A high-nickel cathode material, its preparation method and application

Abstract

This disclosure provides a high-nickel cathode material, its preparation method, and its application, belonging to the technical field of lithium-ion battery cathode materials. First, a high-nickel core precursor is prepared via co-precipitation. Then, a carbonate shell containing a dioxime compound is prepared using a two-step method, resulting in a core-shell structured high-nickel cathode material precursor. The dioxime compound in the carbonate shell undergoes a chelation reaction with nickel ions, thereby reducing the nickel content in the carbonate shell and improving the thermal stability of the high-nickel cathode material, solving the instability problem caused by excessively high nickel content in high-nickel cathode materials. Furthermore, due to the chelation reaction between the dioxime compound and nickel ions, the carbonate shell can form a low-nickel gradient shell structure, with the nickel content in the carbonate shell gradually decreasing along the direction away from the core structure. Additionally, this disclosure uses organic solvent washing to avoid the influence of water on the structure of the high-nickel cathode material.

Description

Technical Field

[0001] This disclosure belongs to the field of lithium-ion battery cathode material technology, and relates to a high-nickel cathode material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, with their excellent energy density, rate performance, and long lifespan, are widely used in devices such as mobile phones, digital cameras, and portable personal computers. Their application is also shifting from small mobile devices to large electric vehicle batteries, such as those for pure electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles, as well as energy storage systems. High-nickel ternary cathode materials offer advantages such as low cost, high specific capacity, and high average operating voltage, making them one of the best choices for achieving high-energy-density battery cathodes. However, high-nickel cathode materials have the following problems: (a) The high-nickel cathode materials obtained by wet co-precipitation have a high residual alkali on the surface, which is easy to react with CO2 and moisture in the air to generate Li2CO3 and LiOH, or react with electrolyte to generate by-reaction products such as HF, which leads to many problems such as difficulty in storage and unstable battery performance; generally, it needs to be removed by washing with water, but washing with water will damage the structure of the high-nickel cathode material, thereby affecting the electrochemical performance of the subsequent lithium-ion battery; (b) The nickel content of high-nickel cathode materials is too high, which will produce disadvantages such as Li / Ni cation mixing, surface reaction and crack propagation that lead to structural instability, resulting in poor cycle life and poor thermal stability of high-nickel cathode materials. Summary of the Invention

[0003] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a high-nickel cathode material with good cycle performance and high thermal stability, as well as its preparation method and application.

[0004] To achieve the above objectives, the technical solution adopted in this disclosure is as follows: Firstly, a method for preparing a high-nickel cathode material is provided, comprising the following steps:

[0005] S1: According to the chemical formula Ni x M 1-x Weigh out Ni salt and M salt according to their stoichiometric ratio and dissolve them in water to prepare nickel solution A; according to the chemical formula Ni y N 1-y The stoichiometric ratio of CO3 is used to weigh Ni salt and N salt and dissolve them in water to prepare nickel solution B; wherein, 0.5 < x < 1, 0.2 ≤ y ≤ 0.5, and M and N are each independently selected from at least one of Co, Mn, and Al;

[0006] S2: Add nickel solution A and complexing agent to the reaction vessel, adjust the pH value of the reaction with hydroxide solution, stir to carry out co-precipitation reaction, and obtain the first solution with an average particle size of 5-6 μm;

[0007] S3: Nickel solution B and the complexing agent are added concurrently to the first solution obtained in step S2 under stirring. Through co-precipitation, when the average particle size reaches 7.5–8.5 μm, a second solution is obtained. Nickel solution B, the complexing agent, and an ester solution containing a dioxime compound are added concurrently to the second solution under stirring. Through co-precipitation, when the average particle size reaches 9.5–11 μm, the addition of raw materials is stopped, resulting in a third solution. The pH of the co-precipitation reaction is adjusted using a carbonate solution.

[0008] S4: The third solution obtained in step S3 is stirred and aged, filtered, the solid obtained by filtration is washed with an ester solution containing a coating agent, and dried to obtain a core-shell structure precursor;

[0009] S5: Mix the core-shell structure precursor obtained in step S4 with a lithium source and calcine to obtain a core-shell structure high-nickel cathode material.

[0010] The high-nickel cathode material prepared in this disclosure has a full concentration gradient structure (Ni content gradually decreases from the core to the outer shell). The core of this full concentration gradient structure is to reduce the surface nickel content while maintaining a constant total nickel content, thereby improving the structural stability of the high-nickel cathode material's shell and reducing side reactions with the electrolyte. The high-Ni component inside the high-nickel cathode material exhibits significant volume effects and phase changes during charge and discharge. However, due to the low volume effect of the external low-Ni component, compressive stress is formed on the particle surface. This compressive stress increases the particle's crush resistance and promotes Li... + Diffusion within particles is beneficial for improving the cycle life of high-nickel cathode materials.

[0011] This disclosure discloses the preparation of a high-nickel nucleus precursor via a co-precipitation method. The chemical formula of the high-nickel nucleus precursor is Ni. x M 1-x (OH)₂ is used to prepare a carbonate shell containing a dioxime compound in a two-step process, resulting in a core-shell structured high-nickel cathode material precursor. The dioxime compound in the carbonate shell chelates with nickel ions, thereby reducing the nickel content in the carbonate shell. This effectively increases the nitrogen (N) content in the carbonate shell, improving the thermal stability of the high-nickel cathode material and resolving the instability issue caused by excessively high nickel content. Furthermore, the chelation reaction between the dioxime compound and nickel ions allows the carbonate shell to form a low-nickel gradient structure, with the nickel content gradually decreasing away from the core structure.

[0012] In addition, this disclosure uses organic solvent washing, which avoids the influence of water on the structure of high-nickel cathode material, improves the stability of the high-nickel cathode material structure, and thus improves the performance of high-nickel cathode material.

[0013] This disclosure uses a laser particle size analyzer to determine the particle size during the generation of core-shell structure precursors in order to determine the reaction endpoint.

[0014] In this article, the method for preparing the ester solution containing the dioxime compound is as follows: dissolving the dioxime compound in an ester solvent; the dioxime compound is at least one selected from diacetone oxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime; the ester solvent is at least one selected from ethyl acetate, propyl acetate, and dimethyl carbonate.

[0015] Using ester solvents as solvents for dioxime compounds can effectively control the nickel gradient concentration in the carbonate shell compared to other solvents, thereby improving the stability of the carbonate shell and thus enhancing the electrochemical performance and stability of high-nickel cathode materials.

[0016] In this document, the concentration of the dioxime compound in the ester solution containing the dioxime compound is 2-7 wt%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. This concentration is beneficial for the reaction to proceed and for the gradient control of the nickel content in the material.

[0017] In this article, in step S4, the coating agent is at least one of aluminum oxide and magnesium oxide.

[0018] In this disclosure, an ester solution containing a coating agent is used for washing during the washing process. On the one hand, the ester solution can further clean the nickel-containing dioxime compounds; on the other hand, the coating agent can not only adhere to the surface of the carbonate shell to form a second coating layer, but also some of the metal elements in the coating agent can be incorporated into the Ni vacancies of the carbonate shell during the calcination process, further improving the coating stability of the carbonate shell.

[0019] In this article, in step S4, the ester in the coating agent-containing ester solution is at least one of ethyl acetate, propyl acetate, and dimethyl carbonate.

[0020] Choosing ester solvents as washing solvents can avoid introducing other impurities and reduce the impact of impurities on high-nickel cathode materials.

[0021] In this document, in step S1, the Ni salt, M salt, and N salt are independently any one or a mixture of at least two of sulfate, nitrate, chloride, or acetate.

[0022] In this document, in step S5, the lithium source is at least one of lithium hydroxide, lithium carbonate, or lithium oxalate.

[0023] In this paper, in steps S2 and S3, the feeding rates of nickel solution A and nickel solution B are each independently 60-90 mL / h, for example, 60 mL / h, 65 mL / h, 70 mL / h, 75 mL / h, 80 mL / h, 85 mL / h, and 90 mL / h, but are not limited to the listed values. Other unlisted values ​​within the range are also applicable. Feeding rates that are too fast or too slow will result in uneven growth rates of the material layers.

[0024] In this text, in step S3, the feeding rate of the ester solution containing the dioxime compound is 40-55 mL / h, for example, it can be 40 mL / h, 42 mL / h, 44 mL / h, 46 mL / h, 48 mL / h, 50 mL / h, 53 mL / h, or 55 mL / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. The feeding rate is beneficial for gradient control of nickel content in high-nickel cathode materials.

[0025] In this article, in steps S2 and S3, the complexing agent is either ammonia or an ammonium salt solution;

[0026] In this document, in steps S2 and S3, the molar concentration of the complexing agent is independently selected from 0.3 to 0.5 mol / L, for example, it can be 0.3 mol / L, 0.34 mol / L, 0.37 mol / L, 0.4 mol / L, 0.42 mol / L, 0.45 mol / L, 0.48 mol / L, or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In this paper, in steps S2 and S3, the concentration of the complexing agent in the reaction system is adjusted to be maintained at 0.3–0.5 mol / L. This disclosure employs acid titration to detect the molar concentration of the complexing agent in the reaction system throughout the entire reaction process, thereby controlling the amount of complexing agent added and maintaining its concentration. The concentration of the complexing agent is beneficial for controlling the surface morphology of the particles.

[0028] In this article, in steps S2 and S3, the mass concentration of ammonia used to adjust the ammonia concentration in the reaction system is 25-28%, for example, it can be 25%, 25.5%, 25.8%, 26%, 26.4%, 26.7%, 27%, 27.2%, 27.6%, 27.8%, or 28%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In this document, the reaction temperature in steps S2 and S3 is independently selected from 50-70℃, for example, it can be 50℃, 53℃, 55℃, 57℃, 60℃, 62℃, 64℃, 67℃, 70℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] In this document, the stirring speed in steps S2 and S3 is independently selected from 800 to 1200 r / min, for example, it can be 800 r / min, 850 r / min, 870 r / min, 900 r / min, 940 r / min, 980 r / min, 1000 r / min, 1050 r / min, 1100 r / min, 1150 r / min, 1200 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The specified temperature is conducive to the reaction; the specified stirring speed is even more conducive to the formation of particle morphology.

[0032] In this paper, the pH of the reaction in step S2 is 11-12. At this pH, the growth rate of the particle core layer is ensured to be neither too fast nor too slow.

[0033] In this paper, the pH of the reaction in step S3 is 9-10. This pH ensures that the growth rate of the particle shell is neither too fast nor too slow.

[0034] In this paper, in steps S2 and S3, the pH value of the reaction system is adjusted using a hydroxide solution.

[0035] In this document, in step S4, the stirring speed is 100-250 r / min; and / or the aging temperature is 30-45℃ and the time is 10-14 h; and / or the drying temperature is 50-100℃ and the time is 5-15 h.

[0036] The aging conditions described above promote more uniform particle growth. If the drying temperature is too low, the drying time will be too long; if the drying temperature is too high, side reactions may occur.

[0037] In this document, in step S5, the calcination temperature is 650-800℃ and the time is 10-15h. For example, the calcination temperature can be 650℃, 700℃, 730℃, 750℃, 780℃, or 800℃, and the time can be 10h, 11h, 12h, 13h, 14h, or 15h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] If the calcination temperature is too low or the sintering time is too short, the material reaction will be incomplete and the crystal form will be incomplete, thus affecting the material properties. If the calcination temperature is too high or the time is too long, side reactions will occur, thus affecting the material properties.

[0039] Secondly, a high-nickel cathode material is provided, wherein the high-nickel cathode material is prepared by the same method as the high-nickel cathode material.

[0040] Thirdly, a lithium-ion battery is provided, wherein the lithium-ion battery includes the aforementioned high-nickel cathode material.

[0041] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0042] 1. This disclosure describes the preparation of a high-nickel nucleus precursor via crystallization co-precipitation. The chemical formula of the high-nickel nucleus precursor is Ni. x M 1-x (OH)₂ is then used to prepare a carbonate shell containing a dioxime compound using a two-step method, resulting in a core-shell structured high-nickel cathode material precursor. The dioxime compound in the carbonate shell chelates with nickel ions, thereby reducing the nickel content in the carbonate shell. This effectively increases the nitrogen (N) content in the carbonate shell, improving the thermal stability of the high-nickel cathode material and resolving the instability issue caused by excessively high nickel content. Furthermore, the chelation reaction between the dioxime compound and nickel ions allows the carbonate shell to form a low-nickel gradient structure, with the nickel content gradually decreasing away from the core structure.

[0043] 2. This disclosure uses ester solution washing, which avoids the influence of water on the structure of high-nickel cathode material, improves the stability of high-nickel cathode material structure, and thus improves the performance of high-nickel cathode material.

[0044] 3. In this disclosure, an ester solution containing a coating agent is used for washing during the washing process. The ester solution used is the same as the ester solution for dispersing dioxime compounds. On the one hand, the ester solution can further clean the nickel-containing dioxime compounds. On the other hand, the coating agent can not only adhere to the surface of the carbonate shell to form a second coating layer, but also some of the metal elements in the coating agent can be incorporated into the Ni vacancies of the carbonate shell during the calcination process, further improving the coating stability of the carbonate shell.

[0045] 4. The method disclosed herein is simple in process, low in cost, and suitable for industrial production. Attached Figure Description

[0046] Figure 1 This is a scanning electron microscope image of the high-nickel cathode material obtained in Example 1 of this disclosure. Detailed Implementation

[0047] To better illustrate the purpose, technical solutions, and advantages of this disclosure, the following will provide further explanation of this disclosure in conjunction with specific embodiments and accompanying drawings.

[0048] Example 1

[0049] This embodiment provides a method for preparing a high-nickel cathode material, including the following steps:

[0050] S1: Solution preparation: Weigh nickel nitrate, cobalt nitrate and manganese nitrate according to the molar ratio of Ni, Co and Mn as Ni:Co:Mn=80:10:10, dissolve them in deionized water, and prepare nickel solution A with a total metal ion concentration of 2.5mol / L.

[0051] According to the molar ratio of Ni, Co, and Mn as Ni:Co:Mn = 50:20:30, nickel sulfate, cobalt sulfate, and manganese sulfate were weighed and dissolved in deionized water to prepare nickel solution B with a total metal ion concentration of 2.5 mol / L.

[0052] Dimethylglyoxime was dissolved in ethyl acetate to obtain an ester solution containing dimethylglyoxime, wherein the mass fraction of dimethylglyoxime in the ester solution containing dimethylglyoxime was 5 wt%.

[0053] Magnesium oxide was dispersed in ethyl acetate to obtain a first solvent, wherein the mass fraction of magnesium oxide in the first solvent was 1%.

[0054] S2: Under the conditions of stirring speed of 1000 r / min and temperature of 60℃, 2L of nickel solution A is pumped into a reaction vessel containing 2L of ammonia solution with a molar concentration of 0.45 mol / L at a feeding rate of 80 mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.45 mol / L with 25% ammonia solution, and the pH value of the reaction system is adjusted to 11.1 with 5 mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 6 μm to obtain the first solution containing precursor core material.

[0055] S3: Under the conditions of stirring speed of 1000 r / min and temperature of 60℃, 2L of nickel solution B is pumped into the first solution obtained in step S2 at a feeding rate of 80 mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.45 mol / L with 25% ammonia water, and the pH value of the reaction system is adjusted to 9.0 with 1 mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 8 μm to obtain the second solution. The above operation is continued, and an ester solution containing dimethylglyoxime is added at a feeding rate of 50 mL / h. Through co-precipitation reaction, the average particle size is reduced to 10 μm, and the addition of raw materials is stopped to obtain the third solution containing precursor core-shell material.

[0056] S4: Under the conditions of stirring speed of 200 r / min and temperature of 40℃, the third solution obtained in step S3 was aged for 12 h, filtered, and the obtained filter was washed 3 times with the first solvent and dried at 80℃ for 10 h to obtain the core-shell structure precursor.

[0057] S5: Mix the core-shell structure precursor obtained in step S4 with lithium carbonate to obtain a mixture (the molar ratio of lithium to the sum of the molar numbers of nickel, cobalt and manganese in the mixture is 1.06:1). Place the mixture in a muffle furnace and heat it to 550°C at a rate of 4°C / min for 3 hours. Then heat it to 750°C at a rate of 4°C / min for 10 hours. Cool it to room temperature with the furnace to obtain a core-shell structure high-nickel cathode material.

[0058] Example 2

[0059] This embodiment provides a method for preparing a high-nickel cathode material, including the following steps:

[0060] S1: Solution preparation: According to the molar ratio of Ni, Co, and Al of Ni:Co:Al = 85:10:5, weigh nickel nitrate, cobalt nitrate, and manganese nitrate respectively, dissolve them in deionized water, and prepare nickel solution A with a total metal ion concentration of 2.5 mol / L.

[0061] According to the molar ratio of Ni, Co, and Mn as Ni:Co:Mn = 30:45:25, nickel sulfate, cobalt sulfate, and manganese sulfate were weighed and dissolved in deionized water to prepare nickel solution B with a total metal ion concentration of 2.5 mol / L.

[0062] 1,2-Cyclohexanedione dioxime was dissolved in ethyl acetate to obtain an ester solution containing 1,2-cyclohexanedione dioxime, wherein the mass fraction of 1,2-cyclohexanedione dioxime in the ester solution containing 1,2-cyclohexanedione dioxime was 5 wt%.

[0063] Alumina was dispersed in ethyl acetate to obtain a first solvent, wherein the mass fraction of magnesium oxide in the first solvent was 1%.

[0064] S2: Under the conditions of stirring speed of 800 r / min and temperature of 50℃, 2L of nickel solution A is pumped into a reaction vessel containing 2L of ammonia solution with a molar concentration of 0.3mol / L at a feeding rate of 60mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.3mol / L with 26% ammonia solution, and the pH value of the reaction system is adjusted to 11.6 with 5mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 5.5μm to obtain the first solution containing precursor core material.

[0065] S3: Under the conditions of stirring speed of 800 r / min and temperature of 50℃, 2L of nickel solution B is pumped into the first solution obtained in step S2 at a feeding rate of 60 mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.3 mol / L with 26% ammonia water, and the pH value of the reaction system is adjusted to 9.5 with 1 mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 8.5 μm to obtain the second solution. The above operation is continued, and an ester solution containing 1,2-cyclohexanedione dioxime is added at a feeding rate of 55 mL / h. Through co-precipitation reaction, the average particle size is reduced to 11 μm, and the addition of raw materials is stopped to obtain the third solution containing precursor core-shell material.

[0066] S4: Under the conditions of stirring speed of 100 r / min and temperature of 30℃, the third solution obtained in step S3 was aged for 14 h, filtered, and the obtained filtrate was washed 3 times with the first solvent and dried at 80℃ for 10 h to obtain the core-shell structure precursor.

[0067] S5: Mix the core-shell structure precursor obtained in step S4 with lithium carbonate to obtain a mixture (the molar ratio of lithium to the sum of the molar numbers of nickel, cobalt and manganese in the mixture is 1.06:1). Place the mixture in a muffle furnace and heat it to 550°C at a rate of 4°C / min for 3 hours. Then heat it to 650°C at a rate of 4°C / min for 15 hours. Cool it to room temperature with the furnace to obtain a core-shell structure high-nickel cathode material.

[0068] Example 3

[0069] This embodiment provides a method for preparing a high-nickel cathode material, including the following steps:

[0070] S1: Solution preparation: Weigh nickel nitrate, cobalt nitrate and manganese nitrate according to the molar ratio of Ni, Co and Mn as Ni:Co:Mn=90:5:5, dissolve them in deionized water, and prepare nickel solution A with a total metal ion concentration of 2.5mol / L.

[0071] According to the molar ratio of Ni, Co, and Mn as Ni:Co:Mn = 20:60:20, nickel sulfate, cobalt sulfate, and manganese sulfate were weighed and dissolved in deionized water to prepare nickel solution B with a total metal ion concentration of 2.5 mol / L.

[0072] 2,4-Pentanedione dioxime was dissolved in dimethyl carbonate to obtain an ester solution containing 2,4-pentanedione dioxime, wherein the mass fraction of 2,4-pentanedione dioxime in the ester solution containing 2,4-pentanedione dioxime was 5 wt%.

[0073] Magnesium oxide is dispersed in dimethyl carbonate to obtain a first solvent, wherein the mass fraction of magnesium oxide in the first solvent is 1%;

[0074] S2: Under the conditions of stirring speed of 1200 r / min and temperature of 70℃, 2L of nickel solution A is pumped into a reaction vessel containing 2L of ammonia solution with a molar concentration of 0.5mol / L at a feeding rate of 90mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.5mol / L with 25% ammonia solution, and the pH value of the reaction system is adjusted to 11.9 with 5mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 5μm to obtain the first solution containing precursor core material.

[0075] S3: Under the conditions of stirring speed of 1200 r / min and temperature of 70℃, 2L of nickel solution B is pumped into the first solution obtained in step S2 at a feeding rate of 90 mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 0.5 mol / L with 25% ammonia water, and the pH value of the reaction system is adjusted to 9.9 with 1 mol / L sodium hydroxide solution. Through co-precipitation reaction, the average particle size is reduced to 7.5 μm to obtain the second solution. The above operation is continued, and an ester solution containing 2,4-pentanedione dioxime is added at a feeding rate of 50 mL / h. Through co-precipitation reaction, the average particle size is reduced to 9.6 μm, and the addition of raw materials is stopped to obtain the third solution containing precursor core-shell material.

[0076] S4: Under the conditions of stirring speed of 250 r / min and temperature of 45℃, the third solution obtained in step S3 was aged for 10 h, filtered, and the obtained filter material was washed 3 times with the first solvent and dried at 80℃ for 10 h to obtain the core-shell structure precursor.

[0077] S5: Mix the core-shell structure precursor obtained in step S4 with lithium carbonate to obtain a mixture (the molar ratio of lithium to the sum of the molar numbers of nickel, cobalt and manganese in the mixture is 1.06:1). Place the mixture in a muffle furnace and heat it to 550°C at a rate of 4°C / min for 3 hours. Then heat it to 800°C at a rate of 4°C / min for 12 hours. Cool it to room temperature with the furnace to obtain a core-shell structure high-nickel cathode material.

[0078] Example 4

[0079] This embodiment provides a method for preparing a high-nickel cathode material. The only difference between this embodiment and Example 1 is that the mass fraction of dimethylglyoxime in the ester solution containing dimethylglyoxime is 2 wt%.

[0080] Example 5

[0081] This embodiment provides a method for preparing a high-nickel cathode material. The only difference between this embodiment and Example 1 is that the mass fraction of dimethylglyoxime in the ester solution containing dimethylglyoxime is 7 wt%.

[0082] Example 6

[0083] This embodiment provides a method for preparing a high-nickel cathode material. The only difference between this embodiment and Embodiment 1 is that in step S3, the feeding rate of the ester solution containing dimethylglyoxime is 40 mL / h.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a high-nickel cathode material. The only difference between this comparative example and Example 1 is that, in step S3, an ester solution containing dimethylglyoxime is not added; and in step S3, deionization is used for washing.

[0086] Comparative Example 2

[0087] This comparative example provides a method for preparing a high-nickel cathode material. The only difference between this comparative example and Example 1 is that, in step S3, the average particle size of the particles in the second solution is 9 μm.

[0088] Comparative Example 3

[0089] This comparative example provides a method for preparing a high-nickel cathode material. The only difference between this comparative example and Example 1 is that, in step S3, the average particle size of the particles in the second solution is 7 μm.

[0090] Comparative Example 4

[0091] This comparative example provides a method for preparing a high-nickel cathode material. The only difference between this comparative example and Example 1 is that dimethylglyoxime is dissolved in acetone to obtain a ketone solution containing dimethylglyoxime, wherein the mass fraction of dimethylglyoxime in the ketone solution containing dimethylglyoxime is 5 wt%.

[0092] Comparative Example 5

[0093] This comparative example provides a method for preparing a high-nickel cathode material. The only difference between this comparative example and Example 1 is that dimethylglyoxime is dissolved in ethanol to obtain an alcoholic solution containing dimethylglyoxime, wherein the mass fraction of dimethylglyoxime in the alcoholic solution containing dimethylglyoxime is 5 wt%.

[0094] Example 1

[0095] The performance of the high-nickel cathode materials obtained in each embodiment and comparative example was tested.

[0096] (1) The Ni, Co, and Mn content of the high-nickel cathode materials obtained in each embodiment and comparative example was tested using an inductively coupled plasma spectrometer (ICP).

[0097] (2) The high-nickel cathode materials obtained in the above embodiments and comparative examples are used as cathode active materials and are respectively prepared into cathode sheets and lithium-ion batteries;

[0098] Positive electrode sheet: Using N-methylpyrrolidone as solvent, the positive electrode active material is mixed evenly with acetylene black and PVDF in a mass ratio of 92.3:4:3.7, coated onto aluminum foil, and dried at 80°C for 6 hours to obtain the positive electrode sheet.

[0099] Lithium-ion battery: The negative electrode sheet is made of graphite as the negative electrode active material, the separator is polypropylene film, and the electrolyte is 1M LiPF6-ethylene carbonate / dimethyl carbonate (1:1, v / v), which are assembled into a lithium-ion battery.

[0100] The obtained lithium-ion batteries were subjected to elemental content and cycle performance tests, and the test results are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] As shown in Table 1, the lithium batteries prepared using the high-nickel cathode materials in Examples 1-6 have a cycle efficiency of up to 93% after 300 cycles at room temperature and 1C.

[0105] Compared with Example 1, Comparative Example 1 did not add an ester solution containing dimethylglyoxime during the preparation process and used deionized water for washing. The resulting high-nickel cathode material had a higher nickel content, and the cycle efficiency of the lithium battery was significantly reduced.

[0106] Compared with Example 1, the average particle size of the particles in the second solution in Comparative Examples 2 and 3 was too small or too large, which led to an increase in the nickel content of the high-nickel cathode material, and consequently a decrease in the performance of the resulting lithium battery.

[0107] Compared with Example 1, the solvents used to dissolve dimethyl ethyl ketone contaminants in Comparative Examples 4-5 were different. The nickel content of the resulting high-nickel cathode materials did not change significantly, but the different solvents affected the removal of residual alkali in the high-nickel cathode materials during subsequent washing, which in turn led to a significant decrease in the cycle performance of the resulting lithium batteries.

[0108] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this disclosure and not to limit the scope of protection of this disclosure. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the substance and scope of the technical solutions of this disclosure.

Claims

1. A method for preparing a high-nickel cathode material, characterized in that, Includes the following steps: S1: According to the chemical formula Ni x M 1-x Weigh out Ni salt and M salt according to their stoichiometric ratio and dissolve them in water to prepare nickel solution A; according to the chemical formula Ni y N 1-y The stoichiometric ratio of CO3 is used to weigh Ni salt and N salt and dissolve them in water to prepare nickel solution B; wherein, 0.5 < x < 1, 0.2 ≤ y ≤ 0.5, and M and N are each independently selected from at least one of Co, Mn, and Al; S2: Add nickel solution A and complexing agent to the reaction vessel, adjust the pH value of the reaction with hydroxide solution, stir to carry out co-precipitation reaction, and obtain the first solution with an average particle size of 5-6 μm; S3: Nickel solution B and the complexing agent are added concurrently to the first solution obtained in step S2 under stirring. Through co-precipitation, when the average particle size reaches 7.5–8.5 μm, a second solution is obtained. Nickel solution B, the complexing agent, and an ester solution containing a dioxime compound are added concurrently to the second solution under stirring. Through co-precipitation, when the average particle size reaches 9.5–11 μm, the addition of raw materials is stopped, resulting in a third solution. The pH of the co-precipitation reaction is adjusted using a carbonate solution. S4: The third solution obtained in step S3 is stirred and aged, filtered, the solid obtained by filtration is washed with an ester solution containing a coating agent, and dried to obtain a core-shell structure precursor; S5: Mix the core-shell structure precursor obtained in step S4 with a lithium source and calcine to obtain a core-shell structure high-nickel cathode material.

2. The preparation method according to claim 1, characterized in that, The method for preparing the ester solution containing the dioxime compound is as follows: dissolving the dioxime compound in an ester solvent; the dioxime compound is at least one selected from diacetone oxime, 2,4-pentanedione dioxime, and 1,2-cyclohexanedione dioxime; the ester solvent is at least one selected from ethyl acetate, propyl acetate, and dimethyl carbonate.

3. The preparation method according to claim 1, characterized in that, The concentration of the dioxime compound in the ester solution containing the dioxime compound is 2-7 wt%.

4. The preparation method according to claim 1, characterized in that, In step S4, the coating agent is at least one of aluminum oxide and magnesium oxide.

5. The preparation method according to claim 1, characterized in that, In step S4, the ester in the coating agent-containing ester solution is at least one of ethyl acetate, propyl acetate, and dimethyl carbonate.

6. The preparation method according to claim 1, characterized in that, In step S1, the Ni salt, M salt, and N salt are independently any one or a mixture of at least two of sulfate, nitrate, chloride, or acetate.

7. The preparation method according to claim 1, characterized in that, In step S5, the lithium source is at least one of lithium hydroxide, lithium carbonate, or lithium oxalate.

8. The preparation method according to claim 1, characterized in that, In steps S2 and S3, the complexing agent is either ammonia or an ammonium salt solution.

9. The preparation method according to claim 1, characterized in that, In steps S2 and S3, the reaction temperature is independently selected from 50-70°C.

10. The preparation method according to claim 1, characterized in that, In steps S2 and S3, the stirring speed is independently selected from 800 to 1200 r / min.

11. The preparation method according to claim 1, characterized in that, In step S2, the pH of the reaction is 11-12.

12. The preparation method according to claim 1, characterized in that, In step S3, the pH of the reaction is 9-10.

13. The preparation method according to claim 1, characterized in that, In step S4, the stirring speed is 100-250 r / min; and / or the aging temperature is 30-45℃, and the aging time is 10-14 h; and / or the drying temperature is 50-100℃, and the drying time is 5-15 h.

14. The preparation method according to claim 1, characterized in that, In step S5, the calcination temperature is 650-800℃ and the time is 10-15h.

15. A high-nickel cathode material, characterized in that, It is prepared by the method of any one of claims 1-14 for the preparation of high-nickel cathode material.

16. A lithium-ion battery, characterized in that, The lithium-ion battery contains the high-nickel cathode material as described in claim 14.

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