LiOH Electrolyte Research Articles

The influence of bismuth oxide doping on the rechargeability of aqueous cells using MnO2 cathode and LiOH electrolyte

Bi-doped manganese dioxide (MnO2) has been prepared from γ-MnO2 by physical admixture of bismuthoxide (Bi2O3). The doping improved the cycling ability of the aqueous cell. These results are discussed and compared with the electrochemical behavior of bismuth-free MnO2. Batteries using the traditional potassium hydroxide (KOH) electrolyte are non-rechargeable. However, with lithium hydroxide (LiOH) as an electrolyte, the cell becomes rechargeable. Furthermore, the incorporation of bismuth into MnO2 in the LiOHcell was found to result in significantly longer cycle life, compared with cells using undoped MnO2. The Bi-doped cell exhibited a greater capacity after 100 discharge cycles, than the undoped cell after just 40 cycles. X-ray diffraction and the microscopic analysis suggest that the presence of Bi3+ ions reduces the magnitude of structural changes occurring in MnO2 during cycling. Comparison with additives assessed in our previous studies (titanium disulfide (TiS2); titanium boride (TiB2)) shows that the best rechargeability behavior is obtained for the current Bi-doped MnO2. As the size of Bi3+ ions (0.96 A) is much larger than Mn3+ (0.73 A) or Mn2+ (0.67 A) they have effectively prevented the formation of non-rechargeable products.

Synthesis and Characterization of Nanostructured Manganese Dioxide Used as Positive Electrode Material for Electrochemical Capacitor with Lithium Hydroxide Electrolyte

AbstractA nanostructured manganese dioxide electrode material was prepared using a solid‐reaction route starting with MnCl2·4H2O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with 1 mol·L−1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured γ‐MnO2 and α‐MnO2 containing some bound water in the structure, which was characterized by X‐ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO2 electrode and the MnO2/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO2 electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in 1 mol·L−1 LiOH electrolyte. The MnO2/AC hybrid capacitor with 1 mol·L−1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability.

The Zn–MnO[sub 2] Battery: The Influence of Aqueous LiOH and KOH Electrolytes on the Intercalation Mechanism

Intercalation chemistry of the zinc–manganese dioxide (Zn–MnO2) electrochemical cell aiming at the development of aqueous rechargeable batteries is presented. This study includes electrochemical characterization of MnO2 in saturated aqueous lithium hydroxide (LiOH) and potassium hydroxide (KOH) electrolytes. The lithium insertion into MnO2 results in the formation of LixMnO2. The reversible deintercalation process prevails in the presence of LiOH electrolyte. Rather than the usual protonation (H+) which is apparent in the literature while using KOH electrolyte, in this work, K+ ion insertion into MnO2 is observed. However, the K+ ion insertion is found to be irreversible. The intercalation mechanism is confirmed using various techniques to characterize the discharged MnO2 cathode in LiOH and KOH electrolytes. The influence of small amounts of Bi2O3 (bismuth oxide) additive on the discharge behavior of MnO2 is also discussed.

Supercapacitive behaviors and their temperature dependence of sol–gel synthesized nanostructured manganese dioxide in lithium hydroxide electrolyte

In the present work, a nanostructured manganese dioxide material was synthesized by a sol–gel method starting with manganese acetate (MnAc 2·4H 2O) and citric acid (C 6H 8O 7·H 2O) raw materials, and characterized by X-ray diffraction, infrared spectroscopic and transmission electron microscope techniques. The electrochemical properties and the influence of temperature on supercapacitive behaviors of the nano-MnO 2 electrode in 1 M LiOH electrolyte were investigated using electrochemical methods. Experimental results show that the MnO 2 electrode can exhibit an excellent pseudocapacitive behavior in 1 M LiOH electrolyte, and a high specific capacitance of 317 F g −1 can be obtained at a charge/discharge current rate of 100 mA g −1 and at the temperature of 25 °C. We found that temperature has a crucial influence on the discharge specific capacitance of the electrode. The specific capacitance at 25 °C is higher than that at 15 or 35 °C.

A novel hybrid manganese dioxide/activated carbon supercapacitor using lithium hydroxide electrolyte

We present here a novel hybrid nano-structured manganese dioxide/activated carbon supercapacitor with lithium hydroxide electrolyte, in which the MnO 2 positive material was prepared using a solid-state reaction route. The electrochemical behaviors of MnO 2 electrodes in 1 M LiOH and 1 M KOH electrolytes, respectively, were characterized by cyclic voltammetry and electrochemical impedance spectroscopy methods. The results indicated that the reaction mechanism of MnO 2 electrode in LiOH electrolyte appears to be Li + ion insertion/extraction in MnO 2 solid, which is different with that electrode in KOH electrolyte. Charge/discharge experiments showed that the rate dischargeability of the MnO 2/AC capacitor with 1 M LiOH electrolyte is excellent, and the cyclic stability of the MnO 2/AC capacitor with 1 M LiOH electrolyte is much better than that with 1 M KOH electrolyte.

Effect of Li ions on reduction of Fe oxides in aqueous alkaline medium

It has long been known that the performance of the Fe negative electrode in Fe/Ni or Fe/air batteries is improved by the presence of lithium ions in the electrolyte. This work therefore investigated quantitatively the effect of Li + on the reduction of some Fe II and Fe III oxides, as possible intermediates of Fe reduction/oxidation cycles, by comparing the extent of the reduction in pure 6.0 M KOH with that in lithiated alkaline media. Fe oxides were studied as pressed powder samples embedded in Ni foam. It was found that, in 6.0 M KOH, only FeO is electrolytically reduced at room temperature, whereas Fe 2O 3 and, to an even greater extent Fe 3O 4, are very recalcitrant to the reduction process. The situation dramatically changes in, for instance, 4.0 M KOH + 2.0 LiOH electrolyte, in which the extent of the reduction, even at room temperature, becomes significant for all compounds. This behaviour is very probably due to the reduction of Li + within the oxide lattice to produce Li x Fe y O z intercalation-compound intermediates, which are then reduced to metallic Fe and Li hydroxide.

Structural and spectroelectrochemical (UV–vis and IR) studies of nanocrystalline sol–gel derived TiO2 films

Abstract Nanocrystalline TiO 2 films with a high surface roughness were prepared by the sol–gel route from titanium (IV) iso-propoxide and brij 56 surfactant. XRD and TEM showed that the films consisted predominantly of anatase nanoparticles embedded in an amorphous phase. Addition of the surfactant significantly increased the intensity of the surface hydroxyl modes between 3600 and 3750 cm −1 in IR spectra. Spectroelectrochemical measurements of the films in 0.1 M LiOH electrolyte revealed optical modulation beyond 70%T. Slow-scan cyclovoltammetry showed that bleaching occurred in two steps, suggested to correspond to anatase and amorphous phase. The changes that occur during intercalation and deintercalation were followed by ex-situ IR transmission measurements in the regions of Ti–O, carbonate and surface hydroxyl bands.

Lithium insertion into manganese dioxide electrode in MnO 2/Zn aqueous battery : Part II. Comparison of the behavior of EMD and battery grade MnO 2 in Zn|MnO 2|aqueous LiOH electrolyte

A comparative study of the cathodic behavior of electrolytic manganese dioxide (EMD) and chemically prepared battery grade manganese dioxide (BGM) in Zn|MnO 2|aqueous lithium hydroxide (LiOH) cells has been carried out. The X-ray diffraction (XRD), infrared spectra (IR), thermo gravimetric analysis (TGA) and scanning electron microscope (SEM) investigations showed that the two materials had different phase compositions, water content and particle sizes. The cells with BGM had a higher open circuit voltage (OCV) and discharged at higher voltages as compared to those with EMD. The discharge capacity of BGM was lower compared to that of EMD. On discharge both the materials produced same phase i.e. lithium intercalated manganese dioxide (Li x MnO 2). This was also confirmed through X-ray photoelectron spectroscopy (XPS) investigation of the discharged products.

Lithium insertion into manganese dioxide electrode in MnO2/Zn aqueous battery

The discharge characteristics of manganese dioxide (γ-MnO2 of electrolytic manganese dioxide (EMD) type) as a cathode material in a Zn-MnO2 battery containing saturated aqueous LiOH electrolyte have been investigated. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data on the discharged material indicate that lithium is intercalated into the host structure of EMD without the destruction of its core structure. The XPS data show that a layer of insoluble material, possibly Li2CO3, is deposited on the cathode, creating a barrier to H2O, thus preventing the formation of Mn hydroxides, but allowing the migration of Li ions into the MnO2 structure. The cell could be reversibly charged with 83% of voltaic efficiency at 0.5 mA/cm2 current density to a 1.9 V cutoff voltage. The percentage utilization of the cathode material during discharge was 56%.

The Langmuir adsorption isotherms of electroadsorbed hydrogens for the cathodic hydrogen evolution reactions at the Pt(100)/H 2SO 4 and LiOH aqueous electrolyte interfaces

The Langmuir adsorption isotherms of the under-potentially deposited hydrogen (UPD H) and the over-potentially deposited hydrogen (OPD H) at the Pt(100)/0.5 M H 2 SO 4 and 0.5 M LiOH aqueous electrolyte interfaces have been studied using cyclic voltammetric and ac impedance techniques. The phase-shift profile (− φ vs. E) for the optimum intermediate frequency can be used as an experimental method to estimate the Langmuir adsorption isotherm ( θ vs. E) at the interfaces. At the Pt(100)/0.5 M H 2 SO 4 electrolyte interface, the equilibrium constant ( K) and the standard free energy (Δ G ads) of the OPD H are 1.5×10 −4 and 21.8 kJ/ mol , respectively. At the Pt(100)/0.5 M LiOH electrolyte interface, K transits from 1.9 (UPD H) to 6.1×10 −6 (OPD H) depending on the cathode potential ( E) and vice versa. Similarly, Δ G ads transits from −1.6 kJ/ mol (UPD H) to 29.7 kJ/ mol (OPD H) depending on E and vice versa. The transition of K and Δ G ads is attributed to the two distinct adsorption sites of the UPD H and the OPD H on the Pt(100) surface. The UPD H and the OPD H on the Pt(100) surface act as two distinguishable electroadsorbed H species. The UPD H and the OPD H at the Pt(100) interfaces are the independent processes depending on the H adsorption sites rather than the sequential processes for the cathodic H 2 evolution reactions. The criterion of the UPD H and the OPD H is the H adsorption sites and processes rather than the H 2 evolution reactions and potentials.

Fundamental baseline variations in aqueous near-infrared analysis

Distinctive, relatively small, analyte extinction coefficients in the near-infrared (NIR) spectral region, have led to NIR methodologies to probe the composition of concentrated solutions. However, as exemplified with alkaline hydroxide solutions, it is shown that the analyte strongly affects the conventional aqueous baseline of these measurements, and this baseline behavior must be addressed for effective NIR analysis. In the domain of molal and higher analyte concentration, the water baseline changes drastically as solute interacts and confines bulk solvent. At 967 nm an (hydroxide) absorption peak increases smoothly with increasing hydroxide activity in LiOH and NaOH electrolytes. Yet at this same wavelength, there is an unexpected absorption decrease in concentrated cesium (>5 m CsOH) and potassium (>13 m KOH) electrolytes, evidently due to solvent bridged anion–cation association. A peak for bulk water occurs nearby at 976 nm, with a unit pathlength absorbance of 0.24. This absorbance diminishes by an order of magnitude at high analyte concentration, as water activity decreases. A broad strong (0.53 cm −1) series of absorbances centered near 1200 nm diminish smoothly with decreasing bulk water activity. However, a broad strong absorption (14 cm −1) centered near 1450 nm, is resolved into two peaks, one disappearing, the other increasing at high hydroxide concentrations. Recognition of these variations permits effective NIR determination of analyte (in this case hydroxide). Second-order differentiation, ∂ 2 A/ ∂λ 2, at either 967 or 1421 nm, minimizes the effects of the near-lying bulk water absorption, and of baseline shift, and provides a linear variation with hydroxide concentration.

Characterisation of redox states of Ni(La)-hydroxide films prepared via the sol-gel route by ex situ IR spectroscopy

Ni(La)-hydroxide films were prepared from aqueous colloidal solutions containing nickel sulfate and lanthanum acetate in the molar ratio 10:1. Two types of film were made by heating for 15 and 60 min at 300 °C. Thermogravimetry (TG) and X-ray diffraction (XRD) reveal that both films consist of NiO (bunsenite 40%) nanoparticles (particle size ∼30 A), the remainder being amorphous. IR spectroscopy showed that the amorphous phase comprised the α(II)-Ni(OH)2 phase incorporating SO42−, carboxylate and water species. Cyclic voltammetry (CV) in a 0.1 M LiOH electrolyte combined with in situ UV-VIS spectroscopy revealed that the colouring/bleaching changes, as a function of applied potential, differed considerably for the two types of film. Ex situ IR spectroelectrochemical measurements at near-grazing incidence angle conditions using P-polarised light (NGIA IR) were performed for films heated for 60 min in 0.1 M LiOH and 0.1 M tetramethylammonium hydroxide (TMAH) electrolytes and cycled 1402 and 1802 times. During the oxidation/reduction cycles the α(II)-Ni(OH)2 phase transforms to the γ(III)-NiOOH phase, while the β(II)-Ni(OH)2 did not develop. This explains the high cycling stability of Ni(La)-hydroxide films. The incorporation of TMA+ ions was observed from the ν(CH3) stretching band intensities in the IR spectra of cycled films.

Sol-gel derived hydrated nickel oxide electrochromic films: Optical, spectroelectrochemical and structural properties

Electrochromic hydrated Ni-oxide films were prepared using a dip-coating technique from a nickel sulphate heptahydrate precursor in combination with glycerol, formamide and polyvinyalcohol. In-situ monochromatic (λ=400 nm) spectroelectrochemical measurements using a potential of −0.4 V to 0.8 V in 0.1M LiOH electrolyte revealed that the electrochromic efficiency was 23.5 cm2/C. The observed colouring/bleaching transmittance of a 100 nm thick film changed during potential cycling (20 cycles) by 45%. Ex-situ FT-IR absorption/reflection measurements performed at near-grazing incidence angle conditions (80°) confirmed transformation of as-deposited α-Ni(OH)2 phase to β-Ni(OH)2 at cathodic (bleached state) and β-NiOOH at anodic (coloured state) potentials during extended cycling (200 cycles). Clear evidence of the OH− ions insertion and release of SO 4 2− ions from the as-deposited films when soaked (0.5 hour) in 0.1M LiOH are given. These processes are accompanied by the transformation of the residual COO− groups originating from the peptisation with glacial acetic acid into CO 3 2− species residing in the films during extensive potential cycling.

Research of ZnMn spinel electrode material for aqueous secondary batteries

ZnMn complex oxides have been prepared by the organic acid complex method. X-ray diffraction (XRD) analyses show that the major product is a ZnMn spinel phase. The capacity of the sample is above 200 mAh g −1 on cycling in aqueous LiOH electrolyte, but deep-discharge has great influence on the cycling property of the sample. XRD analysis shows that Li + ions are intercalated into and extracted from the ZnMn spinel lattice during the discharge and charge process.

Optical, spectroelectrochemical and structural properties of sol-gel derived Ni-oxide electrochromic film

Ni-oxide films prepared using the sol-gel route and dip-coating method have been investigated by X-ray diffraction, scanning electron microscopy, FT-IR spectroscopy, cyclic voltammetry and in situ UVVIS spectroelectrochemical methods. The sols were prepared from a nickel sulphate hexahydrate precursor with formamide and polyvinylalcohol added to improve the abrasive resistance of films and to increase the yield from dip-coating deposition method (100–120 μm per dipping cycle). The films consisted of 40% NiO crystalline phase with an average grain size of 10 to 30 Å. The crystallites were incorporated into the amorphous phase which was found to resemble the α(II)-Ni(OH) 2 phase. A pronounced electrochromic effect ( ΔT ≈ 60%) was found by cycling the films in a 0.1 M LiOH electrolyte. This produced a maximum colouration efficiency ( λ = 450 nm) of 35–40 cm 2 C −1. Longitudinal optical (LO) mode of films potentially cycled up to 200 times have been detected by near-grazing incidence angle (NGIA) FT-IR reflection-absorption spectroscopy. The results revealed that the as-deposited films are progressively transformed to the β(II)-Ni(OH) 2 phase which is then converted to the β(III)-NiOOH phase during further potential cycling. The influence of foreign ions (SO 2− 4, CO 2− 3, OH −) on the development of persistent electrochromism and stability of films was established and discussed in detail.

Electrochromism of iron oxide films prepared via the sol-gel route by the dip-coating technique

Thin iron oxide films (69–500 nm) were deposited by the dip-coating method from iron-ion-containing sols which had been made from an FeCl 3·6H 2O precursor precipitated with ammonium hydroxide. Homogeneous sols were obtained after peptization of precipitates with the addition of acetic acid (∼ 60 mol.%) and no organics were added in order to adjust the sol viscosity for depositing the xerogel film. In situ UV—visible spectroelectrochemical measurements revealed that films heat treated in the temperature range 200–350°C exhibited intensive bleaching in 10 −3 M LiOH, KOH and NaOH electrolytes at cathodic potentials (−1.45 V) and became coloured again at anodic potentials (+0.6 V). The ability of films to take up Li + is 0.9−1.1 Li + per Fe 2O 3 giving rise to an intercalated charge of about 0.2 mC cm −2 per nanometre of the film thickness. This indicates that the film consists of particles of small grain size (γ-Fe 2O 3 (maghemite)) with dimensions < 100 Å and well-developed grain boundaries which contain OH − and other defect bonds originating from residual acetate groups. Consequently, only minor “activation” of films in base electrolytes is needed to attain reversible and steady electrochromism. Electrochromism was not observed for films heat treated at 500°C when α-Fe 2O 3 (haematite) with a larger grain size (∼ 270Å) is formed. The textural and structural properties of films were investigated with scanning electron microscopy, X-ray diffraction and UV—visible spectroscopic methods. The detected transverse optical and longitudinal optical modes determined with the help of Fourier transform IR reflectance measurements confirmed the homogeneous structure of films prepared at different temperatures. It was also found that the sols consist of iron oxohydroxo ions with chelated acetate units in addition to medium strong OH-O bonds, thus contributing to cross-linking of the gel and xerogel structure.

Lithium Intercalation from Aqueous Solutions

AbstractLithium can be intercalated into a variety of materials using aqueous electrochemical methods, provided that certain criteria are met. The materials must be stable in concentrated Li+ aqueous solution and Li intercalation must take priority over hydrogen intercalation. We use X-ray and neutron diffraction, as well as electrochemical methods to investigate if lithium or hydrogen is intercalated into certain hosts. For example, spinel Li2Mn2O4 can be made from spinel LiMn204 by intercalating one Li per mole in an electrochemical cell with 1 M LiOH electrolyte. If the electrochemical reduction is carried out further, beyond one electron per mole, Mn(OH)2 is then formed, as we prove using neutron diffraction. By carefully selecting electrode materials and electrolyte composition it is possible to make rechargeable lithium-ion cells with aqueous electrolytes. For example, LiMn204/γ-Li0.36MnO2 can be selected as an electrode couple, and5 M LiNO3 in water as an electrolyte to make lithium-ion cells with aqueous electrolytes.

Electrocatalytic activity of Li xNi 1− xO (0 ≤ x < 0.5) solid solutions in the oxygen evolution reaction

Cyclic voltammetry and steady state current-potential measurements, as well as physicochemical methods, have been used to elucidate the electrocatalytic properties of Li x Ni 1− x O electrodes in the oxygen evolution reaction in KOH and LiOH electrolytes. By varying the lithium content in Li x Ni 1− x O ( x = 0 to x = 0.42) and correspondingly the mean oxidation state of nickel (2 to 3) and the crystal structure type (from disordered to ordered rock salt type), it has been shown that nickel hydroxide thin films are formed electrochemically on the oxide surface. The structures of these nickel hydroxide films are determined not only by the chemical composition and crystal structure of Li x Ni 1− x O substrates but also determined by the anodic polarization conditions and the electrolyte type. α-Type Ni · OH · H 2O is deposited on NiO, and during anodic polarization it is partially transformed to β-type Ni · OH, resulting in an enhanced electrocatalytic activity. On ordered Li x Ni 1− x O (0.3 ≤ x < 0.5), oxyhydroxide films of Ni · O · OH are formed by ion exchange of Li + with electrolyte protons. During anodic polarization of these samples, Ni 4+ ions are stabilized, with a consequent significant decrease in their electrocatalytic activity. The highest activity towards O 2 evolution is displayed by Li x Ni 1− x O (0.05 ≤ x≤0.2) with a disordered rock salt structure, on which β-type Ni · OH films, which are stable during anodic polarization, are formed. The possible insertion of electrolyte ions into the nickel hydroxide films is discussed on the basis of comparative measurements performed in KOH and LiOH electrolytes.

Acoustic emission from a palladium electrode during hydrogen charging and its release in a LiOH electrolyte

Acoustic emission (EA) from a palladium electrode dipped in a 0.1 M LiOH electrolyte was measured during electrochemical hydrogen charging and its release. Large AE signals were observed for a few minutes in the first stage of the hydrogen charging in contrast with the small random AE signals caused by the evolution of hydrogen and oxygen gas. These signals appear to reflect the deformation of the Pd lattice by hydrogen charging. Various types of periodic AE signals were also observed during hydrogen charging and hydrogen release after charging for long periods. It is believed that these phenomena are associated with the hydrogen-transfer mechanism through defects existing in the palladium.

A Search for Tritium Production in Electrolytically Deuterided Palladium

This paper reports on a search for anomalous heat generation and tritium production associated with cold fusion in electrolytically deuterided palladium which was carried out for {gt} 180 days. Ten cathodes were mounted in electrolytic cells with LiOD and LiOH electrolytes and galvanostatically charged at current densities between 15 and 348 mA/cm{sup 2}. Most of the electrolytic cells were closed to the external environment; in all cells, the gases evolved during electrolysis were internally recombined using platinum recombination catalysts mounted in the cells. Tritium concentration assays using a liquid scintillation analyzer were performed on aliquots of electrolyte taken from some cells. No increase in tritium concentration was observed in the closed cells; in the partially open cells, small fluctuations in tritium concentration were observed, but these can be attributed to systematic errors.