The dependence of the open-circuit potential on the state of charge in lithium insertion electrodes is usually measured at equilibrium conditions. For the modeling of lithium–silicon electrodes at room temperature, the use of a pseudo-thermodynamic potential vs composition curve based on metastable amorphous phase transitions with path dependence is proposed. Volume changes during lithium insertion/deinsertion in a single silicon electrode particle under potentiodynamic control are modeled and compared with experiments to provide justification for the same. Only if asymmetric transfer coefficients and sluggish kinetics are experimentally observed can kinetic hysteresis be reasoned for the potential gap in Li–Si system. The particle model enables one to analyze the influence of diffusion in the solid phase, particle size, and kinetic parameters without interference from other components in a practical porous electrode. Concentration profiles within the electrode particle under galvanostatic control are investigated. Sluggish kinetics is established from cyclic voltammograms at different scan rates. This work stresses the need for accurate experimental determination of kinetic parameters (and thus the exchange current density) in silicon nanoparticles. This model and knowledge thereof can be used in the cell-sandwich model for the design of lithium-ion cells with composite silicon negative electrodes.

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The galvanostatic charge and discharge of a silicon composite electrode/separator/lithium foil cell is modeled using porous elec-trode theory and concentrated solution theory. The one-dimensional (flow) model is solved with COMSOL 3.5a software. Porosity changes that accompany the large molar volume changes in the lithium-silicon electrode during operation are included and ana-lyzed. The concept of reservoir is introduced for lithium-ion cells to accommodate the displaced electrolyte (i.e. the liquid phase). Simulation results quantitatively show the importance of a high initial porosity in silicon electrodes for better utilization of active material, especially at low rates. At higher rates, the utilization becomes similar for both thicker, porous electrodes and thinner, less porous electrodes. The insensitivity to porosity and thickness at high rates is attributed to the slow electrode kinetics for the Li-Si system. Therefore, the application dictates the optimum thickness and porosity of the electrode. Moreover, the importance and need for faster electrode kinetics relative to transport limitations is quantitatively shown. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3589301] All rights reserved. Manuscript submitted December 13, 2010; revised manuscript received April 15, 2011. Published June 1, 2011. Recent interest in rechargeable batteries for electric vehicles, hybrid electric vehicles and plug-in hybrid electric vehicles has led to the investigation of silicon as a negative insertion material due to its high specific capacity (4200 mAh/g (corresponding to Li22Si5

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