An 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 interfacial electrode microstructure, which directly affects electrochemical kinetics, electrode structural stability, and volume variation, results 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 (5C) capability over 5000 cycles. This is achieved via electrophoretic deposition (EPD) controlled at the nanoscale with graphene oxide acting as a binder and conductive component upon reduction annealing. The designed electrode exhibits a dramatic reduction in charge transfer impedance from 183 ohms to 75 ohms and boosting of the Li ion diffusion coefficient by one order of magnitude from 10⁻¹² to 10⁻¹¹ cm² s⁻¹. Consequently, the EPD nanoengineered TNO/rGO hybrid anode demonstrates outstanding performance, namely capacities of 252, 246, 236, and 210 mAh g⁻¹ at 0.5C, 1C, 2C, and 5C, respectively. More remarkably, it is shown to have exceptional cycling stability with 70% retention after 5000 cycles at 5C. This remarkable electrochemical performance can be attributed to the EPD-enabled nanoscale interfacial contact (between C-coated Fe-TNO and rGO) and the homogeneous microstructure endowing the electrode with a highly conductive and stable charge percolation network.