Abstract
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 MnO2 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. (c) 2013 Elsevier B.V. All rights reserved.