A sustainable chitosan-zinc electrolyte for high-rate zinc-metal batteries

Rechargeable aqueous Zn-metal battery is promising for grid energy storage needs, but its application is limited by issues such as Zn dendrite formation. In this work, we demonstrate a Zn-coordinated chitosan (chitosan-Zn) electrolyte for high-performance Zn-metal batteries. The chitosan-Zn electrolyte exhibits high mechanical strength, Zn2+ conductivity, and water bonding capability, which enable a desirable Zn-deposition morphology of parallel hexagonal Zn platelets. Using the chitosan-Zn electrolyte, the Zn anode shows exceptional cycling stability and rate performance, with a high Coulombic efficiency of 99.7% and >1,000 cycles at 50 mA cm−2. The full batteries show excellent high-rate performance (up to 20C, 40 mA cm−2) and long-term cycling stability (>400 cycles at 2C). Furthermore, the chitosan-Zn electrolyte is non-flammable and biodegradable, making the proposed Zn-metal battery appealing in terms of safety and sustainability, demonstrating the promise of sustainable biomaterials for green and efficient energy-storage systems.