Polymers For High Electric Energy Density Storage

Polymeric dielectrics are principal materials for high power density electric energy storage applications. They exhibit superior processability, high dielectric breakdown strength and exceptional self-healing properties. Among this group of dielectrics, polyvinylidene fluoride (PVDF) is the most promising for energy storage applications due to its ferroelectric nature. However, the ability to produce a polar phase with relaxor-like behaviour and high energy storage density in PVDF is a major challenge, thus limiting its practical applications. Currently, this has only been achieved using complex and expensive synthesis of PVDF copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations.

The technology on offer provides a proprietary method of producing ferroelectric β-PVDF with relaxor-like behaviour without the need of any hazardous gases, solvents, electrical or chemical treatments. This simple and scalable processing route generates unprecedentedly high β-phase content (approx. 98 wt. % of crystalline phases) and is generally applicable to PVDF of different molecular weights (M_w). Relaxor-like ferroelectricity is achieved in PVDF with high M_w (at least 534 kg/mol). An ultra-high energy density of 29 J/cm³ can be achieved at 800 kV/mm in PVDF (M_w: 670-700 kg/mol) produced by this method, which is one of the highest values ever reported for a polymer based dielectric capacitor.

The technology provides a unique approach to produce a dielectric material comprising of a fluoropolymer, with part of the crystalline region of the fluoropolymer in the β-phase. The process to produce this material is very iterative and can be applied up to seven cycles. A rectangular PVDF film produced by hot pressing is first folded and followed by a pressing step which is executed at a temperature around the melting temperature of PVDF (160-170˚C). Through this pressing step, the formation of β-phase is expedited and the PVDF produced exhibits relaxor-like ferroelectricity, a property highly desired for energy storage.

• High performance material produced (approx. 98% crystallinity and energy storage density of 29 J/cm³)
• Low-cost materials (using commercially available PVDF homo-polymers)
• Scalable process produced by a proprietary technique
• Eliminates the need for complex and expensive synthesis of copolymers and terpolymers