 2 ; c represents the cross-sectional perimeter of the ternary cathode material, in μm.

5. A method for preparing the ternary cathode material according to any one of claims 1-4, characterized in that, include: The nickel-cobalt-manganese precursor is mixed with the first M source and sintered at the first sintering temperature to obtain the pre-sintered product; The pre-burned material is mixed with a lithium source and sintered at a second sintering temperature to obtain a sintered material; After the sintered material is crushed, a single crystal material with a particle size of 2.0 μm-4.5 μm is obtained; The single crystal material is mixed with the second M source and sintered at a third sintering temperature. Wherein, the second sintering temperature is greater than the first sintering temperature, and the second sintering temperature is greater than the third sintering temperature.

6. The preparation method according to claim 5, characterized in that, The metal elements in the first M source and the second M source are each independently selected from two to eight combinations of elements selected from Zr, Sr, Ni, Co, Mn, Al, Ti, Y, Mo, Nb, W, Ca, Na, Sb, Cu, Fe, Ta, Ce and Mg; And / or, the first M source and the second M source are each independently selected from at least one of oxides, carbonates, phosphates, nitrates and lithium-containing complex oxides; And / or, the molar ratio of the total amount of metal elements in the first M source and the second M source is 1:(0.4-3). And / or, during the preparation of the pre-sintered material, the sintering atmosphere is air or oxygen, the sintering temperature is controlled at 350℃-750℃, and the sintering time is 4h-20h; preferably, the sintering temperature is controlled at 500℃-700℃, and the sintering time is 4h-10h. And / or, the particle size D50 of the nickel-cobalt-manganese precursor is 2.0 μm-4.5 μm; And / or, the BET of the nickel-cobalt-manganese precursor is 5m. 2 / g-20m 2 / g; And / or, the whisker thickness of the nickel-cobalt-manganese precursor is 0.1 μm-1.5 μm.

7. The preparation method according to claim 5, characterized in that, In the process of preparing the sintered material from the pre-sintered material, the sintering temperature is controlled at 750℃-1050℃ and the sintering time is controlled at 6h-16h; preferably, the sintering temperature is controlled at 850℃-1000℃ and the sintering time is controlled at 10h-15h. And / or, during the preparation of the sintered product from the pre-sintered product, the sintering atmosphere requires an oxygen volume fraction greater than 90%; And / or, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the pre-calcined material is controlled to be (1.00-1.08):1, preferably (1.02-1.08):1; And / or, the lithium source is selected from at least one of lithium hydroxide monohydrate, lithium carbonate, lithium oxide, and lithium hydroxide.

8. The preparation method according to claim 5, characterized in that, The single crystal material is mixed with the second M source and sintered in an oxygen-containing atmosphere at a sintering temperature of 300℃-750℃ for 3h-15h; preferably, the sintering temperature is 400℃-750℃ and the sintering time is 5h-12h. Preferably, the oxygen volume fraction in the oxygen-containing atmosphere is greater than 90%.

9. A positive electrode sheet, characterized in that, This includes the ternary cathode material according to any one of claims 1-4 or the ternary cathode material prepared by the preparation method according to any one of claims 5-8.

10. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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