Unraveling the Mechanism of Field-Induced Li Concentration for Improved Kinetics in Rechargeable Li-CO Batteries.

The design of highly efficient electrocatalysts is a promising strategy to improve the electrochemical kinetics of Li-CO batteries. However, electrocatalysts usually aim to reduce the energetic barrier for the corresponding electrochemical reactions; little attention has been given to modulating the kinetics that directly determine the local concentration of reaction molecules surrounding catalysts. Herein, we present a systematic study on the role of Li reunion on the improvement of reaction kinetics in Li-CO batteries with a Cu cone cathode. Specifically, this local, geometry-driven tip effect can enrich the local electron concentration to facilitate Li ions diffusion from the bulk electrolyte to the surface of catalyst, leading to boosted catalytic performance. Further studies demonstrate that Cu(II/I) as a solid redox mediator dominates the reversible bulk redox reactions in a Cu cone cathode, which acts as an electron-hole transfer agent and permits the efficient reduction and oxidation of solid LiCO, contributing to an accessible theoretical discharge voltage, low charge potential below 3.2 V, impressive rate capability, and a long cycling stability (333 days) for Li-CO batteries. The exploitation of the sharp-tip enhancement effect and dynamic creation of catalytic active sites is expected to become routine practice in future mechanistic studies for metal-air batteries.