Hollow ultra-microporous carbon spheres as high-rate anode nanomaterials for sodium-ion batteries

Hollow porous carbon spheres are considered as promising anode nanomaterials for sodium-ion batteries (SIBs), but suffer from the problems of poor rate and cycling performances. Typical improvement strategies by creating micropores or mesopores are used to boost cycling and rata performances. Herein, hollow porous carbon spheres (HPCS) with ultra-micropores are prepared as anode nanomaterials for SIBs. The optimized HPCS-2 delivers a decent capacity of 272.3 mAh g−1 at 0.1 A g−1, a capacity retention rate of 96.62% over 500 cycles at 2 A g–1, and, in particular, a remarkable rate performance of 233.64 mAh g–1 at 10 A g–1. The great enhancement is elucidated predominantly by the abundant ultra-micropores that provide rapid ion-transport pathways and accelerated sodium-ion diffusion coefficient. The results promise rational design and preparation of high-rate carbon anode nanomaterials for sodium storage.