Boosting energy-storage capability in carbon-based supercapacitors using low-temperature water-in-salt electrolytes

Supercapacitors(SCs) are high-power energy storage devices with ultra-fast charge/discharge properties.SCs using concentrated aqueous-based electrolytes can work at low temperatures due to their intrinsic properties, such as higher freezing point depression(FPD) and robustness. Besides the traditional organic-and aqueous-based(salt-in-water) electrolytes used in SCs, water-in-salt(WISE) sodium perchlorate electrolytes offer high FPD, non-flammability, and low-toxicity conditions, allowing the fabrication of safer, environmentally friendly, and more robust devices. For the first time, this work reports a comprehensive study regarding WISE system’s charge-storage capabilities and physicochemical properties under low-temperature conditions(T < 0 ℃) using mesoporous carbon-based electrodes. The effect of temperature reduction on the electrolyte viscosity and electrical properties was investigated using different techniques and the in-situ(or operando) Raman spectroscopy under dynamic polarization conditions.The cell voltage, equivalent series resistance, and specific capacitance were investigated as a function of the temperature. The cell voltage(U) increased ~ 50%, while the specific capacitance decreased ~20%when the temperature was reduced from 25 ℃ to -10 ℃. As a result, the maximum specific energy(E = CU^(2)/2) increased ~ 100%. Therefore, low-temperature WISEs are promising candidates to improve the energy-storage characteristics in SCs.

Free radicals, apparent activation energy, and functional groups during low-temperature oxidation of Jurassic coal in Northern Shaanxi

Correlations among free radicals, apparent activation energy, and functional groups during lowtemperature oxidation of Jurassic coal in Northern Shaanxi were investigated by examining three coal samples collected from the Ningtiaota, Jianxin, and Shigetai coal mines. Free radical concentrations at less than 120 ℃ were investigated by electron spin resonance experiments while the thermogravimetric experiments were conducted to analyze apparent activation energies. In addition, Fourier transform infrared spectroscopy was employed to study the spectrum of functional groups generated in coal. The results indicated that, in decreasing order, the apparent activation energies were Shigetai 〉Jianxin 〉 Ningtiaota, indicating that, from 50 to 120 ℃, the Ningtiaota coal sample most easily absorbed and reacted with oxygen while the most resistant was the Shigetai coal sample. Free radical concentrations and line heights increased with increased temperature, and the line width and Lande factor showed irregular fluctuations. Functional group variations were different among these coals, and the phenol and alcohol-associated OHs, carboxyls, and aromatic ring double bonds might have had a major impact on free radical concentrations. These results were meaningful for better consideration and management of coal oxidation at low temperatures.

Study on the energy evolution mechanism of low-temperature concrete under uniaxial compression

In order to study the mechanical properties and energy evolution of low-temperature concrete during uniaxial compres‐sion, a uniaxial compression test was performed on concrete. In addition, the evolution laws of compressive strength, deformation modulus and total energy, elastic potential energy, dissipated energy and peak energy of concrete in the process of deformation and failure are analyzed. The effects of age and temperature on low-temperature concrete is analyzed from the perspective of energy. Test results show that temperature improves the strength and deformation of concrete to varying degrees. When cured for 28 days, the compressive strength and deformation modulus of concrete at −20 ℃ is increased by 17.98% and 21.45% respectively, compared with the compressive strength and deformation modulus at room temperature of 20 ℃. At the point of failure of the concrete under uniaxial compression, the total damage energy and the dissipation energy both increase, while the developed elastic strain energy increases and then decreases. Increase in curing duration tends to increase the total destruction energy of concrete, peak point elastic strain energy, peak point dissipation energy, and peak point total energy. Whereas increase in curing durations, has shown to decrease the total destruction energy of concrete, the peak point elastic strain energy, peak point dissipation energy, and peak point total energy. The peak point strain energy reflects the ability of low-temperature concrete to reasonably resist damage. By using the principle of energy analysis to study the deformation process of concrete, it provides research methods and ideas for the deformation analysis of this type of material under load.

A systematic approach for synthesizing a low-temperature distillation system

In this paper, by combining a stochastic optimization method with a refrigeration shaft work targeting method,an approach for the synthesis of a heat integrated complex distillation system in a low-temperature process is presented. The synthesis problem is formulated as a mixed-integer nonlinear programming(MINLP) problem,which is solved by simulated annealing algorithm under a random procedure to explore the optimal operating parameters and the distillation sequence structure. The shaft work targeting method is used to evaluate the minimum energy cost of the corresponding separation system during the optimization without any need for a detailed design for the heat exchanger network(HEN) and the refrigeration system(RS). The method presented in the paper can dramatically reduce the scale and complexity of the problem. A case study of ethylene cold-end separation is used to illustrate the application of the approach. Compared with the original industrial scheme, the result is encouraging.

Utilization and recycling of low-temperature waste heat of stainless steel continuous annealing furnace

Stainless steel continuous annealing furnace is mainly used for heat treatment of hot-rolled strip steel.The combustion air will be enabled to heat to 520℃by waste heat recovery system,but the discharge temperature is still up to about 300℃.Owing to with development of global emphasis on energy conservation energy saving and discharge reduction,it's significant to lower the discharge temperature to below 200℃, for the sake of achieving rational use of waste heat resource.Through the analysis of the existing heat recovery system by this study,it is proved that mixing low temperature with flue gas in high temperature standard will increase the capacity of the flue gas and deteriorate the quality of remaining heat resource.In stead of that,increasing the combustion air temperature to 600℃on the basis of stability temperature for the prerequisite of recuperator design,and giving priority to reducing fuel consumption are the better way.The recovery and recycle of low temperature gas are also be introduced.It is demonstrated by the way of setting a secondary recuperator at the exit of the primary recuperator,and using low temperature flue gas to heat the air used for drying the strip steel,the exhuast temperature of flue gas can be reduced to lower than 200℃.At the same time,the steam required for heating air is saved,the energy reserve as high as 2 300 t of standard coal per year.

Fundamental study of novel mid-and low-temperature solar thermochemical energy conversion

A new approach to application of mid-and low-temperature solar thermochemical technology was in-troduced and investigated.Concentrated solar thermal energy in the range of 150―300℃ can be effi-ciently converted into high-grade solar fuel by integrating this technique with the endothermic reaction of hydrocarbons.The conversion mechanism of upgrading the low-grade solar thermal energy to high-grade chemical energy was examined based on the energy level.The new mechanism was used to integrate two novel solar thermal power systems:A solar/methanol fuel hybrid thermal power plant and a solar-hybrid combined cycle with inherent CO2 separation using chemical-looping combustion,for developing highly efficient solar energy use to generate electricity.An innovative prototype of a 5-kW solar receiver/reactor,as the key process for realizing the proposed system,was designed and manu-factured.Furthermore,experimental validation of energy conversion of the mid-and low-temperature solar thermochemical processes were conducted.In addition,a second practical and viable approach to the production of hydrogen,in combination with the novel mid-and low-temperature solar thermo-chemical process,was proposed and demonstrated experimentally in the manufactured solar re-ceiver/reactor prototype through methanol steam reforming.The results obtained here indicate that the development of mid-and low-temperature solar thermochemical technology may provide a promising and new direction to efficient utilization of low-grade solar thermal energy,and may enable step-wise approaches to cost-effective,globally scalable solar energy systems.

Enhanced piezoelectric properties in low-temperature sintered Pb(Zr,Ti)O_(3)-based ceramics via Yb_(2)O_(3) doping

Pb(Mg_(0.5)W_(0.5))O_(3)–Pb(Ni_(1/3)Nb_(2/3))O_(3)–Pb(Zr_(0.5)Ti_(0.5))O_(3)(PNN–PMW–PZT)piezoceramics were sintered at a low temperature of 900℃by the mixed metal oxide powder solid-state reaction route.CaCO_(3) and Li_(2)CO_(3) as sintering aids and Yb_(2)O_(3) as a dopant were added into the PNN–PMW–PZT ceramic system for low-temperature sintering and enhancement of electrical properties,respectively.The effects of different Yb_(2)O_(3) doping amounts on the microstructure,dielectric,piezoelectric and ferroelectric properties of the samples were systematically investigated.The piezoceramics doped with 0.1 mol%Yb_(2)O_(3) have optimal electrical properties(d_(33)=563 pC/N,k_(p)=0.66,ε_(r)=2728(1 kHz),tanδ=0.0176(1 kHz),and T_(C)=301℃).While the piezoceramics doped with 0.3 mol% Yb_(2)O_(3) have optimal energy conversion properties:the piezoelectric voltage coefficient g_(33)=26.7×10^(-3)Vm/N and the effective piezoelectric energy conversion coefficient d_(33)×g_(33)=14366×10^(-15)m^(2)/N.

Multiscale Study on Low Temperature Crack Resistance Mechanism of Steel Slag Asphalt Mixture

The objective of this paper was to study low temperature crack resistance mechanism of steel slag asphalt mixture(SAM).Thermal stress restrained specimen test(TSRST)and three-point bending test were carried out to evaluate the low-temperature crack resistance of SAM and basalt asphalt mixture(BAM).Based on the digital image correlation technique(DIC),the strain field distribution and crack propagation of SAM were analyzed from the microscopic point of view,and a new index,crack length factor(C),was proposed to evaluate the crack resistance of the asphalt mixture.The crystal phase composition and microstructure of steel slag aggregate(SA)and basalt aggregate(BA)were studied by X-ray diffraction(XRD)and scanning electron microscopy(SEM)to explore the low-temperature crack resistance mechanism of SAM.Results show that the low-temperature crack resistance of SAM is better than that of BAM;SAM has good integrity and persistent elastic deformation,and its bending failure mode is a hysteretic quasi-brittle failure;The SA surface is evenly distributed with pores and has surface roughness.SA has the composition phase of alkaline aggregate-calcite(CaCO3),so it has good adhesion to asphalt,which reveals the mechanism of excellent low-temperature crack resistance of SAM.

A New Method for Predicting Wall Sticking Occurrence Temperature of High Water Cut Crude Oil

In crude oil transportation, adhesion of oil on pipe wall can cause partial or total blockage of the pipe. This process is significantly affected by wall sticking occurrence temperature(WSOT). In this work, an efficient approach for estimating WSOT of high water-cut oil, which can agree well with the actual environment of multiphase transportation pipeline, is proposed. Based on the energy dissipation theory, it is possible to make comparison of average shear rates between the stirred vessel and the flow loop. The impacts of water content and shear rate on WSOT are investigated using the stirred vessel and the flow loop. Good agreement has been observed between the stirred vessel and the flow loop results with the maximum and the average absolute deviations equating to 3.30 °C and 2.18 °C, respectively. The development of gathering scheme can enjoy some benefits from this method.

Low-Temperature Working Feasibility of Zinc–Air Batteries with Noble Metal-Free Electrocatalysts

Expanding the application scenario for rechargeable batteries is the key to the terminal utilization of renewable energy.Enabling zinc–air batteries at low temperatures is drawing increasing attention,yet the low-temperature working feasibility of zinc–air batteries with noble metalfree electrocatalysts remains indistinct.In this contribution,the low-temperature performances of zinc–air batteries with noble metal-free electrocatalysts are comprehensively investigated.Armed with a representative noble metal-free bifunctional oxygen electrocatalyst,the zinc–air batteries demonstrate satisfactory yet relatively depressed performance at low temperatures,compared with that at room temperatures.The reduced electrolyte conductivity is identified as one of the limiting factors for the reduced low-temperature performance.Furthermore,electrolyte engineering via solvation structure regulation is performed on the zinc–air batteries with noblemetal-free electrocatalysts,where an improved low-temperature performance is achieved.This work reveals the compatibility between noble metal-free electrocatalysts and low-temperature feasibility/low-temperature performance enhancement strategies for zinc–air batteries and affords new opportunities to satisfy low-cost and efficient energy storage at harsh working conditions.

Effect of Magnetic Field on Synthesis of Nano-FeOOH by Low-Temperature Neutralization Method

Using XRD,TEM and VSM methods,the phase,morphology and magnetic property of iron hydroxide oxide(FeOOH) which has been prepared by low-temperature neutralization reaction under different magnetic fields were analyzed.It can be found that the magnetic field had a great influence on the product.Acicular goethite(α-FeOOH) was synthetized without magnetic field.When the magnetic flux density was increased to 0.1T,γ-FeOOH was obtained.If the magnetic field intensity was raised to 0.5T,the product was all composed of δ-FeOOH.Moreover,the crystallization of FeOOH was greatly influenced by magnetic field as well.Thermodynamic calculation results show that the magnetic free energy of chemical reaction reached to more than hundreds KJ/mol when the magnetic field is applied.It meaned that the application of magnetic field was conducived to producing the products with higher susceptibility.Even under the low magnetic field,due to the stability of the reaction products was broken by the magnetic field,the magnetic free energy was also effective.

Incorporation of Ag into Cu(In,Ga)Se_(2) films in low-temperature process

Chalcopyrite Cu(In,Ga)Se_(2)(CIGS) thin films deposited in a low-temperature process(450℃) usually produce fine grains and poor crystallinity. Herein, different Ag treatment processes, which can decrease the melting temperature and enlarge band gap of the CIGS films, were employed to enhance the quality of thin films in a low-temperature deposition process. It is demonstrated that both the Ag precursor and Ag surface treatment process can heighten the crystallinity of CIGS films and the device efficiency. The former is more obvious than the latter. Furthermore, the Urbach energy is also reduced with Ag doping. This work aims to provide a feasible Ag-doping process for the high-quality CIGS films in a low-temperature process.

Numerical and Experimental Studies of Working Processesin a Cryogenic Fuelling Tank Coupled with Energy Plant

This article presents a device for the storage and gasification of cryogenic working fluid,which is named a cryogenic fuelling tank.A cryogenic fuel tank can serve both as a fuel vessel and a pressure accumulator due to the regasification process that takes place inside.Application of this tank is slowed by the lack of theoretical and experimental research on its working process.This article deals with an investigation of the working process of the energy plant based on a cryogenic fuel tank coupled with a rotor-vane expander.Developed mathematical models include evaporation and condensation processes within the tank,heat exchange between gas chambers and between the tank and environment,and changes in energy due to incoming and leaving mass.Mechanical work used to determine the efficiency of a power plant is generated by a steam expander.Research shows that it is possible to achieve specific work outputs up to 110-160 kJ/kg with relative deviation of power and specific work determination equal to 1.4% and 1.9%correspondingly.

INFLUENCE OF CaF_(2)-4LiF ADDITIVE ON SINTERING AND ENERGY STORAGE PERFORMANCE OF SrTiO_(3)CERAMICS

The CaF_(2)-4LiF additive was added into SrTiO_(3)ceramics in order to decrease the sintering temperature for compact pulse power application.The crystalline structure,microstructure and energy storage performance of sintered ceramics were studied.Incorporating CaF_(2)-4LiF additive to SrTiO_(3)ceramics contributes to a notably enhancement of the energy storage density.The great enhancement in energy storage density occurred due to the notable increase in breakdown strength and the refinement of microstructure.With 2 at%additive,the samples exhibited an average breakdown strength of 31.8kV/mm,and an energy storage density of 1.212 J/cm^(3)which is about 1.4 times higher than pure SrTiO_(3).