High-Concentrated Electron-Deficient Boron Through Dual-Function Boric Acid Strategy Significantly Enhancing Reaction Kinetics and Stability of Photoassisted Li-Co2 Batteries

Photoassisted rechargeable Li-CO2 batteries exhibit remarkable advantages in facilitating the formation/decomposition of insulating Li2CO3, but the conventional photoelectrodes still face issues such as ineffective hole-electron separation and low electrical conductivity. Herein, the boric acid coated boron (B@BAx) composites were developed as photoelectrodes in Li-CO2 batteries. The dissolution of boric acid overlayer has shown the dual functions including the exposure of highly-concentrated electron-deficient boron as primary photocatalyst, and the high-coordination combined with TEGDME-based electrolyte for rapid solvation and desolvation of Li-ions. This defect-enriched boron photocatalyst enables to provide suitable CB/VB values, fast carrier separation, and high conductivity for remarkably promoting reaction kinetics and stability of Li-CO2 batteries on basis of the synergetic effect with dissolved boric acid. As a result, the optimized B@BA2-based photoassisted Li-CO2 battery displayed an ultrahigh energy efficiency of 97.5 % with rare voltage gap of 0.07 V, record-lowest charge voltage of 2.80 V and long-terms cycle stability for 250 h. This unique strategy could broaden applications of high-performance electron-deficient photoelectrodes.