TiO2@ CARBON NANOSTRUCTURE FOR IMPROVED LITHIUM ION PROPERTIES

摘要

Lithium ion batteries (LIBs) are excellent power sources for portable and transportation applications because of their relatively high energy density, high voltage, high power density, and long-term operating life, etc. In the LIBs, the cathodes consist of transition metal oxide containing lithium sources (e.g., LiCoO2, LiMn2O4, and LiMnPO4, etc.), which show typically higher voltage and lower capacity than the anodes. On the other hand, the anodes mainly utilize carbon-based materials (e.g., carbon black, carbon nanotube, carbon nanofiber, and graphene) containing higher conductivity and highly initial capacitance, which show typically lower voltage and higher capacity than the cathodes. Besides, in the anodes, the transition metal oxides have been utilized due to low cost, good safety, environmental friendliness, and especially high lithium intercalation potential in comparison with carbon-based materials. Among transition metal oxides, TiO2 is regarded as a promising lithium ion insertion/desertion material with low production cost, high abundance, non-toxicity, very low volume change during lithium ion insertion/desertion (3-4%), good structural stability, and long cycle life. However, TiO2 has limitations such as lower initial- practical capacity than theoretical value (335 mAh g~(-1)) and low high- rate capability due to poor ionic conductivity and electrical conductivity. There have been many reports in the literature to improve the electrochemical properties by the structure-controlled or complex nanostructures.