Design of graphen reinforced CuO anode electrodes and applications of Li-ion batteries

Lithium ion batteries are one of the most prominent power supplies for portable electronic devices due to their high energy densities, long cycle life and shelf life, wide usage temperature range, fast recharging and high energy efficiency. In order to meet the increasing energy demand of today, it is inevitable to develop new electrode materials with higher capacity to further increase the energy density. To date, lithium ion batteries have used graphite as the traditional anode material, but the theoretical capacity of graphite (372 mAhg-1) is limited due to the formation of LiC6. For this reason, efforts have been made so far to develop high capacity anodes, including carbon nano materials, silicon materials and transition metal oxides (MxOy, M = Fe, Co, Ni, Sn, Cu, vb.). Among metal oxides, CuO is a promising candidate because of its abundance, low cost, chemical stability, high theoretical capacity (674 mAhg-1) and environmental friendliness. However, pure CuO electrodes suffer from poor cycle and low capacity at high C-rate during charge / discharge cycles due to low conductivity and morphological changes caused by high volume changes. A small amount of high-quality graphene and carbon nanotubes can increase the strength and cyclic stability while maintaining the high-energy storage capacity of lithium-ion batteries. Graphene shows a unique structure of carbon layers bonded to two-dimensional sp2 hybridization and shows high surface areas (2630 m2 g-1 theoretical value), mobility of charge carriers (200,000 cm2 V-1 s-1) and single atomic thickness with large electrochemical window. Carbon nanotubes, on the other hand, both increase the electrical conductivity of the anodes and ensure their stable operation for a long time. These properties make graphene and carbon nanotube an ideal two-dimensional supporting material used to fix active materials that offer high performance on lithium-ion batteries. In this thesis, CuO nanoparticles were synthesized in nanorods form. The synthesized nanorods structures were reinforced with graphene and carbon nanotube and hybrid composite free electrodes were produced. The chemical, electrochemical and physical properties of the free electrodes were investigated in detail.