Sb3+-Doped and Carbon Nanotube-Wrapped Li4Ti5O12 with Large Capacity at High Rate

Abstract

The low theoretical capacity and conductivity of Li₄Ti₅O₁₂ (LTO) impose limitations on its capacity release at high rate, so a core–shell structure, LSbC-10 [87 wt.% Li₄Ti₅O₁₂ + 10 wt.% Sb₂O₃ + 3 wt.% carbon nanotubes (CNTs)] with Sb³⁺-doped and CNT-wrapping has been synthesized by liquid-phase dispersion and hydrothermal crystallization to address this problem. The obtained results demonstrated the successful preparation of LSbC-10 with exceptional properties. The LSbC-10 exhibits enhanced crystallinity and an increased Ti³⁺/Ti⁴⁺ ratio, which promotes the material’s conductivity, while the polarization resistance decreased significantly. Building upon the LTO, the rate capability (5C/1C) has been boosted to 83.41%, while the reversible capacity retention rate (0.1C(re)/0.1C) has increased to 93.27%. The Li⁺ diffusion coefficient also doubled to achieve a value of 1.5316 × 10⁻⁹ cm² s⁻¹. After undergoing fast charge–discharge at a rate of 5C for 1000 cycles, the capacity reached 228.53 mAh g⁻¹, representing a remarkable increase of 43.05% compared to the LTO (159.75 mAh g⁻¹). Compared with the recently reported Li₄Ti₅O₁₂ composites, the rate capability still had obvious advantages. In the meantime, straightforward and green processes can reduce the pressure on the environment during industrial production. The outstanding performance exhibited by LSbC-10 not only demonstrates that Sb³⁺-doped and CNT-wrapping significantly enhances the market competitiveness of Li₄Ti₅O₁₂ but also provides a new model for the study of insertion anode electrode composite conversion/alloying anode electrode besides single doping or coating.