AgI Ag Research Articles

AgI Electrolytes for Printable Solid-State Thermal Batteries

Thermal batteries are used as power sources in safety-critical electrical systems that require stability during long-term storage and reliability during high current operation when activated. AgI is an attractive material for a solid-state electrolyte for thermal batteries because of its low ionic conductivity near room temperature. It then undergoes a phase transition to a high conductivity phase above 150C. [1, 2] We have investigated the development of AgI batteries using I2 loaded carbon or PVP as a cathode material and Ag as an anode material. The electrochemical reactions for solid-state batteries in this configuration are as follows: Ag+ + e- + ½ I2 => AgI (Cathode)Ag => Ag+ + e- (Anode)Overall: 2Ag + ½ I2 => AgI (DE = 0.95 V) The batteries were first investigated as pressed pellets of Ag powder prepared by electrolysis, AgI powder, and Cabot Norit SX-Ultra activated carbon soaked in an ethanol I2 solution. Pressed pellets yielded an maximum power of 4.9 μW at room temperature and 0.6 mW above 150C, confirming the ability to extract higher power out of the cell when heated. Additive manufacturing of this electrolyte would enable the printing of thermal batteries in custom geometries for integration into small electronics devices. Pastes and processing conditions were developed for the printing of Ag, PVP loaded I2, and AgI. Additive manufacturing would also enable the printing of the higher conductivity AgI/Al2O3 composites which are difficult to fabricate by traditional clean room deposition technologies. This project was supported by Sandia Laboratory Directed Research and Development Grant 209285. SAND2020-4499 A.References.[1] K. Lehovec, J. Broder, Journal of The Electrochemical Society, 101, 208 (1954).[2] J. S. Lee, S. Adams, and J. Maier, Journal of The Electrochemical Society 147, 2407 (2000).Figure 1. Power curves for Ag/AgI/I2 battery operated between room temperature and 160C. Figure 1

Theoretical insights into the magneto-structural correlation: Comparison between series of copper(I) and silver(I) metal complexes with nitronyl nitroxide radicals

Using nitronyl nitroxide radicals, we presented a comparative study of magneto-structural correlations between series of CuI and AgI models (Cu(a) ∼ Cu(d) and Ag(a) ∼ Ag(d), modified from [CuI(immepy)2]PF6 and [AgI(impy)2]PF6 (Oshio et al., 1997). Cu(a) ∼ Cu(d) possess three characteristics that are significantly different from Ag(a) ∼ Ag(d) for the more utilization of CuI than that of AgI in the ferromagnetic joints of radical networks. (1) Structural shorter Cu-N length in Cu(a) ∼ Cu(d) than corresponding Ag-N length in Ag(a) ∼ Ag(d) leads to the quite larger Wiberg bond index (WBI), ∇2ρ(r) values, and metal atomic spin densities between triplet (T) and broken-symmetry (BS) states (ΔρT-BS) of the former than that of the latter. (2) From each of AgI (Ag(a) ∼ Ag(d)) to the corresponding one of CuI (Cu(a) ∼ Cu(d)), the spin density increases up to one or two order of magnitudes, which indicates the more notable spin delocalization from ONCN groups (paramagnetic centers) to CuI than that to AgI. Changing the dihedral angle (θ) between two radical components, the variation of the magnetic coupling constants (Jab) is directly proportional to the spin density of CuI but inversely proportional to that of one ONCN group. (3) Due to the larger d orbital distributions of CuI than that of AgI in the SOMOs, large metal-ligand charge transfer (MLCT) occurs in Cu(a) ∼ Cu(d) but little in Ag(a) ∼ Ag(d). The broken orthogonality is not evidently associated with the significantly different magnetic coupling interactions between CuI and AgI models.

Effects of Ag addition on properties and structure of Ge–Ga–Se–AgI chalcohalide glasses

An increasing amount of Ag metal was introduced in two GeSe2–Ga2Se3–AgI chalcohalide glasses with GeSe2/Ga2Se3 molar ratios of 1:1 and 2:1. Up to 25mol% Ag can be added in this GeSe2–Ga2Se3–AgI glass. The effects of Ag addition on some basic properties such as density, thermal stability, and optical band gap were investigated to have an overall understanding of GeSe2–Ga2Se3–AgI–Ag chalcohalide glasses. The modification of glass networks can be observed by Raman spectra and DSC measurements. Specifically, electrical conductivity was characterized by AC impedance spectra. The activation energy values of conductivity (Eσ) were obtained through Arrhenius linear fitting. The large amount of Ag in the systems led to high conductivity and low Eσ values. In general, several basic properties of the two series of novel glasses with different GeSe2/Ga2Se3 ratios were investigated in parallel and their potential as solid state conductive materials was evaluated.

Synthesis and optical properties of hybrid “plasmon-exciton” nanostructures based on Ag-AgI in nanoporous silica glass

The methods of “dry” synthesis of Ag-AgI hybrid nanostructures in the bulk of nanoporous silica glass with an average pore size of 17 nm have been described. Spectral characteristics of obtained nanocomposites have been presented. The possibility of forming the Fano resonance due to the electromagnetic coupling between AgI excitons and Ag plasmons has been shown.

Influence of the process variables on mechanosynthesis of AgI–Ag 2O–WO 3 system

The work studies the effect of selected milling variables on mechanosynthesis of the materials formed in the AgI–Ag 2O–WO 3 system. These variables were: a rotation speed, a milling time, a ball-to-powder mass ratio, a process control agent and a level of preliminary grinding of the reactant powders. The mechanosynthesis was carried out using Fritsch Pulverisette 7 and Fritsch Pulverisette Premium Line planetary mills. The X-ray diffraction method was applied for phase identification in the final product and for determination of their relative contents. It has been found out that: the synthesis leads to amorphous products and its efficiency is enhanced when: i) rotation speed and milling time are increased, ii) ball-to-powder mass ratio decreased and iii) starting powders are pre-ground. When the substrates are milled too long or applied milling speed is too fast, exceeding 600 rpm, then the process of amorphisation is impeded. The limit values of rotation speed and milling time are interrelated. Additionally they depend on the type of mill and applied mode of work. Preliminary grinding of the starting compounds enhances the milling efficiency. Addition of acetone, a control agent, to the milling batch reduces efficiency of production of amorphous phase.

Electrical transport and crystallization in Cu + ion substituted AgI–Ag 2O–V 2O 5 glassy superionic system

A new glassy solid electrolyte system Cu x Ag 1 − x I–Ag 2O–V 2O 5 has been synthesized. The structural, thermal and electrical properties of the samples have been investigated. The glassy nature of the samples is confirmed by X-Ray diffraction and Differential Scanning Calorimetry studies. The electrical conductivity of these samples increases with CuI content and approaches a maximum value of ∼ 10 − 2 Ω − 1 cm − 1 for x = 0.35 at room temperature. Ionic mobility measurements suggest that enhancement in the conductivity with Cu + ion substitution may be attributed to increase in the mobility of Ag + ions. The electrical conductivity versus temperature cycles carried out at well-controlled heating rate above T g and T c reveal interesting thermal properties. For lower CuI content samples conductivity exhibits anomalous rise above T g and subsequent fall at T c. It is also found that CuI addition into AgI–Ag 2O–V 2O 5 matrix reduces the extent of crystallization.

Study of ion diffusion in superionic crystals by EPMA and local CL

In this work the effect of ionic diffusion was studied in crystals AgI, HgI 2 and heterostructure Ag 2Hg 4I, obtained by a solid state chemical reaction (SSCR). The main aim was to characterize the structure of AgI–Ag 2HgI 4–HgI 2 p–n heterojunction and study the influence of a high power density electron beam on the ionic diffusion rate in this system. All structures were examined by electron probe microanalysis (EPMA) and local cathodoluminescence (CL). Dependence of elemental distribution and CL spectra on the p–n junction distance was revealed. Diffusion of Ag + ions was observed both in AgI crystals and through the interface of Ag 2HgI 4–HgI 2 in HgI 2 crystals.

Thermal- and Pressure-Induced Cooperative Spin Transition in the 2D and 3D Coordination Polymers {Fe(5-Br-pmd)z[M(CN)x]y} (M = AgI, AuI, NiII, PdII, PtII)

A new family of cyanide-based spin-crossover polymers with the general formula {Fe(5-Br-pmd)z[M(CN)x]y} [M=AgI (1), AuI (2), NiII (3), PdII (4), PtII (5); 5-Br-pmd=5-bromopyrimidine; z=1 or 2, x=2 or 4, and y=2 or 1] have been synthesized and characterized using single-crystal X-ray diffraction (XRD), X-ray powder diffraction (XRPD), magnetic susceptibility measurements, and differential scanning calorimetry (DSC). At 293 K, compound 1 presents the monoclinic space group C2/c, whereas at 120 K, it changes to the monoclinic space group P21/c. At 293 K, the crystal structure of 1 displays an uninodal three-dimensional network whose nodes, constituted of FeII, lie at the inversion center of an elongated octahedron. The equatorial bond lengths are defined by the N atoms of four [AgI(CN)2]- groups belonging to two crystallographically nonequivalent AgI atoms, Ag(1) and Ag(2). They are shorter than those of the axial positions occupied by the N atoms of the 5-Br-pmd ligands. The Fe-N average bond length of 2.1657(7) A is consistent with a high-spin (HS) state for the FeII ions. At 120 K, the crystal structure changes refer mainly to the FeII environment. There are two crystallographically independent FeII ions at this temperature, Fe(1) and Fe(2), which adopt the HS and low-spin (LS) states, respectively. The average Fe-N bond length for Fe(1) [2.174(5) A] and Fe(2) [1.955(5) A] agrees well with the reported magnetic data at this temperature. The spin transition of the FeII ions labeled as Fe(1) is found to be centered at Tc downward arrow=149 K and Tc upward arrow=167 K and accompanied by a drastic change of color from orange (HS) to red (LS). Magnetic susceptibility measurements under applied hydrostatic pressure performed on 1 have shown a linear displacement of the transition to higher temperatures while the hysteresis width remains unaltered in the interval of pressures of 105 Pa to 0.34 GPa. A further increase of the pressure induces the spin transition in the Fe(2) ions, which is completely accomplished at 1.12 GPa (T1/2=162 K). Compounds 1 and 2 are isostructural, but 2 does not exhibit spin-transition properties; the FeII centers remain in the HS state in the temperature range investigated, 5-300 K. Compounds 3-5 are not similar or isostructural with 1. A two-dimensional structure for 3-5 has been proposed on the basis of analytical data and the XRPD patterns. Compounds 3-5 undergo first-order spin transition where the critical temperatures for the cooling (Tc downward arrow) and warming (Tc upward arrow) modes are 170 and 180 K (3), 204 and 214 K (4), and 197 and 223 K (5), respectively. It is worth mentioning the color change from yellow to orange observed in 3-5 upon spin transition. The thermodynamic parameters associated with the spin transition estimated from DSC measurements are DeltaH=6 kJ mol(-1) (1), 11 kJ mol(-1) (3), 16 kJ mol(-1) (4), and 16 kJ mol(-1) (5) and DeltaS=38 J K(-1) mol(-1) (1), 62 J K(-1) mol(-1) (3), 76 J K-1 mol(-1) (4), and 81 J K(-1) mol(-1) (5).

Micro Raman, FT-IR/PAS, XRD and SEM studies on glassy and partly crystalline silver phosphate ionic conductors

Glassy and glassy-crystalline silver ion conductors of the AgI–Ag 2O–P 2O 5 system have been studied by FTIR-PAS and Micro Raman spectroscopies in conjunction with X-ray diffractometry, scanning electron microscopy and differential scanning calorimetry. It was found out that materials with lower (≤60 mol%) AgI contents are fully amorphous, while those with higher contents of AgI (>70 mol%) contain crystalline grains of β/γ-AgI embedded in the glassy matrix. Annealing of the glasses at 105 °C and/or 145 °C resulted in an increase in the formation of a yet unidentified crystalline phase dispersed in the glass. From the spectroscopic studies it was found that PO 4 3− units existed as separated species in the glass network or precipitated crystalline phases regardless the thermal treatment of the material. Vibrations of PO 4 3− units appeared to be affected by the total concentration of AgI and microstructure. The spectroscopic methods were also used to study crystallization process in the glassy samples.

XRD, SEM, Raman and DSC characterization of the materials of the AgI–Ag 2O–V 2O 5 system prepared by mechanosynthesis

Ion conducting materials of the AgI–Ag 2O–V 2O 5 system were prepared at room temperature via mechanosynthesis. Their crystallographic structure, microstructure, local dynamics and thermal properties were monitored by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and differential scanning calorimetry (DSC), respectively. It was found that the prolonged ball-milling of mixtures described by formulae: (i) xAgI·0.25(100 − x)(3Ag 2O·V 2O 5), for 40 ≤ x ≤ 70, and (ii) xAgI·0.2(100 − x)(3Ag 2O·2V 2O 5), for 0 ≤ x ≤ 60, led to the formation of amorphous materials. DSC scans and Raman spectra indicate that the thermal events in the mechanosynthesized materials and their main constituting units are similar to those observed for the glasses of the same compositions, prepared by a standard melt-quenching technique.

Conductivity, thermal behavior and microstructure of new composites based on AgI–Ag 2O–B 2O 3 glasses with Al 2O 3 matrix

A series of Ag +-ion conducting composites consisting of glasses of the AgI–Ag 2O–B 2O 3 system and hard Al 2O 3 powder matrix were synthesized by a high-pressure route (pressure 7.7 GPa, temperature 100–200 °C). The composition of the glasses was described by the general formula: xAgI·(100 − x)(0.667Ag 2O·0.333B 2O 3), where x = 40, 50 and 60. Alumina powder (2 μm average grain size) was added to the glass in 50/50 proportions (by volume). Conductivity, thermal behavior and microstructure of these composites are reported. Though the conductivity of the composites is lower than that of the constituent glasses, other properties like mechanical resistance to fracture are considerably improved.

Ionic conductivity of all-glass composites in the AgI–Ag 2O–P 2O 5 system

All-glass composites fabricated from mixtures of the superionic 33AgI·33Ag 2O·33P 2O 5 and 60AgI·20Ag 2O·20P 2O 5 glasses conduct Ag + ions. It is demonstrated that such composites can be easily formed by high-pressure methods. Their electric properties could be modelled by an equivalent electric circuit in which the ion conductivity of the bulk of a composite is represented by a single ‘effective resistance’. A related quantity—the effective ion conductivity, shows Arrhenius-like dependence. The effective activation energy and the effective preexponential factor both exhibit linear dependence on composition. The general mixing rule and the Uvarov model appeared to be unsuitable for the description of the effective conductivity of the all-glass composites as a function of composition and temperature. A new phenomenological model of effective conductivity is suggested and tested—proving its applicability.

Reverse Monte-Carlo Analysis of neutron diffraction from AgI–Ag 2S–AgPO 3 superionic conducting glasses

Neutron diffraction patterns from silver phosphate (AgPO 3), AgI–AgPO 3 and Ag 2S–AgPO 3 glasses were analysed by the Reverse Monte-Carlo method. The diffraction patterns were collected on the HIT-II spectrometer at KENS up to Q = 50 Å - 1 . The derived structural models of the salt-doped glasses were compared to AgPO 3 glass to correlate features of the atomic and molecular structure with observed superionic conduction in these glasses. A structural model based on extended chains of PO 4 tetrahedra, as reported previously by other researchers, provides a solid basis for all these glasses. The analysis indicates a strengthening of the Ag–Ag correlations and contrasting changes in the Ag–O correlations in the doped glasses. We also conclude that S largely displaces non-bridging O in the PO 4 tetrahedra in Ag 2S–AgPO 3 glass.

Effect of nanocrystallization on electrical conductivity of glasses and composites of the AgI–Ag 2O–B 2O 3 system

Amorphous and glassy–crystalline samples of the AgI–Ag 2O–B 2O 3 system with high content of AgI were prepared. It was shown that annealing of initially amorphous samples (with AgI content not higher than 60 mol%) leads to formation of crystalline grains of β-and γ-AgI and to a conductivity increase to 1.1·10 − 2 S cm − 1 at 20 °C (for AgI content of 55 mol%). The conductivity enhancement was attributed to interfacial regions surrounding crystalline grains. As-received samples with higher contents of AgI (≥ 75 mol% AgI) have high concentration of crystalline grains, mainly of AgI. The temperature dependence of conductivity undergoes step-like changes (close to 150 °C on heating and close to 120 °C on cooling). These changes are a consequence of the β-α-AgI phase transitions taking place in the crystallites.

Electrical properties and crystallization processes in AgI–Ag 2O–P 2O 5, [Ag 2O]/[P 2O 5] = 3, glasses

The effect of crystallization processes in the xAgI·0.75(100 − x)Ag 2O·0.25(100 − x)P 2O 5, 50 ≤ x ≤ 75, glasses on the ionic conductivity was investigated, using impedance spectroscopy, X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The crystallization was induced and promoted by thermal processing. It was found out that depending on annealing conditions, the conductivity could be enhanced or lowered. The conductivity enhancement is observed when the glass is annealed near the glass transition temperature T g for relatively short time. In this case, the XRD patterns do no indicate the presence of crystalline phases. The decrease of conductivity is observed for more pronounced crystallization, detectable by X-ray diffraction. The annealing does not affect the activation energy of ionic conductivity.

Relaxation of silver ions in fast ion conducting molybdate glasses

The conductivity relaxation in the frequency range from 10 Hz to 2 MHz and in the temperature range from 108 to 303 K for the fast ion conducting AgI–Ag 2O–MoO 3 glasses has been reported. It has been observed that the conductivity relaxation in these glasses is highly non-exponential and that the conductivity relaxation mechanism is independent of temperature but is dependent on composition. It has been further observed that the motion of Ag + ions is decoupled more and more from the viscous motion of the glassy matrix with the increase of AgI content in the composition, giving rise to the increase of the conductivity.

Transport and solid state battery characteristic studies of silver based super ion conducting glasses

Silverarsenotellurite (SAT), silverphosphotellurite (SPT) and silvervanadotellurite (SVT) quaternary glass systems were prepared with various formers compositions by a melt quenching method. Glass nature, glass transition temperature ( T g) and structure of the prepared glasses were identified respectively by X-ray diffraction (XRD), differential scanning calorimetric (DSC) and Fourier transform infrared (FT-IR) technique. Electrical conductivity studies were carried out by impedance measurement in the frequency range 40 Hz to 100 KHz at different temperatures for all three sets of AgI–Ag 2O–[TeO 2–M 2O 5] (M 2O 5 = As 2O 5, P 2O 5, V 2O 5) glasses. The high conducting compositions of SAT, SPT and SVT glass samples were fixed from the results of total conductivity ( σ t). Electronic conductivity ( σ e) studies were made on high conducting composition of each glass system by Wagner's polarization method. Total current ( i t) is due to ion and electron. Electronic current ( i e) due to electron were estimated through mobility studies. Ionic conductivity ( σ i) and ionic current ( i i) were calculated respectively using the conductivity ( σ t and σ e) and current ( i t and i e) results for the SAT, SPT and SVT glasses. Transport numbers due to ion ( t i) and electron ( t e) were calculated using the conductivity and mobility results for each glass system. The high conducting composition of the SAT, SPT and SVT glasses were used as solid electrolytes with silver metal as an anode and iodine:graphite (I:C) as a cathode for the fabrication of solid state batteries (SSBs). All the fabricated batteries were characterized by measuring the open circuit voltage (OCV) and polarization properties and estimated the batteries performances.

Crystallization studies on AgI–Ag 2O–MoO 3 superionic system synthesized by melt quenching and mechanical milling

Crystallization in the melt-quenched (MQ) and mechanically milled (MM) superionic systems has been thoroughly investigated using differential scanning calorimetry, X-ray diffraction and electrical conductivity measurements. It is observed that the two systems obey different crystallization processes. The conventionally melt-quenched samples exhibit only one crystallization peak near 112 °C, whereas, the mechanochemically synthesized samples show two well-separated crystallization peaks at T cl∼75–97 °C and T c2∼132±2 °C. The higher value of electrical conductivity in the mechanochemically synthesized samples (∼10 −2 Ω −1 cm −1 at 300 K) than the melt-quenched samples is attributed to the higher value of disorder (entropy) in the former.

Formation of superionically conducting amorphous phase in mechanically-milled AgI–Ag 2O–V 2O 5 system

Formation of highly ionically conducting and thermally stable amorphous phase during mechanical ball milling of AgI–Ag 2O–V 2O 5 system is discussed. It is found that the system with composition xAgI(100− x)–66.66Ag 2O–33.34V 2O 5 for x=50, 60 and 67 forms a highly conducting amorphous phase within 10–15 h of mechanical milling, confirmed by X-ray diffraction, glass ( T g) and amorphous to crystalline phase transition ( T c) temperatures. The ionic conductivity of mechanochemically synthesized samples is found to be ∼10 −2 Ω −1 cm −1 at room temperature, which is appreciably higher than that of the melt-quenched glass. These systems are found to be stable at least up to ∼80 °C as confirmed by differential scanning calorimetry measurements. A tentative mechanism of amorphous phase formation is proposed. It is demonstrated that silver iodide that diffuses in Ag 2O–M x O y matrix plays a key role in the formation of amorphous phase.

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H 2O 2 formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10 −4 to 4×10 −3 M glucose concentration (75–650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI–Ag 2S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.