A high-energy-density micro supercapacitor of asymmetric MnO ₂-carbon configuration by using micro-fabrication technologies

This paper demonstrates an asymmetric micro supercapacitor with superior overall performance that combines the advantages of both MnO₂ positive electrode and carbon negative electrode for energy storage on a chip. Nano-structured MnO₂ with rough surface is synthesized as active material for micro electrode. A self-supporting composite containing MnO ₂ and another containing nanoporous activated carbon (AC) are separated in an interdigital structure by using micro-electro-mechanical systems (MEMS) fabrication technologies. Measurements of the prototype show that the asymmetric micro supercapacitor has well-performed capacitive behavior, and its working voltage range is extended from 1 V to 1.5 V in aqueous electrolyte due to the MnO₂-AC configuration. Calculations prove that it stores much higher energy densities than symmetric ones using either MnO₂ or AC. Moreover, this work provides an attractive approach to achieve various asymmetric micro energy storage systems on chips.