A rapid classification method of the retired LiCoxNiyMn1-x-yO2 batteries for electric vehicles

With the aging of Lithium-ion batteries (LIBs) of electric vehicles in the near future, research on the second use of retired LIBs is becoming more and more critical. The classification method of the retired LIBs is challenging before the second use due to large cell variations. This paper proposes a rapid classification method based on battery capacity and internal resistance, because batteries with different capacities and internal resistances have different voltage curves during charge/discharge. First, the piecewise linear fitting method established by the specified tested batteries with capacities and their corresponding characteristic voltages is used to sort the batteries. Then combined with the nonlinear function approximation ability of the radial basis function neural network (RBFNN) model, battery capacity and internal resistance are predicted after the model training. 108 cells are used for the simulation classification with experimental classification performed on 12 cells. The results prove that the classification method is accurate.