A Flexible Aqueous Asymmetric Lithium-Ion Supercapacitor with High Voltage and Superior Safety

Achieving high voltage and safety simultaneously in energy storage devices can greatly advance the development of flexible and wearable electronics. Thus, flexible aqueous asymmetric lithium-ion supercapacitors with a high voltage attract the interest of many researchers. Herein, a new flexible aqueous asymmetric lithium-ion supercapacitor with a high voltage and superior safety is fabricated using manganese oxide and iron hydroxide, which are electrodeposited on carbon cloths as electrodes and a super-concentrated gel polymer as the electrolyte. Impressively, the flexible asymmetric lithium-ion supercapacitor delivers a high voltage of 3.2 V, which is a high value in aqueous asymmetric supercapacitors. Moreover, the asymmetric supercapacitor exhibits a specific capacitance of 227.6 F g⁻¹, a maximum energy density of 49.3 Wh kg⁻¹, and a maximum power density of 11.5 kW kg⁻¹, together with a capacitance retention of 82% after 1000 cycles at a current density of 2 A g⁻¹. Importantly, the supercapacitor can keep good electrochemical performance under extremely harsh conditions, such as compressing, hammering, punching, and tailoring, which demonstrates superior safety.