Breaking the Activity-Stability Trade-Off of Li-CO2 Batteries: Covalency-Driven Reconstruction on Cobalt-Based Catalysts.

Developing highly efficient catalysts is crucial for Li-CO2 batteries to achieve superior performance, offering significant benefits of CO2 utilization and energy conversion. However, accurately elucidating the structure-activity relationships of catalysts under operating conditions remains a major challenge. The limited understanding derived solely from catalysts' pristine states hinders the rational optimization of catalytic systems. Here, by monitoring the structural reconstruction and the evolving Co ligand environments in CoX (X = O, S, and Se) precatalysts during operation, we establish the structure-activity relationship and reveal the regulatory role of precatalyst covalency in governing the catalytic activity and stability of Li-CO2 batteries. We found that the reconstruction behavior of the catalysts is fundamentally determined by the catalysts' covalency, which governs the oxidation thermodynamics that ultimately drive the structural evolution. CoS, with the weakest covalency, suffers from detrimental complete reconstruction, transforming into a fully oxidized phase CoO during cycling, ultimately resulting in the rapid failure of polarization voltage exceeding 2 V after 200 h of cycling. In contrast, CoSe, with stronger covalency, undergoes confined partial reconstruction to form a CoSe/CoO heterophase interface on the local surface, which protects active sites and facilitates electron transfer. This partial reconstruction strategy successfully breaks the activity-stability trade-off. The CoSe-based battery demonstrates both high activity and stability, maintaining a polarization voltage of 0.96 V with an energy efficiency exceeding 80% after 736 h of continuous cycling. This work reveals the structure-activity correlations dominated by covalency in Li-CO2 batteries and provides insights into designing durable and high-efficiency catalysts by inducing partial reconstruction.