Synthesis of novel nitrogen-doped lithium titanate with ultra-high rate capability using melamine as a solid nitrogen source

Abstract

Nitrogen-doped Li₄Ti₅O₁₂ (LTO) is first synthesized by thermal decomposition of LTO and melamine. As indicated by TG, XPS and TEM analysis, nitrogen is successfully doped in LTO and the generated TiN layer is deposited on the surface of the LTO particle. The LTO with certain nitrogen modification (LTON12) on the surface exhibits enhanced electronic conductivity and Li ion diffusivity. The LTON12 electrode exhibits much better rate capability and cycling performance than the pristine LTO. The LTON12 electrode delivers a capacity of 124.2 mA h g⁻¹ after 500 cycles at 5 C with a high capacity retention of 89.1% while the capacity retention of the pristine LTO is only 43.7%. In addition, the LTON12 exhibits a capacity of 74.3 mA h g⁻¹ at even 100 C with a fixed discharge rate of 1 C. The excellent electrochemical performance of N-doped LTO is attributed to the improved electronic and ion conductivities provided by the thin TiN coating layer on the particle surface.