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.
Aqueous zinc‐ion hybrid capacitors (ZHCs) are considered ideal energy‐storage devices. However, the common aqueous Zn2+‐containing electrolytes used in ZHCs often cause parasitic reactions during charging–discharging owing to free water molecules. Hydrated eutectic electrolytes (HEEs) that bind water molecules through solvation shells and hydrogen bonds can be applied at high temperatures and within a wide potential window. This study reports a novel bimetallic HEE (ZnK–HEE), consisting of zinc chloride, potassium chloride, ethylene glycol, and water, which enhances the capacity and electrochemical reaction kinetics of ZHCs. The bimetallic solvation shell in ZnK‐HEE is studied by molecular dynamics and density functional theory, confirming its low step‐by‐step desolvation energy. A Zn//activated carbon ZHC in ZnK–HEE shows a high operating voltage of 2.1 V, along with an ultrahigh capacity of 326.9 mAh g−1, power density of 2099.7 W kg–1, and energy density of 343.2 Wh kg–1 at 100 °C. The reaction mechanisms of charging–discharging process are investigated by ex situ X‐ray diffraction. This study reports a promising electrolyte for high‐performance ZHCs, which exhibits high‐temperature resistance and is operable within a wide potential window.
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