US Patent 7919966 Method of estimating surface ion density

The present teachings are directed toward machine implemented method for estimating the ion density of the surface of either positive or negative electrode of a battery. The machine-implemented method includes dividing each electrode into N layers of active electrode material, determining the ion density variable for each one of the N layers of the active electrode, and determining the ion density of the electrode surface. In the presently disclosed method, the ion density variable of each of the N layers of the active electrode changes as a function of the difference between the respective ion density variables of adjacent N layers, and the ion density of the electrode surface changes as a function of the battery current and the difference between the respective ion density variables of adjacent N layers. The present method is particularly applicable to Li-ion batteries.