Superior rate-capability and long-lifespan carbon nanotube-in-nanotube@Sb2S3 anode for lithium-ion storage

It is vital to improve the rate capability and cycling performance of Sb2S3 to promote its application in lithium-ion batteries. Herein, Sb2S3 is successfully anchored inside a carbon nanotube-in-nanotube via a multi-step method based on a metal–organic framework and carbon nanotubes. The composite has a large specific surface area (48.1 m2 g−1), relatively high content of Sb2S3 (57%), and an external highly conductive nitrogen-doped amorphous carbon nanotube. Benefitting from these advanced structure advantages, such as well-confined Sb2S3, completely closed internal void space, highly conductive carbon matrix, and formation of C–S covalent bonds, the composite exhibits superior lithium storage performance. The rate capability is its highlight. Even at 15 A g−1, the discharge capacity still reaches 361 mA h g−1. After the rate test, a cycling test at 5 A g−1 up to 400 cycles demonstrates its excellent structural stability. The cycling performance is very impressive (710.5 mA h g−1 at 1 A g−1 after 1500 cycles, 316 mA h g−1 at 5 A g−1 after 1700 cycles, 201.5 mA h g−1 at 10 A g−1 after 1000 cycles). The reversible capacity is outstanding (1117.2 mA h g−1 at 0.1 A g−1). Electrochemical kinetic analyses and ex situ observation of the cycled composite are studied in detail to comprehensively elucidate its electrochemical mechanism. It can be concluded that carbon nanotube-in-nanotube@Sb2S3 is a promising anode material for high-performance lithium-ion batteries.