COVER PLATE ASSEMBLY, BATTERY CELL, BATTERY MODULE, BATTERY PACK AND DEVICE

A cover plate assembly, a battery cell (10), a battery module (11), a battery pack (1) and an apparatus are disclosed. The cover plate assembly (300) includes a top cover plate (310), where the top cover plate (310) is provided with an explosion-proof valve (311); and an insulating plate (320), laminated with the top cover plate (310), where the insulating plate (320) includes a base portion (321) and a thinned region (322) located on the base portion (321), the thinned region (322) is formed by thinning the base portion (321), and a region enclosed by boundaries of an orthographic projection of the thinned region (322) at least partially overlaps an orthographic projection of the explosion-proof valve (311) in a thickness direction of the cover plate assembly (300). The thinned region (322) is formed by thinning the base portion (321). Therefore, the thinned region (322) is easily softened and deformed by heat, making a through hole in the thinned region (322), thereby effectively increasing an exhaust area and ensuring normal and timely opening of the explosion-proof valve (311). The thinned region (322) corresponds to a position of the explosion-proof valve (311) in the thickness direction, so that gas can quickly arrive at the explosion-proof valve (311), and then quickly push the explosion-proof valve (311) open, effectively improving safety performance of the battery cells (10).