Synergistic Modification of Dandelion-Shaped Na3V2(PO4)3 with Triple Superimposed Conductive Networks by Dual-Carbon Sources for High Performance Sodium-Ion Batteries

Low intrinsic conductivity and poor structural stability limit the application of Na3V2(PO4)3 (NVP). Herein, a strategy for the in situ synthesis of dandelion-shaped NVP based on cross-linked chitosan quaternary ammonium hydrogel (CHACC) and carbon nanotubes (CNTs) is proposed. CHACC and CNTs provide steric hindrance and avoid agglomeration of precursor particles. Notably, CHACC could be carbonized into a thin N–Cl codoped carbon coating, attaching to short CNTs fibers by electrostatic adsorption to construct the dandelion shape. The N–Cl codoped carbon coating delivers superior electronic conductivity and generates beneficial defects. DFT calculations are explored to investigate the influence of N–Cl codoping in the mixed carbon matrix. Significantly, triple conductive networks are successfully constructed by the dual-carbon resources. CNTs attached to the carbon coating connect with each other forms first network. Large-scale CNT network is generated through physical entanglement and bonding. CHACC provides additional conductive substrate after carbonizations. The unique triple networks supply stable carbon skeleton, alleviating the impact of current shock and increasing active sites. CHACC–CNTs-NVP submitted a value of 82.5 mAh g–1 at 80 C and remained at 61.9 mAh g–1 after 6000 cycles, corresponding to a low decay rate of 0.004% per cycle. Even at 120 C, it still releases 81.5 mAh g–1.