Drawing a Pencil‐Trace Cathode for a High‐Performance Polymer‐Based Li–CO₂ Battery with Redox Mediator

Abstract

Abstract Lithium–carbon dioxide (Li–CO 2 ) batteries have received wide attention due to their high theoretical energy density and CO 2 capture capability. However, this system still faces poor cycling performance and huge overpotential, which stems from the leakage/volatilization of liquid electrolyte and instability of the cathode. A gel polymer electrolyte (GPE)‐based Li–CO 2 battery by using a novel pencil‐trace cathode and 0.0025 mol L −1 (M) binuclear cobalt phthalocyanine (Bi‐CoPc)‐containing GPE (Bi‐CoPc‐GPE) is developed here. The cathode, which is prepared by pencil drawing on carbon paper, is stable because of its typical limited‐layered graphitic structure without any binder. In addition, Bi‐CoPc‐GPE, which consists of polymer matrix filled with liquid electrolyte, exhibits excellent ion conductivity (0.86 mS cm −1 ), effective protection for Li anode, and superior leakproof property. Moreover, Bi‐CoPc acts as a redox mediator to promote the decomposition of discharge products at low charge potential. Interestingly, different from polymer‐shaped discharge products formed in liquid electrolyte–based Li–CO 2 batteries, the morphology of products in Li–CO 2 batteries using Bi‐CoPc‐GPE is film‐like. Hence, this polymer‐based Li–CO 2 battery shows super‐high discharge capacity, low overpotential, and even steadily runs for 120 cycles. This study may pave a new way to develop high‐performance Li–CO 2 batteries.