Development of carbon based electrode materials for lithium ion battery applications

Lithium ion batteries are drawing attention as the energy source of today's electronic devices and tomorrow's electric vehicles. Properties like quick charging, high energy storage capacity is directly linked to anode material. Low cost and easy synthesis of anode materials with superior qualities will improve the efficiency of everyday electronic devices and the electric vehicles. Currently, graphite is the most common anode material. Although graphite is advantageous with its durability and electrical conductivity, because of its limited surface area and energy storage capacity, the requested power can only be supplied with the coupling of several batteries in series. To prevent the increase in total cost and volume, materials with high surface area/volume ratio and with higher Li storage capacity should be used. To this end, graphene which is described as a single layer of graphite, with its high surface area/volume ratio, mechanical and chemical resistance and silicon, with its high Li storage capacity catch attention. On the other hand, volume change of silicon that occurs during charging and discharging, breaks the bond within the battery parts and causes to malfunction. The purpose of this study is to develop an authentic, single-step method to synthesize graphene sheets which have homogeneously distributed Si atoms. To synthesize such structures, vacuum decomposition of SiC powder is selected. However the needed high temperature for the vacuum decomposition of SiC causes particles to agglomerate. Therefore, reducing the temperature for decomposition is one of the challenges of this work. For this reason, first aim of the study is to understand the mechanism of vacuum decomposition of SiC, using single crystal wafers, and then, to apply the technology to SiC powders. The ultimate goal is to synthesize Si / graphene structures with the potential of using as anode material at lithium ion batteries. To understand the mechanism of decomposition and the effects of variables in the system, two sets of experiments are carried out, and the formed structures are characterized. Then, the knowledge gained from the SiC single crystals are applied to SiC powders and the results are discussed.