Journal of The Electrochemical Society 

About: Journal of The Electrochemical Society is an academic journal published by Electrochemical Society. The journal publishes majorly in the area(s): Electrolyte & Oxide. It has an ISSN identifier of 0013-4651. Over the lifetime, 49019 publications have been published receiving 1720678 citations. The journal is also known as: JES.

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.

Polymer Electrolyte Fuel Cell Model

Abstract: We present here an isothermal, one-dimensional, steady-state model for a complete polymer electrolyte fuel cell (PEFC) with a 117 Nation | membrane. In this model we employ water diffusion coefficients electro-osmotic drag coefficients, water sorption isotherms, and membrane conductivities, all measured in our laboratory as functions of membrane water content. The model pre.dicts a net-water-per-proton flux ratio of 0.2 H20/H § under typical operating conditions, which is much less than the measured electro-osmotic drag coefficient for a fully hydrated membrane. It also predicts an increase in membrane resistance with increased current density and demonstrates the great advantage of a thinner membrane in alleviating this resistance problem. Both of these predictions were verified experimentally under certain conditions.

Electrochemical Polarization I . A Theoretical Analysis of the Shape of Polarization Curves

Abstract: At low overvoltage values, deviations from Tafel behavior for a noncorroding electrode are due primarily to the reverse reaction of the oxidation‐reduction system, and at high overvoltages to concentration and/or resistance polarization. It is shown further that the practice of placing straight lines through a few experimental points is extremely hazardous, while the indiscriminate introduction of "breaks" is contrary to the electrode kinetics described.Further complexities arising from a corroding electrode are described. In this instance, the forward and reverse reactions of both of the oxidation‐reduction systems forming the corrosion couple must be considered. This representation of the local polarization diagram of a corroding metal is more fundamental than that used previously in the literature, and thus provides a clearer picture of the various factors which affect the corrosion rate and the shape of polarization curves.A region of linear dependence of potential on applied current is described for a corroding electrode by treating it in a manner analogous to that for a noncorroding electrode. An equation is derived relating the slope of this linear region to the corrosion rate and Tafel slopes. This relation provides an important new experimental approach to the study of the electrochemistry of corroding metals since, in some instances, interfering reactions prevent determination of Tafel slopes at higher current densities.

Modeling of Galvanostatic Charge and Discharge of the Lithium/Polymer/Insertion Cell

Abstract: The galvanostatic charge and discharge of a lithium anode/solid polymer separator/insertion cathode cell is modeled using concentrated solution theory. The model is general enough to include a wide range of polymeric separator materials, lithium salts, and composite insertion cathodes. Insertion of lithium into the active cathode material is simulated using superposition, thus greatly simplifying the numerical calculations. Variable physical properties are permitted in the model. The results of a simulation of the charge/discharge behavior of the system are presented. Criteria are established to assess the importance of diffusion in the solid matrix and transport in the electrolyte. Consideration is also given to various procedures for optimization of the utilization of active cathode material.