A multifunctional electrolyte additive for zinc-ion capacitors with low temperature resistant and long lifespan

Aqueous zinc-ion capacitors (ZICs) are considered as potential candidates for next generation electrochemical energy storage devices due to their high safety and low cost. However, the existing aqueous ZICs usually have the problems of zinc dendrite growth and unsatisfactory performance at low temperature. Herein, an erythritol (Eryt) additive with inhibition of zinc dendrites and anti-freezing capability was introduced into the ZnSO4 electrolyte. The experimental characterization and theoretical calculation confirm that the Eryt adsorbed on the surface of zinc anodes regulates the deposition orientation of Zn2+ and inhibits the formation of dendrites. It also reconstructs the solvation structure in the electrolyte to reduce water activity, enabling the electrolyte to have a lower freezing point for operation at low temperature. With the assistance of Eryt, the Zn||Zn symmetric cell exhibits a long cycle life of 2000 h, while the ZIC assembled with activated carbon (AC) cathode and zinc anode (Zn||AC) maintains a capacity retention of 98.2% after 30000 cycles at a current density of 10 A g−1 (even after 10000 cycles at −20 °C, the capacity retention rate reached 94.8%.). This work provides a highly scalable, low-cost and effective strategy for the protection of the anodes of low-temperature aqueous ZICs.