lowest energy density. [4][5][6] To improve this, much attention has been particularly paid to antiferroelectric ceramics such as PZ, [ 7,8 ] PLZT, [ 9,10 ] PZN-PMN-PT, [ 4 ] PLZST, [ 4 ] etc., since they normally have higher energy density than ferroelectric and paraelectric ceramics at comparable electric fi eld. [ 2 ] The energy density in bulk ceramics is usually less than 1 J cm −3 because of the limitation of low dielectric breakdown strength (<100 kV cm −1 ). [ 11,12 ] With the development of high-quality thin fi lms by sol-gel, pulsed laser deposition (PLD), molecular beam epitaxy, etc., large energy density, mainly in lead-based antiferroelectric thin fi lms, has been achieved due to the higher dielectric breakdown strength (>500 kV cm −1 ). [ 3,9,13,14 ] For example, a high energy density of 53 J cm −3 at 3500 kV cm −1 was obtained in relaxor antiferroelectric (Pb 0.92 La 0.08 )(Zr 0.9 Ti 0.05 ) O 3 sol-gel thin fi lm. [ 9 ] However, widespread applications of lead-based materials are prohibited due to the toxicity of lead. As a lead-free dielectric material, poly(vinylidene fl uoride) (PVDF)-based polymer was also widely studied and a high energy density of 27 J cm −3 at 8000 kV cm −1 was reported. [ 1,4 ] However, its lifetime and reliability are seriously impaired at the maximum operating temperature (typically less than 85 °C), seriously limiting its applications as capacitors.Ferroelectrics/antiferroelectrics with high dielectric breakdown strength have the potential to store a great amount of electrical energy, attractive for many modern applications in electronic devices and systems. Here, it is demonstrated that a giant electric energy density (154 J cm −3 , three times the highest value of lead-based systems and fi ve times the value of the best dielectric/ ferroelectric polymer), together with the excellent fatigue-free property, good thermal stability, and high effi ciency, is realized in pulsed laser deposited (Bi 1/2 Na 1/2 ) 0.9118 La 0.02 Ba 0.0582 (Ti 0.97 Zr 0.03 )O 3 (BNLBTZ) epitaxial lead-free relaxor thin fi lms with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases. This is endowed by high epitaxial quality, great relaxor dispersion, and the coexistence of the FE/AFE phases near the morphotropic phase boundary. The giant energy storage effect of the BNLBTZ lead-free relaxor thin fi lms may make a great impact on the modern energy storage technology.

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A brand new polysulfide entrapping strategy based on the ferroelectric effect has been demonstrated for the first time. By simply adding the nano-ferroelectrics (BaTiO nanoparticles) into the cathode, the heteropolar polysulfides can be anchored within the cathode due to the internal electric field originated from the spontaneous polarization BaTiO nanoparticles, and thus significantly improving the cycle stability of Li-S batteries.

A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range.

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