Insight into the Li-Storage Property of Surface-Modified Ti ₂Nb ₁₀O ₂₉ Anode Material for High-Rate Application

Abstract

Ti-based anode materials are considered to be an alternative to graphite anodes to accomplish high-rate application requirements. Ti ₂Nb ₁₀O ₂₉ (TNO15) has attracted much attention due to its high lithium storage capacity through the utilization of multiple redox couples and a suitable operating voltage window of 1.0 to 2.0 V vs Li/Li ⁺. However, poor intrinsic electronic conductivity has limited the futuristic applicability of this material to the battery anode. In this work, we report the modification of TNO15 by introducing oxygen vacancies and using few-layered carbon and copper coatings on the surface to improve its Li ⁺ storage property. With the support of the galvanostatic intermittent titration technique (GITT), we found that the diffusion coefficient of carbon/copper coated TNO15 is 2 orders of magnitude higher than that of the uncoated sample. Here, highly conductive copper metal on the surface of the carbon-coated oxygen-vacancy-incorporated TNO15 increases the overall electronic and ionic conductivity. The prepared TNO15-800-C-Cu-700 half-cell shows a significant rate capability of 92% when there is a 10-fold increase in the current density. In addition, the interconnected TNO15 nanoparticles create a porous microsphere structure, which enables better Li-ion transportation during charge/discharge process, and experiences an enhancement after the carbon and copper coating on the surface of the primary TNO15 nanocrystallites.