Separation film for lithium secondary battery having adhesive layer

Abstract

The present invention relates to a coating composition, comprising a solvent, inorganic particles, a dispersant, and a binder, for coating at least one surface of a porous substrate having a plurality of pores. The binder comprises binder B and binder A, wherein the binder B and the binder A both contain a vinylidene fluoride (VDF)-derived unit and a hexafluoropropylene (HFP)-derived unit. The HFP-derived unit accounts for 8% to 50% by weight of the binder B, and in the binder A, the HFP-derived unit is not more than 80% of the proportion thereof in the binder B and is not less than 5% by weight of the binder A. The total number average molecular weight of the binder B is 200,000 to 2,000,000, and the total number average molecular weight of the binder A is 70% or less of that of the binder B. The weight ratio of binder A: binder B in the total coating composition is 0.1 to 10: 1. The present invention has resolved the problem that when a binder is thinned from 4 to 3 , the binder is dried before being sufficiently phase-separated and thus a sufficient electrode adhesive force cannot be obtained, and also in terms of a manufacturing method, the present invention has provided a coating composition in which sufficient phase separation occurs even in a low-humidity condition.

Description

technical field [0001] The present invention relates to a coating composition for a separator of a lithium secondary battery comprising an adhesive layer, and more particularly to a coating composition suitable for coating at least one surface of a separator of a porous substrate having a plurality of pores thereon, for comprising A coating composition for a lithium secondary battery separator of an adhesive layer. Background technique [0002] As the recent trend is to reduce weight and increase functions of portable devices such as smartphones, notebook computers, tablet computers, and portable game consoles, the demand for secondary batteries to be used as a driving power source for these portable devices is increasing. In the past, nickel-cadmium, nickel-hydrogen, and nickel-zinc batteries have been used, but lithium secondary batteries having a high operating voltage and high energy density per unit weight are most commonly used at present. [0003] A problem with lith...

AI Technical Summary

Problems solved by technology

In particular, when the coating thickness of the separator is reduced from 4 μm to 3 μm (based on the cross-section), the coating composition of the present invention can solve the problem of not obtaining sufficient electrodes due to the drying of the binder before sufficient phase separation. problem of stickiness and is able to achieve sufficient phase separation even at the low humidity of the manufacturing method

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