Soft/hard carbon nanofibers with a unique heterogeneous interface for sodium storage

Sodium-ion batteries (SIBs) have become a promising candidate in the field of large-scale energy storage due to the abundance of sodium resources and the low cost of sodium. Developing advanced anode materials is crucial for the further development of SIBs. In this work, a unique design strategy based on the co-optimization of a soft and hard carbon heterogeneous interface is proposed to solve the problems of slow sodium storage kinetics and the poor structural stability of carbon anodes. The as-prepared soft/hard carbon nanofibers (SHC) exhibit a gradient interlayer spacing conducive to sodium storage and superior electrical conductivity. Stable sodium storage channels are formed through interface engineering to endow the SHC with excellent sodium storage capacity. Ultimately, the SHC maintains a capacity of 210 mAh g^-1 (capacity retention rate 91%) after 1000 cycles at 2 A g^-1. This study provides a new idea for the design of high-rate and long-cycling anode materials for SIBs.