Scalable Synthesis and Kinetic Studies of Carbon Coated Sodium Titanate: A Promising Ultra-low Voltage Anode for Sodium Ion Battery

Abstract

The ultra-low voltage anode, Na2Ti3O7 (NTO) of high specific capacity (177 mAh/g) suffers from low intrinsic electronic conductivity, leading to poor electrochemical performance. Herein, we report the synthesis of carbon-coated Na2Ti3O7 (NTO/C) from indigenously prepared TiO2; where a low-cost organic precursor, resorcinol is used as a carbon source for the first time. Resorcinol derived carbon is beneficial in two ways: (1) increase in electronic conductivity; and (2) promote sodium ion intercalation being electrochemically active. The structural and morphological characterizations are conducted by X-ray diffraction, Fourier transform infra-red spectroscopy, scanning electron microscopy and transmission electron microscopy techniques, which confirm the formation of phase pure NTO/C with cuboid-shaped morphology. The carbon coating along with cuboid type morphology together show improved electrochemical performance due to the increase in electronic conductivity and sodium ion diffusivity. The NTO/C shows higher reversible charge capacity of 213 (± 5) mAh/g with 48% capacity retention against 178 (± 5) mAh/g with 24% capacity retention for pristine NTO after 40 cycles. Excellent rate capability is seen for NTO/C; where it shows a stable capacity of 70 (± 5) mAh/g at 2.0 C-rate. The novelty of this present work involves large scale synthesis of carbon-coated Na2Ti3O7 from indigenously prepared TiO2 and low-cost resorcinol as a source of carbon with improved electrochemical performance, which can be used as promising intercalation based anode material for sodium-ion batteries.