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Structural Evolution and High-Voltage Structural Stability of Li(NixMnyCoz)O2 Electrodes

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posted on 2018-12-17, 00:00 authored by Damian Goonetilleke, Neeraj Sharma, Wei Kong Pang, Vanessa K. Peterson, Remi Petibon, Jing Li, J. R. Dahn
Positive electrode materials remain a limiting factor for the energy density of lithium-ion batteries (LIBs). Improving the structural stability of these materials over a wider potential window presents an opportune path to higher energy density LIBs. Herein, operando neutron diffraction is used to elucidate the relationship between the structural evolution and electrochemical behavior for a series of Li-ion pouch cells containing Li­(NixMnyCoz)­O2 (x + y + z = 1) electrode chemistries. The structural stability of these electrodes during charge and discharge cycling across a wide potential window is found to be influenced by the ratio of transition-metal atoms in the material. Of the electrodes investigated in this study, the Li­(Ni0.4Mn0.4Co0.2)­O2 composition exhibits the smallest magnitude of structural expansion and contraction during cycling while also providing favorable structural stability at high voltage. Greater structural change was observed in electrodes with a higher Ni content, while decreasing inversely to the Ni and Co content in the positive electrode. The combination of structural and electrochemical characterization of a wide range of NMC compositions provides useful insight for the design and application of ideal electrode compositions for long-term cycling and structural stability during storage at the charged state.

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