A Foldable Aqueous Zn‐Ion Battery with Gear‐Structured Composite as Freestanding Cathode

Abstract

A foldable battery with high flexibility provides great potential in various wearable electronic devices for health and fitness tracking, chronic disease management, performance monitoring, navigation tracking, and portable gears for soldiers. We report a highly flexible, self-healing Znion battery with a free-standing cathode that is composed of a 3D gear-like NH 4 V 4 O 10 @C composite on carbon paper. The battery retained a capacity of up to 102.4 mAh g À 1 even after being folded 60 times with a high angle of 180°. An aqueous hydrogel consisting polyvinyl alcohol, glycerin and Zn-(CF 3 SO 3 ) 2 was used as electrolyte, which showed as high as 580 % tensile strain under a loading weight of 78 N. The battery exhibited a better capacity retention of over 100 mAh g À 1 and Coulombic efficiency of over 99.8 % after cutting and twisting to 90°, thereby indicating a great selfhealing performance. The gear-like geometry greatly improved the volume accommodation due to the increased interval space between the blades and the outward configuration. Meanwhile the Zn 2 + ionic conductivity was improved by rapid re-binding of many existing hydroxy groups from the electrolyte and the enhanced contact surface area and diffusion route from the cathode material. The highly flexible, safe aqueous Zn-ion battery opens a practical way to power various carry-on electronics under mechanical agitation.

Effect of MnO2 Morphology on Kinetics and Stability in Zinc-Ion Batteries

“…1−6 They show great promise in the fields of energy storage and electric vehicles. 7,8 The typical cathode materials used for ZIBs are vanadium oxides, manganese oxides, Prussian blue analogues, and metal sulfides. 9−14 Among them, MnO 2 has attracted significant attention because of its natural abundance, low cost, and high theoretical capacity (308 mAh g −1 ).…”

“…Water-based zinc-ion batteries (ZIBs) are considered promising candidates for an ideal green battery system because of their high power and energy densities, high-current charging and discharging, low cost, safety, and environmental compatibility. − They show great promise in the fields of energy storage and electric vehicles. , The typical cathode materials used for ZIBs are vanadium oxides, manganese oxides, Prussian blue analogues, and metal sulfides. − Among them, MnO 2 has attracted significant attention because of its natural abundance, low cost, and high theoretical capacity (308 mAh g –1 ). − However, research on manganese-derived water-based ZIBs has been hindered by their poor cycle stability. − Therefore, improving the stability of ZIBs is an important issue in the industry.…”