Enhanced Energy Storage Performance of Lead-Free Capacitors in an Ultrawide Temperature Range via Engineering Paraferroelectric and Relaxor Ferroelectric Multilayer Films

Industry has been seeking a thin-film capacitor that can work at high temperature in a harsh environment, where cooling systems are not desired. Up to now, the working temperature of the thin-film capacitor is still limited up to 200 °C. Herein, we design a multilayer structure with layers of paraferroelectric (Ba0.3Sr0.7TiO3, BST) and relaxor ferroelectric (0.85BaTiO3–0.15Bi(Mg0.5Zr0.5)O3, BT–BMZ) to realize optimum properties with a flat platform of dielectric constant and high breakdown strength for excellent energy storage performance at high temperature. Through optimizing the multilayer structure, a highly stable relaxor ferroelectric state is obtained for the BST/BT–BMZ multilayer thin-film capacitor with a total thickness of 230 nm, a period number N = 8, and a layer thickness ratio of BST/BT–BMZ = 3/7. The optimized multilayer film shows significantly improved energy storage density (up to 30.64 J/cm3) and energy storage efficiency (over 70.93%) in an ultrawide temperature range from room temperature to 250 °C. Moreover, the multilayer system also exhibits excellent thermal stability in such an ultrawide temperature range with a change of 5.15 and 12.75% for the recoverable energy density and energy storage efficiency, respectively. Our results demonstrate that the designed thin-film capacitor is promising for the application in a harsh environment and open a way to tailor a thin-film capacitor toward higher working temperature with enhanced energy storage performance

Regulating Surface and Grain-Boundary Structures of Ni-Rich Layered Cathodes for Ultrahigh Cycle Stability

The wide applications of Ni-rich LiNi1-x-yCoxMnyO2 cathodes are severely limited by capacity fading and voltage fading during the cycling process resulting from the pulverization of particles, interfacial side reactions, and phase transformation. The canonical surface modification approach can improve the stability to a certain extent; however, it fails to resolve the key bottlenecks. The preparation of Li(Ni0.4Co0.2Mn0.4)(1-)xTixO2 on the surface of LiNi0.8Co0.1Mn0.1O2 particles with a coprecipitation method is reported. After sintering, Ti diffuses into the interior and mainly distributes along surface and grain boundaries. A strong surface and grain boundary strengthening are simultaneously achieved. The pristine particles are fully pulverized into first particles due to mechanical instability and high strains, which results in serious capacity fading. In contrast, the strong surface and the grain boundary strengthening can maintain the structural integrity, and therefore significantly improve the cycle stability. A general and simple strategy for the design of high-performance Ni-rich LiNi1-x-yCoxMnyO2 cathode is provided and is applicable to surface modification and grain-boundary regulation of other advanced cathodes for batteries

Atomic Scale Understanding of the Epitaxy of Perovskite Oxides on Flexible Mica Substrate

The excellent functionalities of perovskite oxides and the growing demands for flexible devices lead to great interests on epitaxial growth of functional oxide films on flexible mica substrates. Understanding the film epitaxy on the substrate with a very different crystal structure is a key issue for the optimization of the film growth and hence properties. Such understanding largely depends on knowing the atomic structure of the interfaces between the films and the substrates. Here, the interface between the epitaxial films of SrTiO3 on the fluorophlogopite mica substrate is studied in detail. Two types of interfaces, clean or with secondary phase, exist in this system, leading to two types of crystallographic orientation relationships. Atomic‐resolution scanning transmission electron microscopy images reveal that at the clean interface the (111) Sr–O3 atomic plane of SrTiO3 interacts with the (001) (SiAl)2–O3 plane of mica. This interface structure and thus the epitaxy of the film are understood in light of the strong similarity of the oxygen sublattices in these two atomic planes. First‐principles calculations demonstrate strong bonding of the atoms at the interface, which is also corroborated by the observation of misfit dislocations at the interfaces

Green, Biodegradable, Underwater Superoleophobic Wood Sheet for Efficient Oil/Water Separation

Superwettable (by water or oil) materials have been used in oil/water separation to cope with the growing oily industrial sewage discharge and oil spill accidents. The artificial superwetting materials for oil/water separation that have been previously reported are expensive, and using them usually causes secondary pollution, so practical, large-scale uses of those materials are limited. Here, we find that wood sheet shows underwater superoleophobicity and low oil adhesion in water, resulting from its strong capacity of absorbing water. A through-microhole array was created on the wood sheet surface by a simple mechanical drilling process. The prewetted porous sheet had great ability to separate the mixtures of water and oil with high separation efficiency. Wood is a low cost, green, and natural eco-friendly material; therefore, we believe that such a simple, low-cost, efficient, and green route of large-scale oil/water separation has great potential to practically solve the pollution problems caused by oil spill and oily industrial wastewater

Green, Biodegradable, Underwater Superoleophobic Wood Sheet for Efficient Oil/Water Separation

Superwettable (by water or oil) materials have been used in oil/water separation to cope with the growing oily industrial sewage discharge and oil spill accidents. The artificial superwetting materials for oil/water separation that have been previously reported are expensive, and using them usually causes secondary pollution, so practical, large-scale uses of those materials are limited. Here, we find that wood sheet shows underwater superoleophobicity and low oil adhesion in water, resulting from its strong capacity of absorbing water. A through-microhole array was created on the wood sheet surface by a simple mechanical drilling process. The prewetted porous sheet had great ability to separate the mixtures of water and oil with high separation efficiency. Wood is a low cost, green, and natural eco-friendly material; therefore, we believe that such a simple, low-cost, efficient, and green route of large-scale oil/water separation has great potential to practically solve the pollution problems caused by oil spill and oily industrial wastewater

Realization of high energy density in an ultra-wide temperature range through engineering of ferroelectric sandwich structures

Thin film dielectrics are the most selected materials for many power electronics owing to their inherent advantages, such as high power density, fast charging-discharging, and long lifetime. Nowadays, additional demands for the film dielectrics are the high performances under harsh operating conditions, e.g. at high temperatures, which is highly favourable to significantly reduce the size and cost of energy devices. Here, we demonstrated that through design and optimization of the film systems with 1 mol% SiO2-doped BaZr0.35Ti0.65O3 layer sandwiched between two undoped BaZr0.35Ti0.65O3 layers, it is capable to concomitantly enhance breakdown strength and electrical polarization of the systems. The optimized sandwich-structure films yield a greatly improved discharged energy densities of ~130.1 J/cm3 with a high charge-discharge efficiency of ~73.8% at room temperature, as well as retain an ultrahigh discharged energy densities of ~77.8 J/cm3 in the ultra-wide temperature range from −100 to 200 °C. The presented combination of property modulation with structure engineering paves an effective way to meet the increasingly technological challenges and the requirements of modern electrical energy storage applications