Concentration polarization induced phase rigidification in ultralow salt colloid chemistry to stabilize cryogenic Zn batteries

The breakthrough in electrolyte technology stands as a pivotal factor driving the battery revolution forward. The colloidal electrolytes, as one of the emerging electrolytes, will arise gushing research interest due to their complex colloidal behaviors and mechanistic actions at different conditions (aqueous/nonaqueous solvents, salt concentrations etc.). Herein, we show “beyond aqueous” colloidal electrolytes with ultralow salt concentration and inherent low freezing points to investigate its underlying mechanistic principles to stabilize cryogenic Zn metal batteries. Impressively, the “seemingly undesired” concentration polarization at the interface would disrupt the coalescence stability of the electrolyte, leading to a mechanically rigid interphase of colloidal particle-rich layer, positively inhibiting side reactions on either side of the electrodes. Importantly, the multi-layered pouch cells with cathode loading of 10 mg cm^–2 exhibit undecayed capacity at various temperatures, and a relatively high capacity of 50 mAh g^–1 could be well maintained at −80 °C.