Zn and Cl Coregulated MXene Catalyst Enhances Li-CO₂ Battery Reversibility.

Abstract

MXenes are promising cathodes for Li-CO₂ batteries owing to their high electrical conductivity and efficient CO₂ activation function. However, the effects of adsorption and electronic structures of MXene on the full life cycle of Li-CO₂ batteries have been rarely investigated. Here, we employ a coregulation approach to enhance the adsorption-decomposition of lithium carbonate (Li₂CO₃) by introducing Zn and Cl surface groups onto the Ti₃C₂ MXene (Zn-Ti₃C₂Cl₂) catalyst. The incorporation of Cl surface groups enhances Li₂CO₃ adsorption on the MXene catalyst surface, resulting in the formation of small-sized and uniform Li₂CO₃. Additionally, the introduction of Zn shifts the <i>d</i>-band centers of titanium and promotes CO₂ evolution reaction (CO₂ER) activity, thereby facilitating the decomposition of discharge products. As a result, the Li-CO₂ battery based on the Zn-Ti₃C₂Cl₂ catalyst exhibits an ultralow overpotential (0.72 V) at 200 mA g^-1 and stable cycling for up to 1500 h. This work validates the efficacy of promoting reversibility in Li-CO₂ batteries by adjusting the adsorption-decomposition process.