Synergistic effects of modulating electrical double layer structure and facilitating uniform deposition of Zn2 + by biocompatible polysaccharide additive for high-performance aqueous zinc ion batteries

Abstract

Dendrite growth and uncontrollable side reactions considerably restrict the development of aqueous zinc-ion batteries (AZIBs). In this study, chitosan (CTS), an inexpensive, biocompatible, and biodegradable polysaccharide biopolymer, is introduced to enhance the electrochemical properties of AZIBs through manipulation of electrical double layer adsorption and improvement of Zn deposition behavior. Theoretical calculations and experimental analyses show that CTS with a rich hydroxyl structure regulates the adsorption of the electrical double layer and the hydrogen-bonding network among water molecules, thereby influencing preferential binding and deposition behavior of Zn²⁺. Owing to synergistic effects of redistributed solvated layer surrounding Zn²⁺ and inhibited excessive growth of Zn dendrites, the electrochemical performance is significantly enhanced. The Zn||Zn symmetric battery with CTS additives demonstrates stable cycling performance for 1650 h (825 cycles) at 0.5 mA cm⁻² and 0.5 mAh cm⁻², which is eight times longer than that of the battery without additives. So, the assembled Zn||MnO₂ full cells exhibit remarkable cycling stability, high specific capacity and superb rate capability. This work may shed light for the development of high-performance AZIBs.