Improved gravimetric energy density and cycle life in organic lithium-ion batteries with naphthazarin-based electrode materials

Replacing the scarce metal-based positive electrode materials currently used in rechargeable lithium ion batteries with organic compounds helps address environmental issues and might enhance gravimetric electrochemical capacity. The challenge has been to find organic materials with both high capacity and long-cycle life. Here, we study the naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) skeleton as a high capacity candidate electrode for lithium-ion batteries, showing a multielectron-transfer type redox reaction. We also use electron energy-loss spectroscopy to reveal the reaction stoichiometry during charge/discharge processes. While the lithium salt of naphthazarin itself helped deliver a high initial capacity, its cycle-life was not satisfactory. Instead, a newly synthesized naphthazarin-dimer shows a lengthened cycle-life without sacrificing the initial high capacity of 416 mAh g−1 and energy density of 1.1 Wh g−1. Replacing metal electrodes in lithium-ion batteries with organic materials reduces environmental impact and might lead to high gravimetric capacity. Here, organic electrodes containing a naphthazarin-dimer skeleton achieve an initial capacity of 416 mAh g−1 and energy density of 1.1 Wh g−1 in a lithium-ion battery.