Efficient Rechargeable Li-CO 2 Battery with a Liquid Electrolyte-Soluble CuCl 2 Electrocatalyst.

We demonstrate here a simple liquid electrolyte soluble Cu-compound, viz., cupric chloride (CuCl 2 ) as an alternative electrocatalyst for nonaqueous Li-CO 2 batteries. The key point behind the selection of CuCl 2 is that the theoretical potential of Li-CO 2 batteries (≈2.8 V; Li + |Li) lies within the Cu 1+ |Cu 0 redox couple (2.3-3.3 V; Li + |Li). The presence of CuCl 2 in the liquid electrolyte near to the carbon nanotubes (≡ coelectrocatalyst)-loaded porous-CO 2 cathode led to efficient electrocatalysis of CO 2 and superior Li-CO 2 battery performance. The cell overpotential in the presence of CuCl 2 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 CuCl 2 with the redox characteristics of CO 2 . Additionally, only in the presence of CuCl 2 , the existence of Li-oxalate (Li 2 C 2 O 4 ) is detected, which is a seldomly reported intermediate preceding the formation of Li 2 CO 3 .