Degradation Mechanisms of LiNi0.5Mn0.3Co0.2O2/graphite Battery in Real-Life Driving Scenarios

Abstract

Understanding the aging mechanisms of lithium-ion batteries (LIBs) in real-life driving scenarios is the key to advancing battery design and management for electric vehicles. This work studies in detail the aging modes of commercial LIBs under real-life driving scenarios with a standardized World Harmonized Light Vehicle Test Cycle (WLTC) discharging procedure. Combined results from electrochemical analyses, post-mortem, and operando characterization show that a large depth of DOD (100%) leads to significant structural changes, especially Ni-O bond length and coordination number, of NMC532 cathode materials and hence rapid degradation related to active material loss, while a low DOD level (45%) results in intensified interfacial degradation, both leading to a limited battery cycle life (<900 and <1600 equivalent full cycles (EFCs), respectively, under 45% and 100% DoDs). In contrast, a medium DOD (75%) results in balanced electrode and interface degradations and significantly enhanced cycling stability (>2200 EFCs under 75% DoDs). Besides, we also emphasized that in real-life driving, the loss of active materials primarily originates from the cathode. These findings reveal that balancing the electrode and interfacial degradations are crucial for extending battery lifetime in practical applications. This work provides mechanistic insights into the degradation of LIBs under real-life operating conditions, guiding the rational design and optimization of cycling protocols in battery management systems (BMSs) for advanced battery development.