Boosting a practical Li-CO2 battery through dimerization reaction based on solid redox mediator

Abstract

Li-CO2 batteries offer a promising avenue for converting greenhouse gases into electricity. However, the inherent challenge of direct electrocatalytic reduction of inert CO2 often results in the formation of Li2CO3, causing a dip in output voltage and energy efficiency. Our innovative approach involves solid redox mediators, affixed to the cathode via a Cu(II) coordination compound of benzene-1,3,5-tricarboxylic acid. This technique effectively circumvents the shuttle effect and sluggish kinetics associated with soluble redox mediators. Results show that the electrochemically reduced Cu(I) solid redox mediator efficiently captures CO2, facilitating Li2C2O4 formation through a dimerization reaction involving a dimeric oxalate intermediate. The Li-CO2 battery employing the Cu(II) solid redox mediator boasts a higher discharge voltage of 2.8 V, a lower charge potential of 3.7 V, and superior cycling performance over 400 cycles. Simultaneously, the successful development of a Li-CO2 pouch battery propels metal-CO2 batteries closer to practical application.