Nitrogen, sulfur Co-doped porous graphene boosting Li4Ti5O12 anode performance for high-rate and long-life lithium ion batteries

Abstract

Enhancing the electron/ion transfer ability of Li4Ti5O12 materials is very important to achieve advanced high-rate and long-life anode in lithium ion batteries (LIBs). Here, for the first time, we report Li4Ti5O12/nitrogen, sulfur co-doped porous graphene composites (LTO/N, S-PG) via one-step facile calcination and activation process by using LiOH as Li source and activating agent. Mechanisms underlying the beneficial effects of N, S co-doped graphene for LTO anode were substantiated by the Density Functional Theory (DFT) calculations, revealing that co-doped N and S atoms not only significantly facilitate Li+ adsorption, but also ameliorate Li+ diffusion in graphene. Furthermore, the synergistic effects of nanosized LTO and porous graphene endow the composites with efficient Li+ diffusion channels and electron-conductive networks. Therefore, the LTO/N, S-PG can deliver extraordinarily high rate capability (e.g. 130 ​mA ​h ​g−1 at 80 ​C and 123 ​mA ​h ​g−1 at 100 ​C), and excellent cycling stability (83.1% capacity retention after 4000 cycles at 20 ​C). In addition, their superior electrochemical performance was also demonstrated in the full cells with LiNi0.5Mn1.5O4 cathode, which displayed 89.5% capacity retention after 500 cycles at 5 ​C. These results suggest the great promise of using the LTO/N, S-PG as a novel anode material for high-rate and long-life LIBs.