Nanostructured Polyaniline–Cellulose Papers for Solid-State Flexible Aqueous Zn-Ion Battery

Solid-state flexible aqueous Zn-ion battery was fabricated with nanostructured polyaniline–cellulose papers as the cathode and Zn-grown graphite papers as the anode. The separator was a flexible gel electrolyte with high ionic conductivity, based on cellulose nanofibers. The Zn-ion battery exhibited energy density of 117.5 and 67.8 mW·h/g at power density of 0.16 and 3.34 W/g, respectively (estimated from total active mass of both cathode and anode). The energy density of the Zn-ion battery was much higher than that of asymmetric supercapacitors with aqueous electrolytes, while maintaining a comparable power density. Meanwhile, good cyclic stability was achieved with a high capacity retention of 84.7% after 1000 charge/discharge cycles at a current density of 4 A/g. More importantly, specific capacity changed little under mechanical bending, and there was only 9% loss after 1000 bending cycles. The solid-state flexible Zn-ion battery has great potential as an energy-storage device for flexible displays and wearable electronics.