Cerium modified ternary precursor, preparation method and application thereof

Abstract

The application provides a cerium-modified ternary precursor and a preparation method and application thereof, and the preparation method comprises the following steps: (1) injecting a nickel-cobalt-manganese mixed salt solution, a complexing agent and a precipitating agent into a bottom liquid in parallel flow, and obtaining crystal seeds through a coprecipitation reaction; (2) placing the crystal seeds in the bottom liquid, injecting a cerium-containing nickel-cobalt-manganese mixed salt solution, a complexing agent and a precipitating agent into the bottom liquid in parallel flow, and obtaining a mixed solution containing a semi-step precursor through a coprecipitation reaction; and (3) injecting a cerium salt solution, a complexing agent and a precipitating agent into the mixed solution containing the semi-step precursor, and obtaining the cerium-modified ternary precursor through a coprecipitation reaction. The application modifies the positive electrode precursor by simultaneously doping and coating cerium, improves the disadvantage of cation mixing, hinders the reaction between the prepared positive electrode material and the electrolyte, prevents the dissolution of metal ions, improves the stability and cycle performance of the positive electrode material from multiple aspects, and achieves the purpose of simplifying the preparation steps.

Description

TECHNICAL FIELD

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

[0002] The environmental pollution problem caused by fossil fuel consumption is aggravated, leading to the 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 determining the performance of lithium ion batteries. Nickel-cobalt-manganese (NCM) high-nickel ternary positive electrode material has always been the core of lithium battery positive electrode material due to its high energy density. However, NCM high-nickel ternary material still has the shortcomings of poor cycle performance and thermal stability. By modifying the structure and composition of NCM high-nickel ternary precursor, its shortcomings can be improved, and its market utilization rate can be further improved.

[0003] CN118771488A discloses a preparation method of a cerium and bismuth doped cobalt-free precursor. By adding cerium salt in the nickel salt of the raw material and bismuth in 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 carry out a co-precipitation reaction, obtaining a cobalt-free precursor with gradient distribution of nickel and manganese. The doping of cerium and bismuth plays a role in assisting the fusion in the later sintering process of the positive electrode material, making the material more easily sintered into a single crystal, and reducing the occurrence of heterogeneous phases due to incomplete sintering of manganese inside the material. However, this method does not utilize the influence of the doped element cerium on the internal structure of the positive electrode material during the charging and discharging process.

[0004] CN117776288A discloses a preparation method of a zinc hydroxystannate coated sodium ion precursor. By adding zinc oxide, water and a precursor matrix to a tin solution dissolved in alkali solution, a zinc hydroxystannate coated sodium ion battery precursor is obtained. In the subsequent calcination process to prepare sodium ions, the zinc hydroxystannate can be in-situ oxidized into zinc oxide and tin oxide, forming a coating layer to resist the corrosion of electrolyte and induce the formation of sodium deficient phases. Not only the kinetic performance of the entire material particles is improved, but also the rate performance and cycle performance of the battery are improved. However, in this method, a large amount of metal is used to form the coating layer structure, and other elements are doped in the precursor in the scheme, making the material composition complex, the preparation process complicated and the cost high. SUMMARY

[0005] The purpose of the present application is to provide a cerium-modified ternary precursor and a preparation method and application thereof. The present application modifies the positive electrode precursor by using cerium for simultaneous doping and coating, which not only improves the disadvantage of cation mixing, but also hinders the reaction between the prepared positive electrode material and the electrolyte, prevents the dissolution of metal ions, improves the stability and cycle performance of the positive electrode material from multiple aspects, and achieves the purpose of simplifying the preparation steps.

[0006] To achieve the object of the present application, the present application adopts the following technical solutions:

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

[0008] (1) injecting a nickel-cobalt-manganese mixed salt solution, a first complexing agent and a first precipitant into a first bottom liquid in parallel flow to obtain a crystal seed through a one-step co-precipitation reaction;

[0009] (2) placing the crystal seed in a second bottom liquid, 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 flow to obtain a mixed solution containing a semi-step precursor through a two-step co-precipitation reaction;

[0010] (3) injecting a cerium salt solution, a third complexing agent and a third precipitant into the mixed solution containing the semi-step precursor to obtain the cerium-modified ternary precursor through a three-step co-precipitation reaction.

[0011] By adjusting the co-precipitation method and the materials added in each step, the present application introduces cerium into the ternary positive electrode precursor as a doping ion and a coating layer at the same time, improves the structural stability of the ternary positive electrode material, reduces the side reactions on the electrode / electrolyte interface, and inhibits the dissolution of metal ions, thereby more effectively improving the thermal stability and cycle performance of the positive electrode material. The present application uses the same metal element for two modifications, reduces the preparation cost and process steps of the material, and saves the preparation time.

[0012] Preferably, the solutes in the nickel-cobalt-manganese mixed salt solution in step (1) include 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 only limited to the listed values, but also other values not listed within the value 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-200 g / L, for example: 100 g / L, 120 g / L, 150 g / L, 180 g / L or 200 g / L, etc., not only limited to the listed values, but also other values not listed within the value range are also applicable.

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

[0016] Preferably, the mass concentration of the ammonia water is 10% to 20%, such as 10%, 12%, 15%, 18%, or 20%, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

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

[0018] Preferably, the mass concentration of the sodium hydroxide solution is 25% to 35%, such as 25%, 28%, 30%, 32%, or 35%, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

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

[0020] Preferably, the pH of the first bottom solution in step (1) is 10 to 11.5, such as 10, 10.2, 10.5, 11, or 11.5, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

[0021] Preferably, the concentration of the first complexing agent in the first bottom solution in step (1) is 4 g / L to 12 g / L, such as 4 g / L, 6 g / L, 8 g / L, 10 g / L, or 12 g / L, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

[0022] Preferably, the temperature of the one-step co-precipitation reaction in step (1) is 50°C to 60°C, such as 50°C, 52°C, 55°C, 58°C, or 60°C, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

[0023] Preferably, the concentration of the first complexing agent during the one-step co-precipitation reaction in step (1) is 3 g / L to 5 g / L, such as 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, or 5 g / L, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

[0024] Preferably, the pH of the one-step co-precipitation reaction in step (1) is 9 to 11, such as 9, 9.5, 10, 10.5, or 11, and the like, not only limited to the listed values, but also other values within the range of the values are applicable.

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

[0026] Preferably, the median particle size D50 of the seed crystals in step (1) is 3 μm to 5 μm, for example, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, and the like, not only limited to the listed values, but also other values not listed within the range of values are also applicable.

[0027] Preferably, the second bottom solution in step (2) contains a second complexing agent and a second precipitant.

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

[0029] Preferably, the concentration of the second complexing agent in the second bottom solution 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, and the like, not only limited to the listed values, but also other values not listed within the range of values 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 to 0.98):(0.01 to 0.2):(0.01 to 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, and the like, not only limited to the listed values, but also other values not listed within the range of values 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, and the like, not only limited to the listed values, but also other values not listed within the range of values are also applicable.

[0033] Preferably, the molar concentration of cerium ions in the cerium-containing nickel-cobalt-manganese mixed salt solution of 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, the second complexing agent of step (2) comprises ammonia water.

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

[0036] Preferably, the second precipitating agent of step (2) comprises a 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 only limited to the listed values, other values not listed within this range are also applicable.

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

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

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

[0041] Preferably, the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution during the two-step co-precipitation reaction of step (2) 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 only limited to the listed values, other values not listed within this 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 unlisted values ​​within this range are also applicable.

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

[0044] Preferably, the mass concentration of 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., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the third complexing agent in step (3) includes 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. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the third precipitant in step (3) includes a 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., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

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

[0050] Preferably, in the three-step coprecipitation reaction described 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., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

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

[0052] Preferably, during the three-step coprecipitation 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 unlisted values ​​within this range are also applicable.

[0053] Preferably, the stirring speed of the three-step coprecipitation 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 unlisted values ​​within this 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., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

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

[0056] The cerium-modified ternary precursor of the present invention contains Ce-doped Ce. 3+ and Ce 4+ There are two valence states, which can interconvert in chemical processes, while Ce... 4+ It has strong oxidizing properties and can oxidize Ni. 2+ Oxidized to Ni 3+ Reduce Li during charging and discharging + / Ni 2+ The degree of mixing improves the cycle efficiency of the cathode material. The presence of numerous oxygen vacancies effectively captures unstable oxygen-containing substances (such as O2) generated during deep lithium insertion / extraction. 2- O- and O2 2- This reduces oxygen release. The CeO2 coating (from which cerium hydroxide is oxidized to cerium dioxide during cathode material preparation) further reduces the reaction between the cathode material and the electrolyte, minimizing phase transitions and structural damage to the cathode material, thus improving material stability and safety.

[0057] Thirdly, the present invention provides a cerium-modified ternary cathode material, which is prepared by mixing and sintering a cerium-modified ternary precursor as described in the second aspect with a lithium source.

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

[0059] Fourthly, the present invention provides a lithium-ion battery comprising a cerium-modified ternary cathode material as described in the third aspect.

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

[0061] (1) In this invention, cerium is introduced into the ternary cathode precursor as both a dopant ion and a coating layer, thereby improving the structural stability of the ternary cathode material, reducing side reactions at the electrode / electrolyte interface, and inhibiting the dissolution of metal ions, thus more effectively improving the thermal stability and cycle performance of the cathode material.

[0062] (2) The method described in this invention is applicable to various high-nickel ternary cathode materials and has good discharge specific capacity at 0.1C. The cathode material prepared by preparing cerium-modified ternary precursor can achieve a capacity retention rate of 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 Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0064] Example 1

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

[0066] (1) Based on the Ni:Co:Mn molar ratio of 0.97:0.01:0.02, a nickel-cobalt-manganese sulfate mixed salt solution with a total concentration of 150 g / L was prepared. A portion of the nickel-cobalt-manganese sulfate mixed salt solution was added to 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, using 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 reaction vessels respectively, and the mixture was stirred at a flow rate of 0.8 m... 3Nitrogen gas is introduced into the base solution at a rate of / h, and the mixture is stirred at 200rpm to ensure uniform mixing. Then, the temperature is raised to 40℃, the pH is controlled at 11-11.5, and the ammonia concentration is controlled at 6g / L~8g / L to obtain the base solution (the first base solution is the same as the second base solution).

[0067] (2) The nickel cobalt manganese sulfate mixed salt solution, sodium hydroxide solution and ammonia water were injected into the first base liquid in parallel. At 50℃ and 300rpm, the pH was controlled at 9 and the complexing agent concentration was 3g / L to carry out a one-step co-precipitation reaction. When the median particle size D50 of the solid material in the system was 3μm, the seed crystals were obtained by washing.

[0068] (3) Place the seed crystal in the second bottom liquid, and inject the cerium-containing nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution and ammonia water into the second bottom liquid in a parallel flow. The flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 10L / h. Under the stirring speed of 300rpm at 55℃, the pH is controlled at 9.5 and the complexing agent concentration is 4g / L to carry out a two-step co-precipitation reaction. When the median particle size D50 of the solid material in the system is 9μm, stop feeding to obtain a mixed solution containing a half-step precursor.

[0069] (4) Cerium sulfate solution, sodium hydroxide solution and ammonia water are injected concurrently into a mixed solution containing a half-step precursor. The flow rate of the cerium sulfate solution is 80 mL / min. The pH is controlled at 10.5 and the complexing agent concentration is 2 g / L at 50 °C and 150 rpm. A two-step co-precipitation reaction is carried out. When the median particle size D50 of the solid material in the system is 11 μm, the feeding is stopped to obtain the cerium-modified ternary cathode precursor.

[0070] Example 2

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

[0072] (1) Based on the Ni:Co:Mn molar ratio of 0.90:0.03:0.07, a nickel-cobalt-manganese sulfate mixed salt solution with a total concentration of 150 g / L was prepared. A portion of the nickel-cobalt-manganese sulfate mixed salt solution was added to cerium sulfate to obtain a cerium-containing nickel-cobalt-manganese mixed salt solution with a cerium molar concentration of 0.3 mol / L. A cerium sulfate solution with a mass concentration of 6 g / L was prepared, using sodium hydroxide solution 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 reaction vessels respectively, and the mixture was stirred at a flow rate of 0.8 m... 3Nitrogen gas is introduced into the base solution at a rate of / h, and the mixture is stirred at 200rpm to ensure uniform mixing. Then, the temperature is raised to 40℃, the pH is controlled at 11-11.5, and the ammonia concentration is controlled at 6g / L~8g / L to obtain the base solution (the first base solution is the same as the second base solution).

[0073] (2) The nickel cobalt manganese sulfate mixed salt solution, sodium hydroxide solution and ammonia water were injected into the first base liquid in parallel. At 55℃ and 350rpm, the pH was controlled at 10 and the complexing agent concentration was 4g / L to carry out a one-step co-precipitation reaction. When the median particle size D50 of the solid material in the system was 4μm, the seed crystals were obtained by washing.

[0074] (3) Place the seed crystal in the second bottom liquid, and inject the cerium-containing nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution and ammonia water into the second bottom liquid in a parallel flow. The flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 25L / h. Under the stirring speed of 300rpm at 55℃, the pH is controlled at 9.5 and the complexing agent concentration is 5g / L to carry out a two-step co-precipitation reaction. When the median particle size D50 of the solid material in the system is 9μm, stop feeding to obtain a mixed solution containing a half-step precursor.

[0075] (4) Cerium sulfate solution, sodium hydroxide solution and ammonia water are injected concurrently into a mixed solution containing a half-step precursor. The flow rate of the cerium sulfate solution is 150 mL / min. The pH is controlled at 10 and the concentration of the complexing agent is 3 g / L at 60 °C and 130 rpm. 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 cathode precursor.

[0076] Example 3

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

[0078] (1) Prepare a nickel-cobalt-manganese sulfate mixed salt solution with a total concentration of 150 g / L based on a Ni:Co:Mn molar ratio of 0.80:0.1:0.1. Add cerium sulfate to a portion of the nickel-cobalt-manganese sulfate mixed salt solution to obtain a cerium-containing nickel-cobalt-manganese mixed salt solution with a cerium molar concentration of 0.2 mol / L. Prepare a cerium sulfate solution with a mass concentration of 10 g / L. Use sodium hydroxide solution as a precipitant with a mass concentration of 35%. Use ammonia water as a complexing agent with a mass concentration of 20%. Add 150 L of pure water and a certain amount of NaOH solution and ammonia water to two 300 L reaction vessels respectively, and then... 3 Nitrogen gas is introduced into the base solution at a rate of / h, and the mixture is stirred at 200rpm to ensure uniform mixing. Then, the temperature is raised to 40℃, the pH is controlled at 11-11.5, and the ammonia concentration is controlled at 6g / L~8g / L to obtain the base solution (the first base solution is the same as the second base solution).

[0079] (2) The nickel cobalt manganese sulfate mixed salt solution, sodium hydroxide solution and ammonia water were injected into the first base liquid in parallel. At 60℃ and 300rpm, the pH was controlled at 11 and the complexing agent concentration was 5g / L. A one-step co-precipitation reaction was carried out. When the median particle size D50 of the solid material in the system was 4μm, the seed crystals were obtained by washing.

[0080] (3) Place the seed crystal in the second bottom liquid, and inject 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. Under the stirring speed of 300 rpm at 60℃, the pH is controlled to be 11 and the complexing agent concentration is 6 g / L to carry out a two-step co-precipitation 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) Cerium sulfate solution, sodium hydroxide solution and ammonia water are injected concurrently into a mixed solution containing a half-step precursor. The flow rate of the cerium sulfate solution is 150 mL / min. The pH is controlled at 10 and the concentration of the complexing agent is 4 g / L at 60 °C and 130 rpm. A two-step co-precipitation reaction is carried out. 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 cathode precursor.

[0082] Example 4

[0083] 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 0.01 mol%, while the other conditions and parameters are exactly the same as 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%, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0086] Example 6

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

[0088] Example 7

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

[0092] Comparative Example 2

[0093] The only difference between this comparative example and Example 1 is that step (4) uses a solution without cerium salt, while the other conditions and parameters are exactly the same as in Example 1.

[0094] Comparative Example 3

[0095] The only difference between this comparative example and Example 1 is that cerium is not added in steps (3) and (4), i.e., a cerium-free ternary precursor is prepared. Other conditions and parameters are exactly the same as in Example 1.

[0096] Performance testing:

[0097] Cerium-modified ternary precursors obtained from Examples 1-7 and Comparative Examples 1-3 were washed, dried, sieved, and iron-removed. They were then mixed with lithium hydroxide at a molar ratio of 1.05:1 and calcined in an oxygen atmosphere at 900°C for 14 hours to obtain cerium-doped and coated modified ternary lithium cathode materials. The obtained ternary cathode material, polyvinylidene fluoride, and acetylene black were mixed uniformly at a mass ratio of 8:1:1 to form a slurry. This slurry was then uniformly coated onto aluminum foil, dried in an oven at 110°C for 14 hours, and pressed into cathode sheets. Using lithium sheets as the anode and lithium hexafluorophosphate as the electrolyte solution, CR2032 coin cells were assembled. Electrochemical performance was tested at 2.8-4.3V, and the results are shown in Table 1.

[0098] Table 1

[0099] Discharge specific capacity at 0.1 C (mAh / g) Capacity retention rate (%) after 1 C cycling for 50 cycles 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, and from Examples 1-7, the method described in this invention is applicable to various high-nickel ternary cathode materials, exhibiting good discharge specific capacity at 0.1C. The cathode material prepared from the cerium-modified ternary precursor can achieve a capacity retention rate of over 80.25% after 50 cycles at 1C. By adjusting the preparation conditions, the capacity retention rate can reach over 86.17% after 50 cycles at 1C.

[0101] A comparison of Examples 1 and 4-5 shows that during the preparation 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 affects its performance. Controlling the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution to 0.1 mol / L to 0.3 mol / L results in a cerium-modified ternary precursor with better performance. If the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution is too low, the degree of cation mixing in the subsequently prepared lithium-ion cathode material will increase, reducing the charge-discharge efficiency of the material. If the molar concentration of cerium in the cerium-containing nickel-cobalt-manganese mixed salt solution is too high, it will reduce the electron transfer rate, thereby reducing the electrochemical performance of the material.

[0102] A comparison of Examples 1 and 6-7 shows that the mass concentration of cerium in the cerium salt solution affects the performance of the cerium-modified ternary precursor during its preparation. Controlling the mass concentration of cerium in the cerium salt solution to 2 g / L–15 g / L results in a cerium-modified ternary precursor with better performance. If the mass concentration of cerium in the cerium salt solution is too low, the cerium oxide layer cannot completely coat the ternary particles, leading to reduced structural stability of the subsequently prepared cathode 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] A comparison of Example 1 and Comparative Example 1 shows that the Ce-doped Ce in the cerium-modified ternary precursor of the present invention contains Ce. 3+ and Ce 4+ There are two valence states, which can interconvert in chemical processes, while Ce... 4+ It has strong oxidizing properties and can oxidize Ni. 2+ Oxidized to Ni 3+ Reduce Li during charging and discharging + / Ni 2+ The degree of mixing improves the cycle efficiency of the cathode material. The presence of numerous oxygen vacancies effectively captures unstable oxygen-containing substances (such as O2) generated during deep lithium insertion / extraction. 2- O- and O2 2- This reduces the release of oxygen.

[0104] As can be seen from the comparison between Example 1 and Comparative Example 2, the coated CeO2 layer (in the process of preparing the cathode material, cerium hydroxide is oxidized to cerium dioxide) reduces the reaction between the cathode material and the electrolyte, reduces the phase change and the degree of structural damage to the cathode material, and improves the stability and safety of the material.

[0105] As can be seen from the comparison between Example 1 and Comparative Example 3, the present invention, by adjusting the co-precipitation method and the materials added in each step, introduces cerium simultaneously as a dopant ion and a coating layer into the ternary cathode precursor, thereby improving the structural stability of the ternary cathode material, reducing 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 cathode material.

[0106] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a cerium-modified ternary precursor, characterized in that, The preparation method includes the following steps: (1) A nickel-cobalt-manganese mixed salt solution, a first complexing agent, and a first precipitant are injected concurrently into a first base liquid, and seed crystals are obtained through a one-step co-precipitation reaction; (2) Place the seed crystal in the second bottom liquid, and inject the cerium-containing nickel-cobalt-manganese mixed salt solution, the second complexing agent and the second precipitant into the second bottom liquid in a co-precipitation reaction to obtain a mixed solution containing a half-step precursor. (3) The cerium salt solution, the third complexing agent and the third precipitant are injected into a mixed solution containing a half-step precursor, and the cerium-modified ternary precursor is obtained by a three-step co-precipitation reaction; 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, and the mass concentration of cerium salt in the cerium salt solution in step (3) is 2 g / L to 15 g / L.

2. The preparation method according to claim 1, characterized in that, The solutes in the nickel-cobalt-manganese mixed salt solution in step (1) include nickel salt, manganese salt and cobalt salt.

3. The preparation method according to claim 1, characterized in that, 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).

4. The preparation method according to claim 1, characterized in that, In step (1), the total mass concentration of nickel salt, manganese salt and cobalt salt in the nickel-cobalt-manganese mixed salt solution is 100 g / L to 200 g / L.

5. The preparation method according to claim 1, characterized in that, Step (1) The first complexing agent includes ammonia.

6. The preparation method according to claim 5, characterized in that, The mass concentration of the ammonia water is 10%~20%.

7. The preparation method according to claim 1, characterized in that, Step (1) The first precipitant includes a sodium hydroxide solution.

8. The preparation method according to claim 7, characterized in that, The sodium hydroxide solution has a mass concentration of 25% to 35%.

9. The preparation method according to claim 1, characterized in that, Step (1) The first base liquid contains a first complexing agent and a first precipitant.

10. The preparation method according to claim 1, characterized in that, Step (1) The pH of the first base solution is 10~11.

5.

11. The preparation method according to claim 1, characterized in that, Step (1) The concentration of the first complexing agent in the first base liquid is 4 g / L to 12 g / L.

12. The preparation method according to claim 1, characterized in that, The temperature of the one-step coprecipitation reaction in step (1) is 50℃~60℃.

13. The preparation method according to claim 1, characterized in that, In the one-step coprecipitation reaction described in step (1), the concentration of the first complexing agent is 3~5 g / L.

14. The preparation method according to claim 1, characterized in that, The pH of the one-step coprecipitation reaction in step (1) is 9~11.

15. The preparation method according to claim 1, characterized in that, The stirring speed for the one-step coprecipitation reaction in step (1) is 300 rpm to 400 rpm.

16. The preparation method according to claim 1, characterized in that, The median particle size D50 of the seed crystals in step (1) is 3μm~5μm.

17. The preparation method according to claim 1, characterized in that, Step (2) The second base liquid contains a second complexing agent and a second precipitant.

18. The preparation method according to claim 1, characterized in that, Step (2) The pH of the second base solution is 10~11.

5.

19. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the second complexing agent in the second base solution is 4 g / L to 12 g / L.

20. The preparation method according to claim 1, characterized in that, 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.

21. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of nickel ions, cobalt ions, and manganese ions in the cerium-containing nickel-cobalt-manganese mixed salt solution is (0.8~0.98):(0.01~0.2):(0.01~0.2).

22. The preparation method according to claim 1, characterized in that, In step (2), the total mass concentration of nickel salt, manganese salt and cobalt salt in the cerium-containing nickel-cobalt-manganese mixed salt solution is 100 g / L to 200 g / L.

23. The preparation method according to claim 1, characterized in that, Step (2) The second complexing agent includes ammonia.

24. The preparation method according to claim 23, characterized in that, The mass concentration of the ammonia water is 10%~20%.

25. The preparation method according to claim 1, characterized in that, Step (2) The second precipitant includes a sodium hydroxide solution.

26. The preparation method according to claim 25, characterized in that, The sodium hydroxide solution has a mass concentration of 25% to 35%.

27. The preparation method according to claim 1, characterized in that, The temperature of the two-step coprecipitation reaction in step (2) is 50℃~60℃.

28. The preparation method according to claim 1, characterized in that, In the two-step coprecipitation reaction described in step (2), the concentration of the second complexing agent is 4~6 g / L.

29. The preparation method according to claim 1, characterized in that, The pH of the two-step coprecipitation reaction in step (2) is 9~12.

30. The preparation method according to claim 1, characterized in that, In the two-step coprecipitation reaction described in step (2), the flow rate of the cerium-containing nickel-cobalt-manganese mixed salt solution is 10 L / h to 50 L / h.

31. The preparation method according to claim 1, characterized in that, The stirring speed for the two-step coprecipitation reaction in step (2) is 250 rpm to 350 rpm.

32. The preparation method according to claim 1, characterized in that, The median particle size D50 of the semi-step precursor in step (2) is 8 μm to 13 μm.

33. The preparation method according to claim 1, characterized in that, The third complexing agent in step (3) includes ammonia.

34. The preparation method according to claim 33, characterized in that, The mass concentration of the ammonia water is 10%~20%.

35. The preparation method according to claim 1, characterized in that, The third precipitant in step (3) includes a sodium hydroxide solution.

36. The preparation method according to claim 35, characterized in that, The sodium hydroxide solution has a mass concentration of 25% to 35%.

37. The preparation method according to claim 1, characterized in that, The temperature of the three-step coprecipitation reaction in step (3) is 40℃~60℃.

38. The preparation method according to claim 1, characterized in that, In the three-step coprecipitation reaction described in step (3), the concentration of the third complexing agent is 2~4 g / L.

39. The preparation method according to claim 1, characterized in that, The pH of the three-step coprecipitation reaction in step (3) is 10-11.

40. The preparation method according to claim 1, characterized in that, During the three-step coprecipitation reaction described in step (3), the flow rate of the cerium salt solution is 80 mL / min to 180 mL / min.

41. The preparation method according to claim 1, characterized in that, The stirring speed for the three-step coprecipitation reaction in step (3) is 130 rpm to 160 rpm.

42. The preparation method according to claim 1, characterized in that, The median particle size D50 of the cerium-modified ternary precursor in step (3) is 10 μm to 15 μm.

43. 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 1-42.

44. A cerium-modified ternary cathode material, characterized in that, The cerium-modified ternary cathode material is prepared by mixing and sintering the cerium-modified ternary precursor as described in claim 43 with a lithium source.

45. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the cerium-modified ternary cathode material as described in claim 44.