An energy storage device and a method of fabricating such energy storage device. The energy storage device includes a first electrode, a second electrode, and an electrolyte. The combination of the electrodes and the electrolyte is arranged to elastically deform when subjected to an external mechanical load applied to the energy storage device. The electrolyte includes a polymer matrix of at least two crosslinked structures, including a first polymeric material and a second polymeric material; and an electrolytic solution retained by the polymer matrix.