Lithium battery separator and lithium battery

Abstract

The present invention relates to the technical field of lithium batteries, and particularly relates to a lithium battery separator and a lithium battery. The separator comprises a block polymer, the porosity of the separator is p, the mass percentage of the block polymer relative to the separator is w, and the relationship between the porosity p of the separator and the relative mass percentage w of the block polymer satisfies: (1 - w) / 3 < p < 25%. For the lithium battery separator of the present invention, by adding the block polymer, the separator can also achieve its own functions under the condition of a relatively small porosity, having good lithium ion conduction characteristics, reducing the thermal shrinkage rate of the separator, and improving the safety performance.

Claims

1. A lithium battery separator, characterized in that, The separator includes a block polymer, the porosity of the separator is p, the mass percentage of the block polymer relative to the separator is w, and the mass percentage w of the block polymer relative to the separator is w > 40%; the relationship between the mass percentage w of the block polymer relative to the separator and the porosity p of the separator satisfies: (1 - w) / 3 < p < 25%; the block polymer includes a flexible block A and a rigid block B, and the structure of the block polymer is A n B m 、A n B m A n or B m A n B m ; The structural formula of the flexible block A is: ； Wherein, R1 is a hydrocarbon group with an unsaturation degree not higher than 1, and the molecular weight W1 of R1 satisfies 28≤W1≤108; The structural formula of the rigid block B is: or ; R2 is one of hydrogen, a hydrocarbon group or halohydrocarbon group with a molecular weight not exceeding 45, or a saturated ester group; R3 is one of hydrogen, a hydrocarbon group or haloalkyl group with a molecular weight not exceeding 45, a cyclic unsaturated hydrocarbon group, or an aliphatic hydrocarbon group.

2. The lithium battery separator according to claim 1, characterized in that, The weight-average molecular weight W of the flexible block A a The weight-average molecular weight W of the rigid block B b The condition is satisfied that: 0.25 ≤ W a / W b ≤5.

3. The lithium battery separator according to claim 2, characterized in that, The weight-average molecular weight W of the flexible block A a Satisfying 8≤W a ≤100, in ten thousand; the weight-average molecular weight W of the rigid block B. b Satisfying 10≤W b ≤150, in ten thousand.

4. The lithium battery separator according to claim 3, characterized in that, The thickness d of the diaphragm satisfies 3 ≤ d ≤ 20, and the unit is μm; the weight-average molecular weight W of the flexible block A is... a The thickness d of the diaphragm satisfies 3 ≤ W a / d≤25.

5. The lithium battery separator according to any one of claims 1-4, characterized in that, The surface of the diaphragm is further coated with ceramic powder or polymer adhesive; the ceramic powder includes one or more of alumina and boehmite; the polymer adhesive includes one or more of PVDF, PMMA, and PAN.

6. A lithium battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator according to any one of claims 1-5.

7. The lithium battery according to claim 6, characterized in that, The electrolyte comprises cyclic carbonates.

8. The lithium battery according to claim 7, characterized in that, The cyclic carbonate has a mass percentage u > 15% relative to the electrolyte, and the cyclic carbonate is selected from any one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, vinylene carbonate, and difluoroethylene carbonate.

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