Master of Engineering - Research
Institute for Superconducting and Electronic Materials
Yu, Ruixiang, Hybrid nanostructured materials for lithium-ion and lithium-sulphur batteries, Master of Engineering - Research thesis, Institute for Superconducting and Electronic Materials, University of Wollongong, 2013. http://ro.uow.edu.au/theses/3994
Lithium-ion batteries (LIBs) for portable electronics are attracting researchers' interest as the promising power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs). To meet the requirements for widely use in EVs and HEVs, LIBs with high rate performance, high energy density and long cycle life should be developed. In the Master's period, in order to reach this target, a series of materials were synthesized and characterized for possible applications as cathode or anode materials for rechargeable lithium-ion batteries or lithium sulphur batteries. For cathode materials, flake-like structured vanadium pentoxide was studied, while, sandwich-like framework graphene-polypyrrole/sulphur free- standing paper was also studied as the cathode candidate for lithium sulphur batteries. Moreover, for anode materials, a highly porous fibre constructed by silicon-carbon core−shell structures was investigated.
Hierarchical networks with highly interconnected V2O5 nanosheets (NSs) anchored on skeletons of carbon nanotubes (CNTs) are prepared by a facile hydrothermal treatment and a following calcination for the first time. Due to its specific framework, these V2O5 @ CNTs display excellent electrochemical performance with remarkable long cyclability (137–116 mAh g–1 after 400 cycles) at various high rates (20 C to 30 C). The excellent electrochemical performance indicated that this novel structured V2O5 could be a promising candidate as cathode material for lithium-ion batteries.
Free-standing graphene-polypyrrole/sulphur (G-PPy/S) composite paper was fabricated by a simple suction filtration method and used as the cathode in rechargeable lithium sulphur batteries. Several according characterizations were conducted, and demonstrated that the sulphur nanoparticles were homogeneously mixed with the PPy fibres and stuck with two graphene layers, with the amount of S approximately 54.1 wt % in the composite paper. A reversible discharge specific capacity of 652 mAh g-1 for this paper electrode was obtained up to 50 cycles when used as a cathode in lithium sulphur batteries.
A facile approach was reported to mass produce highly porous fibres constructed from silicon-carbon core−shell structures (Si/C@C) with high uniformity. The C-Si microfibres were prepared using Si nanoparticles as the precursor via a modified electrospinning deposition method (ESD), vacuum drying, and subsequent calcination. When evaluated as an anode material for lithium-ion batteries, the C-Si microfibres exhibited improved reversibility and cycling performance compared with the commercial Si nanoparticles. A high capacity of 760 mAh g-1 could be retained after 200 cycles at a current rate of 0.3 C. The rate capability of the C-Si microfibres is also improved. The unique Si/C@C structure was believed to offer better structural stability upon prolonged cycling and to improve the conductivity of the material. This simple strategy using the modified ESD method could also be applied to prepare other porous materials for energy storage or other applications.