Achieving Low Charge Overpotential in a Li-CO2 Battery with Bimetallic RuCo Nanoalloy Decorated Carbon Nanofiber Cathodes

The rechargeable aprotic Li-CO2 batteries are novel and innovative technology for promising energy storage devices owing to the superb energy density and capability of directly utilizing the greenhouse gases CO2. However, they are still suffering from a severe challenge in decomposing the Li2CO3 discharge products, leading to poor batteries performance. Here we for the first time design and completely synthesize alloyed RuCo nanoparticles evenly dispersed on carbon nanofibers (RuCo/CNFs) as highly active electrocatalysts for Li-CO2 batteries. In particular, Li-CO2 battery with the optimal bimetallic Ru82Co18/CNFs cathode electrocatalyst demonstrates a remarkably reduced charge voltage of 3.75 V and maintains a stable cycling performance of over 90 cycles. An unexpected discharge capacity as high as 17 270 mAh g(-1) with a superb Coulombic efficiency of 98.9% is also obtained at 300 mA g(-1). Moreover, such a Li-CO2 battery shows outstanding rate capability even at a large current density of 2000 mA g(-1). The present study highlights the critical role of bimetallic RuCo nanoalloy in enhancing the Li-CO2 battery performance, in which the advantageous alloying effect between Ru and Co at the atomic level dramatically facilitates the decomposition kinetics of Li2CO3, giving rise to a new avenue to design advanced electrocatalysts for practically available Li-CO2 batteries.