Multiredox tripyridine-triazine molecular cathode for lithium-organic battery

Electroactive organics with multiple redox centers have advantage to realize high capacity and energy density of lithium-ion batteries (LIBs). Herein, a novel multiredox organic molecule, viz . 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT), is developed by densely assembling active sites in one molecule, which yields reversible four-electron storage and a high capacity of 347 mA h g −1 TPT at 0.10 A g −1 in carbonate electrolyte. Battery test reveals a superior cyclability with a capacity retention of 66% after 6000 cycles at 2.0 A g −1 and rate performance. Physiochemical characterizations and theoretical calculation are extensively performed to clarify the superior capacity and stability. Physicochemical characterizations reveal that the TPT evolves to diradicals upon accepting two electrons, and the quinoid structure upon accepting four electrons. The effective delocalization of the four charge over the four aromatic rings can remarkably stabilize the organic molecule against side reactions. The formation of a cathode electrolyte interface film contributes to the high cyclability during the battery test. The capacitive response of TPT is recognized as the dominant proportion in capacity, which contributes to the superior rate performance. This work offers an effective strategy on the rational design of high-capacity and stable organic cathode materials for LIBs.