Novel organic anode based on o-benzene active material for high-performance lithium ion batteries

Organic redox-active materials are investigation hotspots for lithium ion storage due to their structural diversity and tunability. A large number of researches have focused on the organic materials of benzene para-substitution type. There are little investigations on benzene ortho-substitution type organic materials. Benzene ortho-substitution redox molecules are generally considered to be too close to the functional group to fully react, and conjugated structure is not as stable as that of para-substitution. However, we reported dilithium phthalate (Li2PA) anode active material for lithium ion battery. Interestingly, Li2PA anode has an excess capacity and reaches four-electrons reaction, and the lithium ions storage mechanism is explored: not only the two adjacent conjugated carbonyls can fully react, but also the rearranged benzene ring can accept two Li + ions. Li2PA anode has a high specific capacity of 674 mA h g−1 at 60 mA g−1, with 91.7% capacity retention after 125 cycles (cycled for 4 months). Furthermore, it achieves high-rate capability, holding the specific capacity of 110 mA h g−1 at 4000 mA g−1. This research shows that Li2PA can be used as organic active material for anode, opening up new possibility for organic anode development. •Dilithium phthalate is first used in lithium ion battery.•Dilithium phthalate anode performances exceed reported dilithium terephthalate.•Crystalline state of dilithium phthalate changes to amorphous state during cycles.