Dielectric capacitors are attracting increasing attention in electronic and electrical systems where high pulse power is needed. The energy density of a typical dielectric capacitor (Ue) depends on the permittivity (εr) of its dielectric component as well as its ability to withstand an applied electric field (denoted by its breakdown strength, Eb). However, dielectric capacitors tend to have considerably lower energy densities than other storage systems such as batteries. Meanwhile, the energy efficiency (η) of dielectric capacitors — another important performance metric, defined as the ratio of Ue to the total stored energy density — is also far from satisfactory due to the commonly occurring dielectric loss in these devices. Now, Florian Le Goupil et al. at Université de Bordeaux, France, have developed a class of poly(hydroxy urethane)s (PHUs) for dielectric capacitors with both promising Ue and η.
PHUs belong to the recently emerged class of dipolar glass polymers that feature high densities of polar groups (hydroxyl and carbamate in PHUs). These polar groups possess large dipole moments that can induce high orientational polarisation in PHUs and consequently high εr of up to 8.4. Furthermore, PHUs display a relatively high glass transition temperature (50 °C), which helps to suppress the electronic and ionic conduction, thereby reducing the dielectric loss. These properties, combined with a relatively high Eb for PHUs, lead to a Ue of 6 J cm−3 (which is higher than that of commercial dielectric polymers) and a high η of 91%. Additionally, PHUs are synthesized with biomaterials by reacting erythritol dicarbonate with diamines, offering benefits as a potentially inexpensive and green energy source compared to other types of dielectric materials such as inorganic ceramics.
This is a preview of subscription content, access via your institution