Method for producing nickel-rich hydroxide precursor material and method for producing nickel-rich oxide cathode material

Abstract

To provide a method for producing a nickel-rich hydroxide precursor material having a homogeneous structure with an element concentration gradient distribution, using a continuous Taylor vortex flow reactor.SOLUTION: The method for producing a nickel-rich hydroxide precursor material according to the present invention comprises (1) a step of preparing an aqueous solution A in which metal ion raw materials are dissolved, preparing an aqueous solution B in which a manganese source is dissolved, preparing an aqueous solution C in which a precipitating agent is dissolved, preparing an aqueous solution D in which a chelating agent is dissolved, and pouring the aqueous solution A, the aqueous solution C, and the aqueous solution D into a continuous Taylor vortex flow reactor to perform a first coprecipitation reaction, (2) a step of pouring the aqueous solution B into the continuous Taylor vortex flow reactor to perform a second coprecipitation reaction, and (3) a step of washing precipitates that have undergone the second coprecipitation reaction, placing the precipitates in an oven for drying, and obtaining the nickel-rich hydroxide precursor material.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention provides a method for manufacturing a nickel-rich hydroxide precursor material and a nickel-rich oxide cathode material. In particular, the present invention relates to a method for manufacturing a nickel-rich hydroxide precursor material and a nickel-rich oxide cathode material having an elemental concentration gradient distribution, which are manufactured by performing a coprecipitation reaction using a continuous Taylor vortex reactor and mixing by a ball mill.

Background Art

[0002] As consumers' energy demands for, for example, hybrid vehicles, smart grids, power plants, etc. are rapidly increasing, lithium-ion batteries (LIBs) are being widely studied as a promising energy storage technology, and more specifically, as one of the optimal energy storage technologies for solving energy problems. Lithium-ion batteries are optimal batteries for many consumer electronic devices, but the oxide cathodes applicable thereto have problems such as poor mechanical properties of the materials and the requirements for high discharge capacity and long cycle life. Therefore, research on next-generation oxide cathode materials is continuously being conducted. The research mainly focuses on improving the mechanical strength of the materials, the cycle life, discharge capacity, and safety of the battery during the charge-discharge process of the lithium-ion battery.

[0003] Nickel-rich layered oxide cathodes having a theoretical discharge capacity reaching 275 mAh / g and a high operating voltage of 2.8 to 4.3 V are expected as promising cathode materials for meeting the demands arising from the development of technology. Compared with the currently widely used lithium cobalt oxide cathode material (LiCoO2), such nickel-rich oxide cathodes have attracted attention because they are less toxic and less costly. However, if the nickel concentration is too high, it may accelerate the deterioration of the discharge capacity of the battery, and in particular, structural and chemical instabilities may occur at high temperatures and high operating voltages, posing a significant risk to safety. When the nickel-rich oxide cathode is charged to a high voltage, unstable Ni appears on its surface. 4+Ions are generated, forming an NiO-containing impurity phase and releasing an oxygen-containing substance. These highly active Ni 4+ ions may accelerate the decomposition of the electrolyte, thus consuming the electrolyte completely and potentially degrading the cycle performance of the battery. Additionally, the electrochemically inert NiO-containing impurity phase increases the diffusion resistance of lithium ions and reduces the charge and discharge rate. At the same time, the reaction between O2 released from the oxide and the organic electrolyte causes the problem of thermal runaway of the battery.

[0004] Cation mixing refers to the process in which Li + ions (ionic radius is approximately 0.76 Å) and Ni 2+ ions (ionic radius is approximately 0.69 Å) exchange their positions in their respective layers, which is the main cause of the degradation of the discharge capacity and the occurrence of phase transition in the structure of nickel-rich oxide cathodes. Such ion exchange is achieved through similar ionic radii. Also, side reactions generated by the contact of nickel-rich oxides with air or moisture may produce unwanted residues (e.g., LiOH and Li2CO3) on the surface. These residues can cause an insulating surface layer through interaction with the electrolyte, resulting in overvoltage phenomena during the charging of lithium-ion batteries. Due to the above reasons, it is still difficult to apply conventional nickel-rich oxides to commercial batteries such as electric vehicles and smart grids.

[0005] Methods for improving the structural stability of nickel-rich oxide cathodes and the long-term cycle life of batteries include component modification, adjustment of manufacturing conditions, and surface modification, etc. In particular, in a structure with a concentration gradient, also called a core-shell structure, electrochemically active transition metals (TM) are mainly restricted to the core part of the active material particles, and inactive transition metals are used as the shell, so the structural stability of nickel-rich oxide cathodes and the cycle performance of lithium-ion batteries are improved. In the prior art, as the outer layer, Li[Ni 0.8 Co 0.2 x [Ni 0.2 Mn 0.8 ​​1-x It has been proven that by using an oxide where (1 > x > 0.5), side reactions on the surface can be minimized. In such a material, the manganese element has an average oxidation number of +4, so even under high voltages, it has excellent structural stability and can maintain its hexagonal shape during the cycling process.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, there are still no related inventions regarding nickel-rich oxide cathode materials that have long-term cycle stability and can effectively suppress the occurrence of side reactions.

Means for Solving the Problems

[0008] Therefore, the present invention provides a method for manufacturing a nickel-rich hydroxide precursor material, and further provides a method for manufacturing a quaternary oxide cathode material having an element concentration gradient distribution synthesized from the nickel-rich hydroxide precursor material. In the present invention, the definition of nickel-rich is that the molar ratio of nickel content exceeds 50% of the whole compound. The nickel-rich hydroxide precursor material of the present invention is nickel cobalt manganese hydroxide having a homogeneous structure. That is, different from the prior art that synthesizes materials with different compositions of core and shell, such as a core-shell structure where the core is a binary material and the shell is a ternary material, the nickel-rich hydroxide precursor material of the present invention has the same elemental composition in its inner layer and outer layer, and each layer has nickel, cobalt, and manganese, and the difference is only the concentration ratio in each layer.

[0009] The nickel-rich hydroxide precursor produced by the manufacturing method of the present invention has a homogeneous element distribution structure having a nickel-rich inner layer and a manganese-rich outer layer, which can reduce the interfacial resistance when lithium ions move, increase its movement path, and thus improve the electrochemical performance and cycle stability of the manufactured electrode. In addition, the nickel-rich oxide cathode material produced by the manufacturing method of the present invention also has a homogeneous structure with an element concentration gradient distribution, and has aluminum element as an element to stabilize the structure, so it can improve the electrochemical performance such as the charge and discharge rate of the lithium-ion battery and the mechanical strength of the cathode material.

[0010] The method for manufacturing a nickel-rich hydroxide precursor material according to the present invention includes a step of pouring an aqueous solution A containing nickel ions and cobalt ions, a precipitant (aqueous solution C), and a chelating agent (aqueous solution D) into a continuous Taylor vortex reactor (TFR) to perform a first coprecipitation reaction, a step of further adding an aqueous solution B containing manganese ions to perform a second coprecipitation reaction, and a step of washing and drying the precipitate to obtain a nickel cobalt manganese hydroxide precursor.

[0011] The manufacturing method of the nickel-rich oxide cathode material according to the present invention includes a step of mixing an ethanol solution containing aluminum ions and the nickel cobalt manganese hydroxide precursor and then drying them, a step of pulverizing and mixing the dried mixture and a lithium source with a ball mill, and a step of performing a three-stage calcination heat treatment to obtain a lithium nickel cobalt manganese aluminum oxide cathode material.

[0012] Specifically, the present invention provides a manufacturing method of a nickel-rich hydroxide precursor material, which is a nickel cobalt manganese hydroxide having a homogeneous structure with an element concentration gradient distribution. The manufacturing method of the nickel-rich hydroxide precursor material includes: (1) Preparing an aqueous solution A in which a metal ion raw material is dissolved, Preparing an aqueous solution B in which a manganese source is dissolved, Preparing an aqueous solution C in which a precipitant is dissolved, Preparing an aqueous solution D in which a chelating agent is dissolved, A step of pouring the aqueous solution A, the aqueous solution C, and the aqueous solution D into a continuous Taylor vortex reactor and performing a first coprecipitation reaction for 2 to 7 hours, The metal ion raw material is a nickel source and a cobalt source, The nickel source is at least one selected from the group consisting of nickel sulfate, nickel oxalate, nickel acetate, nickel nitrate, nickel chloride, and nickel hydroxide, The cobalt source is at least one selected from the group consisting of cobalt sulfate, cobalt oxalate, cobalt carbonate, cobalt acetate, cobalt nitrate, cobalt chloride, and cobalt hydroxide, The manganese source is at least one selected from the group consisting of manganese sulfate, manganese oxalate, manganese carbonate, manganese citrate, manganese acetate, manganese nitrate, manganese phosphate, electrolytic manganese dioxide, and manganese oxide, (2) A step of pouring the aqueous solution B into the continuous Taylor vortex reactor and performing a second coprecipitation reaction for 5 to 70 hours, The reaction temperature of the second coprecipitation reaction is 30°C to 80°C, the pH value of the reaction environment is 9.5 to 12.5, and the rotation speed of the inner cylinder of the continuous Taylor vortex reactor is 200 rpm to 1500 rpm; (3) washing the precipitate obtained through the second coprecipitation reaction, putting it into an oven and drying it to obtain the nickel-rich hydroxide precursor material.

[0013] Furthermore, the concentration of the aqueous solution A is 1.6M to 1.92M.

[0014] Furthermore, the concentration of the aqueous solution B is 0.08M to 0.4M.

[0015] Furthermore, the concentration of the aqueous solution C is 2.0M to 6.0M, and the weight molar concentration ratio of the aqueous solution A to the aqueous solution C is 1:1 to 1:5.

[0016] Furthermore, the concentration of the aqueous solution D is 2.5M to 9.0M, and the weight molar concentration ratio of the aqueous solution A to the aqueous solution D is 1:1 to 1:5.

[0017] Furthermore, the drying temperature of the oven is 60°C to 120°C, and the drying time is 6 to 24 hours.

[0018] Furthermore, the supply rates of the aqueous solution A and the aqueous solution B are 1.0 to 3.0 ml / min.

[0019] The present invention further provides a method for manufacturing a nickel-rich oxide cathode material using the method for manufacturing the nickel-rich hydroxide precursor material. The nickel-rich oxide cathode material has a homogeneous structure with an elemental concentration gradient distribution, and the method for manufacturing the nickel-rich oxide cathode material includes: (a) dispersing an aluminum source in ethanol, adding the nickel-rich hydroxide precursor material and mixing them to obtain a mixture, and heating the mixture to complete drying at a temperature of 80°C to obtain a mixture a; The aluminum source is at least one selected from the group consisting of aluminum hydroxide, aluminum oxalate, aluminum carbonate, aluminum sulfate, aluminum acetate, aluminum nitrate, and aluminum phosphate; (b) A step of pulverizing and mixing the lithium source and the mixture a in the step (a) at a molar ratio of 1:1.01 to 1:1.25 to obtain a mixture b; The lithium source is at least one selected from the group consisting of lithium hydroxide, lithium nitrate, lithium acetate, lithium chloride, lithium hydrogen phosphate, lithium phosphate, and lithium carbonate; (c) A step of performing a three-stage calcination heat treatment on the mixture b in the step (b) to obtain the nickel-rich oxide cathode material.

[0020] Furthermore, the conditions for the pulverization are that the rotation speed of the ball mill is 50 to 200 rpm and the pulverization time is 2 to 10 hours.

[0021] Furthermore, the temperature and time of the three-stage calcination heat treatment are respectively: the temperature of the first stage is 100°C to 200°C and the time is 1 to 3 hours; the temperature of the second stage is 500°C to 600°C and the time is 4 to 8 hours; the temperature of the third stage is 700°C to 800°C and the time is 10 to 40 hours. The heating rate of the three-stage calcination heat treatment is 0.1 to 20°C / min in all cases.

Advantages of the Invention

[0022] The nickel-rich oxide cathode material having a homogeneous structure with an element concentration gradient distribution produced by the method of the present invention has a nickel-rich inner layer, a manganese-rich outer layer, and an aluminum-containing surface layer with an element concentration gradient distribution. This particle structure contributes to the mechanical stability of the cathode material at high charge and discharge rates and can effectively suppress the occurrence of side reactions between the cathode material and the electrolyte.

[0023] Therefore, compared with an oxide cathode material having a normal uniform concentration, a lithium-ion battery composed of a nickel-rich oxide cathode material produced using a continuous Taylor vortex reactor has better electrochemical performance, such as a high charge-discharge rate and a high discharge capacity retention rate during long-term charge-discharge cycles.

[0024] In addition, the nickel-rich hydroxide precursor produced by performing a coprecipitation reaction using the continuous Taylor vortex reactor in the method of the present invention has uniform and aggregated particles and a large particle size. Furthermore, since it has primary particles in a needle-like form, the regularly arranged secondary particles composed of it have a structure capable of bearing the tensile and compressive stresses generated by long-term charge and discharge, can prevent the occurrence of microcracks, and can improve the manufacturing efficiency in large-scale production.

[0025] From the above, the present invention provides a method for producing a nickel-rich hydroxide precursor and a nickel-rich oxide cathode material having a homogeneous structure with an elemental concentration gradient distribution. These production methods can be suitably applied to large-scale production. Since the nickel-rich hydroxide precursor has a uniform and stress-resistant structure and the nickel-rich oxide cathode material has excellent charge-discharge efficiency and long-term cycle stability, the electrochemical performance of the lithium-ion battery can be significantly improved.

Brief Description of the Drawings

[0026]

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Mode for Carrying Out the Invention

[0027] The manufacturing method of the nickel-rich hydroxide precursor material and the nickel-rich oxide cathode material according to the present invention will be described below by way of exemplary embodiments. It should be noted that the following exemplary embodiments are merely for explaining the present invention and do not limit the scope of the present invention.

[0028] [Method for Producing Nickel-Rich Hydroxide Precursor Material] First, a nickel-rich hydroxide precursor having an element concentration gradient is synthesized by a coprecipitation reaction using a continuous Taylor vortex reactor (TFR, 1 L, Laminar, Korea). A schematic diagram thereof is shown in FIG. 1.

[0029] As shown in FIG. 2(a), the method for producing a nickel-rich hydroxide precursor according to the present invention includes the following steps. S11: A metal ion raw material is uniformly mixed with deionized water to prepare a metal ion mixed solution (aqueous solution A); S12: A manganese source is dissolved in deionized water to prepare an aqueous solution B; S13: Aqueous solution A, a precipitant aqueous solution (aqueous solution C), and a chelating agent aqueous solution (aqueous solution D) are poured into a continuous Taylor vortex reactor filled with deionized water to perform a first coprecipitation reaction; S14: Aqueous solution B is poured into the continuous Taylor vortex reactor to perform a second coprecipitation reaction; S15: The precipitate of the second coprecipitation reaction is collected, washed with ethanol and deionized water to remove residual ions, and then placed in an oven and dried to obtain a nickel-rich hydroxide precursor.

[0030] Specifically, the preparation method of each solution is as follows.

[0031] Preparation of a mixed metal ion solution (aqueous solution A): A metal ion raw material is uniformly dissolved and mixed in deionized water to prepare a mixed metal ion solution (aqueous solution A). In one embodiment, the metal ion raw material is a nickel source and a cobalt source. In one embodiment, the nickel source as the metal ion raw material is at least one selected from the group consisting of nickel sulfate, nickel oxalate, nickel acetate, nickel nitrate, nickel chloride, and nickel hydroxide. The cobalt source as the metal ion raw material is at least one selected from the group consisting of cobalt sulfate, cobalt oxalate, cobalt carbonate, cobalt acetate, cobalt nitrate, cobalt chloride, and cobalt hydroxide. In one embodiment, the concentration of aqueous solution A is 1.6 M to 1.92 M, preferably 1.7 M to 1.92 M, more preferably 1.8 M to 1.92 M, and even more preferably 1.92 M.

[0032] Preparation of aqueous solution B: A manganese source is dissolved in deionized water to prepare aqueous solution B. In one embodiment, the manganese source is at least one selected from the group consisting of manganese sulfate, manganese oxalate, manganese carbonate, manganese citrate, manganese acetate, manganese nitrate, manganese phosphate, electrolytic manganese dioxide, and manganese oxide (e.g., α-MnO2, β-MnO2, γ-MnO2, Mn2O3, Mn3O4). In one embodiment, the concentration of aqueous solution B is 0.08 M to 0.4 M, preferably 0.08 M to 0.2 M, more preferably 0.08 M to 0.1 M, and even more preferably 0.08 M.

[0033] Preparation of a precipitant aqueous solution (aqueous solution C): A precipitant is uniformly dissolved and mixed in deionized water to prepare a precipitant aqueous solution for the subsequent coprecipitation reaction. In one embodiment, the precipitant is sodium hydroxide. In one embodiment, the concentration of aqueous solution C is 2.0 M to 6.0 M, preferably 2.5 M to 5.0 M, more preferably 3.0 M to 4.5 M, and even more preferably 4 M. In one embodiment, the weight molar concentration ratio of aqueous solution A to aqueous solution C is 1:1 to 1:5, preferably 1:1 to 1:4, more preferably 1:1 to 1:3, and even more preferably 1:2.

[0034] Preparation of Chelating Agent Aqueous Solution (Aqueous Solution D): The chelating agent is uniformly dissolved and mixed in deionized water to prepare the chelating agent aqueous solution for the subsequent coprecipitation reaction. In one embodiment, the chelating agent is aqueous ammonia. In one embodiment, the concentration of aqueous solution D is 2.5M to 9.0M, preferably 4.0M to 9.0M, more preferably 6.0M to 8.0M, and even more preferably 7.2M. In one embodiment, the weight molar concentration ratio of aqueous solution A to aqueous solution D is 1:1 to 1:5, preferably 1:1 to 1:4, more preferably 1:1 to 1:3, and even more preferably 1:3.

[0035] In one embodiment, before performing the coprecipitation reaction, all of the above aqueous solutions are pre-filtered to remove unnecessary impurities.

[0036] A schematic diagram of manufacturing a nickel-rich hydroxide precursor using a TFR is shown in FIG. 1. When the inner cylinder of the TFR rotates, aqueous solutions A, C, and D are poured into the front inlet end of the cylindrical chamber of the TFR filled with deionized water. After undergoing the first coprecipitation reaction, aqueous solution B is further poured into the upper inlet end of the TFR, and a second coprecipitation reaction is carried out with the mixed solution of aqueous solutions A, C, and D by the cylindrical chamber of the TFR. In one embodiment, the time of the first coprecipitation reaction is 2 to 7 hours, preferably 3 to 6 hours, and more preferably 5 hours. In one embodiment, the time of the second coprecipitation reaction is 5 to 70 hours, preferably 15 to 55 hours, and more preferably 20 to 30 hours. In one embodiment, the temperature of the second coprecipitation reaction can be 30°C to 80°C, preferably 45°C to 70°C, and more preferably 60°C. Among them, the coprecipitation reaction at 60°C is the most complete, generating spherical secondary particles composed of needle-like primary particles, and can achieve a suitable regular arrangement and density. The environmental pH value can be 9.5 to 12.5, preferably 10.0 to 12.0, and more preferably 11.2. By controlling the flow rate of aqueous solution C, the reaction can occur stably. Among them, the coprecipitation reaction at pH 11.2 reaches a steady state and can achieve an optimal particle size distribution. In one embodiment, the rotation speed of the inner cylinder of the TFR can be 200 rpm to 1500 rpm, preferably 400 rpm to 1000 rpm, more preferably 500 rpm to 800 rpm, and still more preferably 600 rpm. Among them, setting the rotation speed of the inner cylinder of the TFR to 600 rpm contributes the most to generating secondary particles with a particle size of about 8 to 12 μm, and is most preferred for the polycrystalline cathode material. The supply rates of aqueous solution A and aqueous solution B are 1.0 ml / min to 3.0 ml / min, preferably 1.5 ml / min to 2.0 ml / min, and more preferably 1.703 ml / min. Thereby, continuous production is carried out.

[0037] Here, what needs to be further explained is that the present invention is to manufacture a hydroxide precursor using a TFR. Compared with the batch reactor used in the conventional continuous stirred tank reactor (CSTR), manufacturing with a TFR has the following characteristics and advantages.

[0038] Controllability and uniformity: By controlling the rotation speed of the inner cylinder of the reactor, the TFR can achieve various fluid flow patterns. In this embodiment, it is a fluid mixing form called Taylor flow, belonging to micro-scale mixing, and it is possible to make the environment where the coprecipitation reaction occurs more favorable for the production of a more uniform nickel-rich hydroxide precursor. In contrast, conventional batch reactors perform mixing by a flow pattern called turbulent flow, belonging to macro mixing, so there is a possibility of causing differences and changes in the particle size and material components, which particularly affects the material uniformity and production efficiency in large-scale production applications.

[0039] Scalability: Generally, the production of nickel-rich hydroxide precursors can be scaled up from the laboratory level to the industrial production scale, that is, the required reactor capacity is 1L to 1000L. Since the TFR has the characteristics of continuous operation and scalability, it can guarantee the consistency of quality in mass production. On the other hand, conventional batch reactors are suitable for applications in small-scale research and development, and it is difficult to maintain the consistency of the same reaction conditions and product quality in mass production.

[0040] Reaction time and production efficiency: In the production process of nickel-rich hydroxide precursors, characteristics such as continuous production and micro-scale mixing of the TFR can effectively shorten the material production time, and thus improve the production efficiency. On the other hand, the mixing by conventional batch reactors belongs to macro mixing and requires a longer reaction time, so it is less efficient in continuous production and large-scale production processes.

[0041] It is further necessary to explain that the conditions of reaction parameters such as the reaction environment temperature, pH value, inner cylinder rotation speed, supply rates of aqueous solution A and aqueous solution B, etc. in the TFR have a great influence on the characteristics of the produced nickel-rich hydroxide precursor, so the setting and control of the above conditions are extremely important. (1) Reaction temperature: The temperature in the reaction environment significantly affects the shape of nickel-rich hydroxide precursor particles. If the temperature is too low, the formation of particles will be incomplete, and if the temperature is too high, the shape of the formed primary particles may be different from what is expected. (2) Inner cylinder rotation speed: The inner cylinder rotation speed of the TFR can directly affect the particle size of the precursor. Increasing the rotation speed will generate smaller vortices, resulting in the formation of particle cores with small particle sizes, thereby producing a large number of small-sized particles. If the particle size is too small (particle size < about 1 - 3 μm), it will cause a larger surface area and a higher solid electrolyte interface (SEI) resistance, which is likely to have an adverse effect on the electrochemical performance of the positive electrode in the subsequent production of the positive electrode material. On the other hand, particles with too large a size (particle size > about 20 - 30 μm) have a longer lithium ion migration path, resulting in a decrease in the diffusion rate of lithium ions and a reduction in the overall electrochemical performance of the positive electrode material. To endow the positive electrode material with optimal electrochemical performance, the particle size of the material produced by the method of the present invention is preferably 8 - 12 μm. (3) Supply rates of aqueous solution A and aqueous solution B and pH value: If the supply rate is too fast or the pH value is too high, a large number of hydroxide particle cores will be generated, resulting in incomplete particle molding or a less compact structure. Such particles are likely to disintegrate and powderize during the subsequent manufacturing process. On the other hand, if the supply rate is too slow, the residence time of the particles in the reaction chamber will be longer, reducing the manufacturing efficiency. Also, if the pH value is too low, it will directly affect the shape of the particles.

[0042] Thereby, control is performed so that the above conditions are satisfied, and the mixed solution in the cylindrical chamber of the TFR is sufficiently reacted. Next, the precipitate of the coprecipitation reaction is collected at the outlet end of the cylindrical chamber, and the remaining Na + , SO4 2- and other ions are washed and removed, and then placed in an oven to be dried. In one embodiment, the temperature of the oven can be 60°C to 120°C, preferably 60°C to 100°C, more preferably 60°C to 80°C, and even more preferably 60°C. The drying time can be 6 to 24 hours, preferably 8 to 20 hours, more preferably 10 to 15 hours, and even more preferably 12 hours. After the drying treatment, a nickel-rich hydroxide precursor Ni x Co y Mn 1-x-y (OH)2 is obtained.

[0043] [Method for manufacturing nickel-rich oxide cathode material] As shown in FIG. 2(b), the method for manufacturing the nickel-rich oxide according to the present invention is as follows. S21: Disperse the aluminum source in ethanol, add the nickel-rich hydroxide precursor and mix to obtain a mixture, and heat the mixture until it is completely dried to obtain mixture a; S22: Use a ball mill to grind and mix the lithium source and mixture a in S21 with grinding balls to obtain mixture b; S23: Perform three-stage calcination heat treatment on mixture b in S22 in a high-temperature furnace.

[0044] Disperse an appropriate amount of the aluminum source in ethanol, add the powder of the manufactured nickel-rich hydroxide precursor and mix well, and heat at a constant temperature until it is completely dried to obtain mixture a. In one embodiment, the aluminum source is Al(OH)3. In one embodiment, the constant temperature is 70°C to 90°C, and 80°C is preferred.

[0045] Next, a lithium source is added to the mixture a. In one embodiment, the lithium source is the lithium salt LiOH·H2O. In one embodiment, the molar ratio of the mixture a to the lithium source is from 1:1.01 to 1:1.25, preferably from 1:1.01 to 1:1.20, more preferably from 1:1.01 to 1:1.10, and even more preferably 1:1.05.

[0046] Next, pulverization and mixing are carried out using a ball mill with PU balls or agate balls to obtain a mixture b. The rotation speed of the ball mill is from 50 rpm to 200 rpm, preferably from 70 rpm to 150 rpm, more preferably from 80 rpm to 125 rpm, and even more preferably 100 rpm. The pulverization time is from 2 to 10 hours, preferably from 3 to 8 hours, more preferably from 4 to 6 hours, and even more preferably 5 hours. The ratio of the PU balls or agate balls to the sample obtained by mixing the mixture and the lithium source is from 1:1 to 1:20, preferably from 1:1 to 1:10, more preferably from 1:1 to 1:5, and even more preferably 1:1.

[0047] Next, the mixture b is subjected to three-stage calcination heat treatment in a high-temperature furnace in an air or pure oxygen atmosphere, and a pure oxygen atmosphere is preferred. The temperature of the first stage in the three-stage calcination heat treatment is from 100°C to 200°C, preferably from 120°C to 180°C, more preferably from 140°C to 160°C, and even more preferably 150°C. The time is from 1 to 3 hours, preferably from 1.5 to 2.5 hours, and more preferably 2 hours. The temperature of the second stage is from 500°C to 600°C, preferably from 520°C to 580°C, more preferably from 540°C to 560°C, and even more preferably 550°C. The time is from 4 to 8 hours, preferably from 5 to 7 hours, and more preferably 6 hours. The temperature of the third stage is from 700°C to 800°C, preferably from 710°C to 775°C, more preferably from 720°C to 750°C, and even more preferably 730°C. The time is from 10 to 40 hours, preferably from 15 to 30 hours, and more preferably 20 hours. The heating rate of this three-stage calcination heat treatment is all from 0.1 to 20°C / min, preferably from 0.5 to 10°C / min, more preferably from 1 to 5°C / min, and even more preferably 2°C / min.

[0048] As a result, a nickel-rich oxide cathode material having a homogeneous structure with an elemental concentration gradient distribution can be obtained.

[0049] The nickel-rich oxide cathode material produced in this embodiment will bring obvious differences in its electrochemical performance by changing the ratio of metal ions of nickel, cobalt, manganese, and aluminum. Among them, the higher the nickel content, the higher the discharge capacity of the oxide cathode material. When the content of aluminum or manganese is increased, better structural stability can be provided for the material.

[0050] In the following examples, a nickel-rich hydroxide precursor material and a nickel-rich oxide cathode material are synthesized respectively by the manufacturing methods of the nickel-rich hydroxide precursor material and the nickel-rich oxide cathode material described above, and the measurement of related material properties and the evaluation of the electrical properties of the battery are carried out.

[0051] [Example 1] Nickel-rich hydroxide precursor material [Ni 0.91 Co 0.05 Mn 0.04 (OH)2

[0052] NiSO4·6H2O with a molar concentration of 1.82M and CoSO4·7H2O with a molar concentration of 0.1M were dissolved in deionized water as metal ion raw materials to prepare aqueous solution A. Also, MnSO4·H2O with a molar concentration of 0.08M was dissolved in deionized water to prepare aqueous solution B. Further, sodium hydroxide was dissolved in deionized water as a precipitant to prepare an aqueous solution C with a molar concentration of 4M, and aqueous ammonia was dissolved in deionized water as a chelating agent to prepare an aqueous solution D with a molar concentration of 7.2M. Before the coprecipitation reaction, all the above aqueous solutions were filtered in advance to remove unnecessary impurities. Among them, the weight molar concentration ratio of aqueous solution A to aqueous solution C was 1:2, and the weight molar concentration ratio of aqueous solution A to aqueous solution D was 1:3.

[0053] Aqueous solutions A, C, and D were poured into a continuous Taylor vortex reactor, and after a first coprecipitation reaction for 5 hours, aqueous solution B was poured into the continuous Taylor vortex reactor, and a second coprecipitation reaction with aqueous solution A was carried out for 25 hours. Also, for the second coprecipitation reaction, the reaction temperature was 60 °C, the pH value of the reaction environment was 11.2, and the reaction was stably generated by controlling the flow rate of NaOH. The continuous Taylor vortex reactor had an inner cylinder rotation speed of 600 rpm, and continuous production was carried out under the condition that the supply rates of aqueous solution A and aqueous solution B were 1.703 ml / min. The precipitate that had undergone the second coprecipitation reaction was collected at the outlet end of the cylindrical chamber, washed multiple times with ethanol and deionized water to remove the remaining residual ions, and placed in an oven and dried at a temperature of 60 °C for 12 hours. Thereby, a [Ni 0.91 Co 0.05 Mn 0.04 (OH)2 hydroxide precursor with an element concentration gradient was obtained, which is denoted as the CG-NCM precursor in this example.

[0054] [Example 2] Nickel-rich oxide cathode material Li[Ni 0.90 Co 0.04 Mn 0.03 Al 0.03 O2

[0055] 0.15 g of Al(OH)3 was dispersed in 20 ml of ethanol, 5 g of the CG-NCM precursor powder was added and thoroughly mixed to complete the mixture. After that, the mixture was heated to complete drying at 80 °C to obtain mixture a. Next, LiOH·H2O and the mixture a were subjected to grinding and mixing for 5 hours at a rotation speed of 100 rpm using a ball mill at a molar ratio of 1:1.05 to obtain mixture b. In this example, grinding and mixing (the ratio of the sample to the ball was 1:1) were carried out with PU balls or agate balls. Finally, the mixture b was subjected to three-stage calcination heat treatment in a pure oxygen atmosphere. The temperature of the first stage was 150 °C and the time was 2 hours. The temperature of the second stage was 550 °C and the time was 6 hours. The temperature of the third stage was 730 °C and the time was 20 hours. The heating rate for these three stages was set to 2 °C / min in all cases. Thereby, Li[Ni 0.90 Co0.04 Mn 0.03 Al 0.03 An O2 oxide cathode material is obtained, which is denoted as CG-NCMA oxide in this example.

[0056] To compare the effects of two types of oxide cathode materials with different concentration distributions, a nickel-rich hydroxide precursor material with a uniform concentration distribution was produced under the same manufacturing method and parameter conditions. Specifically, metal ion raw materials of nickel, cobalt, manganese, and aluminum were all dissolved in a single solution, directly poured into the TFR to carry out a coprecipitation reaction, and Ni with a uniform concentration (Uniform concentration) 0.90 Co 0.04 Mn 0.03 Al 0.03 (OH)2 precursor was produced, and finally, calcination heat treatment was carried out under the same conditions as above. Thereby, a Li[Ni 0.90 Co 0.04 Mn 0.03 Al 0.03 O2 oxide cathode material is obtained, which is denoted as UC-NCMA oxide here.

[0057] [Comparative Example 1] Using TFR, a hydroxide precursor with a uniform concentration distribution was produced in the same manner as in Example 1. Among them, metal ion raw materials of nickel, cobalt, manganese, and aluminum were all dissolved in a single solution and directly poured into the TFR to carry out a coprecipitation reaction. Thereby, [Ni with a uniform concentration (Uniform concentration) 0.90 Co 0.04 Mn 0.03 Al 0.03 (OH)2 hydroxide precursor is obtained, which is denoted as UC-NCMA precursor.

[0058] [Comparative Example 2] The powder of the UC-NCMA precursor after drying was subjected to calcination heat treatment under the same conditions as in Example 2. Thereby, Li[Ni 0.90 Co 0.04 Mn 0.03 Al 0.03An O2 oxide sample was obtained and denoted as UC-NCMA oxide.

[0059] Hereinafter, Examples and Comparative Examples of the present invention will be compared by analysis and measurement of each material.

[0060] [Crystal plane intensity ratio analysis] The crystal plane intensity ratios of two types of hydroxide precursors, CG-NCM and UC-NCMA, were analyzed using an X-ray diffractometer (XRD). As shown in Figure 3, the preferred crystal orientation of the UC-NCMA precursor produced using TFR is the (001) crystal plane (2θ = 19.2°), and the preferred crystal orientation of the CG-NCM precursor produced using TFR in the method of the present invention is the (101) crystal plane (2θ = 38.6°). Thus, the intensity ratio (I (101) / I (001) ) of the (101) crystal plane to the (001) crystal plane of the CG-NCM precursor produced by TFR is 1.45, far exceeding I (101) / I (001) = 0.82 of the UC-NCMA precursor produced by TFR.

[0061] [Particle size analysis] The particle sizes of two types of hydroxide precursors, CG-NCM and UC-NCMA, produced by TFR were analyzed using dynamic light scattering (DLS). As shown in Figure 4, the two peaks in the particle size distribution of the UC-NCMA precursor were located at 0.24 μm and 6.76 μm respectively, while the two peaks in the particle size distribution of the CG-NCM precursor were located at 0.26 μm and 8.15 μm respectively. Thus, it was found that the particle size of the CG-NCM precursor particles is relatively large and more uniformly aggregated.

[0062] [Surface morphology analysis] The surface morphologies of two types of hydroxide precursors, CG-NCM and UC-NCMA, produced by TFR were observed using a scanning electron microscope (SEM). Figures 5(a1) to 5(a4) are SEM images of the UC-NCMA precursor at different magnifications. Figures 5(b1) to 5(b4) are SEM images of the CG-NCM precursor at different magnifications. As shown in Figures 5(a3) and 5(a4), the primary particles of the UC-NCMA precursor with a uniform concentration have a granular distribution in morphology, and as shown in Figures 5(a1) and 5(a2), its secondary particles were formed. Also, as shown in Figures 5(b3) and 5(b4), the primary particles of the CG-NCM precursor have a needle-like shape in morphology, and as shown in Figures 5(b1) and 5(b2), its secondary particles were formed. The one-dimensional structure of the needle-like primary particles of the CG-NCM precursor can resist micro cracks caused by tensile and compressive stresses due to the expansion and contraction during the long-term charge-discharge process.

[0063] From the above, the method of the present invention can improve the manufacturing efficiency of continuity and large-scale production by manufacturing the CG-NCM hydroxide precursor using TFR. In addition, the particles of the manufactured nickel-rich hydroxide precursor are uniform and the particle size is concentrated, and it has a needle-like primary particle morphology with a special one-dimensional structure.

[0064] [Observation of the distribution of metal element components in nickel-rich oxides][[ID=X]] [Analytical apparatus and method][[ID=Y]] The diffraction patterns of the CG-NCM precursor and CG-NCMA oxide powders were obtained using a Bruker D2 PHASER (Cu Kα5, λ = 0.1534753 nm, 30 kV; Germany), and quantitative analysis was performed using the Rietveld analysis method with software TOPAS (v.4.0). The microstructure, surface morphology, and longitudinal section of the manufactured powder samples were observed using a scanning electron microscope (SEM; JOEL, JSM-IT200 InTouch Scope TM, 15 kV; Japan), and energy-dispersive X-ray spectroscopy (EDS) was carried out. To elucidate the elemental distribution in the internal structure of the particles of the CG-NCM precursor and CG-NCMA oxide powders, a focused ion beam (FIB; FEI Helios G4 UX) was used to perform cutting analysis of the particle samples. A high-resolution transmission electron microscope (HR-TEM; JEOL JEM-2100F; Japan) was used for the characterization analysis of the microstructure of the crystals. An X-ray photoelectron spectroscopy (XPS; PHI5600, PerkinElmer; USA) was used to analyze the oxidation numbers of transition metal elements, C, and O atoms, and data fitting and analysis were performed using an Al Kα (1486.6 eV) excitation source and XPSPEAK 4.1.

[0065] [FIB / SEM EDS Scanning Analysis] Since the CG-NCM precursor of Example 1 of the present invention was manufactured at an ideal rotation speed (600 rpm) and pH value (11.2) in TFR, the obtained spherical particles have a concentrated particle size distribution and excellent sphericity in their structure. Further, the obtained CG-NCM precursor having a manganese concentration gradient and an aluminum source were sufficiently mixed and calcined heat-treated under ideal conditions, whereby a CG-NCMA oxide cathode material containing a large amount of manganese element in the outer layer and containing aluminum element in the surface layer was obtained. FIGS. 6(a) and 6(b) are high / low magnification SEM images of the CG-NCM precursor manufactured using the method of the present invention, respectively. The high magnification SEM image shows the nano-level needle-like morphology of its primary particles, and the low magnification SEM image shows its spherical secondary particles (particle size of about 8 to 12 μm). Further, the particles of the CG-NCM precursor were cut by FIB, and the component distribution of metal elements on the cut surface was analyzed by line scan. In FIG. 6(c), the component distribution of each element along the longitudinal section (arrow) in the CG-NCM precursor is shown. It was found that the nickel concentration in the inner layer is higher than that in the outer layer closer to both left and right sides, and the manganese concentration exhibits a concentration gradient distribution that gradually increases in order from the inner layer to the outer layer. Further, from FIG. 6(d), it was found that the XRD diffraction pattern of the CG-NCM precursor has no extra impurity phase and has distinct characteristic peaks. That is, although the outer layer of the particle contains a large amount of manganese element, since the manganese cation has already been fused with the structure of the CG-NCM precursor, the CG-NCM precursor is not a manganese hydroxide crystal phase formed alone, but a homogeneous structure having an element concentration gradient distribution in order from the inner layer to the outer layer.

[0066] As shown in FIGS. 7(a) to 7(d) respectively, in addition to maintaining the spherical morphology of the secondary particles of the UC-NCMA oxide and the CG-NCMA oxide after the calcination heat treatment, the primary particles having the nano-level needle-like morphology of the CG-NCMA oxide formed a rod-like particle distribution having excellent crystallinity. Further, from the EDS element maps of FIGS. 7(e) and 7(f), it was found that the surface of a single spherical secondary particle is composed of four kinds of elements of nickel, cobalt, manganese, and aluminum, and all metal element components are uniformly distributed.

[0067] [Analysis of XRD Diffraction Pattern by the Rietveld Method] Figure 8(a) shows a comparison of the XRD diffraction patterns of the UC-NCMA oxide and CG-NCMA oxide powder samples manufactured using the method of the present invention. From the drawing, it was found that all diffraction peaks could accurately correspond to the hexagonal α-NaFeO2 structure of the R-3m space group with high crystallinity. Also, since it was discovered that the (006) / (012) characteristic peaks and the (018) / (110) characteristic peaks were significantly split, it was understood that the analyzed material is a crystal with a regular structure. Furthermore, the value R of the ratio of the (003) / (104) peaks of the UC-NCMA oxide manufactured by the method of the present invention is 1.68, and the value R of the ratio of the (003) / (104) peaks of the CG-NCMA oxide is 1.55, both of which far exceed 1.2. That is, since the powder samples of the UC-NCMA oxide and CG-NCMA oxide were manufactured in a situation with little cation mixing, such NCMA-based cathode materials have excellent crystal structures. Next, as shown in Figures 8(b) and 8(c), the Rietveld analysis method was used to perform fitting on the XRD diffraction pattern, and the lattice constants and analysis results of the two types of powder samples were compared. The related data are shown in Table 1.

[0068]

Table 1

[0069] [TEM Image Analysis] As shown in FIGS. 9(a) and 9(b), the microstructures of the UC-NCMA oxide and CG-NCMA oxide samples were observed using TEM images. The primary particle samples of the UC-NCMA oxide and CG-NCMA oxide produced by the method of the present invention have a distinct layered crystal structure. When the lattice fringes in the two types of primary particle samples were matched with the (003) crystal plane of the hexagonal system using microscopic image analysis software, it was found that the interplanar spacing of both was approximately 0.47 nm. In addition, the selected area electron diffraction (SAED) pattern indicated that these primary particle samples have excellent crystallinity and a perfect laminated structure. The measurement and analysis by TEM-EDS in FIG. 9(b) showed the concentration gradient distribution of the primary particle sample of the CG-NCMA oxide. The analysis results showed that all metal elements were uniformly distributed throughout the primary particles, and the concentrations of manganese and aluminum elements on the surface of the particles were much higher than the concentration of nickel element, which is consistent with the results of the FIB / SEM EDS line scan. When the surface of the particles at the grain boundaries has relatively high concentrations of manganese and aluminum elements, the side reaction between the cathode material and the surrounding electrolyte can be reduced, and the structural stability of the cathode material can be improved, thereby improving the charge-discharge cycle performance of the lithium-ion battery.

[0070] [Measurement and Analysis of XPS Spectrum] To analyze the elemental composition and valence of transition metals, samples of the CG-NCMA oxide and UC-NCMA oxide were measured using an X-ray photoelectron spectrometer. As shown in FIG. 10(a), in the 2p spectrum of Ni, two different peaks at approximately 855 eV (Ni 2p3 / 2) and approximately 872 eV (Ni 2p1 / 2), and two accompanying satellite peaks were observed. Among them, the peak near 855 eV is obtained by superimposing and fitting the peaks of Ni 3+ and Ni 2+ on the surface of the cathode material. Ni 2+ ions that can easily move from the TM layer to the lithium layer are Li +Occupying the ion sites can cause permanent site exchange (cation mixing), which may lead to capacity degradation of the battery.

[0071] From the results of the semi - quantitative analysis and Figure 10(a), it was found that the ratio of Ni ions in the CG - NCMA oxide is significantly lower than that in the UC - NCMA oxide (CG - NCMA: 6%, UC - NCMA: 46%). Also, 2+ the concentration gradient distribution of Mn ions can reduce the amount of Ni becoming Ni at the surface region of the cathode material, and thus can change the valence of Ni ions in the surface region. Also, the CG - NCMA oxide has a higher ratio of Ni ions, that is, such a material becomes to have a high oxidation number after high - temperature calcination and can effectively reduce cation mixing. 4+ the concentration gradient distribution of Mn ions can reduce the amount of Ni becoming Ni at the surface region of the cathode material, and thus can change the valence of Ni ions in the surface region. Also, the CG - NCMA oxide has a higher ratio of Ni ions, that is, such a material becomes to have a high oxidation number after high - temperature calcination and can effectively reduce cation mixing. 3+ becoming Ni 2+ ions, and thus can change the valence of Ni ions in the surface region. Also, the CG - NCMA oxide has a higher ratio of Ni ions, that is, such a material becomes to have a high oxidation number after high - temperature calcination and can effectively reduce cation mixing. 3+ ions, and thus can change the valence of Ni ions in the surface region. Also, the CG - NCMA oxide has a higher ratio of Ni ions, that is, such a material becomes to have a high oxidation number after high - temperature calcination and can effectively reduce cation mixing.

[0072] Figure 10(b) is the 1s spectrum of O, which is a graph obtained by fitting the characteristic peaks of O element in the lattice and the surface respectively. The characteristic peaks are located at about 529 eV and about 532 eV respectively. The low intensity of the oxygen signal of C = O in the CG - NCMA oxide means that the amount of Li2CO3 residue on its surface is small. Figures 10(c) and 10(d) are the XPS spectra obtained by fitting Co 2p and Mn 2p respectively. Among them, the valence of cobalt is +3 (Co 3+ ), and the valence of manganese is +4 (Mn 4+ ). From Figures 10(c) and 10(d), it can be seen that for the UC - NCMA oxide, the signal intensity of Co 2p of the CG - NCMA oxide is lower and the signal intensity of Mn 2p is higher. That is, the surface region of the CG - NCMA oxide has a higher concentration of manganese element.

[0073] From the XPS spectra of the 1s of Li in Fig. 10(e) and the 1s of C in Fig. 10(f), it was found that for the UC-NCMA oxide, the signal intensities of Li and the carbon atoms of C=O on the surface of the CG-NCMA oxide were weaker. That is, the amount of impurities containing lithium components (e.g., Li2CO3 and LiOH) on the surface of the CG-NCMA oxide was small.

[0074] [Electrochemical measurement] The NCMA-based positive electrodes (including the UC-NCMA oxide positive electrode and the CG-NCMA oxide positive electrode) were formed by applying the paste of the electrodes to an aluminum foil. The composition of the electrode paste included 80% of the NCMA-based positive electrode active material, 10% of conductive carbon black (Super P: registered trademark), 10% of polyvinylidene fluoride (PVDF) adhesive, and N-methylpyrrolidone (NMP) as a solvent. Next, the positive electrode was placed in a vacuum oven at 120 °C and dried for 12 hours, and then pressed to produce a disk-shaped electrode piece with a diameter of 13 mm (mass loading: 2.5 mg / cm 2 ). Then, a lithium metal foil was used as the negative electrode, and furthermore, 1 M LiPF6 with 1:1 (volume percentage) of ethylene carbonate (EC) and diethyl carbonate (DEC) was added as the electrolyte and assembled into a CR-2032 button-type battery.

[0075] All electrochemical measurements in the present invention were performed using a BCS-805 workstation (BioLogic, France) for charge-discharge tests. For the lithium-ion battery fabricated by the above method, a charge-discharge test was carried out at 2.8~4.3 V (Li / Li +A constant current charge-discharge test was carried out within the voltage range (for...). The cycle life test was performed with charge-discharge cycles of 100 times and 200 times at a charge-discharge rate of 1C / 1C (1C = 200 mA / g). The rate capability test was carried out at low and high current rates from 0.2C to 10C. The cyclic voltammetry experiment was carried out with the voltage range controlled at 2.5 - 4.3V and measured at a sweep rate of 0.01 mV / s. Electrochemical impedance spectroscopy (EIS) analysis was performed using a MetrOhm AutoLab (registered trademark) system, with the frequency range set at 100 kHz to 0.01 Hz and the AC amplitude set at 5 mV.

[0076] Figure 11(a) shows the initial charge-discharge curves of the UC-NCMA cathode and the CG-NCMA cathode tested at a charge-discharge rate of 0.1C in the voltage range of 2.8 - 4.3V in the NCMA / / Li half-cell. The initial discharge capacity of the UC-NCMA oxide cathode is approximately 213 mAh / g, while the initial discharge capacity of the CG-NCMA oxide cathode is approximately 209 mAh / g, which is slightly lower than that of the UC-NCMA oxide cathode. The reason is that the nickel element with a concentration gradient distribution in the CG-NCMA oxide has a relatively low content in the outer layer and the aluminum element exists on its surface layer.

[0077] As shown in Figures 11(b) and 11(d), under the condition of an upper limit voltage of 4.3V, the rate performance of the two types of cathodes was measured at low and high discharge rates of 0.2, 0.5, 1, 3, 5, and 10C. The results show that the discharge capacity of the CG-NCMA oxide cathode is higher than that of the UC-NCMA oxide cathode. Especially at high discharge rates of 5C and 10C, the discharge capacities of the CG-NCMA oxide cathode are 168.7 and 159.5 mAh / g respectively, while the discharge capacities of the UC-NCMA oxide cathode are only 146.8 and 127.7 mAh / g respectively. The low and high discharge curves of the two types of cathodes are shown in Figure 12. Also, Figure 11(d) shows that at a high discharge rate of 10C, the CG-NCMA oxide cathode has a capacity retention rate of about 83% of the 0.2C discharge capacity (100%), while the UC-NCMA oxide cathode has a capacity retention rate of only about 67%.

[0078] From the above, by using the CG-NCMA oxide cathode, the electrochemical performance of the lithium-ion battery can be improved. The reason is that it has a complete and stable crystal structure, and in the charge-discharge process, the structure has resistance to the distortion of the material. In contrast, the UC-NCMA oxide cathode is prone to deterioration of the discharge capacity at a high discharge rate. The reasons are considered to be that microcracks have already occurred in the cathode material and a phase transition has occurred in the structure of the oxide.

[0079] Figure 11(c) shows a comparison of the electrochemical performance of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode after 100 charge-discharge cycles under the conditions of a charge-discharge rate of 1C / 1C, a cut-off voltage of 2.8 - 4.3V, and an environmental temperature of 25°C. The results show that the CG-NCMA oxide cathode reaches a maintenance rate of 91.5% of the initial discharge capacity and has excellent cycle stability, while the UC-NCMA oxide cathode has a maintenance rate of only 83.4% of the initial discharge capacity. Also, as shown in Figure 11(e), after a 200 charge-discharge cycle test under the same conditions, the CG-NCMA oxide cathode still has a maintenance rate of 80.2% of the initial discharge capacity, while the capacity maintenance rate of the UC-NCMA oxide cathode remains only 64.1%.

[0080] Table 2 shows a comparison of the electrochemical performance of the NCMA / / Li battery composed of the cathode material with an element concentration gradient manufactured by the method of the present invention and lithium-ion batteries in a plurality of prior arts. From Table 2, it was found that the CG-NCMA oxide cathode of the present invention is excellent in cycle stability. The reason is that the CG-NCMA oxide has excellent material structure stability due to the relatively high concentrations of manganese element in the outer layer and aluminum element in the surface layer, and such an element concentration gradient distribution can effectively suppress side reactions caused by the contact between the cathode and the electrolyte in the long-term cycle process.

[0081]

Table 2

[0082] Prior art documents in Table 2: 1. Y. Zhang, H. Li, J. Liu, J. Zhang, F. Cheng, J. Chen, LiNi 0.90 Co 0.07 Mg 0.03 O2 cathode materials with Mg-concentration gradient for rechargeable lithium-ion batteries, Journal of Materials Chemistry A 7 (36) (2019) 20958-20964. 2. C.-L. Xu, W. Xiang, Z.-G. Wu, Y.-D. Xu, Y.-C. Li, M.-Z. Chen, G. Xiao Dong, G.-P. Lv, J. Zhang, B.-H. Zhong, Constructing a Protective Pillaring Layer by Incorporating Gradient Mn 4+ to Stabilize the Surface / Interfacial Structure of LiNi 0.815 Co 0.15 Al 0.035 O2 Cathode, ACS Applied Materials & Interfaces 10 (33) (2018) 27821-27830. 3. U.-H. Kim, S.-T. Myung, C. S. Yoon, Y.-K. Sun, Extending the Battery Life Using an Al- Doped Li[Ni 0.76 Co 0.09 Mn 0.15 O2 Cathode with Concentration Gradients for Lithium Ion Batteries, ACS Energy Letters 2 (8) (2017) 1848-1854. 4. P. Hou, F. Li, Y. Sun, H. Li, X. Xu, T. Zhai, Multishell Precursors Facilitated Synthesis of Concentration-Gradient Nickel-Rich Cathodes for Long-Life and High-Rate Lithium- Ion Batteries, ACS Applied Materials and Interfaces 10 (29) (2018) 24508-24515. 5. K. Du, C. Hua, C. Tan, Z. Peng, Y. Cao, G. Hu, A high-powered concentration-gradient Li(Ni 0.85 Co 0.12 Mn 0.03 )O2 cathode material for lithium ion batteries, Journal of Power Sources 263 (2014) 203-208.

[0083] Figures 13(a) and 13(b) are the differential capacity-voltage analysis (Differential capacity analysis, DCA. dQ / dV vs. V) curves after three cycles at a charge-discharge rate of 0.1C. In these figures, due to the polarization phenomenon in subsequent cycles, the negative peak and the positive peak shifted positively and negatively, respectively, so that a phase transition of three typical interconversions between the hexagonal system and the monoclinic system can be observed. In the curves of the three cycles shown in Figures 13(a) and 13(b), most parts overlap well, that is, at low charge-discharge rates, both the UC-NCMA oxide cathode and the CG-NCMA oxide cathode have high stability and electrochemical reversibility.

[0084] However, as shown in Fig. 13(c), it was found that after 100 charge-discharge cycles were performed on the UC-NCMA oxide cathode at a charge-discharge rate of 1C, an obvious and severe polarization phenomenon occurred. Among them, the cathode peak near 4.2V is the criterion for judging the reversibility of the H2⇔H3 phase transition. In contrast, as shown in Fig. 13(d), for the CG-NCMA oxide cathode in 100 charge-discharge cycles at a charge-discharge rate of 1C, the dQ / dV curves almost overlap. Thus, the CG-NCMA oxide cathode manufactured by the method of the present invention has excellent internal structural stability and can effectively improve the electrochemical performance of lithium-ion batteries.

[0085] The cyclic voltammetry (CV) method was used to analyze the reversibility of the electrochemical reaction at the cathode of the lithium-ion battery. The results of the first 3 cycles of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode are shown in Figs. 14(a) and 14(b) respectively, and qualitative analysis was performed on the voltage at which the electrochemical reaction and electron transfer in the electrode occur. A typical CV curve has three pairs of oxidation-reduction peaks, indicating the H1⇔M⇔H2 phase transition due to the intercalation-deintercalation of Li + ions. Due to the delay in the dynamic response of the H1→M phase transition in the initial de-lithiation process, the oxidation potential increased slightly. Also, after being activated by the first cycle, the fact that the symmetric oxidation-reduction peaks in the second and third cycles almost overlap indicates that the cathode material has excellent electrochemical reversibility.

[0086] The definition of the polarization voltage is the difference (ΔV) between the values of the first anode peak and cathode peak near 3.7 - 4.0V in the first activation cycle, which is the criterion for judging the reversibility of the cathode material. The ΔV values of the first anode peak and cathode peak (H1⇔M) of the CG-NCMA oxide cathode and the UC-NCMA oxide cathode are 192.7mV and 211.6mV respectively. Among them, the fact that the CG-NCMA oxide cathode has a lower polarization voltage means that it has higher structural stability and thus excellent reversible kinetic reactions.

[0087] Figures 14(c) and 14(d) are the electrochemical impedance spectra of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode after performing the initial cycle and 100 cycles at the charge and discharge rate of 1C, respectively. All of their curves have a curve region at the high frequency (and medium-high frequency) position and a straight line region at the low frequency position. The fitting of the EIS curve was performed using the proposed equivalent circuit model. Among them, R b is the bulk resistance, and R sei is the solid electrolyte interphase (SEI) resistance, and R ct is the charge transfer resistance, CPE (Constant phase element) is the constant phase element, and Z W is the value of the Warburg impedance representing the diffusion resistance of Li + ions in the solid electrode.

[0088] The electrochemical impedance spectra of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode were fitted to their respective equivalent circuit models using the software ZView, and the obtained numerical values are shown in Table 3. The results in Table 3 show that the initial R ct = 263.1 Ω of the CG-NCMA oxide cathode is much lower than the initial R ct = 355.6 Ω of the UC-NCMA oxide cathode. That is, when the nickel-rich UC-NCMA-based cathode is exposed to the electrolyte, an NiO-like inert region is likely to occur on its surface, increasing the charge transfer resistance. Also, as shown in Figure 14(d), after the UC-NCMA oxide cathode and the CG-NCMA oxide cathode perform 100 cycles at the charge and discharge rate of 1C / 1C, both of the two EIS curves are curve lines. When fitting them to the equivalent circuit model (the inserted diagram in Figure 14(d)), it is observed that not only is the R ct value of the CG-NCMA oxide cathode after cycling lower, but also the R sei = 66.7 Ω of the CG-NCMA oxide cathode tends to be lower than the R sei = 95.4 Ω of the UC-NCMA oxide cathode, which is consistent with the above experimental results.

[0089]

Table 3

[0090] In the long - term cycle process, active secondary particles are easily affected by hydrofluoric fluoride (HF) generated in the electrolyte or inevitable impurities caused by side reactions. Therefore, the CG - NCMA oxide cathode with an elemental concentration gradient produced by the method of the present invention has a large amount of manganese and aluminum elemental components in the outer layer and the surface layer respectively, which can effectively suppress the occurrence of side reactions at the interface between the cathode material and the electrolyte, prevent the destruction of the electrode structure, and thus improve the electrochemical performance and cycle stability of the entire lithium - ion battery.

[0091] [In - situ X - ray diffraction analysis] One of the most important functions of the concentration gradient is to maximize the discharge capacity by confining the nickel - rich phase in the inner layer of the active material particles. However, the improvement of the cycle stability of the battery and the structural stability of the electrode cannot be completely attributed to the result brought about by the concentration gradient. This is because the CG - NCMA oxide contains a large amount of nickel component (Ni content 90%). In addition, due to the volume change of the battery during the charge - discharge cycle, the cathode structure is subjected to enormous pressure. And since most of the expansion and contraction occur in the c - axis direction, the strain is anisotropic. Generally, in the process of de - intercalation (i.e., charging) of Li + ions into the cathode and subsequent intercalation (i.e., discharging), the anisotropic strain generated is adjusted through the relevant directions of the plane composed of the a - axis and the b - axis.

[0092] To clarify the mechanisms and causes of battery capacity degradation, the change in lattice constant during the second charge-discharge cycle was measured using the in-situ XRD method. Figures 15(a) and 15(b) show the XRD diffraction patterns during the charge-discharge processes of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode, respectively. As shown in Figures 16(a) and 16(b), isocurves were extracted from Figures 15(a) and 15(b), and comparisons were made for different characteristic peaks. During the charging process, due to the electrostatic repulsion between adjacent O layers, when Li + ions desorbed from the cathode, the (003) characteristic peak continued to shift to the left (i.e., the lattice expanded in the c-axis direction). Also, as shown in Figures 13(a)-(d) and 14(a)(b), due to the transition from the H2 phase to the H3 phase, the (003) characteristic peak rapidly decreased near 4.1 V, and the diffraction angle shifted to a high angle. This is called the lattice contraction behavior.

[0093] Moreover, during the charging process, since the ionic radius in the TM layer decreased, the (101) characteristic peak shifted to the right, i.e., the a-axis contracted. During the discharging process, the same process was repeated in the reverse direction, and when the discharging process was completed, all the peaks finally returned to their original Bragg positions. This proved that the NCMA-based cathode has structural reversibility. Other peaks also followed the same movement process, each undergoing a lattice expansion or contraction process. Both types of cathodes underwent the same charge-discharge process and received the same level of strain, but during the cycle process, the degree of expansion and contraction of the CG-NCMA oxide cathode was lower, which was shown in Figure 16(b) to contribute to the extension of the cycle life of the lithium-ion battery.

[0094] Table 4 and Figures 16(c)-(e) show Li +It is the result of the change in lattice constant in the ion intercalation / deintercalation process. From this, it was found that the H2⇔H3 phase transition is the largest. That is, the lattice change Δc = 1.92% of the (003) crystal plane in the CG-NCMA oxide cathode is much smaller than Δc = 3.38% of the UC-NCMA oxide cathode, and the lattice change Δa = 1.64% and the lattice volume change Δvol = 3.78% of the (101) crystal plane in the CG-NCMA oxide cathode are much lower than Δa = 2.36% and Δvol = 7.80% of the UC-NCMA oxide cathode. Thus, the changes in the three lattice constants (Δa, Δc, and Δvol) have the same tendency.

[0095]

Table 4

[0096] From the in-situ X-ray diffraction analysis, it was found that the primary particles of the CG-NCMA oxide cathode have a unique one-dimensional needle-like spatial structure distribution, and in addition, due to its stronger outward extensibility, it can effectively reduce the volume change of the CG-NCMA oxide cathode during deep charging and improve its cycle stability. Also, due to the anisotropic shrinkage / expansion in randomly arranged primary particles, tensile / compressive stress will be partially concentrated, resulting in the occurrence of microcracks and ultimately structural failure. On the other hand, when using the CG-NCMA oxide cathode, the manganese-rich regions and some aluminum regions in the outer layer and surface layer of its active material particles can suppress the high volume change rate that may occur in the structure during the charge-discharge process, and can significantly and effectively improve the electrochemical performance and stability of the CG-NCMA cathode material.

[0097] [Fault Analysis] To elucidate the influence of the concentration gradient on the NCMA-based cathode structure and mechanical strength, the NCMA-based / / Li half-cell after charge-discharge cycles was disassembled, and the NCMA-based electrode after cycles was observed by XRD and SEM.

[0098] There was no significant difference in the positions, shapes, and relative intensities of the characteristic peaks of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode shown in the XRD diffraction pattern of Fig. 17(a), indicating that the capacity degradation of the lithium-ion battery was not caused only by the destruction of its electrode structure or irreversible phase transformation. However, as shown in the enlarged XRD diffraction pattern of a part of Fig. 17(b), compared with the CG-NCMA oxide cathode, the (003) characteristic peak in the UC-NCMA oxide cathode shifted more significantly towards a lower angle, with a difference of Δ2θ = 0.54° from the (003) characteristic peak in the CG-NCMA oxide cathode. That is, long-term cycling causes irreversible damage to the structure of the active material particles in the UC-NCMA oxide, while the CG-NCMA oxide cathode has better resistance to mechanical stress caused by long-term cycling.

[0099] Figs. 17(c) and 17(d) are SEM images of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode, respectively, after 100 cycles at a high charge-discharge rate of 1C / 1C. During the charge-discharge process, as Li + ions repeatedly intercalate and de-intercalate into the lattice, it causes a certain degree of mechanical stress, resulting in cracks along the grain boundaries of the primary particles and eventually disintegration. Fig. 17(c) shows that the secondary particles of the UC-NCMA oxide cathode were pulverized into a large number of primary particles after long-term cycling, that is, the strength of its particle structure was insufficient and it could not withstand the long-term charge-discharge cycle test. In contrast, Fig. 17(d) shows that even when the CG-NCMA oxide cathode was cycled 100 times at a high charge-discharge rate, there were only slight cracks in its secondary particles, but its structure remained intact. That is, the structure of the CG-NCMA oxide cathode material was sufficiently strengthened and could withstand the mechanical stress generated during the long-term cycling process at a high charge-discharge rate. In addition, the manganese-rich distribution and aluminum element content distribution in the outer layer and surface layer of the CG-NCMA oxide cathode contribute to the effect of stabilizing the structure of the CG-NCMA oxide cathode under the conditions of high voltage (≧4.3V) and high charge-discharge rate (≧1C).

[0100] Next, the secondary particles of the NCMA-based electrode that had undergone charge-discharge cycles were cut using focused ion beam (FIB) technology, and the internal structure of the longitudinal section of the cut particles was observed using SEM. Thereby, the degree of microcracks in the internal structure of the secondary particles formed in the lithium-ion battery through long-term charge-discharge cycles was further investigated. As shown in FIGS. 18(a) and 18(b), there were more obvious cracks along the grain boundaries of the primary particles inside the secondary particles of the UC-NCMA oxide cathode. When the charge-discharge cycles were repeated, the primary particles began to separate from each other, causing structural damage. In contrast, as shown in FIGS. 18(c) and 18(d), the CG-NCMA oxide cathode maintained a complete arrangement of primary particles even after repeated charge-discharge cycles, and there were almost no cracks at the grain boundaries of the primary particles.

[0101] The experimental results of cutting the longitudinal section with FIB demonstrated the following. When the UC-NCMA oxide cathode undergoes long-term charge-discharge cycles, microcracks are likely to occur at the grain boundaries of the primary particles in its secondary particles, and the range of the cracks is likely to extend and expand. In addition, the subsequent penetration of the electrolyte and the reaction with the electrolyte accelerate the loss of the mechanical integrity of its structure. Also, since the surface area of the particles exposed to the electrolyte increases with the long-term cycling of the battery, the damage to the microstructure on the surface of the particles becomes severe, and as a result, the particles of the UC-NCMA oxide cathode are crushed. In contrast, the stable structure of the manganese-rich outer layer and the aluminum-containing surface layer in the CG-NCMA oxide cathode can effectively suppress the generation and expansion of microcracks, and prevent the disintegration and pulverization of secondary particles due to the formation of microcracks during the long-term cycling process.

[0102] After performing 100 charge-discharge cycles at a high charge-discharge rate of 1C / 1C, the surface structures of the active material particles of the UC-NCMA oxide cathode and the CG-NCMA oxide cathode were observed using TEM for different degrees of phase transitions that occurred continuously during the charge-discharge cycle process. As shown in Fig. 18(e), for the primary particles of the UC-NCMA oxide cathode that had undergone long-term charge-discharge cycles, significant phase transitions occurred during the frequent intercalation and deintercalation of Li + ions. Among them, the selected area electron diffraction (SAED) pattern in region I showed a perfect R-3m layered structure with alternating TM layers and Li ions. Furthermore, there was active Ni 4+ material at the edge of the particles (this is a common phenomenon in nickel-rich oxide cathodes during charge-discharge cycles), so an Fm-3m surface layer similar to NiO was detected in region II. On the other hand, as shown in Fig. 18(f), since the NiO-like damaged layer found in the CG-NCMA oxide cathode was limited to about 1 nm at the edge of the particles, it could not be distinguished by the electron diffraction of the selected regions I and II.

[0103] From the above, the present invention aims to provide a method for manufacturing a nickel-rich cathode material for application in lithium-ion batteries, which can improve the electrochemical performance of lithium-ion batteries and the mechanical stability of their cathode materials. In the above method, a CG-NCM precursor with an element concentration gradient is manufactured by a coprecipitation reaction using a continuous Taylor vortex reactor under conditions such as a suitable environmental temperature, pH value, heating time, and supply rates of aqueous solution A and aqueous solution B, and further a CG-NCMA oxide with a high-concentration manganese and aluminum element distribution on its surface is manufactured. It can be proved by EDS line scan that the CG-NCMA oxide cathode material has a homogeneous structure with an element concentration gradient distribution (the concentration of nickel element gradually decreases in order from the inner layer to the outer layer, and the concentration of manganese element gradually increases in order from the inner layer to the outer layer), and its surface layer also has a homogeneous aluminum element distribution and is a NCMA quaternary system structure.

[0104] The CG-NCMA oxide cathode manufactured by the method of the present invention has excellent electrochemical performance. At a charge-discharge rate of 20 mA / g, its initial discharge capacity is Q sp,dchg,ini = 209 mAh / g, and its initial Coulombic efficiency (ICE) is 89.4%, which is higher than the CE = 82.9% of the UC-NCMA oxide cathode. After the CG-NCMA oxide cathode has undergone 100 charge-discharge cycles at a charge-discharge rate of 1C / 1C, its capacity retention rate is CR 1-100 = 91.5%, and the capacity retention rate after 200 charge-discharge cycles is CR 1-200 = 80.2%, both of which are much higher than those of the UC-NCMA oxide cathode (CR 1-100 = 83.4% and CR 1-200 = 64.1%).

[0105] Moreover, from the results of cyclic voltammetry and differential capacitance-voltage analysis, it was found that the degree of voltage polarization of the CG-NCMA oxide cathode decreased significantly. From the results of in-situ X-ray diffraction analysis, in the charge-discharge process, the mechanical stress received by the electrode and its influence on the battery performance were found. Among them, since the change in stress in the CG-NCMA oxide cathode is relatively small, the possibility of its structure being destroyed is also relatively low. In addition, the above experimental results can be proved by performing failure analysis on the electrode that has undergone long-term charge-discharge cycles by XRD and SEM. In the above analysis, the secondary particles of the UC-NCMA oxide cathode material had already disintegrated into a large number of primary particles, but the secondary particles of the CG-NCMA oxide cathode material could maintain a more complete structure.

[0106] As described above, the nickel-rich hydroxide precursor obtained by combining a continuous Taylor vortex reactor with a coprecipitation reaction has a homogeneous structure with a nickel-rich inner layer and a manganese-rich outer layer having an elemental concentration gradient distribution, which can reduce the interfacial impedance during lithium ion movement and increase the lithium ion migration path. Further, the nickel-rich oxide cathode material having an elemental concentration gradient distribution produced from the nickel-rich hydroxide precursor can improve the electrochemical performance such as the charge and discharge rate and long-term cycle stability of a lithium ion battery and the structural stability of the nickel-rich cathode material.

[0107] The above embodiments are merely specific examples for explaining the present invention, which are intended to show the features of the present invention and are not intended to list all forms of the technical concept of the present invention, nor are they intended to limit the present invention to the forms of the technical concept disclosed in the embodiments. Various modifications and changes within the scope not departing from the gist of the present invention are easy for those skilled in the art. The selected and described embodiments are for preferably interpreting the principles and actual applications of the present invention, and those skilled in the art can understand that the present invention has various modifications and embodiments suitable for specific applications.

Description of Signs

[0108] S11: Uniformly mix a metal ion raw material in deionized water to prepare a metal ion mixed solution (aqueous solution A). S12: Dissolve a manganese source in deionized water to prepare an aqueous solution B. S13: Pour aqueous solution A, a precipitant aqueous solution (aqueous solution C), and a chelating agent aqueous solution (aqueous solution D) into a continuous Taylor vortex reactor filled with deionized water to perform a first coprecipitation reaction. S14: Pour aqueous solution B into the continuous Taylor vortex reactor to perform a second coprecipitation reaction. S15: Collect the precipitate of the second coprecipitation reaction, wash it with ethanol and deionized water to remove residual ions, and then place it in an oven to dry to obtain a nickel-rich hydroxide precursor. S21: Disperse the aluminum source in ethanol, add the nickel-rich hydroxide precursor material and mix to obtain a mixture, and heat the mixture until completely dry to obtain mixture a. S22: Use a ball mill to grind and mix the lithium source and mixture a in S21 with grinding balls to obtain mixture b. S23: Perform three-stage calcination heat treatment on mixture b in S22 in a high-temperature furnace.

Claims

1. A method for producing a nickel-rich hydroxide precursor material, which is a nickel cobalt manganese hydroxide having a homogeneous structure with an element concentration gradient distribution, comprising: (1) preparing an aqueous solution A in which a metal ion raw material is dissolved, preparing an aqueous solution B in which a manganese source is dissolved, preparing an aqueous solution C in which a precipitant is dissolved, preparing an aqueous solution D in which a chelating agent is dissolved, a step of pouring the aqueous solution A, the aqueous solution C, and the aqueous solution D into a continuous Taylor vortex reactor and performing a first coprecipitation reaction for 2 to 7 hours, wherein the metal ion raw material is a nickel source and a cobalt source, the nickel source is at least one selected from the group consisting of nickel sulfate, nickel oxalate, nickel acetate, nickel nitrate, nickel chloride, and nickel hydroxide, the cobalt source is at least one selected from the group consisting of cobalt sulfate, cobalt oxalate, cobalt carbonate, cobalt acetate, cobalt nitrate, cobalt chloride, and cobalt hydroxide, and the manganese source is at least one selected from the group consisting of manganese sulfate, manganese oxalate, manganese carbonate, manganese citrate, manganese acetate, manganese nitrate, manganese phosphate, electrolytic manganese dioxide, and manganese oxide; (2) a step of pouring the aqueous solution B into the continuous Taylor vortex reactor and performing a second coprecipitation reaction for 5 to 70 hours, wherein the reaction temperature of the second coprecipitation reaction is 30°C to 80°C, the pH value of the reaction environment is 9.5 to 12.5, and the rotation speed of the inner cylinder of the continuous Taylor vortex reactor is 200 rpm to 1500 rpm; (3) washing the precipitate obtained through the second coprecipitation reaction, drying it in an oven, and obtaining the nickel-rich hydroxide precursor material. A method for producing a nickel-rich hydroxide precursor material, comprising the above steps.

2. The method for producing a nickel-rich hydroxide precursor material according to claim 1, wherein the concentration of the aqueous solution A is 1.6 M to 1.92 M.

3. The method for producing a nickel-rich hydroxide precursor material according to claim 1, wherein the concentration of the aqueous solution B is 0.08 M to 0.4 M.

4. The method for producing a nickel-rich hydroxide precursor material according to claim 1, wherein the concentration of the aqueous solution C is 2.0 M to 6.0 M, and the weight molar concentration ratio of the aqueous solution A to the aqueous solution C is 1:1 to 1:

5.

5. The concentration of the aqueous solution D is 2.5 M to 9.0 M, and the weight molar concentration ratio of the aqueous solution A to the aqueous solution D is 1:1 to 1:

5. The method for producing a nickel-rich hydroxide precursor material according to claim 1.

6. The drying temperature of the oven is 60°C to 120°C, and the drying time is 6 to 24 hours. The method for producing a nickel-rich hydroxide precursor material according to claim 1.

7. The supply rate of the aqueous solution A and the aqueous solution B is 1.0 to 3.0 ml / min. The method for producing a nickel-rich hydroxide precursor material according to claim 1.

8. A method for producing a nickel-rich oxide cathode material using the method for producing a nickel-rich hydroxide precursor material according to claim 1, (a) Dispersing an aluminum source in ethanol, adding and mixing the nickel-rich hydroxide precursor material to obtain a mixture, and heating the mixture at a temperature of 80°C until it is completely dried to obtain a mixture a. The aluminum source is at least one selected from the group consisting of aluminum hydroxide, aluminum oxalate, aluminum carbonate, aluminum sulfate, aluminum acetate, aluminum nitrate, and aluminum phosphate. (b) Grinding and mixing a lithium source and the mixture a in step (a) at a molar ratio of 1:1.01 to 1:1.25 to obtain a mixture b. The lithium source is at least one selected from the group consisting of lithium hydroxide, lithium nitrate, lithium acetate, lithium chloride, lithium hydrogen phosphate, lithium phosphate, and lithium carbonate. (c) Performing a three-stage calcination heat treatment on the mixture b in step (b) to obtain the nickel-rich oxide cathode material. A method for producing a nickel-rich oxide cathode material, including the above steps.

9. The conditions for the grinding are that the rotation speed of the ball mill is 50 to 200 rpm, and the grinding time is 2 to 10 hours. The method for producing a nickel-rich oxide cathode material according to claim 8.

10. The temperature and time of the three-stage calcination heat treatment are as follows: in the first stage, the temperature is 100°C to 200°C and the time is 1 to 3 hours; in the second stage, the temperature is 500°C to 600°C and the time is 4 to 8 hours; in the third stage, the temperature is 700°C to 800°C and the time is 10 to 40 hours. The heating rate of the three-stage calcination heat treatment is 0.1 to 20°C / min in all cases. The method for producing a nickel-rich oxide cathode material according to claim 8.

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