Kind Of Electrolyte Research Articles

The Effect of Additives on the Trap States Distribution of TiO2 Anode in Dye-Sensitized Solar Cell (DSSC)

1.Introduction Dye-sensitized solar cell (DSSC) has been studied in the past two decades because of its high cost-efficiency characteristic. It is well known that the electrons recombination behaviors related to the trap states on the interface between anode and electrolyte are very important to decide the performance of DSSC. It has been reported that the cells with different additives have different trap states distribution on TiO2 anode.[1][2] Among the additives, 4-tert-Butylpyridine (4-tBP) is the most popular used one. It is generally considered to upshift the band edge of TiO2 anode which can increase the Voc and form blocking layer to reduce the electrons recombination. Considering the adsorption competition between dye and additives, we prepared the cells with different amount of dye adsorption and composition of additives on the TiO2 to study the relationship between the trap states distribution and the surface attachments. In this study, N719 dye and the electrolyte with same solvent (3-MPN) but different composition (4-tBP+DMPII and DMPII only) are applied for the cells. The trap states distribution was evaluated by measuring the chemical capacitance (Cμ) obtained from impedance measurement. 2.Experimental The TiO2 anode used for experiments was solaronix 74101 (thickness: 9μm main layer and 5μm scattering layer, area: 6mm6mm, provided by solaronix). TiO2 anode was Preheated at 500℃ for 30mins and kept at 120 ℃ to ensure no water adsorbed on TiO2 surface before dye soaking. The TiO2 anode was soaked into N719 dye solution (dissolved in acetonitrile) at the concentration from 0.1mM to 0.5mM for 4-10 hours. Two kinds of electrolyte: electrolyte tBP (0.05M I2, 0.1M LiI, 0.6M DMPII, 0.5M 4-tBP) and electrolyte no tBP (0.05M I2, 0.1M LiI, 0.6M DMPII) were applied for the cells. The excitation using AM1.5 solar simulator and monochromatic LED lights (627nm) were adopted in this study to analyze the characteristic of trap states distribution for different cells. The impedance was measured under the AM1.5 solar simulator at the intensity of 100mW/cm2 and LED light source at the range from 19.1mW/cm2 to 72.8mW/cm2. After impedance measurement, IMVS and IMPS measurement were applied to calculate the collection efficiency. The N719 dye adsorbed on TiO2surface was taken off by 0.5M KOH solution, and the UV-vis was applied to evaluate the amount of dye adsorption through N719/KOH solution. 3.Result By the comparison of cells with same electrolyte but different amount of dye adsorption, it is found that Cμ increase with the increase of dye adsorption. On the other hand, for the cells with similar amount of dye adsorption, the cells without 4-tBP showed a higher Cμcompared with those with 4-tBP. Interestingly, by the measurement of IMVS and IMPS, cells with 4-tBP have lower collection efficiencies compare with those without 4-tBP regardless of the dye adsorption as shown in the fig indicating higher recombination in case of adding 4-tBP into the electrolyte. These results will be further explained by the impedance analysis. Also, further study will be focus on clarifying the relationship between trap states distribution and additives attachment. Acknowledge: This work partially was supported by Center for Low Carbon Society Strategy (LCS) in the Japan science and Technology Agency (JST) and Shin-Etsu Chemical Co., Ltd. Japan. Their contribution is greatly appreciated. Reference: [1] Raga S R, Barea E M, Fabregat-Santiago F. Analysis of the origin of open circuit voltage in dye solar cells[J]. The journal of physical chemistry letters, 2012, 3(12): 1629-1634. [2] Fabregat-Santiago F, Bisquert J, Garcia-Belmonte G, et al. Influence of electrolyte in transport and recombination in dye-sensitized solar cells studied by impedance spectroscopy[J]. Solar Energy Materials and Solar Cells, 2005, 87(1): 117-131. Figure 1

Effect of electrostatic correlations on micelle formation

Micellization phenomena are fundamental to countless biological and chemical processes. Salts can dramatically change the micellization, depending on the kind of electrolyte and its concentration. Traditional approaches to model and describe these phenomena do not take into account electrostatic correlation interactions. Those interactions are essential when modeling surfactant solutions containing multivalent and/or highly concentrated electrolytes. Therefore, the development of a theory that is able to correctly predict the behavior of surfactant solutions with salts is a key to improve the application of surfactants in industrial processes. Here, we propose a simple methodology that uses a mean field approach to include electrostatic correlation effects and we coupled it with the well-established molecular thermodynamics approach to describe the micellization phenomena. From the proposed model, we can obtain the critical micelle concentration (CMC) of ionic and zwitterionic surfactant solutions and information about the size and shape of the micelles. We also propose an approach to take into account the binding of cations and anions on the surface of zwitterionic surfactants. To validate the model we compared our results with experimental data of CMC and counterion binding for different surfactants. We obtained very good agreement with the experimental data with a completely predictive model.

Effect of iron oxide impregnated in hollow carbon sphere as symmetric supercapacitors

Iron oxide impregnated hollow carbon spheres (HCS-Fe3O4) samples were fabricated by impregnating Fe(NO3)3 into hollow carbon spheres (HCS) through an incipient wetness procedure and subsequent heat treatment. Through controlling the amount of iron species stored in HCS, different samples were selectively prepared. Pristine HCS and the samples with different Fe3O4 loading (HCS-Fe3O4-1, HCS-Fe3O4-2 and HCS-Fe3O4-3) were characterized by TEM, XRD, TGA and N2 adsorption/desorption isotherms in detail, respectively. As electrode materials of supercapacitor, their capacitive performances have been investigated by CV, galvanostatic charge/discharge and EIS measurements in two-electrode system using different kinds of electrolytes. Owing to the optimal pore size and partially filled cavity structure, electrolyte ions exhibit easy and reversible transport through HCS-Fe3O4-2. So that HCS-Fe3O4-2 presents the highest specific capacitance of 193 F g−1 at a scan rate of 1 mV s−1 and retains 94.75% up to 10,000 cycles. The capacitance performance of this material tested by symmetric system showed even higher value than the results by three-electrode system from some other researches, indicating the potential applications of HCS-Fe3O4-2 in industrial and energy field.

Application of Box-Behnken designs in parameters optimization of differential pulse anodic stripping voltammetry for lead(II) determination in two electrolytes

Box-Behnken design was advantageous to parameters optimization of differential pulse anodic stripping voltammetry (DPASV) for the analysis of lead(II) with its high efficiency and accuracy. Five Box-Behnken designs were designed and conducted in the electrolyte of 0.1 mol/L acetate buffer and 0.1 mol/L HCl without the removal of oxygen. Significant parameters and interactions in each electrolyte were found (P-value < 0.05) and their quantitative effects on lead(II) determination were classified into two categories, linear and quadratic. Though significant parameters and interactions were not similar in different kinds of electrolytes, characteristic parameters of differential pulse voltammetry, which were pulse amplitude, pulse width and interval time, were found significant in both electrolytes. After optimization, peak currents and relative standard deviation at 20 μg/L along with detection limits in both electrolytes were superior than before. With the lower detection limit and R.S.D., 0.1 mol/L HCl was a better choice for electrolytes in this work. Meanwhile, with the combination of parameters optimization and background subtraction, the interference of dissolved oxygen for lead(II) determination was eliminated. It was important and necessary to apply Box-Behnken designs in parameters optimization of DPASV for lead(II) determination regardless of the electrolyte kinds.

Effects of Surface Oxygenic Functional Groups on the Electrochemical Properties of Supercapacitor

The surface oxygenic functional groups are significant to the capacity and cycle stability of supercapacitor. Coconut shell-based activated carbon (CS) with high surface oxygen content was used as starting material and reduced by hydrogen. The measurement results of microstructure showed that the specific surface area and total pore volume increased a little. While the surface oxygen content decreased greatly according to the results of X-ray photoelectron spectroscopy (XPS). Electrochemical behaviors of the electrode built with CS and hydrogen reduced CS (HCS) were investigated in two kinds of electrolytes, 6 mol L-1 KOH and 1 mol L-1 Et4NBF4/PC, respectively. The results showed that the surface oxygen groups have little influence to the electrochemical properties of supercapacitor in KOH electrolyte. As for supercapacitor in Et4NBF4/PC, HCS presents higher specific capacitance, higher energy density, better capacity retention and lower leakage current than those of original CS. This indicates that the surface oxygenic functional groups have reaction and impediment to the organic electrolyte. The study not only provides a simple and effective method for large-scale and safe application of supercapacitors using organic electrolyte, but also offers a better understanding of the action of surface functional groups on the electrochemical performances of porous carbon materials.

Recent progress in Li–S and Li–Se batteries

Li–S and Li–Se batteries have attracted tremendous attention during the past several decades, as the energy density of Li–S and Li–Se batteries is high (several times higher than that of traditional Li-ion batteries). Besides, Li–S and Li–Se batteries are low cost and environmental benign. However, the commercial applications of Li–S and Li–Se batteries are hindered by the dissolution and shuttle phenomena of polysulfide (polyselenium), the low conductivity of S (Se), etc. To overcome these drawbacks, scientists have come up with various methods, such as optimizing the electrolyte, synthesizing composite electrode of S/polymer, S/carbon, S/metal organic framework (MOF) and constructing novelty structure of battery. In this review, we present a systematic introduction about the recent progress of Li–S and Li–Se batteries, especially in the area of electrode materials, both of cathode material and anode material for Li–S and Li–Se batteries. In addition, other methods to lead a high-performance Li–S and Li–Se batteries are also briefly summarized, such as constructing novelty battery structure, adopting proper charge–discharge conditions, heteroatom doping into sulfur molecules, using different kinds of electrolytes and binders. In the end of the review, the developed directions of Li–S and Li–Se batteries are also pointed out. We believe that combining proper porous carbon matrix and heteroatom doping may further improve the electrochemical performance of Li–S and Li–Se batteries. We also believe that Li–S and Li–Se batteries will get more exciting results and have promising future by the effort of battery community.

Ionic liquid-based electrolyte with dual-functional LiDFOB additive toward high-performance LiMn2O4 batteries

Manganese oxide-based cathodes are one of the most promising lithium-ion battery (LIB) cathode materials due to their cost-effectiveness, high discharge voltage plateau (above 4.0 V vs. Li/Li+), superior rate capability, and environmental benignity. However, these batteries using conventional LiPF6-based electrolytes suffer from Mn dissolution and poor cyclic capability at elevated temperature. In this paper, the ionic liquid (IL)-based electrolytes, consisting of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfon)imidate (PYR1,4-TFSI), propylene carbonate (PC), lithium bis(trifluoromethanesulfon)imide (LiTFSI), and lithium oxalyldifluoroborate (LiDFOB) additive, were explored for improving the high temperature performance of the LiMn2O4 batteries. It was demonstrated that LiTFSI-ILs/PC electrolyte associated with LiDFOB addition possessed less Mn dissolution and Al corrosion at the elevated temperature in LiMn2O4/Li batteries. Cyclic voltammetry and electrochemical impedance spectroscopy implied that this kind of electrolyte also contributed to the formation of a highly stable solid electrolyte interface (SEI), which was in accordance with the polarization measurement and the Li deposition morphology of the symmetric lithium metal cell, thus beneficial for improving the cycling performance of the LiMn2O4 batteries at the elevated temperature. Cyclic voltammetry and electrochemical impedance spectroscopy implied that the cells using this kind of electrolyte exhibited better interfacial stability, which was further verified by the polarization measurement and the Li deposition morphology of the symmetric lithium metal cell, thus beneficial for improving the cycling performance of the LiMn2O4 batteries at the elevated temperature. These unique characteristics would endow this kind of electrolyte a very promising candidate for the manganese oxide-based batteries.

In Situ Observation of Critical Phenomena of Multicomponent Geofluids and Seawater by Using Visible-type Autoclave

Spectroscopic characteristics of critical phenomena of multicomponent geofluids and seawater were observed by using autoclave with transparent windows (visible-type autoclave). First, pure H2O fluids were observed by spectroscopic measurements at 500–800nm under high temperature and pressure conditions. The intensity of light transmitted decreased significantly as the critical point of H2O fluid was approached, and the local minimum intensity of transmitted light corresponded to the critical temperature and pressure of all fluids tested. The experimentally determined critical temperature and pressure of H2O were similar to the results of previous work. Critical temperatures and pressures of multicomponent geofluids and seawaters were determined. Spectroscopic measurement could provide information of molecular behaviours of aqueous fluid involving several kinds of electrolytes.

Application of ionic liquid in metal-air battery

Metal-air battery is an important direction in the field of electric vehicle technology development since it has high energy density, low cost, no pollution and can be recycled. Ionic liquid becomes a new kind of electrolytes in the field of metal-air battery since it has high thermal stability, wide electrochemical window, negligible vapor pressure and can be recycled easily. The problems existing in the traditional solution system such as the low energy conversion efficiency and electrolyte evaporation, are expected to be solved if the ionic liquids are used as electrolyte in metal-air battery. The common anodes of metal-air battery are lithium (Li), zinc (Zn), magnesium (Mg), aluminum (Al), sodium (Na) and silicon (Si). In this paper, progress and challenges in the application of ionic liquids as electrolyte in these six kinds of metal-air batteries and its future development direction are discussed.

Linear stability of buoyant convective flow in a vertical channel with internal heat sources and a transverse magnetic field

Linear stability of buoyant convective flow of an electrically conducting fluid in a vertical channel owing to internal heat sources has been studied. The flow takes place in a transverse, horizontal magnetic field. The results show that up to four different local minima may be present in the neural stability curve. Up to two of these modes may be the most unstable depending, critically, on the value of the Hartmann number. Over a wide range of moderate to high Hartmann numbers, thermal waves dominate the instability. As the Hartmann number increases, however, this mode is strongly damped. Then the so-called Hartmann mode takes over, which involves the characteristic Hartmann layers at the walls appearing due to modification of the basic velocity profile by the magnetic field. Overall, for liquid metals at high magnetic fields, the basic flow is very stable. Variation of the Prandtl number in a wide range has also been performed as, depending on the type of an electrically conducting fluid (liquid metal or various kinds of electrolytes), the Prandtl number varies over several orders of magnitude. As may be expected, the increase of the Prandtl number lowers the instability threshold for the thermal waves.

Carbon Nanotube Composite Electrodes Toward All Solid Alkali Metal Ion Batteries

Owing to the superior energy density, rechargeable Li-ion batteries (LIBs) have been used as a major power source of portable electric devices such as cell phones and lap-top computers. In addition to small-scale applications, LIBs are also installed in recently developed large scale systems such as electric vehicles (EVs), renewable energy storage systems, and smart grids. In commercially available LIBs, rare metal oxides, such as LiCoO2 and LiMnO4 are used for the cathode material. However, the capacity of LIB is not large enough for EV with long driving range. Furthermore, rare metals used in the present LIB such as Co, Ni and Li raise the cost of LIB. Therefore, we have to explore new electrode materials having high ion adsorption capacity and available at low cost so as to develop long driving range EV. Phosphorus is a candidate for such an electrode materials, because phosphorus is one of the ubiquitous elements and can adsorb much alkali metal ions. However, most of the polymorphs of phosphorus except for black phosphorus, which is prepared by high pressure and high temperature treatment, are electric insulators. We also take large volume change of phosphorus electrode with ion adsorption into account. Single-walled carbon nanotube (SWCNT) has good electric conductivity and huge hollow core space in which some molecules can be encapsulated. Therefore, if we input phosphorus molecules into the hollow core of SWCNT, the materials would work as a good electrode. In fact, it was found by our preliminary experiments that phosphorus encapsulated in SWCNT (P@SWCNT) can adsorb and desorb alkali metal ions such as Li and Na [1]. However, since the experiments were performed under limited conditions, we should perform more sophisticated experiments to examine the electrode properties of P@SWCNT more precisely. In this study, we discuss how the electrode property of P@SWCNT changes with different kinds of electrolytes. In the previous work, we used mixture of Ethylene Carbonate and Diethyl Carbonate (EC/DEC) as an electrolyte. In the present study, we prepared two different kinds of electrolytes: Propylene Carbonate (PC) and polyethyleneoxide based composite polymer electrolyte (PEO). The former has wide liquid temperature range and shows very good low temperature performance than EC/DEC solvent and high conductivity thus we can try to evaluate electrode material at low temperature. The latter is known for one of the solid electrolyte and show from 10-3 to 10-4 S/cm at over 60 degrees Celsius. In the symposium, we’ll discuss the electrode properties of P@SWCNT with different kinds of electrolyte and also talk about the possibility of all solid state battery using P@SWCNT.

Molecular Modeling of Energy Barrier of Li Ion Transport from Negative to Positive Electrodes

Lithium ion battery is used as a main power supply of a small portable device and large power supplies for electric cars. For further applications, however, an improvement in battery performance from materials level based on rational design of Li ion transport in the battery is needed. In this study, we carried out systematic analysis of energy barrier of Li ion transport from anode to cathode materials using first-principles molecular dynamics and classical molecular dynamics. First, we calculated the energy barrier of diffusion of Li ion through several kinds of electrolyte. To validate the accuracy of calculated transport properties, diffusion coefficients and activation energies for diffusion of ions in LiPF6-DEC-EC at different temperature (-20 ℃ – 20 ℃) and ratio of DEC/EC are compared with experimental data and confirmed the reasonable agreement. Furthermore, the solvation energy of Li ion in electrolytes as well as the salvation structure were investigated by density functional theory and classical molecular dynamics. First principles molecular dynamics and density functional theory were used to calculate the adsorption energy and activation energy fir diffusion of Li ion in cathode materials such as LiCoO2. From these analysis, we conclude that the solvation energy, which is more than 50 kcal/mol for EC/DEC system, is the highest energy barrier for transport of Li ion of which would be the limited step for Li ion transport although it depends on the condition. We also investigated the influence of these transport properties to the battery performance (I-V curve). We will present more concrete data regarding Li ion transport at the conference.

Si-O-C Composites Prepared By Electrodeposition on CNTs/Cu or Carbon Paper Substrate and Electrochemical Performance for Lithium Ion Battery

Silicon have been attracted as promising anode material because of its higher theoretical capacity than commercial graphite (silicon: 4200 mA h g-1, graphite: 372 mA h g-1). We have been reported the novel Si-O-C composite as anode for lithium secondary batteries with high discharge capacity around of 1045 mA h (g of Si)-1 at 2000th cycle and 842 mA h (g of Si)-1 with outstanding cycle ability over 7200 cycles. Nevertheless, it is not easy to increase the thickness of Si-O-C composite for higher areal capacity due to its weak adhesion strength between Si-O-C with current corrector. To solve this problem, we reported the nickel micro-nanocones hierarchical structured (MHS) substrate and carbon nanotubes (CNTs) covered Cu substrate, and Si-O-C was deposited on those of current collectors, resulting in improved areal capacity and deposited Si amounts, 600 mA h cm-1 with Si-O-C deposited on MHS substrate and enhanced deposited Si amounts up to 16.7 % by CNTs/Cu substrate. In this research, the Si-O-C deposited on to CNTs/Cu substrate was used as anode for full-cell test with LiCoO2 (LCO) cathode. The loading amounts of LCO and Si-O-C were controlled to find optimum loading amounts for good-balanced LCO//Si-O-C full cell. Besides, to enhance the areal capacity, carbon paper (CP) which has three-dimensional structure was used as current collector. The Si-O-C/CP was prepared by electrodeposition with two kinds of electrolytes, in PC and EC/DEC bath. Material and electrochemical properties of Si-O-C/CP was measured by FE-SEM, raman spectrum, inductively coupled plasma, and charge/discharge test by half-cell. Acknowledgements This work was partly supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)” from Japan Science and Technology Agency (JST), Japan.

Phosphoric Acid Tolerant Oxygen Reduction Reaction Catalysts for High-Temperature Polymer Electrolyte Fuel Cells

Operating polymer electrolyte fuel cells (PEFCs) at temperatures of above 100 °C can be beneficial over low-temperature operation. However, different operating temperatures require also different kinds of electrolytes. For operating PEFCs at temperature in-between 150 and 200 °C, typically phosphoric acid doped polybenzimidazole is the electrolyte of choice. Unfortunately, state-of-the-art platinum catalysts are deactivated by adsorption of phosphate species on their active catalyst sites, thus the overall performance of the fuel cell system drops. In order to overcome this hurdle, it is necessary to identify suitable catalyst systems with high tolerance towards phosphate poisoning.

The Negative Effect of Cyclic Carbonate-Based Electrolyte on the Electrochemical Performance of Copper Sulfides

Copper sulfides are attractive electrode materials for lithium-ion battery because of their high capacity and energy density. Interestingly, the cycling stability of copper sulfides is poor in the carbonate-based electrolyte but excellent in ether-based electrolyte. The reasons for the different electrochemical performance in these two kinds of electrolyte need to be further investigated. In this study, we have compared the electrochemical performance of Cu2S electrodes in various kinds of carbonate-based electrolyte and the results show that the cyclic carbonate-based electrolyte is a major factor contributing the limited stability. Experiments were done by using commercially available copper sulfides as the electrode material. Some linear carbonate (DMC, EMC) and cyclic carbonate (FEC, PC, VC, EC) were tested as the electrolytes in different compositions. Our results show that the capacity of the Cu2S electrode fades quickly in cyclic carbonate-based electrolytes, but shows a much better electrochemical performance in linear carbonate-based electrolytes. In EMC (1 M LiPF6), it can show a discharge-capacity of 242.8 mAhg-1 with coulombic efficiency of 99.6% after 50 cycles. (As shown in Figure 1 and Table 1) Our study firstly finds that the copper sulfides electrodes can obtain excellent electrochemical performance in carbonate-based electrolyte without any special nanostructure. And the theoretical work was used to reveal the real reason of the negative effect of cyclic carbonate-based electrolyte for the first time. (As shown in Figure 2 and Table 2). From the data as shown in Figure 2 and Table 2, we can draw a conclusion that it is more difficult for nucleophilic attack reaction on linear-based carbonate due to the change of the Gibbs free energies for reaction (b) is a positive value. At the same time, the total energy of the cyclic carbonate molecules is higher than the related energies of linear carbonate molecules which also show that the cyclic carbonate molecules are more unstable. All these indicate that the electrolyte composed of cyclic structure (take FEC, PC, VC and EC for example) may easily react with nucleophilic anions and which is related to the negative effects on the electrochemical performance of copper sulfides. On the basis of the electrochemical study, we can conclude that there is a negative effect of cyclic carbonate-based electrolyte on the electrochemical performance of copper sulfide electrodes. Additional theoretical work for this study reveals the real reason of the negative effect of cyclic carbonate-based electrolyte for the first time. Fig. 1 (a) Discharge–charge profiles of the Cu2S electrode at first cycle in different electrolyte, (b) cycle performance of the Cu2S electrode in different electrolyte, all the experiments are tested between 1.0 and 3.0 V vs. Li/Li+ at a rate of 0.5 C (1 C = 335 mAh g-1). Table. 1 The first columbic efficiency and the capacity retention of Cu2S electrode in various composition of electrolytes at room temperature. Compsition of electrolytes The first columbic efficiency capacity retention 10th 20th 50th 1 M LiPF6 in DMC 92.6% 86.0% 77.3% 55.5% 1 M LiPF6 in EMC 95.2% 95.4% 88.4% 76.5% 1 M LiPF6 in FEC 79.0% 1.3% 0.9% 0.3% 1 M LiPF6 in PC 91.5% 5.8% 1.9% 1.1% 1 M LiPF6 in VC 78.4% 1.1% 0.9% 0.8% 1 M LiPF6 in EC 74.2% 1.3% 0.8% 0.6% Fig. 2 Proposed Reactions between S4 2- and Carbonates. Species EC DMC S4 2- 1 2 °÷G (a) °÷G (b) G(Hartree/Particle) -342.35 -343.55 -1592.68 -1935.09 -1935.67 -0.05 0.56 Table. 2 Gibbs free energies of the solvents and the change of the Gibbs free energies for reaction. Figure 1

Impact of the Water Content in Glyme-Based Electrolyte to Rechargeable Magnesium-Organic Battery

Rechargeable magnesium battery can be a candidate of the next-generation batteries because magnesium has a higher volumetric capacity, is more abundant in terms of the resources, and is less reactive in air than lithium. We previously found that a redox-active organic compound, 2,5-di­methoxy-1,4-benzo­quinone (DMBQ), has the potential to serve as the positive electrode material for the Mg system1. Recently, we have investigated two kinds of electrolytes, sulfone-based and glyme-based electrolytes2-3, for the rechargeable magnesium-organic batteries. In the case of monoglyme-based electrolyte, the discharge voltage of the Mg-DMBQ cell significantly increases, not decreases, after a few cycles, for which, we found, a decrease in the overpotential for the Mg dissolution upon cycling is responsible3. However, what caused the decrease in the overpotential on the Mg negative electrode is not clear. In the present study, we report the impact of the water content in the monoglyme-based electrolyte to the rechargeable Mg-organic battery. Magnesium bis(trifluoromethane sulfonyl)amide (Mg(TFSA)2) and monoglyme were purchased from Kishida Chemical and used without further purification. The electrolyte was prepared by dissolving 0.5 mol L-1 of Mg(TFSA)2 in monoglyme. The water content of the as-prepared electrolyte was 40 ppm. Two other electrolyte solutions were prepared in which pure water was deliberately added to 100 and 1000 ppm. The electrochemical cells were set up and tested based on our previous study3. The specific conductivities of water-added 0.5 mol L-1 Mg(TFSA)2/monoglyme did not shift from that of the as-prepared. The discharge and charge curves of the cells in the electrolytes at various water contents showed that in all three cases the first discharge curve has two potential plateaus below 0.7 V. In the case of the water-added electrolytes, the discharge voltage during the second cycle significantly increased, while in the as-prepared electrolyte the discharge voltage remained below 0.7 V even after several cycles. The drastic dissolution of Mg from the surface of the negative electrode was observed by SEM only in the water-added electrolytes. A certain amount of water plays an important role in preparing the surface of the electrode to let Mg dissolve in the electrolyte. 1. H. Sano et al., Chem. Lett., 41, 1594 (2012). 2. H. Senoh et al., J. Electrochem. Soc., 161, A1 (2014). 3. H. Senoh et al., ECS Transactions, in press.

Graphene-cellulose tissue composites for high power supercapacitors

Flexible supercapacitors have aroused a great deal of interest for their integration in portable, flexible and wearable electronic devices. In this context, graphene has emerged as an excellent building block for the fabrication of flexible electrodes. However, free-standing graphene films suffer from a certain lack of mechanical resistance, which limits their use. In this paper, we report on the fabrication of free-standing and flexible composites with enhanced robustness, consisting of a graphene layer deposited over a porous cellulose tissue. The coated graphene consists of two types of holey graphene units (i.e. wrinkled graphene sheets and graphene nanoscrolls) that produce closely interconnected and porous 3D graphene architectures. The graphene-tissue composites developed here have a thickness of around 60µm and areal densities in the 0.6–2.4mgcm−2 range. These composites have a very open structure that provides easy access to the electrolyte, thereby guaranteeing high ion-transport rates. In consequence, they show a remarkable capacitive performance in both liquid (1M H2SO4) and solid (PVA-H2SO4) electrolytes. The supercapacitors assembled with these materials possess an areal capacitance of up to ~80mFcm−2 at low rates in both kinds of electrolyte and around 60mFcm−2 at 500mAcm−2 in H2SO4 and 54mFcm−2 at ca. 80mAcm−2 in a gel electrolyte. What is more, these SCs are able to deliver ca. 9µWhcm−2 of energy at a high power density of 100mWcm−2.

Electrocatalytic degradation of aniline by Ti/Sb–SnO2, Ti/Sb–SnO2/Pb3O4 and Ti/Sb–SnO2/PbO2 anodes in different electrolytes

Electrochemical treatment (ECT) of bio-refractory and highly toxic aniline was investigated over Ti/Sb–SnO2, Ti/Sb–SnO2/Pb3O4 and Ti/Sb–SnO2/PbO2 anodes in Na2SO4 or NaCl electrolyte, for the purpose of finding out the most suitable electrode in the two kinds of electrolyte. The degradation performances of aniline were investigated by UV–Vis spectra, chemical oxygen demand (COD) and biochemical oxygen demand (BOD). In addition, instantaneous current efficiency (ICE) and energy consumption (Ep) for aniline degradation were also studied. Results showed that the performances of aniline electrochemical oxidation at the three electrodes were significantly different, which also relied on the electrolytes. Ti/Sb–SnO2 showed the best effect on the degradation of aniline in Na2SO4 electrolyte. The aniline and COD removal efficiency could achieve 95.9% and 91.1%, respectively, at the lowest energy consumption after 5h electrolysis. While Ti/Sb–SnO2/Pb3O4 was more capable in NaCl electrolyte. The aniline and COD removal efficiency could achieve 97.7% and 96.8%, respectively, at the lowest energy consumption after 5h electrolysis. Ti/Sb–SnO2/PbO2 had the best capability to enhance the biodegradability in the both Na2SO4 electrolyte and NaCl electrolyte. The biodegradability (BOD5/COD) could be promoted from original 0.286 to 0.498 and 0.452, respectively. Moreover, it was found that the wastewater biotoxicity was also an important parameter to study the enhance biodegradability besides the effect of ring-opening or bond breaking. Furthermore, a simple mechanism of aniline degradation was proposed.

Use of pyrocatechol violet as an effective redox additive for highly promoting the supercapacitor performances

In present work, we demonstrate a simple but effective redox additive of pyrocatechol violet (abbr. PCV) to largely promote the capacitive performances especially when carried out in three different kinds of electrolytes (H2SO4, Na2SO4 and KOH), mostly due to its fast electron and proton transfer occurring in the electrode/electrolyte interface. It reveals that the PCV dosage incorporated into electrolyte plays a crucial role in the determination of capacitive performance. When conducted in a two-electrode system, incorporating 0.06 mol L−1 PCV into 1 mol L−1 H2SO4 can achieve large capacitance up to 200 F g−1, which is almost 2.06 times than the one without the addition of PCV; besides, the corresponding energy density is of 28 Wh kg−1 (also increasing 2 times). What’s more, PCV has been extended as the redox additive in other electrolytes such as Na2SO4 and KOH, and remarkable promotion in capacitance and energy density also occur, well evincing the high efficiency and universal applicability of PCV for the large promotion of supercapacitors’ performances due to its prominent electrochemical reversibility and high solubility.

Electrochromic Devices with Ionic Liquid Based Electrolyte By Room Temperature Process

Electrochromic devices (EC), which dynamically change colour under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterials, which can provide electrochromic devices with improved coloration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. The flexible electrochromic films are promising film for applications in automobiles, buildings, etc. Here, we synthesized nanostructured tungsten trioxide (WO3) particles for electrochromic materials. The thin layers with nanostructured materials of WO3 inks were coated at room temperature, solution-processed method. For comparing the effects of electrolyte, electrochromic devices were fabricated with various kind of electrolyte, which can be optimized to obtain higher performances. Two types of polymer based electrolytes were fabricated and characterized. The operation voltages were controlled with electrolyte types and compositions. Ionic liquid based electrolyte showed higher ionic conductivity than liquid type or polymer type electrolyte. Also EC with the liquid electrolyte exhibited 40% of coloring/bleaching efficiencies and EC with the polymer gel electrolyte 60%. All solid EC could be fabricated with the polymer gel electrolyte, which exhibited the higher coloring / bleaching efficiencies than that with the liquid. The effects of composition and process variables will be discussed.