The present application provides a battery cell including a first electrode, a second electrode, and a separator disposed therebetween, wherein the separator comprises an extension portion beyond the first electrode and the second electrode at an end portion of the battery cell. The battery cell further includes an adhesive layer including a body and a connecting portion extending from the body. The body is adhered to the extension portion, and the connecting portion is adhered to the extension portion. It is an object of the present application to provide a battery cell that effectively eliminates invalidation resulted from short circuit caused by the separator shrinkage. The present application further provides an electrochemical device and a method of manufacturing thereof.