A supercapacitor (1) includes two like stacked supercapacitive cells (2, 3) that are connected to each other in series. A two-piece generally prismatic sealed package (4) defines an interior (5) to contain cells (2, 3). Package (4) includes a substantially planar access sidewall (6) having two spaced apart apertures (7, 8) extending from interior (5) to an exterior of the package. Sidewall (6) contains a liquid crystal polymer (LCP). A lead assembly, in the form of two spaced apart metal leads (9, 10) are electrically connected to cells (2, 3) respectively, and extend through respective apertures (7, 8) to allow external electrical connection to the cells.