Transient batteries are expected to lessen the inherent environmental impact of traditional batteries that rely on toxic and critical raw materials. This work presents the bottom-up design of a fully transient Zn-ion battery (ZIB) made of nontoxic and earth-abundant elements, including a novel hydrogel electrolyte prepared by cross-linking agarose and carboxymethyl cellulose. Facilitated by a high ionic conductivity and a high positive zinc-ion species transference number, the optimized hydrogel electrolyte enables stable cycling of the Zn anode with a lifespan extending over 8500 h for 0.25 mA cm-2 - 0.25 mAh cm-2 . On pairing with a biocompatible organic polydopamine-based cathode, the full cell ZIB delivers a capacity of 196 mAh g-1 after 1000 cycles at a current density of 0.5 A g-1 and a capacity of 110 mAh g-1 after 10 000 cycles at a current density of 1 A g-1 . A transient ZIB with a biodegradable agarose casing displays an open circuit voltage of 1.123 V and provides a specific capacity of 157 mAh g-1 after 200 cycles at a current density of 50 mA g-1 . After completing its service life, the battery can disintegrate under composting conditions.
Keywords: aqueous electrolytes; biopolymers; degradation; green batteries; hydrogel electrolytes; transiency; zinc-ion batteries.
© 2022 The Authors. Small published by Wiley-VCH GmbH.