Computer simulation of negative electrode operation in lithium—ion battery: Galvanostatic discharg active intercalating agent grains, role of diffusion limitations

Abstract

Computer simulation of the negative electrode (anode) operation in a lithium-ion battery under galvanostatic discharge mode is performed. The amount of active intercalating agent grains that may take part in the electrochemical process is calculated. Special attention was paid to evaluation of diffusion limitations arising under recovery of lithium atoms from an intercalating agent grains related to the low value of the diffusion coefficient of lithium atoms D. It is shown that the common model of a spherical intercalating agent grain, when its whole outer surface participates in an electrochemical process, contradicts the model of equally-sized cubic grains studied in this work. It is found that the average amount of electrochemically active faces of active intercalating agent grains varies in the range of 1.91 to 3.55. A new model of the structure and depletion of an intercalating agent grain is suggested. The process of full depletion of intercalating agent grains may be implemented in the case when they either have rather small dimensions L, more specifically, if the L/D ratio is low, or if the anode discharge current density I is sufficiently low. The optimum working anode parameters are calculated under the condition of reaching full depletion of intercalating agent grains: active layer depth, discharge time, specific electric capacitance and final anode potential at the active layer/inter-electrode space interface.