Abstract
Dielectric capacitors have the highest charge/discharge speed among all electrical energy devices, but lag behind in energy density. Here we report dielectric ultracapacitors based on ferroelectric films of Ba(Zr0.2,Ti0.8)O3 which display high-energy densities (up to 166 J cm–3) and efficiencies (up to 96%). Different from a typical ferroelectric whose electric polarization is easily saturated, these Ba(Zr0.2,Ti0.8)O3 films display a much delayed saturation of the electric polarization, which increases continuously from nearly zero at remnant in a multipolar state, to a large value under the maximum electric field, leading to drastically improved recyclable energy densities. This is achieved by the creation of an adaptive nano-domain structure in these perovskite films via phase engineering and strain tuning. The lead-free Ba(Zr0.2,Ti0.8)O3 films also show excellent dielectric and energy storage performance over a broad frequency and temperature range. These findings may enable broader applications of dielectric capacitors in energy storage, conditioning, and conversion.
Highlights
Dielectric capacitors have the highest charge/discharge speed among all electrical energy devices, but lag behind in energy density
Due to the high electrical energy densities originated from their large dielectric constants (Supplementary Note 1), ferroelectric dielectric films have attracted intensive research interest[1,2,8–12]
WC of ferroelectric films has been rapidly increased to a level of 20–70 J cm−32,8,14,15, an order of magnitude higher than their bulk counterparts
Summary
Dielectric capacitors have the highest charge/discharge speed among all electrical energy devices, but lag behind in energy density. Different from a typical ferroelectric whose electric polarization is saturated, these Ba(Zr0.2,Ti0.8)O3 films display a much delayed saturation of the electric polarization, which increases continuously from nearly zero at remnant in a multipolar state, to a large value under the maximum electric field, leading to drastically improved recyclable energy densities. This is achieved by the creation of an adaptive nano-domain structure in these perovskite films via phase engineering and strain tuning. The demonstrated recordhigh capacitive energy density WC (~166 J cm−3), and drastically improved charge–discharge efficiency η (up to ~96%), together with a low dielectric loss and a high dielectric stability, indicate that the utilization of an optimal polydomain structure could become a general strategy to enhance the capacitive performance of ferroelectrics
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