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Recent efforts to improve zinc metal anode reversibility in aqueous electrolytes have primarily focused on tailoring Zn2+ solvation. We propose a complementary approach to directly engineer the anode interphase with the help of two co-cations. The designed organic co-cations offer distinct improvements: a partially fluorinated pyrrolidinium cation effectively suppresses parasitic reactions such as hydrogen evolution (1 year, Zn||Zn). Only 3 wt % of the co-cation combination enables full utilization of a 5-mAh cm−2 reservoir with over 99% Coulombic efficiency and 1,000 cycles with 20% reservoir utilization. We further validate this concept in Zn metal batteries with various cathode chemistries (O2, polyaniline, and HNaV6O16), and we have achieved significant enhancements in performance. This suggests co-cations are a promising and universal approach to improve metal anode reversibility across emerging battery chemistries.
Pastel et al. (Wed,) studied this question.