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

Ultra-Wide Bandgap Quasi Two-Dimensional Β-Ga2o3 with Highly In-Plane Anisotropy for Power Electronics

In this letter, the AlGaN/GaN/graded-AlGaN:Si-doped/GaN double channel (GDC-SI) high electronic mobility transistors (HEMTs) with high saturation current density and linearity have been reported for low voltage applications. Compared with the standard AlGaN/GaN/AlGaN/GaN double channel GaN (SDC) HEMTs, the GDC-SI HEMTs exhibited the higher saturation current, the broader and flatter transconductance profile, the lower transconductance (<inline-formula> <tex-math notation="LaTeX">${g}_{\text {m}}{)}$ </tex-math></inline-formula> derivatives, and lower on-resistance (<inline-formula> <tex-math notation="LaTeX">${R}_{\text {on}}{)}$ </tex-math></inline-formula>. Due to the Si-doped graded bottom barrier present in GDC-SI HEMTs, the profile of current gain cutoff frequency (<inline-formula> <tex-math notation="LaTeX">${f}_{\text {T}}{)}$ </tex-math></inline-formula> and the maximum oscillation frequency (<inline-formula> <tex-math notation="LaTeX">${f}_{\text {max}}{)}$ </tex-math></inline-formula> were flatter with the bias voltage increased. The output power density of 0.75 W/mm and power added efficiency (PAE) of 58% were achieved for GDC-SI HEMTs, at the drain voltage of 7 V and the test frequency of 3.6GHz. The output third-order intercept point (OIP3) of 39.3 dBm and saturation current density of 1909 mA/mm are achieved, which are the state-of-the-art saturation current and OIP3 in the double-channel GaN HEMTs.

High Current and Linearity AlGaN/GaN/-Graded-AlGaN:Si-doped/GaN Heterostructure for Low Voltage Power Amplifier Application

Formation and Increased Photoelectrochemical Properties of Free-Standing Nanoporous GaN-Based MQW Photoanodes Embedded on Nanoporous GaN Reflectors

In this work, we have studied the degradation of AlGaN/GaN MIS-HEMTs under reverse gate stress. It found that the origin of the threshold voltage shift (ΔVTH) is not derived from the barrier layer defect, but is closely related to the gate dielectric layer. In order to investigate it, two types of trap states (traps A and B) with different properties in AlGaN/GaN MIS-HEMTs gate dielectrics were proposed and studied by the constant stress-recovery experiment and thermal detrapping technique. Trap A is related to the precursor defect with transient characteristics. Trap B with permanent characteristics is newly generated during the stress, which dominates the permanent degradation and induces the breakdown. Furthermore, according to the measurement results of ΔVTH and injected-electron density (Ninj), the capture cross sections of traps A and B have been extracted, which are 5.52 × 10−21cm2 and 1.38 × 10−22cm2, respectively. 

Characterization of different trap states in AlGaN/GaN MIS-HEMTs under high reverse gate stress

Molybdenum disulfide (MoS2) has been deemed as one of the promising noble-metal-free electrocatalysts for hydrogen evolution reaction (HER), but it suffers from the inert basal plane and low electronic conductivity. Regulating the morphology of MoS2 during the synthesis on conductive substrates is a synergistic strategy for enhancing the HER performance. In this work, vertical MoS2 nanosheets were fabricated on carbon cloth (CC) using an atmospheric pressure chemical vapor deposition method. The growth process could be effectively tuned through introducing hydrogen gas during vapor deposition process, resulting in nanosheets with increased edge density. The mechanism for edge-enriching through controlling the growth atmosphere is systematically studied. The as-prepared MoS2 exhibits excellent HER activity due to the combination of optimized microstructures and coupling with CC. Our findings provide new insights to design advanced MoS2-based electrocatalysts for HER.

Xiaohua Ma

Papers

Ultra-Wide Bandgap Quasi Two-Dimensional Β-Ga2o3 with Highly In-Plane Anisotropy for Power Electronics

High Current and Linearity AlGaN/GaN/-Graded-AlGaN:Si-doped/GaN Heterostructure for Low Voltage Power Amplifier Application

Formation and Increased Photoelectrochemical Properties of Free-Standing Nanoporous GaN-Based MQW Photoanodes Embedded on Nanoporous GaN Reflectors

Characterization of different trap states in AlGaN/GaN MIS-HEMTs under high reverse gate stress

Vertically molybdenum disulfide nanosheets on carbon cloth using CVD by controlling growth atmosphere for electrocatalysis