Highly compressible binder-free sponge supercapacitor electrode based on flower-like NiO/MnO2/CNT

The increasing demand for flexible electronics encourages the innovative and functional designs of electrode materials with high performance and compressibility. In this work, we report a compressible supercapacitor electrode which is prepared by coating electrically active NiO/MnO2/carbon nanotube (CNT) composite onto a sponge. A cube of sugar was used as the template to obtain the sponge through infiltration and cross-linking of polydimethylsiloxane (PDMS). NiO/MnO2/CNT was deposited on the PDMS sponge to generate substantial amount of interface, resulting in a specific capacitance of 23 F/g at 0.1 A /g in a three-electrode system and 1.32 F/g at 0.5 mA in a symmetric supercapacitor. The proposed system exhibits excellent cycling stability with capacitance retention over 10.000 cycles. The strong adhesion of the binary metal oxides and carbon material onto the porous nonconductive sponge enables mechanical stability under compression-release cycles. Our study indicates that this electrode is a promising candidate for applications in flexible electronics. Furthermore, this research might guide the development of flexible, high-performance, and low-cost electrodes, which will be useful in wearable energy storage systems.