A flexible and highly ion conductive polyzwitterionic eutectogel for quasi-solid state zinc ion batteries with efficient suppression of dendrite growth

Gels have gained much attention in flexible batteries. However, traditional hydrogel electrolytes are insufficient to solve the fundamental problems of zinc anodes, such as dendrite issues and parasitic side reactions, which severely restrict the development of zinc ion batteries. Here, a novel polyzwitterionic eutectogel (PSPE) is constructed with a DES (ChCl–EG–urea), zwitterionic sulfobetaine, and Zn(ClO4)2. Compared to common hydrogels, the PSPE eutectogel contains no free water, thus widening the electrochemical window and suppressing side reactions. The charged groups of the polyzwitterion can also guide the distribution of ions and promote smooth zinc deposition. Consequently, Zn//Zn cells with the PSPE eutectogel achieve a long cycle life of over 2200 h at 1 mA cm−2. At 0.2 A g−1, a full battery assembled with a V2O5 cathode and the PSPE eutectogel electrolyte can provide a high capacity of 201.8 mA h g−1. Furthermore, the flexible battery can light up LEDs under different bending angles. Besides, the low volatility of the DES and strong electrostatic interactions of zwitterionic groups allow the eutectogel to have excellent water retention. Under 60 °C unsealed conditions, the PSPE eutectogel retained 87.9% of its initial weight after 55 h. Such a highly conductive and anti-dehydration polyzwitterionic eutectogel shows promising applications in wearable energy storage devices.