Asymmetric Mn 2+ Cluster Electrolyte for High‐Performance Mn‐Metal Batteries

Abstract Due to the high natural abundance and low redox potential, Mn metal is an attractive anode material for post‐Li batteries. A key challenge of Mn‐metal batteries (MnMBs) lies at the unsatisfying ionic conductivity of the present non‐aqueous electrolyte. In this work, an asymmetric tetramethylene sulfone (TMS)‐coordinated Mn 2 (µ‐Cl)Cl 2 (TMS) x (TFSI) y n + (TFSI: bistrifluoromethanesulfonimide) cluster electrolyte is reported for MnMBs. Benefitting from the asymmetric solvation structure of Mn 2+ and high‐dielectric constant TMS, the concentration is improved over 1 m with a high ionic conductivity of 4.68 mS cm −1 . Impressively, reversible Mn plating‐stripping is realized under high current rates (up to 8 mA cm −2 ), high areal capacity (1–10 mAh cm −2 ), and even in a wide temperature range (−40 to 60 °C). The electrolyte composition is parsed as TMS‐coordinated Mn 2 Cl 3 + , AlCl 2+ , AlCl 2 + , and Al(TFSI) 3 Cl − . A hybrid MnMBs is thus proposed based on AlCl 2+ insertion/extraction at an organic cathode and Mn plating‐stripping. The hybrid battery delivers a specific capacity over 100 mAh g −1 , a high output voltage of 1.0 V, excellent rate performance and a long cycle life (>2000 cycles) at both low and high temperatures (−30 and 60 °C), much superior over state‐of‐the‐art MnMBs. The work demonstrates the significance of the cluster structure of Mn 2+ and their influence on Mn‐ion electrolyte and MnMBs.