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

Abstract

The invention discloses a ternary precursor and a preparation method thereof, a ternary positive electrode material and a lithium ion battery, and relates to the technical field of lithium ion batteries. The initial dehydroxylation temperature of the ternary precursor provided by the invention is 150 DEG C or above, the dehydroxylation speed v is 0.5-2.0 g / (g.DEG C), the ternary precursor has relatively proper dehydroxylation speed and relatively proper sintering activity, the performance of the polycrystalline ternary positive electrode material obtained by sintering is favorably improved, and the polycrystalline ternary positive electrode material has the advantages of low lithium-nickel mixed arrangement, large gram capacity, good cycle performance and the like.

Description

Technical Field

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

[0002] Lithium nickel cobalt manganese oxide (NCM) ternary cathode materials have become one of the mainstream power battery cathode materials due to their advantages such as high specific capacity, high discharge voltage, high energy density, and good rate performance, which can provide new energy vehicles with longer driving range and faster charging speed, occupying a large market share. Among them, ternary polycrystalline materials are more widely used because of their higher energy density, rate performance, and more mature processing technology.

[0003] However, polycrystalline ternary cathode materials suffer from problems such as lithium-nickel mixing, oxygen loss, and irreversible phase conversion. To address these issues, methods such as doping, coating, and precursor structure optimization are commonly employed. Among these, precursor structure optimization offers more solutions to overcome these shortcomings. Taking hydroxide precursors as an example, the process of preparing cathode materials from precursors is roughly as follows: nickel-cobalt-manganese hydroxide is mixed with a lithium source and then calcined in an oxygen-containing atmosphere. After crushing, demagnetization, and sieving, the cathode material is obtained. During calcination, at a lower temperature, nickel-cobalt-manganese hydroxide loses hydroxyl groups to obtain a solid solution of nickel-cobalt-manganese oxide, while the lithium source loses carbon dioxide (lithium carbonate) or hydroxyl groups (lithium hydroxide) to obtain lithium oxide. Then, at a higher temperature, nickel-cobalt-manganese oxide and lithium oxide fuse, and lithium ions migrate and embed into the crystal lattice, forming a layered structure. Therefore, the progress of each stage during calcination affects the properties of the obtained cathode material. Adjusting the sintering activity of nickel-cobalt-manganese hydroxide is beneficial for preparing polycrystalline cathode materials with low lithium-nickel mixing, high crystallinity, and high particle sphericity.

[0004] Therefore, there is an urgent need to develop nickel-cobalt-manganese hydroxides with suitable sintering activity to improve the performance of polycrystalline ternary cathode materials obtained by sintering, including low lithium-nickel mixing, high crystallinity, high particle sphericity, excellent coating performance, and large specific capacity.

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

[0006] The purpose of this invention is to provide a ternary precursor and its preparation method, a ternary cathode material, and a lithium-ion battery. The aim is to provide a nickel-cobalt-manganese hydroxide with suitable sintering activity, thereby improving the performance of the polycrystalline ternary cathode material obtained by sintering.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a ternary precursor, which is a nickel-cobalt-manganese hydroxide, wherein the dehydroxylation initiation temperature of the ternary precursor is above 150°C and the dehydroxylation rate v is 0.5~2.0 g / (g·°C). The test procedure for the dehydroxylation rate is as follows: The ternary precursor and acetylene black are mixed at a mass ratio of 1:0.25 and then subjected to thermogravimetric analysis. The test conditions are a nitrogen atmosphere, a temperature range of 25℃~1000℃, and a heating rate of 2° / min. Dehydroxylation rate v = W / T × 1000; In the formula, W represents the weight loss ratio corresponding to the maximum weight loss peak of the differential thermogravimetric curve below 400℃, with the unit being g / g; T represents the temperature range corresponding to the onset and termination temperatures of the maximum weight loss peak below 400℃ in the thermogravimetric curve obtained from the thermogravimetric test, with the unit being ℃.

[0008] In an optional implementation, the reduction initiation temperature of the ternary precursor is 600℃~950℃, and the reduction initiation temperature is determined by the tangent method for the maximum weight loss peak above 600℃ on the differential thermogravimetric curve. And / or, the temperature range T is 60℃~200℃; And / or, the weight loss ratio W ranges from 0.09 g / g to 0.19 g / g; And / or, the particle size D50 of the ternary precursor is 5 μm to 15 μm; And / or, the dehydroxylation rate v / D50 = (0.05~0.35) / (℃·μm); And / or, the acetylene black used conforms to GB / T 3782-2016; And / or, the chemical formula of the ternary precursor is Ni x Co y Mn z M 1-x-y-z (OH) 2+e M is selected from one or more of Al, Ti, Ca, Sr, Ba, Zr, Y, La, Ce, Sm, Er, Mg, Nb, Ta, Mo, W and Zn; 1 / 3≤x<1, 0<y<1, 0<z<1, 0≤e≤0.06, 0≤1-xyz≤0.2.

[0009] Secondly, the present invention provides a method for preparing any of the ternary precursors in the foregoing embodiments, comprising: Synthetic seed crystals: Nickel-cobalt-manganese hydroxide seed crystals with a particle size D50 of 2 μm to 4 μm were prepared by co-precipitation method; Precursor preparation: Co-precipitation reaction was continued using nickel cobalt manganese hydroxide seed crystals until the particle size D50 of the intermediate particles was 2.5 μm to 6.1 μm; Quaternized polyethyleneimine was added to continue growth, resulting in precursor particles with a particle size D50 of 5 μm to 15 μm.

[0010] In an optional embodiment, the process of synthesizing seed crystals includes: preparing a base liquid in a reactor, introducing a nickel-cobalt-manganese mixed metal salt solution, a complexing agent solution, and a precipitant solution into the reactor for a co-precipitation reaction, stopping the feeding after the material particle size D50 grows to 2μm~4μm, and separating to obtain seed crystals; wherein, the complexing agent solution is an ammonia solution.

[0011] In an optional implementation, the process of synthesizing seed crystals has at least one of the following features 1-6: Feature 1: The pH value of the base solution is 11~12, and the pH value of the reaction system is controlled at 11~12 during the reaction process; Feature 2: The precipitant solution is an aqueous solution of sodium hydroxide; Feature 3: The ammonia concentration in the base solution is controlled at 8 g / L to 10 g / L, and the ammonia concentration in the reaction system is controlled at 8 g / L to 10 g / L during the reaction process; Feature 4: The total concentration of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is 1.5M~2.5M, and the feed rate of the nickel-cobalt-manganese mixed metal salt solution is 50mL / min~70mL / min; Feature 5: The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is (0.5~0.95):(0.02~0.3):(0.02~0.3). Feature 6: The reaction is carried out under an inert atmosphere at a temperature of 55℃-70℃.

[0012] In an optional embodiment, the process of preparing intermediate particles includes: adding seed crystals to a reaction vessel and mixing with glycine-sodium hydroxide buffer solution, then introducing a nickel-cobalt-manganese mixed metal salt solution, a complexing agent solution, and a precipitant solution to react, controlling the reaction pH to be 8-9 and the ammonia concentration to be 4 g / L-6 g / L; the pH of the glycine-sodium hydroxide buffer solution is 8.6-9.6. And / or, during the preparation of intermediate particles, the feed rate of the nickel-cobalt-manganese mixed metal salt solution is 90 mL / min to 120 mL / min.

[0013] In an optional embodiment, after adding quaternized polyethyleneimine, the feed rate of the nickel-cobalt-manganese mixed metal salt solution is adjusted to 50 mL / min to 70 mL / min, the reaction pH is 10 to 11, and the ammonia concentration is 4 g / L to 6 g / L. And / or, when the particle size D50 in the reaction slurry reaches 5μm~15μm, it is aged, then the solid and liquid are separated, and the obtained solid material is washed and dried; And / or, the amount of quaternized polyethyleneimine added is 1wt% to 5wt% of the solid content of the system; And / or, the number average molecular weight of the added quaternized polyethyleneimine is 20kDa~60kDa; And / or, the degree of quaternization of quaternized polyethyleneimine is 40% to 55%.

[0014] In an optional embodiment, the preparation process of quaternized polyethyleneimine includes: adding propylene oxide solution dropwise to polyethyleneimine solution under reaction conditions of 5℃~10℃, reacting for 5h-12h, and then distilling under reduced pressure to obtain tertiary amination polyethyleneimine; mixing and dissolving the tertiary amination polyethyleneimine with a halogenated product, and then carrying out a quaternization reaction at 40℃~60℃ for 40h-60h, followed by purification and drying to obtain quaternized polyethyleneimine; The halogenated product is selected from at least one of iodomethane and benzyl chloride; The molar ratio of nitrogen to propylene oxide in polyethyleneimine is 1:(0.8-1.1); the molar ratio of nitrogen to iodomethane in tertiary amination polyethyleneimine is 1:(0.4-0.8).

[0015] Thirdly, the present invention provides a ternary cathode material, which is prepared from any of the ternary precursors in the foregoing embodiments or from any of the preparation methods in the foregoing embodiments.

[0016] Fourthly, the present invention provides a lithium-ion battery comprising the ternary cathode material of the aforementioned embodiments.

[0017] The present invention has the following beneficial effects: the ternary precursor provided by the present invention has a dehydroxylation initiation temperature of above 150℃ and a dehydroxylation rate v of 0.5~2.0g / (g·℃), which has a suitable dehydroxylation rate and suitable sintering activity. This is beneficial to improving the performance of the polycrystalline ternary cathode material obtained by sintering, so that the polycrystalline ternary cathode material has the advantages of low lithium-nickel mixing, large specific capacity, and good cycle performance.

[0018] It should be noted that if the dehydroxylation rate of nickel-cobalt-manganese hydroxide is too fast, it will lead to excessive water evaporation and lithium loss. Furthermore, it can cause the primary particles on the outer surface to fuse due to dehydroxylation, making it difficult to remove internal hydroxyl groups, resulting in an uneven particle structure. This, in turn, hinders the sufficient diffusion of Li, exacerbates lithium-nickel mixing, reduces crystallinity, and makes the particle surface overly smooth. Conversely, if the dehydroxylation rate of nickel-cobalt-manganese hydroxide is too slow, it will lead to a longer sintering time and increased energy consumption. Under the same sintering conditions, particles with slower dehydroxylation rates exhibit poorer uniformity of primary particles, lower crystallinity, and more internal porosity, resulting in decreased specific capacity and increased particle surface roughness. The surface roughness or smoothness of the cathode particles not only affects the flowability of the cathode slurry, thus affecting the performance of the electrode (such as compaction density and uniformity), but also the stability of the coating layer. Excessive roughness or smoothness is detrimental to the formation of a stable and uniform coating layer. Attached Figure Description

[0019] 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.

[0020] Figure 1 The weight loss curve and derivative thermogravimetric curve of the ternary precursor provided in Embodiment 6 of the present invention are shown. Detailed Implementation

[0021] 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.

[0022] This invention provides a ternary precursor, which is a nickel-cobalt-manganese hydroxide. The ternary precursor has a dehydroxylation initiation temperature of over 150°C and a dehydroxylation rate v of 0.5~2.0 g / (g·°C). The ternary precursor provided by this invention has high sintering activity, and the prepared cathode material particles have a high degree of surface smoothness, and have advantages such as low lithium-nickel mixing, large specific capacity, and good cycle performance.

[0023] Specifically, the dehydroxylation initiation temperature of the ternary precursor can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc. The dehydroxylation rate v can be 0.5g / (g·℃), 0.8g / (g·℃), 1.0g / (g·℃), 1.3g / (g·℃), 1.5g / (g·℃), 1.8g / (g·℃), 2.0g / (g·℃), etc.

[0024] The test procedure for the dehydroxylation rate is as follows: The ternary precursor and acetylene black are mixed at a mass ratio of 1:0.25 and then subjected to thermogravimetric analysis (TGA). The test conditions are a nitrogen atmosphere, a temperature range of 25℃ to 1000℃, and a heating rate of 2° / min. The weight loss curve and the derivative TGA curve can be obtained through the TGA test, as shown below. Figure 1 As shown. The dehydroxylation rate is calculated as follows: Dehydroxylation rate v = W / T × 1000; where W represents the weight loss ratio corresponding to the maximum weight loss peak below 400℃ obtained from the thermogravimetric analysis (TGA), in g / g; T represents the temperature range corresponding to the weight loss onset temperature and weight loss termination temperature of the maximum weight loss peak below 400℃ obtained from the TGA, in °C. The acetylene black used in the test method of this embodiment conforms to GB / T 3782-2016.

[0025] In some embodiments, the temperature range T is 60℃ to 200℃, determined from the differential thermogravimetric curve, and can be 60℃, 80℃, 100℃, 130℃, 150℃, 180℃, 200℃, etc. The weight loss ratio W is 0.09g / g to 0.19g / g, and can be 0.09g / g, 0.10g / g, 0.13g / g, 0.15g / g, 0.18g / g, 0.19g / g, etc.

[0026] It should be noted that the process of preparing the cathode material from the precursor is roughly as follows: nickel cobalt manganese hydroxide is mixed with a lithium source, then calcined in an oxygen-containing atmosphere, followed by crushing, demagnetization, and sieving to obtain the cathode material. During the calcination process, at a relatively low temperature, the nickel cobalt manganese hydroxide undergoes dehydroxylation to obtain a solid solution of nickel cobalt manganese oxide (Ni... x Co y Mn z M (1-x-y-z) (OH)₂ + 1 / 6O₂ → Ni x Co y Mn z M (1-x-y-z) O 4 / 3+H2O↑), lithium source removes carbon dioxide (lithium carbonate) or hydroxyl groups (lithium hydroxide) to obtain lithium oxide; then at a higher temperature, nickel cobalt manganese oxide and lithium oxide fuse, lithium ions migrate and embed into the lattice to form a layered structure.

[0027] If the dehydroxylation rate of nickel-cobalt-manganese hydroxide is too fast, it will lead to excessive water evaporation and lithium loss. Furthermore, it can cause the primary particles on the outer surface to fuse due to dehydroxylation, making it difficult to remove internal hydroxyl groups, resulting in an uneven particle structure. This, in turn, hinders Li diffusion, exacerbates lithium-nickel mixing, reduces crystallinity, and makes the particle surface too smooth. Conversely, if the dehydroxylation rate of nickel-cobalt-manganese hydroxide is too slow, it will lead to a longer sintering time and increased energy consumption. Under the same sintering conditions, particles with slower dehydroxylation rates exhibit poorer uniformity of primary particles, lower crystallinity, and more internal porosity, resulting in decreased specific capacity and increased particle surface roughness. The surface roughness or smoothness of the cathode particles not only affects the flowability of the cathode slurry, thus affecting the performance of the electrode (such as compaction density and uniformity), but also the stability of the coating layer. Excessive roughness or smoothness is detrimental to the formation of a stable and uniform coating layer.

[0028] To analyze the dehydroxylation rate of nickel-cobalt-manganese hydroxide, it was mixed with excess acetylene black and subjected to thermogravimetric analysis (TGA) under a nitrogen atmosphere. The presence of nitrogen and acetylene black inhibited the oxidation of nickel, cobalt, and manganese, allowing only dehydroxylation and dehydration to occur, thus enabling the analysis of the dehydroxylation rate. The dehydroxylation rate was obtained by analyzing the weight loss curve and the derivative thermogravimetric curve. The temperature range required to remove all hydroxyl groups at a heating rate of 2℃ / min was calculated, reflecting the weight loss per unit temperature during the dehydroxylation stage of nickel-cobalt-manganese hydroxide. The following process occurs: Ni x Co y Mn z M (1-x-y-z) (OH)2→Ni x Co y Mn z M (1-x-y-z) O + H₂O↑.

[0029] As the temperature rises, a reduction reaction occurs above 600℃, producing CO and resulting in weight loss, i.e., Ni. x Co y Mn z M (1-x-y-z)O + C → xNi + yCo + zMn + (1-xyz)M + CO↑. Since the reduction reaction between nickel cobalt manganese oxide solid solution and C is a solid-solid reaction, its ease of reaction is influenced by both the chemical energy barrier and the degree of contact between particles. The former is determined by the chemical reaction mechanism itself; the latter is determined by the state of the particles, such as the morphology and crystallinity of the nickel cobalt manganese oxide solid solution. Therefore, examining the reduction initiation temperature of nickel cobalt manganese hydroxide and C can, to a certain extent, evaluate the solid-solid reaction efficiency of nickel cobalt manganese hydroxide.

[0030] In some embodiments, the particle size D50 of the ternary precursor is 5 μm to 15 μm, such as 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, etc. The dehydroxylation rate v / D50 = (0.05~0.35) / (℃·μm), such as 0.05 / (℃·μm), 0.06 / (℃·μm), 0.08 / (℃·μm), 0.10 / (℃·μm), 0.13 / (℃·μm), 0.15 / (℃·μm), 0.18 / (℃·μm), 0.20 / (℃·μm), 0.23 / (℃·μm), 0.25 The particle size D50 is calculated in μm, with values ​​such as 0.28 / (℃·μm), 0.30 / (℃·μm), 0.33 / (℃·μm), and 0.35 / (℃·μm). It should be noted that the dehydroxylation rate v is calculated in g / (g·℃). For simplicity, g / g is canceled out when calculating the dehydroxylation rate v / D50; therefore, the unit for the dehydroxylation rate v / D50 is (℃·μm). -1 The particle size of the ternary precursor has a certain influence on its dehydroxylation rate. For the same mass, the larger the particle size of the ternary precursor, the slower the dehydroxylation rate. By adjusting the dehydroxylation rate v / D50 to meet the above range, it is beneficial to obtain a ternary precursor with suitable sintering activity, thereby improving the performance of the polycrystalline ternary cathode material obtained by sintering.

[0031] In some embodiments, the reduction initiation temperature is 600℃~950℃, such as 600℃, 650℃, 680℃, 700℃, 730℃, 750℃, 780℃, 800℃, 830℃, 850℃, 880℃, 900℃, 930℃, 950℃, etc. Figure 1 As shown, the reduction initiation temperature was determined by the tangent method for the maximum weight loss peak above 600℃ in the thermogravimetric curve of the micro-merchant.

[0032] In some embodiments, the chemical formula of the ternary precursor is Ni x Co y Mn z M 1-x-y-z (OH) 2+eM is selected from one or more of Al, Ti, Ca, Sr, Ba, Zr, Y, La, Ce, Sm, Er, Mg, Nb, Ta, Mo, W and Zn, and M can be any one or more of the above; 1 / 3≤x<1, 0<y<1, 0<z<1, 0≤e≤0.06, 0≤1-xyz≤0.2.

[0033] This invention also provides a method for preparing a ternary precursor, the steps of which are as follows: S1, Synthetic Seed Crystal Nickel-cobalt-manganese hydroxide seed crystals with a particle size D50 of 2 μm to 4 μm were prepared by co-precipitation and used in step S2 to prepare the precursor. Specifically, the particle size D50 of the nickel-cobalt-manganese hydroxide seed crystals can be 2.0 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3.0 μm, 3.3 μm, 3.5 μm, 3.8 μm, 4.0 μm, etc.

[0034] In some embodiments, the process of synthesizing seed crystals includes: preparing a base solution in a reactor; introducing a nickel-cobalt-manganese mixed metal salt solution, a complexing agent solution, and a precipitant solution into the reactor under an inert atmosphere for a co-precipitation reaction; allowing the solid particles to gradually grow; stopping the feeding when the particle size D50 reaches 2μm~4μm; and separating the seed crystals. The complexing agent solution can be an ammonia solution, but is not limited to it. The precipitant solution can be an aqueous sodium hydroxide solution, but is not limited to it, as long as it can be used to control the pH value of the reaction. The type of inert atmosphere is not limited, such as nitrogen or argon, etc. The reaction temperature is controlled at 55℃-70℃ during the reaction process, such as 55℃, 60℃, 65℃, 70℃, etc.

[0035] Furthermore, the base solution is obtained by mixing water, a complexing agent solution, and a precipitant solution. The pH value of the base solution is 11-12, such as 11.0, 11.3, 11.5, 11.8, 12.0, etc.; the ammonia concentration in the base solution is 8 g / L-10 g / L, such as 8.0 g / L, 8.5 g / L, 9.0 g / L, 9.5 g / L, 10.0 g / L, etc. Similarly, during the co-precipitation reaction, the pH value of the reaction system is controlled to be 11-12, such as 11.0, 11.3, 11.5, 11.8, 12.0, etc.; the ammonia concentration of the reaction system is controlled to be 8 g / L-10 g / L, such as 8.0 g / L, 8.5 g / L, 9.0 g / L, 9.5 g / L, 10.0 g / L, etc.

[0036] Furthermore, the total concentration of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is 1.5M to 2.5M, such as 1.5M, 1.8M, 2.0M, 2.3M, 2.5M, etc. The feed rate of the nickel-cobalt-manganese mixed metal salt solution is 50mL / min to 70mL / min, such as 50mL / min, 55mL / min, 60mL / min, 65mL / min, 70mL / min, etc. The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is (0.5~0.95):(0.02~0.3):(0.02~0.3), such as 0.5:0.3:0.2, 0.5:0.2:0.3, 0.6:0.2:0.2, 0.7:0.2:0.1, 0.8:0.1:0.1, 0.9:0.02:0.08, 0.95:0.03:0.02, etc. By adjusting the concentration and feed rate of the nickel-cobalt-manganese mixed metal salt solution, the particle growth rate can be controlled, ensuring uniform growth of the precursor particles.

[0037] S2. Preparation of precursor Co-precipitation reaction was continued using nickel-cobalt-manganese hydroxide seed crystals, and the particle size D50 of the intermediate particles was 2.5 μm to 6.1 μm. Quaternized polyethyleneimine was added to continue growth, and precursor particles with a particle size D50 of 5 μm to 15 μm were obtained. Specifically, the particle size D50 of the intermediate particles can be 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm, 5.0μm, 5.5μm, 6.0μm, 6.1μm, etc.; the particle size D50 of the precursor particles can be 5.0μm, 5.5μm, 6.0μm, 6.5μm, 7.0μm, 7.5μm, 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10.0μm, 10.5μm, 11.0μm, 11.5μm, 12.0μm, 12.5μm, 13.0μm, 13.5μm, 14.0μm, 14.5μm, 15.0μm, etc.

[0038] It should be noted that in the layered metal hydroxide crystal structure, the transition metal ion is located at the center of the octahedron, surrounded by an octahedron structure composed of six unsaturated hydroxyl ions. Adjacent octahedra are connected by sharing edges to form the transition metal layer. The high concentration of unsaturated hydroxyl ions on the (001) crystal face gives it a negative charge, attracting NH4 in the electrostatic system. + Approaching and neutralizing part of the negative charge, in NH4 + Passivation of the (001) crystal plane leads to the formation of complexes between transition metals and ammonium ions, including Ni(NH3). i 2+ Co(NH3) j 2+ And Mn(NH3) k 2+With OH in solution After the displacement precipitation reaction, the nanosheets are deposited along the ab plane, forming hexagonal nanosheets dominated by the (001) crystal plane. As the reaction proceeds, to reduce surface energy, the nanosheets spontaneously stack, forming primary particles composed of multiple stacked nanosheets. To reduce the number of stacked nanosheets, quaternized polyethyleneimine is added as a passivating agent for the (001) crystal plane. Due to its high positive charge density and large molecular steric hindrance, it can significantly reduce the surface energy of the nanosheets and inhibit their stacking. Simultaneously, the high positive charge density and large molecular steric hindrance limit the formation of Ni(NH3)i 2+ Co(NH3)j 2+ and Mn(NH3)k 2+ The proximity of the particles prevents excessive growth in the ab plane, thereby refining the primary particle size.

[0039] By suppressing the stacking of nanosheets, the exposure of the (001) crystal plane can be increased, thereby accelerating the dehydroxylation rate; however, it also restricts the growth of the ab plane and refines the primary particles, which means that the exposure of the crystal plane perpendicular to the (001) crystal plane is increased, thereby slowing down the insertion / extraction rate. Under the combined effect of the above two aspects, the dehydroxylation rate of the precursor material is maintained within a suitable range.

[0040] In some embodiments, the process of preparing intermediate particles includes: adding the seed crystals obtained in step S1 to a reaction vessel and mixing them with a glycine-sodium hydroxide buffer solution with a pH of 8.6-9.6; introducing a nickel-cobalt-manganese mixed metal salt solution, a complexing agent solution, and a precipitant solution to react; controlling the reaction pH to 8-9, the ammonia concentration to 4 g / L-6 g / L, and the feed rate of the nickel-cobalt-manganese mixed metal salt solution to 90 mL / min-120 mL / min. By adjusting the pH value, ammonia concentration, and feed rate of the nickel-cobalt-manganese mixed metal salt solution, the particle growth rate is controlled to prevent it from being too fast, which is beneficial for refining the primary particles and making the internal pores uniform.

[0041] Specifically, during the preparation of intermediate particles, the reaction pH can be controlled at 8.0, 8.3, 8.5, 8.8, 9.0, etc., and the ammonia concentration can be 4.0 g / L, 4.5 g / L, 5.0 g / L, 5.5 g / L, 6.0 g / L, etc. The feed rate of the nickel-cobalt-manganese mixed metal salt solution can be 90 mL / min, 95 mL / min, 100 mL / min, 105 mL / min, 110 mL / min, 115 mL / min, 120 mL / min, etc. Glycine-sodium hydroxide buffer refers to an aqueous solution formed by glycine and sodium hydroxide. For example, the preparation process of a glycine-sodium hydroxide buffer with a pH of 9 is as follows: Weigh approximately 7.5 g of glycine, dissolve it in approximately 800 mL of water, and titrate with 1 M NaOH solution to pH 9.0 while stirring.

[0042] In some embodiments, after adding quaternized polyethyleneimine, the feed rate of the nickel-cobalt-manganese mixed metal salt solution is adjusted to 50 mL / min to 70 mL / min, such as 50 mL / min, 55 mL / min, 60 mL / min, 65 mL / min, 70 mL / min, etc.; the reaction pH value is 10 to 11, such as 10.0, 10.3, 10.5, 10.8, 11.0, etc.; the ammonia concentration is 4 g / L to 6 g / L, such as 4.0 g / L, 4.5 g / L, 5.0 g / L, 5.5 g / L, 6.0 g / L, etc. Adding quaternized polyethyleneimine increases the pH value and decreases the feed rate of the nickel-cobalt-manganese mixed metal salt solution, which is beneficial for refining the primary particle size. When the particle size D50 in the reaction slurry reaches 5 μm to 15 μm, aging is performed, followed by solid-liquid separation by filtration or other methods. The obtained solid material is then washed and dried. There are no restrictions on the washing method; if it can be washed with water, it can be washed multiple times.

[0043] In some embodiments, the amount of quaternized polyethyleneimine added is 1 wt% to 5 wt% of the solid content of the system, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc. "Solid content" refers to the total mass fraction of materials other than water in the system before the addition of quaternized polyethyleneimine. The number average molecular weight (Mn) of the added quaternized polyethyleneimine is 20 kDa to 60 kDa, such as 20 kDa, 30 kDa, 40 kDa, 50 kDa, 60 kDa, etc. The degree of quaternization (silver nitrate titration method) of the quaternized polyethyleneimine is 40% to 55%, such as 40%, 45%, 50%, 55%, etc.

[0044] Furthermore, quaternized polyethyleneimine can be prepared independently. The preparation process includes: (1) adding propylene oxide solution dropwise to polyethyleneimine solution under reaction conditions of 5℃~10℃, reacting for 5h-12h, and then distilling under reduced pressure to obtain tertiary amination polyethyleneimine; (2) mixing and dissolving tertiary amination polyethyleneimine with a halogenated product, and then carrying out a quaternization reaction at 40℃~60℃ for 40h-60h, and obtaining quaternized polyethyleneimine after purification and drying; wherein, the halogenated product is selected from at least one of iodomethane and benzyl chloride, and the halogenated product can be any one or more of the above. The molar ratio of nitrogen (N) to propylene oxide in polyethyleneimine is 1:(0.8-1.1), such as 1:0.8, 1:0.9, 1:1.0, 1:1.1, etc.; the molar ratio of nitrogen (N) to iodomethane in tertiary amination polyethyleneimine is 1:(0.4-0.8), such as 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, etc.

[0045] Specifically, the solvents used in step (1) to prepare the propylene oxide solution and the polyethyleneimine solution can both be N,N-dimethylformamide (DMF), but are not limited to this. The reaction temperature in step (1) can be 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, etc., and the reaction time can be 5h, 8h, 10h, 12h, etc.

[0046] Specifically, the solvent used in step (2) can be anhydrous ethanol, but is not limited to it. The reaction temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, etc.; the reaction time can be 40h, 45h, 50h, 55h, 60h, etc.

[0047] This invention also provides a ternary cathode material, prepared from the ternary precursor provided in this invention, which has advantages such as low lithium-nickel mixing, high crystallinity, high particle sphericity, excellent coating performance, and large specific capacity.

[0048] This invention also provides a positive electrode sheet, including the above-mentioned ternary positive electrode material, and may further include a positive electrode current collector, wherein 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.

[0049] 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 with good electrochemical performance.

[0050] Specifically, the types of negative electrode, electrolyte, and separator are not limited. During the charging and discharging process of a secondary battery, active ions are inserted and removed back and forth between the positive and negative electrode, while the electrolyte plays the role of conducting ions between the positive and negative electrode.

[0051] In other embodiments, the lithium-ion battery is not limited to any particular form and can take the form of a battery module, battery pack, etc.

[0052] 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.

[0053] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0054] First, the testing methods for each parameter will be explained: [Precursor] Particle size: D50 was determined according to GB / T 19077-2016.

[0055] Thermogravimetric analysis (TGA): A Netzsch STA449F3 simultaneous thermal analyzer was used. The precursor and acetylene black were dried separately in an oven at 120℃ for 24 h. Then, the precursor and acetylene black were mixed at a mass ratio of 1:0.25 and used as the test sample. The test conditions were a nitrogen atmosphere, a temperature range of 25~1000℃, and a heating rate of 2° / min. The weight loss curves were obtained, and the derivative thermogravimetric curves were obtained by taking the first derivative of the weight loss curves. The acetylene black used conformed to GB / T 3782-2016.

[0056] Dehydroxylation initiation temperature: The tangent method is used to determine the initiation temperature of the maximum weight loss peak below 400℃ on the thermogravimetric curve of the micro-quotient. The tangent method refers to drawing the extension line of the baseline before weight loss and the tangent line at the inflection point of the curve after weight loss, and taking the intersection of the extension line and the tangent line as the dehydroxylation initiation temperature.

[0057] Dehydroxylation rate: The tangent method is used to determine the starting temperature and ending temperature of weight loss of the maximum weight loss peak below 400℃ on the thermogravimetric curve of the micro-merchant. The difference between the two is the temperature range. The difference between the corresponding weight loss rates on the weight loss curve is the weight loss ratio (g / g). Dehydroxylation rate (g / (g·℃)) v = (weight loss ratio W / temperature range T) × 1000.

[0058] Reduction initiation temperature: The reduction initiation temperature was determined by the tangent method for the maximum weight loss peak above 600℃ on the thermogravimetric curve of the micro-merchant.

[0059] XRD: Ultima IV X-ray powder diffractometer was used. Scanning mode: continuous scanning, scanning speed 0.02° / s. Jade software was used for full spectrum fitting.

[0060] [Cathode Material] All precursor samples were sintered in the following manner to obtain the cathode material, which was then tested.

[0061] Cathode material preparation method: The precursor and battery-grade lithium carbonate are mixed at a ratio of n(M'):n(Li)=1:1.08 (M' includes Ni, Co, Mn and M). After being placed in a bowl, the mixture is fed into a roller kiln and heated to 450℃ at a rate of 1℃ / min and held for 4 hours. Then, the temperature is increased to 800℃ at a rate of 2℃ / min and held for 12 hours to obtain a first-burned material. The first-burned material is coarsely crushed and finely crushed, and then uniformly mixed with Al2O3. The amount of Al added is 1500ppm based on the weight of the crushed material. The mixture is then sintered again at 550℃ in an oxygen atmosphere to obtain the cathode material.

[0062] XRD: Ultima IV X-ray powder diffractometer was used. Scanning mode: continuous scanning, scanning speed 0.02° / s. Jade software was used for full spectrum fitting to obtain I(003) / I(104). Fullprof was used to refine the Li / Ni mixing ratio in the material.

[0063] SEM: A Nova NanoSEM 450 scanning electron microscope was used.

[0064] [Electrochemical Performance] Battery assembly shall be carried out in accordance with GB / T 37207-2018, and some conditions shall be selected as follows: positive electrode active material: carbon black conductive agent: graphite conductive agent: PVDF = 95:2:1:2; the solid content of the positive electrode slurry shall be 40%; conditions not specifically specified shall be set in accordance with the general conditions of GB / T37207-2018.

[0065] The assembled batteries were tested for initial discharge specific capacity according to GB / T 37201-2018 and cycle stability according to GB / T 37207-2018. Cycle stability was evaluated by discharge capacity retention rate (500th discharge capacity ÷ 1st discharge capacity × 100%). The discharge rate was 0.2C and the test temperature was 25℃.

[0066] Table 1. Parameters of the precursors provided in each embodiment and comparative example.

[0067] Table 2. Results of cathode materials and electrochemical performance

[0068] The dehydroxylation initiation temperature of Comparative Example 1 was too low, which resulted in a large difference in the conversion rate of the ternary precursor and the lithium source to oxides during sintering with the lithium source. This was not conducive to the fusion of the two, leading to a decrease in lithium-ion diffusion capacity and a high Li / Ni mixing ratio, which in turn affected capacity and cycle performance.

[0069] The excessively rapid dehydroxylation rate in Comparative Example 2 resulted in poor sintering uniformity during mixing and sintering with the lithium source. The premature dehydration of the outer surface of the particles led to the formation of a solid solution, making it difficult for internal moisture to be removed. This resulted in poor structural uniformity of the obtained cathode material, which easily caused a high Li / Ni mixing ratio, thus affecting capacity and cycle performance.

[0070] The dehydroxylation initiation temperature of Comparative Example 3 was lower than that of Example 1, and the dehydroxylation rate of Comparative Example 3 was too slow, resulting in a rough surface of the precursor. The cathode material inherited the rough surface, resulting in poor coating stability. Although it had low lithium-nickel mixing, its electrochemical performance was still poor.

[0071] The preparation methods of the ternary precursors provided in the above embodiments will be described below.

[0072] Example 1 This embodiment also provides a method for preparing a ternary precursor, the steps of which are as follows: (1) Under an argon atmosphere, a metal salt solution, ammonia and sodium hydroxide solution were introduced into a reactor containing a bottom liquid for co-precipitation reaction. The temperature was maintained at 60℃, the flow rate of the metal salt solution was controlled at 60mL / min, the pH of the reaction system was controlled at 11.5, and the ammonia concentration of the reaction system was controlled at 9g / L. The feeding was stopped after the particle size D50 of the reactant material grew to 3.14μm. Seed crystals were obtained after solid-liquid separation. The concentration of metal ions in the metal salt solution is 2 mol / L, and the metal salt solution contains nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 8:0.8:1.2.

[0073] The ammonia solution has a mass fraction of 17%; the sodium hydroxide solution has a mass fraction of 35%; the bottom solution is a mixed solution with a pH of 11.5 and an ammonia concentration of 9 g / L, and its volume is 1 / 3 of the reactor volume.

[0074] (2) Add 6 kg of seed crystals obtained in step (1) to the reactor, and add 1 / 3 of the reactor volume (the reactor volume is 300 L, the same below) of glycine-sodium hydroxide buffer solution with pH 9 as the base liquid. Pass sodium hydroxide solution, ammonia water and metal salt solution through, control the feed rate of metal salt solution to 100 mL / min, the pH of the reaction system to 9, and the ammonia concentration to 5 g / L, until the reaction slurry particles grow to D50 of 5.84 μm, add quaternized polyethyleneimine, control the amount of quaternized polyethyleneimine added to be 3 wt% of the solid content of the system, and adjust the feed rate of metal salt solution to 60 mL / min. Increase the flow rate of sodium hydroxide solution to control the pH of the reaction system to 10.5 and the ammonia concentration to 5 g / L, until the reaction slurry particles grow to D50 of 9.95 μm, stop feeding, and age for 6 h.

[0075] The concentrations of sodium hydroxide solution, ammonia water, and metal salt solution are the same as in step (1).

[0076] Quaternized polyethyleneimine (quaternized PEI) has a molecular weight of 40 kDa and a degree of quaternization (silver nitrate titration) of 48%. The preparation method is as follows: ① Polyethyleneimine was dissolved in DMF, and a DMF solution of propylene oxide was added dropwise under an ice-water bath at 5°C. After the addition was complete, the mixture was stirred and reacted for 8 hours. The tertiary amination polyethyleneimine was obtained by vacuum distillation at 40°C. The molar ratio of nitrogen to propylene oxide in polyethyleneimine was 1:1. ② Tertiary amination polyethyleneimine was dissolved in anhydrous ethanol and refluxed at 50°C for 48 h. The mixture was precipitated with 10 times its volume of anhydrous diethyl ether. The solid was collected by filtration, washed with anhydrous diethyl ether, and dried to obtain quaternary amination polyethyleneimine. The molar ratio of nitrogen to iodomethane in tertiary amination polyethyleneimine was 1:0.5.

[0077] (3) The reaction material obtained in step (2) is filtered, washed and dried to obtain nickel cobalt manganese hydroxide precursor.

[0078] Example 2 The difference from Example 1 is that it includes: In step (1), the reaction temperature is 65℃ and the D50 is 3.28μm; In step (2), the mass fraction of ammonia water is 12%; the D50 when quaternized PEI is added is 5.68 μm; the flow rate of the molten metal after adding quaternized PEI is 70 mL / min; the endpoint D50 is 10.05 μm; and no aging is performed.

[0079] Step (3) is the same as in Example 1.

[0080] Example 3 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 3.59 μm. In step (2), the added base solution has a pH of 9 and an ammonia concentration of 6 g / L; the metal salt solution has a metal ion concentration of 2 mol / L and contains nickel sulfate, cobalt sulfate, manganese sulfate, and titanium oxysulfate in a molar ratio of 8:0.8:1.2. The amount of titanium oxysulfate added is based on a titanium doping amount of 2000 ppm in the final product; the ammonia concentration is maintained at 6 g / L; the metal liquid flow rate is 120 mL / min; the D50 when adding quaternized PEI is 5.59 μm; and the endpoint D50 is 10.04 μm.

[0081] Step (3) is the same as in Example 1.

[0082] Example 4 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 3.32 μm. In step (2), the D50 of the added quaternized PEI is 4.27 μm; the amount of quaternized polyethyleneimine added is controlled to be 5 wt% of the solid content of the system, and the feeding is stopped when the reaction slurry particles grow to D50 of 9.85 μm, and no aging is carried out.

[0083] The quaternized polyethyleneimine has a molecular weight of 60 kDa and a degree of quaternization (silver nitrate titration) of 55%. The preparation method is as follows: ① Polyethyleneimine was dissolved in DMF, and a DMF solution of propylene oxide was added dropwise under an ice-water bath at 5°C. After the addition was complete, the mixture was stirred and reacted for 8 hours. The mixture was then distilled under reduced pressure at 40°C to obtain tertiary amination polyethyleneimine. The molar ratio of nitrogen to propylene oxide in polyethyleneimine was 1:1. ② Tertiary amination polyethyleneimine and iodomethane were dissolved in anhydrous ethanol and refluxed at 50°C for 48 hours. The mixture was precipitated using 10 times its volume of anhydrous diethyl ether. The solid was collected by filtration, washed with anhydrous diethyl ether, and dried to obtain quaternary ammonium polyethyleneimine. The molar ratio of nitrogen to iodomethane in tertiary amination polyethyleneimine was 1:0.8.

[0084] (3) Same as in Example 1.

[0085] Example 5 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 3.17 μm. In step (2), the D50 of the added quaternized PEI is 4.85 μm; the added quaternized polyethyleneimine is controlled to be 2 wt% of the solid content of the system, and the feeding is stopped when the reaction slurry particles grow to a D50 of 10.05 μm.

[0086] The quaternized polyethyleneimine has a molecular weight of 20 kDa and a degree of quaternization (silver nitrate titration) of 40%. The preparation method is as follows: ① Polyethyleneimine was dissolved in DMF, and a DMF solution of propylene oxide was added dropwise under an ice-water bath at 5°C. After the addition was complete, the mixture was stirred and reacted for 8 hours. The mixture was then distilled under reduced pressure at 40°C to obtain tertiary amination polyethyleneimine. The molar ratio of nitrogen to propylene oxide in polyethyleneimine was 1:0.8. ② Tertiary amination polyethyleneimine and iodomethane were dissolved in anhydrous ethanol and refluxed at 50°C for 48 hours. The mixture was precipitated with 10 times its volume of anhydrous diethyl ether. The solid was collected by filtration, washed with anhydrous diethyl ether, and dried to obtain quaternary ammonium polyethyleneimine. The molar ratio of nitrogen to iodomethane in tertiary amination polyethyleneimine was 1:0.5.

[0087] Step (3) is the same as in Example 1.

[0088] Example 6 This embodiment also provides a method for preparing a ternary precursor, the steps of which are as follows: (1) Under an argon atmosphere, a metal salt solution, ammonia and sodium hydroxide solution were introduced into a reactor containing a bottom liquid for co-precipitation reaction. The temperature was maintained at 60℃, the flow rate of the metal salt solution was controlled at 70mL / min, the pH of the reaction system was controlled at 11, and the ammonia concentration of the reaction system was controlled at 8g / L. The feeding was stopped after the particle size D50 of the reactant material grew to 3.89μm. Seed crystals were obtained after solid-liquid separation. The concentration of metal ions in the metal salt solution is 2.5 mol / L, and the metal salt solution contains nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.92:0.06:0.02.

[0089] The ammonia solution has a mass fraction of 17%; the sodium hydroxide solution has a mass fraction of 35%; the bottom solution is a mixed solution with a pH of 11 and an ammonia concentration of 8 g / L, and its volume is 1 / 3 of the reactor volume.

[0090] (2) Add the seed crystals obtained in step (1) to the reactor, and add 1 / 3 of the reactor volume of glycine-sodium hydroxide buffer solution with pH 8.6 as the base liquid. Pass sodium hydroxide solution, ammonia water and metal salt solution through, control the feed rate of metal salt solution to 100 mL / min, the pH of the reaction system to 9, and the ammonia concentration to 5 g / L. When the reaction slurry particles grow to D50 of 5.92 μm, add quaternized polyethyleneimine, control the amount of quaternized polyethyleneimine added to 3 wt% of the solid content of the system, and adjust the feed rate of metal salt solution to 60 mL / min. Increase the flow rate of sodium hydroxide solution to control the pH of the reaction system to 10.5 and the ammonia concentration to 5 g / L. Stop feeding when the reaction slurry particles grow to D50 of 13.55 μm.

[0091] The concentrations of sodium hydroxide solution, ammonia water, and metal salt solution are the same as in step (1).

[0092] The molecular weight of the quaternized polyethyleneimine is 40 kDa, and the degree of quaternization (silver nitrate titration method) is 48%. The preparation method is the same as in Example 1.

[0093] (3) The reaction material obtained in step (2) is filtered, washed and dried to obtain nickel cobalt manganese hydroxide precursor.

[0094] Example 7 This embodiment also provides a method for preparing a ternary precursor, the steps of which are as follows: (1) Under an argon atmosphere, a metal salt solution, ammonia and sodium hydroxide solution were introduced into a reactor containing a bottom liquid for co-precipitation reaction. The temperature was maintained at 60℃, the flow rate of the metal salt solution was controlled at 50mL / min, the pH of the reaction system was controlled at 12, and the ammonia concentration of the reaction system was controlled at 10g / L. The feeding was stopped after the particle size D50 of the reactant material grew to 2.14μm. Seed crystals were obtained after solid-liquid separation. The concentration of metal ions in the metal salt solution is 1.5 mol / L, and the metal salt solution contains nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 6:2:2.

[0095] The ammonia solution has a mass fraction of 17%; the sodium hydroxide solution has a mass fraction of 35%; the bottom solution is a mixed solution with a pH of 12 and an ammonia concentration of 10 g / L, and its volume is 1 / 3 of the reactor volume.

[0096] (2) Add the seed crystals obtained in step (1) to the reactor, and add 1 / 3 of the reactor volume of glycine-sodium hydroxide buffer solution with pH 9.6 as the base liquid. Pass sodium hydroxide solution, ammonia water and metal salt solution through, control the feed rate of metal salt solution to 100 mL / min, the pH of the reaction system to 9, and the ammonia concentration to 5 g / L. When the reaction slurry particles grow to D50 of 2.89 μm, add quaternized polyethyleneimine, control the amount of quaternized polyethyleneimine added to 1 wt% of the solid content of the system, and adjust the feed rate of metal salt solution to 60 mL / min. Increase the flow rate of sodium hydroxide solution to control the pH of the reaction system to 10.5 and the ammonia concentration to 5 g / L. Stop feeding when the reaction slurry particles grow to D50 of 5.42 μm.

[0097] The concentrations of sodium hydroxide solution, ammonia water, and metal salt solution are the same as in step (1).

[0098] The molecular weight of the quaternized polyethyleneimine is 40 kDa, and the degree of quaternization (silver nitrate titration method) is 48%. The preparation method is the same as in Example 1.

[0099] (3) The reaction material obtained in step (2) is filtered, washed and dried to obtain nickel cobalt manganese hydroxide precursor.

[0100] Example 8 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 2.85 μm. In step (2), the metal salt solution contains nickel sulfate, cobalt sulfate, manganese sulfate and sodium metatungstate in a molar ratio of 8:0.8:1.2. The amount of sodium metatungstate added is based on the doping amount of tungsten in the final product being 2000 ppm. The D50 when quaternized PEI is added is 3.54 μm. The final D50 is 6.85 μm. No aging is performed.

[0101] Step (3) is the same as in Example 1.

[0102] Example 9 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 3.59 μm. In step (2), the metal salt solution contains nickel sulfate, cobalt sulfate, manganese sulfate, and titanium oxysulfate in a molar ratio of 8:0.8:1.2. The amount of titanium oxysulfate added is based on a titanium doping amount of 4000 ppm in the final product. The D50 of quaternized PEI is 6.02 μm. Quaternized polyethyleneimine is added, and the amount of quaternized polyethyleneimine added is controlled to be 1 wt% of the solid content of the system. Feeding is stopped when the reaction slurry particles grow to a D50 of 10.11 μm, and no aging is performed. The molecular weight of quaternized polyethyleneimine is 20 kDa, and the degree of quaternization (silver nitrate titration method) is 40%.

[0103] Step (3) is the same as in Example 1.

[0104] Example 10 The difference from Example 1 is that it includes: In step (1), the D50 of the seed crystal is 2.34 μm. In step (2), the metal salt solution contains nickel sulfate, cobalt sulfate, manganese sulfate and aluminum sulfate in a molar ratio of 8:0.8:1.2. The amount of aluminum sulfate added is based on the doping amount of aluminum element in the final product of 4000 ppm. The flow rate of the metal salt solution is 90 mL / min. The D50 when adding quaternized PEI is 3.22 μm. The flow rate of the metal salt solution is 50 mL / min. When the endpoint D50 is 5.04 μm, the feeding is stopped and no aging is performed.

[0105] Step (3) is the same as in Example 1.

[0106] Comparative Example 1 This comparative example also provides a method for preparing a ternary precursor, the steps of which are as follows: (1) Preparation of carbonate seed crystals: Under an argon atmosphere, metal salt solution, ammonia water and sodium carbonate solution are passed into a reaction vessel containing bottom liquid for co-precipitation reaction. The temperature is maintained at 85℃, the flow rate of metal salt solution is controlled at 60mL / min, the pH of the reaction system is controlled at 11, and the ammonia concentration of the reaction system is controlled at 8g / L. When the particle size D50 of the reactant material grows to 2.34μm, the feeding is stopped, and the seed crystals are obtained after solid-liquid separation. The concentration of metal ions in the metal salt solution is 2 mol / L, and the metal salt solution contains nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 8:0.8:1.2.

[0107] The ammonia solution has a mass fraction of 17%; the sodium carbonate solution has a concentration of 1.8 mol / L; the bottom solution is a mixed solution with a pH of 11 and an ammonia concentration of 8 g / L, and its volume is 1 / 3 of the reactor volume.

[0108] (2) Add the seed crystals obtained in step (1) to the reactor, and add 1 / 3 of the reactor volume of glycine-sodium hydroxide buffer solution with pH 8.6 as the base liquid. Then, introduce sodium hydroxide solution, ammonia water and metal salt solution. Control the feed rate of metal salt solution to 100 mL / min, the pH of the reaction system to 8.6, and the ammonia concentration to 5 g / L. When the reaction slurry particles grow to D50 of 3.84 μm, adjust the feed rate of metal salt solution to 60 mL / min, increase the flow rate of sodium hydroxide solution to control the pH of the reaction system to 10.5, and the ammonia concentration to 5 g / L. Stop feeding when the reaction slurry particles grow to D50 of 6.22 μm, and age for 6 h.

[0109] The metal salt solution contains nickel sulfate, cobalt sulfate, manganese sulfate, and sodium metatungstate in a molar ratio of 8:0.8:1.2. The amount of sodium metatungstate added is based on a tungsten doping level of 2000 ppm in the final product. The ammonia solution has a mass fraction of 17%, and the sodium hydroxide solution has a mass fraction of 35%.

[0110] (3) The reaction material obtained in step (2) is filtered, washed and dried to obtain nickel cobalt manganese hydroxide precursor.

[0111] Comparative Example 2 The difference from Example 1 is that it includes: In step (1), the temperature is maintained at 50℃ and the D50 of the seed crystal is 3.85μm; In step (2), the added base solution has a pH of 9 and an ammonia concentration of 4 g / L. The metal salt solution contains nickel sulfate, cobalt sulfate, manganese sulfate, and sodium metatungstate in a molar ratio of 8:0.8:1.2. The amount of sodium metatungstate added is based on a tungsten doping amount of 2000 ppm in the final product. Quaternized PEI is not added. When D50 reaches 5.21 μm, the flow rate and pH of the metal salt solution are adjusted. The final D50 is 10.24 μm, and no aging is performed.

[0112] Step (3) is the same as in Example 1.

[0113] Comparative Example 3 This comparative example also provides a method for preparing a ternary precursor, the steps of which are as follows: A solution with pH 9 and ammonia concentration of 4 g / L was added to one-third of the reactor volume as a base solution. Sodium hydroxide solution, ammonia water, and a metal salt solution were then introduced, maintaining the reaction temperature at 70℃. The feed rate of the metal salt solution was controlled at 100 mL / min, the pH of the reaction system was 9.6, and the ammonia concentration was 8 g / L. Feeding was stopped when the reaction slurry particles grew to a D50 of 10.12 μm, and the mixture was aged for 6 hours. The concentration of metal ions in the metal salt solution was 2 mol / L, and the solution contained nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 8:0.8:1.2. The ammonia water mass fraction was 17%, and the sodium hydroxide solution mass fraction was 35%. The resulting reaction mixture was filtered, washed, and dried to obtain a nickel-cobalt-manganese hydroxide precursor.

[0114] 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 precursor, characterized in that, The ternary precursor is nickel-cobalt-manganese hydroxide, and the dehydroxylation initiation temperature of the ternary precursor is above 150℃, and the dehydroxylation rate v is 0.5~2.0 g / (g·℃). The test procedure for the dehydroxylation rate is as follows: The ternary precursor and acetylene black are mixed at a mass ratio of 1:0.25 and then subjected to thermogravimetric analysis. The test conditions are a nitrogen atmosphere, a temperature range of 25℃~1000℃, and a heating rate of 2° / min. Dehydroxylation rate v = W / T × 1000; In the formula, W represents the weight loss ratio corresponding to the maximum weight loss peak of the differential thermogravimetric curve below 400℃, with the unit being g / g; T represents the temperature range corresponding to the onset and termination temperatures of the maximum weight loss peak below 400℃ in the thermogravimetric curve obtained from the thermogravimetric test, with the unit being ℃.

2. The ternary precursor according to claim 1, characterized in that, The reduction initiation temperature of the ternary precursor is 600℃~950℃. The reduction initiation temperature is determined by the tangent method for the maximum weight loss peak above 600℃ on the differential thermogravimetric curve. And / or, the temperature range T is 60℃~200℃; And / or, the weight loss ratio W ranges from 0.09 g / g to 0.19 g / g; And / or, the particle size D50 of the ternary precursor is 5 μm to 15 μm; And / or, the dehydroxylation rate v / D50 = (0.05~0.35) / (℃·μm); And / or, the acetylene black used conforms to GB / T 3782-2016; And / or, the chemical formula of the ternary precursor is Ni x Co y Mn z M 1-x-y-z (OH) 2+e M is selected from one or more of Al, Ti, Ca, Sr, Ba, Zr, Y, La, Ce, Sm, Er, Mg, Nb, Ta, Mo, W and Zn; 1 / 3≤x<1, 0<y<1, 0<z<1, 0≤e≤0.06, 0≤1-xyz≤0.

2.

3. A method for preparing the ternary precursor according to any one of claims 1 to 2, characterized in that, include: Synthetic seed crystals: Nickel-cobalt-manganese hydroxide seed crystals with a particle size D50 of 2 μm to 4 μm were prepared by co-precipitation method; Preparation of precursor: The nickel-cobalt-manganese hydroxide seed crystals were used to continue the co-precipitation reaction until the particle size D50 of the intermediate particles was 2.5 μm to 6.1 μm; Quaternized polyethyleneimine was added to continue the growth to obtain precursor particles with a particle size D50 of 5 μm to 15 μm.

4. The preparation method according to claim 3, characterized in that, The process of synthesizing seed crystals includes: preparing a base liquid in a reactor, introducing a nickel-cobalt-manganese mixed metal salt solution, a complexing agent solution, and a precipitant solution into the reactor for a co-precipitation reaction, stopping the feeding after the material particle size D50 grows to 2μm~4μm, and separating to obtain seed crystals; wherein, the complexing agent solution is an ammonia solution.

5. The preparation method according to claim 4, characterized in that, The process of synthesizing seed crystals has at least one of the following characteristics 1-6: Feature 1: The pH value of the base liquid is 11~12, and the pH value of the reaction system is controlled at 11~12 during the reaction process; Feature 2: The precipitant solution is an aqueous solution of sodium hydroxide; Feature 3: The ammonia concentration in the base solution is controlled to be 8 g / L to 10 g / L, and the ammonia concentration in the reaction system is controlled to be 8 g / L to 10 g / L during the reaction process; Feature 4: The total concentration of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is 1.5M~2.5M, and the feed rate of the nickel-cobalt-manganese mixed metal salt solution is 50mL / min~70mL / min; Feature 5: The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed metal salt solution is (0.5~0.95):(0.02~0.3):(0.02~0.3). Feature 6: The reaction is carried out under an inert atmosphere at a temperature of 55℃-70℃.

6. The preparation method according to claim 4, characterized in that, The process for preparing the intermediate particles includes: adding the seed crystals to a reaction vessel and mixing them with a glycine-sodium hydroxide buffer solution; introducing the nickel-cobalt-manganese mixed metal salt solution, the complexing agent solution, and the precipitant solution to react; controlling the reaction pH to be 8-9 and the ammonia concentration to be 4 g / L-6 g / L; the pH of the glycine-sodium hydroxide buffer solution is 8.6-9.

6. And / or, during the preparation of the intermediate particles, the feed rate of the nickel-cobalt-manganese mixed metal salt solution is 90 mL / min to 120 mL / min.

7. The preparation method according to claim 4, characterized in that, After adding the quaternized polyethyleneimine, the feed rate of the nickel-cobalt-manganese mixed metal salt solution is adjusted to 50 mL / min to 70 mL / min, the reaction pH is 10 to 11, and the ammonia concentration is 4 g / L to 6 g / L. And / or, when the particle size D50 in the reaction slurry reaches 5μm~15μm, it is aged, then the solid and liquid are separated, and the obtained solid material is washed and dried; And / or, the amount of the quaternized polyethyleneimine added is 1wt% to 5wt% of the solid content of the system; And / or, the number average molecular weight of the added quaternized polyethyleneimine is 20 kDa to 60 kDa; And / or, the degree of quaternization of the quaternized polyethyleneimine is 40% to 55%.

8. The preparation method according to claim 3, characterized in that, The preparation process of the quaternized polyethyleneimine includes: adding propylene oxide solution dropwise to polyethyleneimine solution under reaction conditions of 5℃~10℃, reacting for 5h-12h, and then distilling under reduced pressure to obtain tertiary amination polyethyleneimine; mixing and dissolving the tertiary amination polyethyleneimine with a halogenated product, and then carrying out a quaternization reaction at 40℃~60℃ for 40h-60h, followed by purification and drying to obtain quaternized polyethyleneimine; The halogenated product is selected from at least one of iodomethane and benzyl chloride; The molar ratio of nitrogen to propylene oxide in polyethyleneimine is 1:(0.8-1.1); the molar ratio of nitrogen to iodomethane in tertiary amination polyethyleneimine is 1:(0.4-0.8).

9. A ternary cathode material, characterized in that, The ternary precursor is prepared by any one of the ternary precursors described in claims 1-2 or by any one of the preparation methods described in claims 3-8.

10. A lithium-ion battery, characterized in that, Including the ternary cathode material as described in claim 9.

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