(PVDF/BaTiO/sub 3/) and (PP/BaTiO/sub 3/) films for energy storage capacitors

Energy storage is nowadays very useful for applications such as energy recuperation or energy compensation systems. For this purpose batteries are very powerful, but the charging time remains too long. On the other hand, capacitors can be charged instantaneously but the energy density is low (the capacitor to accumulator energy ratio is 1/2000). Many studies encourage the use of films filled with ceramic for energy storage applications. This paper reports on such films based on compounds which are prepared using a modular twin screw extruder. It has been shown that it is possible to make composites (PVDF/BaTiO/sub 3/) or (PP/BaTiO/sub 3/) in a twin screw extruder. For an energy storage capacitor the best results are obtained with the PVDF matrix. Considering a functional dielectric strength equal to 100 V//spl mu/m, the energy density reaches 0.13 Wh/kg for a filler volume content of 30%. It is low compared to a battery, but the capacitor to accumulator energy ratio is now 1/460. Such a product may be suitable for energy storage applications. The manufacturing process has to be improved. Good agreement is observed between theoretical and experimental percolation coefficients.