Hexaazatrinaphthylene-Based Porous Organic Polymers as Organic Cathode Materials for Lithium-Ion Batteries

Incorporating small organic molecules with redox-active sites into a suitable porous organic framework could enhance both ion diffusion rate and electronic conductivity while reducing its solubility in electrolytes. Principles for the construction of a redox-active porous organic framework should not sacrifice the theoretical capacity and should balance various important parameters such as specific capacity, cycling stability, rate capability, as well as scalability. Herein, we designed two new porous organic frameworks as cathode materials for lithium-ion batteries (LIBs) using hexaazatrinaphthalene (HATN) cores which show high theoretical capacities. The polymer materials were synthesized in a facile and scalable manner with different structural features ranging from a rigid conjugated framework (HATNPF1) to a flexible nonconjugated framework (HATNPF2). HATNPF polymers demonstrated a high specific capacity (309 mA h g–1), and excellent long-term cycling stability (92% capacity retention after 1200 cycles) and rate capability (65% capacity retention at 2 A g–1 as compared to capacity at 0.2 A g–1), which is an improvement over previously reported porous organic polymers and the HATN monomer. The structure–property relationships of these porous frameworks were also studied using computational modeling.