port conditions on the reaction surface and helped smooth the deposit at the expense of the current efficiency. As the hydrogen evolution reaction dominates over 90% of the process, the alloy deposit loses its integrity. Note in Fig. 14g for the Cu-5 bath at -1.6V, segregated areas of copperrich and nickel-rich can be seen as well as numerous cracks caused by hydrogen embrittlement. ConclusionsCodeposition of copper-nickel alloys occurs in a fairly narrow potential region, namely, between -1.0 to -1.2V vs. SCE. In this region, a wide variety of alloy composition (0-50% nickel) and fairly smooth deposits can be obtained. Because copper deposition is near mass transport limited in the codeposition region, it is important that the plating bath is well-agitated. The composition of the alloy deposit can be controlled by the molar metal ion ratio in solution as well as the electrode potential. If greater operational control is needed, alternative plating schemes such as pulse plating can be utilized. Preliminary pulse-potential deposition of this alloy produced some improved surface morphology as well as greater compositional control. Also, for greater applicability, it is useful to model the alloy dep~ osition process as discussed in part II of this paper (18).

Steady-state polarization measurements on stationary and rotating disk electrodes were performed in Cu-Ni-citrate plating baths as well as in single metal ion-citrate solutions. The polarization curves were used to identify the different electrode reactions occurring during the plating process. Five electrochemical reactions were found dominant in different potential regions. They were the reduction of hydrogen ion from the dissociation of hydrogenated citrate ion, oxygen reduction, copper deposition, nickel deposition, and reduction of water. C odeposition of Cu-Ni alloy occurred in a fairly narrow electrode potential region (-1.0 to -1.2V vs. SCE), where the effects of the side reactions were relatively small. A Levich analysis of the rotating disk data was used to determine the overall kinetic and mass transport parameters of the Cu-Ni alloy electrodeposition process. Finally, compositional and morphological analyses of the alloy plated at constant potentials were also performed.

Model predictions of half-cell voltages, current, and gassing behavior are compared to experimental results of valve-regulated lead-acid ͑VRLA͒ cells to elucidate the charge mechanisms. Good comparisons of experimental Pb half-cell voltages with model predictions confirm the importance of liquid-phase Pb 2ϩ transport early during charge. In the latter stages of Pb-electrode charge, limitations in the PbSO 4 dissolution rate are more important than those of Pb 2ϩ transport and control charge behavior. Model predictions with an analogous mechanism for the PbO 2 electrode ͑i.e., involving dissolution and Pb 2ϩ transport͒ were not consistent with the charge polarization behavior, since comparisons of experimental half-cell voltages with model results were poor. Satisfactory comparisons with a model that incorporates a solid-state PbO 2 charge mechanism confirmed the insignificance of dissolution and transport in PbO 2 charging. The good agreement between model and experimental current behavior during the constant-voltage portion of charge support our conclusions regarding the electrode charging mechanisms. Conditions under which to expect charging difficulties as well as improved charge regimes are also discussed. The model also predicted the characteristic double-peak gas-flow behavior seen when charging VRLA cells with constant current to a specific voltage lid. The first peak is due to the onset of significant amounts of O 2 generation even though the internal residual gas is dominantly H 2 . The second peak is due to the onset of H 2 evolution.

We provide an analysis of batteries subject to controlled power operation on both charge and discharge over the temperature range of −30 to 45°C, consistent with vehicle drive events. The method we develop is applied to a high-power lithium ion cell, thereby allowing us to obtain parameters and overall characteristics useful for ͑i͒ representing the battery in vehicle models and ͑ii͒ providing a quantitative means of comparing and classifying battery systems. The current and voltage histories are modeled during the constant power discharge, and Ragone plots ͑energy vs power͒ as well as discharge and charge times are analyzed. The equations employed are based on an equivalent circuit comprising a parallel resistor-capacitor combination in series with a resistor and the open-circuit potential source. The circuit element values are dependent on temperature and independent of the current and potential. Model calculations are compared with experimental data. Good agreement is obtained for temperatures ranging from 0 to 45°C. More work is needed to clarify phenomena below 0°C.