Abusive testing of large Li/SOCl2 cells

Results are reported of various abuse tests conducted with lithium-thionyl chloride primary batteries of 2 000 A h and 10 000 A h capacity. The mechanical abuse tests, such as shock and vibration, showed that the large prismatic cells can now be built to satisfy typical military requirements. The thermal abuse tests showed that the cells can withstand a considerable overheating or a thermal shock treatment, as long as provisions were made for the thermal expansion of the electrolyte. The electrochemical abuse tests showed that the cells could be overdischarged (driven in reverse beyond discharge) to an equivalent of up to 50% of the discharge capacity with no adverse effects. The short circuit test, as a combination of the electrochemical and thermal abuse, was performed with no rupture, explosion or any other adverse effects on the surroundings.     

Investigation of positive electrode characteristics in high rate Li/SOCl2 cells

Operational characteristics of the positive electrode in high discharge rate Li/SOCl₂ batteries (with i > 60 mA cm⁻²) are investigated     

Reaction products on current or potential reversal in Li/SOCl2 cells

The products formed during abnormal operation due to current or potential reversal in Li/SOCl₂ cells have been identified by several complementary analytical techniques. In addition to the expected corrosion of cell components, the following compounds were found: Cl₂, SO₂, SO₂Cl₂, S₂Cl₂ and SCl₂. The presence of Cl₂O and ClO₂, reported earlier by others, has not been confirmed.     

Electrical analysis of Li/SOCl2 cell connected with electrochemical capacitor

A Li/SOCl₂ bobbin-type cell, connected in parallel with an electrochemical capacitor, is investigated in order to overcome the voltage delay problem at high-rate discharge. In spite of the high internal resistance of the Li/SOCl₂ cell due to the passivation, the voltage delay is suppressed. Impedance measurements, in which the cell is separated from the capacitor, explain the suppression process clearly. The electrochemical capacitor operates as a high-current buffer and voltage-delay suppressor for the Li/SOCl₂ bobbin-type cell.     

Raman spectroscopic studies of the structure of electrolytes used in the Li/SOCl2 battery

The importance of the Li/SOCl₂ cell using thionyl chloride as a liquid cathode has given rise to studies of the structure of the electrolytes used in this lithium cell. The electrolytes are made from LiAlCl₄ dissolved in SOCl₂ in which SO₂ is formed during the discharge process. This paper deals with a structural study, using Raman spectroscopy, of solutions of LiAlCl₄ in pure SOCl₂ and SO₂, and in mixtures of both solvents. The complexes |Li(SOCl₂)₂|⁺|AlCl₄|^? and |Li(SO₂)₃|⁺|AlCl₄|^? were characterized at room temperature in the pure solvents SOCl₂ and SO₂, respectively. In the ternary system LiAlCl₄SOCl₂SO₂ the existence of |Li(SO₂, SOCl₂)|⁺|AlCl ₄|^? was established.     

Primary Li/SOCl2 cells. X. Optimization of D cells with respect to energy density,storability and safety

Hermetically-constructed Li/SOCl₂ D cells were used for the studies reported in this publication. Optimization with respect to energy density resulted in a capacity recovery of 18 – 19 A h at 3.5 volt at 25 °C, at 0.01 A corresponding to 20 W h/in.³ (1.24 W h/cm³) and 300 W h/lb. (661 W h/kg). The optimization with respect to storability resulted in cells having no voltage-delays after three months of storage at 72 °C and test at ?30 °C at 3.0 A. The optimization with respect to safety resulted in cells which are resistant to abuses such as shorting and force-discharge. Approaches have also been developed to stabilize the partially-discharged cells and thus prevent spontaneous explosions on storage.     

Chemical and structural optimization of ZnCl2 activated carbons via high temperature CO2 treatment for EDLC applications

Development of biomass based activated carbon materials for electrical double layer capacitor (EDLC) usage has gained attention as a result of requesting efficient and low cost energy storage device production. In this study, pine cone based activated carbons were produced with a combined chemical and physical activation route. ZnCl₂ and CO₂ were used for chemical and physical activation of the material, respectively. Activation parameters are adjusted to give different chemical and textural characteristics. FTIR and Raman spectroscopies were used for functional group identification and structural order characterization, respectively. As a result, efficient active materials for EDLC usage were obtained, with as high as 87 F/g specific capacitance in organic electrolytes.     

Enhancing the elevated temperature performance of Li/LiMn2O4 cells by reducing LiMn2O4 surface area

Lithium-rich spinels were obtained with the same structure but different surface area by two different synthesis routes, namely the “once-annealed” and the “twice-annealed” methods. The elevated temperature performance of Li/Li_1+xMn₂O₄ cell is significantly improved using a spinel cathode with a small surface area: the cell at 50°C lost 5% of the initial capacity over the first 100 cycles based on a spinel cathode with the small surface area of 1.2 m²/g compared to 8% based on a large one of 6.2 m²/g. Also the mechanism responsible for the reaction of LiMn₂O₄ with LiOH to form lithium-rich spinel has been investigated.     

A possible mechanism for the reduction of voltage delay in the Li/SOCl2 system via cyanoacrylate coatings on lithium

Scanning electron microscopy and X-ray photoelectron spectroscopy were used to investigate the passivation of lithium treated with alkyl 2-cyanoacrylates in LiAlCl₄/SOCl₂ electrolyte. Cyanoacrylate coatings reduce anode polarization by affecting the morphology and growth kinetics of the LiCl passivating film. The mechanism for these effects depends on the gradual dissolution of the coating in electrolyte and its subsequent replacement by LiCl. Dissolving either the monomer or polymer form of cyanoacrylate directly into the electrolyte without coating the lithium also affects LiCl film growth and reduces polarization.     

Study of glasses/glass-ceramics in the SrO-ZnO-SiO2 system as high temperature sealant for SOFC applications

Glasses having composition (in wt.%) 51SrO-9ZnO-(40−x)SiO₂ (SZS), where x represents the additives like B₂O₃, Al₂O₃, V₂O₅, and Cr₂O₃, were prepared by melt-quench method and transformed into glass-ceramics by controlled crystallization based on differential thermal analysis (DTA) data. Glasses and glass-ceramics were characterized using dilatometry, X-ray diffraction (XRD), microhardness, and Raman spectroscopy. XRD revealed that glass-ceramics are composed of mainly Sr₂ZnSi₂O₇ and SrSiO₃ crystalline phases along with residual glassy phase. Raman spectroscopy showed that main constitutes of the glass network are the Q¹ and Q² silicate structural units. With the addition of B₂O₃ and other additives silicate glass network depolymerizes and concentration of Q¹ structural units increases at the expense of Q² units. Formation of phases during crystallization depends on the presence of different silicate structural units in the glass matrix. B₂O₃ goes into the glass network as triangular (BO₃) borate structural units and at higher concentration of B₂O₃, only a part of the B₂O₃ forms tetragonal (BO₄) structural units. Investigated glasses and glass-ceramics have thermal expansion coefficient (TEC) in the range of 105-120 × 10⁻⁷/°C which matches with TEC of other cell components. B₂O₃ containing SZS glasses show good adhesion/bonding with YSZ and Crofer 22 APU. Elemental line scans indicate that interdiffusion of Fe, Cr and Si across interface is responsible for good bonding with Crofer 22 APU and interdiffusion of Sr, Si, Y and Zr is responsible for good bonding with YSZ.     

Effect of high temperature steam annealing for SiO2 passivation

We introduced high-temperature steam annealing (HSA) as a low-cost and effective post-annealing method for c-Si solar cell processing. The annealing effects were analyzed by measuring effective lifetime and C–V characteristics and were compared with the effects of forming gas annealing (FGA) and hydrogen-radical annealing (HRA). By using this method, effective lifetime of a SiO₂-coated wafer was increased in a very short annealing time compared to the conventional FGA. It was determined that the improvement of lifetime by HSA can be attributed to the decrease of interface state density.     

Study on stretch extinction limits of CH4/CO2 versus high temperature O2/CO2 counterflow non-premixed flames

Extinction limits of counterflow non-premixed flames with normal and high temperature oxidizers were studied experimentally and numerically for development of new-type oxygen-enriched mild combustion furnace. Extinction stretch rates of CH₄/CO₂ (at 300 K) versus O₂/CO₂ flames at oxygen mole fractions of 0.35 and 0.40 and oxidizer temperatures of 300 K, 500 K, 700 K and 1000 K were obtained. Investigation was also conducted for CH₄/N₂ (at 300 K) versus air (O₂/N₂) flames at the same oxidizer temperatures. An effect of radiative heat loss on stretch extinction limits of oxygen-enriched flames and air flames was investigated by computations with optical thin model (OTM) and adiabatic flame model (ADI). The results show influence of radiative heat loss on stretch extinction limits was not significant in relative high fuel mole fraction regions. The extinction curve of the oxygen-enriched flames with oxygen mole fraction of 0.35 was close to that of the air flames at the oxidizer temperature of 300 K. However, the extinction curve of air flames with high temperature oxidizer was comparable with that of oxygen-enriched flames with oxygen mole fraction of 0.40. Scaling analysis based on asymptotic solution of stretch extinction was applied and it was found that stretch extinction limits can be expressed by two terms. The first term is total enthalpy flux of fuel stream based on thermo-physical parameters. The second term is a kinetic term which reflects an effect of the chemical reaction rate on stretch extinction limits. OH radicals which play important roles in chain propagating and main endothermic reactions were used to represent the kinetic term of both oxygen-enriched and air flames. The global rates of OH formation in these two cases were compared to understand the contribution of kinetic term to stretch extinction limits. Variation of extinction curves of oxygen-enriched flames and air flames was well explained by the present scaling analysis. This offers an effective approach to estimate stretch extinction limits of oxygen-enriched flames based on those of air flames at the same oxidizer temperature.     

Button cells based on the Li/Bi2O3 couple

Lithium button cells (1.5 V) with thermally treated Bi₂O₃ cathodes (additive free), mainly of 11.4 × 3.4 mm standard size (100 mA h), have been constructed. They are characterized by high volumetric energy densities even at high discharge rates. The cell behaviour is also satisfactory after 1 year's storage, at low temperature (?10 °C), and under 500 μA pulses. Comparison with analogous Li cells (Li/FeS₂ and Li/Pb₂Bi₂O₅) or aqueous cells (Zn/HgO and Zn/Ag₂O) confirms the usefulness of this system as a power source for microelectronic devices. This was also substantiated by field tests.     

Influence of the electronic configuration of the central metal ions on catalytic activity of metal phthalocyanines to Li/SOCl2 battery

The relative energy of Li/SOCl₂ battery whose electrolyte contains the transition metal phthalocyanines is used to evaluate the catalytic activity of the compounds. The energy of Li/SOCl₂ battery whose electrolyte contains transition metal phthalocyanines-tetracarboxylic acid (MPcTc) and metal phthalocyanines-tetrasulfonic acid (MPcTs) (M = Mn²⁺, Ni²⁺) increases by approximately 62–106%, the energy of Li/SOCl₂ battery whose electrolyte contains MPcTc and MPcTs (M = Fe²⁺, Co²⁺) increases by approximately 32–52%, and the energy of Li/SOCl₂ battery whose electrolyte contains CuPcTc and CuPcTs is similar to that of the cell in the absence of these complexes. It shows that the electronic configuration of the central metal ion strongly influences the catalytic activity of metal phthalocyanine to Li/SOCl₂ battery. To the same ligand, the compound whose central metal ion with electronic configuration d⁹ is inactive; the compound whose central metal ion with electronic configuration d⁴ or d⁸ exhibits relatively high catalytic activity; and the compound whose central metal ion with electronic configuration d⁵ or d⁷ exhibits relatively low catalytic activity. Three possible routes of catalytic reduction of SOCl₂ by transition metal phthalocyanine compound are proposed to interpret the results.     

Energy conversion by spontaneously reacting LiSO2 cells

In abuse tests LiSO₂ cells were exploded in a detonation chamber and in calorimeters. The energy measurements show that when air is present, the energy released is six times that obtained by electrically discharging the cells. In the absence of air the energy is reduced to one third.Reactions which may perhaps occur in the two cases are described and the heats of reaction are calculated. The calculated values are in fair agreement with those obtained experimentally.By comparing the pressure increase, it has been shown that the cell explosion is not as fast as the detonation of TNT. It is, however, faster than the combustion of the gunpowder used for comparison.     

Unique TiO2 paste for high efficiency dye-sensitized solar cells

A novel titanium oxide paste based on Pechini sol-gel method and nanocrystalline titanium oxide powder have been successfully developed. Titanium oxide layers possess high inner surface area assuring high dye loading and well-connected nanocrystalline grains assuring good electron transport within the layer. The dye-sensitized layers have been used to assemble dye-sensitized solar cells with acetonitrile- and ionic liquid-based electrolyte. Overall conversion efficiencies of dye-sensitized solar cells (DSSCs) determined under standard test conditions (100 mW/cm², 25 °C and AM 1.5 G) are 10.2% for acetonitrile and 7.3% for ionic liquid-based electrolyte.     

SnO2 functionalized AlGaN/GaN high electron mobility transistor for hydrogen sensing applications

In this study, we report on a demonstration of hydrogen sensing at low temperature using SnO₂ functionalized AlGaN/GaN high electron mobility transistors (HEMT). The SnO₂ dispersion was synthesized via a hydrothermal method and selectively deposited on the gate region of a HEMT device through a photolithography process. The high electron sheet carrier concentration of nitride HEMTs provides an increased sensitivity relative to simple Schottky diodes fabricated on GaN layers. The morphology and crystalline properties of the SnO₂-gate, together with the texture of the multilayer films on the device were investigated by SEM, HRTEM, EDS and XRD. The effects of annealing treatment on the crystalline properties of the SnO₂-gate, and gas sensing properties of SnO₂-gated HEMT sensors were studied. The SnO₂-gated HEMT sensor showed fast and reversible hydrogen gas sensing response at low temperature.     

Doped TiO2 for solar energy applications

TiO₂ samples were prepared from TiCl₃ solution or TiCl₄ with or without 0.5a/o Cr, 0.5a/o Mn or 0.25a/o of each. The samples were heated under vacuum (for 6 hrs) at 600°C or in H₂/N₂ (for 6.5 hrs) at 500°C. Two Cr-doped samples were loaded with RuO₂ (using RuCl₃ solutions). The reflectance spectra of the powders were recorded using a Perkin Elmer 330 spectrophotometer over the range 200–800 nm. The spectra of the undoped and Cr-doped samples demonstrated the increased visible absorption on doping, with further improvements on heating and after RuO₂-loading. The effects were more marked for the samples prepared from TiCl₃. The Mn-doped samples and the Cr/Mn-doped samples exhibited similar trends of increased absorption. Maximum visible absorption was observed for the Mn-doped or Cr/Mn-doped samples, the improvement surpassing the effect of Ru-loading of Cr-doped samples. The effect of the latter was more pronounced for the sample prepared from TiCl₃ compared to TiCl₄. Little effect on the spectrum resulted from irradiation with visible light. Preliminary work on the reduction of CO₂ solution containing EDTA in a suspension of Pt-loaded TiO₂, demonstrated the formation of HCHO on irradiation with a medium pressure mercury lamp. The latter was determined by gas chromatography and colorimetrically.     

Comparison of the electrochemical properties of LiBOB and LiPF6 in electrolytes for LiMn2O4/Li cells

The electrochemical stability and conductivity of LiPF₆ and lithium bis(oxalato)borate (LiBOB) in a ternary mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were compared. The discharge capacities of LiMn₂O₄/Li cells with the two electrolytes were measured at various current densities. At room temperature, LiMn₂O₄/Li cells with the electrolyte containing LiBOB cycled equally well with those using the electrolyte containing LiPF₆ when the discharge current rate was under 1 C. At 60 °C, the LiBOB-based electrolyte cycled better than the LiPF₆-based electrolyte even when the discharge current rate was above 1 C. Compared with the electrolyte containing LiPF₆, in LiMn₂O₄/Li cells the electrolyte containing LiBOB exhibited better capacity utilization and capacity retention at both room temperature and 60 °C. The scanning electron microscopy (SEM) images and the a.c. impedance measurements demonstrated that the electrode in the electrolyte containing LiBOB was more stable. In summary, LiBOB offered obvious advantages in LiMn₂O₄/Li cells.