Unraveling the superior anodic lithium storage behavior in the redox-active porphyrinic triazine frameworks

Abstract

Porphyrinic triazine frameworks (PTF) with abundant redox-active sites, permanent porosity, and stable π-conjugated skeleton have attracted great attention for lithium-ion batteries (LIBs). Herein, we synthesized three PTFs, including PTF, Co-PTF, and Cu-PTF, by the ionothermal method. Benefitting from the metal-N4 conjugated macrocycle, triazine redox-active groups, and the “doping” N-driven superlithiation process in polycyclic aromatic systems, the optimum Cu-PTF as an organic anode material for LIBs can display a high reversible capacity (1360 mAh g−1 at 50 mA g−1), long-term cycle performance (no decrease in capacity after 1200 cycles at 1 A g−1), and superior rate performance (592.7 mAh g−1 at 1 A g−1). Furthermore, theoretical calculations and spectral characterizations are used to further confirm that multiple active sites of metal-N4, triazine groups, and aromatic rings can be used for lithium-ion storage in a superlithiation storage mechanism, which would deepen our understanding on the storage mechanism of organic anode-active materials.