Conjugated ladder-type polymers with multielectron reactions as high-capacity organic anode materials for lithium-ion batteries

Ladder-type conjugated polymers (LCPs) have attracted extensive attention in rechargeable lithium-ion batteries (LIBs) due to their inherent stability, poor solubility, tunable structure, and strong π—π intermolecular interactions. Herein, we describe the synthesis of two heteroatom nitrogen/oxygen-rich LCPs (TABQ-NTCDA, named TNL, and TABQ-PMDA, named TPL) by the polycondensation reaction of tetromino-benzoquinone (TABQ) and aromatic dianhydride. Benefiting from the rigid backbone, the large conjugated skeleton and the heteroatom-driven superlithiation process in polycyclic aromatic systems, heteroatom nitrogen/oxygen-rich LCPs acting as organic anode materials for LIBs display high specific capacity and long-term cycle stability. In particular, TNL displays a high reversible capacity of 1063.5 mA h g−1 at 0.05 A g−1, good cyclic performance with a capacity retention of 75.2% after 1000 cycles at 1 A g−1, and excellent rate capability of 260.6 mA h g−1 even at 2 A g−1. In addition, the superlithiation storage mechanism was further confirmed by theoretical calculations, suggesting multiple active sites of C=O, C=N, and aromatic rings for lithium-ion storage. Furthermore, a full cell is also assembled by pairing a TNL anode with a LiCoO2 cathode, indicating the feasibility of practical application.