Abnormal Capacity Rise During Early Stage of Calendar and Cycling Aging for Li-Ion Batteries: A Review

The capacity fade or aging of Li-ion batteries (LIBs) has been extensively studied over the past few decades. It is generally observed that capacity decreases monotonically over time. However, a growing number of studies have reported an abnormal aging behavior, where capacity initially increases before declining, a clear indication of non-monotonic aging. Understanding this abnormal capacity evolution could inform strategies for extending LIB lifespan by leveraging periods of “negative” and “zero” aging. This review comprehensively summarizes and discusses proposed mechanisms from the literature that may explain this phenomenon, including the anode overhang effect, formation/dissolution of surface films, and electrode structural evolution. Finally, directions for further investigation into the abnormal capacity rise in LIBs are suggested. We hope this review will inspire new ideas for extending the lifetime of LIBs in various commercial applications, such as electric vehicles, energy storage systems, humanoid robots, electric vertical take-off and landing aircraft, etc.