Efficient Rechargeable Li-CO₂ Battery with a Liquid Electrolyte-Soluble CuCl₂ Electrocatalyst

We demonstrate here a simple liquid electrolyte soluble Cu-compound, viz., cupric chloride (CuCl₂) as an alternative electrocatalyst for nonaqueous Li-CO₂ batteries. The key point behind the selection of CuCl₂ is that the theoretical potential of Li-CO₂ batteries (≈2.8 V; Li⁺|Li) lies within the Cu¹⁺|Cu⁰ redox couple (2.3-3.3 V; Li⁺|Li). The presence of CuCl₂ in the liquid electrolyte near to the carbon nanotubes (≡ coelectrocatalyst)-loaded porous-CO₂ cathode led to efficient electrocatalysis of CO₂ and superior Li-CO₂ battery performance. The cell overpotential in the presence of CuCl₂ is 0.65 V, which is less than half compared to the one without it (≈1.7 V). Extensive investigations precisely elucidate the electrocatalytic mediation of CuCl₂ with the redox characteristics of CO₂. Additionally, only in the presence of CuCl₂, the existence of Li-oxalate (Li₂C₂O₄) is detected, which is a seldomly reported intermediate preceding the formation of Li₂CO₃.