Identification of the parameters in equivalent circuit model of lithium-ion batteries

A typical impedance spectrum of the lithium-ion cell is composed of two partially overlapped semicircles and a straight line at low frequency end. The overlapped semicircles make the parameters of the two RC circuit in equivalent circuit model of lithium-ion battery hard to be discriminated. To correctly obtain the parameters of the two RC circuit, it is necessary to find a method to distinguish Rct from Rsei. It is found that the charge transfer resistance Rct can be determined from the expression, Rct = RT/i0nF, where the exchange current density i0 is evaluated by the electrochemical model simulation, and R and T respectively denote the gas constant and the Kelvin temperature. As soon as Rct is achieved, the curve fitting of the impedance spectrum helps us to obtain the other seven parameters. © The Electrochemical Society.