Ultra high fast charge/discharge lithium ion battery anode on nanosized TiO2 on porous graphene hierarchitecture

Abstract

As the grown concerns of environmental pollution, climate changes and exhaustion of energy, the developments including not only technologies for harvesting and converting sustainable energy sources, but also effective methods for storing and delivering the energy efficiently upon demand for applications, such as electric vehicles and smart grids have been improved. In that reason, the electrochemical devices have emerged as one of the advanced technologies for utilizing the electrical energies from renewable resources. In addition, battery systems are the indispensible technology in portable electronic devices and electrical vehicles. Titanium (IV) oxide is one of the promising material for electrochemical applications. It is earth abundant, low cost, eco-friendly, high safety and high chemical stability. $TiO_2$ has also fast lithium ion insertion characteristic without its structural changes which is important in the performance of lithium ion batteries. Although It suffers from low electro-conductivity resulting in low capacitance at high current rates, it was demonstrated this weakness could be improved through nanostructuring $TiO_2$ and additional conducting materials such as graphitic carbon. In this thesis, three-dimensional macroporous graphene foam and its hybrid composite with titanium oxide nanoparticles were synthesized, so called graphene foam (GF), to improve the electrochemical property such as high rate capability. The high rate capability without critical capacitance loss is attributed to extremely high conductive graphene foam (GF). Three-dimensional pores in macroscale could enhance the accessibility to electrolyte and accelerate the ion diffusion rate. Moreover, freestanding structure could also facilitate the procedures assembling electrochemical cells without additional binders. Due to relatively high surface area, large amount of $TiO_2$ can easily be decorated and controlled. Through this ways, our study indicate that a $TiO_2$ NP-graphene foam ($TiO_2$ NP-GF) exhibit ultrahigh fast charging-discharging rate capability as an anode materials for lithium ion battery.