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

Abstract

The invention provides a ternary positive electrode material, a preparation method thereof and a lithium ion battery. The ternary positive electrode material at least meets the following conditions: S > = 4, S = 0.5 * (S1 + S2) / (S1-S2), s is an influence factor for reflecting the influence of the gradient difference of the pore specific surface area and the dynamic structure-activity on the stacking effect of the material; s1 and S2 are pore specific surface areas of the ternary positive electrode material after densification treatment, and S1 is greater than S2. The ternary positive electrode material is controlled to meet the condition that S is larger than or equal to 4, by means of regulation and control over the pore structure and the dynamic structure-activity gradient difference of the material, the non-uniformity of the macroscopic morphology and the microstructure of the ternary positive electrode material under the dynamic working condition is reduced, and more consistent stacking behavior and more uniform stress distribution are achieved; the synchronism of active substance capacity exertion and the continuity of an ion / electron transport network are improved, and the occurrence of interface side reaction is inhibited. The capacity and the cycle life of the battery prepared based on the ternary positive electrode material are improved.

Description

Technical Field

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

[0002] As a core component in current energy storage and power applications, the energy density, cycle life, and safety of lithium-ion batteries largely depend on the performance of the cathode material. Ternary cathode materials (such as nickel-cobalt-manganese ternary cathode materials) have become a key solution to meet the demand for high energy density due to their high specific capacity and voltage platform. They are widely used in high-end electric vehicles, high-end consumer electronics, and specific energy storage scenarios, and are an important material foundation supporting the electrification of transportation, energy structure transformation, and the upgrading of the high-end manufacturing industry chain.

[0003] However, under actual dynamic operating conditions, ternary cathode materials often exhibit inhomogeneities in their macroscopic morphology (such as particle size, morphological uniformity, and pore distribution) and microscopic crystal structure (such as lattice parameters, crystal orientation, and cation mixing degree). These inhomogeneities can lead to differences in mechanical properties within and between particles, asynchronous phase transitions, and mismatches in local volume changes during battery operation. This, in turn, results in asynchronous capacity development of the active material, discontinuities in the ion / electron transport network, and stress concentration. These factors further affect the interfacial conditions and interfacial side reactions, ultimately limiting the capacity and cycle stability of ternary cathode materials.

[0004] Therefore, there is an urgent need to provide a ternary cathode material with small dynamic structure-property gradient differences and stable cycle performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a ternary cathode material, its preparation method, and a lithium-ion battery. By controlling the ternary cathode material to satisfy the condition ∆S≥4, and through effective regulation of the internal pore structure and dynamic structure-property gradient differences, the present invention reduces the inhomogeneity of the macroscopic morphology and microscopic crystal structure of the ternary cathode material under dynamic operating conditions. This achieves more consistent stacking behavior and a more uniform stress distribution, thereby improving the synchronicity of the active material's capacity utilization and the continuity of the ion / electron transport network, and suppressing the occurrence of interfacial side reactions. Therefore, the ternary cathode material satisfying this condition exhibits higher structural stability and interfacial integrity, laying the foundation for the preparation of high-energy-density, long-life lithium-ion batteries.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a ternary cathode material, wherein the ternary cathode material at least meets the following requirements:

[0008] ΔS≥4, ΔS=0.5×(S1+S2) / (S1-S2).

[0009] Wherein, ∆S is the influence factor reflecting the gradient difference between pore specific surface area and dynamic structure-property ratio on the stacking effect of the material; S1 and S2 are both the pore specific surface areas of the ternary cathode material after densification treatment, and S1 > S2.

[0010] During the pressing process of ternary cathode materials into sheets, capillary action occurs between the particles. During drying, after the solvent evaporates from the electrode surface, the internal liquid phase is drawn to the surface by capillary forces, creating a "pump" effect. This causes the binder to float, and the active material gradually detaches due to insufficient adhesion. The structure-property gradient differences formed during dynamic operation of the ternary cathode material affect the uniformity of the internal void distribution. If the dynamic structure-property gradient differences are too large, resulting in void distribution variations, the bonding stability of the ternary cathode material within the electrode will be uneven, thus affecting the structural stress distribution and the integrity of the conductive network, ultimately impacting the battery's cycle stability.

[0011] To address this, this invention controls the ternary cathode material to satisfy the condition ∆S≥4. By effectively regulating the internal pore structure and dynamic structure-property gradient differences of the material, more consistent stacking behavior and more uniform stress distribution are achieved. This improves the synchronicity of the active material's capacity utilization and the continuity of the ion / electron transport network, while suppressing interfacial side reactions. Therefore, the ternary cathode material satisfying this condition exhibits higher structural stability and interfacial integrity, laying the foundation for the fabrication of high-energy-density, long-life lithium-ion batteries.

[0012] In this invention, "S1-S2" reflects the influence of the gradient difference in dynamic structure-property ratio on the material's packing effect. A larger S1-S2 indicates greater packing variation, while a smaller S1-S2 indicates less packing variation. Simultaneously, the pore specific surface area also affects the electrolyte's wetting area. "0.5 × (S1 + S2)" represents the average pore specific surface area; a larger value indicates a larger electrolyte wetting area, and a smaller value indicates a smaller wetting area. ∆S reflects the influence of the gradient difference in pore specific surface area and dynamic structure-property ratio on the material's packing effect. A larger ∆S indicates a smaller influence of these gradient differences on the packing effect and better cycle stability; a smaller ∆S indicates a larger influence of these gradient differences and worse cycle stability.

[0013] Preferably, the ternary cathode material is a lithium nickel cobalt manganese oxide ternary cathode material.

[0014] In this invention, ∆S≥4, for example, it can be 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 or 30, etc.

[0015] Preferably, the ∆S satisfies: 4≤∆S≤30.

[0016] Preferably, the apertures corresponding to S1 and S2 are 2-200nm, for example, they can be 2nm, 5nm, 10nm, 50nm, 100nm, 150nm or 200nm, etc.

[0017] It should be noted that the pore specific surface area can be measured using a BSD-660S A6B6.

[0018] Preferably, the densification process includes sequential vibration separation and pressing processes, wherein the pressure applied during the pressing process is 4-6T, for example, 4T, 5T or 6T.

[0019] It should be noted that "vibration separation" refers to the process of separating upper and lower particles by vibrating and moving them up and down in a test tube.

[0020] Preferably, the ternary cathode material also meets the following requirements:

[0021] ∆A≤20, ∆A=(|A 上前 -A 上压 | / A 上前 +|A 下前 -A 下压 | / A 下前 ) / 2×100.

[0022] Wherein, ∆A is the influence factor reflecting the effect of the gradient difference in dynamic structure-property ratio on the crystal orientation and microstructure of the material; A 上前 and A 下前 A represents the peak areas of the upper and lower particles of the ternary cathode material after vibration, respectively, at the characteristic peaks of the X-ray diffraction peaks on the (003) crystal plane. 上压 and A 下压 These are the peak areas of the X-ray diffraction characteristic peaks of the (003) crystal plane corresponding to the upper and lower particles after pressing.

[0023] In this invention, the gradient difference in dynamic structure-property ratio directly affects the crystal structure and pore size distribution of the material in subsequent fabrication processes such as rolling, manifested as changes in the diffraction peak area of ​​the (003) crystal plane of particles with different sizes. ∆A is the key parameter for quantifying this influence: the smaller ∆A is, the smaller the impact of dynamic structure-property ratio difference on the crystal structure and microstructure of the material, and the higher the structural consistency of the material; the larger ∆A is, the greater the impact of dynamic structure-property ratio difference on the crystal structure and microstructure of the material, and the more significant the structural difference. By controlling ∆A within the range of ≤20, this invention can effectively regulate the crystal orientation and microstructure consistency of the material, thereby suppressing interfacial side reactions and ultimately improving the cycle stability of the ternary cathode material.

[0024] In this invention, ∆A≤20, and can be, for example, 1, 3, 5, 7, 9, 10, 13, 15, 16, 17, 18, 19 or 20, etc.

[0025] It should be noted that the peak area of ​​the characteristic peak of X-ray diffraction of the (003) crystal plane is obtained by X-ray diffraction test.

[0026] Preferably, ∆A satisfies: 1≤∆A≤20.

[0027] Preferably, the pressure applied during the pressing process is 4-6T, for example, it can be 4T, 5T or 6T.

[0028] Preferably, the ternary cathode material satisfies: 0.7≤∆S / ∆A≤15, and the value of ∆S / ∆A can be, for example, 0.7, 1, 3, 5, 7, 9, 12, 13 or 15, etc.

[0029] In this invention, 0.7≤∆S / ∆A≤15. This inequality combines the effects of ∆S and ∆A, including the combined effect of microstructure, crystal morphology, structural stress, and conductive network on the electrical performance of ternary cathode materials.

[0030] In a second aspect, the present invention provides a method for preparing a ternary cathode material as described in the first aspect, the method comprising the following steps:

[0031] The first nickel-cobalt-manganese mixed salt solution, precipitant, and complexing agent are added in parallel to the first reaction vessel containing the bottom liquid to carry out the first co-precipitation reaction, thereby obtaining the ternary precursor seed slurry.

[0032] A portion of the ternary precursor seed slurry is placed in the second reactor, and then a second nickel-cobalt-manganese mixed salt solution, a precipitant, a complexing agent, a persulfate solution, and a coordinating agent are added in parallel to carry out the second coprecipitation reaction to obtain the ternary precursor intermediate slurry.

[0033] The remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed into the third reactor. Then, a third nickel-cobalt-manganese mixed salt solution, a precipitant, and a complexing agent are added in parallel to carry out the third co-precipitation reaction. After the reaction, post-processing is performed to obtain the ternary precursor.

[0034] The ternary precursor and lithium source are mixed and calcined to obtain the ternary cathode material.

[0035] In this invention, a portion of the ternary precursor seed slurry is transferred into the second reactor as a base liquid. During the introduction of the second nickel-cobalt-manganese mixed salt solution, precipitant, and complexing agent, a persulfate solution is also added to initiate a second co-precipitation reaction. Under a specific pH environment, the persulfate solution utilizes the characteristic that its O2O bonds are more easily hydrolyzed by alkaline substances, thereby generating hydroxyl radicals. ; ; Among them, the OO bonds of persulfate are more easily activated by direct electron transfer from metal active sites, resulting in significant and locally specific ·OH. Due to the high reactivity, high local electron density, and very high coordination unsaturation of the edge active sites of the ternary precursor grains, they can preferentially adsorb and activate persulfate, leading to the specific generation of ·OH at these sites. The intact crystal faces with low surface energy hardly participate in this process, and then the corresponding precipitates can be rapidly formed at the tips, achieving selective growth at the crystal boundaries and obtaining a partial whisker growth layer. Subsequently, the remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed into the third reactor for mixing to continue the third coprecipitation reaction, finally obtaining a ternary cathode material with small gradient differences in dynamic structure and property.

[0036] In this invention, the purpose of introducing persulfate is to adjust the density and volume of small particles in the ternary cathode material, thereby reducing the difference in the dynamic structure-property gradient. During the third coprecipitation reaction, it helps to increase the surface roughness of the particles and simultaneously increase the dissipation of stress on the particle surface, reducing the changes in particle structure caused by stress concentration. In addition, the adjustment of the ligand, pH, and calcination temperature can prevent the persulfate from affecting the oxidation of cobalt.

[0037] Preferably, in the first nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5). The range of nickel ions ("5-95") can be, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95; the range of cobalt ions ("1-9") can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, or 9; and the range of manganese ions ("1-5") can be, for example, 1, 2, 3, 4, or 5. It should be noted that the molar ratio of nickel ions, cobalt ions, and manganese ions is selected according to the atomic ratio of nickel, cobalt, and manganese elements in the chemical formula of the ternary precursor and the final ternary cathode material, and the same applies below.

[0038] Preferably, the concentration of the first nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, for example, it can be 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L, or 2.2 mol / L, etc. It should be noted that this concentration refers to the total concentration of nickel, cobalt, and manganese in the solution, and the same applies below.

[0039] Preferably, the anions in the first nickel-cobalt-manganese mixed salt solution include sulfate ions.

[0040] Preferably, the feed rate of the first nickel-cobalt-manganese mixed salt solution is 20-35 mL / min, for example, it can be 20 mL / min, 25 mL / min, 30 mL / min or 35 mL / min.

[0041] Preferably, during the first coprecipitation reaction, the pH of the solution system is 11-12, for example, it can be 11, 11.2, 11.4, 11.6, 11.8 or 12.

[0042] Preferably, during the first coprecipitation reaction, the reaction temperature is 45-60℃, for example, it can be 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃, etc.

[0043] Preferably, in the ternary precursor seed slurry, the particle size Dv50 of the seed particles is 2-5 μm, for example, it can be 2 μm, 3 μm, 4 μm or 5 μm, etc.

[0044] Preferably, in the second nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5), wherein the range of nickel ions "5-95" can be, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95, the range of cobalt ions "1-9" can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, or 9, and the range of manganese ions "1-5" can be, for example, 1, 2, 3, 4, or 5.

[0045] Preferably, the concentration of the second nickel-cobalt-manganese mixed salt solution is 0.8-1.2 mol / L, for example, it can be 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L or 1.2 mol / L, etc.

[0046] Preferably, the anions in the second nickel-cobalt-manganese mixed salt solution include sulfate ions.

[0047] Preferably, the feed rate of the second nickel-cobalt-manganese mixed salt solution is 10-20 mL / min, for example, it can be 10 mL / min, 15 mL / min or 20 mL / min.

[0048] Preferably, the feed rate of the first nickel-cobalt-manganese mixed salt solution is greater than the feed rate of the second nickel-cobalt-manganese mixed salt solution.

[0049] Preferably, the persulfate solution comprises a KHSO5 solution.

[0050] Preferably, the concentration of the persulfate solution is 0.6-1.5 mol / L, for example, it can be 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L or 1.5 mol / L, etc.

[0051] Preferably, the feed rate of the persulfate solution is 5-10 mL / min, for example, it can be 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min or 10 mL / min, etc.

[0052] Preferably, the feeding time of the persulfate solution is 0.5-2.5h, for example, it can be 0.5h, 1h, 1.5h, 2h or 2.5h.

[0053] Preferably, the ligand comprises ethylenediaminetetraacetic acid and / or citric acid.

[0054] Preferably, the concentration of the ligand is 0.08-0.12 mol / L, for example, it can be 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L or 0.12 mol / L, etc.

[0055] Preferably, the feed rate of the ligand is 10-20 mL / min, for example, it can be 10 mL / min, 12 mL / min, 14 mL / min, 16 mL / min, 18 mL / min or 20 mL / min, etc.

[0056] Preferably, the addition time of the ligand is the same as the addition time of the persulfate solution.

[0057] Preferably, the feed rate ratio of the persulfate solution and the complexing agent is (5-10):(10-20), wherein the persulfate solution is selected in the range of "5-10", for example, 5, 6, 7, 8, 9 or 10, and the complexing agent is selected in the range of "10-20", for example, 10, 12, 14, 16, 18 or 20.

[0058] Preferably, during the second coprecipitation reaction, the pH of the solution system is 10-10.5, for example, it can be 10, 10.1, 10.2, 10.3, 10.4 or 10.5.

[0059] Preferably, during the second coprecipitation reaction, the reaction temperature is 45-60℃, for example, it can be 45℃, 50℃, 55℃ or 60℃.

[0060] Preferably, the reaction time during the second coprecipitation reaction is 1-3 hours, for example, 1 hour, 2 hours or 3 hours.

[0061] Preferably, in the third nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5), wherein the range of nickel ions "5-95" can be, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95, the range of cobalt ions "1-9" can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, or 9, and the range of manganese ions "1-5" can be, for example, 1, 2, 3, 4, or 5.

[0062] Preferably, the concentration of the third nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, for example, it can be 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L or 2.2 mol / L, etc.

[0063] Preferably, the anions in the third nickel-cobalt-manganese mixed salt solution include sulfate ions.

[0064] Preferably, the feed rate of the third nickel-cobalt-manganese mixed salt solution is 30-40 mL / min, for example, it can be 30 mL / min, 32 mL / min, 34 mL / min, 36 mL / min, 38 mL / min or 40 mL / min, etc.

[0065] In this invention, a feeding rate of up to 30-40 mL / min for the third nickel-cobalt-manganese mixed salt solution is used to increase the dissipation capacity of the ternary cathode material surface against stress.

[0066] Preferably, during the third coprecipitation reaction, the pH of the solution system is 11.5-12, for example, it can be 11.5, 11.6, 11.7, 11.8, 11.9 or 12.

[0067] In the third coprecipitation reaction, the pH of the solution system is controlled to be 11.5-12 in order to increase the dissipation capacity of the ternary cathode material particles on the surface of the particles.

[0068] Preferably, during the third coprecipitation reaction, the reaction temperature is 45-60℃, for example, it can be 45℃, 50℃, 55℃ or 60℃.

[0069] Preferably, the calcination process includes a first calcination step and a second calcination step performed by sequentially increasing the temperature.

[0070] Preferably, the temperature of the first calcination step is 300-350℃, for example, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, and the holding time is 5-7h, for example, 5h, 6h or 7h.

[0071] Preferably, the calcination temperature in the second step is 750-800℃, for example, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, and the holding time is 12-15h, for example, 12h, 13h, 14h or 15h.

[0072] Preferably, the preparation method includes the following steps:

[0073] (1) The first nickel-cobalt-manganese mixed salt solution, the alkaline solution (e.g., sodium hydroxide solution) and ammonia water are added in parallel to the first reaction vessel containing the bottom liquid. The first coprecipitation reaction is carried out at 400-700 rpm (e.g., 400 rpm, 500 rpm, 600 rpm or 700 rpm) and 45-60℃ to obtain the ternary precursor seed slurry.

[0074] In the first nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5); the concentration of the first nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, and the feed rate is 20-35 mL / min; during the first coprecipitation reaction, the pH of the solution system is 11-12, and the ammonia concentration of the solution system is 0.65-0.9 mol / L (e.g., 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, or 0.9 mol / L, etc.); the concentration of the alkaline solution is 4-6 mol / L (e.g., 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L, etc.); in the ternary precursor seed slurry, the particle size Dv50 of the seed particles is 2-5 μm.

[0075] (2) The upper layer of the ternary precursor seed slurry is placed in the second reactor, and then a second nickel-cobalt-manganese mixed salt solution, an alkaline solution, ammonia, a persulfate solution and a complexing agent are added in parallel. The second coprecipitation reaction is carried out at 400-700 rpm (e.g., 400 rpm, 500 rpm, 600 rpm or 700 rpm, etc.) and 45-60°C for 1-3 hours to obtain the ternary precursor intermediate slurry.

[0076] The upper slurry comprises 30-50 vol% (e.g., 30 vol%, 40 vol%, or 50 vol%) of the ternary precursor seed slurry; the molar ratio of nickel ions, cobalt ions, and manganese ions in the second nickel-cobalt-manganese mixed salt solution is (5-95):(1-9):(1-5); the concentration of the second nickel-cobalt-manganese mixed salt solution is 0.8-1.2 mol / L, and the feed rate is 10-20 mL / min; the persulfate solution includes KHSO5 solution; the concentration of the persulfate solution is 0.6-1.5 mol / L, and the feed rate is 5-10 mL / min; the coordinating agent includes ethylenediaminetetraacetic acid. The mixture contains citric acid and / or ligand; the concentration of the ligand is 0.08-0.12 mol / L, and the feed rate is 10-20 mL / min; during the second coprecipitation reaction, the pH of the solution system is 10-10.5, and the ammonia concentration of the solution system is 0.65-0.9 mol / L (e.g., 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, or 0.9 mol / L, etc.); the concentration of the alkaline solution is 4-6 mol / L (e.g., 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L, etc.).

[0077] (3) The remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed in the third reactor. Then, a third nickel-cobalt-manganese mixed salt solution, an alkaline solution and ammonia are added in parallel. The third coprecipitation reaction is carried out at 400-700 rpm (e.g., 400 rpm, 500 rpm, 600 rpm or 700 rpm, etc.) and 45-60℃ for 1-3 hours (e.g., 1 hour, 2 hours or 3 hours, etc.). Then, post-processing is performed to obtain the ternary precursor.

[0078] In the third nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5); the concentration of the third nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, and the feed rate is 30-40 mL / min; during the third coprecipitation reaction, the pH of the solution system is 11.5-12, and the ammonia concentration of the solution system is 0.65-0.9 mol / L (e.g., 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, or 0.9 mol / L, etc.); the concentration of the alkaline solution is 4-6 mol / L (e.g., 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L, etc.).

[0079] (4) The ternary precursor and the lithium source are mixed and calcined to obtain the ternary cathode material.

[0080] The molar ratio of the transition metal element in the ternary precursor to the lithium metal element in the lithium source is 1:(1.02-1.05) (e.g., 1:1.02, 1:1.03, 1:1.04, or 1:1.05, etc.); the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium oxalate; the calcination atmosphere is an oxygen-containing atmosphere (exemplarily, such as air or an oxygen atmosphere, etc.); the calcination process includes a first calcination and a second calcination performed by sequentially increasing the temperature; the temperature of the first calcination is 300-350℃, and the holding time is 5-7h; the temperature of the second calcination is 750-800℃, and the holding time is 12-15h.

[0081] Thirdly, the present invention provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery comprises a ternary positive electrode material as described in the first aspect.

[0082] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0083] Compared with the prior art, the present invention has the following beneficial effects:

[0084] This invention achieves more consistent stacking behavior and a more uniform stress distribution in ternary cathode materials by controlling the condition ∆S≥4. This improves the synchronicity of active material capacity utilization and the continuity of the ion / electron transport network, while suppressing interfacial side reactions. Therefore, ternary cathode materials meeting this condition exhibit higher structural stability and interfacial integrity, laying the foundation for the fabrication of high-energy-density, long-life lithium-ion batteries. Detailed Implementation

[0085] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0086] Example 1

[0087] This embodiment provides a method for preparing a ternary cathode material, the method comprising the following steps:

[0088] (1) Nickel sulfate, cobalt sulfate and manganese sulfate were prepared in a ratio of Ni:Co:Mn of 8:1:1 to obtain a first nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 1.5 mol / L.

[0089] The first nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, and ammonia water were added concurrently to the first reaction vessel containing deionized water. The first coprecipitation reaction was carried out at 550 rpm and 60°C until the particle size Dv50 of the seed crystals was 3 μm. Then the feeding was stopped to obtain the ternary precursor seed crystal slurry.

[0090] The feed rate of the first nickel-cobalt-manganese mixed salt solution is 30 mL / min; during the first coprecipitation reaction, the pH of the solution system is 11.5 and the ammonia concentration of the solution system is 0.75 mol / L.

[0091] (2) Nickel sulfate, cobalt sulfate and manganese sulfate were prepared in a ratio of Ni:Co:Mn of 8:1:1 to obtain a second nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 0.9 mol / L.

[0092] The upper layer of the ternary precursor seed slurry was placed in the second reactor, and then the second nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, ammonia, 1 mol / L KHSO5 solution and 0.09 mol / L ethylenediaminetetraacetic acid solution were added in parallel. The second coprecipitation reaction was carried out at 550 rpm and 60°C for 2 h. After the reaction was completed, the ternary precursor intermediate slurry was obtained.

[0093] The upper slurry comprises 40 vol% of the ternary precursor seed slurry; the feed rate of the second nickel-cobalt-manganese mixed salt solution is 15 mL / min; the feed rate of the KHSO5 solution is 8 mL / min, and the feed is stopped after 1 hour; the feed rate of the ethylenediaminetetraacetic acid solution is 15 mL / min, and the feed time is the same as that of the KHSO5 solution; during the second coprecipitation reaction, the pH of the solution system is 10, and the ammonia concentration of the solution system is 0.7 mol / L.

[0094] (3) The remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed in the third reactor. Then, the third nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution and ammonia water are introduced in parallel. The third coprecipitation reaction is carried out at 550 rpm and 60°C for 1 h. Then, the mixture is filtered, washed and dried to obtain the ternary precursor.

[0095] The third nickel-cobalt-manganese mixed salt solution has the same composition and concentration as the first nickel-cobalt-manganese mixed salt solution; the feed rate of the third nickel-cobalt-manganese mixed salt solution is 35 mL / min; during the third coprecipitation reaction, the pH of the solution system is 11.5 and the ammonia concentration of the solution system is 0.75 mol / L.

[0096] (4) The ternary precursor and lithium carbonate are mixed in a molar ratio of Li:(Ni+Co+Mn) of 1.05:1 and then calcined in an oxygen atmosphere at a heating rate of 3℃ / min in two steps to obtain the ternary cathode material.

[0097] In the two-step calcination process, the first calcination temperature is 330℃ and the holding time is 6h; the second calcination temperature is 780℃ and the holding time is 13h.

[0098] Example 2

[0099] The difference between this embodiment and embodiment 1 is that step (2) is replaced by:

[0100] A second nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 0.9 mol / L was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a Ni:Co:Mn molar ratio of 8:1:1.

[0101] The upper layer of the ternary precursor seed slurry was placed in the second reactor, and then the second nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, ammonia, 0.7 mol / L KHSO5 solution and 0.08 mol / L ethylenediaminetetraacetic acid solution were added in parallel. The second coprecipitation reaction was carried out at 550 rpm and 60°C for 2 h. After the reaction was completed, the ternary precursor intermediate slurry was obtained.

[0102] The upper slurry comprises 30 vol% of the ternary precursor seed slurry; the feed rate of the second nickel-cobalt-manganese mixed salt solution is 15 mL / min; the feed rate of the KHSO5 solution is 6 mL / min, and the feed is stopped after 1 hour; the feed rate of the ethylenediaminetetraacetic acid solution is 12 mL / min, and the feed time is the same as that of the KHSO5 solution; during the second coprecipitation reaction, the pH of the solution system is 10, and the ammonia concentration of the solution system is 0.7 mol / L.

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Example 3

[0105] The difference between this embodiment and embodiment 1 is that step (2) is replaced by:

[0106] A second nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 0.9 mol / L was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a Ni:Co:Mn molar ratio of 8:1:1.

[0107] The upper layer of the ternary precursor seed slurry was placed in the second reactor, and then the second nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, ammonia, 0.8 mol / L KHSO5 solution and 0.1 mol / L ethylenediaminetetraacetic acid solution were added in parallel. The second coprecipitation reaction was carried out at 550 rpm and 60°C for 2.5 h. After the reaction was completed, the ternary precursor intermediate slurry was obtained.

[0108] The upper slurry comprises 45 vol% of the ternary precursor seed slurry; the feed rate of the second nickel-cobalt-manganese mixed salt solution is 12 mL / min; the feed rate of the KHSO5 solution is 10 mL / min, and the feed is stopped after 1.5 h; the feed rate of the ethylenediaminetetraacetic acid solution is 14 mL / min, and the feed time is the same as that of the KHSO5 solution; during the second coprecipitation reaction, the pH of the solution system is 10, and the ammonia concentration of the solution system is 0.7 mol / L.

[0109] The remaining preparation methods and parameters are consistent with those in Example 1.

[0110] Example 4

[0111] The difference between this embodiment and embodiment 1 is that, in step (1), the particle size Dv50 of the seed particles in the ternary precursor seed slurry is 3.5 μm; in step (2), the time of the second coprecipitation reaction is 2.5 h; in step (3), the time of the third coprecipitation reaction is 1.5 h, the pH of the solution system is 11.8, and the feed rate of the third nickel-cobalt-manganese mixed salt solution is 40 mL / min.

[0112] The remaining preparation methods and parameters are consistent with those in Example 1.

[0113] Example 5

[0114] The difference between this embodiment and embodiment 1 is that, in step (1), the particle size Dv50 of the seed particles in the ternary precursor seed slurry is 2 μm; in step (2), the feed rate of the ethylenediaminetetraacetic acid solution is 10 mL / min, and the time of the second coprecipitation reaction is 3 h; in step (3), the feed rate of the third nickel-cobalt-manganese mixed salt solution is 30 mL / min.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Example 6

[0117] The difference between this embodiment and embodiment 1 is that, in step (1), the particle size Dv50 of the seed particles in the ternary precursor seed slurry is 1.5 μm; in step (2), the total concentration of transition metal ions in the second nickel-cobalt-manganese mixed salt solution is 1.5 mol / L, the feed rate of the second nickel-cobalt-manganese mixed salt solution is 25 mL / min, the time of the second coprecipitation reaction is 3 h, and the feed of the KHSO5 solution is stopped after 2 h; in step (3), the feed rate of the third nickel-cobalt-manganese mixed salt solution is 50 mL / min, the time of the third coprecipitation reaction is 2 h, and the pH of the solution system is 12.

[0118] The remaining preparation methods and parameters are consistent with those in Example 1.

[0119] Example 7

[0120] The difference between this embodiment and Embodiment 1 is that, in step (1), the particle size Dv50 of the seed crystals in the ternary precursor seed slurry is 3.2 μm. In step (2), 30 vol% of the ternary precursor seed slurry is placed in the second reaction vessel; the concentration of the KHSO5 solution is 0.5 mol / L, the feed rate of the KHSO5 solution is 4 mL / min, and the feed is stopped after 0.5 h; the time for the second coprecipitation reaction is 1 h; during the second coprecipitation reaction, the pH of the solution system is 10.5. In step (3), the time for the third coprecipitation reaction is 1.5 h, the pH of the solution system is 11.8, and the feed rate of the third nickel-cobalt-manganese mixed salt solution is 40 mL / min. In step (4), the temperature of the first calcination step is 350 °C.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Example 8

[0123] The difference between this embodiment and embodiment 1 is that in step (2), the ethylenediaminetetraacetic acid solution is replaced with a citric acid solution of equal concentration; the concentration of the KHSO5 solution is 0.8 mol / L, and the feed rate is 5 mL / min.

[0124] The remaining preparation methods and parameters are consistent with those in Example 1.

[0125] Example 9

[0126] The difference between this embodiment and embodiment 1 is that in step (2), the concentration of KHSO5 solution is 1.3 mol / L and the feed rate is 9 mL / min.

[0127] The remaining preparation methods and parameters are consistent with those in Example 1.

[0128] Example 10

[0129] The difference between this embodiment and embodiment 1 is that, in step (3), during the third coprecipitation reaction, the pH of the solution system is 11, and the feed rate of the third nickel-cobalt-manganese mixed salt solution is 30 mL / min.

[0130] The remaining preparation methods and parameters are consistent with those in Example 1.

[0131] Example 11

[0132] This embodiment provides a method for preparing a ternary cathode material, the method comprising the following steps:

[0133] (1) Nickel sulfate, cobalt sulfate and manganese sulfate were prepared in a ratio of Ni:Co:Mn of 8:1:1 to obtain a nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 1.5 mol / L.

[0134] The nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, and ammonia water were added concurrently to the first reaction vessel containing deionized water. A first co-precipitation reaction was carried out at 550 rpm and 60°C until the seed crystal particle size Dv50 reached 3 μm. Feeding was then stopped to obtain a ternary precursor seed slurry. The feed rate of the nickel-cobalt-manganese mixed salt solution was 30 mL / min. During the first co-precipitation reaction, the pH of the solution system was 11.5, and the ammonia concentration was 0.75 mol / L.

[0135] 40 vol% of the ternary precursor seed slurry was transferred to the second reactor, while the remaining ternary precursor seed slurry in the first reactor was used as the bottom solution and reacted for 2 hours under the conditions of passing through the nickel-cobalt-manganese mixed salt solution, the sodium hydroxide solution, and the ammonia water. After filtration, washing, and drying, the first ternary precursor was obtained. The feed rate of the nickel-cobalt-manganese mixed salt solution was 30 mL / min. During the reaction, the pH of the solution system was 11.5, the ammonia concentration was 0.75 mol / L, the reaction temperature was 60 °C, and the stirring rate was 550 rpm.

[0136] (2) Nickel sulfate, cobalt sulfate and manganese sulfate were prepared in a ratio of Ni:Co:Mn of 8:1:1 to obtain a second nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 0.9 mol / L.

[0137] The second nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, ammonia, 1 mol / L KHSO5 solution and 0.09 mol / L ethylenediaminetetraacetic acid solution were fed into the second reaction vessel in a parallel flow. The second coprecipitation reaction was carried out at 550 rpm and 60 °C for 2 h. After filtration, washing and drying, the second ternary precursor was obtained.

[0138] The feed rate of the second nickel-cobalt-manganese mixed salt solution is 15 mL / min; the feed rate of the KHSO5 solution is 8 mL / min, and the feed is stopped after 1 hour; the feed rate of the ethylenediaminetetraacetic acid solution is 15 mL / min, and the feed time is the same as that of the KHSO5 solution; during the second coprecipitation reaction, the pH of the solution system is 11, and the ammonia concentration of the solution system is 0.7 mol / L.

[0139] (3) The first ternary precursor, the second ternary precursor and lithium carbonate are mixed in a molar ratio of Li:(Ni+Co+Mn) of 1.05:1 and then calcined in an oxygen atmosphere at a heating rate of 3℃ / min in two steps to obtain the ternary cathode material.

[0140] In the two-step calcination process, the first calcination temperature is 350℃ and the holding time is 6h; the second calcination temperature is 780℃ and the holding time is 13h.

[0141] Example 12

[0142] The difference between this embodiment and Embodiment 1 is that, in step (2), the pH of the solution system is 11 during the second coprecipitation reaction; and no ethylenediaminetetraacetic acid solution is added. In step (4), the calcination temperature in the first step is 450°C.

[0143] The remaining preparation methods and parameters are consistent with those in Example 1.

[0144] Comparative Example 1

[0145] The difference between this comparative example and Example 1 is that step (2) is replaced by:

[0146] A second nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 0.9 mol / L was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a Ni:Co:Mn molar ratio of 8:1:1.

[0147] 20 vol% of the ternary precursor seed slurry was placed in the second reactor, and then the second nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, ammonia, 0.4 mol / L KHSO5 solution and 0.09 mol / L ethylenediaminetetraacetic acid solution were added in parallel. The second coprecipitation reaction was carried out at 550 rpm and 60 °C for 1 h. After the reaction was completed, the ternary precursor intermediate slurry was obtained.

[0148] The feed rate of the second nickel-cobalt-manganese mixed salt solution is 15 mL / min; the feed rate of the KHSO5 solution is 4 mL / min, and the feed is stopped after 0.5 h; the feed rate of the ethylenediaminetetraacetic acid solution is 15 mL / min, and the feed time is the same as that of the KHSO5 solution; during the second coprecipitation reaction, the pH of the solution system is 11, and the ammonia concentration of the solution system is 0.7 mol / L.

[0149] The remaining preparation methods and parameters are consistent with those in Example 1.

[0150] Comparative Example 2

[0151] This comparative example provides a method for preparing a ternary cathode material, the method comprising the following steps:

[0152] (1) Nickel sulfate, cobalt sulfate and manganese sulfate were prepared in a ratio of Ni:Co:Mn of 8:1:1 to obtain a nickel-cobalt-manganese mixed salt solution with a total transition metal ion concentration of 1.5 mol / L.

[0153] The nickel-cobalt-manganese mixed salt solution, 5 mol / L sodium hydroxide solution, and ammonia water were added concurrently to a reactor containing deionized water. A co-precipitation reaction was carried out at 550 rpm and 60°C for 20 h. After the reaction, the mixture was filtered, washed, and dried to obtain the ternary precursor. The feed rate of the first nickel-cobalt-manganese mixed salt solution was 35 mL / min. During the co-precipitation reaction, the pH of the solution system was 11.5, and the ammonia concentration was 0.75 mol / L.

[0154] (2) The ternary precursor and lithium carbonate are mixed in a molar ratio of Li:(Ni+Co+Mn) of 1.05:1 and then calcined in an oxygen atmosphere at a heating rate of 3℃ / min in two steps to obtain the ternary cathode material.

[0155] In the two-step calcination process, the first calcination temperature is 350℃ and the holding time is 6h; the second calcination temperature is 780℃ and the holding time is 13h.

[0156] Comparative Example 3

[0157] The difference between this comparative example and Example 1 is that in step (2), the KHSO5 solution is replaced with a Na2S2O8 solution of equal concentration.

[0158] The remaining preparation methods and parameters are consistent with those in Example 1.

[0159] Performance testing

[0160] I. Physical property tests were performed on the ternary cathode materials provided in the above embodiments and comparative examples, including:

[0161] (I) ∆S: After the sample to be tested was subjected to 5000 vibrations using a BT-302 tap density meter, the upper and lower particles were separated at a volume ratio of 1:1. The upper and lower particles were then pressed at 5T. The pore specific surface area of ​​the upper and lower particles after pressing was measured using a BSD-660S A6B6 with a pore size of 2-200nm. The relatively larger pore specific surface area was recorded as S1, and the relatively smaller pore specific surface area was recorded as S2.

[0162] The ∆S value of the corresponding ternary cathode material was calculated according to the formula ∆S=0.5×(S1+S2) / (S1-S2), and the results are shown in Table 1.

[0163] (II) ∆A: After the sample to be tested was subjected to 5000 vibrations using a BT-302 tap density meter, the upper and lower particles were separated at a volume ratio of 1:1. The peak areas of the characteristic X-ray diffraction peaks of the upper and lower particles on the (003) crystal plane were measured using an X-ray diffractometer (denoted as A). 上前 and A 下前 Then, the upper and lower particles were pressed at 5T respectively, and the peak areas of the characteristic X-ray diffraction peaks of the (003) crystal plane after pressing were measured using an X-ray diffractometer (denoted as A). 上压 and A 下压 ).

[0164] According to the formula ∆A=(|A 上前 -A 上压 | / A 上前 +|A 下前 -A 下压 | / A 下前 The ∆A value of the corresponding ternary cathode material was calculated by 1 / 2×100, and the results are shown in Table 1.

[0165] Table 1

[0166]

[0167] II. Based on the ternary cathode material provided in the above embodiments and comparative examples, a coin cell is fabricated using the following specific steps: ternary cathode material, acetylene black, and polyvinylidene fluoride are uniformly mixed in N-methylpyrrolidone at a mass ratio of 90:5:5, then coated onto aluminum foil, dried in a vacuum drying oven, and then pressed into a 12mm diameter cathode sheet using a sheet press in an argon glove box; the cathode sheet, polypropylene porous separator, negative lithium sheet, and electrolyte are assembled into a coin cell in the glove box; the solute in the electrolyte is LiPF6 with a concentration of 1mol / L, and the solvent is EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 1:1.

[0168] The coin cell was subjected to constant current charge-discharge testing using the LAND battery testing system to test the cycle stability of the ternary cathode material. The test voltage was 2.8V-4.3V and the test current density was 1C. The results are shown in Table 2.

[0169] Table 2

[0170]

[0171] analyze:

[0172] According to the data in Tables 1 and 2, a comparison between Example 1 and Comparative Examples 1-3 shows that if the ∆S value of the ternary cathode material is not within the protection range, the capacity performance and cycle stability of the battery made based on this ternary cathode material will both deteriorate.

[0173] The ∆S value, ∆A value, and ∆S / ∆A value of the ternary cathode materials provided in Examples 1-5 and Examples 8-10 are all within the range specified in this invention, and their discharge specific capacity and cycle stability are superior.

[0174] A comparison of Examples 1 and 6-7 shows that if the total concentration of transition metal ions in the second nickel-cobalt-manganese mixed salt solution is too high, the feed rate of the second nickel-cobalt-manganese mixed salt solution is too high, and the feed rate of the third nickel-cobalt-manganese mixed salt solution is too high, the ∆A of the obtained ternary cathode material will be greater than 20, and its cycle performance will deteriorate. If the concentration of KHSO5 solution is too low and the feed rate is too low, the ∆S / ∆A value of the obtained ternary cathode material will be lower than the protection range (0.7≤∆S / ∆A≤15), and its cycle performance will be poor.

[0175] A comparison of Examples 1 and 12 shows that if ethylenediaminetetraacetic acid is not added during the preparation of the ternary precursor intermediate slurry, and the pH of the solution system is too high during the second coprecipitation reaction, and the temperature of the first calcination step is too high during the subsequent two calcination processes, the resulting ternary cathode material will have ∆A > 20 and a ∆S / ∆A value that is too low, resulting in lower cycle performance and discharge specific capacity.

[0176] As can be seen from the comparison between Example 1 and Comparative Example 3, if the KHSO5 solution is replaced with Na2S2O8 solution of equal concentration, the OO bond of KHSO5 cannot be more easily activated by direct electron transfer from the metal active site. The generated ·OH is more significant and locally specific, causing the edge active sites of the ternary precursor grains to react, realizing the growth of the crystal boundary and obtaining a partial whisker growth layer. Ultimately, the ∆S value and ∆S / ∆A value of the ternary cathode material are lower than the protection range, and its cycle stability is poor.

[0177] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions 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 must meet at least the following requirements: ΔS≥4, ΔS=0.5×(S1+S2) / (S1-S2); Wherein, ∆S is the influence factor reflecting the gradient difference between pore specific surface area and dynamic structure-property ratio on the stacking effect of the material; S1 and S2 are both the pore specific surface areas of the ternary cathode material after densification treatment, and S1 > S2.

2. The ternary cathode material according to claim 1, characterized in that, The ∆S satisfies: 4≤∆S≤30; And / or, the apertures corresponding to S1 and S2 are 2-200 nm; And / or, the densification process includes sequential vibration separation and pressing processes, wherein the pressure applied during the pressing process is 4-6T.

3. The ternary cathode material according to claim 1, characterized in that, The ternary cathode material also meets the following requirements: ∆A≤20,∆A=(|A 上前 -A 上压 | / A 上前 +|A 下前 -A 下压 | / A 下前 ) / 2×100; Wherein, ∆A is the influence factor reflecting the effect of the gradient difference in dynamic structure-property ratio on the crystal orientation and microstructure of the material; A 上前 and A 下前 A represents the peak areas of the upper and lower particles of the ternary cathode material after vibration, respectively, at the characteristic peaks of the X-ray diffraction peaks on the (003) crystal plane. 上压 and A 下压 These are the peak areas of the X-ray diffraction characteristic peaks of the (003) crystal plane corresponding to the upper and lower particles after pressing.

4. The ternary cathode material according to claim 3, characterized in that, The condition ∆A satisfies: 1≤∆A≤20; And / or, the pressure applied during the pressing process is 4-6T.

5. The ternary cathode material according to claim 3 or 4, characterized in that, The ternary cathode material satisfies the following condition: 0.7 ≤ ∆S / ∆A ≤ 15.

6. A method for preparing a ternary cathode material as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: The first nickel-cobalt-manganese mixed salt solution, precipitant and complexing agent are added in parallel to the first reaction vessel containing the bottom liquid to carry out the first co-precipitation reaction and obtain ternary precursor seed slurry. A portion of the ternary precursor seed slurry is placed into the second reactor, and then a second nickel-cobalt-manganese mixed salt solution, a precipitant, a complexing agent, a persulfate solution, and a coordinating agent are added in parallel to carry out the second coprecipitation reaction to obtain the ternary precursor intermediate slurry. The remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed into the third reactor. Then, a third nickel-cobalt-manganese mixed salt solution, a precipitant, and a complexing agent are added in parallel to carry out the third co-precipitation reaction. After the reaction, post-processing is performed to obtain the ternary precursor. The ternary precursor and lithium source are mixed and calcined to obtain the ternary cathode material.

7. The preparation method according to claim 6, characterized in that, During the first coprecipitation reaction, the pH of the solution system is 11-12; And / or, in the ternary precursor seed slurry, the particle size Dv50 of the seed particles is 2-5 μm; And / or, the feed rate of the first nickel-cobalt-manganese mixed salt solution is greater than the feed rate of the second nickel-cobalt-manganese mixed salt solution.

8. The preparation method according to claim 6 or 7, characterized in that, The persulfate solution includes a KHSO5 solution; And / or, the concentration of the persulfate solution is 0.6-1.5 mol / L; And / or, the ligand comprises ethylenediaminetetraacetic acid and / or citric acid; And / or, the concentration of the ligand is 0.08-0.12 mol / L; And / or, the feed rate ratio of the persulfate solution to the complexing agent is (5-10):(10-20); And / or, during the second coprecipitation reaction, the pH of the solution system is 10-10.5; And / or, during the second coprecipitation reaction, the reaction time is 1-3 hours; And / or, the feed rate of the third nickel-cobalt-manganese mixed salt solution is 30-40 mL / min; And / or, during the third coprecipitation reaction, the pH of the solution system is 11.5-12.

9. The preparation method according to any one of claims 6-8, characterized in that, The preparation method includes the following steps: (1) The first nickel-cobalt-manganese mixed salt solution, alkaline solution and ammonia water are added in parallel to the first reaction vessel where the bottom liquid is located, and the first coprecipitation reaction is carried out at 400-700 rpm and 45-60℃ to obtain ternary precursor seed slurry; In the first nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5); the concentration of the first nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, and the feed rate is 20-35 mL / min; during the first coprecipitation reaction, the pH of the solution system is 11-12, and the ammonia concentration of the solution system is 0.65-0.9 mol / L; the concentration of the alkaline solution is 4-6 mol / L; and the particle size Dv50 of the seed crystals in the ternary precursor seed slurry is 2-5 μm. (2) The upper layer of the ternary precursor seed slurry is placed in the second reactor, and then the second nickel-cobalt-manganese mixed salt solution, alkaline solution, ammonia water, persulfate solution and complexing agent are added in parallel. The second coprecipitation reaction is carried out for 1-3 hours at 400-700 rpm and 45-60℃ to obtain the ternary precursor intermediate slurry. The upper slurry comprises 30-50 vol% of the ternary precursor seed slurry; the molar ratio of nickel ions, cobalt ions, and manganese ions in the second nickel-cobalt-manganese mixed salt solution is (5-95):(1-9):(1-5); the concentration of the second nickel-cobalt-manganese mixed salt solution is 0.8-1.2 mol / L, and the feed rate is 10-20 mL / min; the persulfate solution includes KHSO5 solution; the concentration of the persulfate solution is 0.6-1.5 mol / L, and the feed rate is 5-10 mL / min; the ligand includes ethylenediaminetetraacetic acid and / or citric acid; the concentration of the ligand is 0.08-0.12 mol / L, and the feed rate is 10-20 mL / min; during the second coprecipitation reaction, the pH of the solution system is 10-10.5, the ammonia concentration of the solution system is 0.65-0.9 mol / L; and the concentration of the alkaline solution is 4-6 mol / L. (3) The remaining ternary precursor seed slurry in the first reactor is mixed with the ternary precursor intermediate slurry and placed in the third reactor. Then, the third nickel-cobalt-manganese mixed salt solution, alkaline solution and ammonia water are added in parallel. The third coprecipitation reaction is carried out for 1-3 hours at 400-700 rpm and 45-60℃. Then, the ternary precursor is obtained by post-processing. In the third nickel-cobalt-manganese mixed salt solution, the molar ratio of nickel ions, cobalt ions, and manganese ions is (5-95):(1-9):(1-5); the concentration of the third nickel-cobalt-manganese mixed salt solution is 1.5-2.2 mol / L, and the feed rate is 30-40 mL / min; during the third coprecipitation reaction, the pH of the solution system is 11.5-12, the ammonia concentration of the solution system is 0.65-0.9 mol / L; and the concentration of the alkaline solution is 4-6 mol / L. (4) The ternary precursor and the lithium source are mixed and calcined to obtain the ternary cathode material; The molar ratio of the transition metal element in the ternary precursor to the lithium metal element in the lithium source is 1:(1.02-1.05); the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium oxalate; the calcination treatment is carried out in an oxygen-containing atmosphere; the calcination treatment includes a first calcination and a second calcination performed by sequentially increasing the temperature; the temperature of the first calcination is 300-350℃, and the holding time is 5-7h; the temperature of the second calcination is 750-800℃, and the holding time is 12-15h.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery includes the ternary positive electrode material as described in any one of claims 1-5.

Images