Organic cathode with high-density active sites and extended π-conjugated structure for advanced high-performance...

Organic electrode materials demonstrate exceptional potential for sustainable rechargeable batteries due to their tunable structure, environmental friendliness and cost-effectiveness. However, their practical application in lithium-ion batteries (LIBs) is hindered by challenges such as limited capacity, poor intrinsic conductivity and significant dissolution issues in inorganic electrolytes. To address these challenges, a novel high-performance organic cathode material for LIBs, Polymeric ladder-type benzoquinone compound (PLBQ), was designed and synthesized in this work. The rational molecular design strategy imparts PLBQ with abundant active sites (CO and CN), enhancing its theoretical specific capacity. The electron-withdrawing nature of the redox-active sites (CO) and the extended π-conjugated structure lower the lowest unoccupied molecular orbital (LUMO) energy level and reduce the bandgap, thus increasing both the operational voltage and intrinsic conductivity of the PLBQ cathode. Additionally, the synergistic π-π interactions and hydrogen bonding impart remarkable solvent resistance to PLBQ, while simultaneously enhancing the stability of its molecular structure. As a result, the PLBQ cathode exhibited outstanding electrochemical performance, including long-term cycling stability (96 % capacity retention after 1000 cycles at 1 A g^-1), excellent rate capability (101.3 mA h g^-1 at 2 A g^-1) and high reversible specific capacity (252.5 mA h g^-1 at 0.1 A g^-1). This work offers a novel molecular design strategy for the development of high-performance organic cathode materials for future lithium-ion batteries.