Innovative dielectric materials for energy storage
Capacitors store electrical energy through the polarisation of dielectric materials in the presence of an external electric field. Dielectric materials with high saturated polarisation, small remnant polarisation and a high electrical breakdown can store a large amount of electrical energy and are thus promising candidates for energy storage applications. In the EU-funded project HIDSOM (High density energy storage materials), scientists investigated four kinds of materials that show potential for pulsed power systems: antiferroelectrics, glass-ceramics, relaxor ferroelectric and polymer-based ferroelectrics. Different techniques such as glass addition, chemical doping, spark plasma sintering (SPS) and hot press sintering were employed to enhance performance of the various material systems. The team added soda-lime glass and zinc oxide to increase the densification and grain boundary strength of BST ceramics. The porosity of the ceramics was also significantly reduced, resulting in structures with high permittivity, high breakdown field and enhanced grain boundaries. Antiferroelectric ceramics with a high switching field allow for increased energy storage in pulsed power applications. Several lanthanum-doped compositions of a ceramic perovskite material (PZST) were studied. Using SPS for the shaping process, the team obtained pore-free and uniform ceramic structures with fine grain sizes. The project study also revealed the potential of AgNbO3 to be a promising lead-free ceramic compound for energy storage applications. Scientists reported double hysteresis loop in one of the material phases, which is a typical characteristic of antiferroelectric materials. The stable and relaxor-like behaviour of 0.88BT-0.12BMT ceramics over a wide range of operating temperatures suggests its potential for use in capacitors. Dielectric films tend to exhibit greater dielectric strength than thicker samples of the same material. Thin free-standing dielectric films will thus increase energy storage, making hybrid vehicles more efficient and reliable.
Keywords
Dielectric materials, energy storage, hybrid vehicles, capacitors, HIDSOM
