Boosting sodium-ion battery performance by nitrogen-doped bamboo-like branched carbon nanotube

Na-ion batteries have been considered promising substitutes for lithium-ion batteries due to the abundance of sodium resources. However, their large-scale application is limited by issues such as low capacity and poor rate capability. Here, we report a branched bamboo-like carbon nanotube (BBCNT) anode for Na+ storage. The obtained BBCNT material exhibits nitrogen-doping active sites, suitable mesopores, and bamboo-like hollow structure with numerous branches. The optimized BBCNT-2 material delivers a reversible capacity of 416 mAh g−1 at 100 mA g−1, superior rate capability of 257 mAh g−1 at 2 A g−1, and excellent reversible capacity for 4500 cycles. Owing to the fast charge diffusion, BBCNT-2 achieved an excellent capacity of 209 and 196 mAh g−1 under the current densities of 16 000 and 32 000 mA g−1, respectively. The ex-situ Raman analysis reveals that BBCNT-2 retains its structural features during a complete intercalation/deintercalation cycle of Na+. This work will shed lights on the design of high-performance carbon for low-cost and high-performance batteries.