Reversible Hybrid Aqueous Li-CO Batteries with High Energy Density and Formic Acid Production.

Metal-CO batteries, an attractive technology for both energy storage and CO utilization, are typically classified into organic Li(Na)-CO batteries with a high energy density/output voltage and aqueous Zn-CO batteries with flexible chemical production. However, achieving both high-efficiency energy storage and flexible chemical production is still challenging. In this study, a reversible hybrid aqueous Li-CO battery is developed, integrating Li with an aqueous phase, which exhibits not only a high operating voltage and energy density but also highly selective formic acid production. Based on a Li plate as the anode, NaCl solution as the aqueous electrolyte, solid electrolyte Li Al Ge P O (LAGP) as a separator and Li transporter, and a bifunctional Pd-based electrocatalyst as the cathode, the resulting battery shows a high discharge voltage of up to 2.6 V, an outstanding energy conversion efficiency of above 80 %, and remarkable selectivity of CO -to-HCOOH conversion of up to 97 %. The related reaction mechanism is proposed as CO +2 Li+2 H ⇌HCOOH+2 Li .