Studies of tin–transition metal–carbon and tin–cobalt–transition metal–carbon negative electrode materials prepared by mechanical attrition

Samples of Sn₃₀TM₃₀C₄₀ and of Sn₃₀Co₁₅TM₁₅C₄₀, with TM = 3d transition metals, were prepared by vertical-axis attritor milling. The structure and performance of these samples were studied by X-ray diffraction (XRD) and by electrochemical testing. The XRD patterns of Sn₃₀TM₃₀C₄₀ show an amorphous-like diffraction pattern only for the sample with TM = Co. The other prepared samples show broadened Bragg peaks of their main starting material, along with an amorphous-like background, even after 32 h of milling. Samples with TM = Co and TM = Ni show stable differential capacity versus potential plots and stable cycling for at least 100 cycles with reversible capacities of 425 and 250 mAh g⁻¹, respectively. All samples prepared with 15 at.% Co show good capacity retention for at least 100 cycles ranging from 270 mAh g⁻¹ for samples with TM = Ni to 500 mAh g⁻¹ for samples with TM = Ti. The differential capacity versus potential plots for all the prepared Sn₃₀Co₁₅TM₁₅C₄₀ samples show similar structure to that of Sn₃₀Co₃₀C₄₀ except when TM = Cu. This shows the possibility of preparing tin-based negative electrode materials using a combination of cobalt and TM, especially if one looks to reduce the cobalt content.     

β‐molybdenum carbide/carbon nanofibers as a shuttle inhibitor for lithium‐sulfur battery with high sulfur loading

We report the synthesis of β‐molybdenum carbide/carbon nanofibers (β‐Mo₂C/CNFs) by electrospinning and annealing process, when exploited as an interlayer in Li‐S batteries, demonstrating significantly improved electrochemical behaviors. The synthesized β‐Mo₂C/CNFs with 3D network structure and high surface area are not only conducive to ion transport and electrolyte penetration but also effectively intercept the shuttle of lithium polysulfide by polar surface interaction. Moreover, the reaction kinetics of the batteries enhanced is due to the presence of β‐Mo₂C, promoting the solid‐state polysulfide conversion reaction in the charge‐discharge process. Compared with the batteries with CNF interlayer and without interlayer, the batteries using a β‐Mo₂C/CNFs interlayer with a sulfur loading of 4.2 mg cm^‐2 delivered excellent electrochemical performance because of a facile redox reaction during cycling. The discharge capacity at the first cycle at 0.7 mA cm^?2 was 1360 mAh g^?1, maintaining a specific capacity of 974 mAh g^?1 after 160 cycles. Furthermore, it showed a high‐rate capacity of 700 mAh g^?1 at 14 mA cm^?2. This work demonstrates the β‐Mo₂C/CNFs as a promising interlayer to exploit Li‐S battery commercialization.     

Surface modification of LiNi0.5Co0.2Mn0.3O2 cathode materials with Li2O‐B2O3‐LiBr for lithium‐ion batteries

LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathode material suffers from phase transformation and electrochemical performance degradation as its main drawbacks, which are strongly dependent on the surface state of NCM523. Herein, an effective surface modification approach was demonstrated; namely, the fast lithium‐ion conductor (Li₂O‐B₂O₃‐LiBr) was coated on NCM523. The Li₂O‐B₂O₃‐LiBr coating layer as a protecting shell can prevent NCM523 particles from corrosion by the acidic electrolyte, leading to a superior discharge capacity, rate capability, and cycling stability. At room temperature, the Li₂O‐B₂O₃‐LiBr–coated NCM523 exhibited an excellent capacity retention of 87.7% after 100 cycles at the rate of 1 C, which is remarkably better than that (29.8%) without the uncoated layer. Furthermore, the coating layer also increased the discharge capacity of NCM523 cathode material from 68.7 to 117.0 mAh g^?1 at 5 C. Those can be attributed to the reduction in the electrode polarization and improvement in the electrode conductivity, which was supported by electrochemical impedance spectroscopy and cyclic voltammetry measurements.     

Estimation of Nusselt number and effectiveness of double‐pipe heat exchanger with Al2O3–, CuO–, TiO2–, and ZnO–water based nanofluids

This paper deals with experimental studies carried out to analyze heat transfer characteristics of Al₂O₃–, CuO–, TiO₂–, and ZnO–water based nanofluids in a double‐pipe, counter flow heat exchanger for different volume concentrations (0.025%, 0.05%, 0.075%, and 0.1%) of the nanofluids. The fabricated double‐pipe heat exchanger is made up of two different materials, viz., copper as the inner tube and unplasticized polyvinyl chloride as the outer tube. The density, viscosity, and thermal conductivity were calculated, and were used to estimate dimensionless numbers, such as Reynolds number, Prandtl number, and Nusselt number, and also to estimate heat exchanger effectiveness. High‐energy ball milling technique was used to prepare nanoparticles and were characterized using X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. Polyvinyl alcohol (3%) was used as a surfactant for making the nanofluids stable. It was observed from the experiment that with the increase in the volume concentration, thermal conductivity, viscosity, and friction factor increase, whereas the Reynolds number decreases. The experimentally observed data for Nusselt number were formulated into a correlation that matches the data for all these nanofluids within an error of 11.4%. It was found that the highest effectiveness was obtained while using TiO₂–water nanofluids than other nanofluids.     

Electrochemical corrosion of Pb–1 wt% Sn and Pb–2.5 wt% Sn alloys for lead-acid battery applications

The aim of this study was to compare the electrochemical corrosion behavior of as-cast Pb–1 wt% Sn and Pb–2.5 wt% Sn alloy samples in a 0.5 M H₂SO₄ solution at 25 °C. A water-cooled unidirectional solidification system was used to obtain the as-cast samples. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical corrosion response. It was found that a coarse cellular array has a better electrochemical corrosion resistance than fine cells. The pre-programming of microstructure cell size of Pb–Sn alloys can be used as an alternative way to produce as-cast components of lead-acid batteries with higher corrosion resistance associated with environmental and economical aspects.     

Submicron‐sized Sb2O3 with hierarchical structure as high‐performance anodes for Na‐ion storage

Submicron‐sized Sb₂O₃ with hierarchical structure was successfully prepared via a synthesis of one‐step solvothermal chemical route. Na‐ion storage performance of Sb₂O₃ material was investigated. Sb₂O₃ anode exhibits a high reversible capacity (approximately 350 mAh/g) and stable cycle stability (greater than 95%) over 100 cycles at 100 or 200 mA/g. A full battery with Sb₂O₃ anode and P2‐Na_2/3Ni_1/3Mn_1/2Ti_1/6O₂ (PTO) cathode indicated a high energy density of 216.6 Wh/kg.     

Effects of additives on the hydrogen generation of Al–H2O reaction at low temperature

Water displacement method is used to study the influence of temperatures (60–80°C), additives (Na₂CO₃, NaCl, Na₂CO₃/NaCl) and concentrations on the reaction characteristics and kinetics of Al–H₂O. Results show that the reaction rate and the hydrogen yield are enhanced with the increase of the temperature or by adding Na₂CO₃. The reaction rate is decreased by adding NaCl, but which has less effect on the hydrogen yield. For the mixture additive, Na₂CO₃ plays a key role in improving the hydrogen yield and the reaction rate. The influence degree of different factors is analyzed by orthogonal method. The most obvious factor is additive, but additive concentration has a minimum influence. The solid products are collected and analyzed by X‐ray diffraction and transmission electron microscopy. Al, Al(OH)₃ and AlO(OH) are detected. The spherical particles are obviously found at the initial reaction stage. However, they change to flocs at the end of reaction. Kinetic analysis shows that the reaction mechanism of Al–H₂O is changed by adding Na₂CO₃ or mixture, but it is not affected by adding NaCl. Moreover, the apparent activation energy of Al–H₂O is 74.49 kJ mol^?1, while it is only 43.03 kJ mol^?1 for Al–H₂O with 5 wt% Na₂CO₃ addition. Copyright © 2017 John Wiley & Sons, Ltd.     

Impact of battery storage on economics of hybrid wind‐diesel power systems in commercial applications in hot regions

Integration of wind machines and battery storage with the diesel plants is pursued widely to reduce dependence on fossil fuels. The aim of this study is to assess the impact of battery storage on the economics of hybrid wind‐diesel power systems in commercial applications by analyzing wind‐speed data of Dhahran, East‐Coast, Kingdom of Saudi Arabia (K.S.A.). The annual load of a typical commercial building is 620,000 kWh. The monthly average wind speeds range from 3.3 to 5.6 m/s. The hybrid systems simulated consist of different combinations of 100‐kW commercial wind machines (CWMs) supplemented with battery storage and diesel generators. National Renewable Energy Laboratory's (NREL's) (HOMER Energy's) Hybrid Optimization Model for Electric Renewables (HOMER) software has been employed to perform the economic analysis. The simulation results indicate that for a hybrid system comprising of 100‐kW wind capacity together with 175‐kW diesel system and a battery storage of 4 h of autonomy (i.e. 4 h of average load), the wind penetration (at 37‐m hub height, with 0% annual capacity shortage) is 25%. The cost of generating energy (COE, $/kWh) from this hybrid wind–battery–diesel system has been found to be 0.139 $/kWh (assuming diesel fuel price of 0.1$/L). The investigation examines the effect of wind/battery penetration on: COE, operational hours of diesel gensets. Emphasis has also been placed on un‐met load, excess electricity, fuel savings and reduction in carbon emissions (for wind–diesel without battery storage, wind–diesel with storage, as compared to diesel‐only situation), cost of wind–battery–diesel systems, COE of different hybrid systems, etc. The study addresses benefits of incorporation of short‐term battery storage (in wind–diesel systems) in terms of fuel savings, diesel operation time, carbon emissions, and excess energy. The percentage fuel savings by using above hybrid system is 27% as compared to diesel‐only situation Copyright © 2012 John Wiley & Sons, Ltd.     

Electrochemical performance and modeling of lithium‐sulfur batteries with varying carbon to sulfur ratios

Lithium‐sulfur batteries have attracted much research interest because of their high theoretical energy density and low‐cost raw materials. While the electrodes are composed of readily available materials, the processes that occur within the cell are complex, and the electrochemical performance of these batteries is very sensitive to a number of cell processing parameters. Herein, a simple electrochemical model will be used to predict, with quantitative agreement, the electrochemical properties of lithium‐sulfur cathodes with varying carbon to sulfur ratios. The discharge capacity and the polarization were very similar for the lowest sulfur loadings, while above 23.2 wt% sulfur the gravimetric capacity dropped significantly, and there was an increase in the cell polarization. In addition, a transition in the electrode morphology, from well dispersed to aggregated sulfur at the surface, will be reflected in the change in a critical model parameter demonstrating the sensitivity and functionality of even this simple model in predicting complex behavior in the lithium‐sulfur cells.     

Influence of tungsten loading on CO2/O2 reforming of methane over Co‐W–promoted NiO‐Al2O3 nanocatalyst designed by sol‐gel‐plasma

Co‐W–promoted NiAl₂O₄ nanocatalyst with various amount of tungsten (0, 1, 3, and 7 wt.%) was fabricated via hybrid sol‐gel‐plasma method. The nanocatalysts were evaluated by XRD, FESEM, EDX, BET, and FTIR analyses. The samples were utilized in CO₂/O₂ reforming of methane to syngas. EDX results proved the existence of all the applied elements in synthesis. FESEM and BET results illustrated that tungsten addition led to lower surface area, larger particle size, and roughly worse particles scattering. Therefore, Co‐NiAl₂O₄ (NCW0A) presented higher yield; however, yields were reduced for the other samples due to the covering impact of tungsten. As a result of time on streams performance (2880 minutes and at 750°C), the 7 wt.% tungsten promoted sample exhibited stable but lower yield (Y_H2 = 64%). Moreover, NCW1A exhibited more stable and higher yield than NCW0A. Optimum operating parameters were obtained as GHSV = 24 l/g_cat.h, CH₄/CO₂ = 1, and CH₄/CO₂/O₂ = 1/1/0.08. TG‐DTG, EDX, and FESEM analyses were applied for the used samples. TG‐DTG graphs demonstrated that by rising of tungsten loading, lighter and lower amount of coke was formed. Some agglomerations were observed in the EDX images of NCW0A and NCW1A while lower agglomeration was found for the tungsten‐rich sample. Carbon fiber formation was detected in the FESEM images of the used NCW0A while for the others, amount of the deposited coke and carbon fibers decreased.     

Direct conversion of syngas to DME over CuO–ZnO–Al2O3/HZSM‐5 nanocatalyst synthesized via ultrasound‐assisted co‐precipitation method: New insights into the role of gas injection

In this study, direct synthesis of dimethyl ether (DME) is conducted over a bifunctional CuO–ZnO–Al₂O₃/H Zeolite Socony Mobil‐5 (HZSM‐5) nanocatalyst. A hybrid method of ultrasound‐assisted co‐precipitation is used for the synthesis of catalysts, and the effect of gas injection during sonication is investigated. The physicochemical characteristics of the catalysts are analysed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), particle size distribution (PSD), energy dispersive X‐ray (EDX), Brunauer–Emmett–Teller (BET) and Fourier‐transformed infrared (FTIR) methods. In the absence of gas injection, the acetate‐based catalysts have a better morphology and higher surface area than the nitrate‐based catalyst. Gas injection significantly changes the morphology and structural properties of the acetate‐based catalyst. High surface area, narrow PSD and better dispersion of small CuO crystals are obtained in a gas‐injected synthesized sample. DME synthesis experiments showed that the CO conversion and DME selectivity are correlated with surface area, nanocatalyst particle size and its dispersion. The gas‐injected CuO–ZnO–Al₂O₃/HZSM‐5 nanocatalyst that has the highest surface area and the smallest dispersed particles showed more than 70% DME selectivity. The gas‐injected CuO–ZnO–Al₂O₃/HZSM‐5 nanocatalyst exhibited high stability in terms of CO conversion and DME yield over 1440‐min time on a stream test at 275°C, 40 bar and 18 000 cm³ g.h^?1. Copyright © 2014 John Wiley & Sons, Ltd.     

Single and multi‐objective optimization for the performance enhancement of lead–acid battery cell

Electric energy storage systems are used considerably in industries and daily applications. The demand for batteries with high energy content has increased because of their use in hybrid vehicles. Lead–acid batteries have wide applications because of their advantages such as high safety factor and low cost of production. The major shortcoming of lead–acid batteries is low energy content and high dimension and weight. Nowadays, a common method to increase the energy content of lead–acid battery is the experimental method with trial and error, which is time consuming and expensive. In this paper, non‐isothermal one‐dimensional numerical simulation of lead–acid battery with finite volume method is performed. In addition, a cell with higher energy content and lower thickness is designed by using particle swarm optimization algorithm based on developed simulation code. The results of single objective optimization show that an optimal battery that has 27.6% higher energy can be made with the same cell dimension. The results also show that an optimum cell battery can be obtained with a decrease of 24% in thickness while keeping the energy the same. Moreover, a multi‐objective optimization algorithm is utilized to find Pareto optimal solutions while considering the energy content and thickness objectives simultaneously. Copyright © 2016 John Wiley & Sons, Ltd.     

Construction of Li-ion supercapacitor-type battery using active carbon/LiNi0.5Co0.2Mn0.3O2 composite as cathode and its electrochemical performances

采用有机体系（NMP+PVDF）混料及乙醇萃取的方法成功制得活性炭/LiNi_0.5Co_0.2Mn_0.3O₂（AC/NCM）复合电极片,通过设计不同AC/NCM配比能够调控能量和功率密度。选取AC/NCM为1/3配比的复合正极和硬碳（HC）负极组装的超级电容电池循环伏安（CV）曲线呈现近似矩形的容性特征,恒流充放电过程电压随时间的变化（V-t曲线）呈现出良好的线性行为。此外,采用导电炭黑（SP）/碳纳米管（CNT）/石墨烯（graphene）=3/1/1的质量比设计了复合导电剂,立体导电网络的构建有效降低了器件内阻。按照IEC 62660—1标准,在2.5～4.2 V电压窗口,83.4 W/kg功率密度下测得的能量密度高达66.6 W·h/kg,在最大功率密度6.5 kW/kg下测得的能量密度为21.5 W·h/kg。器件充满电后在65℃高温存储168 h能量保有率为97.4%,且无任何胀气现象,平均自放电率为27.5 mV/天,表现出优良的高温特性。采用14 C和50 C电流循环充放电1000次后能量保有率分别为99.06%和96.45%,体现出该超级电容电池的长寿命优势。在12 kW/kg平均放电功率密度下进行脉冲测试,连续放电100次后该器件仍表现出良好的稳定性,表明在车辆启动、脉冲器件等领域具有极大的应用潜力。     

Review on the research of failure modes and mechanism for lead–acid batteries

The lead–acid battery (LAB) has been one of the main secondary electrochemical power sources with wide application in various fields (transport vehicles, telecommunications, information technologies, etc.). It has won a dominating position in energy storage and load‐leveling applications. However, the failure of LAB becomes the key barrier for its further development and application. Therefore, understanding the failure modes and mechanism of LAB is of great significance. The failure modes of LAB mainly include two aspects: failure of the positive electrode and negative electrode. The degradations of active material and grid corrosion are the two major failure modes for positive electrode, while the irreversible sulfation is the most common failure mode for the negative electrode. Introduction of carbon materials to the negative electrodes of LAB could suppress sulfation problem and enhance the battery performance efficiently. This paper will attempt here to pull together observations made by previous research to obtain a more comprehensive and integrative view of LAB failure modes. Moreover, according to a detail investigation to the battery market, we have drawn an objective and optimistic conclusion of LAB prospect. Copyright © 2016 John Wiley & Sons, Ltd.     

Charge/discharge characteristics of Li‐ion batteries with two‐phase active materials: a comparative study of LiFePO4 and LiCoO2 cells

A comparative study of LiFePO₄ and LiCoO₂ cells was conducted using two mathematical models to identify the physical characteristics of the two‐phase electrode compared with the single‐phase electrode under both charge and discharge conditions. First, the electrical conductivity of the LiFePO₄ electrode was examined applying a two‐dimensional electrical conduction model. The calculation results showed that the electrical conductivity of the LiFePO₄ electrode could be improved significantly by coating the LiFePO₄ particles with a conductive substance. Second, a modified physics‐based cell model was applied to simulate the phase‐change phenomena at the equilibrium boundary inside the LiFePO₄ particles. The cell performance using LiFePO₄ electrode was degraded significantly owing to the increase in ohmic loss and concentration loss caused by the low electrical conductivity and phase‐change characteristics of LiFePO₄ under high C‐rate conditions. The present model was validated with experimental data and showed good agreement. Copyright © 2016 John Wiley & Sons, Ltd.     

Study on electrochemical and thermal characteristics of lithium‐ion battery using the electrochemical‐thermal coupled model

The higher specific energy leads to more heat generation of a battery, which affects the performance and cycle life of a battery and even results in some security problems. In this paper, the capacity calibration, Hybrid Pulse Power Characteristic (HPPC), constant current (dis)charging, and entropy heat coefficient tests of chosen 11‐Ah lithium‐ion batteries are carried out. The entropy heat coefficient increases firstly and then decreases with the increase of the depth of discharge (DOD) and reaches the maximum value near 50% DOD. An electrochemical‐thermal coupled model of the chosen battery is established and then verified by the tests. The simulation voltage and temperature trends are in agreement with the test results. The maximum voltage and temperature error is within 2.06% and 0.4°C, respectively. Based on the established model, the effects of adjustable parameters on electrochemical characteristic are systematically studied. Results show that the average current density, the thickness of the positive electrode, the initial and maximum lithium concentration of the positive electrode, and the radius of the positive electrode particle have great influence on battery capacity and voltage. In addition, the influence degree of the internal resistance of the solid electrolyte interface (SEI) layer, the thickness of negative electrode, and the initial and maximum lithium concentration of the negative electrode on the capacity and voltage is associated with certain constraints. Meanwhile, the influences of adjustable parameters related to thermal characteristic are also systematically analyzed. Results show that the average current density, the convective heat transfer coefficient, the thickness, and the maximum lithium concentration of the positive electrode have great influence on the temperature rise. Besides, the uniformity of the temperature distribution deteriorates with the increase of the convective heat transfer coefficient.     

Thermal simulation of high‐power Li‐ion battery with LiMn1/3Ni1/3Co1/3O2 cathode on cell and module levels

Thermal modeling of temperature rise in high‐power Li‐ion battery cells and modules is presented here. Simulation results are validated by experiments. Results indicate that entropy heat generation plays a significant role in heat generation of Li‐ion battery cells and should be included in simulation as a function of state of charge (SOC). Simulation results utilizing measured overpotential resistance and entropy heat generation provide the best fit when compared to experimental results. Resistance data provided by supplier shows significant difference compared with measured data and should be critically examined for any module design purposes. Copyright © 2013 John Wiley & Sons, Ltd.     

Degradation of LiCoO2 in aqueous lithium–air batteries

The degradation behaviour of aqueous rechargeable lithium cobalt oxide–air batteries in 5 M LiNO₃ aqueous solution is observed by electrochemical characterizations. At lower scan rates of cyclic voltammetry, the three pairs of redox peaks at E _SCE = 0.79/0.67, 0.89/0.85 and 1.15/0.97 V are proven to produce good reversibility. The small separation of the peaks is proportionally consistent with the Li⁺ diffusion coefficients of 2.82 × 10^?7 cm² s^?1 (anodic) and 1.76 × 10^?7 cm² s^?1 (cathodic). The lithium cobalt oxide–air batteries have a higher initial specific discharge capacity of 114.35 mA h g^?1, which fades to 83% (after the first 10 cycles) and 52% (after 50 cycles). As the specific discharge capacity decreases, the resistance increases. The dissolution of Li⁺ is mainly attributed to these degradations. Further analyses of the batteries' degradation are performed by morphological and structural characterizations of the cathode material. Copyright © 2016 John Wiley & Sons, Ltd.     

Study on CuO–CeO2/SiC catalysts in the sulfur–iodine cycle for hydrogen production

The structure and activity of ceria–copper oxides supported on nanometer silicon carbide (nano‐SiC) particles for sulfuric acid decomposition were studied. The promoting activities and stabilities of CuO–CeO₂ complex oxides loaded on nano‐SiC grains were prominently higher than those of CuO–CeO₂ without carriers, especially at <800 °C. The results of X‐ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM) showed that copper‐cerium composite oxides grains were well dispersed and fixed on the surface of SiC particle, and the average sizes of CuO–CeO₂ complex oxides carried by SiC particles were considerably smaller than those of CuO–CeO₂ without carriers. Based on the analysis of HRTEM images, X‐ray photoelectron spectroscopy (XPS) spectra, and infrared radiation (IR) pattern, the majority of SiC surfaces were converted to SiO₂ layers, in which CeO₂ grains immobilized by coordination bonding Ce–O–Si bridges. From the temperature programmed reduction (TPR) patterns, compared with those of CuO–CeO₂ without carrier, the reduction temperature of CuO to Cu₂O in CuO–CeO₂/SiC catalysts was lowered, especially at (Ce + Cu)/SiC atomic ratio of 5 mol.%. The catalysts also showed relatively high activities at 727 °C for 20 h of continuous operation. A mechanism of SO₃ decomposition on CuO–CeO₂/SiC was proposed according to the characterization results. Copyright © 2016 John Wiley & Sons, Ltd.