A universal in situ strategy for charging supercapacitors

Abstract

In the studies of supercapacitors (SCs), most efforts are focused on improving their electrochemical performances. However, in order to further promote SCs as widely used and reliable power supplies for electronics, how to charge them more effectively and conveniently should be considered. This work demonstrates a universal in situ charging strategy based on planar interdigital SCs. This strategy can be applied to different kinds of SCs without complicating them or obviously increasing their volumes. In situ charging was realized by simply adding a piece of Zn foil to one electrode of the SC and then the electrodes play a dual role as both a SC and a chemical cell. A carbon nanotube (CNT) electrode modified with silicone rubber can form a stable metal–air cell with Zn foil to charge the SC in situ. The charging process is activated when a drop of solution/water is added between the Zn anode and carbon cathode. The SC can be in situ charged to 1.0 V and its energy density is 3.92 μW h cm⁻² based on the whole device, including the cell part. The SC can be charged repeatedly and higher voltage is attainable when several SCs are assembled into a compact one. To extend its feasibility, charging the SC with moisture is also demonstrated.