Atomic-Level Insights into Singlet Oxygen-Induced Catalyst Degradation in Li-CO2 Batteries

Li–CO2 batteries (LCBs) offer a compelling route toward integrated energy storage and carbon conversion, yet their long-term durability remains elusive. Although high-performance catalysts substantially promote the decomposition kinetics of Li2CO3, they often exhibit accelerated deactivation, implying deeper instability beyond the accumulation of insulating products. Here, operando electron paramagnetic resonance and UV–visible spectroscopy directly identify a voltage-dependent release of singlet oxygen (1O2) during Li2CO3 decomposition. Correlated in situ Raman and differential electrochemical mass spectrometry reveal that 1O2 triggers a cascading instability in LCBs, coupling catalyst oxidation, intensified polarization, enhanced 1O2 release, and amplified parasitic reactions into a self-reinforcing degradation loop. Guided by the Density functional theory calculations, an antioxidative MXene-based catalyst featuring low subsurface anion exposure was designed. The optimized catalyst delivers an exceptional energy efficiency of 96%, a reversible areal capacity of 31.5 mAh cm-2, and only 0.01 V charging voltage polarization after 2500 h cycling. This work elucidates the atomic-scale origins of 1O2-mediated failure and outline a general design principle for oxidation-resistant catalysts in high-efficiency and long-life LCBs.