Alkynyl-Bipyridine-Based Conjugated Microporous Polymer Anode for Lithium Storage

Conjugated microporous polymer (CMP) anode materials composed of sp- and sp²-hybridized carbons are promising for lithium storage, owing to their π-electron-delocalization framework and abundant active sites. Unfortunately, such CMP-based materials have rarely been reported, largely stemming from the synthetic challenge of achieving the predesigned structural characteristics (e.g., uniform pores). Herein, we synthesize an alkynyl-bipyridine-CMP (Alk-Bpy-CMP) which features a well-defined six-membered ring structure. The smallest structural unit consisting of alkynyl linkages, bipyridine, and aromatic rings processes high-density distributed active sites and an extended π-conjugated system. At a current density of 0.1 A g^-1, the Alk-Bpy-CMP shows a specific capacity of 674 mAh g^-1 after 100 cycles. This phenomenon can be ascribed to the preferential lithium storage behavior of bipyridine and alkynyl linkages, which possess a high proportion of storage sites. By boosting conductive property via reduced graphene oxide (rGO) encapsulation, the specific capacity was further enhanced to 1020 mAh g^-1 after 200 cycles at 0.1 A g^-1, approaching the theoretical specific capacity (1145.4 mAh g^-1) and exceeding the majority of reported CMP. A stable 1000-cycle discharge and charge test indicates the robust cycling performance of the resultant Alk-Bpy-CMP@rGO.