Three-dimensional porous bowl-shaped carbon cages interspersed with carbon coated Ni-Sn alloy nanoparticles as anode materials for high-performance lithium-ion batteries

The structural damage induced by huge volume change during lithiation/delithiation results in poor cycle stability of tin-based anode materials, which becomes the major obstacle to their practical application. In this work, we fabricated three-dimensional (3D) porous bowl-shaped carbon cages interspersed with carbon coated Ni-Sn alloy nanoparticles (Ni3Sn2 and Ni3Sn4; 10-30 nm) by a freeze-drying method with self-assembled NaCl as a template followed by annealing. Both Ni3Sn2/C and Ni3Sn4/C exhibit excellent electrochemical performance as anode materials for lithium-ion batteries. In particular, the Ni3Sn4/C nanocomposites exhibit superior rate capability (735, 661, 622, 577, 496, and 377 mA h g(-1) at 0.1, 0.2, 0.5, 1, 2, and 5 A g(-1), respectively) and excellent cycling stability (568 mA h g(-1) at 0.5 A g(-1) for the second cycle and gradually increased to 732 mA h g(-1) after 200 cycles). The superior electrochemical performance is attributed to the synergetic effect of Ni-Sn alloy nanoparticles and 3D porous bowl-shaped carbon networks. The uniformly embedded Ni-Sn alloy nanoparticles can effectively alleviate the absolute stress/strain and shorten the Li+ diffusion path, and Ni in the Ni-Sn alloy acts as a buffer to suppress the volume expansion. Moreover, the 3D bowl-shaped carbon networks with high conductivity can provide abundant space for volume expansion, suppress the agglomeration of Ni-Sn nanoparticles, ensure the structural integrity, and facilitate lithium-ion diffusion as well as electron transportation.