Dually-functionalized Ni-rich layered oxides for high-capacity lithium-ion batteries

Layered lithium nickel-cobalt-manganese oxides(NCM)have been highlighted as advanced cathode materials for lithium-ion batteries(LIBs);however,their low interfacial stability must be overcome to ensure stable cycling performance of the cell.In this work,we propose a one-step surface modification method that uses a task-specific precursor,N,N,N,N-tetraethylsulfamide(NTESA),to improve interfacial stability of Ni-rich NCM cathode materials.The unstable surface properties of Ni-rich NCM cathode material are improved by embedding an artificial cathode-electrolyte interphase(CEI)layer on the cathode surface by heat treatment of the Ni-rich NCM cathode material with an NTESA precursor at low temperature.Our material analyses indicate that this approach allows the formation of amine-and sulfone-functionalized CEI layers on the surface of Ni-rich NCM cathode material without changing the layered structure of the cathode material.NTESA-functionalized Ni-rich NCM cathode materials exhibit improved cycling retention after 100 cycles:for example,a cell cycled with a 3.0 NTESA-modified NCM811 cathode presents the highest retention ratio of 88.3%,whereas a cell cycled with a non-functionalized NCM811 cathode suffers from rapid fading of the cycling performance(68.4%).Our additional SEM,XPS,and EIS analyses indicate that electrolyte decomposition is suppressed during electrochemical cycling,thereby leading to smaller increases in the internal resistances.ICP-MS analyses of the cycled anodes also indicate that the NTESA-based artificial CEI layer inhibits the dissolution of transition metal components from the Ni-rich NCM cathode materials,thereby contributing to an improved overall electrochemical performance of the cell.