Direct observation of Mn-ion dissolution from LiMn2O4 lithium battery cathode to electrolyte

The degradation of lithium-ion batteries has become a concerning issue. One problem is metal ion dissolution from the cathode material, such as Mn2+ dissolution from spinel-type LiMn2O4 (LMO). However, direct observation of the dissolution process has yet to be reported. Here, we establish in-situ 1H nuclear magnetic resonance imaging (MRI) measurement as an efficient technique to observe Mn2+ dissolution from a model lithium battery with LMO as the cathode. We observe an increase in the MRI signal intensity near the cathode, confirming the dissolution of Mn2+ from the cathode to the electrolyte. Moreover, we show that Mn2+ dissolution from LMO can be suppressed using an appropriate choice of electrolytes. We believe the method developed here can answer the long-time unanswered question of when, where, and how the metal ion dissolution occurs in the lithium-ion battery electrode and can be extended to other electrochemical systems. Metal ion dissolution from the cathode is a major issue for lithium-ion battery degradation. Here, 1H nuclear magnetic resonance imaging was demonstrated as an efficient technique to directly observe Mn2+ dissolution from a LiMn2O4 cathode of a model lithium battery.