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A tanghulu-like NiO microcubes on Co 3 O 4 nanowires array anchored on Ni foam was prepared via a facile method. As a pseudocapacitor electrode, the hybrid array exhibits a specific capacitance as high as 2691 mF cm -2  at 2 mA cm −2 and good cycling stability of 84.62% retention after 2000 cycles. Remarkably, the NiO/Co 3 O 4 /NF composite demonstrates about 2 times higher specific capacitance than that of Co 3 O 4 /NF precursor at a current density of 2 mA cm −2 . The improved electrochemical performance could be attributed to the synergistic effect of uniqure tanghulu-like wire-penetrated-cube hybrid arrays on Ni foam conductive substrate. Most importantly, a red light-emitting diode (LED) can be illuminated by two connected ASCs, indicating that as-synthesized NiO/Co 3 O 4 /NF possesses great potential for practical applications. [ABSTRACT FROM AUTHOR]

Hollow double–shelled NiO nanospheres have been successfully prepared by the calcination of Ni–based MOF precursor at proper temperatures. The morphology and phase structure of NiO samples were characterized by SEM, TEM, XRD and FTIR. Electrochemical studies indicate that NiO nanospheres obtained under different conditions have distinct electrochemical performances. Hollow double–shelled NiO nanospheres calcined at 400 °C (N400) exhibit the best charge storage with a specific capacitance of 473 F g −1 at the current density of 0.5 A g −1 and with 94% capacitance retention even after 3000 cycling tests. For this merits, the N400//active carbon (AC) asymmetric supercapacitor (ASC) was assembled to examine the practical application of the N400 sample, which presents high energy density of 21.4 Wh kg −1 at power density of 375.8 W kg −1 . Particularly, the N400//AC ASC exhibits outstanding cycling stability, and its capacitance retention can still reach up to 92.3% after 3000 cycles. These results indicate that the N400 sample is a promising electroactive candidate for supercapacitors. [ABSTRACT FROM AUTHOR]

Dielectric ceramic materials with high energy-storage density and excellent charge-discharge performance are desirable for use in dielectric capacitors. In this study, (Na 0.5 Bi 0.5) 0.75 Sr 0.25 TiO 3 – x Nb 2 O 5 (denoted as NBSTN x) lead-free ceramics were prepared by a solid-state reaction method. Polarization-electric field hysteresis loops (P–E loops) reflected the energy storage characteristics of the NBSTN x ceramics. Introducing Nb into a pure NBST ceramic can reduce the large remnant polarization (P r) and make the P–E loops slimmer. Through repeated trials and calculations, the maximum recoverable energy-storage density (W rec ~ 3.25 J/cm3) and energy storage efficiency (η ~ 74.5%) were achieved for the NBSTN 0.03 ceramic at 140 kV/cm. We also tested the stability performance of the NBSTN x ceramics, where the NBSTN 0.03 ceramic exhibited the highest thermal stability (30–100 °C) and frequency stability (10–1000 Hz). The NBSTN 0.03 ceramic also had a fast discharge rate (<300 ns) and a good discharge energy-storage density (W d ~ 1.80 J/cm3). Therefore, the NBSTN 0.03 ceramic with a good energy-storage density and charge-discharge performance has excellent application prospects for practical dielectric capacitors. [Display omitted] • A strategy incorporating B-site doping to enhance energy storage performance. • A relatively high W rec of 3.25 J/cm3 and η of 74.5%. • Sample with 0.03 mol Nb doping shows relatively good temperature and frequency stability. [ABSTRACT FROM AUTHOR]