Battery with a flexible laminate casing includes a means for fixing the electrode assembly (2) within the casing (1, 18). The fixing means may be a frame (19, 33, 38, 50, 54) attached to the periphery of the electrode assembly, or an insulating spacer (59, 69, 70, 77, 78) encased within the casing together with the electrode assembly such as to fill a space between one end of the electrode assembly and the casing. Alternatively, the fixing means may be constructed of a material with which the casing and the electrode assembly are joined together by applying heat and pressure, or may be an abutting surface (87h) provided to the casing (87) itself such as to make contact with one end face of the electrode assembly within the casing.