In this work, we introduce a new concept to fabricate on chip, all solid-state and flexible micro-supercapacitors based on MnO_x/Au multilayers, which are compatible with current microelectronics. The micro-supercapacitor exhibits a maximum energy density of 1.75 mW h cm⁻³ and a maximum power density of 3.44 W cm⁻³, which are both much higher than the values obtained for other solid-state supercapacitors. At a scan rate of 1 V s⁻¹, a volumetric capacitance of 32.8 F cm⁻³ is obtained for MnO_x/Au multilayer electrodes, which is much higher than the bare MnO_x electrode. Electrochemical impedance spectroscopy (EIS) and evolution complex capacitance confirm that the electrical conductivity of MnO_x is improved due to the incorporation of gold, and a low relaxation time constant around 5 ms is observed. The MnO_x/Au multilayer micro-supercapacitor also shows good long-term cycling stability, with a capacitance retention rate of 74.1% after a large cycling number of 15 000 times. Compared with other supercapacitors, which are not portable and are relatively bulky, the device demonstrated here allows fast and reliable applications in a portable and smart fashion. Furthermore, the nature of the process allows the micro-supercapacitor to be integrated with other micro-devices, to meet the need for micro-scale energy storage.

Graphene prepared with p-phenylene diamine as reducing reagent was stably dispersed in ethanol, and its film, prepared by electrophoretic deposition on ITO, exhibited high conductivity.