Dually modified cathode-electrolyte interphases layers by calcium phosphate on the surface of nickel-rich layered oxide cathode for lithium-ion batteries

Improvement of the interfacial stability of layered nickel-rich cathode materials by surface modification is investigated using calcium phosphate as a coating precursor. The surface modification procedure allows the formation of artificially induced cathode-electrolyte interphases with residual lithium species remaining on the surface of nickel-rich cathode materials. Surface modification increases the particle hardness of the cathode materials by increasing their mechanical properties through strong binding of calcium ions with oxygen elements. In addition, artificially induced cathode-electrolyte interphases prevent electrolyte decomposition on the surface of the nickel-rich cathode materials, thereby affording improved the cycling retention at high temperatures. The cell cycled with surface-modified nickel-rich cathode materials exhibits a cycling retention of 72.5%, whereas the cell cycled with unmodified nickel-rich cathode materials shows rapid fading of cycling retention (39.9%) at high temperature. Additional systematic analyses, performed by scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectrometry, indicate that the undesired surface reactions are effectively inhibited on the modified cathode during electrochemical charging/discharging processes in the cell, resulting in improved electrochemical performances, such as cycling retention and rate capabilities.