Optimization of electrophoretic suspension to fabricate Li[Ni1/3Co1/3Mn1/3]O2 based positive electrode for Li-ion batteries

Abstract

A direct deposition technique based on electrophoresis is employed to prepare positive electrode for Li-ion batteries. Li[Ni1/3Co1/3Mn1/3]O2 (active material), denka black (conductive agent) and PVDF (binder) is dispersed in the solvent and used as a suspension for electrophoretic deposition (EPD) process. The Box-Bhenken design is made to optimize the EPD suspension, by varying three controllable input factors namely weight of active material, conductive agent and binder. The output responses are initial discharge capacity and capacity retention ratio. There is a good agreement between the actual and predicted values. The adequacies of the models are established with analysis of variance. The response surface methodology with desirability function is used to determine the optimum deposition condition to obtain maximum initial discharge capacity and capacity retention ratio for the EPD prepared positive electrode. The developed design predicts the 500mg of active material, 10mg of conductive agent and 30mg of binder as an optimum condition for maximum discharge capacity of 152mAh/g and capacity retention ratio of 93%. For confirmation, the electrode prepared with these optimum parameters gives discharge capacity of 147.18mAh/g and capacity retention ratio of 97.11%. EPD process is suggested to be efficient for fabrication of positive electrode under the predicted optimal condition in accordance to the positive electrode prepared by Doctor blade method.