Quaternary ammonium ionic liquid as inhibitor enhancing the discharge performance for Mg-air battery

[N₁₈₈₈][NTf₂] serves as a bifunctional electrolyte additive for Mg–air batteries. • [N₁₈₈₈][NTf₂] forms a hydrophobic, MgF₂-containing interfacial layer on Mg. • DFT and MD simulations reveal preferential and stable adsorption on Mg(0001). • The protective effect is concentration-dependent, with an optimum at 1 mM. • The cell delivers 1853.3 Wh·kg⁻¹ and a discharge duration of 123.3 h. Mg-air batteries are limited by severe self-corrosion of the magnesium anode and accumulation of discharge products, leading to reduced anode utilization and discharge voltage. This study introduces the ionic liquid [N₁₈₈₈][NTf₂] as a bifunctional electrolyte additive to regulate the magnesium/electrolyte interface. The long alkyl chain of [N₁₈₈₈]⁺ forms a hydrophobic barrier, restricting water access to the magnesium surface and inhibiting magnesium self-corrosion; [NTf₂]⁻ coordinates with Mg²⁺, slowing the accumulation of discharge products. This complementary cation-anion regulation achieves a balance between inhibiting corrosion and maintaining effective dissolution of the magnesium anode. The full cell achieved a discharge voltage of 1.45 V and a specific energy of 1853.3 Wh·kg⁻¹ at 5 mA·cm⁻²; at 10 mA·cm⁻², the discharge time reached 123.3 h, approximately seven times that of the blank electrolyte. This work provides an ion-specific interface regulation strategy for improving magnesium anode utilization and the discharge performance of MABs. Download: Download high-res image (331KB) Download: Download full-size image