TECHNOLOGY FOCUS - ELECTRONICS - Preferred Parameters: In the rechargeable battery, the insulating member (30, 41, 42, 43, 50), when folded, matches the shape of the case. The shape of the surface of the insulating member (30, 41, 42, 43, 50) being in contact with the electrode assembly (15) is designed to correspond to the outer shape of the electrode assembly (15). The supporting part (32a, 52a; 34a, 54a) comprises at least one of the following features: the supporting part is closely attached to the flat part (15a) of the electrode assembly (15) and supports the electrode assembly (15); is shaped to have a buffering groove (52b) adapted to allow expansion of the battery; is flat in the region where it contacts the flat part (15a) of the electrode assembly (15); is tilted or curbed in an arc shape where it contacts the convex part (15b) of the electrode assembly; and has a trapezoid-shaped cross-section. The insulating member (30, 41, 42, 43, 50) has the form of a cuboid with the top open. The third insulating plate (36, 56) and the fourth insulating plate (38, 58) are of planar shape. The base (31, 51): has a quadrangular shape; and/or is provided with an arc-shaped top surface in the region of contact with the bottom of the electrode assembly (15); and/or is closely attached to the bottom of the case (14). Preferred Components: The supporting parts (32a, 52a; 34a, 54a) comprise film sheets laminated together. The insulating member (30, 41, 42, 43, 50) comprises a groove (35) on the boundary between the base (31) and the insulating plates (32, 34, 36, 38), the groove (35): being provided on the top of the surface of the base (31) facing the electrode assembly (15) or on the bottom of the surface of the base (31) facing the case (14); and/or having a triangular cross-section; and/or having a quadrangular cross-section. The battery further comprises a first terminal (21) and a second terminal (22), the first terminal (21) being connected to the first electrode (11) via a first lead tab (21 a), the second terminal (22) being connected to the second electrode (12) via a second lead tab (22a), where the third insulating plate (36, 56) is disposed between the first lead tab (21a) and the case (14) and the fourth insulating plate (38, 58) is disposed between the second lead tab (22a) and the case (14).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The insulating member (30, 41, 42, 43, 50) is formed of one selected from poly propylene, poly ethylene, poly phenyl sulfate, poly butylene terephthalate, poly tetrafluoro ethylene, perfluoroalkoxy, fluorinated ethylene propylene, poly vinylidene fluoride. EXAMPLE - No example given.