Flexible high-capacity and long-cyclability hydrogel batteries enabled by polyvalent vanadium ion redox chemistry

Abstract

Aqueous secondary batteries based on nonflammable electrolytes are attracting extensive attention due to high safety, fast reaction kinetics, and low cost. Herein, we report the development of flexible hydrogel batteries based on polyvalent vanadium ion redox chemistry. In this battery, symmetrical composite hydrogel electrodes used as both cathode and anode are prepared by in-situ fabrication of highly porous 3D poly(N-isopropylacrylamide) scaffold alongside conductive multi-walled carbon nanotube networks and swollen with redox-active vanadium ion electrolyte. The abundant nanoscale porosity and channels in the hydrogel matrix are conducive to the infiltration/diffusion of vanadium ions and H+ ions, thus enabling high areal loading mass (13 mgv cm−2) and large areal capacity (0.99 mAh cm−2). The active materials in the flexible electrodes exist in the form of composite hydrogel state, which is beneficial to facilitate ion transport and electrochemical kinetics, delivering an impressive power density of 11 mW cm−2 at 10 mA cm−2. Moreover, the flexible vanadium ion hydrogel batteries also exhibit excellent mechanical properties and long-term durability of 1000 cycles. These merits make them promising for the applications in wearable and smart electronics.