Isometric Thionated Naphthalene Diimides As Organic Cathodes for High Capacity Lithium Batteries

Bingjie Zhang,§ Yueyan Zhang,§ Xiaodong Yang, Guoping Li, Sikun Zhang, Yanfeng Zhang, Demei Yu, Zishun Liu, and Gang He*

Cite This: https://dx.doi.org/10.1021/acs.chemmater.0c03661

Abstract

Although naphthalene diimide (NDI) and its derivatives have been widely used for organic Li-ion batteries (OLIBs), they are limited by a low lithium uptake capacity and ambiguous lithiation mechanism. Herein, we report two isometric thionated-NDI cathodes (cis-2S and trans-2S) obtained by replacing O with S in the imide groups which improves the battery performance compared with parent NDI (P-NDI). Remarkably, the position of S atoms plays an important role as the potential plateau of cis-2S was 100 mV higher than trans-2S, 256 mV higher than P-NDI, and the capacity of cis-2S was twice than that of trans-2S, four times as P-NDI after 400 cycles. The insitu Raman, X-ray photoelectron spectroscopy (XPS), and DFT calculations revealed that the lithiation process occurs on the less electronegative S atoms. For cis-2S, the electron density on the lithiation sites is lower than trans-2S because of a stronger electron inductive effect. This in turn enhances the redox potential and cycling stability of cis-2S. This contribution provides an additional molecular engineering strategy to develop novel organic cathode materials for high performance OLIBs.