Carbon dots supported upon N-doped TiO2 nanorods applied into sodium and lithium ion batteries

Abstract

N-doped TiO₂ nanorods decorated with carbon dots with enhanced electrical-conductivity and faster charge-transfer have been fabricated utilizing a simple hydrothermal reaction process involving TiO₂ powders (P25) and NaOH in the presence of carbon dots followed by ion exchange and calcination treatments. Due to the merits of the carbon dots, doping and nanostructures, the as-designed N–TiO₂/C-dots composite utilized as anode materials for lithium-ion batteries can sustain a capacity of 185 mA h g⁻¹ with 91.6% retention even at a high rate of 10 C over 1000 cycles. It is interesting to note that the ratios of capacitive charge capacity during such high rates for the N–TiO₂/C-dots composite electrodes are higher than those at low rates, which likely explains the observed excellent rate capabilities. In contrast to lithium-ion batteries, sodium-ion batteries have gained more interest in energy storage grids because of the greater abundance and lower cost of sodium-containing precursors. The as-obtained N–TiO₂/C-dots composites reported here and utilized as anode materials for sodium-ion batteries exhibit excellent electrochemical performances, including substantial cycling stabilities (the capacity retention ratios after 300 cycles at 5 C is 93.6%) and remarkable rate capabilities (176 mA h g⁻¹ at 5 C, 131 mA h g⁻¹ at 20 C); such performances are the greatest ever reported to date over other structured TiO₂ or TiO₂ composite materials.