A dual-electrolyte rechargeable Li-air battery with phosphate buffer catholyte

A novel dual-electrolyte rechargeable Li-air cell, consisting of lithium metal anode in an aprotic electrolyte, an air electrode in an aqueous phosphate buffer catholyte, and a NASICON-type lithium-ion conducting solid electrolyte (Li_{1 + x + y}Al_xTi_2 − xSi_yP_3 − yO₁₂ or LTAP) separator, has been investigated. The solid electrolyte separates the aprotic electrolyte from the aqueous catholyte, while providing pathways for lithium-ion transport. The phosphate buffer solution with a moderate pH helps to keep the solid electrolyte stable and reduces internal resistance and overpotential, while enabling a rechargeable Li-air cell with a high operating voltage and energy density. The Li-air cell exhibits a discharge capacity of 221 mAh g^− 1 at a current density of 0.5 mA cm^− 2 with good cycle life.