Carbon nanotubes cross-linked Na₃(VO)₂(PO₄)₂F cathode for high-performance sodium-ion batteries

Na₃(VO)₂(PO₄)₂F (NVOPF) as a promising cathode material for sodium-ion batteries (SIBs) possesses high ionic conductivity and robust poly-anionic structure, but its electrochemical performance is still limited by the low intrinsic electronic conductivity. Herein, we report the fabrication of micro-cuboid-shaped NVOPF crystals cross-linked by multi-wall carbon nanotubes (CNTs) (denoted as NVOPF@CNT). The CNTs act as “hinge” between NVOPF crystals, constructing faster and efficient electron transport tunnels, thus greatly enhancing the electronic conductivity of NVOPF@CNT and increasing the operation potential. The reaction kinetics and Na⁺ storage mechanism of NVOPF@CNT are unveiled through comprehensive characterizations, demonstrating that the as-fabricated NVOPF@CNT cathode shows excellent cycle and rate performances (104.25 mAh·g⁻¹ after 1600 cycles at 1C and 91.29 mAh·g⁻¹ after 6500 cycles at 10C), benefiting from the remarkable structural stability. Moreover, the full cells, utilizing hard carbon (HC) as the anode and NVOPF@CNT-25 as the cathode, provide a high capacity of 97.4 mAh·g⁻¹ even at 10C and an energy density of as high as 262.75 Wh·kg⁻¹ after 700 cycles at 5C with the retention of 80.9%, displaying great potential for practical application.