Unraveling the Mechanism of Field-Induced Li⁺ Concentration for Improved Kinetics in Rechargeable Li–CO₂ Batteries

Abstract

The design of highly efficient electrocatalysts is a promising strategy to improve the electrochemical kinetics of Li–CO2 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–CO2 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 Li2CO3, 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–CO2 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.

A Li–O2/CO2 battery based on bio-inspired engineering of the Bi2S3/PVP cathode

“…To improve their performance, some noble and transition metal-based materials have attracted much attention due to their excellent catalytic activity. [29][30][31][32][33] The results show that they can effectively reduce the overpotential and prevent the electrolyte decomposition by a charging voltage that is too high, thus greatly improving the catalytic efficiency. However, their cost is severely hampered by their practical applications.…”