Studies on electrochemical performance of partially reduced MnO2 used as cathode for MH–MnO2 rechargeable battery

Cyclic voltammograms show that the reversibility of the manganese dioxide (MnO₂) electrode is improved by means of using partially reduced samples. The crystal lattice of the intermediate is transformed by reduction. Formation of the manganous ion is very limited before the electrode potential reaches −0.4 V (versus Hg/HgO), thus the formation of Mn₃O₄ is prevented.The addition of Ni(OH)₂ to partially reduced samples can further improve the reversibility of the MnO₂ electrode, Ni(OH)₂ delays the 2e⁻ discharge step and decreases the opportunity for the co-existence of Mn(III) and Mn(II) ions and, thereby, prevents the formation of Mn₃O₄. The capacity retention of a cathode of partially reduced MnO₂ (pr-MnO₂) or pr-MnO₂+Ni(OH)₂ is much better than that of the MnO₂ cathode. This demonstrates the feasibility of using pr-MnO₂ as a cathode material.     

Fabrication and characteristics of a composite cathode of sulfonated polyaniline and Ramsdellite–MnO2 for a new rechargeable lithium polymer battery

The ionic conductivity of a polyacrylonitrile (PAN)-based solid polymer electrolyte is 1.4×10⁻³ S cm⁻¹, which is sufficient for the electrolyte to be used in a rechargeable lithium polymer battery. The anodic stability of the solid polymer electrolyte is over 4.6 V (vs. Li/Li⁺). A reduced, highly sulfonated form of polyaniline (SPAn) and Ramsdellite–MnO₂ (R-MnO₂) are synthesized and used as a cathodic material for a rechargeable lithium polymer battery. Three kinds of cathodes are prepared from SPAn, R-MnO₂, and a mixture of SPAn and R-MnO₂. The electrochemical properties and diffusion coefficient of lithium ions in each cathode, and the interface between the solid polymer electrolyte and each cathode are investigated by cyclic voltammetry and impedance spectroscopy. The redox processes of the SPAn cathode are two-step reactions. The cathodic and anodic peak currents increase as the cycle number increases. In the redox processes of the R-MnO₂ cathode, the cathodic peak current on the second cycle is 62% of that on the first cycle. The Li/R-MnO₂ battery has a very high initial discharge capacity, but very poor cycleability. For the composite cathode, the cathodic peak current on the second cycle is 72% of that on the first cycle, i.e., higher than that for the R-MnO₂ cathode. The diffusion coefficient of the composite cathode during the discharge process is close to the sum of each variation in the SPAn and R-MnO₂ cathodes. The instability of the R-MnO₂ cathode at x=0.3 and x=0.2 during the charge process is not observed with the composite cathode. The discharge–charge performance of three types of battery are investigated. The initial discharge capacity of the Li/composite cathode battery is 97.0 m Ah g⁻¹. This battery has higher discharge capacity than the Li/SPAn battery (66.8 m Ah g⁻¹), and better cycleability than the Li/R-MnO₂ battery.     

Alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte for Zn–air battery

An alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte with high ionic conductivity (10⁻² S cm⁻¹) at room temperature has been prepared and applied to solid-state primary Zn–air batteries. The electrolyte shows excellent mechanical strength. The electrochemical characteristics of the batteries were experimentally investigated by means of ac impedance spectroscopy and galvanostatic discharge. The results indicate that the PEO–PVA–glass-fibre-mat composite polymer electrolyte is a promising candidate for application in alkaline primary Zn–air batteries.     

Optimisation of real-time control for hybrid diesel–PV–battery systems

Hybrid diesel–PV–battery systems are one of the most cost effective options for off-grid power generation. A methodology for the optimal operation of such systems for an off-grid application is proposed in this paper. The methodology is based on the minimisation of an energy cost function. Based on this function, an optimal operating point for the diesel generator is identified, taking into account the characteristics of the diesel generator, battery bank and converter as well as the costs of fuel and battery usage. The operation of the diesel generator at this optimum operating point results in an overall energy cost reduction for the hybrid diesel–battery system. Simulation analysis shows that the proposed control strategy can achieve up to 4% reduction in the levelised cost of energy. This is mostly due to the savings made from the efficient usage of diesel generator and battery.     

Evaluation of criteria for design of current collectors of the lead–acid battery

The effect of the main structural parameters of the current collectors on efficiency of operation of the positive electrode of the lead–acid battery was investigated.     

Tuning of electrocatalytic activity of Mn–O–Co composite for alkaline hydrogen evolution reaction

We report the enhancement in electrocatalytic activity of Mn–O–Co composite electrode developed through chemical reduction method. The Mn–O–Co composite electrode exhibits high catalytic activity with a low Tafel slope of 123 mV dec⁻¹ and a low overpotential of 117 mV at a current density of 10 mA cm⁻². The enhancement in electrocatalytic activity of Mn–O–Co composite electrode is due to the synergistic activity of MnO and CoO with the NiP matrix. The intermetallic interaction among the half-filled orbitals of manganese with the fully occupied orbitals of cobalt and nickel leads to an effective electron delocalization in the catalytic system which enhances the HER performance of the coating. The C_dl value of the composite electrode is in the order of 254 μF, which is approximately ten fold higher than the bare NiP coating, due to the enhancement in interaction between the Mn–O–Co composite electrode and the reactive species in the HER medium. The Mn–O–Co composite electrode shows promising characteristics as an electrocatalyst with long term stability and remarkable competency with the commercially available electrodes.     

Relationship between the total energy efficiency of a sodium–sulfur battery system and the heat dissipation of the battery case

The relationship between the total energy efficiency of an Na/S battery system and the heat dissipation through its battery case, was investigated. The total energy efficiency was heavily influenced by the heat dissipation of the battery case, and little influenced by the energy efficiency of its cells. In order to obtain a higher total energy efficiency, it is essential to design the battery case with less heat dissipation.     

Noble fabrication of Ni–Mo cathode for alkaline water electrolysis and alkaline polymer electrolyte water electrolysis

Among the catalysts for hydrogen evolution reaction (HER) in alkaline media, Ni–Mo turns out to be the most active one. Conventional preparations of Ni–Mo electrode involve repeated spraying of dilute solutions of precursors onto the electrode substrate, which is time-consuming and usually results in cracking and brittle electrodes. Here we report a noble fabrication of Ni–Mo electrode for HER. NiMoO₄ powder was synthesized and used as the precursor. After reduction in H₂ at 500 °C, the NiMoO₄ powder layer was converted to a uniform and robust electrode containing metallic Ni and amorphous Mo(IV) oxides. The distribution of Ni and Mo components in this electrode is naturally uniform, which can maximize the interaction between Ni and Mo and benefit the electrocatalysis. The thus-obtained Ni–Mo electrode exhibits a very high catalytic activity toward the HER: the current density reaches 700 mA/cm² at 150 mV overpotential in 5 M KOH solution at 70 °C. This new fabrication method of Ni–Mo electrode is not only suitable for alkaline water electrolysis (AWE), but also applicable to the alkaline polymer electrolyte water electrolysis (APEWE), an emerging technique for efficient production of H₂.     

Mechanically alloyed Mg2Ni for metal-hydride–air secondary battery

Mechanically alloyed Mg₂Ni and a single air (oxygen) electrode are used as the anode and cathode, respectively, in a Mg₂Ni|6 M KOH|O₂ rechargeable metal-hydride–air (MH–air) battery. The battery is tested for self-discharge by measuring the open-circuit voltage (OCV) and cycling characteristics. Battery degradation after charge–discharge cycling is characterized by means of X-ray diffraction (XRD) and scanning electron microscopic (SEM) analyses.     

Nanosized Zn–Sn metal composite oxide: a new anode material for Li ion battery

Abstract

The morphological evolution of nanosized Zn–Sn composite oxides, synthesised by the decomposition of ZnSn(OH)₆ precursor at temperature ranged from 300 to 800°C was investigated by using XRD and high resolution TEM. The precursor was also studied by thermal analysis. The electrochemical performance of Zn–Sn composite oxides as anode materials for Li ion batteries was measured in the form of Li/Zn–Sn composite oxides cells. The results reveal that the samples calcined at low temperatures (300 and 500°C) were amorphous Zn₂SnO₄ and SnO₂, and the samples calcined at high temperatures (720 and 800°C) were crystal Zn₂SnO₄ and SnO₂. All the samples have a high reversible specific capacity of over 800 mAh g^?1, and the first charge specific capacity is up to 903 mAh g^?1 for the sample calcined at 500°C. The charge capacity and cyclability were sensitive to the structure and composition of the electrode active materials; the samples calcined at phase transition temperature rage exhibited relatively worse electrochemical properties.     

Polydivinylferrocene surface modified electrode for measuring state-of-charge of lead–acid battery

This paper outlines an investigation of the electrochemical behaviour of polymeric divinylferrocene (PDVF) produced by direct polymerisation of divinylferrocene (DVF) monomer on a glassy carbon substrate. The findings indicate that PDVF undergoes reversible reduction/oxidation in neutral and acidic aqueous media containing perchlorate (ClO₄⁻) and sulfhate (SO₄²⁻). The anodic peak potential of the PDVF shifts linearly to less positive potentials as the sulfuric acid (H₂SO₄) concentration is increased from 1 to 5 M. The polymer film strongly adheres to the glassy carbon surface and is electrochemically stable when subjected to repeated voltammetric cycling in the potential range of −0.2 to +0.8 V vs. Ag|AgCl. The potential of the partially oxidized film of PVDF on a glassy carbon substrate against a Ag|AgCl/KCl reference electrode in sulfuric acid solution is stable, reproducible and varies linearly with the acid concentration in the range of 1–5 M. This observation may be suitable for potentiometrically measuring the state-of-charge of lead–acid batteries.     

Study on optimal configuration of the grid-connected wind–solar–battery hybrid power system

The capacity allocation of each energy unit in the grid-connected wind–solar–battery hybrid power system is a significant segment in system design. In this paper, taking power grid dispatching into account, the research priorities are as follows: (1) We establish the mathematic models of each energy unit in the hybrid power system. (2) Based on dispatching of the power grid, energy surplus rate, system energy volatility and total cost, we establish the evaluation system for the wind–solar–battery power system and use a number of different devices as the constraint condition. (3) Based on an improved Genetic algorithm, we put forward a multi-objective optimisation algorithm to solve the optimal configuration problem in the hybrid power system, so we can achieve the high efficiency and economy of the grid-connected hybrid power system. The simulation result shows that the grid-connected wind–solar–battery hybrid power system has a higher comprehensive performance; the method of optimal configuration in this paper is useful and reasonable.     

Synergistic effect of organic-inorganic hybrid electrolyte for ultra-long Zn–I2 batteries

Hydrogel electrolytes are widely used in wearable aqueous zinc-ion batteries (ZIBs) which are considered as the most promising candidate for future energy storage systems. However, traditional organic hydrogel ions have the disadvantages of low ionic conductivity and poor mechanical properties. To conquer this, an organic-inorganic hybrid hydrogel electrolyte (PVA/CNC–C/sepiolite) is developed to improve ionic conductivity and reduce side reactions in ZIBs simultaneously. In this system, hydrogen bonds are formed between sulfonic acid groups in the polymer and the hydroxyl groups in sepiolite. The existence of these hydrogen bonds enhances the binding force between the organic and inorganic components, thus improving the ionic conductivity and mechanical properties of the electrolyte. Also, sulfonic acid groups in this hydrogel electrolyte can induce homogeneous deposition of Zn²⁺. The pores between the multilayer structures in sepiolite further optimize the ion transport channel and improve the transfer kinetics of Zn²⁺. Due to the synergistic effect of organic-inorganic compositions in this electrolyte, the Zn/Zn cell operates for more than 2000 h and Zn/I₂ cell full exhibits an ultra-stable lifespan for 10,000 cycles. This work opens up a new avenue for the design of hydrogel electrolytes in ZIBs.     

Synergistic effects in an AB5–Co material as an anode for a secondary alkaline battery

The AB₅ alloy and Co powders have been mixed at various weight ratios to form AB₅–Co composite electrodes. The discharge properties such as discharge capacity, discharge plateau, and cycling stability are investigated by charge and discharge testing using Arbin battery testing equipment. Synergistic effects in the composite electrodes contribute to significant improvements of the discharge behavior. For instance, the composite AB₅–25%Co electrode shows a high discharge capacity of 395.1 mAh/g, which is significantly higher than that of AB₅ or Co electrode, and good cycling stability. The discharge process is also characterized by electrochemical impedance spectroscopy. Moreover, the electrochemical discharge mechanism is discussed.     

Reproduction of Li battery LiNixMnyCo1−x−yO2 positive electrode material from the recycling of waste battery

In this study, Co, Li and Ni were acquired from waste battery to remake positive electrode material of Li battery, then the battery was assembled and battery charging and discharging was conducted. By doing so, the waste can be turned into resource, and pollution issue to the environment from the battery can be reduced and manufacturing cost of the battery can be reduced too. Presently, the recycling treatment of waste Li battery was to adopt wet metallurgical method to separate Li, Co, Ni and Mn elements and to prepare respectively all kinds of pure oxide or carbonate, therefore, the process was very tedious, and the economic efficiency was not as expected. In this study, Co, Li and Ni were acquired from waste battery to make Li, Ni, Mn, Co ternary material positive electrode powder. In the process, Li, Ni, Mn and Co proportion in the solution was analyzed, and insufficient metallic ion composition was then added. After it was adjusted to correct composition, it was sintered into positive electrode material powder. Therefore, element separation procedure can be saved, and the cost can be greatly reduced. In this study, waste battery was used to remake positive electrode material, and SEM and XRD were used first to observe micro structure, then it was assembled into battery. After battery charging and discharging performance test, it can reach 122.21 mA h/g, which was about 88% of that made by pure material. Consequently, the purposes of low manufacturing cost of positive electrode material, the recycling of valuable Co material from the waste battery, the reduction of waste material and the turning of waste into resource can be reached.     

Charge–discharge properties of surface-modified carbon by resin coating in Li-ion battery

The effect of an epoxy resin coating on the electrochemical performance of Li-ion batteries is investigated. Mesocarbon microbeads (MCMB), which constitute a promising carbon anode material for rechargeable Li-ion batteries is used as a starting carbon material. The surface coating of the MCMB is carried out by refluxing in a dilute H₂SO₄ solution and mixing in the epoxy resin-dissolved tetrahydrofuran (THF) solution. After heat treatment at 1000–1300 °C, the resin coating layer on the MCMB is converted to an amorphous phase which is identified by means of a high resolution transmission electron microscope (HRTEM) and a electron energy loss spectroscopy (EELS) analyses. The Brunauer–Emmett–Teller (BET) surface area of MCMB is increased by the formation of the amorphous epoxy resin coating layer. The electrochemical performance of the MCMB, such as the charge–discharge capacity and cycleability, is enhanced by the surface modification through epoxy resin coating. The reasons for the improvement of electrochemical performance are discussed in terms of the results from HRTEM observation, EELS analysis, and cyclicvoltammetry     

Fabrication of dc–dc converter using nanocrystalline Mn–Zn ferrites

Abstract

The microwave–hydrothermal method has been successfully used for synthesis of nanocrystalline Mn–Zn ferrites which are used for high frequency applications. The nanopowders were characterised using X-ray diffraction and TEM. The nanopowders were annealed using microwaves at 600°C/10 min. The frequency dependence of dielectric constant ?′ was measured in the range from 10 Hz to 1·3 GHz, and initial permeability μ _i was measured in the range from 10 Hz to 1 MHz. The total power loss was measured at 100 kHz and 200 mT on the annealed samples. Conductor embedded ferrite transformers were fabricated, and output power P _o, efficiency η and temperature increase ΔT were measured at sinusoidal voltage of 25 V with frequency 1 MHz. The transformer efficiency η was found to be high, and surface rise of temperature ΔT is very low.     

The electrochemical behavior of Ni–MH battery,Ni(OH)2 electrode and metal hydride electrode

In the past years, the nickel–metal hydride rechargeable battery is already been widely used in many application fields, and is now replacing the nickel–cadmium battery. Electrochemical impedance spectroscopy technique is extensively used to reveal the electrode process kinetics, for example, Pb–H₂SO₄ battery, Ni–Cd battery. There are few reports on the EIS of Ni–MH battery. In this paper, an extensive study is focused on the electrochemical impedance spectroscopy of metal hydride electrode, β–Ni(OH)₂ electrode and Ni–MH battery with different states of charge.     

Microstructure and electrochemical properties of Zr–Ti–V–Ni–Mn–LM alloys for application in Ni–MH secondary battery

A series of multi-component Zr_1−xTi_xV_0.4Ni_1.2Mn_0.4LM_y (x=0.3, 0.4; y=0.0,0.02,0.05,0.1,0.2,0.3, LM; lantanum-rich-mischmetal) alloys are prepared and their crystal structure and P–C–T curves are analyzed. The alloys have been modified by adding LM and their gaseous and electrochemical hydrogenation properties are studied to find out the effect of LM elements. Also, the second phase and initial activation performance are investigated. The Zr_1−xTi_xV_0.4Ni_1.2Mn_0.4LM_y (x=0.3,0.4; y=0.0,0.02,0.05,0.1,0.2,0.3) alloys have C14 Laves phase hexagonal structure, so the volume expansion ratio of lattice parameters with LM has increased. As the amount of LM in alloy has increased, correspondingly the second phase is also increased. The second phase is LM, Ti and V-rich. The second phase improve the activation of La-rich misch-metal, and also the concentration of elements Ti, V〉LM〉 matrix in alloys.The addition of LM in Zr_1−xTi_xV_0.4Ni_1.2Mn_0.4LM_y (x=0.3, 0.4) alloys have increased the activation rate and hydrogen storage capacity significantly, but the plateau pressure and the discharge capacity have been decreased due to the formation of second phase. For more Zr in electrode alloys, the activation of rate becomes slow.     

Ni–Zn nanosheet anchored on rGO as bifunctional electrocatalyst for efficient alkaline water-to-hydrogen conversion via hydrazine electrolysis

Bifunctional Ni-15 at.% Zn/rGO catalyst was fabricated by a two-step electrodeposition to be used for efficient alkaline water-to-hydrogen conversion via hydrazine electrolysis. Experiments show that the as-deposited Ni-15 at.% Zn/rGO nanosheet arrays with porous structure possesses excellent catalytic activity and stability towards both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). A small overpotential of 49 mV at 10 mA cm⁻² with a low Tafel slope of 26.3 mV dec⁻¹, and a retention rate of 91.4% after 12 h at 10 mA cm⁻² are observed for Ni-15 at.% Zn/rGO towards HER. Moreover, Ni-15 at.% Zn/rGO also shows an extra-high current density of 1097 mA cm⁻² at 0.6 V vs RHE with a low Tafel slope of 33.5 mV dec⁻¹, and a high durability of 90.5% after 5000 s towards HzOR. Moreover, two-electrode cell was constructed using Ni-15 at.% Zn/rGO as both cathode and anode for HER and HzOR, achieving 100 mA cm⁻² at an ultralow cell voltage of 0.418 V. The above outstanding bifunctional catalytic performance should be attributed to its large ECSA, high electrical conductivity and most importantly, its superaerophobic surface induced by the porous structure with nanosheet arrays.