Development of energy storage capacitors, based on PVDF/BaTiO{sub}3 films

摘要

The storage of electrical energy is a big challenge for many applications, such as compensation Systems or electric cars. Some of the equipments used are batteries, super and ultra capacitors. The supercapacitor and ultracapacitor have the highest energy density in volume (5600-7200 J/I) but their electric strength is low, around 5V/μm. The use of polymer composite films with high permittivity are also promising [1-3] but the processing of these films must be improved. The results of tests on thin films of polyvinylidene fluoride or polypropylene filled with a barium titanate, with an intrinsic permittivity of 3800 have been presented in a previous paper [4]. The filler volume fraction studied ranged between 0 and 40 %. The films were obtained bycast film extrusion through a flat die, and the thickness obtained was about 40 microns. The best energy density results were obtained with the PVDF matrix, filled with 15, 20, 25 and 30% of barium titanate.In this paper, the influence of stretching, in the rubbery state and in the molten state, on the relative permittivity and the electric field strength of the PVDF composite films have been studied. The effect of a coupling agent is also examined.