▎ 摘　　要

NOVELTY - Composite polyester film comprises a first polyester layer, a second layer and a third layer of polyester, where the first and third polyester layers are respectively located on both sides of the surface of the second layer of the polyester. The raw materials for preparing the first, second and third layer polyester each independently comprise 97.0-99.9 wt.% polyester material and 0.1-3.0% additive. The terminal carboxy group content of the carboxyl group in the polyesters in the first layer and the third layer is 40-100 mol/t. USE - The composite polyester film is useful in electronic, packaging and printing applications, and in battery e.g. lithium-ion battery, lead-acid battery, nickel-cadmium battery and nickel-phosphorus battery (claimed). ADVANTAGE - The composite polyester film constructs a carboxyl-rich polar surface in the first and third polyester layers, so as to effectively improve the adhesive performance of the film, and after storing for a period of time, the film is substantially unchanged. The film has high surface tension, stable surface tension and firm surface metal layer. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) the preparation method of composite polyester film, involves (S1) preparing polyester slice one, polyester slice two and polyester slice three, independently prepared by 97-99.9 % of polyester material and 0.1-3 % of additive. The polyester slice one and polyester slice three end carboxyl content of polyester material are 40-100mol/t end carboxyl content of polyester material in the polyester slice two is 5-30 mol/t; (S2) preparing melt polyester material with first polyester layer, second polyester layer and third polyester layer, the first polyester layer, the second polyester layer and the third polyester layer sequentially cut by the polyester slice one, the polyester slice two and the polyester slice three, wherein the first polyester layer and the third polyester layer are respectively located on the surface of two sides of the second polyester layer; and (S3) forming and thermally treating the molten polyester material; (2) a metallized polyester film, comprises a metal layer and a base material layer. The metal layer has surface of the base material layer, the base material layer. The thickness of the metal layer is 20-2000nm; (3) a composite current collector, comprises metallized polyester film; (4) an electrode sheet; (5) an electrochemical device; and (6) an electric device.