Supercapacitors are attractive energy storage devices due to their high-power capabilities and robust cycle lifetimes. “Super” capacitors are named in part because the electrodes are composed of materials with high specific surface area and the distance between the electrode and electrochemical double layer is very small compared to standard capacitors. A variety of porous silicon nanowires have been developed for use as supercapacitors electrodes by maximizing the specific surface area of active materials. Although the use of Si is attractive due to its wide-spread adoption by microelectronics industry and due to its abundance, Si nanowires are highly reactive and dissolve rapidly when exposed to mild saline solutions. Previously, silicon carbide thin films were used to protect the porous silicon nanowires, but the coatings were 10’s of nm thick and while they successfully mitigated Si degradation during electrochemical cycling in aqueous electrolytes, they also resulted in pore blockage and a large decrease in energy storage potential.
Researchers at UC Berkeley have developed methods and materials to improve porous silicon nanowires by overcoming the above limitations. The resulting nanowires have an ultrathin carbon coating preserving the pore structure while mitigating Si degradation. The resulting supercapacitor electrodes have the highest capacitance (and hence energy storage) per projected area to date.
Porous silicon nanowire, supercapacitor, coating, carbon coating, ionic liquid, nanowire, battery, electrochemical capacitor, planar micro-supercapacitor