An insight into lithium-ion transport in germanium-doped lithium titanate anode through NMR spectroscopy and post-carbonization for anode applications in lithium-ion battery

Abstract

Adapting toward lithium titanate as a negative electrode for lithium-ion batteries led to the safest and long-lasting battery technology, especially for electric vehicle applications. However, the poor conductivity and lithium-ion diffusion of lithium titanate have to be addressed for widespread usage in next-generation E-mobility. The lithium-ion motion inside lithium titanate and germanium-doped lithium titanate was investigated through pulsed-field gradient nuclear magnetic resonance spectroscopy and temperature-dependent ionic conductivity studies. The superior charge carrier mobility of germanium enhanced the lithium-ion diffusion in lithium titanate significantly to 1.48 × 10−8 cm2 s−1 in Li4Ge0.1Ti4.9O12 at 500 °C. While germanium improves the ionic diffusion, an ex situ carbon coating was adapted over the sample for electronic conductivity enhancement. Samples with two different carbon contents (5 and 10 wt. %) were examined for electrochemical analysis. Significant improvements in battery performance were observed on carbon-coated germanium-doped lithium titanate. The carbon-coated sample gave superior initial performance (191 and 178 mAh g−1 for 10 and 5 wt. % carbon at 0.1C) than the pristine lithium titanate and preserved the exceptional capacity retention over a thousand cycles at 1C rate.