Synergistic effect of organic-inorganic hybrid electrolyte for ultra-long Zn–I2 batteries

Hydrogel electrolytes are widely used in wearable aqueous zinc-ion batteries (ZIBs) which are considered as the most promising candidate for future energy storage systems. However, traditional organic hydrogel ions have the disadvantages of low ionic conductivity and poor mechanical properties. To conquer this, an organic-inorganic hybrid hydrogel electrolyte (PVA/CNC–C/sepiolite) is developed to improve ionic conductivity and reduce side reactions in ZIBs simultaneously. In this system, hydrogen bonds are formed between sulfonic acid groups in the polymer and the hydroxyl groups in sepiolite. The existence of these hydrogen bonds enhances the binding force between the organic and inorganic components, thus improving the ionic conductivity and mechanical properties of the electrolyte. Also, sulfonic acid groups in this hydrogel electrolyte can induce homogeneous deposition of Zn2+. The pores between the multilayer structures in sepiolite further optimize the ion transport channel and improve the transfer kinetics of Zn2+. Due to the synergistic effect of organic-inorganic compositions in this electrolyte, the Zn/Zn cell operates for more than 2000 h and Zn/I2 cell full exhibits an ultra-stable lifespan for 10,000 cycles. This work opens up a new avenue for the design of hydrogel electrolytes in ZIBs.