Patent ID: 11929492
Assignee: CONTEMPORARY AMPEREX TECHNOLOGY CO., LIMITED
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 14:
15. A method for preparing a lithium-ion secondary battery, at least comprising following steps:
S1, applying a positive electrode slurry comprising a first positive electrode active material, a conductive agent and a binder on at least one surface of a positive electrode current collector, to form a first positive electrode active material layer;
S2, applying a positive electrode slurry comprising a second positive electrode active material, a conductive agent and the binder on the first positive electrode active material layer, to form a second positive electrode active material layer;
S3, drying to obtain a positive electrode plate comprising the positive electrode current collector and the first positive electrode active material layer and the second positive electrode active material layer sequentially disposed on at least one side of the positive electrode current collector;
S4, sequentially laminating the positive electrode plate, a separator and a negative electrode plate and then winding or pressing to obtain an electrode assembly, then injecting an electrolyte, and packaging, to obtain a secondary battery;
wherein, the lithium-ion secondary battery satisfies formula (I):

0.05≤log10(u/v)×w≤15.5  formula (I)

wherein,
u is a thickness of the first positive electrode active material layer in microns,
v is a thickness of the second positive electrode active material layer in microns,
w is a conductivity of the electrolyte at a temperature of 25° C. in mS·cm−1, and
wherein the first positive electrode active material layer comprises a first positive electrode active material being the compound of formula (II),

Li1+xNiaCobM1-a-bO2-yAy  formula (II)

wherein, −0.1≤x≤0.2, 0.7≤a<1, 0<b<1, 0<a+b<1, 0≤y<0.2, M is one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr and Ce, and A is one or more of S, F, Cl and I, and
the second positive electrode active material is one or more of lithium manganate, lithium iron phosphate, lithium vanadate and lithium nickel manganese oxide, and wherein ratio of the thickness u of the first positive electrode active material to the thickness v of the second positive electrode active material is u/v≥5.