Improvement of lithium anode deterioration for ameliorating cyclabilities of non-aqueous Li–CO2 batteries†
Herein, ruthenium (Ru) nanoparticles were anchored on carbon nanotubes (Ru/CNTs) functionalized as catalyst cathodes for non-aqueous Li–CO2 cells. For cycling tests through a low cut-off capacity (100 mA h g−1), the origin of battery deterioration resulted from the accumulation of Li2CO3 discharging products on catalytic surfaces, identical to the observations in previous studies. However, the Li–CO2 cells in this work showed a sudden death within several cycles of high cut-off capacity (500 mA h g−1), and no Li2CO3 residues were investigated on the cathode. In contrast, Li dendrites and passivation materials (LiOH and Li2CO3) were generated on Li anodes upon cycling at a limited capacity of 500 mA h g−1, which dominantly contributed to the battery degradation. A Li foil-replacement method was adopted to make the Ru/CNT cathode perform continuous 100 cycles under a cut-off capacity of 500 mA h g−1. These results indicate that not only Li2CO3 residues blocked on the active sites of the cathode but also Li dendrites and passivation materials produced on the anode caused Li–CO2 battery deterioration. Moreover, in the present work, a carbon thin film was deposited on Li metal (C/Li) by a sputtering system for suppressing the dendrite formation upon cycling and promoting the defense of the H2O attack from the electrolyte disintegration. The Li–CO2 cell with a Ru/CNT catalyst and a C/Li anode revealed an improved electrochemical stability of 115 cycles at a limited capacity of 500 mA h g−1. This proto strategy provided a significant research direction focusing on Li anodes for elevating the Li–CO2 battery durability.