Synergistically Boosting Sodium-Storage Performance of Na₃V₂(PO₄)₃ by Regulating Na Sites and Constructing 3D Interconnected Carbon Nanosheet Frameworks

Na3V2(PO4)3 (NVP) has been considered as one of the most promising candidates as cathode materials for sodium-ion batteries (SIB), owing to its high structural stability and a three-dimensional (3D) ion diffusion channel. However, low electronic conductivity and limited intrinsic Na+ diffusion kinetics seriously restrict its practical applications, especially at high current rates. Herein, we report a unique 3D interconnected hybrid architecture assembled from Ca-doped NVP embedded in in situ-generated N-doped carbon nanosheet networks. Such hybrids combine the advantages of Na site regulations and a 3D interconnected conductive network in which the former can remarkably enhance Na+ migration capability, owing to the reduced Na+ diffusion barrier, while the latter can efficiently inhibit self-aggregation of nanobuilding blocks and afford intimate contact and an electronic connection between active materials and 3D carbon scaffolds, thus leading to abundant active sites and higher structural stability than each component alone. Benefiting from these merits, the obtained hybrids exhibit superior rate capability (83.0 mAh g–1 up to 15C) and excellent cycling stability with capacity retentions of 93.1% after 5000 cycles at room temperature and 96.3% after 500 cycles at zero temperature. Such work provides a facile avenue for modulating and optimizing polyanion cathode materials with synergistically enhanced electron/ion transport kinetics at both the solid and electrode/electrolyte interface for energy-related applications.