Negligible Voltage Drop Research Articles

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials

AbstractSodium‐ion batteries (SIBs) as a promising technology for large‐scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode‐electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra‐stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM‐CS‐GMg) cathode material in which a Mg‐free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg‐hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered‐to‐rock‐salt phase transition and the resultant microcracks. Besides, the less formation of high‐valence TM ions on the surface contributes to a stable cathode‐electrolyte interface. The as‐prepared NCM‐CS‐GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials.

Sodium-ion batteries (SIBs) as a promising technology for large-scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode-electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra-stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM-CS-GMg) cathode material in which a Mg-free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg-hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered-to-rock-salt phase transition and the resultant microcracks. Besides, the less formation of high-valence TM ions on the surface contributes to a stable cathode-electrolyte interface. The as-prepared NCM-CS-GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

An electrical power control system for explorer-class remotely operated underwater vehicle (ROV)

The importance of an optimal method for electric power transmission is crucial for ROV operation. Meanwhile, only few studies have shown the effect of electrical power system from power supply to ROV.This paper proposes a design and implementation of electrical power system for ROV that developed by Tech_SAS team from Telkom University, Bandung, Indonesia. This work aims to obtain the optimal power system to supply ROV’s electrical and electronic components. Tech_SAS ROV is developed to compete on 1st and 2nd ASEAN MATE Underwater Robotic Competition. The system has demonstrated that 48V electric voltage can be transmitted to ROV with negligible voltage drop when using 20 meter 12AWG cable. The voltage is converted to 12V using DC-DC converter in order to supply various ROV’s electronic devices ROV safely and efficiently. Meanwhile, the microcontroller was used to as thrust control to manage current flow to DC motor. The system has been evaluated and demonstrates optimal results and provides a design consideration about ROV’s power system especially on tether cable and power distribution scheme.

High stability near-broken gap junction for multijunction photovoltaics

High performance tunnel junctions were made from sputtered and annealed p-type CuAlO2 and n-type ZnSnO3 with suitable band alignment for both low resistance and alignment to typical inorganic materials needed for a tandem solar cell. The devices not only exhibit low resistance, they are also thermally stable, capable of sustaining postdeposition temperatures up to 600 °C. This is a key requirement for many high performance multijunction thin film inorganic solar cells. The CuAlO2 top-layer remains amorphous, providing a diffusion barrier for top cell stack processing. The materials’ stack gives a negligible voltage drop, and the visible-spectrum transparency is near 100%. XPS measurements show that unannealed Cu in the Cu-Al-O films is in the +2 oxidation state, while in the films annealed at 500 °C and above, Cu is in the +1 oxidation state. This suggests that annealing is necessary to form CuAlO2. A near-broken gap alignment provides a low resistance contact with band alignment that is nearly ideal for a tandem device.

Fast AC reactor‐based fault current limiters application in distribution network

Almost all of the fault current limiters (FCLs) have a negligible voltage drop during normal operation mode of the power system and show considerable impedance during the fault period. In addition, the most of the FCLs employ a reactor to limit the fault current, which carrying a DC current and named DC reactor-based FCL (DRFCL) or carrying AC current named AC reactor-based FCL (ARFCL). Here, a novel ARFCL is introduced for radial distribution networks protection. Then, the ARFCL performance on the limitation of the fault current is compared with DRFCL in a simple radial distribution network. The MATLAB software is used to simulate both FCLs performance and their effect on the fault current. The laboratory prototype of the ARFCL is built and tested for the evaluation of the ARFCL performance during normal and fault operation modes. The simulation and experimental results show the superiority of ARFCL to control the fault current, fast, and set the point of common coupling voltage in an acceptable range.

Enhanced Stability and Electrochemical Performance of Carbon‐Coated Ti3+ Self‐Doped TiO2‐Reduced Graphene Oxide Hollow Nanostructure‐Supported Pt‐Catalyzed Fuel Cell Electrodes

AbstractStable alternative catalyst supports to replace conventional carbon‐based materials in polymer electrolyte membrane fuel cells (PEMFCs) are being explored to achieve dramatic improvements in the performance and durability of fuel cells. Herein, conductive Ti3+ self‐doped and carbon‐coated TiO2‐reduced graphene oxide (rGO) hollow nanosphere‐supported Pt nanoparticles (Pt/rGO/TiO2) are investigated as cathode electrocatalysts for PEMFCs. Importantly, the rGO/TiO2 hollow nanospheres display excellent electrochemical stability under high potential cycling (1.2–1.7 V) compared with conventional carbon black (CB) support materials that normally induce electrochemical corrosion during fuel cell operation. The Pt/rGO/TiO2 is tested to establish its catalytic activity and stability using accelerated durability testing that mimics the conditions and degradation modes encountered during long‐term fuel cell operation. The Pt/rGO/TiO2 cathode catalyst demonstrates comparable catalytic activity toward oxygen reduction and exhibits much higher stability than the Pt/CB one at high potentials in terms of minimal loss of the Pt electrochemical surface area. More importantly, Pt/rGO/TiO2 displays a negligible voltage drop over long‐term cycling during practical fuel cell operation. The high stability of the Pt/rGO/TiO2 electrocatalyst synthesized in this investigation offers a new approach to improve the reliability and durability of PEMFC cathode catalysts.

Charge Injection in Solution‐Processed Organic Field‐Effect Transistors: Physics, Models and Characterization Methods

A high-mobility organic semiconductor employed as the active material in a field-effect transistor does not guarantee per se that expectations of high performance are fulfilled. This is even truer if a downscaled, short channel is adopted. Only if contacts are able to provide the device with as much charge as it needs, with a negligible voltage drop across them, then high expectations can turn into high performances. It is a fact that this is not always the case in the field of organic electronics. In this review, we aim to offer a comprehensive overview on the subject of current injection in organic thin film transistors: physical principles concerning energy level (mis)alignment at interfaces, models describing charge injection, technologies for interface tuning, and techniques for characterizing devices. Finally, a survey of the most recent accomplishments in the field is given. Principles are described in general, but the technologies and survey emphasis is on solution processed transistors, because it is our opinion that scalable, roll-to-roll printing processing is one, if not the brightest, possible scenario for the future of organic electronics. With the exception of electrolyte-gated organic transistors, where impressively low width normalized resistances were reported (in the range of 10 Ω·cm), to date the lowest values reported for devices where the semiconductor is solution-processed and where the most common architectures are adopted, are ∼10 kΩ·cm for transistors with a field effect mobility in the 0.1-1 cm(2)/Vs range. Although these values represent the best case, they still pose a severe limitation for downscaling the channel lengths below a few micrometers, necessary for increasing the device switching speed. Moreover, techniques to lower contact resistances have been often developed on a case-by-case basis, depending on the materials, architecture and processing techniques. The lack of a standard strategy has hampered the progress of the field for a long time. Only recently, as the understanding of the rather complex physical processes at the metal/semiconductor interfaces has improved, more general approaches, with a validity that extends to several materials, are being proposed and successfully tested in the literature. Only a combined scientific and technological effort, on the one side to fully understand contact phenomena and on the other to completely master the tailoring of interfaces, will enable the development of advanced organic electronics applications and their widespread adoption in low-cost, large-area printed circuits.

Charge Pump Architectures Based on Dynamic Gate Control of the Pass-Transistors

In this paper, we present two charge pump architectures for nonvolatile memories with dynamic biasing of the gate and the body voltages. By controlling the gate and the body voltage of each pass-transistor, the voltage loss due to the device threshold is removed and the charge is pumped from one stage to the following with a negligible voltage drop and large conductivity. The charge pumps were fabricated in the ST 130-nm digital standard CMOS technology. Compared to conventional charge pumps, larger output voltage and better power efficiency are achieved still retaining a simple two-phase clocking scheme. Measurements performed on four-stage and eight-stage charge pumps are provided.

Power efficiency improvement in a tandem organic light-emitting diode

When a tandem light-emitting diode (OLED) utilizes unoptimized electroluminescent (EL) units, it is fairly easy to improve the power efficiency of such a device. However, when a tandem OLED utilizes optimized EL units, improved power efficiency can only be achieved if each intermediate connector has excellent carrier injection capabilities along with a negligible voltage drop across it. Four organic intermediate connectors were studied in this work, one of which consisting of a Li-doped 4,7-diphenyl-1,10-phenanthroline layer and a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile layer, exhibits the best power efficiency improvement for tandem OLEDs.

The Properties of Proportional Tubes and Ion Chambers with Glass Envelopes and External Graphite Electrodes

Proportional tubes and ion chambers are described, the cathodes of which consist of graphite coatings on the external surfaces of the glass envelopes. Currents in the range 10-12 to 10-11 A. pass through the walls of soft glass envelopes with negligible voltage drop. The potential of the inner surface of a hard glass chamber gradually changes due to the accumulation of surface charge. The change of potential is readily tolerated, however, in experiments of normal duration.