Surface Changes of LiNixMnyCo1-x-yO2 in Li-Ion Batteries Using In Situ Surface-Enhanced Raman Spectroscopy

2020 
Understanding and controlling parasitic reactions at the electrode-electrolyte interface (EEI) in Li-ion batteries is essential to enhance and predict battery cycle life. Recent work has shown that increasing Ni in the positive electrode materials can promote the dehydrogenation of carbonate-based electrolytes and electrode impedance growth. Unfortunately, probing the interfacial reactions between positive electrode and organic electrolyte are intrinsically difficult using in situ techniques. In this work, we used in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to examine the changes in the interface between lithium nickel manganese cobalt oxide like LiNi0.8Mn0.1Co0.1O2 (NMC811) or LiNi1/3Mn1/3Co1/3O2 (NMC111) and a carbonate-based electrolyte with 1 M LiPF6. The surface of charged NMC811 was changed to spinel and rock-salt structure at 4.6 VLi. In addition, the formation and growth of surface lithium fluoride appeared at 3.8 VLi and higher, which could be attributed to the hydro...
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