Synthesis and investigation of electrochemical properties of graphene supported NCA cathodes

Humanity's need for energy has increased in parallel with the developing technology and industrial activities. Most of the energy needed is obtained by fossil fuels. The harmful gases released by the burning of fossil fuels damage the ozone layer and nature. The fact that fossil fuels will be depleted in the near future has caused humanity to seek alternative energy sources. As a result of these searches, studies have been started on lithium-ion batteries, one of the clean and sustainable energy sources. Lithium ion batteries come to the fore with their specific capacities, high voltages and high efficiency. Lithium-ion batteries have become one of the promising options with their use in technological devices such as mobile phones, cameras and computers, as well as in electric vehicles. The choice of cathode materials in lithium-ion batteries draws attention as a limiting factor in energy storage systems. Li-NCA cathode material, which is the subject of the thesis, has been the focus of attention of many distinguished brands, especially Tesla. NCA (LiNi0,8Co0,15Al0,05O2) is a cathode electrode composed of LiNiO2 combined with aluminum and cobalt for lithium ion batteries. Advantages include high practical capacity (200 mA h / g), wide operating voltage range (3.0V - 4,3 V), relatively low capacity loss per cycle, and low cost (lower than LiCoO2). In this thesis, NCA nanoparticles were synthesized by sol-gel method. CNTs and graphene nanosheets produced by the modified Hummers method were used as reinforcing elements to provide structural stability and increase conductivity. NCA nanoparticles are decorated between graphene nano-sheets and GN / MWCNTs by ultrasonication and vacuum filtration method to restrict the stacking of layers. The nanocomposite electrodes of NCA-GN and NCA-GN / MWCNTs were produced as independent cathodes for the CR2032 li-ion cell. High purity NCA nanoparticles were synthesized by sol-gel process. The average size of NCA nanoparticles is about 150 nm. MWCNTs and graphene have improved the performance of NCA cathode materials due to their unique structure.