An insight into the analogies, state-of-the-art technologies, concepts, and prospects under the umbrella of perovskite materials (both inorganic-organic hybrid halide perovskites and ferroelectric perovskites) for future multifunctional energy conversion and storage devices is provided. Often, these are considered entirely different branches of research; however, considering them simultaneously and holistically can provide several new opportunities. Recent advancements have highlighted the potential of hybrid perovskites for high-efficiency solar cells. The intrinsic polar properties of these materials, including the potential for ferroelectricity, provide additional possibilities for simultaneously exploiting several energy conversion mechanisms such as the piezoelectric, pyroelectric, and thermoelectric effect and electrical energy storage. The presence of these phenomena can support the performance of perovskite solar cells. The energy conversion using these effects (piezo-, pyro-, and thermoelectric effect) can also be enhanced by a change in the light intensity. Thus, there lies a range of possibilities for tuning the structural, electronic, optical, and magnetic properties of perovskites to simultaneously harvest energy using more than one mechanism to realize an improved efficiency. This requires a basic understanding of concepts, mechanisms, corresponding material properties, and the underlying physics involved with these effects.

Mutual Insight on Ferroelectrics and Hybrid Halide Perovskites: A Platform for Future Multifunctional Energy Conversion.

Dielectric capacitors with ultrahigh power densities are fundamental energy storage components in electrical and electronic systems. However, a long-standing challenge is improving their energy densities. We report dielectrics with ultrahigh energy densities designed with polymorphic nanodomains. Guided by phase-field simulations, we conceived and synthesized lead-free BiFeO3-BaTiO3-SrTiO3 solid-solution films to realize the coexistence of rhombohedral and tetragonal nanodomains embedded in a cubic matrix. We obtained minimized hysteresis while maintaining high polarization and achieved a high energy density of 112 joules per cubic centimeter with a high energy efficiency of ~80%. This approach should be generalizable for designing high-performance dielectrics and other functional materials that benefit from nanoscale domain structure manipulation.

Ultrahigh–energy density lead-free dielectric films via polymorphic nanodomain design

This review provides a detailed overview on the latest developments in the design and control of the interface in polymer based composite dielectrics for energy storage applications. The methods employed for interface design in composite systems are described for a variety of filler types and morphologies, along with novel approaches employed to build hierarchical interfaces for multi-scale control of properties. Efforts to achieve a close control of interfacial properties and geometry are then described, which includes the creation of either flexible or rigid polymer interfaces, the use of liquid crystals and developing ceramic and carbon-based interfaces with tailored electrical properties. The impact of the variety of interface structures on composite polarization and energy storage capability are described, along with an overview of existing models to understand the polarization mechanisms and quantitatively assess the potential benefits of different structures for energy storage. The applications and properties of such interface-controlled materials are then explored, along with an overview of existing challenges and practical limitations. Finally, a summary and future perspectives are provided to highlight future directions of research in this growing and important area.

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Interface design for high energy density polymer nanocomposites

Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge-discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength. Polymer dielectric capacitors offer high power/energy density for applications at room temperature, but above 100 °C they are unreliable and suffer from dielectric breakdown. For high-temperature applications, therefore, dielectric ceramics are the only feasible alternative. Lead-based ceramics such as La-doped lead zirconate titanate exhibit good energy storage properties, but their toxicity raises concern over their use in consumer applications, where capacitors are exclusively lead free. Lead-free compositions with superior power density are thus required. In this paper, we introduce the fundamental principles of energy storage in dielectrics. We discuss key factors to improve energy storage properties such as the control of local structure, phase assemblage, dielectric layer thickness, microstructure, conductivity, and electrical homogeneity through the choice of base systems, dopants, and alloying additions, followed by a comprehensive review of the state-of-the-art. Finally, we comment on the future requirements for new materials in high power/energy density capacitor applications.

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives

A novel lead-free polar dielectric ceramic with linear-like polarization responses was found in (1 − x)(Bi0.5Na0.5)TiO3–xNaNbO3 ((1 − x)BNT–xNN) solid solutions, exhibiting giant energy storage density/efficiency and super stability against temperature and frequency. High-resolution transmission electron microscopy, Raman scattering and Rietveld refinements of X-ray diffraction data suggest that these property characteristics can be derived from temperature and electric field insensitive large permittivity as a result of relaxor antiferroelectricity (AFE) with polar nanoregions. Additionally, this feature intrinsically requires a high driving field for AFE to ferroelectric (FE) phase transitions due to large random fields. Measurements of temperature-dependent permittivity and polarization versus electric field hysteresis loops indicate that the high-temperature AFE P4bm phase in BNT was gradually stabilized close to room temperature, accompanying a phase transition from relaxor rhombohedral FEs to relaxor tetragonal AFEs approximately at x = 0.15–0.2. A record high of recoverable energy-storage density W ∼ 7.02 J cm−3 as well as a high efficiency η ∼ 85% was simultaneously achieved in the x = 0.22 bulk ceramic, which challenges the existing fact that W and η must be seriously compromised. Furthermore, desirable W (>3.5 J cm−3) and η (>88%) with a variation of less than 10% can be accordingly obtained in the temperature range of 25–250 °C and frequency range of 0.1–100 Hz. These excellent energy-storage properties would make BNT-based lead-free AFE ceramic systems a potential candidate for application in pulsed power systems.

Linear-like lead-free relaxor antiferroelectric (Bi0.5Na0.5)TiO3–NaNbO3 with giant energy-storage density/efficiency and super stability against temperature and frequency

Perovskite lead-free dielectrics for energy storage applications

Relaxor ferroelectric ceramics have attracted much attention for storing the electricity generated from clean and renewable energy sources due to their high permittivity and near-zero remnant polarization. The polarization of many relaxor based ceramics tends to saturate at high electric fields, however, which limits their energy storage performance. In this study, a lead-free Sn-modified (Na0.5Bi0.5)TiO3–SrTiO3 system is investigated, where mitigated polarization saturation is observed with the addition of Sn4+, as a result of the different electronic configurations between d10 Sn4+ and d0 Ti4+. As expected, high energy density of 3.4 J cm−3 and energy efficiency of 90% are simultaneously achieved in (Na0.25Bi0.25Sr0.5)(Ti0.8Sn0.2)O3 ceramic. In addition, the ceramic exhibits good thermal stability, with the energy storage property variations below 5% over the temperature range of −20 °C to 150 °C, and satisfactory cycling stability with a variation of less than 8% over 105 cycles. All these merits demonstrate that the (Na0.25Bi0.25Sr0.5)(Ti0.8Sn0.2)O3 ceramic has great potential for high power energy storage applications.

Ultra-high energy storage performance with mitigated polarization saturation in lead-free relaxors

Bi-modified SrTiO3-based ceramics for high-temperature energy storage applications

Sodium niobate (NaNbO3)-based lead-free ceramics have
been actively studied for energy storage applications because of their
antiferroelectric and/or relaxor features achieved in modified systems
The P–E loops of NaNbO3-based ceramics are usually hysteretic because of the existence
of a metastable ferroelectric phase at room temperature In this study,
by introducing aliovalent cations and A-site vacancies, the relaxor
characteristics are greatly enhanced in (Na1–2xBix)­(Nb1–xZrx)­O3 ceramics,
leading to a high energy storage efficiency of above 90% In addition,
sintering aid CuO and a special ramp-to-spike sintering profile were
employed to decrease the sintering temperature and reduce the grain
size The modified ceramic exhibits improved insulating properties
and hence a higher breakdown strength, leading to a high recoverable
energy density of 49 J/cm3 and a high energy efficiency
of 88% at 430 kV/cm The ceramic also exhibits satisfactory temperature
stability over a wide temperature range from 25 to 125 °C and
charge–discharge performance, making it a promising candidate
for high-power dielectric energy storage applications

Enhanced Energy Storage Performance of Sodium Niobate-Based Relaxor Dielectrics by a Ramp-to-Spike Sintering Profile.

New artificial in-plane heterojunctions based on two-dimensional transition metal dichalcogenides fabricated in recent reports are considered able to offer great scope for applications. Here, we study by first principles calculations the adsorption of CO, H2O, NH3, NO, and NO2 gas molecules on the MoS2/WS2 heterojunction. We have determined the optimal adsorption positions and the adsorption strength, which is driven by charge transfer between the molecules and the heterojunction. Except NH3, which performs as the charge donor, all the other studied molecules act as charge acceptors to the heterojunction. The charge transfer mechanism has been discussed by analyzing the electronic structure of the molecules and the heterojunction. Further calculations show that the molecule adsorption significantly affects the electronic transport properties of the heterojunction. Both the rectification behavior and the value of the passing current can be altered by adsorption, and such sensitivity to adsorption makes the heterojunction a superior gas sensor that promises wide-ranging applications.

Letao Yang

Papers

Perovskite lead-free dielectrics for energy storage applications

Ultra-high energy storage performance with mitigated polarization saturation in lead-free relaxors

Bi-modified SrTiO3-based ceramics for high-temperature energy storage applications

Enhanced Energy Storage Performance of Sodium Niobate-Based Relaxor Dielectrics by a Ramp-to-Spike Sintering Profile.

Gas adsorption on MoS2/WS2 in-plane heterojunctions and the I–V response: a first principles study