Single-Molecule Dye Organics with Multielectron Redox Processes as Cathode Materials for Lithium Secondary Batteries.

Abstract

Dissolution loss is the biggest issue for an organic electrode material, and nowadays the most popular strategy to avoid it is to synthesize a polymer or add a large amount of conductive carbon. In this study, the issue is addressed by using monomolecular organics with a relatively long chain and large size. A dye composed of quinones and a carbazole is proposed as the cathode material for a Li secondary battery. The unique structure of more than three quinones joined by a carbazole bridge improves the cycling stability significantly. In addition to the widely known enolization reaction of the quinone moiety, extra anion-doping capacity is supplied by the carbazole moiety. As a result of the multiple active sites, multielectron redox transfer and remarkable capacity enhancement are realized by using Vet Yellow 3RT dye material. It shows a stable capacity up to 340 mAh g-1 within 300 cycles. XRD, X-ray photoelectron spectroscopy, and electrochemical measurements were used to confirm the reactivity of the carbonyl group and the N-heterocycle toward Li+ and PF6 - , respectively. In this work, a new application of this dye material is revealed, providing a new avenue to address the dissolution loss and capacity breakthrough of organic batteries.