Titanium Dioxide Nanoparticles Encapsulated In Porous Carbon Nanofibers As Anode For Lithium-Ion Batteries

Due to its structural stability during lithium insertion/extraction and high working voltage,titanium dioxide ?TiO₂? has attracted special interest as an anode material for lithium ion batteries. However, the practical applications of TiO₂have been currently limited by its poor electric conductivity and lower actual specific capacity (168 mA·h·g^-1). In order to improve the high-rate lithium-storage capacity of TiO₂anode materials, nanostructured TiO₂hasbeen explored to offer extra reaction active sites for lithium-storage andshort diffusion distances for both electron and Li-ion transport. Additionally, various approaches have alsobeen devoted toincrease the electronic conductivity of the TiO₂, such as nanoscale carbon coating.In this study, a series of TiO₂-encapsulated porous carbon nanofibers?denoted as TOPCNFs? with different porous structure are synthesized by electrospinning of tetraethyl orthosilicate ?TEOS?/tetrabutyl titanate ?TBT?-containing PVP/ethanol solution, followed by carbonization and post-etching process. Here, TEOS is employed as the SiOx template to bring in porosity in carbon nanofiber. The effect of porous structure on the electrochemical performance of TOPCNFs nanocomposites has been investigated. The results show that the sample with largest mesopore composition exhibits the best electrochemical performance, which presents a high capacity of 239.4 mA·h·g^-1 at the rate of 0.2C (1C=168 mA·g^-1) after 100 cycles. The outstanding electrochemical performance is mainly contributed to the abundant mesopore that facilitates the penetration of Li+-electrolyte into the TOPCNFs to directly contact the embedded TiO₂ nanoparticles, thus remarkably reducing the Li+-diffusion distance.To further improve the conductivity of TOPCNFs, we introduce single-wall CNT ?denoted as SWCNT? into the porous composite nanofibers. Because the SWCNT can effectively increase the conductivity of the porous composite nanofibers, the SWCNT-added TOPCNFs electrode shows improved rate performance as compared with pristineTOPCNFs electrode. Notably, among all the as-prepared samples, the optimal electrode shows an excellent reversible capacity of 160mA·h·g^-1 at the high rate of 10 C after 2000 cycles.