Polyoxometalates enable cross-scale interfacial engineering of polyimide cathodes toward enhanced energy density and fast kinetics in sodium-ion batteries

Organic cathode materials suffer from low electrical conductivity, sluggish ion transport, and poor accessibility of active sites, which severely restrict their practical application in sodium-ion batteries (SIBs). Herein, we realize the simultaneous regulation of spatial and electronic structures of polyimide (PI) via polyoxometalate molecular engineering. The covalently anchored PMA (phosphomolybdic acid) clusters expose abundant C O groups with enhanced redox kinetics and create continuous charge transfer channels across the PI-PMA heteromolecular interface, thereby facilitating electron transport and improving electrode conductivity. Moreover, the strong electron-withdrawing nature of PMA significantly lowers the LUMO level of PI, which not only strengthens the binding affinity between carbonyl groups and Na + to enhance reversible capacity, but also elevates the discharge voltage plateau to substantially boost the energy density of the composite. Consequently, the PI-PMA electrode exhibits high reversible capacity, superior rate capability, and excellent long-term cycling stability. This work establishes a multi-scale molecular engineering paradigm for overcoming the intrinsic limitations of organic cathodes for high-energy-density SIBs. Download: Download high-res image (152KB) Download: Download full-size image