Si/TiO2/Ti2O3 composite carbon nanofiber by one-step heat treatment with highly enhanced ion/electron diffusion rates for next-generation lithium-ion batteries

Abstract

Silicon anodes are one of the most promising candidate materials for next-generation lithium-ion batteries because of their high theoretical capacity and natural abundance. Unfortunately, the poor conductivity of silicon and large volume expansion (>400%) during the cycle restrict its commercialization. Herein, we combine Si with stable TiO2 and electrically conductive Ti2O3 to significantly increase the capacity and cycle stability of the Si-based anodes. The preparation of a Si/TiO2/Ti2O3-Carbon Nanofiber (denoted as STTC) composite via mechanical blending, electrospinning and subsequent carbonization of Si, TiO2, and polyacrylonitrile (PAN). This material exhibits a reversible specific capacity of 924 mAh g−1 after 500 cycles of 1 A g−1 current density. Moreover, it also exhibits excellent rate performance even at current densities of 6 A g−1. The outstanding electrochemical performance can be ascribed to Ti2O3 generates in the carbonization process has high ion diffusivity and electrical conductivity. Furthermore, the disordered frame of TiO2/Ti2O3 forms voids, which can alleviate the volume expansion of silicon, maintain the electrode integrity during charge and discharge, and form a thin and stable solid electrolyte interphase (SEI). Additionally, the conductive frame of carbon nanofibers also significantly improves the ion and electron conductivity of the complete electrode.