One-dimensional coaxial cable-like MWCNTs/Sn4P3@C as an anode material with long-term durability for lithium ion batteries†
High capacity Sn4P3 is considered as a promising anode candidate for lithium-ion batteries (LIBs), but the fast capacity decay caused by the enormous volume changes and tin agglomeration during cycling largely limits its practical applications. Herein, MWCNTs/Sn4P3@C with a coaxial cable-like structure is designed, where a carbon protective layer is wrapped on the surfaces of Sn4P3 nanoparticles to minimize their exposure to the electrolyte and multi-walled carbon nanotubes (MWCNTs) serve as a conductive backbone to disperse Sn4P3 nanoparticles. When applied as the lithium container, the MWCNTs/Sn4P3@C composites demonstrate excellent cycling stability (delivering a high reversible capacity of 768.8 mA h g−1 after 100 cycles at 100 mA g−1 and 569.5 mA h g−1 after 1000 cycles at 1000 mA g−1) and rate capability (a de-lithiation capacity of 520.1 mA h g−1 maintained at a high current density of 2000 mA g−1). Furthermore, full cells composed of the MWCNTs/Sn4P3@C anode and the commercially available LiNi1/3Mn1/3Co1/3O2 cathode were also assembled. The result of cycling performance showed a reversible capacity of 507 mA h g−1 after 100 cycles, which is far superior to that of bare Sn4P3 and MWCNTs/Sn4P3 anodes with the reversible capacity lower than 100 mA h g−1. These excellent electrochemical performances originate from a synergistic effect between the MWCNT conductive backbone and carbon shell protective layer. The MWCNT backbone can enhance the conductivity and serve as a framework to disperse Sn4P3 nanoparticles, thus helping to accommodate the large volume changes during cycling, while the carbon shell not only can further enhance the conductivity but also minimize the side reaction between Sn4P3 nanoparticles and electrolytes.