A soluble-lead redox flow battery with corrugated graphite sheet and reticulated vitreous carbon as positive and negative current collectors

A soluble-lead redox flow battery with corrugated-graphite sheet and reticulated-vitreous carbon as positive and negative current collectors is assembled and performance tested. In the cell, electrolyte comprising of 1·5 M lead (II) methanesulfonate and 0·9 M methanesulfonic acid with sodium salt of lignosulfonic acid as additive is circulated through the reaction chamber at a flow rate of 50 ml min^???1. During the charge cycle, pure lead (Pb) and lead dioxide (PbO₂) from the soluble lead (II) species are electrodeposited onto the surface of the negative and positive current collectors, respectively. Both the electrodeposited materials are characterized by XRD, XPS and SEM. Phase purity of synthesized lead (II) methanesulfonate is unequivocally established by single crystal X-ray diffraction followed by profile refinements using high resolution powder data. During the discharge cycle, electrodeposited Pb and PbO₂ are dissolved back into the electrolyte. Since lead ions are produced during oxidation and reduction at the negative and positive plates, respectively there is no risk of crossover during discharge cycle, preventing the possibility of lowering the overall efficiency of the cell. As the cell employs a common electrolyte, the need of employing a membrane is averted. It has been possible to achieve a capacity value of 114 mAh g^???1 at a load current-density of 20 mA cm^???2 with the cell at a faradaic efficiency of 95%. The cell is tested for 200 cycles with little loss in its capacity and efficiency.     

Non-aqueous rechargeable Al–O2 battery with a bifunctional catalyst of carbon microspheres

Non-aqueous secondary Al-O₂ batteries have recently received much attention due to their high theoretical capacity, element richness, safety and low cost, although there are still many problems to be overcome. In this paper, a type of Al-O₂ battery using AlCl₃/[EMIm]Cl ionic liquid as electrolyte and carbon microspheres (CMs) as air electrode was considered. The batteries with CMs deliver a high specific capacity of 820 mAh g^?1 in the first cycle at the current density of 25 mA g^?1 and a low charge voltage. In addition, CMs show better redox catalytic activity for O₂ compared with super-p (SP) and the Al-O₂ batteries have two obvious oxygen reduction processes corresponding to two reductive peaks.     

Studies on electrical conductivity and dielectric behaviour of PVdF–HFP–PMMA–NaI polymer blend electrolyte

Polymer blend electrolytes composed of poly(vinylidene fluoride-co-hexafluoro-propylene), poly(methyl methacrylate) and 1·0 M NaI as salt have been synthesized using solution caste technique by varying the PVdF(HFP)–PMMA blend concentration ratio systematically. A.c. impedance studies were performed to evaluate the ionic conductivity of the polymer electrolyte films. The highest ionic conductivity at room temperature for [PVdF(HFP)–PMMA(4:1)](20 wt%) – [NaI(1·0 M)](80 wt%) system is found to be 1·67 × 10^???2 S cm^???1. XRD studies reveal complete complexation of the salt in the polymeric blend systems. The temperature dependence conductivity has been performed in the range of 303–373 K and it is observed that it obeys the Arrhenius behaviour. It has been observed that the dielectric constant, ε _r and dielectric loss, ε _i, increases with temperature in the lower frequency region and is almost negligible in the higher frequency region. This behaviour can be explained on the basis of electrode polarization effects. Plot of real part, M _r and imaginary part, M _i vs frequency indicates that the systems are predominantly ionic conductors. The phenomenon suggests a plurality of relaxation mechanism.     

Lithium ion conducting solid polymer blend electrolyte based on bio-degradable polymers

Lithium ion conducting polymer blend electrolyte films based on poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) with different Mwt% of lithium nitrate (LiNO₃) salt, using a solution cast technique, have been prepared. The polymer blend electrolyte has been characterized by XRD, FTIR, DSC and impedance analyses. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR study confirms the complex formation between the polymer and salt. The shifts in T _g values of 70 PVA–30 PVP blend and 70 PVA–30 PVP with different Mwt% of LiNO₃ electrolytes shown by DSC thermograms indicate an interaction between the polymer and the salt. The dependence of T _g and conductivity upon salt concentration has been discussed. The ion conductivity of the prepared polymer electrolyte has been found by a.c. impedance spectroscopic analysis. The PVA–PVP blend system with a composition of 70 wt% PVA: 30 wt% PVP exhibits the highest conductivity of 1·58 × 10^???6 Scm^???1 at room temperature. Polymer samples of 70 wt% PVA–30 wt% PVP blend with different molecular weight percentage of lithium nitrate with DMSO as solvent have been prepared and studied. High conductivity of 6·828 × 10^???4 Scm^???1 has been observed for the composition of 70 PVA:30 PVP:25 Mwt% of LiNO₃ with low activation energy 0·2673 eV. The conductivity is found to increase with increase in temperature. The temperature dependent conductivity of the polymer electrolyte follows the Arrhenius relationship which shows hopping of ions in the polymer matrix. The relaxation parameters (ω) and (τ) of the complexes have been calculated by using loss tangent spectra. The mechanical properties of polymer blend electrolyte such as tensile strength, elongation and degree of swelling have been measured and the results are presented.     

Polypyrenes as High‐Performance Cathode Materials for Aluminum Batteries

The pressing need for low‐cost and large‐scale stationary storage of electricity has led to a new wave of research on novel batteries made entirely of components that have high natural abundances and are easy to manufacture. One example of such an anode–electrolyte–cathode architecture comprises metallic aluminum, AlCl₃:[EMIm]Cl (1‐ethyl‐3‐methylimidazolium chloride) ionic liquid and graphite. Various forms of synthetic and natural graphite cathodes have been tested in recent years in this context. Here, a new type of compelling cathode based on inexpensive pyrene polymers is demonstrated. During charging, the condensed aromatic rings of these polymers are oxidized, which is accompanied by the uptake of aluminum tetrachloride anions (AlCl₄^?) from the chloroaluminate ionic liquid. Discharge is the fast inverse process of reduction and the release of AlCl₄^?. The electrochemical properties of the polypyrenes can be fine‐tuned by the appropriate chemical derivatization. This process is showcased here by poly(nitropyrene‐co‐pyrene), which has a storage capacity of 100 mAh g^?1, higher than the neat polypyrene (70 mAh g^?1) or crystalline pyrene (20 mAh g^?1), at a high discharge voltage (≈1.7 V), energy efficiency (≈86%), and cyclic stability (at least 1000 cycles).     

Characterization of carboxy methylcellulose doped with DTAB as new types of biopolymer electrolytes

The investigation of new solid biopolymer electrolyte (BEs) system based on carboxy methylcellulose (CMC) is creating opportunity for new types of electrochemical devices, which may themselves, in turn, revolutionize many industrial areas. Biodegradable carboxy methylcellulose (CMC) doped with dodecyltrimethyl ammonium bromide (DTAB) as BEs were prepared via solution-casting method. Upon addition of 35 wt. % of DTAB, highest ionic conductivity of 7·72 × 10^???4 Scm^???1 was achieved due to its higher amorphous region compared to other samples prepared. This result had been further proven in FTIR study. Temperature dependence relationship obeys the Arrhenius rule from which the activation energy, E _a, for ionic conductivity and activation energy for relaxation process, E _τ , were evaluated. The divergent values between E _a for ionic conductivity and relaxation process E _τ shows that the ions hop by jumping over a potential barrier.     

Preparation and characterization of zirconia and mixed zirconia/titania in ionic liquids

Zirconia and mixed zirconia/titania were synthesized in two different ionic liquids, namely, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP]TFSA) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide ([EMIm]TFSA) using sol–gel methods. The synthesized oxides were characterized by means of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray (SEM-EDX)), thermogravimetric and differential thermal analyses (TGA–DTA). The results show that the as-synthesized ZrO₂ powders obtained either in [BMP]TFSA or in [EMIm]TFSA show amorphous behaviour, and calcination at 500 °C yields t-ZrO₂ which is subject to further phase transformation to m-ZrO₂ at 1000 °C. The type of the ionic liquid influences the morphology of the synthesized zirconia as the sample obtained from [BMP]TFSA showed a porous morphology with very fine particles in the nanometer regime, whereas micro-rods were obtained from [EMIm]TFSA. ZrO₂-TiO₂ nanorods with an average diameter of about 100 nm were synthesized in [EMIm]TFSA. The presence of zirconia in the mixed oxides stabilizes the anatase phase and elevates the temperature at which the phase transformation to rutile occurs.     

A Novel Graphite–Graphite Dual Ion Battery Using an AlCl3–[EMIm]Cl Liquid Electrolyte

Herein, a novel graphite–graphite dual ion battery (GGDIB) based on a AlCl₃/1‐ethyl‐3‐methylimidazole Cl ([EMIm]Cl) room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated, that is, metallic aluminum is deposited/dissolved on the surface of the anode, and chloroaluminate ions are intercalated/deintercalated in the cathode material. The self‐discharge phenomenon and pseudocapacitive behavior of the GGDIB are also analyzed. The GGDIB shows excellent rate performance and cycle performance due to the high ionic conductivity of ionic liquids. The initial discharge capacity is 76.5 mA h g⁻¹ at a current density of 200 mA g⁻¹ over a voltage window of 0.1–2.3 V, and the capacity remains at 62.3 mA h g⁻¹ after 1000 cycles with a corresponding capacity retention of 98.42% at a current density of 500 mA g⁻¹. With the merits of environmental friendliness and low cost, the GGDIB has a great advantage in the future of energy storage application.     

Large resonant third-order optical nonlinearity of thin film containing J-like aggregates of a bis[4-(N-dibutylamino)phenyl]squarylium dye

The third-order optical nonlinearity and response of thin film containing J-like aggregates of a bis[4-(N-dibutylamino)phenyl]squarylium dye were measured by degenerate four-wave mixing (DFWM) technique under resonant conditions. The temporal profile of DFWM signal was obtained with a time resolution of 0·3 ps (FWHM), and was found to consist of at least two components, i.e. the coherent instantaneous nonlinear response (electronic response) and the slow response due to the excited state population grating. The effective χ ⁽³⁾ value of thin squarylium dye film was evaluated to be as high as 1·1 × 10^???7 esu, and the figure of merit of third-order nonlinearity F (F =?χ ⁽³⁾/α), was calculated to be about 2·1 × 10^???13 esu cm.     

Evidence for high ionic conductivity in lithium–lanthanum titanate, Li0·29La0·57TiO3

Lithium–lanthanum titanate, Li_0·29La_0·57TiO₃, is prepared by solid-state reaction method and it is furnace-cooled to room temperature. X-ray diffraction results indicated that the compound has tetragonal perovskite-like structure and the lattice parameters are determined as a = 3· 8714 Å and c = 7· 7370 Å. The average grain size is found to be 5 μm from SEM micrograph. The analysis of FTIR and Raman spectra of the sample supported tetragonal structure inferred from XRD data. The impedance spectrum of the sample is separated into bulk and grain boundary parts by analysing the impedance data. The high bulk ionic conductivity is reported as 1· 12 × 10^???3 S cm^?1 at room temperature. D.C. conductivity measurements indicate that the compound is a good ionic conductor.     

Thermophysical Properties of Molten Yttrium Measured by Non-contact Techniques

Understanding the nature and behavior of liquid metals requires accurate values of their physical properties (e.g., density, surface tension, viscosity). However, maintaining samples of matter in their liquid phases, in particular under supercooled conditions, is a great challenge when dealing with refractory metals. This is due mainly to their high melting temperatures (e.g., 3,695 K for W), their high vapor pressure, and the risk of melt contamination with a support or crucibles. Electrostatic levitation, laser heating in vacuum, and non-contact characterization techniques circumvented these difficulties and allowed the determination of the properties of several metals in their liquid state, above their melting temperature as well as in their supercooled phase. In this work, several thermophysical properties were successfully measured with an electrostatic levitation furnace under vacuum conditions. For the first time, density and viscosity data of yttrium were reported over large temperature intervals in the liquid phase. Over the 1,560 to 2,100 K temperature span, the density can be expressed as $\rho (T)=4.15\times 10^3-0.21\, (T - T_{\rm m})$ (kg·m^???3) with T _m = 1,796 K, yielding a volume expansion coefficient of 5.1 × 10^???5 K^???1. In addition, the surface tension can be expressed as $\sigma \left( T \right)=8.04\times 10^2-0.05\,(T - T_{\rm m})$ (mN·m^???1) and the viscosity as $\eta \left( T \right)=0.00287\,\exp \left[ {{1.1\times 10^5} \mathord{\left/ {\vphantom {{1.1\times 10^5} {\left( {\mbox{RT}} \right)}}} \right. \kern-0em} {\left( {\mbox{RT}} \right)}} \right]$ mPa·s over the 1,830 to 2,070 K interval. The results, in particular those for viscosity, suggest that performing similar experiments in microgravity could improve the accuracy of the measurements.     

Influence of conductive electroactive polymer polyaniline on electrochemical performance of LiMn1·95Al0·05O4 cathode for lithium ion batteries

Conductive electroactive polymer polyaniline is utilized to substitute conductive additive acetylene black in the LiMn_1·95Al_0·05O₄ cathode for lithium ion batteries. Results show that LiMn_1·95Al_0·05O₄ possesses stable structure and good performance. Percolation theory is used to optimize the content of conductive additive in cathode. It shows that the conductivity of cathode reaches its maximum value when the content of conductive additives is 15 wt%. This is in agreement with the results of charge and discharge experiments. The application of polyaniline can evidently enhance the electrochemical performance of cathode. The discharge capacity of cathode using 15 wt% polyaniline is 95·9 mAh g^???1 at the current density of 170 mA g^???1. The charge transfer resistance under different depths of discharge of cathode is much lower compared with the use of acetylene black. It can be concluded that the application of polyaniline in cathode can greatly improve the electrochemical performances of LiMn_1·95Al_0·05O₄ cathode.     

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling

Layered LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNi_1/3Co_1/3Mn_1/3O₂ materials were investigated. XRD analysis indicated the as-synthesized LiNi_1/3Co_1/3Mn_1/3O₂ was with the layered α-NaFeO₂ structure. The discharge capacity was about 154 m·Ahg^???1 at 0·1 °C rate in the range of 2·0–4·5 V. The kinetics of the LiNi_1/3Co_1/3Mn_1/3O₂ materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNi_1/3Co_1/3Mn_1/3O₂ was determined in the range of 10^???8??? 10^???9 cm²· s^???1 as a function of voltage of 3·7?4·5 V.     

Structural properties of Cd–Co ferrites

Ferrite samples with composition, Cd $_{\emph{x}}$ Co $_{1-\emph{x}}$ Fe₂O₄ (x = 0·80, 0·85, 0·90, 0·95 and 1·0), were prepared by standard ceramic method and characterized by XRD, IR and SEM techniques. X-ray analysis confirms the formation of single phase cubic spinel structure. Lattice constant and grain size of the samples increase with increase in cadmium content. Bond length (A–O) and ionic radii ( ${\emph{r}}_{\rm {A}})$ on A-sites increase, whereas bond length (B–O) and ionic radii ( ${\emph{r}}_{\rm{B}})$ on B-site decrease. The crystallite sites of the samples lie in the range of 29·1–42·8 nm. IR study shows two absorption bands around 400 cm^???1 and 600 cm^???1 corresponding to tetrahedral and octahedral sites, respectively.     

Preparation and electrochemical properties of SrCe 0·4 Zr 0·4 Yb 0·2 O 2·9 electrolyte

The perovskite Yb-doped strontium cerate–zirconate material, SrCe_0·4Zr_0·4Yb_0·2O_2·9, was prepared by solid-state reaction and the structure was characterized by X-ray diffraction. The calcination process of the powder was investigated by thermogravimetric/differential thermal analysis (TG–DTA). The high temperature conductivities were measured by d.c. four-probe technique in the temperature range from 500 to 950°C in wet hydrogen and effect of temperature on conductivity was investigated. The conductivity increased with the elevation of temperature from 500 to 950°C. The highest conductivity of 4·4 × 10^???2 S· cm^???1 was observed for SrCe_0·4Zr_0·4Yb_0·2O_2·9 at 950°C. The current–voltage (I–V) and current–power (I–P) characteristics of the single cell (H₂, Pt/SrCe_0·4Zr_0·4Yb_0·2O_2·9/Pt, O₂) at temperature range from 600 to 850°C were tested. With the temperature increasing from 600 to 850°C, the open circuit voltage (OCV) decreased from 1·164 to 1·073 V and the ionic transfer number decreased from 0·996 to 0·946. At 850°C, the maximum power density of 25·2 mW· cm^???2 was observed.     

Preparation of High‐Performance Ionogels with Excellent Transparency,Good Mechanical Strength,and High Conductivity

Ionogels offer great potential for diverse electric applications. However, it remains challenging to fabricate high‐performance ionogels with both good mechanical strength and high conductivity. Here, a new kind of transparent ionogel with both good mechanical strength and high conductivity is designed via locking a kind of free ionic liquid (IL), i.e., 1‐ethyl‐3‐methylimidazolium dicyanamide ([EMIm][DCA]), into charged poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS)‐based double networks. On the one hand, the charged PAMPS double network provides good mechanical strength and excellent recovery property. On the other hand, the free [EMIm][DCA] locked in the charged double network through electrostatic interaction offers ionic conductivity as high as ≈1.7–2.4 S m^?1 at 25 °C. It is demonstrated that the designed ionogel can be successfully used for a flexible skin sensor even under harsh conditions. Considering the rationally designed chemical structures of ILs and the diversity of charged polymer networks, it is envisioned that this strategy can be extended to a broad range of polymer systems. Moreover, functional components such as conducting polymers, 0D nanoparticles, 1D nanowires, and 2D nanosheets can be introduced into the polymer systems to fabricate diverse novel ionogels with unique functions. It is believed that this design principle will provide a new opportunity to construct next‐generation multifunctional ionogels.     

Spin canting phenomenon in cadmium doped cobalt ferrites, CoCd x Fe2−x O 4 ( x = 0·0, 0·2, 0·4, 0·6, 0·8 and 1·0), synthesized using sol–gel auto combustion method

Synthesis of non-collinear (spin canted) ferrites having the formula, CoCd _x Fe_2???x O ₄ (x?= 0·0, 0·2, 0·4, 0·6, 0·8 and 1·0), has been carried out using the sol–gel auto combustion method. The ferrite samples show an interesting magnetic transition from Neel to Yafet–Kittel configuration, as the Cd^2?+? concentration is increased beyond x?= 0·4. The FT–IR spectra confirm the formation of the metal oxide bond as they exhibit two frequency bands in the range of ~595 cm^???1 and ~450 cm^???1, corresponding to the tetrahedral and the octahedral stretching vibrations of the metal oxide, respectively. The structural evolutions of the nanophase investigated using powder X-ray diffraction (XRD) technique show that the average crystallite size is ~ 35 nm. The magnetic studies reveal that the saturation magnetization, M _s , increases up to x?= 0·4 and decreases when the value of x is >0·4. It is proposed that the incorporation of Cd^2?+? ion takes place into the tetrahedral sites and up to x?= 0·4, Neel’s model is followed. But for x?> 0·4, canting of spins occurs, as explained by Yafet–Kittel (Y–K) model. The d.c. resistivity decreases as a function of temperature, indicating semiconducting nature of the ferrites and the positive value of Seebeck coefficient establishes p-type conduction behaviour for all the ferrite samples.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

Studies on ionic transport properties of a new Ag+ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO2

A new Ag⁺ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO₂ using a quenched/annealed [0·75 AgI: 0·25 AgCl] as host compound in place of conventional host AgI, has been investigated. The effects of various preparation methods and soaking time are reported. The composition 0·8[0·75 Agl: 0·25 AgCl]:0·2SnO₂ exhibited optimum conductivity (σ = 8·4 × 10⁻⁴S/cm) with conductivity enhancement of ∼ 10¹ from the annealed host at room temperature. Transport property studies such as electrical conductivity (σ) as a function of temperature using impedance spectroscopy technique, ionic transference number (t _ion) using Wagner’s d.c. polarization method and ionic mobility (μ) by transient ionic current technique were carried out on the optimum conducting composition. The mobile ion concentration (n) was calculated from ‘σ’ and ‘μ’ data.     

Electropolymerization in proton-functionalized anilinium salts/glycol deep eutectic solvents

Novel proton-functionalized solid anilinium salts (anilinium hydrochloride ([HANI]Cl) and anilinium nitrate ([HANI]NO₃)) are synthesized. Simply mixing proton-functionalized anilinium salt with glycol in appropriate ratios can get deep eutectic solvents (DESs) which are liquid at room temperature. DES system is a new type of ionic liquids (ILs) or IL analogs. Tests show that the resulting DES systems have higher conductivity and lower viscosity which are suitable for electropolymerization. The electropolymerization of aniline in novel liquid DES ([HANI]Cl/(CH₂OH)₂ and [HANI]NO₃/(CH₂OH)₂) without exogenous protons is first reported. The cyclic voltammograms (CVs) in neat DES show two pairs of redox peaks. Unlike in acidic aqueous solutions, the electropolymerization of aniline in the DES needs no exogenous protons. UV–Vis and FTIR analysis show that the conductive polyaniline (PANI) is obtained. Moreover, the specific capacitance of PANI from the [HANI]Cl/(CH₂OH)₂ system is ca. 341 F g^?1 and that from the [HANI]NO₃/(CH₂OH)₂ is ca. 492 F g^?1, which are superior to that of the PANI obtained in an acid medium. The SEM characterization indicates that the resulting PANI on ITO is cross-linked nanoporous polymer membrane, which is benefit for the capacitance performance of PANI.