Tailoring the Boron Configurations in B‐doped Na3V2(PO4)3@Carbon for Fast and Durable Sodium Storage

Na3 V2 (PO4 )3 (NVP) is a widely studied cathode material for sodium-ion batteries because of its high ionic conductivity and attractive charge/discharge plateau (3.4 V vs. Na/Na+ ). However, its poor electronic conductivity and severe volume expansion during sodium storage need to be addressed before its intensive application could be realized. Herein, boron-doped NVP was synthesized through a facile electrospinning method. By adding boric acid into the reaction mixture during electrospinning followed by carbonization, boron could be directly inserted into the carbon matrix, giving rise to B-doped carbon nanofiber wrapped NVP. By tuning the doping amount, the boron-containing configurations could be facilely manipulated, playing different roles in promoting the sodium storage properties of the composite. Based on the calculation results, BC2 O enhanced sodium diffusion by lowering the energy barrier, while BCO2 improved the structural stability. Due to these specific functionalities of the configurations, the as-prepared composite with a balanced amount of BC2 O and BCO2 demonstrated superior sodium storage capacity of 113 mAh g-1 at 1 C, outstanding long cycling performance of 103 mAh g-1 at 10 C, and retained 91 mAh g-1 after 1500 cycles. This gave rise to a capacity loss of only 0.08‰ per cycle, much better than the undoped counterpart.