Made From Henna! A Fast-Charging, High-Capacity, and Recyclable Tetrakislawsone Cathode Material for Lithium Ion Batteries

Nature-inspired solutions to energy storage are aimed at sustainability, cost-efficiency, and humanitarian issues surrounding current lithium ion battery (LIB) technologies. Tetrakislawsone (TKL), a tetramer derived from the natural tattooing dye henna, yields a promising cathode material for recyclable and environmentally friendly LIBs. Previously, small organic molecules as LIB materials have displayed precipitous capacity fading and poor cycling lifetimes due to their instability in organic electrolytes. Our study finds that tetrakislawsone exhibits stable gravimetric capacities exceeding 100 mAh g(-1) for over 300 charge/discharge cycles owed to the coordination of four Li ions as well as the unique stability of lithium salts of TKL in electrolytes. The mechanistic investigation of metal ion binding was aided by DFT computations, solid-state NMR, and in situ spectroscopy studies revealing that the molecule adopts a nonplanar coordination geometry. This allows for reversible lithium ion binding between the carbonyl and hydroxyl functional groups of TKL subunits.