Rational Assembly of Hollow Microporous Carbon Spheres as P Hosts for Long-Life Sodium-Ion Batteries

This paper reports the rational assembly of novel hollow porous carbon nanospheres (HPCNSs) as the hosts of phosphorous (P) active materials for high-performance sodium-ion batteries (SIBs). The vaporization-condensation process is employed to synthesize P/C composites, which is elucidated by both theories and experiments to achieve optimized designs. The combined molecular dynamics simulations and density functional theory calculations indicate that the morphologies of polymeric P-4 and the P loading in the P/C composites depend mainly on the pore size and surface condition of carbon supports. Micropores of 1-2 nm in diameter and oxygenated functional groups attached on carbon surface are essential for achieving high P loading and excellent structural stability. In light of these findings, HPCNS/amorphous red phosphorus composites with enhanced structural/functional features are synthesized, which present an extremely low volume expansion of approximate to 67.3% during cycles, much smaller than the commercial red P's theoretical value of approximate to 300%. The composite anodes deliver an exceptional sodium storage capacity and remarkable long-life cyclic stability with capacity retention over 76% after 1000 cycles. This work signifies the importance of rational design of electrode materials based on accurate theoretical predictions and sheds light on future development of cost-effective P/C composite anodes for commercially viable SIBs.