Ultra-fast-charging and Long-cycling Titanium Niobate/Reduced Graphene Oxide Anode via Electrophoretic Interfacial Engineering

Abstract

Titanium niobate (TiNb2O7, TNO) materials are emerging as high-performing anode candidates for fast charging Li-ion batteries. However, the non-homogeneous interphasial electrode microstructure, which directly affects electrochemical kinetics, electrode structural stability, and volume variation, result in significant performance loss upon extended cycling under fast charging. To address these issues, we have nanoengineered a carbon-coated single-crystal Fe-doped TNO (C-FeTNO)/reduced graphene oxide (rGO) anode with ultra-fast (5 C) and over 5,000 cycles capability. This is achieved via electrophoretic deposition (EPD) controlled at nanoscale with graphene oxide acting as binder and conductive component upon reducing annealing. The designed electrode exhibits dramatic reduction in charge transfer impedance from 183 ohm to 75 ohm and boosting of Li ion diffusion coefficient by one order of magnitude from 10-12 to 10-11 cm2/s. Consequently, the EPD nanoengineered TNO/rGO hybrid anode demonstrates outstanding performance, namely capacities of 252, 246, 236, and 210 mAh/g at 0.5 C, 1 C, 2 C, and 5 C, respectively. But more remarkably, it is shown to have exceptional cycling stability of 70 % retention after 5000 cycles at 5 C. This remarkable electrochemical performance can be attributed to the EPD-enabled nanoscale interphasial contacting (between C-coated Fe-TNO and rGO) and the homogeneous microstructure endowing the electrode with a highly conducting stable charge percolation network.