In situ formation of graphene/metal oxide composites for high-energy microsupercapacitors

The current design trends in the field of electronic devices involve efforts to make these devices smaller, thinner, lighter, and more flexible. The development of such systems is expected to further accelerate, resulting in the production of wearable and Internet-of-Things devices. In this respect, microenergy storage systems with high capacity and fast charge/discharge rates have become important power sources for such devices. In particular, interdigitated microsupercapacitors (MSCs) have exhibited remarkable potential as micropower sources owing to their fast charge/discharge processes, long cycle life, and high power density compared with microbatteries. Nevertheless, facile fabrication of MSCs using interdigitated electrodes remains challenging, as it requires selective decoration of electrodes with pseudocapacitive materials, such as transition metal oxides, to increase their capacitance. In the present study, we developed a simple method for fabricating MSCs involving in situ formation of interdigitated graphene electrodes and ZnO nanorods by photothermal conversion of graphene oxide (GO) and Zn precursors using infrared (IR) laser scribing. The fabricated MSCs exhibit a high stack capacitance of 3.90 F cm−3 and an energy density of 0.43 mWh cm−3. Notably, the capacity of the developed material is three times higher than those of previously reported MSCs made from the same type of graphene. In addition, the capacitance retention rate of the fabricated MSC is approximately 70% when measured over 10,000 charging–discharging cycles at a constant current, which evidently indicates a stable device performance. Researchers in South Korea have developed a method for making tiny high-capacity energy storage devices. Portable electronic devices rely on light-weight sources of energy. Lithium ion batteries are the prevailing technology, but alternatives are being developed. Supercapacitors, for example, offer faster charging time and a longer life. Supercapacitors can be miniaturized by interlocking the electrodes, but such devices are difficult to fabricate. Junghyo Nah from the Chungnam National University, Daejeon, Min Hyung Lee from Kyung Hee University, Yongin, and colleagues have developed a simple method for making microsupercapacitors from graphene electrodes and zinc oxide nanorods. The capacity of their device was three times higher than that of previous microsupercapacitors built from the same type of graphene. The results could contribute to development of smaller, thinner and lighter power sources. Selective growth of ZnO nanorods/reduced graphene oxide composites via IR laser-induced reaction is developed for electrochemical devices. Optimized design of interdigitated supercapacitor electrodes can be achieved by programming of laser scanning lines. The integration of ZnO NRs on rGO improves supercapacitor performances due to synergistic effects of pseudo capacitance (ZnO) and electric double layer capacitance (graphene).