Ligand-channel-induced ion liberation in crowded zwitterionic hydrogel electrolyte for efficient zinc metal batteries

Developing efficient electrolytes is vital for realizing the vision of aqueous rechargeable zinc-metal batteries as a safe and sustainable energy storage technology. Emerging electrolyte engineering approaches including concentrated and molecular crowding electrolytes restrict water reactivity but usually incur limited bulk ionic conductivity and sluggish interfacial kinetics as well. Here we show that this dilemma can be addressed by deploying hydrogel electrolytes that incorporate typical molecular crowding electrolytes with a zwitterionic polymer matrix. This crowded zwitterionic hydrogel electrolyte counterintuitively entails Zn²⁺ liberation for higher ionic conductivity and prompt interfacial desolvation kinetics while maintaining essential advantages of molecular crowding electrolytes, thereby fundamentally overcoming the critical issues associated with such electrolytes. Such electrolytes enable the assembled zinc-metal batteries and zinc-ion hybrid capacitors to work effectively and stably at high rates (up to 5 A g^-1) and frozen temperatures (down to -60°C). The applicability of this crowding-induced ion liberation strategy was also extended to other aqueous metal-ion (Mg²⁺ and Na⁺) batteries. This work has the potential to provide a general solution to efficient electrolytes for safer, energy-dense, and cost-effective aqueous energy storage technologies.