Abstract: The embodiments of the present disclosure provide an end cover, battery cell, battery, and electrical device, which belong to the field of battery technology. The end cover includes the cover body and the arc groove. The arc groove is arranged in the cover body; and the cover body is configured to crack along the arc groove to release pressure inside the battery cell when the pressure or temperature inside the battery cell reaches the threshold, wherein the depth of the arc groove gradually increases from the middle position of the arc groove to the two ends of the arc groove.

Abstract: A battery cell includes a casing configured to accommodate an electrode assembly, and a pressure relief mechanism disposed on the casing. The pressure relief mechanism includes a pressure relief passage, and a first pressure relief element and a second pressure relief element that are disposed on the pressure relief passage and close the pressure relief passage separately. In a venting direction of the pressure relief passage, the second pressure relief element is disposed upstream of the first pressure relief element and communicated with an internal space of the casing. The second pressure relief element has a rigidity of greater than or equal to 25 N/mm.

Abstract: A composite polyimide separator and a preparation method thereof, and a secondary battery are described. The preparation method of the composite polyimide separator comprises: providing a porous polyamic acid film; subjecting a diamine aqueous solution and an acyl chloride organic solution to an interfacial polymerization reaction on a surface of the porous polyamic acid film to obtain a composite polyamic acid separator; and placing the composite polyamic acid separator in vapor of an imidization reagent for imidization treatment to obtain the composite polyimide separator. In the present application, by controlling the parameters of the interfacial polymerization reaction, a composite polyamic acid separator with a dense surface, a loose bottom, and an adjustable surface pore size can be obtained.

Abstract: A battery cell, a battery, an electrical apparatus, and a method and a system for manufacturing a battery cell are provided. The battery cell comprises: a case having an opening; an electrode assembly provided within the case; an end cover assembly for closing the opening, wherein the end cover assembly comprises an end cover, an insulating member and a connection adapter member, the end cover is provided with an electrode terminal, and is configured to cover the opening and is connected to the case, the insulating member is provided on one side of the end cover facing the electrode assembly, and the connection adapter member is used for being electrically connected to the electrode terminal and to the electrode assembly; and a buffer member provided on one side of the insulating member facing the electrode assembly.