Conjugated Carbonyl Polymer-Based Flexible Cathode for Superior Lithium-Organic Batteries

Conjugated carbonyl compounds are deemed as high theoretical capacity and green electrode materials for lithium-ion batteries (LIBs) but are limited by their high dissolution and poor electronic conductivity. In this paper, we have successfully synthesized a series of multicarbonyl conjugated polymers using the coupling polymerization reaction and then constructed carbonyl-conjugated polymer/carbon nanotube hybrid films by a vacuum-filtration method. Importantly, the hybrid films could serve as a flexible, binder-free, and free-standing organic cathode for LIBs, which could deliver a high reversible discharge capacity of 142.3 mAh g^-1 at 50 mA g^-1, good cycling stability with a capacity retention of 74.6% at 500 mA g^-1 after 300 cycles, and excellent rate capability of 120.6 mAh g^-1 at 1000 mA g^-1. In addition, the theoretical calculation has proved that the symmetrical conjugated structure can well accommodate four Li⁺ ions during the electrochemical reaction. Interestingly, the assembled full cell and flexible battery can power the small devices, suggesting its potential to use in bendable or wearable energy-storages devices.