Hansen Solubility Parameter-Guided Solvent Selection for Solution-Phase Discharge in Li-CO2 Batteries.

Abstract

Surface discharge mechanism-induced cathode passivation is a critical challenge that blocks the full liberation of the ultrahigh theoretical energy density of Li-CO2 batteries. Herein, we propose a novel concept based on Hansen solubility parameters (HSPs) to guide the selection of solvents for inducing the dissolution of discharge products, facilitating the detachment of in situ-formed metastable Li2C2O4 from the electrode surface and enabling a continuous Li2C2O4-dominated discharge process. Combining theoretical calculations with HSP predictions, we identified Pd-OCNTs as an ideal catalyst, with tetraethylene glycol dimethyl ether as the optimal solvent for Li2C2O4 production and stabilization. This combination facilitates the rapid diffusion of Li2C2O4 generated in situ near the catalyst surface out of the inner Helmholtz layer. Consequently, the system exhibits high energy efficiency of 96.7% and remarkable stability over 3200 h. This work provides critical insights into the solution-mediated dissolution process of Li2C2O4, informing strategies for multiphase interfacial reactions in Li-CO2 batteries.