Precisely engineered conjugated polyimide cathodes with dense redox-active carbonyl sites for superior lithium-ion battery performance

Abstract

Polyimide cathode materials have enticed tremendous attention as alternatives to transition-metal electrodes owing to their large theoretical capacity, structural diversity, low cost, and rapid reaction kinetics. Conversely, such imide electrodes still face a severe challenge to achieve their energy storage applications satisfactorily due to the insufficient utilization of their redox-active sites originating from their low electronic conductivities. Herein, four functionalized polyimide composites have been fabricated by virtue of an in situ polycondensation reaction between a newly synthesized benzophenone–benzoquinone-based diamine and commercial dianhydrides in the presence of a conductive Super C45 material for application as cathode materials in Li-ion batteries. Such innovative integration of carbonyl groups of benzophenone, benzoquinone, and diimide rings with the Super C45 material not only creates a stable porous structure with abundant accessible redox-active sites but also guarantees fast electron/ion diffusion. Consequently, our targeted PMQP-SP cathode delivers high capacities of 143 mA h g⁻¹ at 0.2C and 122 mA h g⁻¹ at 1C and attains better rate capability besides ultra-stable cycling performance with 85% capacity retention over 500 cycles at 2C. According to DFT calculations, the theoretical results are well consistent with the electrochemical performance of the synthesized composites. Generally, this work suggests an efficient strategy to design novel carbonyl-rich organic electrodes for next-generation green rechargeable batteries.