Wide-voltage-window silicon nanowire electrodes for micro-supercapacitors via electrochemical surface oxidation in ionic liquid electrolyte

•The use of an ionic liquid electrolyte prevents silicon etching.•Electrochemical oxidation of silicon is enabled.•Operating electrochemical window is extended up to 4 V.•Silicon nanowire electrode proven as promising electrode for micro-supercapacitor

The potential of silicon nanowires (SiNWs) as electrode material for large-voltage window micro-supercapacitors has been investigated. An ionic liquid electrolyte (EMI-TFSI) has been used in order to prevent the previously reported etching of silicon electrodes. Electrochemical oxidation of silicon surface at high anodic potentials leads to an extended operating voltage range (up to 4 V) and slightly enhanced specific capacitance of silicon electrodes. The ability of SiNW electrodes to operate at high frequency was demonstrated and a promising specific power of 472 μW cm− 2 was obtained.

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