Unexpected Electrochemical Behavior of Crown-Based Organic Compounds for Lithium-Ion Battery Cathodes

Abstract

Replacing conventional inorganic cathode materials with organic compounds is environmentally and economically advantageous. As candidates for organic cathodes in lithium-ion batteries, heteroatom-incorporated crown-based compounds have distinctive structural and electronic properties. Herein, an advanced computational approach reveals that the coincorporation of S and Li into a B-crown compound creates a promising organic cathode with a drastically improved redox potential (4.74 V versus Li/Li+) and theoretical performances (289 mAh/g and 1097 mWh/g). This impressive enhancement originates from heteroatom-induced electron localization, which creates electron-deficient areas. In contrast, Li insertion into F- and Cl-incorporated B-crown compounds with exceptionally high redox potentials (∼5.18 V versus Li/Li+) is predicted to make the compounds electrochemically unsuitable as cathode materials due to the Li-induced cathodic deactivation. Further investigation unveils that this cathodic deactivation is induced by a sudden increase in solvation energy combined with a continuous increase in electron affinity during the discharging process. All of these findings can guide the design of high-performance lithium-ion battery cathodes using nonaromatic organic compounds without well-known redox-active sites.