Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200 F g−1 are achieved at current densities of 0.25 and 10 A g−1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16 W h kg−1 at a power density of 75 W kg−1 and 5.5 W h kg−1 at a high power density of 3 750 W kg−1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni–MH batteries. This work provides a new platform for high‐density electrical‐energy storage for electric vehicles and other applications.

Novel composite separators containing metal–organic‐framework (MOF) particles and poly(vinyl alcohol) are fabricated by the electrospinning process. The MOF particles containing opened metal sites can spontaneously adsorb anions while allowing effective transport of lithium ions in the electrolyte, leading to dramatically improved lithium‐ion transference number tLi+ (up to 0.79) and lithium‐ion conductivity. Meanwhile, the incorporation of the MOF particles alleviates the decomposition of the electrolyte, enhances the electrode reaction kinetics, and reduces the interface resistance between the electrolyte and the electrodes. Implementation of such composite separators in conventional lithium‐ion batteries leads to significantly improved rate capability and cycling durability, offering a new prospective toward high‐performance lithium‐ion batteries.

Protein channels in biologic systems can effectively transport ions such as proton (H(+)), sodium (Na(+)), and calcium (Ca(+)) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO3 (h-WO3) which can conduct both protons and electrons. This mixed protonic-electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from h-WO3 nanorods. Such a unique h-WO3 contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the h-WO3 with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50,000 cycles without capacitance decay), thus providing a new platform for a broad range of applications.

Design and fabrication of effective electrode structure is essential but is still a challenge for current lithium-ion battery technology. Herein we report the design and fabrication of a class of high-performance robust nanocomposites based on iron oxide spheres and carbon nanotubes (CNTs). An efficient aerosol spray process combined with vacuum filtration was used to synthesize such composite architecture, where oxide nanocrystals were assembled into a continuous carbon skeleton and entangled in porous CNT networks. This material architecture offers many critical features that are required for high-performance anodes, including efficient ion transport, high conductivity, and structure durability, therefore enabling an electrode with outstanding lithium storage performance. For example, such an electrode with a thickness of ∼35 μm could deliver a specific capacity of 994 mA h g(-1) (based on total electrode weight) and high recharging rates. This effective strategy can be extended to construct many other composite electrodes for high-performance lithium-ion batteries.

Limited by the size of microelectronics, as well as the space of electrical vehicles, there are tremendous demands for lithium-ion batteries with high volumetric energy densities. Current lithium-ion batteries, however, adopt graphite-based anodes with low tap density and gravimetric capacity, resulting in poor volumetric performance metric. Here, by encapsulating nanoparticles of metallic tin in mechanically robust graphene tubes, we show tin anodes with high volumetric and gravimetric capacities, high rate performance, and long cycling life. Pairing with a commercial cathode material LiNi0.6Mn0.2Co0.2O2, full cells exhibit a gravimetric and volumetric energy density of 590 W h Kg−1 and 1,252 W h L−1, respectively, the latter of which doubles that of the cell based on graphite anodes. This work provides an effective route towards lithium-ion batteries with high energy density for a broad range of applications.

MnO 2 /carbon nanocomposites with hierarchical pore structure and controllable MnO 2 loading have been synthesized using a self-limiting growth method. This was achieved by the redox reactions of KMnO 4 with sacrificed carbon substrates that contain hierarchical pores. The unique pore structure allows the synthesis of nanocomposites with tunable MnO 2 loading up to 83 wt.%. The specific capacitance of the nanocomposites increased with the MnO 2 loading; the conductivity measured by electrochemical impedance spectroscopy, on the other hand, decreased with increasing MnO 2 loading. Optimization of the MnO 2 loading resulted in nanocomposites with high specific capacitance and excellent rate capability. This work provides important fundamental understanding which will facilitate the design and fabrication of high-performance supercapacitor materials for a large variety of applications.

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Photovoltaic (PV) effects, power-conversion efficiencies, and structures have been systematically measured in (Bi 1Àx Ca x)FeO 3Àd ceramics for x ¼ 0.05, 0.10, and 0.15. The heterostructures of indium tin oxide (ITO) film/(Bi 1Àx Ca x)FeO 3Àd ceramics/Au film exhibit significant PV effects under illumination of k ¼ 405 nm. The maximum power-conversion efficiency in the ITO/(Bi 0.90 Ca 0.10)FeO 2.95 (BFO10C)/Au can reach 0.0072%, which is larger than 0.0025% observed in the graphene/polycrystalline BFO/Pt films [Zang et al., Appl. Phys. Lett. 99, 132904 (2011)]. A theoretical model based on optically excited current in the depletion region between ITO film and Ca-doped BFO ceramics is used to describe the I-V characteristic, open-circuit voltage, and short-circuit current density as a function of illumination intensity. This work suggests that the Ca-substitution can reduce the rhombohedral distortion and stabilize the single-phase structure. V