Understanding Dissolution As a Mode of Capacity Fade in Lithium-Ion Batteries

LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) positive electrode material is commonly used in lithium ion batteries because of its favorable characteristics including high reversible capacity, power capability, and thermal stability. However, dissolution of transition metals from the positive electrodes is a concern in lithium ion batteries containing NCM positive electrode as it has been implicated in a rise in impedance and capacity fade of cells. In a lithium ion cell, there are many competing effects that contribute to the growth of the solid electrolyte interphase (SEI) and capacity fade. In this work, the effects of metal dissolution on full cells employing NCM positive electrode and graphite negative electrode was studied by accelerating the degradation due to dissolution process. The effects of metal dissolution on cell capacity, cyclic stability, and impedance were investigated by using electrochemical techniques. Postmortem analyses were carried out on electrodes to study the morphological changes due to the transition metal.