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

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.