Overlooked Electrolyte Destabilization by Manganese (II) in Lithium-ion Batteries

Transition-metal dissolution from cathode materials, manganese in particular, has been held responsible for severe capacity fading in lithium-ion batteries, with the deposition of the transition-metal cations on anode surface, in elemental form or as chelated-complexes, as the main contributor for such degradations. In this work we demonstrate with diverse experiments and calculations that, besides interfacial manganese species on anode, manganese(II) in bulk electrolyte also significantly destabilizes electrolyte components with its unique solvation-sheath structure, where the decompositions of carbonate molecules and hexafluorophosphate anion are catalyzed via their interactions with manganese(II). The manganese(II)-species eventually deposited on anode surface resists reduction to its elemental form because of its lower electrophilicity than carbonate molecule or anion, whose destabilization leads to sustained consumption. The reveal understanding of the once-overlooked role of manganese-dissolution in electrolytes provides fresh insight into the failure mechanism of manganese-based cathode chemistries, which serves as better guideline to electrolyte design for future batteries.