Electrodeposited Ni–Sn intermetallic electrodes for advanced lithium ion batteries

Various samples of Ni_xSn_y metallic alloys electrodeposited under different current and time regimes have been prepared and tested in lithium cells. The results clearly demonstrate that the electrochemical performance of these intermetallic electrodes greatly depends on the synthesis conditions which in turn reflect on the type of morphology and phase of the various samples. The best electrode cycled with a high capacity delivery, i.e. of the order of 550 mA hg⁻¹ and showed an efficient behaviour when used as anode in a lithium ion battery using LiNi_0.5Mn_1.5O₄ as cathode. These results confirm that the electrodeposition is a very promising synthesis tool for monitoring the morphological and phase conditions of Ni_xSn_y and that the approach described in this work may be used for further optimizing this intermetallic electrode.     

Preparation and characterization of positive electrode of Ni–MH batteries with cobalt additives

The present paper shows the preparation and characterization of alkaline batteries cathodes formed by nickel hydroxide with the addition of cobalt. This additive was incorporated by two methods: on the electrode surface, using the electroless technique and by direct incorporation of cobalt powder in the active material. The electrochemical behavior of both nickel hydroxide electrodes was investigated and compared. The results indicate that active materials containing cobalt additive by the electroless technique exhibit an improvement on the electrochemical performance.     

Hydrogen evolution reaction on amorphous Ni–S–Co alloy in alkaline medium

Using an orthogonal design, i.e. the CoCl₂ concentration, the current density, the temperature and the pH value as the factors, Ni–S–Co alloy was obtained through electrodeposition in a modified Watts bath by adding thiourea (TU) and CoCl₂ into the bath. The structure and morphology were determined by XRD and SEM. The electrochemical properties, including the hydrogen evolution overvoltages η (h.o.v.), the Tafel slope b, the exchange current density i⁰ and the activation energy ΔH^* of amorphous Ni–S–Co cathode were measured. The effect of heat treatment under various temperatures on its structure and electrochemical properties were determined. The results indicate that the structure of Ni–S–Co alloy obtained under the optimum conditions is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni–S electrode due to the higher sulfur content in such electrode, and heat treatment is harmful to its electrochemical activity.     

Synthesis of γ-CoOOH and its effects on the positive electrodes of nickel batteries

High-valence (3.40) cobalt compounds were synthesized by a chemical precipitation (CP) method. Nickel hydroxide electrodes were then prepared using the synthesized compounds as conducting agents. The effects of high-valence cobalt additions on electrode properties, such as charge–discharge characteristics, electrode reaction reversibility, and cyclic voltammetric performance, were investigated by cyclic voltammetry, X-ray diffraction (XRD), and resistance measurement. The results demonstrate that the addition of high-valence cobalt helps to form a conductive network in the electrode, thus greatly increasing the cycling performance and simultaneously accomplishing an extremely high utilization of the active material in the positive electrode. For comparison, active materials of Co(OH)₂, β-CoOOH, and CoO were also included in the test. It was found that cobalt with a valence of 3.40 has a higher performance within one cycle. The utilization of the active material can reach 100.6% at a discharge rate of 0.2 C.     

Investigation on electronically conductive additives to improve positive active material utilization in lead-acid batteries

In order to adapt lead-acid batteries for use in hybrid electric vehicles, its specific energy must be improved. Specific energy is greatly dependant on active material utilization. In this study, we improve active material utilization in positive electrodes by the addition of electronically conductive additives. Titanium silicide particles (<44 μm diameter), titanium dioxide fibers (<10 μm, diameter), and titanium wire (76 μm, diameter) were incorporated into the positive electrode and each of their effects on discharge capacity and utilization of active material were examined. The percent mass of each additive was varied from 2–5%. Results indicate that titanium wire at 2.3 wt.% had the optimal effect of increasing the utilization by 12.3% (57 to 64% utilization) relative to control with no additive at a slow discharge rate (10 mA cm⁻²) without detrimental effect at fast discharge rate (50 mA cm⁻²). This additive also features reduction in weight and formation enhancement.     

Increase of positive active material utilization in lead-acid batteries using diatomaceous earth additives

In this study we examined the use of diatomites to improve the discharge capacity and utilization of the positive electrode of the lead-acid battery. A large fraction of the positive electrode performance of this battery system (half-reaction shown below) is based on the ionic conduction of sulfuric acid through the plate.

PbO₂(s) + HSO₄⁻ + 3H⁺ + 2e⁻ → PbSO₄(s) + 2H₂O

Activation behaviour of the Ni/MH batteries electrodic material Ni(OH)2 by single particle microelectrode technique

The activation process of Ni(OH)₂ used as the positive electrode active material of Ni/MH batteries was studied by a single particle microelectrode method thanks to an improved apparatus. The images of the Ni(OH)₂ particle during the charge process were collected. The electrochemical properties of Ni(OH)₂ were studied by cyclic voltammetry and galvanostatic charge/discharge of a single particle. The charge efficiency (η) of the single particle was as high as 94%. The normalized output rate (NOR) was proposed as a parameter to evaluate the output performance of the electrode material. The NOR value varied with the electrode potential value. But the NOR value remained constant at fixed electrode potential value during the activation process. This implies that the activation process did not improve the reaction rate of the particle, although the capacity kept increasing during the activation process. The intrinsic nature of the activation of Ni(OH)₂ was deduced as the formation of dispersed Ni(III) in the active mass. The Ni(III) phase was formed during the charge process and some remained unreduced during the discharge process. The remaining Ni(III) resulted in a much higher electronic conductivity of Ni(OH)₂.     

Prospects,challenges, and latest developments in lithium–air batteries

Metal–air batteries are being envisioned as a clean and high energy fuel for the modern automotive industry. The lithium–air battery has been found most promising among the various practically applicable metal–air systems, that is, Al–air, Li–air, Mg–air, Fe–air, and Zn–air. The theoretical specific energy of the Li–air battery is ~12 kWh/kg, excluding the oxygen mass. This is comparable with the energy density of gasoline, which is ~13 kWh/kg. It has been hypothesized that the Li–air battery could supply an energy ~1.7 kWh/kg after losses from over potentials to run a vehicle ~300 miles on a single charge. During the first decade of this century, a fair amount of research has been conducted on Li–air battery system. Yet, Li–air batteries could not make an industrial breakthrough, and are still in the laboratory phase since their birth. In this article, we technically evaluated the recent developments, and the inferences have been analyzed from the practical/commercial point of view. The study concludes that low discharge rate, lower number of cycles, oxidation of lithium anode, discharge products at the cathode, and side reactions inside the battery are the key limiting factors in the slow progress of Li–air batteries on an industrial scale. The ongoing researches to overcome these hurdles have also been discussed. This analysis will help the reader to understand the current standing of the lithium–air battery technology. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Differences in the effects of Co and CoO on the performance of Ni(OH)2 electrode in Ni/MH power battery

The effects of metallic cobalt (Co) and cobalt monoxide (CoO), as additives in positive electrodes, on the electrochemical performance of nickel/metal hydride (Ni/MH) power batteries are studied. Commercial Co and CoO are charged at 50 °C in 6 M KOH solution. The oxidation mechanism of cobalt materials is investigated by observing structural and morphological evolutions during charging. A pure Co₃O₄-type phase is formed when the starting material is CoO. When Co is used, a cobalt oxyhydroxide (CoOOH) phase is present, together with a tricobalt tetroxide (Co₃O₄) phase. In both cases, the cobalt concentration in the electrolyte decreases during oxidation. The final product is dependent on the solubility of cobalt and the kinetics of the reaction that consumes cobalt tetrahydroxide [Co(OH)₄]²⁻. The highly compact CoOOH phase, which works well between the nickel foam frame and nickel hydroxide [Ni(OH)₂] particles, enhances the power performance of Ni/MH power battery. The Co₃O₄ phase, which works well in connecting Ni(OH)₂ particles, improves the capacitive performance of Ni/MH power battery.     

Influence of carbons on the structure of the negative active material of lead-acid batteries and on battery performance

It has been established that addition of carbon additives to the lead negative active material (NAM) of lead-acid batteries increase battery charge acceptance in hybrid electric vehicle mode of operation. The present work studies three types of activated carbons and two types of carbon blacks with the aim to evaluate their efficiency in improving the charge acceptance of lead-acid batteries. It has been established that the size of carbon particles and their affinity to lead are essential. If carbon particles are of nanosizes, they are incorporated into the bulk of the skeleton branches of NAM and may thus increase the latter's ohmic resistance. Their content in NAM should not exceed 0.2-0.5 wt.%. At this loading level, carbon grains are adsorbed only on the surface of NAM contributing to the increase of its specific surface area and thus improving its charge acceptance. When carbon particles are of micron sizes and have high affinity to lead, they are integrated into the skeleton structure of NAM as a structural component and act as super-capacitors, i.e. electric charges are concentrated in them and then the current is distributed along the adjacent branches of the lead skeleton with the lowest ohmic resistance. This eventually improves the charge acceptance of the negative battery plates.     

Co(OH)2 nanoparticles deposited on reduced graphene oxide nanoflake as a suitable electrode material for supercapacitor and oxygen evolution reaction in alkaline media

In this work, cobalt hydroxide nanoparticles are simply synthesized (size is about 50 nm) and deposited on the reduced graphene oxide nanoflake by the hydrothermal method. Then, the ability of glassy carbon electrode modified with this low-cost nanocomposite is examined as a supercapacitor and oxygen evolution electrocatalysts in 2.0 mol L^?1 KOH by a three-electrode system. The modified electrode as a pseudocapacitor with potential windows of 0.35 V, exhibits a powerful specific capacitance (235.20 F g^?1 at 0.1 A g^?1 current density), energy density, stability (about 90% of the initial capacitance value maintain after 2000 cycles at 1.0 A g^?1) and fast charge/discharge ability. Furthermore, the modified electrode displays a good electrocatalytic activity for oxygen evolution reaction with a current density of 10.0 mA cm^?2 at 1.647 V, small Tafel slope of 56.5 mV dec^?1, good onset potential of 1.521 V vs. RHE and suitable durability.     

Effect and function mechanism of amorphous sulfur on the electrochemical properties of cobalt hydroxide electrode

S-Co(OH)₂ composite is prepared via a facile co-precipitation method and investigated as negative electrode of Ni/Co battery. The addition of amorphous S improves the electrochemical properties of Co(OH)₂ electrode. The discharge capacity of S-Co(OH)₂ electrode can reach 413.2 mAh g⁻¹ and still keep about 340 mAh g⁻¹ after 300 cycles, which is much higher than that of S-free Co(OH)₂ electrode. Amorphous S in S-Co(OH)₂ electrode shows two functions during the charge-discharge process. One is that the addition of amorphous S with high specific surface area improves the dispersion of Co(OH)₂ platelets. The other is that the dissolution of amorphous S in electrode brings the new interspaces among the Co(OH)₂ platelets, these two factors largely increase the interspaces among Co(OH)₂ platelets. More interspaces are correlated to larger contact area with alkaline solution, which is in favor of the surface electrochemical redox. Thus, the capacity utilization of Co(OH)₂ is enhanced.     

Influence of carbon microstructure on the Li–O2 battery first‐discharge kinetics

Defects in the carbon microstructure have been reported to enhance the discharge performance of Li–O₂ battery. However, systematic studies correlating the presence of defects with the discharge kinetics have not addressed the variation of carbon electrode surface areas. In this work, carbon blacks and carbon nanofibers with different defect densities were investigated for their discharge properties. The electrolyte‐accessible areas of the carbon electrodes were obtained from Cyclic voltammetry measurements. The microstructure and surface areas of the carbons were characterized by Raman spectroscopy, electron microscopy, and N₂ isotherm. Linear sweep voltammetry and galvanostatic discharge experiments consistently demonstrated that graphitic carbons have more negative onset potentials and more negative discharge potentials at the same current density than defective carbons. The linear sweep voltammetry data were normalized to the carbon masses, Brunauer–Emmet–Teller surface areas, and double layer capacitance‐derived areas for comparison. Plot of inverse charge transfer resistance and double layer capacitance from electrochemical impedance spectroscopy measurements were used to extract current density values without knowledge of electrode areas. The current densities from impedance measurements exhibited good agreement with the data from linear sweep experiments. The electrochemical experiments conclusively showed that defects on the graphitic microstructure increase the discharge kinetics of the Li–O₂ battery. Copyright © 2016 John Wiley & Sons, Ltd.     

Study of the electro-oxidation of CoO and Co(OH)2 at 90 °C in alkaline medium

Cobalt is usually post-added as CoO or Co(OH)₂ to nickel hydroxide at the positive electrode (nickel oxide electrode) of alkaline batteries, to form a conductive network. In the present work, we focus on the transformation of CoO and Co(OH)₂ phases when oxidized at 90 °C. The Co₃O₄ phase is the majority product of such a reaction, with CoOOH as a secondary product. It is shown that the Co₃O₄ phase results from the reaction of the CoOOH phase, formed by electrochemical oxidation of Co(OH)₂, with Co²⁺ species in the electrolyte, which is made possible by temperature. This process requires a global migration of the cobalt phases towards the current collector.     

The effect of internal resistance on dendritic growth on lithium metal electrodes in the lithium secondary batteries

In a lithium secondary battery, the effect of the current rate affect on dendritic growth has been established. In the present, a series of experiments was conducted at a constant current rate, but at various the cell internal resistances. Different temperatures at −5 °C, 15 °C, and 35 °C were applied to change the internal resistance. The present experiment found that as the resistance was varied, the voltage gradient also varied and accordingly to maintain a constant current rate, and that the Sand's time was measured differently at such varying voltage gradients. That voltage was also decreased together with the resistance to apply a constant current density results from Ohm's law. It was found that even if the current density remains constant, the size of the area where dendrites are generated will vary in accordance with the theory of solidification.     

The cobalt content effect on the electrochemical behavior of nickel hydroxide electrodes

In this paper, the study of nickel hydroxide porous electrodes containing different concentrations of cobalt as additive (2–10%), polytetrafluoroethylene (PTFE) as binder material and prepared by chemical impregnation on nickel sintered substrate, are presented. The characterization of the different electrodes is performed using optical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrochemical techniques as cyclic voltammetry, charge-discharge curves and electrochemical impedance spectroscopy (EIS). The results indicate that the concentration of 5% metallic Co improves the electrochemical behavior of the active material.     

Computational study about the effect of electrode morphology on the performance of lithium‐ion batteries

Electrode morphology has significant influence on the performance of lithium‐ion batteries in that it controls electrical conductivity and electrode utilization by establishing electrical connectivity in the electrode. The present study investigates the effect of the electrode morphology on battery performance by combining two different mathematical models. First, a two‐dimensional, direct numerical simulation (DNS) model is introduced, which stochastically generates electrode morphology and calculates electrical conduction and electrode utilization. Various simulations are conducted to evaluate the effect of the active particle coating, conductive agent loading, particle size, and electrode compression by using the DNS model. Second, data acquired from the DNS model are applied to the blended‐electrode model to evaluate battery performance. Calculation result confirms that electrode morphologies have significant effects on both capacity and power of lithium‐ion batteries. Copyright © 2016 John Wiley & Sons, Ltd.     

Nickel volatilization phenomenon on the Ni-CGO anode in a cathode-supported SOFC operated at low concentrations of H2

Rapid degradation phenomenon is generally occurred when Ni-based anode on a cathode-supported SOFC is operated in low concentrations of hydrogen at high current density. In order to clarify this phenomenon, homogenous NiO-Ce_0.8Gd_0.2O_1.9 (CGO) composites powder with fixed weight ratio of Ni:Ce was synthesized using a nitric-citrate sol-gel method, and coated on LSM-CGO cathode-supported SOFC using slurry coating method. As-prepared fuel cells exhibited good performance when they were operated at pure H₂. However, rapid degradation phenomenon on Ni-CGO anode usually happened when low concentration of H₂ was used as fuel at high current density. Obvious microstructure damage and sintering of Ni were observed in SEM micrographs of Ni-CGO anode after repeated degradation process in 5.66% of H₂ at high current density. Furthermore, the decrease in Ni amount in Ni-CGO anode was also found via EDX analysis when this degradation process was repeated for several times. It is inferred that the volatilization of nickel hydroxide should happen at triple-phase boundaries of Ni-CGO anode when high partial pressure ratio of H₂O and H₂ appeared in this case.