Editors' Choice—Capacity Fading Mechanisms of NCM-811 Cathodes in Lithium-Ion Batteries Studied by X-ray Diffraction and Other Diagnostics

By F. Friedrich, Benjamin Strehle, A. Freiberg, Karin Kleiner, S. Day, C. Erk, M. Piana, H. Gasteiger. Journal of the Electrochemical Society, 2019

162 citations recorded by the source corpus.

Ni-rich layered oxides, like NCM-811, are promising lithium-ion battery cathode materials for applications such as electric vehicles. However,pronouncedcapacityfading,especiallyathighvoltages,stillleadtoalimitedcyclelife,wherebytheunderlyingdegradationmechanisms,e.g.whethertheyaredetrimentalreactionsinthebulkoratthesurface,arestillcontroversiallydiscussed.Here,weinvestigatethecapacityfadingofNCM-811/graphitefull-cellsover1000cyclesbyacombinationofinsitusynchrotronX-raypowderdiffraction,impedancespectroscopy,andX-rayphotoelectronspectroscopy.InordertofocusontheNCM-811material,weexcludedLilossattheanodebypre-lithiatingthegraphite.WewereabletofindaquantitativecorrelationbetweenNCM-811latticeparametersandcapacityfading.Ourresultsprovethattherearenoconsiderablechangesinthebulkstructure,whichcouldberesponsiblefortheobserved the formation of a resistive surface layer, which is responsible for (i) an irreversible loss of capacity due to the material lost for its formation, and (ii) for a considerable impedance growth. Further evidence is provided that the surface layer is gradually formed around the primary NCM-811 particles.

Subfields: Electrical and Electronic Engineering, Mechanical Engineering, Surfaces, Coatings and Films

View Paper: https://www.semanticscholar.org/paper/20082687a468cbe6b319207fabe2e5ff044a3831