Wide Operating Temperature Research Articles

Machine-learning-assisted material discovery of oxygen-rich highly porous carbon active materials for aqueous supercapacitors

Porous carbons are the active materials of choice for supercapacitor applications because of their power capability, long-term cycle stability, and wide operating temperatures. However, the development of carbon active materials with improved physicochemical and electrochemical properties is generally carried out via time-consuming and cost-ineffective experimental processes. In this regard, machine-learning technology provides a data-driven approach to examine previously reported research works to find the critical features for developing ideal carbon materials for supercapacitors. Here, we report the design of a machine-learning-derived activation strategy that uses sodium amide and cross-linked polymer precursors to synthesize highly porous carbons (i.e., with specific surface areas > 4000 m2/g). Tuning the pore size and oxygen content of the carbonaceous materials, we report a highly porous carbon-base electrode with 0.7 mg/cm2 of electrode mass loading that exhibits a high specific capacitance of 610 F/g in 1 M H2SO4. This result approaches the specific capacitance of a porous carbon electrode predicted by the machine learning approach. We also investigate the charge storage mechanism and electrolyte transport properties via step potential electrochemical spectroscopy and quasielastic neutron scattering measurements.

Non-flammable solvent-free liquid polymer electrolyte for lithium metal batteries

As a replacement for highly flammable and volatile organic liquid electrolyte, solid polymer electrolyte shows attractive practical prospect in high-energy lithium metal batteries. However, unsatisfied interface performance and ionic conductivities are two critical challenges. A common strategy involves introducing organic solvents or plasticizers, but this violates the original intention of security design. Here, an electrolyte concept called liquid polymer electrolyte without any small molecular solvents is proposed for safe and high-performance batteries, based on the design of a room-temperature liquid-state brush-like polymer as the sole solvent of lithium salts. This liquid polymer electrolyte is non-flammable and exhibits high ionic conductivity (1.09 times 10−4 S cm−1 at 25 °C), significant lithium dendrite suppression, and stable long-term cycling over a wide operating temperature range ( ≥ 1000 cycles at 60 °C and 90 °C). Moreover, the pouch cell can resist thermal abuse, vacuum environment, and mechanical abuse. This electrolyte and design strategy are expected to provide enlightening ideas for the development of safe and high-performance polymer electrolytes.

Influence of mechanical stress on electron transport properties of second-generation high-temperature superconducting tapes

Second-generation high-temperature superconductor (2G HTS) tapes have demonstrated the ability to generate high magnetic fields and critical currents at a wide operating temperature range. In this paper, we study the mechanical properties of 2G HTS tape measured simultaneously with its critical current. The lattice deformations in the tape’s substrate caused by applied mechanical stress were measured by neutron diffraction. In our experiments, the 2G HTS tape was exposed to uniaxial tensile force ranging from 250 to 1100 N at temperature 77 K. The current through the tape was scanned in the range from 22 to 42 A. The experimental results have been obtained in a cryogenic testing chamber for neutron scattering measurements of internal stresses under load with the incorporated HTS current leads. Critical stress is a vital parameter required for the modeling and designing of advanced superconducting magnets and also a variety of different superconducting applications based on 2G HTS tapes.

Construction of high-rate performance sulfurized Poly(acrylonitrile) nanofibers cathodes for practical lithium–sulfur batteries via tellurium catalytic regulation

The rapid charge-discharge and wide operating temperature range are of great significance to the research of lithium-sulfur batteries. However, the poor electronic and ionic conductivity of sulfurized polyacrylonitrile limits the high-rate and low-temperature performance of lithium-sulfur batteries. In this work, a tellurium-doped sulfurized polyacrylonitrile nanofibers-based cathode material (Te0.02S0.98FPAN) is successfully fabricated by air-blow spinning for lithium-sulfur batteries. It is found that Te0.02S0.98FPAN maintained a high reversible specific capacity of 742 mAh·g−1composites after 200 cycles at a current density of 0.2 C (0.014% decay per cycle), whereas it provides a reversible specific capacity of 641 mAh·g−1composites after 500 cycles even at a large current density of 1.0 C (0.021% decay per cycle), manifesting its excellent high-rate performance. Moreover, Te0.02S0.98FPAN still maintained a high reversible specific discharge capacity of 586 mAh·g−1composites after 100 cycles at 0.2 C at a low temperature of 5.0 °C, confirming its wide operating temperature range. Both the eutectic accelerator (tellurium) and the one-dimensional nanofibrous structure greatly improve the migration rate and electron transport ability of Li+ ions, enhancing reaction kinetics and providing fast and stable migration channels for ions and electrons. Therefore, Te0.02S0.98FPAN has a higher oxidation-reduction reaction rate and less polarization. This study not only provides new ideas for the cathode design of lithium-sulfur batteries with high rate and wide temperature range, but also paves the way for the development of practical lithium-sulfur batteries. In particular, when tested in practical conditions of high areal loading (Te0.02S0.98: 5.0 mg cm−2) and lean electrolyte (E/Te0.02S0.98: 10 μL mg−1), this cathode delivers high reversible capacities of 725 mAh g−1 composite (0.1 C) and 663 mAh g−1 composite (0.2 C), demonstrating its great potential for future application.

Elaborating the improving SO2 resistance mechanism of CeWTi catalysts through framework confined ordered mesoporous structures for low-temperature NH3-SCR reaction

It is still a significant challenge that enhancing SO2 tolerance on the Ce-based catalyst in NH3-SCR reaction at low temperature. In this paper, an ordered mesoporous Ce-W-Ti-E catalyst with a framework confined structure had been constructed. The active components were directly constrained in the ordered mesoporous TiO2 structure, forming the framework confined ordered mesoporous structure. The ordered mesoporous structures in the framework structure provided better specific surface area and abundant active sites for the catalyst. In addition, the confinement effect of the framework structure enhanced the interaction between Ce, W and Ti, thus speeding up the electron transfer efficiency and enhancing the redox capacity of the catalyst. Furthermore, the introduction of W also supplemented a large amount of surface acid sites, which can inhibit the adsorption of SO2 on the catalyst surface, reduce the deposition of sulfate and well protect the active sites from SO2 attack with the help of special confinement effect. Therefore, the framework confined structure Ce-W-Ti-E catalyst in the whole process of SCR showed a wide operating temperature window, better stability and strong sulfur resistance, thus extended the catalyst lifetime in the NH3-SCR process.

A High-Sensitivity Cesium Atomic Magnetometer Based on A Cesium Spectral Lamp

Based on a low-noise cesium spectral lamp, a high-sensitivity self-oscillating cesium atomic magnetometer with a wide operating temperature range has been developed, solving problems with existing sensors such as a limited operating temperature range and difficult startup at low temperatures. The temperature feedback mechanism is used to make adjustments to any fluctuations in the cesium lamp’s excitation source in real time, improving the magnetometer’s stability and operating temperature range. Herein, the design and optimization of the cesium atomic magnetometer are presented, and a prototype of the magnetometer is described. The quantum limit sensitivity of the cesium atomic magnetometer is estimated by evaluating the intrinsic relaxation rate in the geomagnetic field. A test demonstrates that the cesium atomic magnetometer’s sensitivity in the geomagnetic background is around 140 fT/Hz at 1 Hz at room temperature, and the operating temperature range is from −50 °C to 70 °C, surpassing most of the commercial products of its kind in terms of sensitivity and operating temperature range.

Thermochemical processes for CO[formula omitted] hydrogenation to fuels and chemicals: Challenges and opportunities

This manuscript discusses the potential use of CO2 as a carbon and oxygen carrier to return it to the carbon life cycle in the form of fuels or chemicals via thermochemical catalytic pathways. Theoretically, CO2 hydrogenation can form a variety of fuels and chemicals. Practically, however, the selectivity, conversion, operating range, and kinetic limitations and operational cost determine the end product. Because of their high value and versatility as a chemical or fuel, small olefins (i.e., C2H4) and methanol are often considered as target species. Whether alcohol or olefin formation, CH4 and CO are the nature’s primary choices of CO2 conversion. They can be formed over a wide operating temperature, pressure, and CO2:H2 ratios. They are often competitive carbon species in olefin or methanol formation steps. Although they are less valuable as end products, they can be used as intermediate species. Secondary processes of CO and CH4 to form chemicals and fuels can increase the overall CO2 hydrogenation yield. Independent of the choice of end product, CO2 hydrogenation requires hydrogen. Pure hydrogen derived mostly from fossil fuels adds to the overall process cost and also increases the CO2 emissions. Hydrogen produced from water electrolysis is a renewable green pathway but is limited by the process efficiency and cost. As an alternative to pure hydrogen, low-value, small chain paraffins are suggested as the hydrogen carriers. Carbon dioxide–assisted oxidative dehydrogenation of paraffins to olefins process is a direct pathway to olefin formation. The paper discusses these potential pathways for CO2 utilization based on theoretical analysis and recent advances in academia and industry.

“Deep Eutectic Solvent-in-Water” Hydrogels Enable High-Performance Flexible Strain Sensors for Electronic Skin with a Wide Operating Temperature Range

“Deep Eutectic Solvent-in-Water” Hydrogels Enable High-Performance Flexible Strain Sensors for Electronic Skin with a Wide Operating Temperature Range

Highly stretchable, conductive, and wide-operating temperature ionogel based wearable triboelectric nanogenerator

Highly stretchable, conductive, and wide-operating temperature ionogel based wearable triboelectric nanogenerator

Design and construction of low resistance copper doped polyaniline electrode with ultrahigh loading density for high performance supercapacitor applications

Polyaniline is a promising material for the development of high performance flexible supercapacitor devices. However, the loose structure of polyaniline materials and the high intermolecular transport impedance between molecular chains remain significant technical barriers, particularly at high loading density. In this study, we developed a copper ion doped polyaniline electrode (Cu-PANI@CC) on carbon cloth using a simple one-step in-situ electrochemical deposition method. The structure and electrochemical properties of this electrode were investigated via different testing techniques. Benefiting from the catalysis and regulation of copper ions between PANI molecular chains, the electrode demonstrated a relatively low internal resistance at high loading densities (> 10 mg cm−2). Moreover, this electrode exhibited specific capacitance of 3.49 F cm−2 at 5 mA cm−2 and capacitance retention of 83.31% at 50 mA cm−2. Two Cu-PANI@CC electrodes were used to fabricate a symmetrical capacitor, which exhibited remarkable cycling stability and wide operating temperature range. The excellent electrochemical performance of the Cu-PANI@CC electrode highlights the potential for use in high-performance supercapacitor devices.

Improvement of Hybrid Electrode Material Synthesis for Energy Accumulators Based on Carbon Nanotubes and Porous Structures.

Carbon materials are promising for use as electrodes for supercapacitors and lithium-ion batteries due to a number of properties, such as non-toxicity, high specific surface area, good electronic conductivity, chemical inertness, and a wide operating temperature range. Carbon-based electrodes, with their characteristic high specific power and good cyclic stability, can be used for a new generation of consumer electronics, biomedical devices and hybrid electric vehicles. However, most carbon materials, due to their low electrical conductivity and insufficient diffusion of electrolyte ions in complex micropores, have energy density limitations in these devices due to insufficient number of pores for electrolyte diffusion. This work focuses on the optimization of a hybrid material based on porous carbon and carbon nanotubes by mechanical mixing. The purpose of this work is to gain new knowledge about the effect of hybrid material composition on its specific capacitance. The material for the study is taken on the basis of porous carbon and carbon nanotubes. Electrodes made of this hybrid material were taken as an object of research. Porous carbon or nitrogen-containing porous carbon (combined with single-, double-, or multi-layer carbon nanotubes (single-layer carbon nanotubes, bilayer carbon nanotubes or multilayer carbon nanotubes) were used to create the hybrid material. The effect of catalytic chemical vapor deposition synthesis parameters, such as flow rate and methane-to-hydrogen ratio, as well as the type of catalytic system on the multilayer carbon nanotubes structure was investigated. Two types of catalysts based on Mo12O28 (μ2-OH)12{Co(H2O)3}4 were prepared for the synthesis of multilayer carbon nanotubes by precipitation and combustion. The resulting carbon materials were tested as electrodes for supercapacitors and lithium ion intercalation. Electrodes based on nitrogen-containing porous carbon/carbon nanotubes 95:5% were found to be the most efficient compared to nitrogen-doped porous carbon by 10%. Carbon nanotubes, bilayer carbon nanotubes and multilayer carbon nanotubes synthesized using the catalyst obtained by deposition were selected as additives for the hybrid material. The hybrid materials were obtained by mechanical mixing and dispersion in an aqueous solution followed by lyophilization to remove water. When optimizing the ratio of the hybrid material components, the most effective porous carbon:carbon nanotubes component ratio was determined.

Mo-doped MnO2@CC electrode for high-performance 2.4 V aqueous asymmetric supercapacitors

Despite many advantages of supercapacitors based on aqueous electrolytes, the inherently low operating voltage severely limits their energy density and practical applicability to many applications. Thus, it is a key scientific challenge to broaden the potential window of electrode materials for supercapacitors. Here we report our findings in tailoring the Fermi level of MnO2-based electrode by doping with a high-valence Mo6+ ion, thus modulating its overpotential in aqueous electrolytes and potential window. For example, the redox potential of Mo-doped MnO2 is effectively increased, resulting in a wider potential window. When grown on a carbon support, the specific capacitance of Mo-doped MnO2@CC with a mass loading of 15.1 mg cm−2 reaches 3.22 F cm−2 in a wide potential window of 1.2 V. The enhanced performance is attributed to the additional redox behavior induced by the Mo dopant, as confirmed by in situ Raman and ex-situ XPS analyses. When coupled with a C-Ti3C2Tx/WO3@CC negative electrode to construct an ASC with a total mass loading of 35.8 mg cm−2, the ASC exhibits a wide voltage window of 2.4 V, demonstrating a remarkable energy density of 0.89 mWh cm−2 at a power density of 2.56 mW cm−2. In addition, the device is operational in a wide operating temperature range of −10 to 50 °C, and a voltage of ∼ 58% is retained after self-discharge for 48 h. This work provides some new insights into the development of aqueous ASC devices of commercial-grade mass loadings with high output voltage, high energy density, and slow self-discharge rates.

Wide-Temperature Operation of Lithium-Sulfur Batteries Enabled by Multi-Branched Vanadium Nitride Electrocatalyst.

High-performance lithium-sulfur (Li-S) batteries that can work normally under harsh conditions have attracted tremendous attention; however, the sluggish reaction kinetics of polysulfide conversions at low temperatures as well as the notorious polysulfide shuttling at high temperatures remain to be resolved. Herein, a multibranched vanadium nitride (MB-VN) electrocatalyst has been designed and deployed for Li-S batteries. Both experimental (time-of-flight secondary ion mass spectroscopy and adsorption tests) and theoretical results verify the strong chemical adsorption capability and high electrocatalytic activity of MB-VN with respect to polysulfides. Moreover, in situ Raman characterization manifests the effective inhibition of polysulfide shuttling by the MB-VN electrocatalyst. Using MB-VN-modified separators, the Li-S batteries deliver an excellent rate capability (707 mAh g-1 at 3.0 C) and great cyclic stability (678 mAh g-1 after 400 cycles at 1.0 C) at room temperature. With 6.0 mg cm-2 of sulfur and a lean electrolyte volume of ∼6 μL mgs-1, Li-S batteries exhibit a high areal capacity of 5.47 mAh cm-2. Even over a wide temperature range (-20 to +60 °C), the Li-S batteries still maintain stable cyclic performance at high current rates. This work demonstrates that metal nitride based electrocatalysts can realize low-/high-temperature-tolerant Li-S batteries.

The study on the preparation of ultra-low thermal expansion ceramic with high elastic modulus

The paper studied the synthesis of cordierite powders and the preparation of ultra-low thermal expansion ceramic with high elastic modulus. The powder was synthesized by solid state reaction using MgO, Al2O3 and SiO2 as raw materials. The effect of temperature on powder purity, phase and properties of ceramic was mainly studied. The results show that the cordierite powder with higher purity and reactivity was synthesized at 1390°C, containing two kinds of phase (α-cordierite and β-cordierite). The compact cordierite ceramic could be obtained at 1420°C with homogeneous and compact organizations, besides, this sample had a wide operating temperature area with low thermal expansion, and the higher elastic modulus.

High Sensitivity Low-Temperature Hydrogen Sensors Based on SnO2/κ(ε)-Ga2O3:Sn Heterostructure

The structural and gas-sensitive properties of n-N SnO2/κ(ε)-Ga2O3:Sn heterostructures were investigated in detail for the first time. The κ(ε)-Ga2O3:Sn and SnO2 films were grown by the halide vapor phase epitaxy and the high-frequency magnetron sputtering, respectively. The gas sensor response and speed of operation of the structures under H2 exposure exceeded the corresponding values of single κ(ε)-Ga2O3:Sn and SnO2 films within the temperature range of 25–175 °C. Meanwhile, the investigated heterostructures demonstrated a low response to CO, NH3, and CH4 gases and a high response to NO2, even at low concentrations of 100 ppm. The current responses of the SnO2/κ(ε)-Ga2O3:Sn structure to 104 ppm of H2 and 100 ppm of NO2 were 30–47 arb. un. and 3.7 arb. un., correspondingly, at a temperature of 125 °C. The increase in the sensitivity of heterostructures at low temperatures is explained by a rise of the electron concentration and a change of a microrelief of the SnO2 film surface when depositing on κ(ε)-Ga2O3:Sn. The SnO2/κ(ε)-Ga2O3:Sn heterostructures, having high gas sensitivity over a wide operating temperature range, can find application in various fields.

Superior zero thermal expansion dual-phase alloy via boron-migration mediated solid-state reaction

Rapid progress in modern technologies demands zero thermal expansion (ZTE) materials with multi-property profiles to withstand harsh service conditions. Thus far, the majority of documented ZTE materials have shortcomings in different aspects that limit their practical utilization. Here, we report on a superior isotropic ZTE alloy with collective properties regarding wide operating temperature windows, high strength-stiffness, and cyclic thermal stability. A boron-migration-mediated solid-state reaction (BMSR) constructs a salient “plum pudding” structure in a dual-phase Er-Fe-B alloy, where the precursor ErFe10 phase reacts with the migrated boron and transforms into the target Er2Fe14B (pudding) and α-Fe phases (plum). The formation of such microstructure helps to eliminate apparent crystallographic texture, tailor and form isotropic ZTE, and simultaneously enhance the strength and toughness of the alloy. These findings suggest a promising design paradigm for comprehensive performance ZTE alloys.

Li3BO3-Li3PO4 Composites for Efficient Buffer Layer of Sulphide-Based All-Solid-State Batteries

All-solid-state batteries (ASSBs) based on sulphide electrolytes are promising next-generation energy storage systems because they are expected to have improved safety, increased volumetric energy density, and a wide operating temperature range. However, side reactions at the cathode/electrolyte interface deteriorate the electrochemical performance and limit the commercialization of ASSBs. Surface coating of the cathode is an efficient approach for overcoming this issue. In this study, new Li3BO3 (LBO)-Li3PO4 (LPO) composites were applied as coating materials for high-Ni cathodes (NCM). PO4-based materials (such as LPO) have been used as coating layers because of their good chemical stability in sulphide electrolytes. However, the ionic conductivity of LPO is slightly insufficient compared to those of generally used ternary oxides. The addition of LBO could compensate for the low ionic conductivity of LPO and may provide better protection against sulphide electrolytes owing to the effect of LBO, which has been used as a good coating material. As expected, the LBO-LPO composites (LBPO) NCM exhibited superior discharge capacity, rate capability, and cyclic performance compared to the pristine and LPO-coated NCMs. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) analyses confirmed that the LBPO coating on the cathodes successfully suppressed the byproduct formation and an undesirable interfacial layer, which are attributed to interfacial side reactions. This result clearly shows the potential of the LBPO coating as an excellent buffer layer to stabilise the oxide cathode/sulphide electrolyte interface.

A flexible, high-energy density, and temperature-tolerant asymmetric supercapacitor based on water-in-salt gel electrolyte

The dramatic development of wearable electronics has led to extensive research into flexible supercapacitors as wearable energy storage devices. The practical application of supercapacitors to wearable electronics requires improved temperature tolerance and high energy density. Herein, we report the fabrication of a high-voltage flexible aqueous supercapacitor featuring high energy density and a wide operating temperature range. This is achieved by the strategy of simultaneously utilizing asymmetric electrodes and water-in-salt gel electrolyte (WISGE). Using NaClO4-based WISGE and asymmetric electrodes consisting of Na-inserted MnO2 and N-doped carbon nanofibers, we obtain excellent electrochemical performance, including a gravimetric capacitance of 97.2 F g−1, energy density of 90 Wh kg−1, power density of 28.1 kW kg−1, operation voltage window of 2.6 V, and capacitance retention of 85.2% over 10,000 charge/discharge cycles. The fabricated flexible supercapacitor is stable under repeated temperature changes between − 20 and 80 °C, regardless of bending deformation. After three cycles of cooling and heating, the initial capacitance at room temperature is 95.1% recovered. This study demonstrates the potential application of our high-performance flexible aqueous supercapacitors to wearable devices, given their resistance to changes in environmental temperature and mechanical deformation.

Promotion Effect of Iron on Activity and N2 Selectivity of Mn/Ce Catalysts in the NH3-SCR Reaction

Manganese oxides are known to have good low-temperature SCR performance, whereas improving their medium- and high-temperature catalytic performance and N2 selectivity remain a challenge. Herein, manganese-based ternary catalysts Fe–Mn/Ce, using CeO2 as the carrier and Fe as the second active component, were constructed to effectively solve this problem. Fe–Mn/Ce catalysts show excellent catalytic performance, with NOx conversions of more than 90% over a wide operating temperature range (164.5–419.4 °C) with high and N2 selectivity. Further investigation showed that, for the Fe–Mn/Ce catalyst with rich redox sites and surface acidity, higher amounts of Fe2+ and Mn4+ are the important factors promoting excellent SCR reactivity. Besides, the Fe modification can generate effective electron transfer to reduce the N2O generation pathway and increase the catalytic reaction sites, thus enhancing the overall catalytic performance.

Interphase stabilized electrospun SnO2 fibers as alloy anode via restricted cycling for Li-ion capacitors with high energy and wide temperature operation

The second-generation supercapacitor comprises the hybridized energy storage mechanism of Lithium-ion batteries and electrical double-layer capacitors, i.e, Lithium-ion capacitors (LICs). The electrospun SnO2 nanofibers are synthesized by a simple electrospinning technique and are directly used as anode material for LICs with activated carbon (AC) as a cathode. However, before the assembly, the battery-type electrode SnO2 is electrochemically pre-lithiated (LixSn + Li2O), and AC loading is balanced with respect to its half-cell performance. First, the SnO2 is tested in the half-cell assembly with a limited potential window of 0.005 to 1 V vs. Li to avoid the conversion reaction of Sn0 to SnOx. Also, the limited potential window allows only the reversible alloy/de-alloying process. Finally, the assembled LIC, AC/(LixSn + Li2O), displayed a maximum energy density of 185.88 Wh kg−1 with ultra-long cyclic durability of over 20,000 cycles. Further, the LIC is also exposed to various temperature conditions (–10, 0, 25, & 50 °C) to study the feasibility of using them in different environmental conditions.