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Facile fabrication of binder-free carbon nanotube-carbon nanocoil hybrid films for anodes of lithium-ion batteries

JOURNAL OF SOLID STATE ELECTROCHEMISTRY 2024年第9期28卷 3325-3335页

作者： Chen, Huan Wang, Chen Fan, Zeng Hao, Liang Pan, Lujun Dalian Univ Technol Sch Integrated Circuits Dalian 116024 Liaoning Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Dalian Univ Technol Sch Phys Dalian 116024 Liaoning Peoples R China Fudan Univ Sch Microelect State Key Lab ASIC & Syst Shanghai 200433 Peoples R China

The electrochemical performance of lithium-ion batteries (LIBs) depends dramatically on the composition, microstructure, and morphology of anode materials. The development of carbon nanotube (CNT)-based anode materials is of great significance. However, the easy agglomeration and winding of CNTs hinder the embedding of lithium ions (Li+), leading to the failure of the battery at a high rate when the CNT film is solely used as anode. Herein, binder-free hybrid films of CNTs and carbon nanocoils (CNCs) were fabricated by the facile vacuum-assisted filtration method. The uniform dispersion of helical CNCs in the densely compacted CNTs results in a large number of passways and space to achieve rapid charge transmission. It is found that the storage capacities of Li+ are strongly dependent on the mixing ratio of CNTs and CNCs. The highest storage capacities of Li+ are obtained in the CNT-CNC film at a mixing ratio of 4:1. The CNT-CNC film electrode still has a charge and discharge capacity of 300 mAh/g even at a high specific current of 800 mA/g, while the CNT film electrode has 150 mAh/g. These results indicate that the CNT-CNC hybrid film is a promising material to be used as binder-free anodes for LIBs.

关键词： Carbon nanotubes Carbon nanocoils Hybrid film Anode Lithium-ion battery

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Effect of constraint on cyclic plastic behaviours of cracked bodies and the establishment of unified constraint correlation

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EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 2023年 97卷

作者： Wang, Xiaoxiao Yang, Jie Chen, Haofeng Ma, Zhiyuan Xuan, Fuzhen Univ Strathclyde Dept Mech & Aerosp Engn Glasgow G1 1XJ Scotland Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China East China Univ Sci & Technol Sch Mech & Power Engn Shanghai 200237 Peoples R China

Constraint effect existing in the cracked structures plays a vital role in monotonic loading conditions and affects the material fracture behaviour, it is not clear whether the constraint affects the cyclic plastic responses in the cyclic loading condition. In this research, the laboratory compact tension (CT) and central-cracked tension (CCT) specimens with different in-plane and out-of-plane constraints were selected to explore the constraint effect on the ratchet limit and cyclic plastic behaviour numerically by the Linear Matching Method (LMM). The results show that the plastic shakedown load domain and low cycle fatigue (LCF) life are compressed dramatically by increasing the in-plane constraint effect, while the out-of-plane constraint effect elevates the capability to resist ratcheting failure. In addition, the ratcheting boundary of the cracked specimen is much more sensitive and vulnerable under the influence of the high in-plane constraint effect. Moreover, the unified constraint parameter A(p) is suitable to measure the strength of compound constraint under cyclic loading conditions, and there is a salient linear relation between constraint parameter root Ap and cyclic plastic responses (including ratchet limit and alternating plastic strain range) of the cracked specimen. This correlation is very meaningful for evaluating the ratchet limit and low cycle fatigue (LCF) life of cracked structures in terms of different levels of constraint conditions (including different in-plane, out-of-plane, and compound constraint conditions), where the constraint effect is calibrated based on the unified constraint parameter A(p).

关键词： Constraint Cracked body Cyclic plastic behaviour Ratcheting Linear Matching Method

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Experimental study and modelling of continuous SO2-depolarized electrolysis in hybrid sulfur cycle for hydrogen production

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JOURNAL OF CLEANER PRODUCTION 2024年 435卷

作者： Ying, Zhi Yang, Aoli Zhao, Muyang Yang, Jingyang Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Sch Energy & Power Engn Shanghai 200093 Peoples R China

SO2-depolarized electrolysis (SDE) is the key process in the hybrid sulfur cycle for green hydrogen production, but the detailed SDE characteristics including products generation, current efficiency variation, and side reactions are unclear. Herein, a continuous SDE process was experimentally conducted and theoretically modelled. The H-2 and H2SO4 production was accelerated and the current efficiency for both electrodes was improved with a proper increase in current density (50-100 mA/cm(2)) or temperature (293-318 K), but further increasing current density to 150 mA/cm(2) or temperature to 333 K led to a negative trend because of the anode corrosion or declined SO2 solubility. The increasing initial H2SO4 concentration (10-40 wt%) facilitated the cathodic H-2 production and current efficiency, while negatively influenced the anodic SO2 conversion. The parasitic reactions occurred at cathode consumed H-2 and resulted to the cathodic current efficiency well below 100%. A rigorous mathematical regression model correlating the production rates of H-2 and H2SO4 with current density, temperature, and initial H2SO4 concentration was developed, and combined with the analysis of variance, current density was suggested the biggest factor affecting products generation in SDE process. These findings demonstrate a practical avenue for efficient SO2 conversion and H-2 production in SDE process of hybrid sulfur cycle.

关键词： hydrogen production Hybrid Sulfur Cycle SO2-depolarized electrolysis (SDE) Current efficiency Modelling

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A Li-O2 battery model coupled with LiO2 and Li2O2 reveals regulation mechanism of deposited product composition on mass transport and electron transfer

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APPLIED ENERGY 2025年 391卷

作者： Wang, Yuanhui Zang, Linfeng Dou, Shaojun Hao, Liang Yanshan Univ Sch Vehicle & Energy Hebei Engn Res Ctr Low Carbon Dev & Resource Utili Qinhuangdao 066004 Peoples R China Dalian Univ Technol Sch Energy & Power Engn Dalian 116024 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

To elucidate the regulation mechanism of deposited product composition on the coupling process of mass transport and electron transfer in lithium-oxygen (Li-O2) batteries, a novel multi-step discharge/charge model with solid lithium superoxide (LiO2(s)) and lithium peroxide (Li2O2) as hybrid precipitation is proposed. This model couples the dynamic competitive growth mechanisms between LiO2(s) and Li2O2, while incorporating the asymmetric deposition and decomposition behaviors of Li2O2. The electrode surface passivation caused by the sluggish kinetic rate of electron across the Li2O2 film is solely responsible for the deep discharge termination based on the reduced graphene oxide cathode. LiO2(s) dominates the precipitation products with a limited capacity and a continuous decline in the LiO2(s) percentage with discharge depth. Although promoting the LiO2(s) formation is conducive to alleviating the electrode surface passivation, it aggravates the O2 transport resistance due to occupying more electrode pores with the same charge contribution. Hence the discharge capacity demonstrates a three-stage variation with increasing lithium superoxide (LiO2) formation rate, which rapidly grows by more than two times in stage 2 benefiting from the increased LiO2(s) percentage and enhanced solution mechanism. Whereas a slow rise of 32 % in the discharge capacity in stage 3 is attributed to the conversion of LiO2(s) to Li2O2 toroid for the discharge process controlled by O2 transport. An increase in the thickness or specific surface area of the cathode improves the discharge capacity mainly by facilitating the production of Li2O2 toroid despite the decrease in the LiO2(s) percentage, which is different from the regulatory mechanism of electrode porosity for accelerating the LiO2(s) formation. Increasing LiO2 solubility predominantly mitigates the electrode surface passivation through enhancement of the solution pathway, whereas the elevated O2 solubility synergistically facilita

关键词： Li-O-2 batteries Multistep discharge/charge model LiO2(s)/Li2O2 hybrid precipitation Reaction pathway regulation Surface passivation/O-2 transport

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Evolution of a single sessile droplet under the influence of the dielectric barrier discharge plasma actuator

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PHYSICS OF FLUIDS 2022年第12期34卷 1-14页

作者： Zuo, Zi-chao Zhang, Xin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China China Aerodynam Res & Dev Ctr State Key Lab Aerodynam Mianyang 621000 Peoples R China

Ice accretion on airplane surfaces has been widely recognized as a significant safety threat, and corresponding investigations of anti-/de-icing technologies have experienced tremendous growth during the last two decades. Dielectric barrier discharge plasma actuators involve different characteristics, such as thermal, acoustic, and flow characteristics, which are well suited for reducing and preventing ice accretion on wing surfaces effectively and safely. However, the correlation between the droplet, as the core of ice formation, and the plasma actuator is still not very clear. In order to understand the anti-/de-icing mechanism of the plasma actuator further, the evolution of a single sessile droplet under the influence of a symmetrical plasma actuator is studied. Interestingly, the oscillation of the droplet is first observed on the initiation of the plasma actuator, which is quite different from the droplet variation under traditional heating or cooling. Then, the flow field inside the droplet under the effect of the induced flow field of the plasma actuator is first uncovered by using the particle image velocimetry system. Subsequently, the evolution process of droplet deformation, deformed droplet moving downstream, deformed droplet moving downstream and evaporating, and water film moving downstream and evaporating is revealed. In addition, the underlying mechanism of the evolution process of the droplet is discussed based on the different characteristics of the plasma actuator. This study provides an in-depth understanding of the correlation between the droplet and the plasma actuation and lay a foundation for proposing the optimized strategy of anti-/de-icing using plasma actuators. Published under an exclusive license by AIP Publishing.

关键词： flow control

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VOF based model of numerical simulation for single aluminum droplet evaporation and combustion

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JOURNAL OF ENERGETIC MATERIALS 2024年

作者： Wang, Jia-Hao Yang, Bin Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet's windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration's role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.

关键词： Aluminum droplets Convective evaporation Evaporation rate heat and mass transfer VOF

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Experimental study and exergy analysis of electric vehicle single-stage compression secondary throttling CO 2 air-source heat pump system in cold climate

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INTERNATIONAL JOURNAL OF REFRIGERATION 2024年 164卷 75-85页

作者： Wang, Fengxian Wu, Weidong Wang, Rujin Chen, Lang Zhang, Hua Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai MAHLE Thermal Syst Co Ltd Shanghai 201206 Peoples R China Hefei Gen Machinery Res Inst Co Ltd Hefei 230031 Peoples R China Univ Shanghai Sci & Technol 516 Jungong Rd Shanghai 200093 Peoples R China

A novel CO 2 air-source heat pump system (ASHPs) with a secondary throttling based on a single-stage compression was proposed to further improve the heating energy efficiency of electric vehicles (EVs) for heating in cold climates. The heating characteristics of the secondary throttling system (STS) and conventional throttling system (CTS) at different indoor air supply temperatures were compared. The STS performance characteristics were investigated under varying ambient temperature, outdoor air velocity, and exergy analysis was performed on the system and its components. A fitting correlation equation for optimal discharge pressure was obtained based on experimental data. The results demonstrate that implementing STS significantly reduces CO 2 ASHPs energy consumption ( W com ), enhances the coefficient of performance (COP), and reduces exergy destruction. When the indoor air supply temperature reaches 45 degrees C, using STS can result in an 8.1 % reduction in W com , a 9.4 % increase in COP, and a 6.1 % improvement in the exergy efficiency ( Ex eta ) compared to that of CTS. Furthermore, the advantages of STS become more pronounced with higher indoor target air supply temperatures. As the ambient temperature decreases, the exergy efficiency of the STS reaching the target air supply temperature decreases. The velocity of outdoor air significantly affects the STS performance, and increasing outdoor air velocity can effectively enhance the Ex eta of STS. The optimal discharge pressure fitting equation for the STS was obtained through multiple linear regression analysis. These findings can provide ideas for architectural optimization and design of CO 2 ASHPs for EVs, which are important for further improving system performance.

关键词： CO2 heat pump System performance optimization Exergy analysis Secondary throttling Electric vehicles Optimisation des performances dusyste`me Pompea` chaleur auCO2 Analyseexergetique Etranglement secondaire Vehiculeselectriques

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Electrochemical activation of biochar and energy-saving hydrogen production by regulation of biochar-assisted water electrolysis

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ENERGY CONVERSION AND MANAGEMENT 2024年 300卷

作者： Gu, Xufei Ying, Zhi Zheng, Xiaoyuan Du, Yueyue Sun, Hao Chen, Xinyue Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Biochar-assisted water electrolysis (BAWE) has the potential to reduce the electricity consumption of hydrogen production. However, prolonged electrolysis leads to over-oxidation of biochar, reduced reactivity, and decreasing hydrogen production at cathode. Herein, we proposed the electrochemical activation of biochar via limited biochar oxidation reaction (BOR) and hydrogen evolution reaction (HER) in BAWE process, and the upgraded biochar was employed to remove Cr(VI). Distinct biochar was first pyrolyzed from three kinds of representative biomass components, cellulose, lignin, and their mixture at different temperatures. All of them exhibited excellent BOR activity, especially the biochar derived by the pyrolyzed cellulose and lignin at 800 degrees C (MBC-800) required a potential as low as 1.319 V vs. RHE@1 mA cm(-2) using Pt electrode in 1 M KOH and achieved a Faraday efficiency almost 100% for hydrogen production. BAWE presented an energy-saving electrical consumption of 4.98 kWh Nm(-3) H-2 compared to the conventional water electrolysis of 5.32 kWh Nm(-3) H-2. Electrochemical oxidation enriched the oxygen-containing groups on biochar surface, which significantly improved its reductivity towards Cr(VI) and complexation with Cr(III), leading to the removal rate of Cr(VI) more than doubled. Results showed the achievement of electrochemical activation of biochar by limited electrooxidation. These findings provide a new route for the high-value utilization of biochar and energy-saving electrolytic hydrogen production.

关键词： Biochar-assisted water electrolysis Hydrogen production Biochar Electrochemical activation Adsorption Cr(VI)

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Frosting characteristics and performance impact on R744 heat pump systems for electric vehicles at low ambient temperatures: An experimental approach

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APPLIED THERMAL engineering 2025年 266卷

作者： Li, Kang Kong, Fanyue Liu, Ni Zhang, Hua Dou, Binlin Li, Chao He, Qize Tian, Yafen Tu, Ran Mohtaram, Soheil Zhou, Xuejin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P 516 Jun Gong Rd Shanghai 200093 Peoples R China Invest Design & Res Inst Co Ltd Shanghai 200080 Peoples R China Shanghai Fire Res Inst MEM Shanghai 200032 Peoples R China Huaqiao Univ Coll Mech Engn & Automat Xiamen 361021 Fujian Peoples R China

With global warming and the depletion of fossil fuels, electric vehicles have emerged. Although their carbon dioxide heat pump systems are environmentally friendly, they face the problem of frosting on outdoor heat exchangers. Previous studies have mainly focused on the internal factors of heat exchangers or specific operating conditions, with limited exploration of frosting behavior in electric vehicles under complex operating conditions, especially in supercritical high-pressure environments of carbon dioxide electric vehicles. This study builds an experimental platform for a carbon dioxide electric vehicle heat pump system, using an infrared thermal imager to capture accurate data on outdoor heat exchanger temperature and frost development. Different environmental temperatures and compressor speeds are set at high humidity levels of 85-95% to study the distribution of frost layer growth in outdoor heat exchangers under different operating conditions. The study also introduced FCR to analyze the changes in heat pump performance parameters in different FCR regions. Finally, under the same environmental temperature, humidity, and speed conditions, the frosting characteristics of R744 and R134a heat pump systems were compared, and the impact of frosting on them was analyzed. The results indicate that in high humidity environments, lower ambient temperatures and higher rotational speeds increase frost coverage. When FCR exceeds 40%, the suction pressure of the compressor significantly decreases, the heating capacity of the system decreases by 26.01% to 31.08%, and the COP decreases by 21.59% to 29.69%. Regardless of the compressor speed, the COP decreases by about 21% after frosting. Under similar conditions, R134a heat exchanger has more severe frosting than R744, which has a greater impact on the suction pressure of R134a compressor. However, frosting reduces the heating capacity of both systems by about 30%.

关键词： Electric vehicles Outdoor heat exchanger Frost formation CO2 heat pump system

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Suppressing thermal stress in the vicinity of a circular nano-inhomogeneity via the mechanism of size effects

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MATHEMATICS AND MECHANICS OF SOLIDS 2023年第8期28卷 1863-1876页

作者： Huang, Haojie Xing, Shichao Song, Kun Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Tongling Univ Key Lab Construction Hydraul Robots Anhui Higher Educ Inst Tongling Peoples R China Nanjing Tech Univ Sch Mech & Power Engn 30 Puzhu South Rd Nanjing 211816 Peoples R China

Thermal stress is one of the main factors threatening the reliability of nanocomposites. In this paper, we propose a set of interfacial conditions to simulate the interfacial phonon scattering and interfacial elasticity in the nanocomposite, and then obtain closed-form solutions for the thermal-elastic fields around the circular nano-inhomogeneity. The results show that the interfacial thermal stress within matrix is more sensitive to interfacial phonon scattering than that in nano-inhomogeneity, while the size change of inhomogeneity has greater impact on the stress of nano-inhomogeneity than that of the matrix. In view of the significant effects of thermal conductivities and thermal expansion coefficients on the thermal stress around inhomogeneity, the maximum von Mises stress is reduced up to three orders of magnitude by adjusting these parameters. More importantly, the thermal stresses within matrix and inhomogeneity can be, respectively, designed as "zero" even though the nanocomposite is subjected to a large thermal loading, which is viewed as an update mechanism of "neutral inhomogeneity." Our work provides guidance for the design of nanocomposites and has important potential applications.

关键词： Thermal stress nano-inhomogeneity interfacial phonon scattering interfacial elasticity complex variable method

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