Electrochemical Society

About: Electrochemical Society is a nonprofit organization based out in Pennington, New Jersey, United States. It is known for research contribution in the topics: Thin film & Oxide. The organization has 162 authors who have published 142 publications receiving 10655 citations. The organization is also known as: ECS & American Electrochemical Society.

Phospho‐olivines as Positive‐Electrode Materials for Rechargeable Lithium Batteries

Abstract: Reversible extraction of lithium from LiFePO 4 (triphylite) and insertion of lithium into FePO 4 at 3.5 V vs. lithium at 0.05 mA/cm 2 shows this material to be an excellent candidate for the cathode of a low-power, rechargeable lithium battery that is inexpensive, nontoxic, and environmentally benign. Electrochemical extraction was limited to ∼0.6 Li/formula unit; but even with this restriction the specific capacity is 100 to 110 mAh/g. Complete extraction of lithium was performed chemically; it gave a new phase, FePO 4 , isostructural with heterosite, Fe 0.65 Mn 0.35 PO 4 . The FePO 4 framework of the ordered olivine LiFePO 4 is retained with minor displacive adjustments. Nevertheless the insertion/extraction reaction proceeds via a two-phase process, and a reversible loss in capacity with increasing current density appears to be associated with a diffusion-limited transfer of lithium across the two-phase interface. Electrochemical extraction of lithium from isostructural LiMPO 4 (M = Mn, Co, or Ni) with an LiClO 4 electrolyte was not possible; but successful extraction of lithium from LiFe 1-x Mn x PO 4 was accomplished with maximum oxidation of the Mn 3+ /Mn 2+ occurring at x = 0.5. The Fe 3+ /Fe 2+ couple was oxidized first at 3.5 V followed by oxidation of the Mn 3+ /Mn 2+ couple at 4.1 V vs. lithium. The Fe 3+ -O-Mn 2+ interactions appear to destabilize the Mn 2+ level and stabilize the Fe 2+ level so as to make the Mn 3+ /Mn 2+ energy accessible.

Micro-macroscopic coupled modeling of batteries and fuel cells: I. Model development

Abstract: A micro-macroscopic coupled model, aimed at incorporating solid-state physics of electrode materials and interface morphology and chemistry, has been developed for advanced batteries and fuel cells. Electrochemical cells considered consist of three phases: a solid matrix (electrode material or separator), an electrolyte (liquid or solid), and a gas phase. Macroscopic conservation equations are derived separately for each phase using the volume averaging technique and are shown to contain interfacial terms which allow for the incorporation of microscopic physical phenomena such as solid-state diffusion and ohmic drop, as well as interfacial phenomena such as phase transformation, precipitation, and passivation. Constitutive relations for these interfacial terms are developed and linked to the macroscopic conservation equations for species and charge transfer. A number of nonequilibrium effects encountered in high-energy-density and high-power-density power sources are assessed. Finally, conditions for interfacial chemical and electrical equilibrium are explored and their practical implications are discussed. Simplifications of the present model to previous macrohomogeneous models are examined. In a companion paper, illustrative calculations for nickel-cadmium and nickel-metal hydride batteries are carried out. The micro-macroscopic model can be used to explore material and interfacial properties for desired cell performance.

Differential Scanning Calorimetry Study of the Reactivity of Carbon Anodes in Plastic Li‐Ion Batteries

Abstract: Chemical reactions taking place at elevated temperatures in a polymer-bonded lithiated carbon anode were studied by differential scanning calorimetry. The influences of parameters such as degree of intercalation, number of cycles, specific surface area, and chemical nature of the binder were elucidated. It was clearly established that the first reaction taking place at ca. 120-140 °C was the transformation of the passivation layer products into lithium carbonate, and that lithiated carbon reacted with the molten binder via dehydrofluorination only at T > 300 °C. Both reactions strongly depend on the specific surface area of the electrodes and the degree of lithiation.

Characterization of Sr‐Doped LaMnO3 and LaCoO3 as Cathode Materials for a Doped LaGaO3 Ceramic Fuel Cell

Abstract: Energy dispersive spectrometry line scan and ac impedance spectroscopy were used in this study to investigate the chemical reactions between two cathode materials, La{sub 0.84}Sr{sub 0.16} MnO{sub 3} (LSM), La{sub 0.5}Sr{sub 0.5}CoO{sub 3{minus}{delta}} (LSC), and the electrolyte La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 2.85} (LSGM). Significant interdiffusions of Co into LSGM and Ga into LSC were found at an LSC/LSGM interface even at relatively low fabrication temperatures. In contrast, only small interdiffusion of Mn into LSGM and Ga into LSM were detected at the LSM/LSGM interface even though it was fired at 1,470 C. The ac impedance spectra of the electrolyte LSGM with LSM, LSC, and Pt electrodes indicate a grain-boundary contribution to the total conductivity in the intermediate frequency range and a diffusion-controlled impedance in the low-frequency range. Irrespective of chemical reactions and a larger thermal expansion coefficient, LSC has the lowest dc resistance of all three electrodes investigated. Considering both the small interdiffusion reactions between LSM and LSGM and their similar thermal expansion coefficients, LSM could be an appropriate cathode material for LSGM-based fuel cells.

Micro‐Macroscopic Coupled Modeling of Batteries and Fuel Cells II. Application to Nickel‐Cadmium and Nickel‐Metal Hydride Cells

Abstract: The micro-macroscopic coupled model developed in a companion paper is applied to predict the discharge and charge behaviors of nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) cells. The model integrates important microscopic phenomena such as proton or hydrogen diffusion and conduction of electrons in active materials into the macroscopic calculations of species and charge transfer. Simulation results for a full Ni-Cd cell and single MH electrode are presented and validated against the pseudo two-dimensional numerical model in the literature. In good agreement with the previous results, the present family of models is computationally more efficient and is particularly suitable for simulations of complex test conditions, such as the dynamic stress test and pulse charging for electric vehicles. In addition, a mathematical model for full Ni-MH cells is presented and sample simulations are performed for discharge and recharge with oxygen generation and recombination taken into account. These gas reactions represent an important mechanism for battery overcharge in the electric vehicle application.