Stable Anion-Rectifying Poly(alkoxide magnesium) Electrolytes for Reversible Magnesium Metal Batteries

The rechargeable magnesium battery (RMB) has emerged as a safe, cost-effective, and high-energy alternative to conventional batteries. Yet their practical applications have been plagued predominantly by severe Mg passivation induced by anion-triggered interfacial side reactions with Mg-metal anodes. Herein, an anion-rectifying poly(alkoxide magnesium) electrolyte with a high stability is reported. This polymer electrolyte demonstrates exceptional electrochemical performance for reversible Mg plating/stripping with a Coulombic efficiency up to 99.99%, thus enabling highly reversible cycling of the RMBs with 80% capacity retention after 1000 cycles. Furthermore, this polymer electrolyte retains its activity even after exposure to air with 33% relative humidity for 12 h. As a result, the as-assembled Mg//O 2 full batteries deliver significantly improved performance due to their high air stability. This work provides a universal design principle for stable polymer electrolytes toward highly reversible RMBs, which will significantly boost the development of high-energy RMBs.