Excellent Capacitive Energy Storage Performance in Organic Relaxor Ferroelectric PVDC Films

Compared with traditional ferroelectrics, relaxor ferroelectrics (RFEs) exhibit slim hysteresis loops and big dielectric constants, which are favorable for capacitive energy storage applications. Herein, organic RFE poly(vinylidene chloride) (PVDC) films with concurrently ultrahigh recoverable energy-storage density ( U rec ), low energy loss, as well as excellent cyclic charging–discharging stability are achieved by thermal annealing approach. The annealed PVDC displays an extremely high U rec of ≈11.6 J cm −3 , while maintaining a charge–discharge efficiency ( η ) of above 90%, which is better than the performance of currently state-of-the-art commercial capacitors based on dielectric polymers, such as biaxially-oriented polypropylene (BOPP) and polyethylene terephthalate (PET) films. Moreover, stable performance with U rec of ≈1 J cm −3 under 200 MV m −1 with η of ≈95% can be maintained over a charge–discharge cycling up to 100 000 cycles. The excellent performance of RFE PVDC films can be attributed to the formation of larger size grains after thermal annealing, which act as physical crosslinking points to effectively enhance mechanical strength and suppress carrier transport within the polymer films. This work offers an effective and easy-processing method for preparing RFE PVDC films with great potential for practical applications in modern power systems and electric devices.