Modeling lithium plating onset on porous graphite elec- trodes under fast charging with hierarchical multiphase porous electrode theory

Lithium plating during fast charging of porous graphite electrodes in lithium-ion batteries accelerates degradation and raises safety concerns. Predicting lithium plating is challenging due to the close redox potentials of lithium reduction and intercalation, obscured by the dynamic resistance originated from the interplay of multiphase behavior and hierarchical pore structures. To resolve dynamic resistance of realistic porous graphite electrodes, we introduce a model of porous secondary graphite particle to the multiphse porous electrode theory(MPET) using nonequilibrium thermodynamics and method of volume averaging. Our hierarchical multiphase porous electrode theory is examined against experiments with varying fast charging conditions and capacities. With all parameters estimated from independent sources, our model quantitatively agrees with measured cell voltages , and, more importantly, experimentally determined plating onset from 2C to 6C. Spatial and temporal lithiation dynamics in porous graphite electrodes are unveiled theoretically, reproducing key features including idle graphite particles observed experimentally.