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

Based on the Reaction-Diffusion framework, an improved NBTI model is proposed with the consideration of moving diffusion front in oxide and poly-Si layer. The dependence of degradation on channel length and width is taken into account simultaneously for the first time. The model is implemented with Verilog-A to be compatible with commercial simulators and verified by experimental data.

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An improved static NBTI Model with physical geometry scaling

In this paper, we report excellent power and radio frequency (RF) performances of GaN HEMTs grown on free-standing GaN substrate using a unified Fe/C co-doped GaN buffer. With gate-drain distance ($L_{\mathrm{gd}}$) of 6.35 $\mu$m, the device presented a low specific on-resistance ($R_{\mathrm{on}_{-}\mathrm{sp}}$) of 0.66 m$\Omega\cdot\mathrm{cm}^{2}$ and a high breakdown voltage ($V_{\mathrm{BR}}$) of 710 V. Record Johnson’s figure-of-merit (JFOM) of 16.25 THz$\cdot$V and $f_{\max}$. VBR of 38.34 THz$\cdot$V were achieved among GaN HEMTs. Load-pull measurements reveal a state-of-the-art power density of 10.2 W/mm for GaN-on-GaN HEMTs. Moreover, the GaN-on-GaN HEMTs in this work show excellent reliability and stable Schottky characteristics after the reverse gate step stress. This technology provides a unified design of material and process for GaN power and RF devices with high performance, promoting the integration of GaN-based devices on the same platform.

First Demonstration of State-of-the-art GaN HEMTs for Power and RF Applications on A Unified Platform with Free-standing GaN Substrate and Fe/C Co-doped Buffer

In this work, high linearity AlGaN/GaN HEMTs accomplished by implementing the dual-threshold coupling technique (DT HEMTs) have been studied. It was found that the transconductance (G<inf>m</inf>) profile for DT HEMTs at high operation voltage was sever compressed induced by the high electric field (E-field), and the phenomenon could be optimized by modulating the α, which was defined as the duty ratio of planar- and recess-elements in a period width. Consequently, the fabricated composite device with α = 0.7 yielded the gate voltage swing (GVS-G<inf>m</inf>) of 4.5 V at V<inf>ds</inf> = 6 V, while GVS-G<inf>m</inf> of 3.97 V at V<inf>ds</inf> = 25 V was obtained by DT HEMTs whose α is 0.5. Meanwhile, For the DT HEMTs with α = 0.5, the predicted output third-order intercept (OIP<inf>3</inf>) of 39 dBm among a wide gate voltage range at V<inf>ds</inf> = 25 V was achieved, and the large signal performance at 8 GHz delivered P<inf>out</inf> of 4.7 W/mm with 1.9 dB improvement in gain compression (G<inf>com</inf>), and 2 dB enhancement in 1-dB compression point (P<inf>1-dB</inf>), respectively, at V<inf>ds</inf> = 25V. The suppressed G<inf>com</inf> and enhanced P<inf>1-dB</inf> indicates that the DT HEMTs with α = 0.5 is capable for linearity requirements at high operation voltage.

Improved Linearity Performance at High Operation Voltage on Dual-threshold Coupling AlGaN/GaN HEMTs by Modulating the Duty Ratio

High performance millimeter-wave enhancement-mode AlGaN/GaN HEMTs using plasma oxidation technology (POT) is fabricated by PECVD. The PECVD system avoids downward bombardment making this process damage free. The POT enables the formation of a thin oxide layer on gate region, ultralow leakage was achieved on the fabricated device, I off = 9.5× 10−7 mA/mm and it has a high ON/OFF ratio of over 109, the lowest off-state leakage for the AlGaN/GaN in deep-submicrometer gate length. The enhancement-mode AlGaN/GaN HEMTs using this new oxidation technology exhibits outstanding performance including Vth of 0.4 V, maximum drain current of 1 A/mm and f max of 170 GHz.

Enhancement-mode AlGaN/GaN with plasma oxidation technology

In this letter, AlGaN/GaN Fin-HEMTs with different fin configurations were fabricated. It is found that the peak value and linearity of transconductance for AlGaN/GaN Fin-HEMTs are improved by the reduction of the fin length, which can be attributed to the modulation of source resistance by varying the fin length. The value and linearity of current cutoff frequency (fT) of AlGaN/GaN Fin-HEMTs also benefit from the improvement of the peak value and linearity of transconductance for AlGaN/GaN Fin-HEMTs.

Xiaohua Ma

Papers

An improved static NBTI Model with physical geometry scaling

First Demonstration of State-of-the-art GaN HEMTs for Power and RF Applications on A Unified Platform with Free-standing GaN Substrate and Fe/C Co-doped Buffer

Improved Linearity Performance at High Operation Voltage on Dual-threshold Coupling AlGaN/GaN HEMTs by Modulating the Duty Ratio

Enhancement-mode AlGaN/GaN with plasma oxidation technology

Improving the peak value and linearity of transconductance for AlGaN/GaN Fin-HEMTs by narrowing down the fin length