Lithium‐plating‐free fast charging of large‐format lithium‐ion batteries with reference electrodes

Abstract

Fast charging without lithium deposition has been one of the most important goals for commercial lithium-ion batteries. This study developed a fast charging strategy for a commercial large-format NCM/graphite lithium-ion battery with a nominal capacity of 120 Ah. Reliable reference electrodes, whose performances were thoroughly investigated with high fidelity, were implanted into the cells to provide anode potential signals during the charging process. The charging current was strictly modulated to maintain both the anode potential and temperature within the safety regions. The cell's full charging capability was exploited and twice the charging speed was realized using the proposed strategy compared with the manufacturer's fast charging strategy. Following the cycle life tests, an incremental capacity analysis and scanning electron microscopy tests were conducted to identify the degradation mechanism under fast charging. The results indicated that after the fast charging, the battery's decay rate was similar to that of a battery subjected to slow charging after 100 cycles, while no plated lithium was detected on the negative electrode. An electric vehicle (EV) could be driven 300 km after charging for 16 minutes without lithium deposition. It can be concluded that the proposed lithium-plating-free fast charging strategy has high battery applicability and manufacturer friendliness, and provides a new perspective on EV fast charging. Highlights A method for developing a fast charging strategy for large-capacity lithium batteries is proposed. The cell's full charging capability was exploited and twice the charging speed was realized using the proposed strategy compared with the manufacturer's fast charging strategy. The battery's decay rate was similar to that of a battery subjected to slow charging after 100 cycles, while no plated lithium was detected on the negative electrode.