Three-Electron Redox Enabled Dithiocarboxylate Electrode for Superior Lithium Storage Performance.

Organic carboxyl compounds are promising anode candidates for lithium ion batteries in which oxygen-related redox dominates the reaction mechanisms. Herein, two nanostructured organic electrodes of π-extended naphthyl-based dicarboxylate and dithiocarboxylate compounds, namely sodium naphthalene-2,6-dicarboxylate (SND) and sodium naphthalene-2,6-bis(carbothioate) (SNB) are first synthesized and investigated systematically for lithium ion battery. Through introducing less electronegative sulfur atoms into carboxylic groups at molecular level, SNB exhibits a different voltage profile and delivers higher reversible capacity of 280 mAh g-1 than SND (198 mAh g-1) at a current density of 50 mA g-1. A combination of electrochemical properties and DFT calculations reveals that SNB could reversibly store three Li+ per formula unit, while SND only stores two Li+. The present work offers a new strategy to develop redox molecules with tunable redox potentials and accommodation more alkaline ions for high performance battery systems.