All-solid-state planner micro-supercapacitor based on graphene/NiOOH/Ni (OH)2 via mask-free patterning strategy

The development of miniaturized and portable electronic devices urgently demands the miniaturization and integration of power sources. Micro-supercapacitors have caught increasing attention in considering their special performance. Herein, we report a type of planar MSC based on the graphene network and nickel hydroxide nanoplates by chemical vapor deposition, mask-free patterning and spray-coating methods. Different interdigital width of graphene network based micro-supercapacitors are researched and the optimized micro-supercapacitor exhibits a high capacitance of 0.34 mF/cm(2) at 10 mV/s. Aiming at improving the capacitance and performance of the micro-device, NiOOH/Ni(OH)(2) nanoplates are uniformly deposited on CVD graphene surfaces to obtain all-solid-state graphene/NiOOH/Ni(OH)(2) micro-supercapacitors. This optimal micro-device displays an outstanding capacitance of 0.75 mF/cm(2) at 5 mV/s (7.54 F/cm(3)), a maximum energy density of 1.04 mWh/cm(3) and retention of 80% of its original capacity value after 3000 charge-discharge cycles. The enhancement of electrochemical performance of graphene/NiOOH/Ni(OH)(2) micro-supercapacitor is profit by the reversible redox involving two kind of phase transformation of Ni(OH)(2) and NiOOH in both positive and negative. These results demonstrate that our graphene based MSCs provide the potential as self-charging power unit for future integrated electronic applications.