Longer cycle life and higher discharge voltage of a small molecular indanthrone resulting from the extended conjugated framework

Organic cathodes have attracted wide attentions owing to their worthful advantages including higher capacity, abundant reserves and designable structure. However, significant dissolution of active organic materials hinders their practical applications in lithium-ion batteries (LIBs). Extending the conjugated framework in which intermolecular interactions play a crucial role, is an efficient strategy to inhibit the dissolution. Herein, an organic molecule with extended conjugated framework, indanthrone (IDT), is reported for LIBs. The rich carboxyl groups (CO) ensure the high capacity for redox reactions, which is hence utilized as cathodic active centers. Moreover, the presence of CO and amidogen resulted in plentiful intermolecular interactions, leading to insolubility and high stability. The rich functional groups also promote the chelation of oxygen and nitrogen with Li-ion and hence benefit their storage. A specific capacity of 238 mAh g−1 has been achieved for IDT-based cathodes at 0.2C, and a capacity of over 200 mAh g−1 is retained after 1000 cycles with a decay rate of only ∼0.014% per-cycle. It is worth mentioning that there is a visible increase in voltage platform during cycling. The structure design of extending the conjugated framework endows the battery performance with longer cycle life and higher energy density.