LiNO3 Aqueous Solution Research Articles

Unveiling the Structural and Dynamic Characteristics of Concentrated LiNO3 Aqueous Solutions through Ultrafast Infrared Spectroscopy and Molecular Dynamics Simulations.

Highly concentrated aqueous electrolytes have attracted a significant amount of attention for their potential applications in lithium-ion batteries. Nevertheless, a comprehensive understanding of the Li+ solvation structure and its migration within electrolyte solutions remains elusive. This study employs linear vibrational spectroscopy, ultrafast infrared spectroscopy, and molecular dynamics (MD) simulations to elucidate the structural dynamics in LiNO3 solutions by using intrinsic and extrinsic vibrational probes. The N-O stretching vibrations of NO3- exhibit a distinct spectral splitting, attributed to its asymmetric interaction with the surrounding solvation structure. Analysis of the vibrational relaxation dynamics of intrinsic and extrinsic probes, in combination with MD simulations, reveals cage-like networks formed through electrostatic interactions between Li+ and NO3-. This microscopic heterogeneity is reflected in the intertwined arrangement of ions and water molecules. Furthermore, both vehicular transport and structural diffusion assisted by solvent rearrangement for Li+ were analyzed, which are closely linked with the bulk concentration.

Lithium trivanadate thin films by polymer-assisted spin coating method for supercapacitor applications

Lithium trivanadate (LiV3O8) thin films were prepared by polymer assisted spin coating method. Here, the effect on addition of the polymers PVA, PVP, PEG and their combination on the preparation step were explored. The structural and morphological changes were analyzed by varying the substrate temperature, and its effect on the electrical and electrochemical performances were also studied. The thin films exhibited mixed micro and nanorod morphology. The XPS spectrum shows the stable 5+ oxidation state for vanadium. The electrochemical performance of the LiV3O8 thin film made using PVA:PVP and PVA:PEG in the 1:1 ratio outperformed the material made using PVA alone. The aqueous LiNO3 solution served as the electrolyte in three-electrode system. A specific capacitance of 359 F g−1 for a current density of 0.5 A g−1 as well as an areal capacitance of 143.8 F cm−2 at 0.2 mA cm−2 current density was obtained for the material made with PVA:PVP (1:1).

Preparation and characterization of lithium trivanadate thin films by spray pyrolysis method for supercapacitor applications

The lithium trivanadate (LiV3O8) thin films were deposited over stainless steel (SS) substrates by spray pyrolysis method. The material deposited at an optimized substrate temperature of 350°C and at an annealing temperature of 500°C (LV350_500/SS) performed better in electrochemical properties. The structural and surface morphological characteristics of the as deposited materials were determined using the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. The stable V5+ state was observed for the as-prepared LiV3O8 thin film in the X-ray photoelectron (XPS) spectrum. The electrochemical performance of the thin films were characterized using a three-electrode configuration with Ag/AgCl as the reference electrode, thin film material as the working electrode, and the platinum wire as the counter electrode. The 1 M LiNO3 aqueous solution was taken to be the electrolyte. LV350_500/SS made using a Li/V molar concentration of 0.1: 0.3 displayed an initial specific discharge capacitance value of 695 Fg−1 at a current density of 0.25 Ag−1, in the voltage range of -0.4 V to 0.4 V. But, the LV350_500/SS prepared using Li/V molar concentration of (0.05: 0.15) showed a low specific capacitance value of 181 Fg−1. A symmetric supercapacitor device made with the LV350_500/SS thin film as the electrodes and poly(vinylidene fluoride-co-hexafluoropropylene)/2D Graphene Oxide (PVdF-HFP/GO) composite polymer membrane as the electrolyte showed an excellent specific discharge capacitance value of 31 Fg−1 for a current density of 0.25 Ag−1. The calculated specific energy density and specific power density values were found to be 69 Whkg−1 and 1002 Wkg−1 respectively, for the above symmetric device.

N,N-Dimethylacetamide-Diluted Nitrate Electrolyte for Aqueous Zn//LiMn2O4 Hybrid Ion Batteries.

N,N-Dimethylacetamide (DMA) cooperated with LiNO3 salt has previously shown to be a promising electrolyte for a Li//O2 battery, showing good stability against both the O2 electrode reaction and Li stripping/plating. In this work, DMA is hybridized with a concentrated nitrate electrolyte [2.5 m Zn(NO3)2 + 13 m LiNO3 aqueous solution] for better electrochemical stability while using less dissolved salts. The widest electrochemical stability window for this DMA-diluted electrolyte is determined as 3.1 V, the negative critical stability potential of which is -1.6 V versus Ag/AgCl, indicating desirable stability against hydrogen evolution and Zn deposition. The findings can be attributed to the weakened Li+/Zn2+ solvation sheath caused by low permittivity of DMA, as revealed through Raman spectra characterization and molecular dynamics simulation. A Zn//Zn symmetrical cell and Zn//LiMn2O4 hybrid ion batteries are assembled in air directly, attributed to the stability of DMA toward O2. Zn stripping/plating with a dendrite-free morphology is delivered for 110 h and 200 charge/discharge cycles under 1 C rate, achieving 99.0% Coulombic efficiency. The maximum capacity of the battery is 121.0 mA h·g-1 under 0.2 C rate (based on the mass of LiMn2O4), delivering an energy density of 165.8 W h·kg-1 together with 2.0 V working voltage. This work demonstrates the feasibility and validity of utilizing a relatively dilute electrolyte dissolved in oxygen for a highly stable aqueous rechargeable battery.

Coconut Shell-Derived Activated Carbon for High-Performance Solid-State Supercapacitors

Coconut shells, low-cost and renewable agro-wastes, were used as a starting material in the synthesis of hierarchical activated carbons via hydrothermal, KOH-activation, and carbonization techniques. The ratio of KOH to hydrochar was varied in a systemic manner to study how it influences the texture and electrochemical behavior of the capacitor. Coconut shell-based carbon coated on nickel foams presented a surface area of 1567 m2 g−1, with micropores as well as mesopores widely distributed. The sample showed superior electrochemical performance, attaining 449 F g−1 at 1 A g−1 in 6 M LiNO3 aqueous solution. The solid-state symmetric supercapacitor device delivered a specific capacitance of 88 F g−1 at 1 A g−1 and a high energy density of 48.9 Whkg−1 at a power density of 1 kW kg−1. At a wide voltage window of 2.0 V, the sample was highly stable during the cycle test, showing a 92% capacitance retention at 2 A g−1 after cycling for 5000 times. The superior performance is due to the sample possessing great BET surface area, a good distribution of pores, and the usage of a suitable electrolyte. This facilitates an electrical double layer that can be deployed for applications to store energy.

The Importance of Li-Ion Nature and Stacking in Layered Cathode Materials for Aqueous Ion Batteries: From Bulk to Surface Models

The performance of aqueous ion batteries has been demonstrated since the foundational work from Dahn et al. who combined an anode of VO2 and a cathode of LiMn2O4 in an aqueous electrolyte. The use of aqueous electrolytes opens the possibility of proton co-insertion, one of the common assumptions to explain performance issues in aqueous electrolytes. Experimental and computational works compared the feasibility of several cathode materials to be intercalated by H+ concluding likewise that non-layered cathode materials are less prone to proton intercalation than layered materials.Therefore, layered compounds should not be good candidates as cathodes of aqueous batteries, although Li+ insertion/extraction using high concentrated LiNO3 aqueous solution as electrolyte, show results consistent with the Li (de)intercalation in organic electrolytes between the ranges from x equals 0.5-1.0 in layered LixCoO2. Thus, could layered materials have a good performance in aqueous environment despite of their tendency to accommodate protons?In this work, we use ab-initio computations to investigate the behavior of LixCoO2 in aqueous electrolytes analyzing the proton insertion to determine which specific chemical and structural features lead to electrochemically stable materials for aqueous batteries by means of bulk and surface models. The investigations have concerned layered NaxCoO2 in order to investigate the role of stacking and ion material.Our simulations reveal the excellent performance of LixCoO2 in contrast to NaxCoO2. By means of DFT calculations, the H+/ion exchange have been studied and the grand potential phase diagram and voltage-composition curves have been built considering different phases of LixCoO2 and NaxCoO2. Our simulations predicts the CoO(OH) as the most stable insertion/extraction product at battery operation conditions, due to the formation of O-H-O bonds. However, LixCoO2 is not affected by the presence of protons since they co-existence is not stable in comparison to full lithiated and full protonated systems. Our computations reveal that H+ could have a secondary role as surface detrimental agent, without compromising the battery performance. Nevertheless, the nature of Na and the stacking of NaxCoO2 favors the accommodation of protons, showing different performance than LixCoO2, due to the different stacking and different behavior of Na.Our work suggests that to be layered is not enough justification to be discarded as cathode material for aqueous electrolytes. We suggest that the stacking, the alkali-proton repulsion, and specially the operation conditions (voltage window, pH...) are key factors to investigate the suitability or not of a layered material as positive electrode for ion aqueous batteries.

Thermodynamic Modeling of Aqueous LiCl, LiBr, LiI, and LiNO3 Solutions

Thermodynamic models are essential to facilitate the advancement of process design, optimization, and operation of electrolyte systems. In this work, a comprehensive thermodynamic framework based on the Electrolyte Nonrandom Two-Liquid model is developed to calculate phase equilibria behavior and salt solubility of aqueous LiCl, LiBr, LiI, and LiNO3 solutions. The model describes the non-ideality of the electrolyte solutions by using two binary interaction parameters for each molecule-electrolyte pair in the system. Each binary interaction parameter is further expressed with up to three temperature coefficients which are regressed from experimental data. To take into account the hydration of lithium ion, two separate chemistries for the dissociation of lithium salts are investigated. In the first case, the lithium ion is considered as a bare ion, Li+, while in the second case hydration of the lithium ion from Li+ to Li(H2O)+ is considered. The calculated thermodynamic properties compare adequately with the experimental data for both sets of chemistries for concentrations up to saturation and temperatures from 273.15 K up to 623.15 K. Moderate to significant improvements are observed with the incorporation of the hydration chemistry for aqueous LiCl, LiBr, and LiI solutions when compared to the non-hydrated lithium ion model results.

Effects of alkali additives in saturated LiNO3 aqueous electrolyte for improvement in cycling stability of polyimide anode

In this work, the alkali additive is introduced to improve the cycling stability of polyimide anode in saturated LiNO3 aqueous electrolyte. Optimal electrolyte consists of saturated LiNO3 aqueous solution with 0.001 mol L−1 KOH, which improves the capacity retention of polyimide in a three-electrode cell. When assembling with LiCoO2 cathode, the full cells exhibit good cycling stability with high capacity retention even after 1000 cycles. The remarkable improvement in cyclic performance is attributed to the efficient suppression of hydrogen ion accumulation in the electrolyte. Furthermore, theoretical calculation results indicate that the carbonyl interactions with hydrogen ions result in poor structural stability of the polymer. The formation of colloidal LiOH is realized/obtained by introducing an appropriate amount of KOH into the saturated LiNO3 electrolyte. The resulting colloidal LiOH not only reduces the concentration of free hydroxyl ions in the electrolyte, but also continuously releases the hydroxyl ions to react with hydrogen ions. These results suggest that the introduction of alkali in saturated LiNO3 aqueous electrolytes improves the electrochemical stability of polyimide anode, which will push the practical applications of polyimide materials in aqueous Li-ion cells.

Biomass-Derived Porous Carbons Derived from Soybean Residues for High Performance Solid State Supercapacitors.

A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m2 g−1 and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g−1 at 1 A g−1 in 6 M LiNO3 aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g−1 at 1 A g−1 and a high energy density of 68.2 Wh kg−1 at a power density of 1 kW kg−1 with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g−1 (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.

Superior cycling performance of a novel NKVO@polypyrrole composite anode for aqueous rechargeable lithium-ion batteries.

An aqueous rechargeable lithium-ion battery (ARLB) system has been assembled using as-prepared polypyrrole (PPy) to coat Na0.8K0.2K6O15 (NKVO) anode coupled with LiMn2O4 cathode, both immersed in an aqueous LiNO3 solution. The chemical polymerization techniques have been employed to uniformly coat the surface of NKVO with PPy. The phase of NKVO@PPy composite has been characterized by X-ray diffraction; for quantifying PPy content, the thermal gravimetric analysis was performed. Spectroscopy techniques have been used to visualize the microscale morphological changes on the particle surface of NKVO caused by PPy coating. The staircase cyclic voltammetry and galvanic charge-discharge tests have been conducted at various current rates in the voltage range of -1 to 1 V vs. saturated calomel electrode (SCE). The PPy coated NKVO material showed a similar intercalation/deintercalation mechanism to that of pristine NKVO. When subjected to cyclic performance evaluation at a higher rate of 4 A g-1, PPy-coated NKVO@PPy exhibited a preliminary discharge capacity of 115 mA h g-1 and 64.5 mA h g-1 following 400 cycles of charge-discharge with a retention rate of 55.6%, whereas the uncoated NKVO showed only 18.8% capacity retention rate. The significantly improved cyclic capacity retention has been attributed to the PPy coating, which acted as a protective layer preventing the unwanted side reactions, buffering the volume change and simultaneously increasing the electrical conductivity of pristine NKVO electrode during charge-discharge cycles. The decent performance demonstrated that NKVO@PPy is a promising electrode material for ARLB.

The influence of synthesis conditions on the redox behaviour of LiFePO4 in aqueous solution

To contribute to the knowledge on the influence of synthesis procedure on the intercalation kinetics of lithium ions into phospho-olivines, LiFePO4/C composite samples (LFPC) were synthesized in two ways, the first one in a sol-gel procedure (SG), and the other in a solid-state reaction (SS). The X-ray diffractograms (XRD) of both samples overlapped with that of pure LiFePO4, taken from the crystallographic database. Scanning electron microscopy pictures indicated the high degree of interparticle sintering, which caused a considerable agglomerate growth. The results of potentiodynamic measurements in aqueous LiNO3 solution revealed that for SS sample, three times higher initial capacity from that of SG one, (amounting to 74 mAh g−1 at 5 mV s−1). However, capacity fade on rising scan rate is much more expressed for SS sample than for SG one. We suggest that a different degree of material utilization due to the incomplete coverage of olivine particles by carbon explains this difference. The technique of separation of diffusion and capacitance currents was applied in a kinetic analysis, but it was shown to be inappropriate. We suggest the inapplicability of classic CV theory to the intercalation system accompanied by phase transition. Instead, a model of ohmic resistance determination of process kinetics was considered. LFPC-SS sample delivers three times larger capacity in LiNO3, amounting to 74 mAh g−1 at 1 mV s−1.

A systematically comparative study on LiNO3 and Li2SO4 aqueous electrolytes for electrochemical double-layer capacitors

In this work, highly soluble LiNO3 was adopted as the neutrally aqueous electrolyte for active carbon (AC)-based electrochemical double-layer capacitors (EDLCs), of which the electrochemical performances were evaluated. Simultaneously, the physicochemical properties such as the ionic conductivity and viscosity of the LiNO3 aqueous solution were investigated. As compared with the most studied Li2SO4 aqueous solution, the LiNO3 aqueous solution displays more favorable physicochemical properties and electrochemical performances as the neutral electrolytes for EDLCs. To be specific, the conductivity of the 5.0 M LiNO3 aqueous solution can reach up to 154.8 mS cm−1 at 25 °C, which is nearly two times of the maximum conductivity of 77.6 mS cm−1 for the 2.0 M Li2SO4 aqueous solution under the identical testing conditions. Even at a concentration as high as 9.0 M, the absolute viscosity of the LiNO3 aqueous solution is only 2.4, while that of the Li2SO4 aqueous solution achieves 3.0 at the maximum concentration of 2.5 M. Additionally, 5.0 M LiNO3 aqueous solution exhibits a wide electrochemical potential stability window from −0.9 to 0.9 V (vs. SCE) at the AC electrode, giving rise to an operating cell voltage of 1.8 V, which is comparable to that of 2.0 M Li2SO4 aqueous solution. Further, with the 5.0 M LiNO3 aqueous solution as the electrolyte, the as-fabricated EDLC delivers an energy density up to 21.16 Wh Kg−1 at a power density of 100.09 W kg−1, which is higher than 18.43 Wh Kg−1 for the EDLC with the 2.0 M Li2SO4 aqueous electrolyte at the identical power density. Even though the power density reaches as high as 5970 W kg−1, the energy density of the EDLC with the 5.0 M LiNO3 aqueous electrolyte can still remain at 13.1 Wh Kg−1, substantially higher than 8.71 Wh Kg−1 of the EDLC with the 2.0 M Li2SO4 aqueous electrolyte at the same power density. Moreover, the EDLC with the 5.0 M LiNO3 aqueous electrolyte also holds good cyclic stability. After 10000 charge–discharge cycles at a current density of 1 A g−1 and a cut-off voltage of 1.8 V, the capacity retention of this EDLC retains more than 90%. These results can render an insight to explore safe, eco-friendly, inexpensive and neutrally aqueous electrolytes for supercapacitors.

Effect of temperature on compressibility properties of 0.1, 0.5 and 1.0 molal solutions of alkali metal nitrates. Part 2. Aqueous solutions of lithium nitrate, sodium nitrate and potassium nitrate in the 278.15 K to 353.15 K temperature range

Sound velocities in aqueous solutions of LiNO3, NaNO3 and KNO3 were measured at 1K intervals from T=(278.15 to 353.15)K, in the 0.1mol·kg−1 0.5mol·kg−1 and 1.0mol·kg−1 solutions. Determined sound velocities and densities served to determine the isentropic and isothermal compressibilities, the apparent molar compressibilities, the apparent molar volumes, the isochoric thermal pressure coefficients, cubic expansion coefficients, changes of heat capacities with volume and with pressure, and the hydration numbers. In addition were evaluated the ultrasonic relaxation times and corresponding thermodynamic functions of the activation of the viscous process. Determined parameters are qualitatively correlated with changes in the structure of water when alkali metal nitrates are dissolved in it.

The synthesis of Li(Co Mn Ni)O2 cathode material from spent-Li ion batteries and the proof of its functionality in aqueous lithium and sodium electrolytic solutions

Abstract Several spent Li-ion batteries were manually dismantled and their components were uncurled and separated. The chemical composition of each battery's component was determined by atomic absorption spectroscopy. Among several ways to separate cathode material from the collector, the alkali dissolution treatment was selected as the most effective one. After both complete separation and acid leaching steps, the co-precipitation method, followed by a thermal treatment (700 °C or 850 °C), was used to resynthesize cathode material LiCo0.415Mn0.435Ni0.15O2. Its structure and morphology were characterized by XRD, Raman spectroscopy and SEM-EDS methods. The electrochemical behavior of recycled cathode materials was examined by cyclic voltammetry and chronopotentiometry in both LiNO3 and NaNO3 aqueous solutions. High sodium storage capacity, amounting to 93 mAh g−1, was measured galvanostatically at a relatively high current of ∼100 mA g−1. Initial lithium intercalation capacity of ∼64 mAh g−1, was determined potentiodynamically at very high scan rate of 20 mV s−1 (∼40 C). Somewhat lower initial capacity of ∼30 mAh g−1, but much lower capacity fade on cycling, was found for sodium intercalation at the same scan rate. The differences in the Li and Na charge storage capability were explained in terms of ion rearrangement during charging/discharging processes.

Superior lithium-ion insertion/extraction properties of a novel LiFePO4/C/graphene material used as a cathode in aqueous solution.

Herein, olivine LiFePO4 covered with graphene and carbon layers is prepared via a sol-gel method, followed by calcination, and the resultant composite is used as a cathode material in aqueous rechargeable lithium-ion batteries (ARLBs). The phase structure and morphology of the composite are characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and specific surface area analysis (BET). The ARLB system is fabricated using LiFePO4/C/graphene as the cathode and a zinc anode in 1 mol L-1 ZnSO4·7H2O and saturated LiNO3 aqueous solution without dissolved oxygen, which delivers a capacity of 153 mA h g-1 at 0.5C rate. Even at a 50C rate, it maintains a capacity of 95 mA h g-1 after 200 cycles. The excellent rate capabilities show that this cathode material exhibits good electrochemical performance and this novel ARLB has great potential in the fields of energy storage and high power sources.

The Effect on the Reaction Rate By the Binder Contact with the Cathode Active Material for 2V Class Water Based Lithium Ion Battery

Introduction Batteries with high electromotive force using aqueous electrolyte solution have been developed by the control of the Hydrogen and Oxygen overvoltage. Leclanche in 1866, manganese dioxide cathode active material, zinc anode active material, and ammonium chloride aqueous solution were applied as a Leclanche battery since zinc is well known as the suitable material of which having high hydrogen overvoltage to overcome the 1.23 V restriction of the water decomposition. Further break through on higher output voltage was achieved by applying PbO2 as the cathode material of lead-acid battery due to its high oxygen overvoltage. Similar point of view may be taken into account as a key point in the development on water-based lithium batteries. The binders commonly used in the conventional lithium ion batteries are polyvinylidene fluoride and polyacrylonitrile, they may work fine as the water based lithium batteries with similar functions. Thus we examined them from the view point of the overvoltage. Experimental The two electrode cells for testing cathode active material of 2V-class water based lithium-ion battery were prepared by the following procedure. Cathode active material of LiNi1/3Mn1/3Co1/3O2 (NMC), PVDF as the binder, and acetylene black conducting reagent were mixed to be as the cathode slurry. Aluminum or titanium were used as the current collector, and zinc was used as an anode. Charging/discharging performance in 6M LiNO3 aqueous electrolyte solution was evaluated by cyclic voltammetry at a sweep rate of 0.5 mV/s. To elucidate the effect of binder, the gold wire only and NMC implanted on gold wire were prepared by coated with and without PVDF, butyral resin, SBR binders, and used as the working electrode. The counter electrode of SUS and Ag/AgCl reference electrode were used for three-electrode cell with 6M LiNO3 aqueous electrolyte solution, and the electrochemical reaction was evaluated by cyclic voltammetry at a sweep rate of 5 mV/s. Results and Discussions For the case of Al current collector, the open circuit voltage of about 2.0 V was observed after charging. However, the gas evolution, probably oxygen evolution, from the electrode surface is observed, and the reaction current became unstable due to come unstuck of active material composites from Al current collector. The pH of electrolyte solution increased from 6 to 12 during the discharging, and this may be decreased the stability of Al. During the discharging, white precipitate was observed on zinc anode and this may be attributed to Zn(OH)2. To prevent these unstable situation, the current collector was changed from Al to Ti, and the results were fine as i) oxygen evolution was suppressed, ii) unstuck of active material composites was suppressed, iii) reaction current became stable. Clearly, it was concluded that the use of Ti was the promising current collector for the 2V class water based lithium-ion battery. According to the three-electrode cell measurement, only the case of PVDF binder showed clear charging/discharging current, whereas the other case did not show any charging/discharging current. As a conclusion, the choice of Ti as the current collector and the PVDF as the binder was suitable for 2V class water based lithium-ion battery.

Electrochemical Behavior of Li4Ti5O12 in Ionic Liquid/Water Bilayer Electrolyte

Introduction Lithium-ion batteries (LIBs) have been used in portable electronic devices, and recently expected to be used in large-scale energy facilities for electric vehicle or large energy storage systems. Flammable organic solvents were used in LIBs and it threaten the safety of LIBs. Therefore, nonflammable aqueous electrolytes have been investigated[1]. However, its narrow potential windows restrict the use of negative electrodes, which makes it difficult to obtain high voltage. In this study, we utilized stable liquid-liquid interface between water and hydrophobic ionic liquids in order to enhance the negative potential window. The electrochemical behavior of Li4Ti5O12(LTO) thin-film electrode, which cannot be used in aqueous solution, was investigated. Experimental LTO thin-film electrodes were prepared on a Pt substrate by a sol-gel method. LTO thin-film electrode was used as a working electrode. The bilayer electrolyte was formed on the working electrode: the upper layer was 1.0 mol dm −3 LiNO3 aqueous solution, and the lower layer was butyltrimethylammonium bis(trifluoromethylsulfonyl)amide (BTMATFSA) containing 1.0 mol kg −1 of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA). The counter electrode was platinum wire and the reference electrode was Ag/AgCl electrode (sat. KCl), and these electrodes were placed in the aqueous solution layer. Cyclic voltammetry was performed. Hereafter, all potentials are referred to as Ag/AgCl. Results Figure 1(a) shows the cyclic voltammograms of LTO thin-film electrode in bilayer electrolyte. At volume ratio of ionic liquid:aqueous solution = 3:4, clear redox peaks around ca. −1.33 V were observed. This reaction can be assigned to lithium-ion insertion/extraction into/from LTO. In contrast, Figure 1(b) shows that only large reduction current was observed and the redox peaks of LTO were not detected at volume ratio = 1:29. At this ratio, ionic liquid was miscible with aqueous solution. Thus, the reduction current below 0.9 V can be assigned to the hydrogen evolution reaction from water. These results reveal that bilayer electrolyte with clear interface prevent the hydrogen evolution reaction and enable lithium-ion to insert/extract into/from LTO. Reference [1] W. Li, J. R. Dahn, and D. S. Wainwright, Science, 264, 1115 (1994). Acknowledgment This work was partially supported by CREST, JST. Figure 1

Degradation of LiCoO2in aqueous lithium-air batteries

The degradation behaviour of aqueous rechargeable lithium cobalt oxide–air batteries in 5 M LiNO3 aqueous solution is observed by electrochemical characterizations. At lower scan rates of cyclic voltammetry, the three pairs of redox peaks at ESCE = 0.79/0.67, 0.89/0.85 and 1.15/0.97 V are proven to produce good reversibility. The small separation of the peaks is proportionally consistent with the Li+ diffusion coefficients of 2.82 × 10−7 cm2 s−1 (anodic) and 1.76 × 10−7 cm2 s−1 (cathodic). The lithium cobalt oxide–air batteries have a higher initial specific discharge capacity of 114.35 mA h g−1, which fades to 83% (after the first 10 cycles) and 52% (after 50 cycles). As the specific discharge capacity decreases, the resistance increases. The dissolution of Li+ is mainly attributed to these degradations. Further analyses of the batteries' degradation are performed by morphological and structural characterizations of the cathode material. Copyright © 2016 John Wiley & Sons, Ltd.

Transfer Properties of Diglycine from Water to Aqueous Alkali Metal Nitrate Solutions

Enthalpies of solution and densities of diglycine in aqueous solutions of LiNO3, NaNO3 and KNO3 were measured at 298.15 K. Transfer enthalpies ( $$ \Delta_{\text{tr}} H $$ ) and transfer partial molar volumes ( $$ \Delta_{\text{tr}} V_{\phi }^{0} $$ ) were derived for diglycine. The transfer enthalpies of diglycine from water to the three alkali metal nitrates solutions are negative while the transfer partial molar volume values are positive. The absolute values of $$ \Delta_{\text{tr}} H $$ and $$ \Delta_{\text{tr}} V_{\phi }^{0} $$ from water to the same concentration in salt solutions in both cases vary in the relative order LiNO3 < KNO3 < NaNO3. The results are discussed in terms of electrostatic interaction and structural interactions. Electrostatic interaction between the diglycine zwitterion and salts gives large contributions to Δtr H and $$ \Delta_{\text{tr}} V_{\phi }^{0} $$ . But, structursal interaction is responsible for the abnormal behavior of diglycine in aqueous LiNO3 solutions.

Study of Apparent Molar Volumes for Ionic Liquid, 1-Ethyl-3-methyl Imidazolium Chloride in Aqueous Lithium Nitrate, Lithium Bromide, and Lithium Chloride Solutions at Temperatures (298.15 to 318.15) K

The densities of ternary systems ([Emim][Cl]+ LiCl + H2O), ([Emim][Cl] + LiBr + H2O), and ([Emim][Cl]+ LiNO3 + H2O) and also binary system ([Emim][Cl] + H2O) were measured at T = (298.15 to 318.15) K using a vibrating U-tube densimeter. On the basis of experimental density data, the apparent molar volumes, Vφ, were computed. The values of apparent molar volumes for binary system were correlated to Redlich–Meyer and Pitzer equations and for ternary systems were correlated to Redlich–Meyer equation and apparent molar volumes at infinite dilution, Vφ0, are also calculated. Our results showed a negative transfer volume of [EmimCl] from water to the aqueous LiCl, LiBr, and LiNO3 solutions, which decrease by enhancing the salt mass fraction. The solute–solvent interactions and structure making or breaking ability of [Emim][Cl] have been discussed in details. The results of second derivative of limiting apparent molar volumes showed that the studied ionic liquid in this work acts as a structure maker.