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EP-4742325-A1 - LITHIUM-ION POSITIVE ELECTRODE MATERIAL, PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

EP4742325A1EP 4742325 A1EP4742325 A1EP 4742325A1EP-4742325-A1

Abstract

Disclosed are a cathode material for lithium ion batteries, a preparation method therefor, and use thereof, which relate to the technical field of lithium ion batteries. The ability of a polycrystalline cathode material to resist the generation of internal cracks during cycle is evaluated by anti-cracking strength. By providing a cathode material, which has an anti-cracking strength that satisfies a specific range, and a high-strength crystals and grain boundaries, so that the structural stability of the material can be improved, and the diffusion of the internal cracks to the interface can be effectively inhibited, thereby improving the cycle stability and lifetime of the material.

Inventors

  • YU, Haijun
  • LI, Changdong
  • WANG, TAO
  • HUANG, Weiyan

Assignees

  • Guangdong Brunp Recycling Technology Co., Ltd.
  • Hunan Brunp Recycling Technology Co., Ltd.

Dates

Publication Date
20260513
Application Date
20241114

Claims (15)

  1. A cathode material for lithium ion batteries, having an anti-cracking strength of 4 MPa to 15 MPa; Anti − cracking strength = Average crushing strength rate of change of unit cell parameter = St ¯ / 1000 Δ c a max × Δ c a t ; where , wherein St represents a crushing strength obtained through an indentation test in MPa; St represents an average crushing strength in MPa, St ¯ = ∑ i = 1 n St i / n , n is a sample size, and n≥10; Δ c a max represents a maximum variation value of shear strain during a first charging process; Δ c a max = Δ c a max − Δ c a min ; where Δ c a t represents a variation value of shear strain after 10 charge-discharge cycles, t=10; where Δ c a t = c a t − c a 0 ; Δ c a t represents a shear strain measured at a static state after 10 charge-discharge cycles, and c a 0 represents a shear strain measured at a static state before the first charge; and a and c each represents a unit cell parameter.
  2. The cathode material according to claim 1, wherein the cathode material has an anti-cracking strength of 6 MPa to 15 MPa; St = 2.8 × P / πd 2 ; wherein P represents a maximum pressure value before a point of sudden pressure drop in an indentation test in mN; d represents a particle diameter of the cathode material in µm; Δ c a max ranges from 0.2 to 0.3, Δ c a t ranges from 0.01 to 0.20, and St ranges from 90 MPa to 140 MPa; and c and a are each obtained by XRD testing via an X-ray diffractometer.
  3. The cathode material according to claim 1 or 2, wherein the cathode material has a general formula of Li x Ni a Co b M c M' 1-a-b-c A y O 2-y ; wherein M is at least one selected from the group consisting of Al and Mn; M' is at least one selected from the group consisting of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, Si, Ca, Cu, La, Ce, Bi, In, Al, Nb and Y; A is at least one selected from the group consisting of P and F; and 0.95≤x<1.1, a>0, b>0, c>0, 0.95≤(a+b+c)≤1 and 0≤y≤0.01.
  4. A method for preparing the cathode material for the lithium ion batteries according to any one of claims 1 to 3, comprising: preparing a cathode material that satisfies anti-cracking strength requirements.
  5. The method according to claim 4, comprising: preparing a precursor inner core with a nickel salt, a cobalt salt and an M salt by a coprecipitation reaction; mixing the precursor inner core with a reinforcement solution to allow a reaction, and then calcining to obtain a reinforcement precursor inner core; wherein raw materials in the reinforcement solution are calcined to obtain a reinforcement aid; and the reinforcement aid is at least one selected from the group consisting of LiAlO 2 , LiMn 2 O 4 and LiCoPO 4 ; performing a coprecipitation reaction using the nickel salt, the cobalt salt, the M salt and a first doping element compound, to continuously grow a shell on the reinforcement precursor inner core, so as to obtain a ternary precursor with a core-shell structure; wherein the first doping element compound has at least one doping element selected from the group consisting of Ti, Al, Zr and Mg; and mixing the ternary precursor with a lithium source and calcining a resulting mixture; or, mixing the ternary precursor, a second doping element compound and a lithium source and calcining a resulting mixture; wherein the second doping element compound has at least one doping element selected from the group consisting of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, F, Si, Ca, Cu, La, P, Ce, Bi, In, Nb and Y.
  6. The method according to claim 5, wherein the precursor inner core has primary particles radially arranged and has a porosity of 4% to 12%.
  7. The method according to claim 5 or 6, wherein a preparation process of the precursor inner core comprises: preparing a base solution in a reactor, and introducing a first mixed metal salt solution, a first precipitant solution, and a first complexing agent solution into the base solution for a coprecipitation reaction, and the preparation process of the precursor inner core satisfies at least one of features A 1 to E 1 : feature A 1 : a reaction temperature of the coprecipitation reaction is controlled at 75°Cto 95°C; feature B 1 : a pH value of the coprecipitation reaction is controlled at 10.5 to 11.5; feature C 1 : when a particle size D50 grows to 2 µm to 17 µm, the introductions are stopped; feature D 1 : the coprecipitation reaction is performed under a protection of an inert atmosphere, and a rotation speed during the reaction is 400 rpm to 800 rpm; and feature E 1 : after the coprecipitation reaction is completed, aging is performed, followed by carrying out alkali solution washing, water washing and drying successively.
  8. The method according to claim 7, wherein the preparation process of the precursor inner core satisfies at least one of features F 1 to K 1 : feature F 1 : the first complexing agent solution is an ammonia solution with a mass fraction of 18% to 22%, wherein during the coprecipitation reaction, an ammonia concentration in the reactor is controlled at 3 g/L to 7 g/L; feature G 1 : the first mixed metal salt solution has a total molar concentration of metal ions of 1.8M to 2.2M, and a flow rate of 400 L/h to 500 L/h; feature H 1 : the first mixed metal salt solution has a molar ratio of nickel, cobalt and M of 35-98: 1-35: 1-35; feature I 1 : the first mixed metal salt solution has a salt of any one of nitrate, chloride salt and sulfate; feature J 1 : the first precipitant solution is a sodium hydroxide solution with a mass fraction of 30% to 34%; and feature K 1 : the base solution has an ammonia concentration of 4.5 g/L to 5.5 g/L, and a pH value of 11.8 to 12.2.
  9. The method according to any one of claims 5 to 8, wherein a preparation process of the reinforcement precursor inner core comprises: subjecting the precursor inner core and the reinforcement solution to mixing and ultrasonicating, reacting a resulting mixture for 10 min to 60 min at a temperature of 100°C to 150°C and a pressure of 10 MPa to 20 MPa, followed by performing a solid-liquid separation to obtain a solid material, and calcining the solid material.
  10. The method according to claim 9, wherein the preparation process of the reinforcement precursor inner core satisfies at least one of features A 2 to F 2 : feature A 2 : the reinforcement solution further contains a thickener, and a viscosity of the reinforcement solution is adjusted to 5 mPa·s to 8 mPa·s by regulating a dosage of the thickener; feature B 2 : when feature A2 is satisfied, the thickener is at least one selected from the group consisting of carbomer, xanthan gum, gelatin and starch; feature C 2 : a dosage of the reinforcement solution in 1 g the precursor inner core is 90 mL to 110 mL; feature D 2 : the ultrasonicating is performed for 10 min to 60 min; feature E 2 : the calcining is performed at 600°C to 700°C for 3 h to 8 h; and feature F 2 : the solid material is first dried at a condition of 80°C to 120°C for 5 h to 10 h and then calcined.
  11. The method according to any one of claims 5 to 10, wherein a preparation process of the ternary precursor having a core-shell structure comprises: adding the reinforcement precursor inner core to a base solution in a reactor, and introducing a second mixed metal salt solution, a second precipitant solution and a second complexing agent solution to the reactor for a coprecipitation reaction; wherein the second mixed metal salt solution contains a nickel salt, a cobalt salt, an M salt and a first doping element compound, and by regulating an addition rate of the second mixed metal salt solution, an addition rate of the nickel, cobalt and M elements during the coprecipitation reaction is controlled to be lower than an addition rate when preparing the precursor inner core.
  12. The method according to claim 11, wherein the preparation process of the ternary precursor having a core-shell structure satisfies at least one of features A 3 to I 3 : feature A 3 : the second mixed metal salt solution has a total molar concentration of nickel, cobalt, and M elements of 1.8M to 2.2M, a flow rate of the second mixed metal salt solution is 100 L/h-200 L/h, and a pH value is regulated to be 2 to 5; feature B 3 : based on a total molar amount of the nickel, cobalt and M elements, a ratio of a total molar amount of the metal in the reinforcement precursor inner core to a total molar amount of the metal in the second mixed metal salt solution is 4-12: 1; feature C 3 : the second mixed metal salt solution has a molar ratio of nickel, cobalt and M elements of 30-60: 20-35: 20-35; feature D 3 : the coprecipitation reaction is performed at a reaction temperature of 75°C to 95°C, and a reaction pH value of 10.8 to 11.2; feature E 3 : the second complexing agent solution is an ammonia solution with a mass fraction of 18% to 22%, wherein during the coprecipitation reaction, an ammonia concentration in the reactor is controlled at 3 g/L to 7 g/L; feature F 3 : the first doping element compound is at least one selected from the group consisting of titanium disulfate, sodium metaaluminate, zirconium nitrate, zirconium acetate, zirconium sulfate, magnesium sulfate and magnesium nitrate; feature G 3 : the base solution in the reactor is water, and the second precipitant solution is a sodium hydroxide solution with a mass fraction of 30% to 40%; feature H 3 : the coprecipitation reaction is performed under a protection of an inert atmosphere, and a rotation speed during the reaction is 300 rpm to 500 rpm; and feature I 3 : after introducing the second mixed metal salt solution, the reaction is continued for 0.5 h to 2.0 h, and then a solid-liquid separation is performed, and an obtained solid material is washed with water and dried.
  13. The method according to any one of claims 5 to 12, wherein the process of mixing the ternary precursor, the second doping element compound and the lithium source and calcining a resulting mixture satisfies at least one of features A 4 to F 4 : feature A 4 : a molar ratio of a total amount of nickel, cobalt, and M elements in the ternary precursor to a lithium content in the lithium source is 1: 1.05-1.1; feature B 4 : the lithium source is lithium hydroxide; feature C 4 : the second doping element compound is at least one selected from the group consisting of oxides, fluorides, carbonates, hydroxides, nitrides, borides, and nitrates; feature D 4 : the calcining comprises a first calcination performed at 400°Cto 500°C for 2 h to 6 h, and a second calcination performed at 750°C to 850°C for 10 h to 15 h; feature E 4 : the calcining is performed in an oxygen-containing atmosphere; and feature F 4 : the ternary precursor, the second doping element compound, and the lithium source are first mixed and ground, and then calcined.
  14. A cathode sheet, comprising the cathode material according to any one of claims 1 to 3 or the cathode material prepared by the method according to any one of claims 4 to 13.
  15. A lithium ion battery, comprising the cathode sheet according to claim 14.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present disclosure claims priority of Chinese patent application No. 2024109102998 filed with the Chinese Patent Office on July 9, 2024, entitled "CATHODE MATERIAL FOR LITHIUM ION BATTERIES, PREPARATION METHOD THEREFOR, AND USE THEREOF," the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to the technical field of lithium batteries, and in particular, to a cathode material for lithium batteries, a preparation method therefor, and use thereof. BACKGROUND The rapid development of lithium-ion batteries has driven the rapid development of ternary cathode materials, which have the advantages of high specific capacity, moderate price, low toxicity and relatively abundant resources. However, there are also many problems with a ternary material, especially a nickel-rich ternary material, which has poor cycle performance of batteries, multi-level phase transitions during charging and discharging, and large volume changes during charging and discharging, which can easily cause residual stress, and leading to problems of mechanical fracture, etc. In order to increase the tap density of the ternary material while suppressing the generation of surface side reactions, the ternary material is prepared into secondary particles formed by the dense stacking of primary particles, which greatly reduces the contact between the primary particles and the electrolytic solution, thereby reducing the generation of interfacial side reactions. However, the secondary particles still bring new problems: First, the secondary particles require a very dense arrangement of primary particles, especially a dense interface, which can effectively block the contact between the internal primary particles and the electrolytic solution. Such dense secondary particles greatly increase the difficulty of synthesis. In addition, the expansion and contraction of the volume of the secondary particles during the charging and discharging process will cause an increase in internal stress, and the long-term cycle will cause these stresses to gradually accumulate, gradually leading to microcracks inside and on the surface of the secondary particles, and eventually causing the entire secondary particles to rupture. The mechanical fracture of the ternary cathode materials undergoes the following development process: during the charging process, as the deintercalation of Li+ occurs, the interlayer spacing of the ternary material gradually increases, which is mainly due to the increase in electrostatic repulsion between the layers after the deintercalation of Li+. When a highly delithiated state is reached, the interlayer spacing shrinks. The reason for the shrinkage may be the structural slip caused by the deintercalation of a large amount of Li+ from the interlayer; it may further because O participates in the redox reaction, resulting in a decrease in the interlayer electrostatic repulsion and a decrease in the interlayer spacing. During the discharging process, the change in interlayer spacing is completely opposite to that during the charging process. During one charging and discharging process, the layered material undergoes four expansion and shrinkage cycles, which inevitably generates residual stress during the volume change. The accumulation of residual stress leads to microcracks at the grain boundaries between the particles, thereby increasing the contact with the electrolytic solution, aggravating interfacial side reactions, which further exacerbates the expansion of microcracks, ultimately leading to particle rupture, resulting in a decrease or even failure in battery capacity. It can be seen that the final rupture of the polycrystalline ternary cathode material particles is related to the unit cell deformation and failure of grain boundaries of the ternary cathode material. The unit cell and grain boundary jointly affect whether the cathode material is prone to cracking during use. It is of great significance to provide a cathode material with both high-strength crystals and grain boundaries. Therefore, there is an urgent need to provide cathode materials with both high-strength crystals and grain boundaries to improve the ability of a material to resist the generation of internal cracks during cycle, thereby improving the cycle stability and lifetime of the material. In view of this, the present disclosure is proposed. SUMMARY The objective of the present disclosure is to provide a cathode material for lithium ion batteries, a preparation method therefor, and use thereof, which aims to improve the ability of a material to resist the generation of internal cracks during cycle, thereby improving the cycle stability and lifetime of the material. The present disclosure is implemented as follows. In a first aspect, the present disclosure provides a cathode material for lithium ion batteries having an anti-cracking strength of 4 MPa to 15 MPa; Anti−c