Self-chargeable zinc-ion hybrid supercapacitor driven by salt-concentrated cellulose hydrogel

The energy storage devices working without electrical grid are attractive for expanding the range of human activities. By using ZnCl2-concentrated cellulose hydrogel as electrolyte, a carbon-based zinc-ion hybrid supercapacitor (ZHS) gains a self-charging ability. The exhausted ZHS will spontaneously recover the discharge capacity by being exposed to air. After repeated “air charging”, the self-charging ability can be reactivated by charging the ZHS to 2.1 V with an external power supply. The ZHS is reliable at a high operating voltage of 2.1 V with a capacity retention of 70.9% after 2000 charge/discharge cycles. The self-chargeable ZHS is convenient for practical application because the cellulose hydrogel is stable in air as well as flexible and sustainable. This work provides new insights into the off-grid charging technologies.