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CN-122025531-A - Positive pole piece of lithium ion battery and lithium ion battery

CN122025531ACN 122025531 ACN122025531 ACN 122025531ACN-122025531-A

Abstract

The invention discloses a positive plate of a lithium ion battery and the lithium ion battery, and belongs to the technical field of lithium ion batteries. The positive electrode plate of the lithium ion battery comprises a current collector, a first active material layer arranged on at least one surface of the current collector and a second active material layer arranged on the surface of the first active material layer, wherein the first active material layer comprises lithium iron phosphate as a first positive electrode active material, the second active material layer comprises lithium nickel cobalt manganese oxide as a second positive electrode active material, the lithium iron phosphate meets the following relational expression that the concentration of the lithium iron phosphate is less than or equal to 0.5 (SSA 1 ×W 1 ) / D 50‑1 ≤4;3%≤W 1 is less than or equal to 10 percent).

Inventors

  • HUANG HAIXU
  • ZHANG CHUANJIAN
  • JU SHUYUAN
  • QIN LI
  • CHEN XIANJIN
  • HU MIN

Assignees

  • 安徽得壹能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260129

Claims (10)

  1. 1. The positive electrode plate of the lithium ion battery comprises a current collector, a first active material layer arranged on at least one surface of the current collector and a second active material layer arranged on the surface of the first active material layer, and is characterized in that the first active material layer comprises lithium iron phosphate as a first positive electrode active material, and the second active material layer comprises lithium nickel cobalt manganese oxide as a second positive electrode active material; The lithium iron phosphate satisfies the following relation that SSA 1 ×W 1 ) / D 50-1 is more than or equal to 0.5 and less than or equal to 4; Wherein SSA 1 is the specific surface area of lithium iron phosphate, the unit is m 2 /g;W 1 , the mass fraction of the first active material layer in the total mass of the first active material layer and the second active material layer is 3% or less, and the W 1 ≤10%;D 50-1 is the median particle diameter of lithium iron phosphate, and the unit is μm.
  2. 2. The positive electrode sheet of a lithium ion battery according to claim 1, wherein W 1 is 5% or less and W 1 is 10% or less.
  3. 3. The positive electrode plate of a lithium ion battery according to claim 1, wherein the specific surface area of the lithium iron phosphate is 10-22 m 2 /g.
  4. 4. The positive electrode sheet of a lithium ion battery according to claim 1, wherein the median particle diameter of the lithium iron phosphate is 0.7-2 μm.
  5. 5. The positive electrode plate of the lithium ion battery according to claim 1, wherein the chemical formula of the nickel cobalt lithium manganate is LiNi x Co y Mn 1-x-y O 2 , wherein x is more than or equal to 0.6 and less than or equal to 0.92, and y is more than or equal to 0 and less than or equal to 0.4.
  6. 6. The positive electrode plate of a lithium ion battery according to claim 1, wherein the nickel cobalt lithium manganate has a median particle diameter of 8-18 μm and a specific surface area of 0.3-1.0 m 2 /g.
  7. 7. The positive electrode sheet of a lithium ion battery according to claim 1, wherein the first active material layer further comprises a first conductive agent and a first binder, the mass ratio of the first positive electrode active material to the first conductive agent to the first binder is (94-97): 1-3): 2-4, the second active material layer further comprises a second conductive agent and a second binder, and the mass ratio of the second positive electrode active material to the second conductive agent to the second binder is (96-98): 1-3): 1-2.
  8. 8. The positive electrode sheet of a lithium ion battery according to claim 1, wherein the coating amount of the first active material layer is 5-20 g/m 2 , and the coating amount of the second active material layer is 145-165 g/m 2 .
  9. 9. A lithium ion battery characterized by comprising the positive electrode sheet of the lithium ion battery of any one of claims 1-8.
  10. 10. An electrical device comprising the lithium-ion battery of claim 9.

Description

Positive pole piece of lithium ion battery and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a positive pole piece of a lithium ion battery and the lithium ion battery. Background The information disclosed in the background of the invention is only for enhancement of understanding of the general background of the invention and is not necessarily to be taken as an admission or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art. The technical development of the lithium ion battery anode material always faces the challenge that multiple performance indexes such as energy density, safety, cycle life and the like are difficult to cooperatively optimize. The layered transition metal oxide with high nickel content (such as nickel cobalt lithium manganate) has the advantages of high specific capacity and high working voltage, and is a key material for realizing high energy density of the battery. However, as the nickel content increases, the structural stability of the material decreases, severe exothermic side reactions tend to occur under thermally or electrically abusive conditions, there is a risk of thermal runaway, and the intrinsic safety deficiency thereof becomes a bottleneck that restricts its wide application in high performance power cells. To improve the safety of high nickel positive electrode systems, industry generally contemplates the incorporation of olivine-type phosphate-based materials (e.g., lithium iron phosphate) for compounding that have better thermal stability. Common compounding strategies include bulk doping of materials, surface cladding, and physical mixing or bilayer structural design at the electrode sheet. The method improves the thermal safety of the system to a certain extent, but also introduces new technical problems that simple physical mixing can cause the mutual coupling of interface side reactions of two materials in electrolyte, and can aggravate gas production, and when different materials are arranged in a partitioning way by adopting a double-layer coating mode and the like, although functional separation can be realized theoretically, if the electrochemical characteristics (such as working voltage interval and ion/electron conductivity) and the dynamic behaviors of inner and outer layer materials are not matched properly, the transmission of lithium ions at an interlayer interface can be blocked, or the reaction progress of the two layers of materials is seriously uneven due to polarization difference under high multiplying power, and the additional side reactions can be also caused, so that the cycle life and the interface stability are damaged. Therefore, how to cooperatively improve the safety, the multiplying power performance and the cycle life of the battery by optimizing the structural design of the double-layer composite positive electrode on the basis of maintaining high energy density is a problem to be solved. Disclosure of Invention In view of the above, the invention provides a positive electrode plate of a lithium ion battery and the lithium ion battery, which realize the cooperative optimization of the morphology, the content and the function of inner-layer lithium iron phosphate and outer-layer lithium nickel cobalt manganese oxide, and cooperatively improve the rate capability, the cycle life and the thermal safety of the battery while ensuring high energy density. In a first aspect, the invention provides a positive electrode plate of a lithium ion battery, which comprises a current collector, a first active material layer arranged on at least one surface of the current collector, and a second active material layer arranged on the surface of the first active material layer; The first active material layer comprises lithium iron phosphate as a first positive electrode active material, and the second active material layer comprises lithium nickel cobalt manganese oxide as a second positive electrode active material; The lithium iron phosphate satisfies the following relation that SSA 1×W1) / D50-1 is more than or equal to 0.5 and less than or equal to 4; Wherein SSA 1 is the specific surface area of lithium iron phosphate, the unit is m 2/g;W1, the mass fraction of the first active material layer in the total mass of the first active material layer and the second active material layer is 3% or less, and the W 1≤10%;D50-1 is the median particle diameter of lithium iron phosphate, and the unit is μm. Preferably, W 1 is less than or equal to 5 and less than or equal to 10 percent of W 1. Preferably, the specific surface area of the lithium iron phosphate is 10-22 m 2/g. Preferably, the median particle size of the lithium iron phosphate is 0.7-2 μm. Preferably, the chemical general formula of the nickel cobalt lithium manganate is LiNi xCoyMn1-x-yO2, wherein x is more than or equal to 0.6 and less than or equal t