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

In this work, high-efficiency InAlN/GaN high electron mobility transistor (HEMT) is fabricated by recess and oxidation process under the gate (RAO) for low-voltage RF applications. Compared with conventional HEMT fabricated on the same heterojunction, RAO-HEMT exhibits a significant decrease in gate leakage, attributed to the thin oxide layer formed around and under the gate as well as adjustment of the location of the peak electric field and confinement of the strong electric field in the oxide. Due to the alleviated electric field as well as adoption of <inline-formula> <tex-math notation="LaTeX">$\text{N}_{{2}}\text{O}$ </tex-math></inline-formula> for plasma treatment, suppressed RF dispersion including the extremely low current collapse and negligible knee voltage walkout is obtained for RAO-HEMT. Although RAO-HEMT delivers lower saturation current as the result of the partial oxidation of the barrier under the gate, it shows a similar ON-resistance to conventional HEMT, which contributes to the reduction in knee voltage. Besides, higher <inline-formula> <tex-math notation="LaTeX">${f}_{T}/{f}_{\text {MAX}}$ </tex-math></inline-formula> is achieved for RAO-HEMT, as the result of the higher dc transconductance and suppressed RF transconductance collapse as well as larger output resistance. Eventually, benefiting from the improvement in gate leakage, RF dispersion, knee voltage, and <inline-formula> <tex-math notation="LaTeX">${f}_{\text {MAX}}$ </tex-math></inline-formula> by RAO, RAO-HEMT delivers both higher power-added-efficiency (PAE) and output power (<inline-formula> <tex-math notation="LaTeX">${P}_{\text {OUT}}$ </tex-math></inline-formula>) than conventional HEMT. At 3.6 GHz, RAO-HEMT provides a high PAE of 71% (74%) at <inline-formula> <tex-math notation="LaTeX">${V}_{{\text {DS}}}$ </tex-math></inline-formula> of 6 V (9 V), which performs better than most of the existing Si, GaAs, or GaN RF devices in PAE, revealing the great potential of InAlN/GaN RAO-HEMT in low-voltage low-power consumption RF applications.

High Efficiency Over 70% at 3.6-GHz InAlN/GaN HEMT Fabricated by Gate Recess and Oxidation Process for Low-Voltage RF Applications

Highly Stable Fibronectin-mimetic-peptide-based Supramolecular Hydrogel to Accelerate Corneal Wound Healing.

In this paper, a method of using band-pass filter for matching is presented, and the parasitic parameters of the device are used as part of the filter. This increases the frequency selectivity of the power amplifier and improves the performance of the power amplifier in the working frequency band. The inner matching power amplifier is fabricated by filter technology. When the frequency is 2GHz, the PAE of the power amplifier reaches 62.83% and the output power reaches 226W. In the whole working frequency, when the frequency is 1.8GHz-2.2GHz, PAE reaches 60% and output power reaches 150W.

The Internal Matching Power Amplifier Design Based on Band-pass Filter with Parasitic Parameter

In this letter, we present high-performance tri-gate normally-off HEMTs RF power devices using MOCVD-grown thin barrier SiN/AlN/GaN heterostructures. The normally-off devices exhibit alloyed Ohmic contact resistance of about <inline-formula> <tex-math notation="LaTeX">$0.35 \Omega \cdot $ </tex-math></inline-formula>mm, low threshold-voltage of 0.2 V, very high output current of 1.61 A/mm, and high peak power added efficiency (PAE) of 67.5% with drain voltage <inline-formula> <tex-math notation="LaTeX">${(}{V}_{\text {d}}{)}$ </tex-math></inline-formula> of 12 V and frequency at 3.6 GHz. Owing to the high breakdown voltage of 159 V when gate bias at −4 V, the normally-off device shows a maximum output power of 5.96 W/mm at <inline-formula> <tex-math notation="LaTeX">${V}_{\text {d}}$ </tex-math></inline-formula> = 28 V with a peak PAE of over 50% and gain of over 20 dB. The SiN/AlN/GaN epi-structures and tri-gate normally-off HEMTs demonstrated in this work show promising potential for both low-voltage and high-voltage applications.

Tri-Gate Normally-Off AlN/GaN HEMTs With 2.36 W/mm of Power Density and 67.5% Power-Added-Efficiency at Vd = 12 V

Negative gate voltage bias step-stress experiments were implemented to research the degradation mechanisms in AlGaN/GaN HEMTs. Although the stress gate current increases sharply above a "critical voltage" for the devices with large gate-to-source distance, no such voltage could be found when the gate-to-source distance is small. It is postulated that surface leakage current becomes prominent when the gate and source of the device come near, thus the degradation of gate leakage caused by the inverse piezoelectric effect is shield.

Xiaohua Ma

Papers

High Efficiency Over 70% at 3.6-GHz InAlN/GaN HEMT Fabricated by Gate Recess and Oxidation Process for Low-Voltage RF Applications

Highly Stable Fibronectin-mimetic-peptide-based Supramolecular Hydrogel to Accelerate Corneal Wound Healing.

The Internal Matching Power Amplifier Design Based on Band-pass Filter with Parasitic Parameter

Tri-Gate Normally-Off AlN/GaN HEMTs With 2.36 W/mm of Power Density and 67.5% Power-Added-Efficiency at Vd = 12 V

Different Gate Current Degradation Mechanisms in AlGaN/GaN High Electron Mobility Transistors