Improvement of polymer composite based Li-ion battery packs and investigation of their properties

Today, with the increase in the importance of electric cars, the work of the car companies on electric vehicles is increasing day by day. In this respect, studies on increasing battery capacities and lightening of vehicles have been focused on. This obstacle must be overcome in order for electric cars to replace traditional fuel-powered vehicles in the future. One of the studies conducted in this direction is to reduce the total weight of the vehicle. If the vehicle becomes lighter, the electric motor spends less energy, and energy of the battery is consumed in the long time. The aim of this study is to develop and investigate the properties of polyamide 6 (PA6) polymer composite filled with high thermal conductivity boron nitride (BN) and aluminum nitride (AlN). The polymer composite-based Li-ion battery pack is foreseen to provide a major weight advantage over conventional aluminum battery packs. In this study, PA6/AlN/BN hybrid polymer composites were produced by using different ratios of AlN and BN additives. Composites produced as extruded filaments were extruded into granules in the granular production line. In the final stage, obtained granules were shaped into plates of 4 mm and 0.5 mm thickness by compression molding method. In the thesis, the distribution of the additives in the polymer was investigated, thermal conductivity, electrical conductivity and mechanical properties were characterized and the relationships between these properties were determined. It has been observed that the mechanical properties of PA6 decreased together additives. When additives was added to the structure, a rapid decrease in tensile strength and elongation at break values was observed. As quantity of additives rate increases, the elongation at break value decreases. There is a slight increase in electrical conductivity of PA6 with additives. The highest electrical conductivity value was obtained for composite containing 50 vol% additives. With the addition of AlN/BN hybrid additives, the thermal conductivity value of PA6 is increased up to five times. The highest thermal conductivity value was obtained in the composite containing 50% AlN/BN by volume with 1,040 W/m.K. Homogeneous distribution of AlN/BN additives in PA6 matrix was obtained. No agglomeration of the additives was observed in the structure. According to FTIR analysis of PA6/AlN/BN hybrid polymer composites, PA6, AlN and BN structures are clearly observed. According to DSC analysis results, melting and glass transition temperatures of PA6/AlN/BN polymer composites are not affected by the presence of BN and AlN additives.