Ultrahigh rate binder-free Na₃V₂(PO₄)₃/carbon cathode for sodium-ion battery

Sodium ion batteries (SIBs) are very promising for large-scale energy storage in virtue of its high energy density, abundant sodium resources and low environmental impact, etc. However, it is still a big challenge to develop high-performance and durable cathode materials for SIBs. Among different candidate materials, Na₃V₂(PO₄)₃ has attracted great attentions due to its high theoretical capacity (117 mAh/g), stable framework structure and excellent ionic conductivity. However, Na₃V₂(PO₄)₃ delivers inferior rate capability and cycling stability due to its poor electronic conductivity. In this work, free-standing Na₃V₂(PO₄)₃/carbon nanofiber membranes are synthesized by an electrospinning-sintering route. The sample could deliver excellent cycling capability with specific capacity of 112 mAh/g at 1 C after 250 cycles and ultrahigh rate capability with 76.9 mAh/g even at 100 C, which is superior to many state-of-the-art SIB cathode materials. This can be attributed to the hierarchically distributed Na₃V₂(PO₄)₃ crystals in carbon nanofiber network, which possesses outstanding electronic/ionic conductivity and thus leads to an ultrahigh rate capability.