Development of a BB-2590/U rechargeable lithium-ion battery

PolyStor has teamed with Hawker Eternacell (US) to develop a BB-2590/U rechargeable lithium-ion battery under contract with the US Army CECOM (Ft. Monmouth, NJ, USA). The concept involves using commercially available ICR-18650 cylindrical lithium-ion cells. The individual cells have a high specific energy of 135 Wh kg⁻¹ and an energy density of 335 Wh dm⁻³. Electronic circuitry was developed to provide pack protection, charge equalization and battery management (fuel gauging). PolyStor's rechargeable BB-2590/U battery provides 4.5 Ah at 28 V nominal or 9.0 Ah at 14 V nominal, translating into 108 Wh kg⁻¹ and 150 Wh dm⁻³. The key developments are discussed in this paper.     

A new electrode for a poly(pyrrole)-based rechargeable battery

The use of dodecylbenzenesulfonate-doped poly(pyrrole) films, PPYDBS, as a secondary battery electrode was studied. The redox and morphologic properties of these films are suitable for battery application. Films were synthesized by electrolysis of pyrrole and sodium dodecylbenzenesulfonate aqueous solutions with a current density of 1.0 mA cm⁻² and were switched in LiC1O₄ 1.0 M propylene carbonate solutions (PC) by cyclic voltammetry. In these experiments an apparent diffusion coefficient of 3.7x10⁻⁹ cm²s⁻¹ has been found. Charge/discharge tests at ±50, ±100, ±150 and ±200 μA cm⁻² were done for a PPYDBS/ LiC1O₄, PC/Li battery. The open-circuit voltage was 3.2 V after 30 h, the specific capacity 53 A h kg⁻¹ and the energy density 154 W h kg⁻¹. These values indicate that this polymer can be used as an electrode in a rechargeable battery.     

Electrical and electrochemical performance characteristics of large capacity lithium-ion cells

We are currently evaluating large capacity (20–40 Ah) Bluestar (cylindrical) and Yardney (prismatic) lithium-ion cells for their electrical and electrochemical performance characteristics at different temperatures. The cell resistances were nearly constant from room temperature down to −20°C, but increased by over 10 times at −40°C. The specific energies and powers, as well as the energy densities and power densities are high and did not reach a plateau even at the highest discharge rates tested. For example, the prismatic lithium-ion cells gave close to 280 Wh dm⁻³ from a 4 A discharge and 249 Wh dm⁻³ at 20 A, both at room temperature. For the same current range the specific energy values were 102 Wh kg⁻¹ and 91 Wh kg⁻¹. Cycle life and other electrical and electrochemical properties of the cells will be presented.     

Synthesis of polyaniline/graphite composite as a cathode of Zn-polyaniline rechargeable battery

The characteristics of polyaniline/graphite composites (PANi/G) have been studied in aqueous electrolyte. PANi/G films with different graphite particle sizes were deposited on a platinum electrode by means of cyclic voltammetry. The film was employed as a positive electrode (cathode) for a Zn-PANi/G secondary battery containing 1.0 M ZnCl₂ and 0.5 M NH₄Cl electrolyte at pH 4.0. The cells were charged and discharged under a constant current of 0.6 mA cm⁻². The assembled battery showed an open-circuit voltage (OCV) of 1.55 V. All the batteries were discharge to a cut off voltage of 0.7 V. Maximum discharge capacity of the Zn-PANi/G battery was 142.4 Ah kg⁻¹ with a columbic efficiency of 97–100% over at least 200 cycles. The mid-point voltage (MPV) and specific energy were 1.14 V and 162.3 Wh kg⁻¹, respectively. The constructed battery showed a good recycleability. The structure of these polymer films was characterized by FTIR and UV–vis spectroscopies. Electrochemical impedance spectroscopy (EIS) was used as a powerful tool for investigation of charge transfer resistance in cathode material. The scanning electron microscopy (SEM) was employed as a morphology indicator of the cathodes.     

A rechargeable lithium battery employing a porous thin film of Cu3+δMo6S7.9

Porous, thin films of copper molybdenum sulfides (Cu_3+δMo₆S_7.9), that have been prepared by the technique of painting and subsequent reaction with mixed H₂/H₂S gases at 500 °C, have been used as a cathode material for lithium secondary batteries. The test cell comprised: Li/2 M LiClO₄ in PC-THF (4:6)/Cu_3+δMo₆S_7.9 (porous, thin film). The discharge reaction proceeded via the intercalation of lithium ions into the structural interstices of the cathode material.

The first discharge curve of the cell showed that the porous film could incorporate up to 18 lithium ions per formula unit. The capacity of the thin film was four times higher than that previously reported for powder or pressed-pellet electrodes. The theoretical energy density was 675 W h kg⁻¹, i.e., higher than that of TiS₂ (455 W h kg⁻¹) which is one of the best materials for high-energy lithium batteries. From X-ray diffraction studies of the lithium incorporated in the thin film at each discharge step, it is suggested that there are four incorporation reactions of lithium ions into the cathode. Finally, cycling tests have been conducted at room temperature.     

Miscanthus sinensis ‘giganteus’ production on several sites in Austria

In Austria it is planned to use Miscanthus sinensis ‘Giganteus’ as a renewable energy source. The influence of site, age of crop and time of harvest on yield, water content, nitrogen content and quality was investigated. In the first year the yield was 0.7 to 2 t dry matter ha⁻¹, in the second year 7.9 to 15.5 t ha⁻¹ and in the third year 17.4 to 24.5 t ha⁻¹. In February of the first year the water content was 40 to 50%, in the second year 34 to 49% and in the third year 24 to 38%. Sufficient precipitation (about 800 mm) in mild climates is required for high yields. On sites with more rain the water content of the plants was higher. Water and nitrogen content decreased significantly during the six week period from January to the end of February. In February of the first year the nitrogen content was 7.8 to 16.6 g kg⁻¹ dry matter, in the second year 3.7 to 6.2 g kg⁻¹ and in the third year 2.6 to 7.5 g kg⁻¹. The calorific value was as high as that of firewood (18 to 19 MJ kg⁻¹ ). The ash content exceeded firewood but was lower than that of straw. By the third year of cultivation 60 to 150 kg N ha⁻¹, 100 to 200 kg K20 ha⁻¹, 10 to 35 kg P₂ O₅ ha⁻¹, 10 to 25 kg MgO ha⁻¹ and 20 to 35 kg CaO ha⁻¹ had to be taken up by the harvest at the end of February.     

Synthesis and electrochemical studies of the 4 V cathode, Li(Ni2/3Mn1/3)O2

Layered Li(Ni_2/3Mn_1/3)O₂ compounds are prepared by freeze-drying, mixed carbonate and molten salt methods at high temperature. The phases are characterized by X-ray diffraction, Rietveld refinement, and other methods. Electrochemical properties are studied versus Li-metal by charge–discharge cycling and cyclic voltammetry (CV). The compound prepared by the carbonate route shows a stable capacity of 145 (±3) mAh g⁻¹ up to 100 cycles in the range 2.5–4.3 V at 22 mA g⁻¹. In the range 2.5–4.4 V at 22 mA g⁻¹, the compound prepared by molten salt method has a stable capacity of 135 (±3) mAh g⁻¹ up to 50 cycles and retains 96% of this value after 100 cycles. Capacity-fading is observed in all the compounds when cycled in the range 2.5–4.5 V. All the compounds display a clear redox process at 3.65–4.0 V that corresponds to the Ni^2+/3+–Ni^3+/4+ couple.     

Performance characteristics of Ultralife's solid polymer rechargeable batteries

Ultralife Batteries delivered the world's first commercial shipments of solid polymer rechargeable batteries in 1997. The battery consists of a Li_xMn₂O₄⁻ based cathode, graphite anode and proprietary polymeric separator. Energy density of the batteries exceeds 120 W h kg⁻¹ and 200 W h dm⁻³ at the C rate. Pulse capability up to 5 C has been demonstrated. More than 90% of the initial C rate capacity remains after 500 continuous cycles at room temperature. These solid polymer rechargeable batteries also show good low and high temperature performance and have good safety characteristics.     

The polyaniline/lithium battery

Polyaniline (PAn), synthesized by electro-polymerization, has exhibited good reversibility in an LiClO₄/propylene carbonate electrolyte. The reversible specific capacity reaches 120 A h kg⁻¹. PAn appears to be a candidate positive electrode for a secondary lithium battery because of its reversibility, high-rate discharge performance, and low self-discharge. The compatibility of the electrolyte between PAn and lithium electrodes is an important problem to be solved.     

Emission factors of wood and charcoal-fired cookstoves

In the developing countries, energy required for cooking often has the biggest share in the total national energy demand and is normally met mostly by biomass. This paper presents the results of experimental studies on emission conducted on a number of traditional and improved cookstoves collected from different Asian countries using wood and charcoal as fuel. The emission factors from this study are comparable to those reported in the literature. In the case of wood combustion, CO₂ emission factor is in the range of 1560–1620 g kg⁻¹. The emission factors for pollutants CO, CH₄, TNMOC and NO_x were in the ranges 19–136, 6–10, 6–9 and 0.05–0.2 g kg⁻¹, respectively. In the case of charcoal combustion, CO₂ emission factor is in the range of 2155–2567 g kg⁻¹. The emission factors for pollutants CO, CH₄, TNMOC were in the ranges 35–198, 6.7–7.8, 6–10 g kg⁻¹, respectively.

Comparison between wood and charcoal fired stoves shows that, CO₂ and CO emission factor values for wood are lower as compared to charcoal. CH₄ and TNMOC emission factors for wood are with the same range as compared to charcoal. Emission factors for NO_x using wood is slightly lower than charcoal. The emission of all the pollutants per unit of useful heat was found to decrease with increasing stove efficiency for both wood and charcoal fired stoves.     

Solvent effects on rechargeable lithium cells

The behaviour of several solvents in rechargeable lithium cells employing two different structure type cathodes, ns-V₆O₁₃ a framework oxide, and TiS₂ a layered material, was compared. Excellent cycling behaviour and high energy were obtained for the Li/ns-V₆O₁₃ cell at current densities as high as 5 mA cm⁻² in the temperature range 25 to −40 °C. Cells utilizing an electrolyte of 2 M LiAsF₆ in methyl formate were discharged at a current density of 2 mA cm⁻² at −40 °C with 37% cell efficiency at an energy density of 255 W h kg⁻¹ (based on active material). Use of an LiAsF₆/2-MeTHF electrolyte with ns-V₆O₁₃ resulted in satisfactory cycle-life, but at significantly reduced capacities than observed with the LiAsF₆/MF electrolyte. This is attributed to the lower conductivities of 2-MeTHF solutions.

The results for Li/TiS₂ cells are in direct contrast with those observed for ns-V₆O₁₃. Use of MF solutions with TiS₂ results in extremely low capacities while capacities and cycle life in 2-MeTHF solutions are quite good. These differences are attributed to a combination of factors including solvent co-intercalation, ion salvation, and solvent decomposition.     

Fibrous polyaniline as positive active material in lithium secondary batteries

Fibrous polyaniline (f-PANI) has displayed a maximum discharge capacity of 164 A h kg⁻¹, a low rate of self-discharge, and a long life as a positive active material in a secondary lithium battery.     

High-temperature superconductor, YBa2Cu307-x as all- solid-state lithium cell

The utility of the high-temperature superconductor, YBa₂Cu₃O_7-itx, as the cathode material for an all-solid-state lithium cell has been examined. The capacity of YBa₂Cu₃O₇-x, is 223 mA h g⁻¹ and the discharge efficiency is> 92%. Measurements of a.c. impedance show that the charge-transfer resistance at the interface of the electrolyte/cathode is very low and increases with the depth-of-discharge of the battery. Studies using X-ray photoelectron spectroscopy (XPS) reveal that the cathode becomes doped with Li⁺ ions as the cell discharges.     

Kinetics of the NCO radical reacting with atoms and selected molecules

Rate constants for the reaction of isocyanate radicals (NCO) in its electronic ground state ( ²Π) with oxygen atoms were determined at 2.5 Torr total pressure in the temperature range 302–757 K. Excimer laser photolysis (ELP) of chlorine isocyanate (ClNCO) produced NCO radicals detected by laser-induced fluorescence (LIF). The reaction NCO + O exhibits a negative temperature dependence, described by the two-parameter equation: k_NCO+O(T) = (4.3_−2.2^+3.2) × 10⁻⁸ × T^{−1.14_−0.12+0.08} cm³ molecule⁻¹ s⁻¹. Measurements at 298 K and total pressures of 2.5 and 9.9 Torr, respectively, indicated a slight pressure dependence. For the reaction of NCO radicals with hydrogen atoms, the rate constant k_NCO+H = (2.2 ± 1.5) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹was obtained at 298 K and a total pressure of 2.6 Torr for the first time by a direct measurement. From a single measurement k = (3.8 ± 1.6) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ was determined at 548 K and 2.4 Torr total pressure. In addition, rate constants for the reactions of NCO radicals with molecular oxygen (O₂), carbon dioxide (CO₂), molecular hydrogen (H₂), and carbon monoxide (CO), which is a dissociation product of CO₂ in a microwave discharge, were measured at two different temperatures. At room temperature these reactions were slow and at the detection limit of the ELP/LIF technique. However, at elevated temperatures at least the rate constants of the reactions NCO + O₂ and NCO + H₂ become significantly larger and, therefore, should be taken into account, when modeling combustion processes under certain conditions.     

Fast cycling of Li/LiCoO2 cell with low-viscosity ionic liquids based on bis(fluorosulfonyl)imide [FSI]

A charge–discharge cycling test of a Li/LiCoO₂ cell containing ionic liquids based on bis(fluorosulfonyl)imide ([FSI]⁻) as the electrolyte media, revealed significantly better rate properties compared to those of cells using conventional ionic liquids. The use of an 1-ethyl-3-methylimidazolium (EMI⁺) salt permitted the retention of 70% of the discharge capacity at a 4 C current rate. In contrast, similar performance of cells containing N-methyl-N-propylpyrrolidinium (Py₁₃⁺) and N-methyl-N-propylpiperidinium (PP₁₃⁺) salts of [FSI]⁻ was limited to operation at 2 and 1 C current rates, respectively. However, the charge/discharge cycling stability of the cell with Py₁₃[FSI] was much better than that of the cell using EMI[FSI].     

Analysis of solar chemical processes for hydrogen production from water splitting thermochemical cycles

This paper presents a process analysis of ZnO/Zn, Fe₃O₄/FeO and Fe₂O₃/Fe₃O₄ thermochemical cycles as potential high efficiency, large scale and environmentally attractive routes to produce hydrogen by concentrated solar energy. Mass and energy balances allowed estimation of the efficiency of solar thermal energy to hydrogen conversion for current process data, accounting for chemical conversion limitations. Then, the process was optimized by taking into account possible improvements in chemical conversion and heat recoveries. Coupling of the thermochemical process with a solar tower plant providing concentrated solar energy was considered to scale up the system. An economic assessment gave a hydrogen production cost of 7.98$ kg⁻¹ and 14.75$ kg⁻¹ of H₂ for, respectively a 55 MW_th and 11 MW_th solar tower plant operating 40 years.     

Crystal chemistry modification of lithium nickel cobalt oxide cathodes for lithium ion rechargeable batteries

As a cathode material for lithium ion rechargeable batteries, LiNi_0.8Co_0.2O₂ (LNCO) is one of the most attractive candidates for high power electronic devices. In the present work, we have synthesized LNCO powder by solid-state route. The discharge capacity and the capacity retention of LNCO cathode are found to be 100 mAh g⁻¹ and 63%, respectively. Molybdenum doping, replacing parts of cobalt ion in LNCO lattice increases the discharge capacity (157 mAh g⁻¹) and improve its capacity retention characteristics. Through X-ray Rietveld analyses, we have found that Mo doping increases the inter-slab spacing between the (Co,Ni)O₂ octahedral layers which provides easier Li¹⁺ intercalation leading to improved electrochemical properties in the modified cathode.     

Structural and electrochromic properties of nanosized Fe/V-oxide films with FeVO4 and Fe2V4O13 grains: comparative studies with crystalline V2O5

Various mixed Fe/V-oxides can be used as anodes in Li⁺ rocking chair batteries, however, their small optical modulation during the insertion/extraction of Li⁺ ions makes them candidates for the counter electrodes in electrochromic (EC) devices. The sol–gel route in combination with dip-coating deposition was used for the preparation of Fe/V-oxide films with molar ratios Fe:V=0.1:1, 1:2, 1:1 and 2:1. X-ray diffraction combined with Fourier transform infrared (FT-IR) spectroscopy studies of films and powders reveal that heating of xerogel films at 400°C produces films with nanosized FeVO₄ (Fe:V=1:1) and Fe₂V₄O₁₃ (Fe:V=1:2) grains, while the corresponding crystalline powders were obtained at 500°C (8 h). Charge capacities (Q) of Fe/V-oxide films (300 and 400°C) were determined using cyclic voltammetry (CV) from 1.5 to −1.5 V vs. Ag/AgCl (4.8 to 1.8 V vs. Li) in 1 M LiClO₄/propylene carbonate (PC) electrolyte. Our results revealed that Q values of Fe/V-oxide films are up to 20 mC cm⁻² depending on the thickness (40–100 nm), temperature of heating and the Fe:V molar ratio (1:2, 1:1). During the first 300 cycles the cycling stability of the Fe-containing films is better than that of V₂O₅ crystalline films. UV-visible spectra of charged/discharged films revealed that these films, similar to V₂O₅ films, exhibit a mixed anodic/cathodic electrochromism. It was established that with regard to the colouring/bleaching changes of V₂O₅ crystalline films, the Fe/V-oxide films exhibit smaller cathodic colouring at wavelengths λ>600 nm and higher visible transmittance. IR spectroscopy of charged/discharged Fe/V-oxide films confirmed that the reduction of Fe³⁺ prevents the overreduction of V⁵⁺ to V³⁺, which takes place in V₂O₅ films cycled in the same potential range.     

Electrocatalysis for dioxygen reduction by a μ-oxo decavanadium complex in alkaline medium and its application to a cathode catalyst in air batteries

The redox behavior of a decavanadium complex [(V=O)₁₀(μ₂-O)₉(μ₃-O)₃(C₅H₇O₂)₆] (1) was studied using cyclic voltammetry under acidic and basic conditions. The reduction potential of V(V) was found at less positive potentials for higher pH electrolyte solutions. The oxygen reduction at complex 1 immobilized on a modified electrode was examined using cyclic voltammetry and rotating ring-disk electrode techniques in the 1 M KOH solutions. On the basis of measurements using a rotating disk electrode (RDE), the complex 1 was found to be highly active for the direct four-electron reduction of dioxygen at −0.2 V versus saturated calomel electrode (SCE). The complex 1 as a reduction catalyst of O₂ with a high selectivity was demonstrated using rotating ring-disk voltammograms in alkaline solutions. The application of complex 1 as an oxygen reduction catalyst at the cathode of zinc–air cell was also examined. The zinc–air cell with the modified electrode showed a stable discharge potential at approximately 1 V with discharge capacity of 80 mAh g⁻¹ which was about five times larger than that obtained with the commonly used manganese dioxide catalyst.     

Structural and electrochemical properties of Li1+xNi0.5Mn0.5O2+δ (0 ≤ x ≤ 0.7) cathode materials for lithium-ion batteries

A comparative analysis of the properties of LiNi_0.5Mn_0.5O₂ and Li_1+xNi_0.5Mn_0.5O₂ (0.2 ≤ x ≤ 0.7) powders, obtained by the freeze drying method, was performed. Lattice parameters of Li_1+xNi_0.5Mn_0.5O₂ decreased considerably with growing amounts of Li until x = 0.3; at x > 0.5 trace amounts of Li₂MnO₃ are observed by X-ray diffraction (XRD) patterns. X-ray photoelectron spectroscopy (XPS) analysis displayed an increase of Ni³⁺/Ni²⁺ ratio at 0.3 < x < 0.5, while Mn 2p spectra were almost identical in all samples. Rechargeable capacity values (V = 2.5–4.6 V) increased systematically with x reaching its maximum (185–190 mAh g⁻¹) at x = 0.5. Samples with superstoichiometric lithium content also demonstrated good C rate characteristics.