Boron-Phosphorus Codoped Coral-like Hard Carbon Anodes for Sodium Ion Storage

Hard carbon materials have the advantages of low price, environmental friendliness, and good electrical conductivity but have the disadvantages of unsatisfactory sodium storage capacity and low long-cycle stability. The use of heteroatom doping and structural design can significantly improve the sodium storage properties of carbon materials. In this paper, a boron-phosphorus doped hard carbon material (CABP) was designed by using citric acid as the carbon source. The rich pore structure of CABP also provides fast transport channels for Na⁺, while the efficient doping of B and P atoms can distort the graphitic layer and generate more active sites and defects. The CABP carbon material therefore exhibits excellent electrochemical properties. It can obtain pretty good capacities of 246.8 mA h g^-1 after 400 cycles at 0.1 A g^-1. Moreover, it was able to maintain 161.9 mA h g^-1 after 5000 cycles at 5 A g^-1. This work provides a new route for the facile preparation of high-performance heteroatom-doped carbon materials and an idea for the preparation of diatom-doped materials for energy storage.