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Intercalation-type metal oxides are promising active anode materials for the fabrication of safer rechargeable lithium-ion batteries, as they are capable of minimizing or even eliminating Li plating at low voltages. Due to the excellent cycle performance, high specific capacity and appropriate working potential, TiNb

Intrinsically low ion conductivity and unstable cathode electrolyte interface are two important factors affecting the performances of LiCoPO

Aqueous rechargeable batteries are promising candidates for safe and large-scale energy storage systems, but their electrochemical performances are limited by anode degradation. Herein, poly(2,5-di...

ABSTRACT: X Oilfield is located in the southern Bohai Sea. The formation fractures of the Neogene Minghuazhen Formation are developed. During drilling, wellbore collapse and block falling are prone to occur, and even cause stuck and stuck drilling. This paper presents a comprehensive geomechanical method which combines theoretical analysis with numerical simulation. By collecting a large number of geological, seismic, drilling and logging data, this method selects the appropriate theoretical model to predict and calculate the ground stress, pore pressure, fracture pressure, collapse pressure and rock mechanical parameters of well A, and draws the formation four pressure profile, and then obtains the safe drilling fluid density window of the well. In this paper, based on the elastic-plastic mechanics theory, the stress state of the wall rock is analyzed, and the numerical simulation of wellbore stability is carried out by using ABAQUS software. The influence of pore pressure, formation strength and drilling fluid density on wellbore stability is analyzed, which provides a powerful tool for understanding the wellbore instability mechanism of the target block of X oilfield, and effectively controls the wellbore instability phenomenon of Well A. 1. INTRODUCTION Since the 21st century, China has gradually focused on offshore oil and gas development in the context of the gradual depletion of conventional oil resources on land. Overall, there are relatively abundant oil and gas deposits in Chinese offshore areas. China’s offshore oil and gas resources are abundant in general. In recent years, Bohai Basin has made significant oil and gas discoveries and has a good development prospect. It is the main offshore oil and gas production area in China . The target well in this paper is well A, which is located in the south of Bohai Sea. The core technology of offshore drilling and completion and the stability of borehole wall are the key issues for the smooth development of offshore oil and gas resources. The theory and research results involved in this paper can not only provide scientific guidance for well A, but also provide theoretical support for the well area of the oilfield and even for the drilling of Bohai Bay in China, which has very important engineering guiding significance.

Intercalation-type metal oxides are promising active anode materials for the fabrication of safer rechargeable lithium-ion batteries, as they are capable of minimizing or even eliminating Li plating at low voltages. Due to the excellent cycle performance, high specific capacity and appropriate working potential, TiNb2O7 (TNO) is considered to be the candidate of anode materials. Despite a lot of beneficial characteristics, the slow electrochemical kinetics of the TNO-based anodes limits their wide use. In this paper, TiNb2O7@C was prepared by using the self-polymerization coating characteristics of dopamine to enhance the rate-performance and cycling stability. The TNO@C-2 particles present ideal rate performance with the discharge capacity of 295.6 mA h g−1 at 0.1 C. Moreover, the TNO@C-2 anode materials exhibit initial discharge capacity of 177.4 mA h g−1, providing 91% of capacity retention after 400 cycles at 10 C. The outstanding electrochemical performance can be contributed to the carbon layer, which builds fast lithium ion paths, enhancing the electrical conductivity of TNO. All these results confirm that TNO@C is a valid methodology to enhance rate-performance and cycling stability and is a new way to provide reliable and quickly rechargeable energy storage resources.

For high-voltage cycling of lithium-ion batteries, a gel polymer Li-ion conductor layer, P(VDF-HFP)/LiTFSI (PHL) with high electrochemical stability has been coated on the surfaces of as-formed LiCoO

Lithium metal anode has attracted soaring attention for high energy batteries. However, uncontrollable growth of dendritic Li and high chemical reactivity with electrolyte incur serious safety issues, hindering its practical applications. Carbon materials and their composites with controllable structures and properties, have been explored to address these issues and show great potential for lithium anode protection as stable scaffolds or Li storage reservoirs. However, the study of heterogeneous nucleation and growth of Li on carbon surfaces, especially on the basal plane of graphite layers, which is the dominating surface for graphene, carbon nanotube, and many other advanced carbon materials, remains empty, attributing to the lack of a perfect (planar and clean) deposition substrate. Herein, we adopt a single-layer graphene grown on Cu foil as an ideal Li plating substrate to reveal the fundamental behavior of Li metal nucleation and growth on carbon surface for the first time. We demonstrate that single-layer graphene on Cu foil, with nearly perfect structure, has a higher energy barrier for Li nucleation than Cu. Thus, it is more likely to form isolated and thicker dendrite layer on the carbon basal plane, and continuous dendrite was formed easily from Li nuclei even at a low Li deposited capacity of 30 µA h cm−2. Thereby, carbon materials with basal plane-dominated structures are proved lithiophobic and not suitable for the matrix of Li-metal anode. Our approach could lead to the realization of fundamental understanding of Li metal heterogeneous nucleation and growth on carbon surface with various electronic properties.

Garnet-like Li7La3Zr2O12 electrolytes with Nb doping are synthesized by self-consolidation method. Different from conventional methods such as cold or hot isostatic pressing, not any pressing assistance is employed throughout the preparation process. Although the preparation process is dramatically simplified, both density and ionic conductivity of the obtained samples are enhanced. Nb-doped content plays a key role in the sintering of the packed precursor powders and in the structure stabilization of the obtained bulk samples. The optimized 0.60 mol Nb-doped sample with relative density of 94%, fine particle boundaries, and solitary cubic structure possesses the maximum total ionic conductivity of 5.22 × 10−4 S cm−1 at 30 °C, which is comparable to the highest reported value of the samples prepared by conventional pressing methods. This work verifies that self-consolidation strategy is effective, reliable, and productive for the preparation of cubic Li7La3Zr2O12 electrolyte, which would significantly facilitate the development of ceramic electrolyte membrane technology.

Garnet-type Li 5 La 3 Ta 2 O 12 (LLTaO) solid electrolyte is a potential candidate component for future all-solid-state batteries due to its extraordinary stability against the reaction with molten lithium. In contrast with traditional cold isostatic pressing (CIP) method, which generally pursues ultra-high pressure, this paper tries to enhance the density and ionic conductivity of LLTaO by self-consolidation strategy without the assistance of any pressing operations. A LLTaO bulk with a relative density of 95% is obtained. SEM images reveal that the bulk sample is assembled by large dense particles in size of tens of microns indicating that the interstitial space among the particles has been dramatically minimized. Accordingly, the total ionic conductivity and the bulk ionic conductivity at 30 °C are promoted up about one order of magnitude higher to 2.63 × 10 −5 S cm −1 and 1.41 × 10 −4 S cm −1 , respectively. Moreover, the lithium ionic migration network in the crystalline unit cell of LLTaO is first explored from its assembled way. A hexagon-like basic unit with tetrahedral Li1 joint sites and Li1- - Li1 edges is identified. The tetrahedral Li1 sites act as crucial junctions for the transportation of lithium ions. This work would significantly stimulate the development of LLTaO electrolyte membrane technology.

Li5La3Nb2O12 (LLNO) is a typical garnet-like solid electrolyte with solitary cubic structure. However, its ionic conductivity is relatively low due to the low relative density when prepared by cold isostatic pressing method, which usually involves high-pressure machines, poor productivity, tedious pressing operations, and low density. In this paper, self-consolidation method is developed to sinter dense LLNO electrolyte. Although not any pressing operations are employed in the entire process, the relative density of LLNO is promoted up to 95%, which is much higher than the reported values of 45–80%. SEM images reveal that the sample is built by huge particles in size of 80 μm indicating that there are few boundaries in the sample. Moreover, a rich content of Li-Al-O compounds is detected out in the boundary areas, which may act as sintering aids for the sample to consolidate automatically. According to the highest density, the bulk ionic conductivity of LLNO sample reaches up to 1.61 × 10−4 S cm−1 at 30 °C, which is in the same order of magnitude as the value of cubic Li7La3Zr2O12 electrolyte. This work verifies the self-consolidation mechanism for the sintering of ceramic electrolytes and could significantly facilitate the development of LLNO membrane technology.

For the preparation of high-density ceramic electrolytes, researchers prefer cold or hot isostatic pressing method, which is not cost effective because of the ultra-high pressure and poor productivity. In this paper, we present a novel “self-consolidation” method to prepare dense cubic Al-doped Li7La3Zr2O12 (LLZO) without the assist of pressing. The relative density of LLZO bulk sample is about 93–96%, and the 0.10 mol Al-doped sample with the purest cubic structure possesses the highest total ionic conductivity of 1.41 × 10−4 S cm−1 at 30 °C, which is comparable to the conductivities of the samples prepared by traditional high-pressure methods. Furthermore, a LLZO crystal unit cell model is constructed and the self-consolidation mechanism for LLZO from crystal unit cell to bulk is explored. The surface tension of the molten Li compounds acts as the intrinsic power for the self-consolidation. This work demonstrates a facile, productive and reliable route for the preparation of dense cubic LLZO, and provides an important insight into the microscopic consolidation mechanism of ceramic electrolytes. Keywords: Lithium ion battery, Li7La3Zr2O12 solid state electrolyte, Ionic conductivity, Cubic structure

Improving the cycling performance without sacrificing its capacity is challenging for high-voltage LiNi0.5Mn1.5O4 cathode due to the trade-off nature among the key properties. A self-polymerization process of dopamine was utilized to grow polydopamine (PDA)-nano titanium dioxide assembly. PDA@TiO2 composite was demonstrated to be integrated with the particles of high-voltage spinel LiNi0.5Mn1.5O4 cathodes via wet chemical method. PDA@TiO2 decorated LNMO improved the long-term cycling performance and rate capability by suppressing detrimental side reactions in balancing the interfacial stability and Li+ diffusion kinetics of LNMO and consequently providing efficient conductive pathways. As a result, 2% PDA@TiO2 modified LNMO cathode exhibited the high reversible capacity of 117 mAh g−1 after 1000 cycles with good capacity retention of 90.7% at 1 C, and superior rate capability (78.5 mAh g−1 at 5 C) at room temperature. Remarkably, a significant improvement in cycling stability at an elevated temperature (50 °C) was obtained for the PDA@TiO2-LNMO composite, giving a capacity retention of 93% after 100 cycles at 1 C. The mechanism of performance improvement could be attributed to the maintenance of the structural stability of LNMO cathode materials and the enhanced kinetics of the remarkable lithium-ion diffusion through the protective effect of PDA@TiO2 decorating.

The carbon-coated chevrel phase of Mo6S8 as electrode material was fabricated for the first time. Compared with the bare Mo6S8 and 10%C-Mo6S8 anodes, the 5%C-Mo6S8 anode possesses excellent rate capability and cyclic performance at the cutoff voltage of 1.5 V using LiMn2O4 as the cathode, which delivers a reversible capacity of ∼ 85 mAh·g−1 and an average discharge voltage of as high as ∼ 2 V maintains 93% of initial discharge capacity even after 400 cycles at 1C and in 21 M aqueous electrolyte. This study provides a promising anode material for aqueous lithium-ion batteries because of its high capacity, stability and environmental inertness. Furthermore, the results demonstrate that this method could expand the synthesis and application of these unique compounds.

For conventional preparation methods of Li7La3Zr2O12 (LLZO) solid state electrolytes, there is a stereotype that higher density always comes from higher pressure enforced upon the LLZO pellets. In this paper, a different way with an auto-consolidation mechanism is provided and discussed. No pressing operations are employed during the whole preparation process. Due to the surface tension of liquid melted Li2O at sintering temperature, LLZO particles could aggregate together freely and automatically. The preparation process for dense LLZO is greatly simplified. A dense tetragonal LLZO with high relative density about 93% has been prepared successfully by this auto-consolidation method. And there are no voids observed in the SEM images. At 30 °C, the total conductivity is about 5.67 × 10−5 S cm−1, which is the highest one for tetragonal LLZO in the reported issues, even two times higher than that prepared by hot-pressing method. The activation energy for total conductivity is ∼0.35 eV atom−1 at 30–120 °C, slightly lower than the previous reported values. This work sheds light on the understanding of the consolidation mechanism for solid electrolytes and suggests a reliable route to syhthesize cemanic solid electrolytes.

Low-cost and chemically stable stainless steel mesh is used widely as a current collector in aqueous batteries, but is not electrochemically stable due to the oxygen evolution corrosion reaction. Here we report C-coated stainless steel (CSS) mesh as a corrosion-resistant current collector using a multi-functional binder, NaPAA, in aqueous lithium-ion battery cathodes. The results show that the corrosion potential of the CSS mesh is shifted positively to a large extent, indicating the suppression of oxygen evolution at high potentials. Thereby, C-coated stainless steel mesh based electrodes show better rate capability and cycling stability than those fabricated on traditional stainless steel mesh, graphite-emulsion coated stainless steel mesh and even titanium mesh based current collectors, especially at ultrahigh current densities. The plausibility of using such low-cost and green corrosion-resistant current collectors for aqueous batteries marks an important step toward industrial applications for low-cost, safe and large-scale energy storage.

Aqueous lithium ion batteries (ALIBs) receive increasing attention due to their intrinsic non-flammable nature. However, their practical application, has been limited by the poor comprehensive properties of aqueous electrolytes, which severely restricts the cycle life and cost of ALIBs. In this study, the concentration and components of aqueous electrolytes were optimized to balance the battery performance and cost of ALIBs. The wide electrochemical stability window of around 2 V is achieved for just 9 ~15 m LiTFSI solutions other than the counterparts of widely used LiNO3 solutions, attributed to most water molecules in crystalline hydrates. A great improvement in the performance of LiMn2O4 electrodes is carried out. The optimal LiTFSI solution of 15 m allows LiMn2O4 to be long cycled at 1C with a discharge capacity of 111mAh∙g−1 and a high capacity retention of 88% after 1400 cycles. At the high C-rate of 5 C, a discharge capacity of 91 mAh∙g−1 and a capacity retention rate of as high as 92% after 3000 cycles are achieved. In highly concentrated LiTFSI solutions beyond 15 m, a decay in the performance of LiMn2O4 electrodes is found, especially the rate capability, attributed to the rather low ion conductivity.

The spherical LiTi(PO4)3/C composites were prepared through spray drying method followed high-temperature calcination and used as anodes for aqueous lithium ion batteries. The effect of different organic carbon source based on different coating mechanisms and carbon content on the electrochemical properties of LiTi(PO4)3/C composite anodes were investigated. Results show that the amount of carbon coating is too low to prevent water from eroding. In contrast, if the amount of carbon coating is too high, the resistance of lithium ion diffusion will be high; the optimal carbon coating amount of LiTi2(PO4)3/C electrodes is 13%. The uniformity of carbon coating and the thickness of coating layer are the two main factors affecting the performance of coated electrodes. The coating mechanism has critical influence on the uniformity of carbon coating. The most uniform carbon coating was obtained by using polydopamine as the carbon source, followed by using the organic macromolecule, glucose as the carbon source. Polyacrylonitrile containing both carbon and nitrogen exhibits no special effect of nitrogen doping. (The two main factors affecting the performance of the carbon coated electrode are the uniformity and the thickness of the carbon layer.) The best performance is achieved by LiTi2(PO4)3/C anodes with the carbon amount of 13% prepared by using polydopamine as the carbon source. But, from a viewpoint of mass production and scale-up, it is more suitable to use low-cost and water-soluble glucose as carbon source.

The sodium manganese oxide, Na0.44MnO2, was synthesized by a solid-state reaction routine combined with a sol–gel process using Mn(CH3CO2)2·4H2O as the manganese source. Results show that the capacity and cycling stability of Na0.44MnO2 cathodes are enhanced significantly by using a hybrid aqueous electrolyte (Na2SO4, ZnSO4 and MnSO4). The energy storage mechanism of as-prepared Na0.44MnO2 in the hybrid aqueous electrolyte is associated with the insertion/extraction of zinc and sodium multi-ions with the help of synergistic effects between zinc and manganese ions and the quasi-reversible deposition–dissolution process of Mn2+ ions. The Na0.44MnO2 electrode displays both excellent storage properties with zinc, sodium and manganese ions (∼340 mA h g−1 at 100 mA g−1 after 150 cycles) and reversibility (∼100% coulombic efficiency during cycling). The excellent reversibility and good cycling properties indicate that the Na0.44MnO2 can be a promising material for energy storage devices by using a hybrid aqueous electrolyte.

Using the tetrachloro-p-benzoquinone (TCQ) monomer, poly(benzoquinonyl sulfide) (PBQS) was synthesized by a simple polycondensation reaction. The influence of the molar ratio of S to Na2S on the electrochemical performance of a PBQS anode was assessed by changing the amount of S added. The results showed that the electrochemical performance of PBQS strongly depended on the molar ratio of S to Na2S. When the molar ratio of S to Na2S was 0.4, two Cl were replaced by S, and PBQS with a stable structure was obtained. The discharge capacity of PBQS exceeded 140 mAh∙g -1 . At the same time, PBQS displayed satisfactory rate capability and excellent cyclability. Conversely, when the molar ratio of S to Na2S was decreased to 0.25, Cl was not substituted completely and the polymerization degree was low. Upon increasing the molar ratio of S to Na2S to 0.7, an unstable S―S bond may form in the polymer. The above two factors degraded the electrode performance of these materials.

LiFePO4 based aqueous lithium batteries using aqueous electrolytes suffer from poor cycling performance. This is mainly caused by the Fe dissolution and Li loss generated from the effects of water. In this paper, fumed silica based gel electrolytes were prepared and optimized for improving the cycling performance of the LiFePO4 electrodes owing to superior stability and comparable ionic conductivity. It was manifested that the Zn/LiFePO4 cells using this homogenous gel electrolyte showed stable charge/discharge voltage profiles and excellent cycling performance at room temperature. The dissolution of Fe and the loss of Li in this electrolyte is significantly suppressed. These superior performances could endow this gel electrolyte as a promising alternative to aqueous electrolyte systems in the LiFePO4 batteries at room temperatures.

The electrochemical stability of LiFePO4 in a Li+-containing aqueous electrolyte solution is critically dependent on the pH value of the aqueous solution. It shows a considerable decay in capacity of LiFePO4 upon cycling when the pH value is increased to 11. The mechanism responsible for the capacity fading is extensively investigated by means of cyclic voltammogram, ac impedance, charge/discharge, ex situ X-ray diffraction, and chemical analysis. LiFePO4 is relatively electrochemically stable in LiNO3 aqueous solution with pH=7. But the electrochemical performance of LiFePO4 in aqueous electrolyte is inferior to that in organic electrolyte. It is attributed to the loss of Li and the Fe, P dissolution during prolonged charge-discharge in aqueous medium. A precipitate is formed on the surface of LiFePO4 electrodes. It results in the change of crystalline structure, a large electrode polarization, and capacity fading.

Electrodeposition and dissolution of zinc in sulfuric acid were studied as the negative electrode reactions in acidic zinc-based redox flow batteries. The zinc deposition and dissolution is a quasi-reversible reaction with a zinc ion diffusion coefficient of 4.6 × 10−6 cm2 s−1 obtained. The increase of acid concentration facilitates an improvement in the kinetics of zinc electrodeposition–dissolution process. But too high acid concentration would result in a significant decrease in charge efficiency. The performance of the zinc electrode in a three-electrode system with magnetic stirring was also studied as a function of Zn(II) ion concentration, sulfuric acid concentration, current density, and the addition of additives in 1 M H2SO4 medium. The optimum electrolyte composition is suggested at high zinc(II) concentration (1.25 M) and moderate sulfuric acid concentration (1.0–1.5 M) at a current density range of 20–30 mA cm−2. Whether in acid-free solution or in sulfuric acid solution with or without additives, no dendrite formation is observed after zinc electrodeposition for 1 h at 20 mA cm−2. The energy efficiency is improved from 77 % in the absence of additives in 1 M H2SO4 medium to over 80 % upon the addition of indium oxide or SLS–Sb(III) combined additive as hydrogen suppressants.

Lead ion and tetrabutylammonium bromide (TBAB) have been testified as inhibitors of spongy zinc electro-growth from flowing alkaline zincate solutions. To assess the efficacy of the two additives, current–time technique using potentiostatic electro-deposition, scanning electron microscopy and cycling test were undertaken. The results show that the growth of spongy zinc in flowing alkaline zincate solutions can be effectively inhibited by the addition of 10 −4 M Pb(II) or TBAB at the cathodic potential ( η = −100 mV), respectively. But, the dual addition of 10 −4 M Pb(II) and 5 × 10 −5 M TBAB produces more effective suppression on spongy zinc growth. Obvious synergistic effect of Pb(II) and TBAB on the inhibition of spongy zinc deposits is found. From the charge/discharge cycling tests of the single flow Zn–Ni test cells, it is shown that the rechargeability of Zn anode is highly improved by the mixed introduction of 10 −4 M Pb(II) and 5 × 10 −5 M TBAB.

The present paper aims at discussing the effect of zinc ions in electrolytes on the cycling stability of nickel oxide electrodes for the zinc/nickel single flow battery. It is shown that the presence of zinc in KOH electrolytes decreases the charging voltage to some extent and inhibits changes in the galvanostatic charging curve vs. cycling number as compared to KOH electrolytes with no zinc present. As a result, the discharge capacity of the electrodes basically does not decay even after 500 charge–discharge cycles. The cycling performance of nickel oxide electrodes is enhanced substantially. It is demonstrated that zinc ions in electrolytes may be incorporated into the lattice structure of nickel hydroxides during the cell cycling, forming a composite where the zinc plays a role as an additive and preventing the formation of γ-phase and overcharge.

In this study, the electrochemical behavior of tiron in aqueous solutions and the influence of pH were investigated. A change of pH mainly produces the following results. In acidic solutions of pH below 4, the electrode reaction of tiron exhibits a simple process at a relatively high potential with a favorable quasi-reversibility. The tiron redox reaction exhibits fast electrode kinetics and a diffusion-controlled process. In solutions of pH above 4, the electrode reaction of tiron tends to be complicated. Thus, acidic aqueous solutions of pH below 4 are favorable for the tiron as active species of a redox flow battery (RFB). Constant-current electrolysis shows that a part of capacity is irreversible and the structure of tiron is changed for the first electrolysis, which may result from an ECE process for the tiron electro-oxidation. Thus, the tiron needs an activation process for the application of a RFB. Average coulombic and energy efficiencies of the tiron/Pb battery are 93 and 82%, respectively, showing that self-discharge is small during the short-term cycling. The preliminary exploration shows that the tiron is electrochemically promising for redox flow battery application.

The effects of the presence of additives like lead and tungstate ions in flowing alkaline zincate solutions on suppressing spongy zinc electrogrowth are examined. The results show that the two additives with optimal concentrations in flowing electrolytes can suppress spongy zinc initiation and propagation. And, the two additives can bring about more uniform and compact deposits and, thereby, reduce spongy zinc growth. The influence of lead and tungstate ions on the zinc deposition/dissolution is evaluated by cyclic voltammetry. It also shows that the addition of the two additives is largely a blocking action, and the co-deposition of lead and zinc ions may occur. The performance of the zinc-air flow battery with zinc regeneration electrolysis is determined. It shows that by the addition of 0.6 M Na 2 WO 4 or 10 −4 M to 10 −3 M lead, compact or mixed compact–spongy zinc deposits are created and the favorable charge/discharge performance of the battery is achieved with an energy efficiency of approximately 60%.

A zinc–air battery using zinc regeneration electrolysis with propanol oxidation as a counter electrode reaction is reported in this paper. It possesses functions of both zincate reduction and electrochemical preparation, showing the potential for increasing the electronic energy utilization. Charge/discharge tests and scanning electron microscopy (SEM) micrographs reveal that when a nickel sheet plated with the high-H2-overpotential metal, cadmium, was used as the negative substrate electrode, the dendritic formation and hydrogen evolution are suppressed effectively, and granular zinc deposits become larger but relatively dense with the increase of charge time. The performance of batteries is favorable even if the charge time is as long as 5 h at the current density of 20 mA cm−2. Better discharge performance is achieved using a ‘cavity-opening’ configuration for the discharge cell rather than a ‘gas-introducing’ configuration. The highest energy efficiency is up to 59.2%. That is, the energy consumed by organic electro-synthesis can be recovered by 59.2%. Cyclic voltammograms show that the sintered nickel electrode exhibits a good electro-catalysis activity for the propanol oxidation. The increase of propanol concentration conduces to an enhancement in the organic electro-synthesis efficiency. The organic electro-synthesis current efficiency of 82% can be obtained.

The present paper reports a new single flow acid battery, Cu–H2SO4–PbO2 battery, in which smooth graphite is employed as negative electrode, lead dioxide as positive electrode and the intermixture of H2SO4–CuSO4 as electrolyte. The reaction Cu⇌Cu2+ takes place on the negative electrode. The working process of the battery is only the circulation of H2SO4–CuSO4 intermixture by means of a single pump. No cationic membrane is needed. A miniature acidic copper single flow battery with a rated capacity of 2000 mAh can offer a discharge voltage of 1.29 V, an average coulombic efficiency of 97% and an energy efficiency of 83% during 450 cycles at a charge/discharge current of 1000 mA. Keywords: Single flow acid battery, Lead dioxide, Coulombic efficiency, Copper

A new bifunctional redox flow battery (BRFB) system, V(III)/V(II)-L-cystine(O-2), was systematically investigated by using different separators. It is shown that during charge, water transfer is significantly restricted with increasing the concentration of HBr when the Nafion 115 cation exchange membrane is employed. The same result can be obtained when the gas diffusion layer (GDL) hot-pressed separator is used. The organic electro-synthesis is directly correlated with the crossover of vanadium. When employing the anion exchange membrane, the electro-synthesis efficiency is over 96% due to a minimal crossover of vanadium. When the GDL hot-pressed separator is applied, the crossover of vanadium and water transfer are noticeably prevented and the electro-synthesis efficiency of over 99% is obtained. Those impurities such as vanadium ions and bromine can be eliminated through the purification of organic electro-synthesized products. The purified product is identified to be L-cysteic acid by IR spectrum. The BRFB shows a favorable discharge performance at a current density of 20 mA cm(-2). Best discharge performance is achieved by using the GDL hot-pressed separator. The coulombic efficiency of 87% and energy efficiency of about 58% can be obtained. The cause of major energy losses is mainly associated with the cross-contamination of anodic and cathodic active electrolytes. (C) 2008 Elsevier Ltd. All rights reserved.

Zinc deposition from alkaline zincate solution in single flow zinc/nickel battery has been investigated. The effect of different substrates such as copper, cadmium and lead were examined by using cyclic voltammetry and cathodic polarization technique. It was found that the cadmium substrate is better than the others. Zinc deposition was carried out by using galvanostatic technique, and the deposits were examined by SEM. The results demonstrated that there is no zinc dendrite on the cadmium substrate in flowing electrolyte. Coulombic and voltage efficiencies of 98 and 88%, respectively, are obtained in a small laboratory cell.

Bifunctional redox flow batteries (BRFB) possess functions of both electricity storage and electrochemical preparation, having the potential for increasing the electrical energy utilization. A V(III)/V(II)–glyoxal(O 2 ) system has been developed. Separators of the BRFB play a key role in BRFB performance. A Nafion solution was sprayed on a gas diffusion layer (GDL) at the Nafion loading of 2 mg cm −2 , and the GDL was then hot-pressed onto a Nafion115 cation exchange membrane, obtaining a modified separator. This separator not only prevents the crossover of vanadium but also has favorable conductivity, obtaining optimal charge and organic electro-synthesis performance of the BRFB. The effects of the concentrations of glyoxal and HCl on the performance of BRFB were also investigated. It is shown that the optimal concentration of glyoxal and HCl should be 1.2 and 3 M, respectively. As a result, the current efficiency of organic electro-synthesis is further increased. An acceptable discharge performance is achieved for a period exceeding 20 h at the current density of 20 mA cm −2 . The average discharge voltage of 0.73 V and the coulombic efficiency of 66% are obtained. It is demonstrated that the principle of the BRFB is feasible. However, further experiments are needed to improve the performance.

A novel electrode-bipolar plate assembly has been developed and evaluated for application in the vanadium redox flow battery (VRB). It is composed of three parts: a graphite felt (electrode), an adhesive conducting layer (ACL) and a flexible graphite plate (bipolar plate). The ACL connects the electrode with the bipolar plate to an assembly. By the evaluations of cost, resistivity, surface morphology, electrolyte permeation and single cell performance, this novel assembly demonstrates its applicability in VRB as evident in the following outcomes: (1) lowers the cost and area resistivity to about 10% and 40% of the conventional setups, respectively; (2) improves electrical conductivity to 4.97 mΩ cm as compared to over 100 mΩ cm of the carbon-plastic composite bipolar plate; (3) attains zero electrolyte permeation; and (4) achieves a higher energy efficiency of 81% at a charge/discharge current density of 40 mA cm−2 when employed in a VRB single cell, which is 73% for the conventional setup. All these indicate that the novel electrode-bipolar plate assembly is a promising candidate for VRB applications.