Dielectric capacitors are the key components in advanced electronics and electrical systems owing to their highest power density among the electrical energy devices. [1][2][3][4][5][6][7] While ceramic dielectrics are of large dielectric constants and high thermal stability, [8][9][10][11][12] polymer dielectrics possess high tolerance to voltage, great reliability, scalability, and light weight, and therefore are preferred for high-energy-density high-power film capacitors. [13][14][15][16][17] However, the current polymer dielectrics are unable to match the temperature requirements of the emerging applications of electrical energy storage and conversion in harsh environments [18][19][20][21][22] because of their inherently poor thermal stability. For example, while the near-engine-temperature in electric vehicles can reach to above 120 °C, [23] the operating temperature of biaxially oriented polypropylene (BOPP), which is the best commercially available polymer dielectric and currently used in power inverters of electric vehicles, is below 105 °C. [24] The wide bandgap semiconductors like silicon carbide (SiC) and gallium nitride that are well positioned to replace traditional silicon power devices boost the operating temperatures of next-generation capacitors beyond 150 °C. [19] To address these urging needs, a variety of engineering polymers with high thermal stability, such as polyimides (PIs) and fluorene polyesters (FPEs), have been exploited as high-temperature dielectric materials. [20,25] Unfortunately, all the polymers show poor charge-discharge efficiencies under elevated temperatures and high applied fields, [26] which is due to sharply increased electrical conduction attributable to various temperature-and field-dependent conduction mechanisms, e.g., charge injection at the electrode/dielectric interface. [27,28] Ceramic dielectrics are relatively insensitive to temperature and able to maintain the energy-storage performance throughout a broad temperature range, [8][9][10][11][12] but they still suffer from considerable energy loss under high electric fields and elevated temperatures. [29] More recently, the addition of 2D wide bandgap nanostructures such as boron nitride nanosheets (BNNSs) into the polymer has been demonstrated to effectively reduce the conduction loss and largely improve the charge-discharge High-temperature capability is critical for polymer dielectrics in the nextgeneration capacitors demanded in harsh-environment electronics and electrical-power applications. It is well recognized that the energy-storage capabilities of dielectrics are degraded drastically with increasing temperature due to the exponential increase of conduction loss. Here, a general and scalable method to enable significant improvement of the high-temperature capacitive performance of the current polymer dielectrics is reported. The high-temperature capacitive properties in terms of discharged energy density and the charge-discharge efficiency of the polymer films coated with SiO 2 via plasma-enhanced chemical...

A design methodology for developing lead-free bulk ceramics with large recoverable energy storage density was proposed in this study.

Present one-step N 2 fixation is impeded by tough activation of the NNb ond and low selectivity to NH 3 .H ere we report fixation of N 2 -to-NH 3 can be decoupled to atwo-step process with one problem effectively solved in each step, including:1)facile activation of N 2 to NO x À by anon-thermal plasma technique,a nd 2) highly selective conversion of NO x À to NH 3 by electrocatalytic reduction. Importantly,this process uses air and water as low-cost raw materials for scalable ammonia production under ambient conditions.F or NO x À reduction to NH 3 ,w ep resent as urface boron-richc ore-shell nickel boride electrocatalyst. The surface boron-rich feature is the key to boosting activity,s electivity,a nd stability via enhanced NO x À adsorption, and suppression of hydrogen evolution and surface Ni oxidation. As ignificant ammonia production of 198.3 mmol cm À2 h À1 was achieved, together with nearly 100 %F aradaic efficiency.