Modified Solid Electrolyte Interphases with Alkali Chloride Additives for Aluminum–Sulfur Batteries with Enhanced Cyclability

Abstract Aluminum–sulfur batteries employing high‐capacity and low‐cost electrode materials, as well as non‐flammable electrolytes, are promising energy storage devices. However, the fast capacity fading due to the shuttle effect of polysulfides limits their further application. Herein, alkaline chlorides, for example, LiCl, NaCl, and KCl are proposed as electrolyte additives for promoting the cyclability of aluminum–sulfur batteries. Using NaCl as a model additive, it is demonstrated that its addition leads to the formation of a thicker, Na_xAl_yO₂‐containing solid electrolyte interphase on the aluminum metal anode (AMA) reducing the deposition of polysulfides. As a result, a specific discharge capacity of 473 mAh g⁻¹ is delivered in an aluminum–sulfur battery with NaCl‐containing electrolyte after 50 dis‐/charge cycles at 100 mA g⁻¹. In contrast, the additive‐free electrolyte only leads to a specific capacity of 313 mAh g⁻¹ after 50 cycles under the same conditions. A similar result is also observed with LiCl and KCl additives. When a KCl‐containing electrolyte is employed, the capacity increases to 496 mA h g⁻¹ can be achieved after 100 cycles at 50 mA g⁻¹. The proposed additive strategy and the insight into the solid electrolyte interphase are beneficial for the further development of long‐life aluminum–sulfur batteries.