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CN-122025635-A - Composite lithium supplementing agent, preparation method thereof, positive plate and lithium ion battery

CN122025635ACN 122025635 ACN122025635 ACN 122025635ACN-122025635-A

Abstract

The invention relates to a composite lithium supplementing agent, a preparation method thereof, a positive plate and a lithium ion battery. The composite lithium supplementing agent comprises an inner core, an intermediate layer and an outer shell layer, wherein the intermediate layer and the outer shell layer are formed in situ along the direction away from the center of the inner core, the inner core is made of lithium-rich lithium nickelate, the intermediate layer is made of lithium-rich lithium ferrite, and the outer shell layer is made of lithium-rich lithium nickelate. According to the invention, the lithium-rich lithium ferrite intermediate layer is arranged between the lithium-rich lithium nickel acid lithium inner core and the shell, and a specific electric field structure formed by matching the concentration gradient of lithium ions with the double heterogeneous interfaces is utilized, so that the improvement of the electronic conductivity and the ion conductivity in the lithium-rich lithium ferrite is driven, and meanwhile, the air stability of the composite lithium supplementing agent is improved by the lithium-rich lithium nickel acid lithium shell, so that the composite lithium supplementing agent has high lithium supplementing capacity and good multiplying power performance and air stability.

Inventors

  • ZHANG JINYU
  • YAN DONGWEI
  • SUN HE
  • SHI ZETAO
  • ZHANG DANLEI
  • HAN LING
  • ZHU WU

Assignees

  • 天津国安盟固利新材料科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260204

Claims (10)

  1. 1. The composite lithium supplementing agent is characterized by comprising an inner core, and an intermediate layer and an outer shell layer which are formed in situ along the direction away from the center of the inner core; the material of the inner core comprises lithium-rich lithium nickel oxide; the material of the middle layer comprises lithium-rich lithium ferrite; the shell layer is made of lithium nickel acid lithium rich.
  2. 2. The composite lithium supplementing agent according to claim 1, wherein the molar ratio of the lithium-rich nickel acid lithium in the inner core to the lithium-rich iron acid lithium in the middle layer to the lithium-rich nickel acid lithium in the outer shell layer is (1-2): (7-8): (1-2); and/or the D50 particle size of the composite lithium supplementing agent is 5-10 mu m.
  3. 3. A method of preparing the composite lithium-supplementing agent according to claim 1 or 2, comprising: (1) Mixing nickel salt solution and precipitant solution, and carrying out precipitation reaction to obtain nickel-based precursor kernel suspension; (2) Mixing the nickel-based precursor inner core suspension, an iron salt solution and a precipitator solution, and performing precipitation reaction to obtain an iron-nickel composite precursor inner core suspension; (3) Mixing the iron-nickel composite precursor inner core suspension, nickel salt solution and precipitant solution, and carrying out precipitation reaction to obtain the composite lithium supplementing agent precursor; (4) And mixing the composite lithium supplementing agent precursor with a lithium source, and sintering to obtain the composite lithium supplementing agent.
  4. 4. The method according to claim 3, wherein the precipitation reaction temperature in step (1) to step (3) is 1 ℃ to 100 ℃; And/or, the pH value of the precipitation reaction in the step (1) to the step (3) is 9-12.
  5. 5. The method of claim 3, wherein the precipitant in the precipitant solution in step (1) to step (3) comprises any one or a combination of at least two of ammonia water, sodium hydroxide, potassium hydroxide, or lithium hydroxide; and/or the concentration of the precipitant solution in the step (1) and the step (2) is 0.1 mol/L-1 mol/L.
  6. 6. The method according to claim 3, wherein the nickel salt in the nickel salt solution in step (1) and step (3) comprises any one or a combination of at least two of nickel oxalate, nickel sulfate, nickel chloride, nickel nitrate, and nickel dichloride; And/or the ferric salt in the ferric salt solution in the step (2) comprises any one or a combination of at least two of ferric oxalate, ferric sulfate, ferric chloride or ferric nitrate; and/or, the concentration of the nickel salt solution in the step (1) and the concentration of the iron salt solution in the step (3) are respectively and independently 0.1mol/L to 3mol/L.
  7. 7. The method of claim 3, wherein in the step (4), the molar amount of Ni in the composite lithium-supplementing agent is denoted as a, the molar amount of Fe is denoted as b, the molar amount of lithium in the lithium source is denoted as c, and the terms "a", "b", and "c" satisfy the terms "c/(2a+5b) =1 to 1.3.
  8. 8. The method of claim 3, wherein the sintering temperature is 700 ℃ to 900 ℃; And/or sintering for 20-30 hours; and/or the sintering atmosphere comprises nitrogen and/or an inert gas.
  9. 9. A positive electrode sheet, characterized in that the positive electrode sheet comprises the composite lithium supplementing agent according to claim 1 or 2.
  10. 10. A lithium ion battery comprising the composite lithium supplementing agent according to claim 1 or 2 or the positive electrode sheet according to claim 9.

Description

Composite lithium supplementing agent, preparation method thereof, positive plate and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a positive electrode lithium supplementing agent, and especially relates to a composite lithium supplementing agent and a preparation method thereof, a positive electrode plate and a lithium ion battery. Background The solid electrolyte membrane (Solid Electrolyte Interphase), SEI membrane for short, is a passivation film formed by electrochemical reduction reaction of electrolyte on the surface of the negative electrode in the first charging process of the lithium ion battery. Active lithium is consumed in the process of forming the SEI film, so that the initial efficiency of the battery is reduced, and in the subsequent charge and discharge process, SEI continuous cracking and regeneration processes exist, active lithium is continuously consumed, and the cycle life of the lithium ion battery is influenced. In order to compensate for the loss of active lithium during the primary charging process, so that the capacity of the positive electrode material can be fully exerted, a lithium supplementing agent is generally used for supplementing lithium. The lithium supplementing agent generally has higher irreversible capacity, and lithium can be irreversibly released in the first charging process to compensate active lithium consumed in the process of forming the SEI film. More positive electrode lithium supplements have been studied in the prior art including lithium-rich nickel acid lithium (Li 2NiO2) and lithium-rich ferrite lithium (Li 5FeO4). The lithium-rich nickel acid lithium has the advantages of good air stability, good electronic and ionic conductivity and good multiplying power performance, can fully remove lithium without extremely small current and higher electrode, but can provide irreversible capacity of only about 300mAh/g, while the lithium-rich iron acid lithium can provide irreversible capacity close to 700mAh/g, and remarkably reduces the dosage of lithium supplementing agent, but has the problems of poor air stability, lower conductivity, poor multiplying power performance and the like, and can fully remove lithium by matching extremely small current with high voltage, and the storage environment and the lithium supplementing condition are more harsh than those of the lithium-rich nickel acid lithium. CN117727937a discloses a composite lithium-rich lithium nickelate material, its preparation method and application. The lithium-rich lithium nickelate material comprises a lithium-rich lithium nickelate material doped with metal M and polythiophene derivatives coated on the surface of the lithium-rich lithium nickelate material, wherein the molecular formula of the composite lithium-rich lithium nickelate material is Li xNiyMzO2 @PTi, x is more than or equal to 1.95 and less than or equal to 2.05,0.9 and y is more than or equal to 0 and less than or equal to 0.1, M is one or more of Mg, ti, V, mn, fe, co, cu, zn, zr, nb, mo, W, al, sn, la and Ce, and PTi represents the polythiophene derivatives. NiO is obtained through precipitation reaction of a nickel source, a precipitator and a metal dopant, the NiO is mixed with the lithium source and sintered to obtain a lithium-rich lithium nickelate material, and then the lithium-rich lithium nickelate material is coated with a polythiophene derivative solution through solvent precipitation, so that the first-ring charging specific capacity of the lithium-rich lithium nickelate material is improved. CN114050258a discloses a positive electrode lithium supplementing agent, a positive electrode sheet and a method for preparing the positive electrode lithium supplementing agent, wherein the molecular formula of the positive electrode lithium supplementing agent is Li 5FeaMbO4, a is more than or equal to 0.1 and less than or equal to 0.9, b is more than or equal to 0.1 and less than or equal to 0.9, a+b is more than or equal to 1, the element M is one or more of Ni, co, mn, cu, the center of the positive electrode lithium supplementing agent is Fe element, and the concentration gradient distribution of the element M is formed from the center to the surface of a material. According to the invention, the transition metal element is fused and doped on the surface of the large-particle-size Fe source, and the doped element migrates and diffuses to the particle core to form concentration gradient distribution in the sintering process, so that the surface stability of Li 5FeaMbO4 is improved due to the enrichment of the doped element on the surface, the surface alkalinity is low, the lithium supplementing capacity is high, and the energy density of the lithium ion battery can be effectively improved. CN118026272a discloses a preparation method of a lithium ferrite positive electrode lithium supplementing agent, which comprises the following steps of prepari