P-Doped Hard Carbon Microspheres for Sodium-Ion Batteries Anode with Superior Rate and Cyclic Performance

Abstract

As the first potential anode material used in sodium ion batteries (SIBs), hard carbon has received extensive sight due to its available resources, inexpensiveness, and high electrochemical properties. While the unsatisfactory sodium storage capacity and rate properties constrain its use in real-life applications. Here, phosphorus (P)-doped hard carbon microspheres (PHCS) with unique interconnected structure, expanded layer spacing (0.411 nm), and enlarged specific surface area (287.82 m2 g-1) is prepared via a facile pyrolysis strategy. It easily achieves a superior sodium storage capacity (293.5 mAh g-1 at 0.1 A g-1), remarkable rate performance (162.5 mAh g-1 at 5 A g-1), and exceptional cyclic stability (more than 2000 cycles at 5 A g-1), when applied as anode material. In addition, density functional theory (DFT) calculations reveal that P-doping not only facilitates the adsorption of Na+ on the material but also lowers its structural resistance, which greatly improves the capacity of sodium storage. This work develops a promising design strategy to prepare P-doped hard carbon for SIBs performance-enhanced anode.

Keywords: phosphorus-doping, anode materials, hard carbon microspheres, Na+ storage mechanisms