Cerium modified ternary precursor as well as preparation method and application thereof

Abstract

The invention provides a cerium-modified ternary precursor and a preparation method and application thereof, the preparation method comprises the following steps: (1) injecting a nickel-cobalt-manganese mixed salt solution, a complexing agent and a precipitator into a base solution in a parallel flow manner, and carrying out a co-precipitation reaction to obtain a seed crystal; (2) placing a seed crystal in a base solution, injecting a cerium-containing nickel-cobalt-manganese mixed salt solution, a complexing agent and a precipitant into the base solution in a parallel flow manner, and carrying out a co-precipitation reaction to obtain a mixed solution containing a half-step precursor; and (3) injecting a cerium salt solution, a complexing agent and a precipitator into the mixed solution containing the half-step precursor, and carrying out a co-precipitation reaction to obtain the cerium modified ternary precursor. According to the preparation method, the positive electrode precursor is modified by doping and coating cerium at the same time, so that the defect of cation mixing is overcome, the reaction between the prepared positive electrode material and an electrolyte is hindered, the dissolution of metal ions is prevented, the stability and the cycle performance of the positive electrode material are improved from multiple aspects, and the purpose of simplifying the preparation steps is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials and relates to a cerium-modified ternary precursor and a preparation method and application thereof. Background Art

[0002] The environmental pollution problem caused by the consumption of fossil fuels has intensified, leading to a growing demand for new energy. Lithium-ion batteries have the characteristics of high energy density, low self-discharge rate and long cycle life, and are widely used in electric vehicles, energy storage and portable electronic products. The positive electrode material is one of the key factors that determine the performance of lithium-ion batteries. Nickel-cobalt-manganese (NCM) high-nickel ternary positive electrode materials have always been the core of lithium battery positive electrode materials due to their high energy density. However, NCM high-nickel ternary materials still have the disadvantages of poor cycle performance and thermal stability. By modifying the structure and components of NCM high-nickel ternary precursors, its shortcomings can be improved and its market utilization can be further improved.

[0003] CN118771488A discloses a method for preparing a cobalt-free precursor doped with cerium and bismuth, by adding cerium salt to the nickel salt of the raw material and bismuth to the manganese salt instead of cobalt salt, while passing the manganese-containing solution into the nickel-containing solution, a precipitant solution and a complexing agent solution are passed to perform a coprecipitation reaction, and a cobalt-free precursor with a gradient distribution of nickel and manganese is obtained. The doping of cerium and bismuth plays a role of fluxing in the later sintering process of the positive electrode material, making the material easier to sinter into a single crystal, and reducing the situation where the manganese inside the material is not burned through and an impurity phase appears. However, this method does not utilize the influence of the doping element cerium on the internal structure of the positive electrode material during the charging and discharging process.

[0004] CN117776288A discloses a method for preparing a sodium ion precursor coated with zinc hydroxystannate. By adding zinc oxide, water and a precursor matrix to a tin solution dissolved in an alkaline solution, a sodium ion battery precursor coated with zinc hydroxystannate is obtained by reaction. In the subsequent calcination process to prepare sodium ions, zinc hydroxystannate can be in-situ oxidized into zinc oxide and tin oxide to form a coating layer to resist the erosion of the electrolyte and induce the formation of a sodium phase deficiency. Not only does it improve the kinetic properties of the entire material particles, it also improves the rate performance and cycle performance of the battery. However, in order to form a coating layer structure in this method, more metals are used, and the precursor is also doped with other elements in the scheme, which makes the material composition complex, the preparation process cumbersome, and the cost high. Summary of the invention

[0005] The purpose of the present invention is to provide a cerium-modified ternary precursor and a preparation method and application thereof. The present invention modifies the positive electrode precursor by using cerium for simultaneous doping and coating, thereby improving the disadvantages of cation mixing and hindering the reaction between the prepared positive electrode material and the electrolyte, preventing the dissolution of metal ions, and improving the stability and cycle performance of the positive electrode material from many aspects, and achieving the purpose of streamlining the preparation steps.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a cerium-modified ternary precursor, the preparation method comprising the following steps:

[0008] (1) injecting a nickel-cobalt-manganese mixed salt solution, a first complexing agent and a first precipitating agent into a first bottom solution in parallel, and performing a one-step coprecipitation reaction to obtain a seed crystal;

[0009] (2) placing the seed crystal in a second bottom liquid, and injecting a cerium-containing nickel-cobalt-manganese mixed salt solution, a second complexing agent, and a second precipitant into the second bottom liquid in parallel, and performing a two-step coprecipitation reaction to obtain a mixed solution containing a half-step precursor;

[0010] (3) Injecting the cerium salt solution, the third complexing agent and the third precipitating agent into the mixed solution containing the half-step precursor, and performing a three-step co-precipitation reaction to obtain the cerium-modified ternary precursor.

[0011] The present invention introduces cerium as both a doping ion and a coating layer into a ternary positive electrode precursor by adjusting the coprecipitation method and adding materials in each step, thereby improving the structural stability of the ternary positive electrode material, reducing the side reaction at the electrode / electrolyte interface, and inhibiting the dissolution of metal ions, thereby more effectively improving the thermal stability and cycle performance of the positive electrode material. The present invention uses the same metal element for two modifications, reducing the material preparation cost and process steps, and saving preparation time.

[0012] Preferably, the solute in the nickel-cobalt-manganese mixed salt solution in step (1) includes nickel salt, manganese salt and cobalt salt.

[0013] Preferably, the molar ratio of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese mixed salt solution in step (1) is (0.8-0.98):(0.01-0.2):(0.01-0.2), for example: 0.8:0.1:0.1, 0.85:0.05:0.1, 0.95:0.02:0.03, 0.9:0.08:0.02 or 0.98:0.01:0.01, not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0014] Preferably, the total mass concentration of nickel salt, manganese salt and cobalt salt in the nickel-cobalt-manganese mixed salt solution in step (1) is 100 g / L to 200 g / L, for example: 100 g / L, 120 g / L, 150 g / L, 180 g / L or 200 g / L, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, in step (1), the first complexing agent comprises aqueous ammonia.

[0016] Preferably, the mass concentration of the ammonia water is 10% to 20%, for example, 10%, 12%, 15%, 18% or 20%, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, in step (1), the first precipitant comprises sodium hydroxide solution.

[0018] Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%, for example, 25%, 28%, 30%, 32% or 35%, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, in step (1), the first base solution contains a first complexing agent and a first precipitating agent.

[0020] Preferably, the pH of the first base solution in step (1) is 10 to 11.5, for example, 10, 10.2, 10.5, 11 or 11.5, etc., but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0021] Preferably, the concentration of the first complexing agent in the first base solution in step (1) is 4 g / L to 12 g / L, for example, 4 g / L, 6 g / L, 8 g / L, 10 g / L or 12 g / L, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the temperature of the one-step coprecipitation reaction in step (1) is 50°C to 60°C, for example, 50°C, 52°C, 55°C, 58°C or 60°C, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, during the one-step coprecipitation reaction in step (1), the concentration of the first complexing agent is 3 g / L to 5 g / L, for example, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the pH of the one-step coprecipitation reaction in step (1) is 9 to 11, for example, 9, 9.5, 10, 10.5 or 11, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the stirring speed of the one-step coprecipitation reaction in step (1) is 300 rpm to 400 rpm, for example, 300 rpm, 320 rpm, 350 rpm, 380 rpm or 400 rpm, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the median particle size D50 of the seed crystal in step (1) is 3 μm to 5 μm, for example, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the second base liquid in step (2) contains a second complexing agent and a second precipitating agent.

[0028] Preferably, the pH of the second base solution in step (2) is 10 to 11.5, for example, 10, 10.2, 10.5, 11 or 11.5, etc., but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0029] Preferably, the concentration of the second complexing agent in the second base liquid in step (2) is 4 g / L to 12 g / L, for example, 4 g / L, 6 g / L, 8 g / L, 10 g / L or 12 g / L, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the solutes in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) include nickel salt, manganese salt, cobalt salt and cerium salt.

[0031] Preferably, the molar ratio of nickel ions, cobalt ions and manganese ions in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is (0.8-0.98):(0.01-0.2):(0.01-0.2), for example: 0.8:0.1:0.1, 0.85:0.05:0.1, 0.95:0.02:0.03, 0.9:0.08:0.02 or 0.98:0.01:0.01, not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the total mass concentration of nickel salt, manganese salt and cobalt salt in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is 100 g / L to 200 g / L, for example: 100 g / L, 120 g / L, 150 g / L, 180 g / L or 200 g / L, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the molar concentration of cerium ions in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is 0.1 mol / L to 0.3 mol / L, for example: 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L, etc.

[0034] Preferably, in step (2), the second complexing agent comprises aqueous ammonia.

[0035] Preferably, the mass concentration of the ammonia water is 10% to 30%, for example, 10%, 15%, 20%, 25% or 30%, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, in step (2), the second precipitant comprises sodium hydroxide solution.

[0037] Preferably, the mass concentration of the sodium hydroxide solution is 10% to 30%, for example, 10%, 15%, 20%, 25% or 30%, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the temperature of the two-step coprecipitation reaction in step (2) is 50°C to 60°C, for example, 50°C, 52°C, 55°C, 58°C or 60°C, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, during the two-step coprecipitation reaction in step (2), the concentration of the second complexing agent is 4 to 6 g / L, for example, 4, 4.5, 5, 5.5 or 6, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the pH of the two-step coprecipitation reaction in step (2) is 9 to 12, for example, 9, 9.5, 10, 11 or 12, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, during the two-step co-precipitation reaction in step (2), the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 10 L / h to 50 L / h, for example: 10 L / h, 20 L / h, 30 L / h, 40 L / h or 50 L / h, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the stirring speed of the two-step coprecipitation reaction in step (2) is 250 rpm to 350 rpm, for example: 250 rpm, 280 rpm, 300 rpm, 320 rpm or 350 rpm, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the median particle size D50 of the half-step precursor in step (2) is 8 μm to 13 μm, for example 8 μm, 9 μm, 10 μm, 11 μm, 12 μm or 13 μm, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the mass concentration of the cerium salt in the cerium salt solution in step (3) is 2 g / L to 15 g / L, for example, 2 g / L, 5 g / L, 8 g / L, 10 g / L or 15 g / L, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the third complexing agent in step (3) comprises aqueous ammonia.

[0046] Preferably, the mass concentration of the ammonia water is 10% to 20%, for example, 10%, 12%, 15%, 18% or 20%, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, the third precipitant in step (3) comprises sodium hydroxide solution.

[0048] Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%, for example, 25%, 28%, 30%, 32% or 35%, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the temperature of the three-step co-precipitation reaction in step (3) is 40°C to 60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, during the three-step coprecipitation reaction in step (3), the concentration of the third complexing agent is 2 to 4 g / L, for example, 2 g / L, 2.5 g / L, 3 g / L, 4.5 g / L or 4 g / L, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the pH of the three-step coprecipitation reaction in step (3) is 10-11, for example: 10, 10.2, 10.5, 10.8 or 11, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, during the three-step co-precipitation reaction in step (3), the flow rate of the cerium salt solution is 80 mL / min to 180 mL / min, for example, 80 mL / min, 90 mL / min, 100 mL / min, 120 mL / min, 150 mL / min or 180 mL / min, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] Preferably, the stirring speed of the three-step co-precipitation reaction in step (3) is 130 rpm to 160 rpm, for example: 130 rpm, 135 rpm, 140 rpm, 150 rpm or 160 rpm, etc., not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the median particle size D50 of the cerium-modified ternary precursor in step (3) is 10 μm to 15 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc., not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] In a second aspect, the present invention provides a cerium-modified ternary precursor, wherein the cerium-modified ternary precursor is prepared by the preparation method described in the first aspect.

[0056] The Ce doped in the cerium-modified ternary precursor of the present invention contains Ce 3+ and Ce 4+ Two valence states, which can be converted into each other in chemical processes, and Ce 4+ It has strong oxidizing properties and can 2+ Oxidized to Ni 3+ , reducing the Li + / Ni 2+ The mixing degree can improve the cycle efficiency of the positive electrode material. There are a large number of oxygen vacancies, which can effectively capture the unstable oxygen-containing species (such as O 2- , O- and O2 2- ), reducing the release of oxygen. The coated CeO2 layer (in the process of preparing the positive electrode material, cerium hydroxide is oxidized to cerium dioxide) reduces the reaction between the positive electrode material and the electrolyte, reduces the phase change and the degree of structural damage of the positive electrode material, and improves the stability and safety of the material.

[0057] In a third aspect, the present invention provides a cerium-modified ternary positive electrode material, wherein the cerium-modified ternary positive electrode material is prepared by mixing and sintering the cerium-modified ternary precursor as described in the second aspect with a lithium source.

[0058] Preferably, the lithium source comprises lithium hydroxide and / or lithium carbonate.

[0059] In a fourth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the cerium-modified ternary positive electrode material as described in the third aspect.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The present invention introduces cerium into the ternary positive electrode precursor as both an impurity ion and a coating layer, thereby improving the structural stability of the ternary positive electrode material, reducing side reactions at the electrode / electrolyte interface, and inhibiting the dissolution of metal ions, thereby more effectively improving the thermal stability and cycle performance of the positive electrode material.

[0062] (2) The method described in the present invention is applicable to various high-nickel ternary positive electrode materials, and has a good discharge specific capacity at 0.1C. The capacity retention rate of the lithium-ion battery made from the positive electrode material prepared from the cerium-modified ternary precursor can reach more than 80.25% after 50 cycles at 1C. By adjusting the preparation conditions, the capacity retention rate can reach more than 86.17% after 50 cycles at 1C. DETAILED DESCRIPTION

[0063] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0064] Example 1

[0065] This embodiment provides a cerium-modified ternary positive electrode precursor, and the cerium-modified ternary positive electrode precursor is prepared by the following method:

[0066] (1) According to the Ni:Co:Mn molar ratio of 0.97:0.01:0.02, a nickel cobalt manganese sulfate mixed salt solution was prepared with a total concentration of 150 g / L. A portion of the nickel cobalt manganese sulfate mixed salt solution was added with cerium sulfate to obtain a cerium-containing nickel cobalt manganese mixed salt solution with a cerium molar concentration of 0.1 mol / L. A cerium sulfate solution with a mass concentration of 2 g / L was prepared, with sodium hydroxide solution as a precipitant with a mass concentration of 25%, and ammonia water as a complexing agent with a mass concentration of 20%. 150 L of pure water and a certain amount of NaOH solution and ammonia water were added to two 300 L reactors respectively, and 0.8 m 3 / h, nitrogen is introduced into the base liquid, stirred at a speed of 200 rpm to make it uniformly mixed, and then the temperature is raised to 40°C, the pH is controlled to be 11-11.5, and the ammonia concentration is controlled to be 6g / L-8g / L to obtain a base liquid (the first base liquid is the same as the second base liquid);

[0067] (2) injecting a nickel-cobalt-manganese sulfate mixed salt solution, a sodium hydroxide solution and an ammonia solution into the first bottom solution in parallel, and performing a one-step coprecipitation reaction at 50° C. and a stirring speed of 300 rpm, controlling the pH to 9 and the complexing agent concentration to 3 g / L, until the median particle size D50 of the solid material in the system is 3 μm, washing to obtain seed crystals;

[0068] (3) placing the seed crystal in the second bottom liquid, and injecting the cerium-containing nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution and ammonia water into the second bottom liquid in parallel, the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 10 L / h, at 55° C., at a stirring speed of 300 rpm, the pH is controlled to be 9.5, the complexing agent concentration is 4 g / L, and a two-step coprecipitation reaction is performed. When the median particle size D50 of the solid material in the system is 9 μm, the feeding is stopped to obtain a mixed solution containing a half-step precursor;

[0069] (4) Injecting cerium sulfate solution, sodium hydroxide solution and ammonia water into the mixed solution containing the half-step precursor at a flow rate of 80 mL / min, at 50° C. and a stirring speed of 150 rpm, controlling the pH to 10.5 and the complexing agent concentration to 2 g / L, and performing a two-step co-precipitation reaction. When the median particle size D50 of the solid material in the system is 11 μm, stop feeding to obtain the cerium-modified ternary positive electrode precursor.

[0070] Example 2

[0071] This embodiment provides a cerium-modified ternary positive electrode precursor, and the cerium-modified ternary positive electrode precursor is prepared by the following method:

[0072] (1) According to the molar ratio of Ni:Co:Mn of 0.90:0.03:0.07, a nickel-cobalt-manganese sulfate mixed salt solution was prepared with a total concentration of 150 g / L. A portion of the nickel-cobalt-manganese sulfate mixed salt solution was added with cerium sulfate to obtain a cerium-containing nickel-cobalt-manganese mixed salt solution with a molar concentration of 0.3 mol / L, and a cerium sulfate solution with a mass concentration of 6 g / L was prepared. Sodium hydroxide solution was used as a precipitant with a mass concentration of 25%. Ammonia water was used as a complexing agent with a mass concentration of 20%. 150 L of pure water and a certain amount of NaOH solution and ammonia water were added to two 300 L reactors respectively, and 0.8 m 3 / h, nitrogen is introduced into the base liquid, stirred at a speed of 200 rpm to make it uniformly mixed, and then the temperature is raised to 40°C, the pH is controlled to be 11-11.5, and the ammonia concentration is controlled to be 6g / L-8g / L to obtain a base liquid (the first base liquid is the same as the second base liquid);

[0073] (2) injecting a nickel-cobalt-manganese sulfate mixed salt solution, a sodium hydroxide solution and an ammonia solution into the first bottom solution in parallel, and performing a one-step coprecipitation reaction at 55° C. and a stirring speed of 350 rpm, controlling the pH to 10 and the complexing agent concentration to 4 g / L, until the median particle size D50 of the solid material in the system is 4 μm, washing to obtain seed crystals;

[0074] (3) placing the seed crystal in the second bottom liquid, and injecting the cerium-containing nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution and ammonia water into the second bottom liquid in parallel, the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 25 L / h, at 55° C., at a stirring speed of 300 rpm, the pH is controlled to be 9.5, the concentration of the complexing agent is 5 g / L, and a two-step coprecipitation reaction is performed. When the median particle size D50 of the solid material in the system is 9 μm, the feeding is stopped to obtain a mixed solution containing a half-step precursor;

[0075] (4) Injecting cerium sulfate solution, sodium hydroxide solution and ammonia water into the mixed solution containing the half-step precursor in parallel, the flow rate of the cerium sulfate solution is 150 mL / min, at 60°C, a stirring speed of 130 rpm, the pH is controlled to be 10, the complexing agent concentration is 3 g / L, and a two-step co-precipitation reaction is carried out. When the median particle size D50 of the solid material in the system is 13 μm, the feeding is stopped to obtain the cerium-modified ternary positive electrode precursor.

[0076] Example 3

[0077] This embodiment provides a cerium-modified ternary positive electrode precursor, and the cerium-modified ternary positive electrode precursor is prepared by the following method:

[0078] (1) A nickel-cobalt-manganese sulfate mixed salt solution was prepared according to the molar ratio of Ni:Co:Mn of 0.80:0.1:0.1, with a total concentration of 150 g / L. A portion of the nickel-cobalt-manganese sulfate mixed salt solution was added with cerium sulfate to obtain a cerium-containing nickel-cobalt-manganese mixed salt solution with a molar concentration of 0.2 mol / L of cerium, and a cerium sulfate solution with a mass concentration of 10 g / L was prepared. Sodium hydroxide solution was used as a precipitant with a mass concentration of 35%. Ammonia water was used as a complexing agent with a mass concentration of 20%. 150 L of pure water and a certain amount of NaOH solution and ammonia water were added to two 300 L reactors respectively, and 0.8 m 3 / h, nitrogen is introduced into the base liquid, stirred at a speed of 200 rpm to make it uniformly mixed, and then the temperature is raised to 40°C, the pH is controlled to be 11-11.5, and the ammonia concentration is controlled to be 6g / L-8g / L to obtain a base liquid (the first base liquid is the same as the second base liquid);

[0079] (2) injecting a nickel-cobalt-manganese sulfate mixed salt solution, a sodium hydroxide solution and an ammonia solution into the first bottom solution in parallel, and performing a one-step coprecipitation reaction at 60° C. and a stirring speed of 300 rpm, controlling the pH to 11 and the complexing agent concentration to 5 g / L, until the median particle size D50 of the solid material in the system is 4 μm, washing to obtain seed crystals;

[0080] (3) placing the seed crystal in the second bottom liquid, and injecting the cerium-containing nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution and ammonia water into the second bottom liquid in parallel, the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 40 L / h, at 60° C., 300 rpm stirring speed, controlling the pH to 11, the complexing agent concentration to 6 g / L, and performing a two-step coprecipitation reaction. When the median particle size D50 of the solid material in the system is 13 μm, stop feeding to obtain a mixed solution containing a half-step precursor;

[0081] (4) Injecting cerium sulfate solution, sodium hydroxide solution and ammonia water into the mixed solution containing the half-step precursor in parallel, the flow rate of the cerium sulfate solution is 150 mL / min, and the pH is controlled to be 10 and the concentration of the complexing agent is 4 g / L at 60° C. and a stirring speed of 130 rpm. A two-step co-precipitation reaction is performed. When the median particle size D50 of the solid material in the system is 15 μm, the feeding is stopped to obtain the cerium-modified ternary positive electrode precursor.

[0082] Example 4

[0083] The only difference between this embodiment and embodiment 1 is that the molar concentration of cerium in the nickel-cobalt-manganese mixed salt solution containing cerium in step (3) is 0.01 mol %, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0084] Example 5

[0085] The only difference between this embodiment and embodiment 1 is that the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (3) is 0.5 mol %, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0086] Example 6

[0087] The only difference between this embodiment and embodiment 1 is that the mass concentration of cerium in the cerium salt solution in step (4) is 1 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0088] Example 7

[0089] The only difference between this embodiment and embodiment 1 is that the mass concentration of cerium in the cerium salt solution in step (4) is 20 g / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0090] Comparative Example 1

[0091] The only difference between this comparative example and Example 1 is that step (3) uses a nickel-cobalt-manganese mixed salt solution without adding cerium, and the other conditions and parameters are exactly the same as those in Example 1.

[0092] Comparative Example 2

[0093] The only difference between this comparative example and Example 1 is that no cerium salt solution is added in step (4), and the other conditions and parameters are exactly the same as those in Example 1.

[0094] Comparative Example 3

[0095] The only difference between this comparative example and Example 1 is that no cerium is added in step (3) and step (4), that is, a ternary precursor without cerium is prepared, and the other conditions and parameters are exactly the same as those in Example 1.

[0096] Performance Test:

[0097] Take the cerium-modified ternary precursor obtained in Example 1-7 and Comparative Example 1-3, wash, dry, sieve, remove iron, mix with lithium hydroxide at a molar ratio of 1.05:1, and calcine in an oxygen atmosphere at 900°C for 14 hours to obtain a cerium-doped and coated modified ternary lithium positive electrode material. The obtained ternary positive electrode material, polyvinylidene fluoride, and acetylene black are mixed uniformly at a mass ratio of 8:1:1, and then made into a slurry and evenly applied on aluminum foil, placed in an oven at 110°C for 14 hours for drying, and then pressed and cut into positive electrode sheets, with lithium sheets as negative electrodes and lithium hexafluorophosphate as electrolyte solution, assembled into CR2032 button batteries, and the electrochemical performance thereof is tested at 2.8-4.3V. The test results are shown in Table 1:

[0098] Table 1

[0099] Discharge capacity at 0.1C (mAh / g) Capacity retention after 50 cycles at 1C (%) Example 1 208.52 91.71 Example 2 200.37 88.43 Example 3 195.82 86.17 Example 4 180.23 86.32 Example 5 195.34 89.57 Example 6 197.28 80.25 Example 7 185.62 87.86 Comparative Example 1 180.38 88.45 Comparative Example 2 198.27 78.48 Comparative Example 3 170.92 75.64

[0100] As can be seen from Table 1, from Examples 1-7, the method of the present invention is applicable to various high-nickel ternary positive electrode materials, has a good discharge specific capacity at 0.1C, and the capacity retention rate of the lithium-ion battery prepared from the positive electrode material prepared from the cerium-modified ternary precursor after 50 cycles at 1C can reach more than 80.25%. By adjusting the preparation conditions, the capacity retention rate after 50 cycles at 1C can reach more than 86.17%.

[0101] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the cerium-modified ternary precursor of the present invention, the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution will affect its performance. The molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution is controlled at 0.1 mol / L to 0.3 mol / L, and the performance of the cerium-modified ternary precursor is better. If the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution is too low, the degree of cation mixing of the subsequently prepared lithium-ion positive electrode material will increase, thereby reducing the charge and discharge efficiency of the material. If the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution is too high, the electron transfer rate will be reduced, thereby reducing the electrochemical performance of the material.

[0102] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation of the cerium-modified ternary precursor of the present invention, the mass concentration of cerium in the cerium salt solution will affect its performance. When the mass concentration of cerium in the cerium salt solution is controlled at 2g / L to 15g / L, the performance of the cerium-modified ternary precursor is better. If the mass concentration of cerium in the cerium salt solution is too low, the cerium oxide layer cannot completely cover the ternary particles, thereby reducing the structural stability of the subsequently prepared positive electrode material. If the mass concentration of cerium in the cerium salt solution is too high, the thickness of the formed CeO2 layer increases and the electron transfer rate decreases.

[0103] From the comparison between Example 1 and Comparative Example 1, it can be seen that the Ce doped in the cerium-modified ternary precursor of the present invention contains Ce 3+ and Ce 4+ Two valence states, which can be converted into each other in chemical processes, and Ce 4+ It has strong oxidizing properties and can 2+ Oxidized to Ni 3+ , reducing the Li + / Ni 2+ The mixing degree can improve the cycle efficiency of the positive electrode material. There are a large number of oxygen vacancies, which can effectively capture the unstable oxygen-containing species (such as O 2- , O- and O2 2- ), reducing the release of oxygen.

[0104] By comparing Example 1 and Comparative Example 2, it can be seen that the coated CeO2 layer (cerium hydroxide is oxidized to cerium dioxide during the preparation of the positive electrode material) reduces the reaction between the positive electrode material and the electrolyte, reduces the phase change and the structural damage of the positive electrode material, and improves the stability and safety of the material.

[0105] By comparing Example 1 with Comparative Example 3, it can be seen that the present invention introduces cerium as both a doping ion and a coating layer into the ternary positive electrode precursor by adjusting the coprecipitation method and the materials added in each step, thereby improving the structural stability of the ternary positive electrode material, reducing the side reactions at the electrode / electrolyte interface, and inhibiting the dissolution of metal ions. This more effectively improves the thermal stability and cycle performance of the positive electrode material.

[0106] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a cerium-modified ternary precursor, characterized in that: The preparation method comprises the following steps: (1) injecting a nickel-cobalt-manganese mixed salt solution, a first complexing agent and a first precipitating agent into a first bottom solution in parallel, and performing a one-step coprecipitation reaction to obtain a seed crystal; (2) placing the seed crystal in a second bottom liquid, and injecting a cerium-containing nickel-cobalt-manganese mixed salt solution, a second complexing agent, and a second precipitant into the second bottom liquid in parallel, and performing a two-step coprecipitation reaction to obtain a mixed solution containing a half-step precursor; (3) Injecting a cerium salt solution, a third complexing agent and a third precipitating agent into a mixed solution containing the half-step precursor, and performing a three-step co-precipitation reaction to obtain the cerium-modified ternary precursor.

2. The preparation method according to claim 1, characterized in that The solute in the nickel-cobalt-manganese mixed salt solution of step (1) includes nickel salt, manganese salt and cobalt salt; Preferably, the molar ratio of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese mixed salt solution of step (1) is (0.8-0.98):(0.01-0.2):(0.01-0.2); Preferably, the total mass concentration of nickel salt, manganese salt and cobalt salt in the nickel-cobalt-manganese mixed salt solution in step (1) is 100 g / L to 200 g / L; Preferably, in step (1), the first complexing agent comprises aqueous ammonia; Preferably, the mass concentration of the ammonia water is 10% to 20%; Preferably, in step (1), the first precipitant comprises a sodium hydroxide solution; Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%; Preferably, in step (1), the first base solution contains a first complexing agent and a first precipitating agent; Preferably, the pH of the first base solution in step (1) is 10 to 11.5; Preferably, the concentration of the first complexing agent in the first base solution in step (1) is 4 g / L to 12 g / L.

3. The preparation method according to claim 1 or 2, characterized in that: The temperature of the one-step coprecipitation reaction in step (1) is 50° C. to 60° C.; Preferably, during the one-step coprecipitation reaction in step (1), the concentration of the first complexing agent is 3 to 5 g / L; Preferably, the pH of the one-step coprecipitation reaction in step (1) is 9 to 11; Preferably, the stirring speed of the one-step coprecipitation reaction in step (1) is 300 rpm to 400 rpm; Preferably, the median particle size D50 of the seed crystals in step (1) is 3 μm to 5 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Step (2) the second base liquid contains a second complexing agent and a second precipitating agent; Preferably, the pH of the second base solution in step (2) is 10 to 11.5; Preferably, the concentration of the second complexing agent in the second base solution in step (2) is 4 g / L to 12 g / L; Preferably, the solute in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) comprises nickel salt, manganese salt, cobalt salt and cerium salt; Preferably, the molar ratio of nickel ions, cobalt ions and manganese ions in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is (0.8-0.98):(0.01-0.2):(0.01-0.2); Preferably, the total mass concentration of nickel salt, manganese salt and cobalt salt in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is 100 g / L to 200 g / L; Preferably, the molar concentration of cerium ions in the cerium-containing nickel-cobalt-manganese mixed salt solution in step (2) is 0.1 mol / L to 0.3 mol / L; Preferably, the second complexing agent in step (2) comprises aqueous ammonia; Preferably, the mass concentration of the ammonia water is 10% to 20%; Preferably, the second precipitant in step (2) comprises a sodium hydroxide solution; Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the two-step coprecipitation reaction in step (2) is 50° C. to 60° C.; Preferably, during the two-step coprecipitation reaction in step (2), the concentration of the second complexing agent is 4 to 6 g / L; Preferably, the pH of the two-step coprecipitation reaction in step (2) is 9 to 12; Preferably, during the two-step coprecipitation reaction in step (2), the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 10 L / h to 50 L / h; Preferably, the stirring speed of the two-step coprecipitation reaction in step (2) is 250 rpm to 350 rpm; Preferably, the median particle size D50 of the half-step precursor in step (2) is 8 μm to 13 μm.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The mass concentration of the cerium salt in the cerium salt solution in step (3) is 2 g / L to 15 g / L; Preferably, the third complexing agent in step (3) comprises aqueous ammonia; Preferably, the mass concentration of the ammonia water is 10% to 20%; Preferably, the third precipitant in step (3) comprises sodium hydroxide solution; Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the three-step coprecipitation reaction in step (3) is 40° C. to 60° C.; Preferably, during the three-step coprecipitation reaction in step (3), the concentration of the third complexing agent is 2 to 4 g / L; Preferably, the pH of the three-step coprecipitation reaction in step (3) is 10-11; Preferably, during the three-step co-precipitation reaction in step (3), the flow rate of the cerium salt solution is 80 mL / min to 180 mL / min; Preferably, the stirring speed of the three-step coprecipitation reaction in step (3) is 130 rpm to 160 rpm; Preferably, the median particle size D50 of the cerium-modified ternary precursor in step (3) is 10 μm to 15 μm.

8. A cerium-modified ternary precursor, characterized in that: The cerium-modified ternary precursor is prepared by the preparation method according to any one of claims 1 to 7.

9. A cerium-modified ternary cathode material, characterized in that: The cerium-modified ternary positive electrode material is prepared by mixing and sintering the cerium-modified ternary precursor as claimed in claim 8 with a lithium source.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the cerium-modified ternary cathode material as claimed in claim 9.