Investigation of lithium plating mechanism based on N/P ratio controlled lithium-ion batteries

The detrimental lithium (Li) plating is widely recognized as a primary cause of capacity degradation and safety hazards in lithium-ion batteries (LIBs). However, inducing Li-plating under practical conditions is often unstable and poorly reproducible, making it difficult to systematically investigate the Li-plating mechanism. In this study, a controllable and reproducible Li-plating platform is established by designing LIBs with a controlled N/P ratio through adjusting the areal loading of graphite anodes, thereby enabling stable triggering of Li-plating under defined charge protocols. A Li4Ti5O12 (LTO) reference electrode is implanted to decouple the electrode voltages and directly interrogate the anode behavior associated with Li-plating. The N/P ratio controlled LIBs are evaluated under different charge rates and post-mortem analysis is conducted to further verify the associated degradation mechanism. The study examines the charge rate dependent evolution of Li-plating morphology and clarifies how the balance between reversible Li-stripping and irreversible Li accumulation shifts with current rate. It is found that a low current rate under overcharging conditions demonstrates high reversibility of Li-plating in the initial stages, but structural damage accumulates and capacity degradation becomes significant in the subsequent stages of cycling. Conversely, a high current rate under overcharging conditions leads to a rapid accumulation of “dead Li” and the simultaneous loss of active anode material from the early cycling, which accelerates the battery degradation. This study establishes a robust experimental framework for the controlled induction of Li-plating and provides valuable insights for the design of high-safety and durable LIBs.