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

Integration of polycrystalline diamond heat spreader with AlGaN/GaN HEMTs using a dry/wet combined etching process

The DC and RF characteristics of double-channel AlGaN/GaN FinFETs are analyzed. The linear operating characteristics of the double-channel AlGaN/GaN FinFET are investigated in detail. The simulated results show that the double-channel AlGaN/GaN heterostructure with doped barriers can improve the drain current, and the FinFET structure can enhance the control of the gate to the channel. The combination of FinFET structure and double-channel AlGaN/GaN heterostructure improves the gate voltage swing under DC conditions. The double-channel FinFET can effectively improve the gate bias-dependent current-gain cutoff frequency(fT) and unit-power-gain frequency(fmax) behaviors, which correlates with the broader transconductance characteristic of the double-channel FinFET.

Study on High-Linearity Devices Based on Double-Channel AlGaN/GaN FinFET Structure

Development of high permeability nanofiltration membranes through porous 2D MOF nanosheets

In this work, a new small-signal model (SSM), which is called the distributes intrinsic subdevice model (DISDM), is established for AlGaN/gallium nitride (GaN) Fin-like high-electron mobility transistors (HEMTs) according to the device structure feature. Perfect agreements between the measured and simulated scattering parameters (S-parameters) illustrated the validity of the DISDM and the accuracy of parameters extracted from the new model. Then, the characteristics of Fin-like HEMTs are analyzed using the DISDM theoretically. Different from the traditional model, the DISDM can accurately show the characteristics of the Fin-like HEMTs, especially the “double-peak” of the intrinsic transconductance. Compared with the planar HEMTs, the Fin-like HEMTs exhibit a higher linearity in direct current and small-signal parameters. For Fin-like HEMTs with different recess depths and duty ratios, the variation of the small-signal parameters and the linearity of devices were characterized to evaluate the performance of devices and optimize the process in the end.

Influence of Fin-Like Configuration on Small-Signal Performance of AlGaN/GaN HEMTs

In this work, high performance InAlN/GaN HEMT based on the n+GaN regrown ohmic contact with n+GaN contact ledge structure is proposed. The regrown ohmic contact of InAlN/GaN HEMT is formed by MBE n+GaN regrowth and self-stopping etching, which makes the total ohmic contact resistance between the 2DEG channel and the ohmic metal decrease to $0.12 \Omega \cdot $ mm and forms n+GaN contact ledge structure. Owing to the n+GaN contact ledge on the InAlN barrier, with the increasing of drain-source voltage (VDS), an additional current path comes into being between the n+GaN contact ledge on the InAlN barrier and the 2DEG channel, which can “shorten” the device effective drain-source distance, thus further reducing the parasitic resistance. Compared with regrown InAlN/GaN HEMT without n+GaN contact ledge structure, the peak transconductance (Gm.max) of regrown InAlN/GaN HEMT with n+GaN contact ledge structure increases from 747 mS/mm to 874 mS/mm, and the saturation current density (ID.max) increases from 2.6 A/mm to 2.9 A/mm. Besides, the self-stopping etching on the access region does not induce extra defects, and negligible current collapse is obtained. As the results of low parasitic resistance, high output current density, low knee voltage and negligible current collapse, power-added-efficiency (PAE) of 44% together with output power density (Pout) of 2.5 W/mm is achieved at 30 GHz and $V_{\mathrm{ DS}}$ of 10 V, which indicates regrown InAlN/GaN HEMT with n+GaN contact ledge structure has great potential for millimeter-wave low voltage applications. Additionally, the transfer and schottky gate characteristics show negligible degradation after OFF/ON-state electrical stress tests.

https://ieeexplore.ieee.org/ielx7/6245494/6423298/10008094.pdf

Xiaohua Ma

Papers

Integration of polycrystalline diamond heat spreader with AlGaN/GaN HEMTs using a dry/wet combined etching process

Study on High-Linearity Devices Based on Double-Channel AlGaN/GaN FinFET Structure

Development of high permeability nanofiltration membranes through porous 2D MOF nanosheets

Influence of Fin-Like Configuration on Small-Signal Performance of AlGaN/GaN HEMTs

InAlN/GaN HEMT With n+GaN Contact Ledge Structure for Millimeter-Wave Low Voltage Applications