Effect of surface modification using a sulfate-based surfactant on the electrochemical performance of Ni-rich cathode materials

Abstract

Ni-rich layered oxides (Ni-rich NCM) have received much attention owing to their high specific capacity, but poor cycling performance attributed to their inferior surface properties is still considered to be a bottleneck preventing the expansion of the wider adoption of these materials in lithium-ion batteries (LIBs). In this work, we propose one-step efficient surface modification process which utilizes an organic surfactant (SDS) with a sulfate functional group in order to improve the surface stability of Ni-rich NCM materials. The surface modification provides a sulfate-embedded cathode-electrolyte interphase (CEI) layer on the Ni-rich NCM surface, which includes a SOx functional group. All of cells employing SDS-treated NCM cathode exhibit higher specific capacity retention after 100 cycles. Among these, the cell cycled with the 0.5% SDS-treated Ni-rich NCM cathode exhibited specific capacity retention of 91.9%, which is a remarkable increase compared with the cell cycled with bare NCM811 (69.6%). Additional analyses of the cycled electrodes indicated that the better cycling performance of the SDS-treated NCM811 cathode is attributable to the stabilization of the NCM811 surface; less electrolyte decomposition was observed in a cycled SDS-treated NCM811 cathode when analyzed by SEM, EIS, and XPS.