Non-passivating Anion Adsorption Enables Reversible Magnesium Redox in Simple Non-nucleophilic Electrolytes

Abstract

Magnesium batteries suffer from low power density and poor cycle life due to severe Mg passivation. Using nucleophilic electrolytes is effective to stabilize the Mg anode, but it prohibits the use of organic and conversion cathodes due to chemical reactivity. Here, we report an effective non-passivating anion additive, the reduced perylene diimide–ethylene diamine (rPDI), to enable fast and reversible Mg deposition/dissolution in a simple non-nucleophilic electrolyte. The rPDI additive exhibits higher adsorption energy than the TFSI– salt on the Mg surface, preventing TFSI– decomposition and Mg anode passivation. Using 0.2 mM rPDI additives, we demonstrated a Mg–organic full cell achieving a high power density (2.0 mW cm–2) and a stable cycle life (>200 cycles). Our study provides a facile and effective strategy for non-nucleophilic electrolytes, enabling the combination of Mg anode with a wide variety of organic and conversion cathodes beyond intercalation chemistries.