Modeling of metal hydride battery anodes at high discharge current densities and constant discharge currents

• Modeling of the kinetic behaviors during discharge of the metal hydride anode
• The model fits the behavior of La2MgNi9 alloy at various current densities
• Diffusion coefficient of H in the solid solution in the La2MgNi9 alloy was determined
• The model allows to determine equilibrium content of H in the solid solution
• The model accounts results of the D.O.S. calculations for the La2MgNi9 alloy

In present work we have developed a theoretical model for the description of the electrochemical discharge process in the metal hydride anodes of the metal hydride batteries at various current densities. The model is based on the description of the assembly of the spherically shaped metal hydride particles where the process of electrochemical discharge is fit using a shrinking core model, with a shell of the H storage alloy growing inside the particle by decreasing volume of the internal metal hydride core. The model accounts results of the D.O.S. calculations for La2MgNi9 intermetallic alloy and has been tested for this metal hydride anode material having an electrochemical discharge capacity of 400 mAh/g and hydrogen storage capacity of 13 at.H/f.u. La2MgNi9. It allows to quantitatively describe kinetic behaviors of the electrode at various applied current densities and to estimate the diffusion coefficient for hydrogen and equilibrium content of H in the solid solution domain of hydrogen in La2MgNi9. This model has a general applicability and can be used for the optimization of the materials and the electrodes of the metal hydride rechargeable batteries at high current densities.

Modeling of discharge curves for a MH anode at various current densities.Figure optionsDownload as PowerPoint slide