Synthesis And Research Of Lithium Titanate/Carbon Nanofibers For Lithium-Ion Battery Anode Materials

With public concerns of environmental issues and serious impact of digital age, it is a great challenge to develop new energy storage devices. To satisfy the rapid popularization of environmental electric vehicles and cater the trend of portable electronic equipment, a new generation of lithium ion batteries (LIBs) with high-rate performance and excellent reversible capacity is highly needed. However, conventional LIBs using carbonaceous anodes generally suffer from crucial safety problems due to the formation of dendritic lithium. Particularly, spinel lithium titanate (Li4Ti5O12, denoted as LTO) has been regarded as one of the most promising alternative anode materials owing to its unique characteristics, such as the near-zero volume change and the improved safety. However, the practical application of LTO is hindered by its intrinsic low specific capacity and poor electronic conductivity.In this study, a nanosized LTO/CNFs flexible anode material has been fabricated by LiOH hydrothermal treatment with electrospun anatase titanium dioxide/carbon nanofibers (A-TiO2/CNFs), followed by thermal treatment. A dual-phase LTO-TiO2/CNFs film electrode with superior electrochemical performance was also developed. The influences of different process parameters on surface morphologies, chemical compositions and electrochemical properties were discussed in detail.The results show that A-TiO2 nanoparticles take erosion reaction with LiOH and H2O molecules under high pressure and elevated temperature during hydrothermal environment. As a result, TiO2 vacate gradually from CNFs, and nucleate moderately with LiOH. Then well-crystallized LTO nanoparticles are obtained at the optimal heat-treated temperature of 600℃. Large numbers of micropores, which contribute to the enhanced electrochemical property, are formed on the CNFs during the migration-corrosion-dissolution-nucleation process. Increasing hydrothermal time and hydrothermal temperature will improve the crystallization of LTO phase. The surface morphology of LTO/CNFs is synergistically affected by both LiOH concentration and hydrothermal time. Meanwhile, the average crystal sizes of nanoparticles tend to grow larger with the increase of hydrothermal temperature, which even show particle aggregation at 190℃. After 200 cycles at a current density of 100mA·g-1, the LTO/CNFs and LTO-TiO2/CNFs anodes present high reversible capacities of 154.6 and 203.8 mAh·g-1, respectively. The LTO-TiO2/CNFs still delivers a high discharge capacity of 114.3mAh·g-1 at high rate of 2000mA·g-1 (for LTO/CNFs: 92.5mAh·g-1), mainly ascribed to the interfacial pseudocapacitive effect induced by its unique architecture.