Compressible zinc-ion hybrid supercapacitor and piezoresistive sensor based on reduced graphene oxide/polypyrrole modified melamine sponge

Abstract

Compressible energy storage devices are very promising in wearable electronics owing to their stable performance under different compressed strains. Melamine sponge (MS) is modified by reduced graphene oxide (rGO) and polypyrrole (PPy) to obtain the compressible positive electrode (PPy/rGO@MS) in this work. Then a compressible zinc-ion hybrid supercapacitor (CZHS) with a novel construction is designed by sandwiching the PPy/rGO@MS positive electrode between two Zn foils to improve the utilization of active materials. The CZHS with an operating voltage within 0.2–1.8 V exhibits high specific capacity of 129.8 mAh g−1, energy density of 103.8 Wh kg−1, capacity retention of 72.0% after 15,000 GCD cycles. Besides, capacity retention of the CZHS is 90.9% after 3000 compression/release cycles with a compressive strain of 40%. The results indicate the CZHS has both outstanding electrochemical performance and high compressibility. The charge storage mechanism of the Zn//PPy/rGO@MS system is also investigated by electrochemical analysis and density functional theory. Taking advantage of the compressibility and sensitive resistance change of the PPy/rGO@MS composite, a piezoresistive sensor with similar construction as the CZHS is fabricated. This work provides an effective strategy for fabricating compressible energy storage device and piezoresistive sensor with high performance.