Gel-state polybenzimidazole proton exchange membranes with flexible alkyl sulfonic acid side chains for a wider operating temperature range(25–240 ℃)

High-temperature proton exchange membrane fuel cells(HT-PEMFC) possess distinct technical advantages of high output power, simplified water/heat management, increased tolerance to fuel impurities and diverse fuel sources, within the temperature range of 120–200 ℃. However, for practical automobile applications, it was crucial to broaden their low-temperature operating window and enable cold start-up capability. Herein, gel-state phosphoric acid(PA) doped sulfonated polybenzimidazole(PBI) proton exchange membranes(PEMs) were designed and synthesized via PPA sol-gel process and in-situ sultone ring-opening reactions with various proton transport pathways based on absorbed PA, flexible alkyl chain connected sulfonic acid groups and imidazole sites. The effects of flexible alkyl sulfonic acid side chain length and content on PA doping level, proton conductivity, and membrane stability under different temperature and relative humidity(RH) were thoroughly investigated. The prepared gel-state membranes contained a self-assembled lamellar and porous structure that facilitated the absorption of a large amount of PA with rapid proton transporting mechanisms. At room temperature, the optimized membrane exhibited a proton conductivity of 0.069 S cm^(-1), which was further increased to 0.162 and 0.358 S cm^(-1)at 80 and 200 ℃, respectively, without additional humidification. The most significant contribution of this work was demonstrating the feasibility of gel-state sulfonated PBI membranes in expanding HT-PEMFC application opportunities over a wider operating range of 25 to 240 ℃.

Moderately concentrated electrolyte enabling high-performance lithium metal batteries with a wide working temperature range

The electrolyte integrated with lithium metal anodes is subjected to the issues of interfacial compatibility and stability,which strongly influence the performances of high-energy lithium metal batteries.Here,we report a new electrolyte recipe viz.a moderately concentrated electrolyte comprising of 2.4 M lithium bis(fluorosulfonyl)imide(LiFSI)in a cosolvent mixture of fluorinated ethylene carbonate(FEC)and dimethyl carbonate(DMC)with relatively high ion conductivity.Owing to the preferential decomposition of LiFSI and FEC,an inorganic-rich interphase with abundant Li_(2)O and LiF nanocrystals is formed on lithium metal with improved robustness and ion transfer kinetics,enabling lithium plating/stripping with an extremely low overpotential of~8 mV and the average CE of 97%.When tested in Li||LiFePO_(4) cell,this electrolyte provides long-term cycling with a capacity retention of 98.3%after 1000 cycles at 1 C and an excellent rate performance of 20 C,as well as an areal capacity of 1.35 mA h cm^(-2)at the cathode areal loading of 9 mg cm^(-2).Moreover,the Li||LiFePO_(4) cell exhibits excellent wide-temperature performances(-40~60℃),including long-term cycling stability over 2600 cycles without visible capacity fading at 0℃,as well as extremely high average CEs of 99.6%and 99.8% over 400 cycles under-20℃ and 45℃.

Progress in Electrolyte Engineering of Aqueous Batteries in a Wide Temperature Range

Aqueous rechargeable batteries are safe and environmentally friendly and can be made at a low cost;as such,they are attracting attention in the field of energy storage.However,the temperature sensitivity of aqueous batteries hinders their practical application.The solvent water freezes at low temperatures,and there is a reduction in ionic conductivity,whereas it evaporates rapidly at high temperatures,which causes increased side reactions.This review discusses recent progress in improving the performance of aqueous batteries,mainly with respect to electrolyte engineering and the associated strategies employed to achieve such improvements over a wide temperature domain.The review focuses on fi ve electrolyte engineer-ing(aqueous high-concentration electrolytes,organic electrolytes,quasi-solid/solid electrolytes,hybrid electrolytes,and eutectic electrolytes)and investigates the mechanisms involved in reducing the solidifi cation point and boiling point of the electrolyte and enhancing the extreme-temperature electrochemical performance.Finally,the prospect of further improving the wide temperature range performance of aqueous rechargeable batteries is presented.

Mixed salts for lithium iron phosphate-based batteries operated at wide temperature range

To achieve good performance for LiFePO4-based batteries operated at a wide temperature range,mixed salts of LiBF4 LiBOB（lithium bis（oxalato）borate） and LiTFSI（lithium bis（trifluoromethanesulfonyl）imide）-LiBOB were investigated as alternative lithium salts to LiPF6 in non-aqueous electrolytes.LiFePO4/Li half cells using LiPF6,LiBF4-LiBOB and LiTFSI-LiBOB slats as lithium salts were investigated by galvanostatic cycling,cyclic voltammetry,thermogravimetric analysis.The results show that LiBF4-LiBOB and LiTFSI-LiBOB mixed salts are much more thermally stable than LiPF6.Corrosion of Al foil in the LiTFSI-based electrolytes can be suppressed successfully by the addition of LiBOB as a co-salt.The electrochemical performance of LiBF4-LiBOB and LiTFSI-LiBOB mixed salts based cells are both better than that of LiPF6-based cell.LiTFSI-LiBOB mixed salt based electrolyte is considered to be a very promising electrolyte candidate for Li-ion batteries that will be used in wide-temperature applications.

Wide temperature range,air stable,transparent,and self-powered photodetectors enabled by a hybrid film of graphene and singlewalled carbon nanotubes

Transparent photovoltaic devices(TPVDs)have attracted increasing attention in emerging electronic devices.As the application scenarios extend,there raise higher requirements regarding the stability and operating temperature range of TPVDs.In this work,a unique preparation strategy is proposed for air stable TPVD with a wide operating temperature range,i.e.,a nanoscale architecture termed as H-TPVD is constructed that integrates a free-standing and highly transparent conductive hybrid film of graphene and single-walled carbon nanotubes(G-SWNT TCF for short)with a metal oxide NiO/TiO_(2)heterojunction.The preparation approach is suitable for scaling up.Thanks to the excellent transparent conductivity of the freestanding G-SWNT hybrid film and the ultrathin NiO/TiO_(2)heterojunction(100 nm),H-TPVD selectively absorbs the ultraviolet(UV)band of sunlight and has a transparency of up to 71%in the visible light.The integrated nanoscale architecture manifests the significant holecollecting capability of the G-SWNT hybrid film and the efficient carrier generation and separation within the ultrathin NiO/TiO_(2)heterojunction,resulting in excellent performance of the H-TPVD with a specific detectivity of 2.7×10^(10) Jones.Especially,the freestanding G-SWNT TCF is a super stable and non-porous two-dimensional film that can insulate gas molecules,thereby protecting the surface properties of NiO/TiO_(2)heterojunctions and enhancing the stability of H-TPVD.Having subjected to 20,000 cycles and storage in air for three months,the performance parameters such as photo-response signal,output power,and specific detectivity show no noticeable degradation.In particular,the as-fabricated self-powered H-TPVD can operate over a wide temperature range from −180 to 300℃,and can carry out solar-blind UV optical communication in this range.In addition,the 4×4 array H-TPVD demonstrates clear optical imaging.These results make it possible for H-TPVD to expand its potential application scenarios.

Performance analysis of a single-stage scroll compressor used in a drying heat pump over a wide condensing temperature range(30–80°C)

This study presents the performance of a new single-stage scroll compressor used for the heat pump drying of thermally sensitive materials over a wide temperature range. The performance of the new compressor was predicted by an ARI standard 540 map-based compressor model and verified by a semi-open drying heat pump system constructed for this purpose. A comparison of the experimental data with the predicted data proved that the new scroll compressor used in the drying heat pump works well, can supply a wide range of condensing temperatures （30--80℃） （without auxiliary heating）, and has a minimum coeffi- cient of performance （COP） above 2.0, even in the worst condition.

Exploiting ultra-large linear elasticity over a wide temperature range in nanocrystalline NiTi alloy

Many shape memory alloys can support large recoverable strains of a few percent by reversible stressinduced martensite transformation,yet they behave non-linear within a narrow operating temperature ra nge.Developing the bulk metallic materials with ultra-large linear elasticity over a wide tempe rature range has proven to be difficult.In this work,a material design concept was proposed,that is true elastic deformation and reversible twinning-detwinning deformation run in parallel to overcome this challe nge.By engineering the residual internal stress to realize the concurrency of true elastic deformation and twinning-detwinning deformation,a bulk nanocrystalline NiTi that possesses an ultra-large linear elastic strain up to 5.1 % and a high yield stress of 2.16 GPa over a wide temperature range of 270℃ was developed.This study offers a new avenue for developing the metallic materials with ultra-large linear elasticity over a wide temperature range of 270℃(from 70℃ to-197℃).

Fe3O4-nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures with improved lithium-ion battery performance over wide temperature range

A facile strategy was designed for the fabrication of Fe3O4-nanoparticle- decorated TiO2 nanofiber hierarchical heterostructures （FTHs） by combining the versatility of the electrospinning technique and the hydrothermal growth method. The hierarchical architecture of Fe3O4 nanoparticles decorated on TiO2 nanofibers enables the successful integration of the binary composite into batteries to address structural stability and low capacity. In the resulting unique architecture of FTHs, the 1D heterostructures relieve the strain caused by severe volume changes of Fe3O4 during numerous charge-discharge cycles, and thus suppress the degradation of the electrode material. As a result, FTHs show excellent performance including higher reversible capacity, excellent cycle life, and good rate performance over a wide temperature range owing to the synergistic effect of the binary composition of TiO2 and Fe304 and the unique features of the hierarchical nanofibers.

Directly modulated active distributed reflector distributed feedback lasers over wide temperature range operation(-40 to 85℃)

We experimentally demonstrated that the distributed feedback(DFB) lasers with the active distributed reflector achieved a 25.8 Gb/s operation over a wide temperature range of -40 to 85℃. The DFB lasers can achieve additional feedback from an active distributed reflector with accurately controlled phase, and single-mode yields are not related to the position of cleave. The threshold currents of the fabricated laser are 6 mA and 20 mA at -40℃ and 85℃, respectively. The side mode suppression ratio of the fabricated laser is above 50 dB at all temperatures. Transmissions of 25.8 Gb/s after 10 km single-mode fibers with clear eye openings and less than 0.8 dB power penalty over a wide temperature range have been demonstrated as well.

Electrostatic Interaction Tailored Anion-Rich Solvation Sheath Stabilizing High-Voltage Lithium Metal Batteries

Through tailoring interfacial chemistry,electrolyte engineering is a facile yet effective strategy for highperformance lithium(Li)metal batteries,where the solvation structure is critical for interfacial chemistry.Herein,the effect of electrostatic interaction on regulating an anion-rich solvation is firstly proposed.The moderate electrostatic interaction between anion and solvent promotes anion to enter the solvation sheath,inducing stable solid electrolyte interphase with fast Li+transport kinetics on the anode.This asdesigned electrolyte exhibits excellent compatibility with Li metal anode(a Li deposition/stripping Coulombic efficiency of 99.3%)and high-voltage LiCoO_(2) cathode.Consequently,the 50μm-thin Li||high-loading LiCoO_(2) cells achieve significantly improved cycling performance under stringent conditions of high voltage over 4.5 V,lean electrolyte,and wide temperature range(-20 to 60℃).This work inspires a groundbreaking strategy to manipulate the solvation structure through regulating the interactions of solvent and anion for highperformance Li metal batteries.

Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing

Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.

Diminishing ether-oxygen content of electrolytes enables temperature-immune lithium metal batteries

The reversibility of lithium(Li) metal anodes is highly susceptible to temperature,owing to the aggravated side reactions at high temperatures and serious Li dendrite growth at low temperatures.Thus it is extremely challenging to simultaneously realize the high Li reversibility in both low and high temperature scenarios.Herein,an oxygen-free solvent(n-hexane,HEX) assisted with the hexyl methyl ether and 1 mol L^(-1)lithium bis(fluorosulfonyl)imide is proposed to constitute an electrolyte for temperatureimmune lithium metal batteries.It demonstrates that the HEX not only greatly suppresses the solvent reduction even at high temperatures but also weaken the Li~+-solvent interaction for the facile Li-ion desolvation,leading to high Li Coulombic efficiencies(99.59% at 25℃,99.30%at 60℃ and 98.75% at -30℃) and the dendrite-free Li plating from -30℃ to 60℃.Benefitting from the low density and temperature-immune properties of our electrolyte,the sulfurized polyacrylonitrile(3.8mAh cm^(-2))||Li(60 μm) pouch-cells deliver 278 Wh kg^(-1)energy density and maintain the stable performance over 50 cycles,and retain 248 and 320 Wh kg^(-1) energy density at -30℃ and 60℃,respectively.This work provides a new perspective on the electrolyte design for wide-temperature Li metal batteries.

A Frequency Tunable Liquid Cavity Bandpass Filter

A liquid-loaded frequency tunable cavity bandpass filter (BPF) is presented. A dielectric fluidic material, dimethyl silicone oil (DSO) withexcellent thermophysical characteristics (working temperature from −50 ℃ to 180 ℃) and extremely low loss tangent is employed as a dielectric loading.The frequency reconfigurability of the proposed design is realized by altering the liquid level inside the cavity resonator. The filter achieves a widefrequency tuning range as well as a high Q factor. Moreover, this design shows significantly improved environmental suitability in extreme temperaturecases, outperforming the existing microfluidic-based RF devices using water or liquid metals. A four-pole tunable cavity bandpass filter is designed andverified. A cross-coupling structure comprising a metal loop structure is used to introduce transmission zeros in the proposed filter, which enhances theskirt selectivity and out-of-band rejections. We demonstrate that the center frequency of the proposed BPF can be tuned from 4.92 GHz to 6.16 GHz,and the filter achieves a high Q factor between 521 and 1527. The measured results agree well with simulated results.

Flexible lead-free BFO-based dielectric capacitor with large energy density,superior thermal stability,and reliable bending endurance

As an essential energy-stored device,the inorganic dielectric film capacitor plays an irreplaceable role in high-energy pulse power technology area.In this work,propelled by the challenge of overcoming the bottlenecks of inflexibility and inferior energy storage density of the pure BiFeO3 films,the mica with high bendability and thermal stability is adopted as substrate,and the relaxor ferroelectric(Sr_(0.7)Bi_(0.2))TiO_(3) is introduced to form solid solution to introduce relaxor behavior.The subsequently fabricated 0.3Bi(Fe_(0.95)Mn_(0.05))O_(3)-0.7(Sr_(0.7)Bi_(0.2))TiO_(3)(BFMO-SBT)thin film capacitor exhibits a high recoverable energy storage density(W_(rec)=61 J cm^(-3))and a high efficiency(η=75%)combined with a fast discharging rate(23.5 μs)due to the large polarization difference(ΔP=59.4 μC cm^(-2)),high breakdown strength(E_(b)=3000 kV cm^(-1)),and the strong relaxor dispersion(γ=1.78).Of particular importance is the capacitor presents excellent stability of energy storage performance,including a wide working temperature window of -50-200℃,fatigue endurance of 108 cycles,and frequency range of 500 Hz-20 kHz.Furthermore,there are no obviously deteriorations on energy storage capability under various bending states and after 104 times of mechanical bending cycles.All these results indicate that BFMO-SBT on mica film capacitor has potential application in the future flexible electronics.