Investigating Li₂NiO₂–Li₂CuO₂ Solid Solutions as High-Capacity Cathode Materials\nfor Li-Ion Batteries

Abstract

Li₂Ni_1–<i>x</i>Cu_<i>x</i>O₂ solid solutions were prepared by a\nsolid-state method to study the correlation between composition and\nelectrochemical performance. Cu incorporation improved the phase purity\nof Li₂Ni_1–<i>x</i>Cu_<i>x</i>O₂ with orthorhombic <i>Immm</i> structure, resulting in enhanced capacity. However, the electrochemical\nprofiles suggested Cu incorporation did not prevent irreversible phase\ntransformation during the electrochemical process, instead, it likely\ninfluenced the phase transformation upon lithium removal. By combining\nex situ X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS),\nand differential electrochemical mass spectrometry (DEMS) measurements,\nthis study elucidates the relevant phase transformation (e.g., crystal\nstructure, local environment, and charge compensation) and participation\nof electrons from lattice oxygen during the first cycle in these complex\noxides.