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Nafion is currently the most stable ion exchange membrane for vanadium redox flow battery (VRB). In order to decrease the high vanadium permeability of Nafion while still keeping its high ionic conductivity and stability, in this study, solution atom transfer radical polymerization (ATRP) method is used with Nafion as initiator to prepare amphoteric Nafion membrane with tunable cationic and anionic ratios. Polymers of [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC) and sodium 4-styrenesulfonate (NaSS) are chosen as cationic and anionic monomers, respectively. FT-IR (Fourier transform infrared) and 1H NMR (nuclear magnetic resonance) tests prove that the METAC and NaSS have been successfully bonded on the Nafion molecules. The solution-casted amphoteric Nafion membrane M-1:1 has shown the highest ion selectivity among all the grafted Nafion membranes. The VRB with M-1:1 membrane has shown the highest average energy efficiency of 83.9% at current density of 40–80 mA cm−2, which is 4.2% higher than that of Nafion 212 (79.7%). One hundred cycles dynamic charge-discharge test proves that the M-1:1 membrane possesses enough stability and good discharge capacity retention ability. On-line self-discharge test further proves that the M-1:1 membrane has lower vanadium ions permeation than that of Nafion 212 membrane. All the results prove that ATRP is an effective method for preparation of novel amphoteric materials for VRB application.

In order to reduce the vanadium ion permeability while still keep its high stability, atom radical polymerization (ATRP) method was used to introduce zwitterionic sulfobetaine methacrylate (SBMA) onto the Nafion matrix in homogenous solution. The Nafion-grafted poly SBMA (N-g-PSBMA) solution was then used to blend with common Nafion solution to prepare Nafion/Nafion-g-PSBMA (N/N-g-PSBMA) amphoteric membranes by solution casting method. The grafted resins and membranes were characterized by attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), energy dispersive X-Ray spectroscopy (EDX), scanning electron microscopy (SEM), and water-contact angle analysis. The results prove that the SBMA has been successfully grafted onto the Nafion backbones. Furthermore, the N/N-g-PSBMA membranes have shown higher ion selectivity, coulombic efficiency, and energy efficiency than that of pure recast Nafion (r-Nafion) membrane for VRB application. At the current density of 40–80 mA cm−2, the average energy efficiency of the VRB with N/N-g-PSBMA-20% membrane has reached up to 84.9%, which is 4.2% higher than that of the VRB with the r-Nafion membrane at the same current densities. Moreover, the 100-cycles charge-discharge test proves that the N/N-g-PSBMA-20% membrane possesses higher stability and capacity retention ability than that of r-Nafion membrane, confirming the great potential of such membranes for VRB application.

LiNi0.8Co0.1Mn0.1O2 cathode material with full-gradient structure is prepared by a novel co-precipitation method. Scanning electron microscope images show that the material presents regular spherical shape. X-ray diffraction pattern shows that the material has good layered structure. Energy dispersive X-ray spectroscopy analysis for the cross section of secondary particles shows that the relative molar content of Ni gradually decreases from 84% to 76% along the center to the edge of hemisphere, while the Mn content increases gradually. Moreover, the Co content also presents a slow gradient change. Electrochemical tests at room temperature show that the retention rates of discharge capacity for full-gradient material after 100 cycles at current density of 1C and 5C are 98.8% and 93.7%, respectively, which are obviously improved compared with intrinsic material. The gradient material also shows improved midpoint voltage and specific energy. Moreover, full-gradient material exhibits good cyclic stability at high temperature, and the capacity retention rate of 100 cycles is as high as 90% at 5C rate, which is obviously higher than 71.8% of intrinsic material. Impedance spectroscopy studies show that the solid-state diffusion coefficient of lithium ion in gradient material has been significantly improved, thus showing good electrochemical properties. The full-gradient material shows excellent application prospects in the field of power batteries.

The aim of this work is to prepare a hydrophobic cathode equipped with quite a few cracks for gas transfer, which can prepare H2O2 in the course of electro-Fenton process. Scanning electron microscopy (SEM) and optical digital microscope are used to characterize the morphology of electrode, and an electrochemical workstation (CHI660e) is used to carry out all electrochemical studies with a conventional three-electrode system. The results demonstrate that the porous electrode is conducive to gas transmission with these cracks which can avoid the formation of bubbles. Additionally, the reaction is almost not affected by the content of dissolved oxygen and the gas flow with this structure. Under the conditions of 300 mA/cm2 (current density), the H2O2 concentration is up to 14.4 mmol/L after 30 min electrolysis with current efficiency beyond 90%. Furthermore, the cathode is successfully applied to electro-Fenton process which reduced catalyst loading. The results indicate that total degradation of MO is observed at the first 10 min, and 81% of TOC can be removed when the dosage of catalyst is 0.4 mmol/L within 60 min.

A novel N115-g-PSBMA membrane containing zwitterionic groups was successfully prepared by grafting the zwitterionic SBMA (sulfobetaine methacrylate) onto Nafion 115 (N115) via SI-ATRP (surface-initiated atom transfer radical polymerization) technique. The N115-g-PSBMA membrane has shown higher hydrophilicity, lower vanadium permeability, higher coulombic efficiency and energy efficiency than that of commercial N115 membrane for VRB (vanadium redox flow battery) application. At the current density of 40–80 mA cm−2, the average energy efficiency of the VRB with N115-g-PSBMA membrane has reached up to 87.3%, which is 2.6% higher than that of the VRB with N115 membrane at the same current densities. The method is expected to present a new direction to prepare novel separators with both excellent performances and low cost for VRB application.

Due to the good balance between the low vanadium permeability and high proton conductivity, AIEM (amphoteric ion exchange membrane) has attracted vast consideration for all vanadium redox flow battery (VRB) application. Similar to the AIEM, BPMs (bipolar membranes) also have both anion and cation exchange groups in the anion-selective layer and cation-selective layer. In this paper, a series of BPMs based on PTFE (polytetrafluoroethylene) reinforced QAPSF (quaternized polysulfone) and SPEEK (sulfonated poly ether ether ketone) are prepared and investigated for the VRB application. As expected, all the membranes have presented typical sandwiched structure with an obvious intermediate layer observed by SEM. Owing to the “Donnan exclusion effect” of anion groups in QAPSF, all the BPMs have shown very low VO2+ permeability. Particularly, the battery with Q/P/S-3:2 membrane has shown average coulombic efficiency of 98.9% at current density of 40–80 mA cm−2. Considering the simple adjustment and abundant choice of cation or anion resins, BPMs membranes should be a promising candidate for VRB application after further investigation.

How to solve the crossover of vanadium ions through ion exchange membrane is a key issue in vanadium redox flow battery (VRB), especially for ultra-thin membranes used for VRB to obtain a lower cell resistance. Herein, an ultra-thin (~ 30 μm) PTFE/SPEEK [polytetrafluoroethylene/sulfonated poly(ether ether ketone), P/S] membrane is successfully prepared and modified by using layer-by-layer (LBL) self-assembly technique with polycation poly(diallyldimethylammonium chloride) (PDDA) and polyanion poly(sodium styrene sulfonate) (PSS). P/S membranes are alternatively immersed in positively and negatively charged polyelectrolyte to form 2 to 8 bilayers onto its surface. Consequently, a series of P/S-[PDDA/PSS] n (n is the number of multilayers) membranes are fabricated. Both the physicochemical properties and VRB performances of the P/S-[PDDA/PSS] n membranes are then investigated in detail. Results show that the ion selectivity of the P/S-[PDDA/PSS] n membranes is much higher than that of pristine P/S membrane, especially for P/S-[PDDA/PSS]6 membrane. As a result, the VRB with the P/S-[PDDA/PSS]6 membrane exhibits the highest coulombic efficiency (CE) of 96.5% at 80 mA cm−2, the highest voltage efficiency of 94.7% at 40 mA cm−2 and the highest energy efficiency of 87.7% at both 40 and 50 mA cm−2, respectively. In addition, 80 times charge–discharge test proves that the P/S-[PDDA/PSS]6 membrane possesses high stability and no obvious CE decay after running. All the results show that the LBL technique is an effective way to prepare ultra-thin membrane with high ion selectivity for VRB application.

Blend membranes of quaternized polysulfone/polyvinylidene fluoride (Q/P) for all vanadium redox flow battery (VRFB) are prepared by one-step solution casting method to reduce the vanadium permeation and improve the mechanical properties of pure quaternized polysulfone membrane. The physicochemical properties and electrochemical performances of the Q/P membranes are characterized in detail. In comparison with the Nafion 115 membrane, Q/P blend membranes exhibit higher water uptake, ion exchange capacity (IEC) and swelling ratio, lower ionic conductivity and ultra-lower vanadium permeability, better stability and superior VRFB cycle performances. Owing to the ultra-low vanadium permeability, the VRFB with Q/P-20% blend membrane has shown the highest coulombic efficiency of 99.29% at 80 mA cm−2 and the Q/P-15% membrane has shown the highest EE of 91.12% at 40 mA cm−2, which is 4.89% and 3.33% higher than that of Nafion 115 at the same current density, respectively. The mechanical properties of the Q/P blend membranes increase with the increasing of the PVDF mass ratio. It reveals that the introduction of PVDF is of great significance to improve the performances of the Q/P blend membranes.

The electron transfer failure model is proposed to analyze the effects of discharge products on the air electrode performance in lithium-air batteries. In order to understand how the air electrode products are obtained during the discharge cycle, three kinds of carbon-based air electrode are constructed, and discharged products are analyzed by powder XRD and SEM techniques. It can be concluded that the air electrode is covered with the products, indicating that the discharge products closely depended on the surface states of carbon materials. EIS studies show that the value of R ct value changes due to the deposition of discharge products on carbon materials. Finally, all present studies show that the air electrode failure is mainly caused by the difficulty of charge transfer.

Spherical nickel rich layer cathode materials (LiNi 0.85− x Co 0.15 Al x O 2 ( x = 0.02, 0.05 and 0.10), NCA) with excellent electrochemical performance for high energy densities lithium-ion batteries are successfully synthesized by a continuous co-precipitation method. An elaborate design of Al solution with sodium aluminate is successfully adopted, which can efficiently prevent rapid precipitation of Al(OH) 3 and obtain the precipitated precursors. The thermodynamic model is established in the Ni—Co—Al—NH 3 —H 2 O system and investigation of precipitation mechanism is carried out systematically, and the results demonstrate that the spherical LiNi 0.85− x Co 0.15 Al x O 2 can be obtained through this route. Charge and discharge tests show that LiNi 0.85− x Co 0.15 Al x O 2 synthesized has a high initial discharge specific capacity of 208 mAh/g at 0.1 C and a good capacity retention of 90.2% after 200 cycles at 0.5 C between 2.5 and 4.3 V. It is expected that performance of NCA electrodes for advancing lithium-ion batteries could be improved with the new process proposed in this study.

The effect of casting solvent and annealing temperature on microstructure, proton conductivity, vanadium permeability, mechanical properties as well as single cell performances of recast Nafion membranes for vanadium redox flow battery (VRB) are conducted experimentally. Membranes are prepared from NMP (N-methly-2-pyrrolidone), DMF(dimethylformamide), DMSO (dimethyl sulfoxide) and EtOH (ethanol/water), annealed at 100 °C, 140 °C and 180 °C, respectively. The micromorphology of recast Nafion membranes is thoroughly examined by Fourier transform infrared (FT-IR), scanning electron microscope (SEM), 1H NMR spectroscopy, X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). It is found that the formation of Nafion membranes is strongly influenced by both temperature and solvent. Results show that solvent is a primary factor affecting the microstructure of recast membranes at lower temperature, but its effect is no longer distinct at higher temperature. EtOH-140 membranes has the highest proton conductivity, NMP-180 has the lowest vanadium permeability, DMF-180 has the smallest ionic cluster, DMSO-180 has the best mechanical properties among the recast Nafion membranes. Single cell tests show that DMF-180 has the best comprehensive cell performances, its capacity decay rate is even smaller than that of commercial Nafion 212 membrane after charge-discharged for 100 cycles at current density of 80 mA cm−2.

A novel carbon nanofiber co-doped with nitrogen and phosphorus (NPCNF) that has a high specific surface area with good electrocatalytic properties for oxygen reduction reaction (ORR) was synthesized using a template-free method. The fabricated processes involve the pyrolysis of phytic acid doped polyaniline aerogel. A nonaqueous Li-O2 battery with a specific capacity as huge as 12,607 mAh g-1 was constructed using an oxygen electrode based on NPCNFs supported by Ni foam. The NPCNFs electrode was also shown lower overpotential than that of the pure carbon. The observed excellent electrochemical performance could be due to its unique foam-like N, P co-doped carbon microstructure with a high ORR catalytic activity. These results indicate that using NPCNF as a cathode material could be a feasible approach to obtain the Li-O2 battery high capacity.

In order to improve the selectivity of porous membrane for vanadium redox flow battery (VRB). A polypyrrole (PPy) thin film composite (TFC) membrane was prepared via interfacial polymerization (IP) method and investigated for VRB application. The optimized PPy TFC membrane has shown both low VO2+ permeability and low area resistance compared to that of commercial Nafion 115 membrane. The VRB cell assembled with PPy TFC membrane shows a coulombic efficiency (CE) of 98.1% and energy efficiency of 81.0% at 80 mA cm−2, which is 2.0% and 6.3% higher than that of Nafion 115 membrane, respectively. Furthermore, 93 cycles charge-discharge test proves that the PPy TFC membrane is very stable and the CE decrease rate is only 0.4% for per-cycle on average. Considering the high selectivity, facile preparation procedure and high stability of PPy TFC membrane, it is thus an ideal system for VRB application to overcome the trade-off between vanadium ions permeability and proton conductivity.

The aim of the study is to increase the stability and selectivity of a polyamide (PA) thin film composite (TFC) membrane (MT) used in a vanadium redox flow battery (VRB). After immersion for different periods, different concentrations of polydopamine (PDA) are successfully self-polymerized on the surface of the PA TFC membrane to prepare an optimized MDx-y (x and y denote the dopamine concentration and reaction time, respectively) membrane that is used in a VRB. The structure and physicochemical properties of MDx-y membranes are thoroughly evaluated using SEM (scanning electronic microscope), AFM (atomic force microscope), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy), and TG (thermogravimetry) and compared to a pristine substrate (M0) and MT membranes. The PDA layer significantly improves both the selectivity and stability of the pristine MT membrane. After coating the MT membrane with PDA, the average pore radius of the MD membrane is estimated to be 0.24–0.25 nm, which is ideal for separate protons ( 0.6 nm) in terms of ion exclusion effect. As a result, the PDA coated MT membranes show very low vanadium ion permeability and high proton to vanadium selectivity. The coulombic efficiency of the optimized PDA-coated TFC membrane (MD2.0-10) reaches 99.3% at 80 mA cm−2, which is higher than both pristine TFC and commercial Nafion 115 (N115) membranes. Even after 158 charge-discharge tests, the energy efficiency of the MD2.0-10 membrane remains stable at greater than 80% at 80 mA cm−2, a value that is superior to the pure TFC membrane. In addition, the MD2.0-10 membrane also exhibits excellent chemical stability, increased mechanical properties and high discharge capacity retention rate, suggesting that it has great prospects in VRB applications.

Ultra-thin (~ 30 μm) polytetrafluoroethene (PTFE)/Nafion/silica composite membranes for all vanadium redox flow battery (VRB) are prepared via solution casting method. The membranes are prepared using nano SiO2 powder with composition of 1% to 9%. Water uptake, proton conductivity, area resistance and vanadium ion permeability of the membrane are measured to evaluate the membrane properties. The membrane with 3% SiO2 content (P/N/S–cast-3) shows the best cell performance among all the prepared composite membranes compared to that of the pristine PTFE/Nafion membrane. Furthermore, the properties of the P/N/S–cast-3 membrane are also compared to that of the membrane prepared by sol–gel method in literature. Experimental results indicate that the membranes prepared with nano SiO2 powder show promising prospects for VRB application. However, its performances are not as good as the P/N/S composite membrane prepared by sol–gel method due to the aggregation of nano SiO2 powder.

Layered LiNi0.8Co0.15Al0.05O2 cathode materials have been synthesized by co-precipitation methods. The effect of pre-thermal treatment was investigated by thermogravimetric differential thermal analysis. Although X-ray diffraction has confirmed that all diffraction peaks in XRD patterns for samples treated at 500 ~ 750 °C can be a well-indexed hexagonal structure, the status of nickel ions varied. Samples pre-treated at different temperatures show different colors and had various contents of Ni3+ measured by XPS. Powders that heated again at 800 °C under the condition of dried oxygen for 12 h after pre-thermal treatment show different electrochemical performances, which pre-thermal treated at 600 °C had a highest reversible specific capacity about 180 mAh·g−1 and capacity retention of 91.7 % after 50 cycles when cycled at a current density of 0.1 C between 2.5–4.3 V at room temperature. The relationship between the status of nickel ions and electrochemical performance was discussed. On the other hand, the capacity retention rates are 91.7, 96.6, and 98.0 % after 50 cycles at 0.1 C and at 100 %DOD, 80 DOD, and 50 %DOD.

Fluorocarbon surfactant (potassium nonafluoro-1-butanesulfonate) is employed to prepare the Nafion/fluorocarbon (N/FC) membranes for all vanadium redox flow batteries (VRFB). N/FC membranes with different FC surfactant mass ratios were successfully prepared by a solution casting method. The addition of FC surfactant has effectively suppressed the vanadium ions permeability and improved the proton conductivity of Nafion. The N/FC membrane with 5 wt% of FC surfactant (N/FC—5%) exhibits the highest ion selectivity (ratio of proton conductivity to permeability) of 2.0×10 6 S min cm −3 , which is 2.1 times higher than that of pure recast Nafion (r-Nafion) membrane (9.7×10 5 S min cm −3 ). Consequently, both coulombic efficiency ( CE ) and voltage efficiency ( VE ) of the VRFB with N/FC—5% membrane are higher than that of the VRFB with r-Nafion membrane. The average energy efficiency (product of CE and VE ) of the VRFB with N/FC—5% membrane is 11% higher than that of the VRFB with r-Nafion at current density of 40–80 mA cm −2 .

Ultra-thin and high performance polytetrafluoroethene (PTFE)/Nafion/silica composite membrane has been successfully prepared by solution casting and sol–gel method for all vanadium redox flow battery (VRB). Thickness of ∼25 μm polytetrafluoroethene/Nafion (P/N) membrane is first prepared by impregnating porous PTFE membrane with Nafion solution, and then the P/N membrane is immersed in tetraethoxysilane (TEOS) solution to prepare PTFE/Nafion/silica (P/N/S) composite membranes. The chemical structures of membranes are investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), which prove that the Nafion resin and silica are well impregnated in PTFE membrane. The water uptake, proton conductivity, vanadium permeability and VRB single cell tests of the composite membrane are also investigated in detail. At 80 mA cm−2, coulombic efficiency, voltage efficiency and energy efficiency of the VRB with P/N/S-7 (7 wt.% SiO2 in P/N/S) membrane are 93.9%, 87.2% and 81.9%, respectively. Furthermore, the self-discharge rate of the VRB with P/N/S membrane is much slower than that of the VRB with P/N membrane, which indicates that the membrane has good vanadium block ability. Fifty cycles charge–discharge test proves that the P/N/S membrane is very stable and possesses high chemical stability under the strong acid solutions.

To reduce the consumption and improve the performance of Nafion, a thin polytetrafluoroethene (PTFE)/Nafion (P/N) composite membrane for vanadium redox flow battery (VRB) application was prepared by impregnating porous PTFE membrane with Nafion solution. The P/N membrane is almost as transparent as commercial Nafion 212 (N212) membrane, which can be easily cut into any desired shape and size. SEM and AFM analyses prove that the Nafion resin uniformly filled into the micro-pores of porous PTFE membrane. Results also show that the swelling ratio, Nafion consumption, water transport and vanadium ions permeability of P/N membrane are smaller than that of N212. The VRB with P/N membrane has higher coulombic efficiency, voltage efficiency and energy efficiency than that of N212 at all tested current densities, and the average EE of VRB with P/N membrane is 5.2% higher than that of the VRB with N212 at current densities from 40 to 70 mA cm −2 . Furthermore, owing to the lower vanadium ions permeability, the self-discharge of the VRB with P/N membrane is much slower than that of the VRB with N212, and 45 cycles charge–discharge test proves that the P/N membrane is very stable and has better capacity retention ability than that of N212.

Solution casting method was adopted using Nafion and polytetrafluoroethylene (PTFE) solution to prepare Nafion/PTFE blend membranes for vanadium redox flow battery application. The physicochemical properties of the membranes were characterized by using water uptake, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis (TA). The electrochemical properties of the membranes were examined by using electrochemical impedance spectroscopy (EIS) and single cell test. Despite the high miscibility of PTFE with Nafion, the addition of hydrophobic PTFE reduces the water uptake, ion exchange capacity (IEC) and conductivity of blend membranes. But PTFE can increase the crystallinity, thermal stability of Nafion/PTFE membranes and reduce the vanadium permeability. The blend membrane with PTFE (30 wt%, N0.7P0.3) was chosen and investigated for VRB single cell test. The energy efficiency of this VRB with N0.7P0.3 membrane was 85.1% at current density of 50 mA cm−2, which was superior to that of recast Nafion (r-Nafion) membrane (80.5%). Self-discharge test shows that the decay of open circuit potential of N0.7P0.3 membrane is much lower than that of r-Nafion membrane. More than 50 cycles charge–discharge test proved that the N0.7P0.3 membrane possesses high stability in long time running. Chemical stabilities of the chosen N0.7P0.3 membrane are further proved by soaking the membrane for 3 weeks in highly oxidative V(V) solution. All results suggest that the addition of PTFE is a simple and effective way to improve the performance of Nafion for VRB application.

In order to further decrease the cost and enhance the durability of sulfonated poly(ether ether ketone) membrane for vanadium redox flow battery, a super thin (40 μm) polytetrafluoroethylene (PTFE)/SPEEK (PS) membrane is prepared. The physico-chemical properties and single cell performance of PS membranes prepared with different casting solvents including NMP (N-methyl-2-pyrrolidone), DMF (N,N′-dimethylformamide), and DMAc (N,N′-dimethylacetamide) have been investigated. Results show that the energy efficiency of VRB with PS/DMF can reach up to 91.2% at the current density of 40 mA cm−2, which is 11.1% and 6.4% higher than that of the commercial Nafion 212 and pristine SPEEK membrane, respectively. In addition, charge–discharge test over 150 times proves that the PS/DMF membrane possesses high stability and thus it is suitable for VRB application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43593.

Li3V2−xSnx(PO4)3/C cathode materials with uniform and fine particle sizes were successfully and fast synthesized by a microwave solid-state synthesis method. X-ray diffraction patterns demonstrated that the appropriate addition of Sn did not destroy the lattice structure of Li3V2(PO4)3/C, but decreased the unit cell volume. X-ray photoelectron spectroscopy analysis demonstrated that the main chemical state of V in the Li3V1.95Sn0.05(PO4)3/C composite is +3 valence, while the chemical state of Sn in the Li3V1.95Sn0.05(PO4)3/C is +4 valence. Scanning electron microscope analysis illustrated that the addition of Sn slightly affected the morphology of samples. As the cathode materials for Li-ion batteries, Li3V2−xSnx(PO4)3/C (x ⩽ 0.10) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5 C in the potential range of 2.5–4.5 V at room temperature, the initial discharge capacity of Li3V1.95Sn0.05(PO4)3/C was 136 mA h/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Sn-doped Li3V2(PO4)3/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Sn doping in Li3V2(PO4)3/C system by enhancing structural stability and electrical conductivity. The present study also demonstrates that the microwave processing is a fast, simple and useful method for the fabrication of Li3V2(PO4)3/C crystals.

A novel Nafion-sulfonated diphenyldimethoxysilane (N-sDDS) composite membrane is prepared and employed in vanadium redox flow battery (VRB). Ion exchange capacity, proton conductivity, water transport behavior, and the cell performances are characterized. Fourier transform-infrared and X-ray diffraction analysis indicate that the sulfonated diphenyldimethoxysilane (sDDS) particles are successfully introduced into the Nafion matrix. In VRB single cell test, the VRB with N-sDDS membrane exhibits nearly the same coulombic efficiency as the unmodified Nafion membrane, but higher voltage efficiency than that of the VRB with unmodified Nafion membrane. The VRB with N-sDDS composite membrane keeps a stable performance after 60 times charge–discharge test. In the self-discharge test, the VRB with the N-sDDS membrane presented a lower self-discharge rate than that of the VRB with Nafion membrane. All results show that the addition of s-DDS is a simple and efficient way to improve the conductivity of Nafion, and the composite membrane shows good potential use for VRB.

Cu2O with S as additive electrode using Ni foam as the substrate is prepared in Mg–Cu2O seawater battery. The morphology and electrochemistry performance of electrode are investigated. The excellent electrochemical properties of Ni foam-supported electrode indicate that it is suitable for seawater devices. The cell voltage of Mg–Cu2O seawater batteries is elevated by sulphur addition. Sulphur participates in the electrochemical reactions; the elevation in cell voltage is 200–350 mV according to the ratio of Cu2O to S.

In our previous work, Nafion/SiO(2) hybrid membrane was prepared via in situ sol-gel method and used for the vanadium redox flow battery (VRB) system. The VRB with modified Nafion membrane has shown great advantages over that of the VRB with Nafion membrane. In this work, a novel Nafion/organically modified silicate (ORMOSIL) hybrids membrane was prepared via in situ sol-gel reactions for mixtures of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS). The primary properties of Nafion/ORMOSIL hybrids membrane were measured and compared with Nafion and Nafion/SiO(2) hybrid membrane. The permeability of vanadium ions through the Nafion/ORMOSIL hybrids membrane was measured using an UV-vis spectrophotometer. The results indicate that the hybrids membrane has a dramatic reduction in crossover of vanadium ions compared with Nafion membrane. Fourier transform infrared spectra (FT-IR) analysis of the hybrids membrane reveals that the ORMOSIL phase is well formed within hybrids membrane. Cell tests identify that the VRB with Nafion/ORMOSIL hybrids membrane presents a higher coulombic efficiency (CE) and energy efficiency (EE) compared with that of the VRB with Nafion and Nafion/SiO(2) hybrid membrane. The highest EE of the VRB with Nafion/ORMOSIL hybrids membrane is 87.4% at 20mA cm(-2). while the EE of VRB with Nafion and the EE of VRB with Nafion/SiO(2) hybrid membrane are only 73.8% and 79.9% at the same current density. The CE and EE of VRB with Nafion/ORMOSIL hybrids membrane is nearly no decay after cycling more than 100 times (60mA cm(-2)), which proves the Nafion/ORMOSIL hybrids membrane possesses high chemical stability during long charge-discharge process under strong acid solutions. The self-discharge rate of the VRB with Nafion/ORMOSIL hybrids membrane is the slowest among the VRB with Nafion, Nafion/SiO(2) and Nafion/ORMOSIL membrane,which further proves the excellent vanadium ions blocking characteristic of the prepared hybrids membrane. (c) 2008 Elsevier B.V. All rights reserved.

Li3V2-xSnx(PO4)3/C (x = 0, 0.01, 0.02, 0.05, 0.10) cathode materials are synthesized by a microwave-assisted solid state reaction starting with mixtures of LiOH·H2O, V2O5, NH4H2PO4, SnO2, and sucrose (Ar flow, 300 °C for 3 h followed by microwave heating at 750 °C for 15 min).

The crossover of vanadium ions through proton-exchange membranes such as those of Nafion is the chief reason that results in the low energy efficiency and high self-discharge rate of vanadium redox flow batteries (VRB). With respect to applicability, the ideal proton-exchange membrane used in VRB should possess simultaneously high proton conductivity and low vanadium ion permeability. Here, we report a novel approach using a polyelectrolyte layer-by-layer self-assembly technique to fabricate a barrier layer onto the surface of Nafion membrane by alternate adsorption of polycation poly(diallyldimethylammonium chloride) (PDDA) and polyanion poly(sodium styrene sulfonate) (PSS), which can suppress the crossover of vanadium ions. The Nafion–[PDDA-PSS]n membrane (n = the number of multilayers) obtained shows much lower vanadium ion permeability compared with plain Nafion membrane. Accordingly, the VRB with Nafion–[PDDA-PSS]n membrane exhibits a higher coulombic efficiency (CE) and energy efficiency (EE) together with a slower self-discharge rate than that of Nafion system. The highest CE of 97.6% and EE of 83.9% can be achieved at charge–discharge current density of 80 mA cm−2 and 20 mA cm−2, respectively.