Overcoming electron/ion transport barriers in NASICON-type cathode through mixed-conducting interphase

The NASICON-structured Na₃MnTi(PO₄)₃ (NMTP) cathode has attracted widespread attention due to its prominent thermal stability, stable 3D structure and rapid sodium ion transport channel. However, the poor cycling stability, limited electronic conductivity and phase transition represent significant obstacles to for its commercialization. Herein, an innovative mixed-conducting interphase, comprising amorphous carbon and Ti₃C₂-MXene, was developed for NMTP. NMTP particles are evenly dispersed on the MXene sheets through electrostatic adsorption, and MXenes can also regulate the growth of NMTP crystals and provide a large number of active sites in contact with the electrolyte. Furthermore, DFT calculations demonstrate that MXene enhances both electron and ion transport processes. Therefore, the mixed-conducting interphase, forming an interconnected network on the NMTP surface, serves as an artificial cathode electrolyte interface, significantly enhancing the dynamic processes and cycle stability of the NMTP cathode. The NMTP/C@Ti₃C₂ exhibits a fully reversible three-electron redox reaction and inhibited voltage hysteresis. An excellent reversible capacity of 158.2 mAh/g is achieved at 0.2 C, corresponding to an extremely high energy density of 466.6 Wh/kg. This study presents an effective approach for developing high-energy SIB cathodes.