Boron and nitrogen co-doped CNT/Li4Ti5O12 composite for the improved high-rate electrochemical performance of lithium-ion batteries

A novel Li4Ti5O12 (LTO) composite with multiwalled carbon nanotubes (CNTs) co-doped with nitrogen (N) and boron (B) (B,N-CNT), denoted N-B-C-LTO, was successfully obtained from a mixture of N,B-CNT and LTO after calcination. For comparison, LTO, C-LTO (LTO/CNT), N-doped N,C-LTO (LTO/N,CNT) and B-doped B,C-LTO (LTO/B,CNT) were also synthesized. Among the samples, N-B-C-LTO demonstrated the best performance in electrochemical measurements. The reversible capacity of N-B-C-LTO could reach 120 mAh/g, even at a rate of 20 C. After 150 cycles at 20 C, 97.5% of the capacity was retained with negligible capacity fading. The excellent electrochemical performance was possibly due to the separate forms of N and B in the co-doped CNTs, which not only maintained the benefits of the N and B additives, i.e., good electron-donating and electron-accepting capabilities, but also led to a synergistic effect from the unique electronic structure. (C) 2018 Elsevier B.V. All rights reserved.