One-step spray processing of high power all-solid-state supercapacitors

Aqueous suspensions of multi-wall carbon nanotubes (MWNTs) in dilute H2SO4 were sprayed onto both sides of a Nafion membrane and dried to fabricate flexible solid-state supercapacitors. A single cell with MWNT-only electrodes had a capacitance of 57 F g(-1) per electrode at 2 mV s(-1) and 44 F g(-1) at 150 mV s(-1) but with low H+ mobility. Cells with MWNT+ ionomer hybrid electrodes showed higher H+ mobility, and the electric double layer (EDL) capacitance increased to 145 F g(-1) at 2 mV s(-1) and 91 F g(-1) at 150 mV s(-1). The energy and power densities of one electrode charged to 1 V at 1 A g(-1) were 12.9 Wh kg(-1) and 3.3 kW kg(-1) respectively. Three solid-state supercapacitor cells connected in series charged to 3 V at 1 and 2 A g(-1) provided a device power density of 8.9 kW kg(-1) at 1 A g(-1) and 9.4 kW kg(-1) at 2 A g(-1), the highest for all-solid-state EDL supercapacitors.