Synergestic effect of magnetron sputtered silver nano-islands and Co3(PO4)2 for high performance supercapattery devices

•The synergetic effect of magnetron sputtered Ag and cobalt phosphate.•Electrochemical performance was investigated in three electrode assembly.•Supercapattery device is fabricated comprises of Ag-Co3(PO4)2.•Specific energy of 65.8 Whkg-1 with a maximum specific power of 6012 Wkg-1.•Capacitive and diffusion-controlled contribution in device is investigated.