There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Solid-state electrolytes are attracting increasing interest for electrochemical energy storage technologies. In this Review, we provide a background overview and discuss the state of the art, ion-transport mechanisms and fundamental properties of solid-state electrolyte materials of interest for energy storage applications. We focus on recent advances in various classes of battery chemistries and systems that are enabled by solid electrolytes, including all-solid-state lithium-ion batteries and emerging solid-electrolyte lithium batteries that feature cathodes with liquid or gaseous active materials (for example, lithium–air, lithium–sulfur and lithium–bromine systems). A low-cost, safe, aqueous electrochemical energy storage concept with a ‘mediator-ion’ solid electrolyte is also discussed. Advanced battery systems based on solid electrolytes would revitalize the rechargeable battery field because of their safety, excellent stability, long cycle lives and low cost. However, great effort will be needed to implement solid-electrolyte batteries as viable energy storage systems. In this context, we discuss the main issues that must be addressed, such as achieving acceptable ionic conductivity, electrochemical stability and mechanical properties of the solid electrolytes, as well as a compatible electrolyte/electrode interface. This Review details recent advances in battery chemistries and systems enabled by solid electrolytes, including all-solid-state lithium-ion, lithium–air, lithium–sulfur and lithium–bromine batteries, as well as an aqueous battery concept with a mediator-ion solid electrolyte.

Lithium battery chemistries enabled by solid-state electrolytes

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

羟氨苄青霉素引起大疱性类天疱疮样疹

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

High-performance AlGaN/GaN lateral Schottky barrier diodes (SBDs) with recess structure and dual metal nitride anodes were demonstrated. With high work-function and nonrecess structure, a NiN anode enhances the breakdown voltage (BV), while a TiN anode reduces the turn-on voltage ( ${V}_{ \mathrm{\scriptscriptstyle ON}}$ ) due to its low work-function and contact to the two-dimensional electron gas (2DEG) layer directly on a recess structure. As the length of the NiN anode ( ${L}_{r}$ ) on the nonrecess region decreases from 75 to 3 $\mu \text{m}$ , ${V}_{ \mathrm{\scriptscriptstyle ON}}$ is reduced from 0.56 to 0.30 V, while the reverse leakage current slightly increases from ${3} \times {10}^{-{4}}$ to ${2} \times {10}^{-{3}}$ A/cm2 at the bias of −10 V. The lateral AlGaN/GaN SBD with a ${L}_{r}$ of 3 $\mu \text{m}$ at a distance of cathode–anode ( ${L}_{\text {AC}}$ ) of 20 $\mu \text{m}$ achieves a high BV of 1.62 kV, an ultralow ${V}_{ \mathrm{\scriptscriptstyle ON}}$ of 0.30 V and a small capacitance of 6.0 pF at zero bias with little degradation on ON-resistance, indicating superior potential application in high-frequency and high-power devices.

Recessed AlGaN/GaN Schottky Barrier Diodes With TiN and NiN Dual Anodes

Substrate integrated waveguide (SIW) structural transmission line (TL) and filter are designed and fabricated on semi-insulating silicon carbide (SiC) substrates for operation at the low end of $H$ -band. The via-holes as the sidewall of SIW are achieved by using a fine dry-etching technique, where the radius and the via–via distance of the via-hole row are determined according to the transmission characteristics and the fabrication process. Measurements show that SIW-based TLs have the attenuation constant of as low as 0.45 dB/mm at 220 GHz, a third of that for TLs on grounded coplanar waveguide, and SIW-structural filters have the minimum insertion loss of <1 dB at the center frequency of 183 GHz with a bandwidth of 5.3 %. It illustrates the availability of passive device fabrications on SiC substrate, and paves the way for the forthcoming terahertz monolithic integrated circuits based on wide bandgap semiconductors.

Substrate Integrated Waveguide Structural Transmission Line and Filter on Silicon Carbide Substrate

We propose an innovative recessed float field plate (RFFP) structure for millimeter-wave AlGaN/GaN high-electron-mobility transistors (HEMTs). The reduced peak electric field contributes to a three-terminal breakdown voltage of 122–140 V for RFFP GaN HEMTs with L GD = 1.35 μm, which is found to increase from 84 to 101 V. The current collapse characteristic is also improved significantly. No obvious increase in parasite capacitance is observed after integrating the novel RFFP, thereby maintaining the high-frequency performance of GaN HEMTs. This technique is especially attractive for HEMTs of millimeter-wave frequency and above, and has great potential for applications.

https://iopscience.iop.org/article/10.7567/1882-0786/ab196c/pdf

Millimeter-wave AlGaN/GaN HEMT breakdown voltage enhancement by a recessed float field plate

In this work, the capping layer atop anodic TiO2 nanotube arrays (NTAs), which hinders filling of other guest materials and transport of charge carriers, is discerned to be TiO2 nanotapes. Then, it is completely removed by a novel sonication-polishing (SP) treatment, after which Sb2S3 is subsequently introduced to fill the nanotubes by chemical bath deposition. The morphological, structural, and optical properties of the SP-treated TiO2 NTAs and TiO2 NTAs/Sb2S3 heterogeneous structures are characterized systematically. The results indicate that SP treatment opens the tops of nanotubes with diameters of ∼120 nm, which endure a phase conversion from amorphous to anatase after calcination at 450 °C; besides, stibnite Sb2S3 with a band gap of ∼1.75 eV inside the TiO2 networks is formed upon heat treatment at 330 °C in Ar, which enhances the absorption in visible light range. The photoelectrochemical (PEC) and photovoltaic properties for the SP-treated TiO2 NTAs are investigated. Results shows that the photoresponse of TiO2 NTAs is improved by the SP treatment, and the photocurrent for the TiO2 NTAs/Sb2S3 electrode is substantially enhanced as compared to the bare TiO2 one. A high efficiency of 6.28 % is achieved in a TiO2 NTAs/Sb2S3 PEC cell. In addition, charge recombination in the photoanode of dye-sensitized solar cells (DSSCs) is observed to be greatly retarded by using the SP-treated TiO2 NTAs as compared to TiO2 nanoparticles (NPs). Thus, the SP anodic TiO2 NTAs are promising in applications in various PEC areas such as photocatalysis and sensitized solar cells.

Xiaohua Ma

Papers

Recessed AlGaN/GaN Schottky Barrier Diodes With TiN and NiN Dual Anodes

Substrate Integrated Waveguide Structural Transmission Line and Filter on Silicon Carbide Substrate

Millimeter-wave AlGaN/GaN HEMT breakdown voltage enhancement by a recessed float field plate

Sonication-polished anodic TiO 2 nanotube array-based photoanode for efficient solar energy conversion

Influence of fin width and gate structure on the performance of AlGaN/GaN fin‐shaped HEMTs