The invention provides a lithium-ion power battery diaphragm, a preparation method thereof and a lithium-ion power battery. The lithium-ion power battery diaphragm comprises a microporous basement membrane, wherein a coating slurry layer is coated on at least one side of the microporous basement membrane. The coating slurry layer comprises the following components by weight percent: 10-25% of chemical binder, 1-3% of thickening agent, 25-55% of abrasive slurry, 0.1-0.3% of defoaming agent, 0.1-0.3% of wetting agent, 0.1-0.3% of dispersing agent and 0.1-0.3% of levelling agent. The lithium-ion power battery diaphragm, the preparation method and the lithium-ion power battery have the beneficial effects that the costs of the abrasive slurry and coating slurry can be greatly reduced by adopting cheap silicon carbide as a main raw material of the abrasive slurry or the coating slurry

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