Nickel-templated carbon foam anodes for sodium-ion batteries

Sodium-ion batteries, which are abundant in resources and cost-effective, are widely considered to be suitable for large-scale energy storage. However, unstable intercalation compounds and large sodium ion radius cause carbonaceous anodes to perform poorly. Herein, a soft-and-hard composite hollow carbon foam (HCF) was one-step prepared by nickel-templated blowing strategy. The sodium-ion storage performances were enhanced by soft carbon skeleton with high conductivity, hard carbon with abundant pores, and nitrogen doping. When applied as anodes for sodium-ion storage, HCF demonstrates remarkable capacity, rate, and cycling performances. It delivers 256 mAh g−1 at 0.05 A g−1 and can be cycled for 2000 times at 1 A g−1 with remaining a capacity of 139 mAh g−1. Kinetic studies reveal that soft-and-hard carbon structure, nitrogen doping, and porous structure can effectively promote sodium-ion absorption, as well as the transport of electrons and ions. Therefore, sodium-ion batteries based on the carbon could facilitate the development of renewable energy sources.