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To improve the interfacial stability of lithium-ion batteries, a metal−organic framework (MOF) was designed and synthesized as an advanced additive for nickel-rich cathodes to trap the transition metal components. Use of the MOF was found to not compromise the specific capacity of the cells, and cells cycled with a nickel-rich layered oxide embedded with a metal−organic framework exhibited considerably improved cycle retention, even at high temperatures. A systematic analysis demonstrated that only negligible amounts of nickel-ion species migrated from the nickel-rich cathode to the anode surface, and the volume of nickel ions trapped inside the porous structure of the MOF could be determined by quantifying the mass change of the electrode. Finally, the surface degradation triggered by the nickel-ion dissolution was seen to be remarkably suppressed because the MOF improved the surface stability of the nickel-rich cathodes.

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Recently, layered nickel-rich cathode materials (NCM) have attracted considerable attention as advanced alternative cathode materials for use in lithium-ion batteries (LIBs). However, their inferior surface stability that gives rise to rapid fading of cycling performance is a significant drawback. This paper proposes a simple and convenient coating method that improves the surface stability of NCM using sulfate-based solvents that create artificial cathode-electrolyte interphases (CEI) on the NCM surface. SO x-based artificial CEI layer is successfully coated on the surface of the NCM through a wetcoating process that uses dimethyl sulfone (DMS) and dimethyl sulfoxide (DMSO) as liquid precursors. It is found that the SO x-based artificial CEI layer is well developed on the surface of NCM with a thickness of a few nanometers, and it does not degrade the layered structure of NCM. In cycling performance tests, cells with DMS-or DMSO-modified NCM811 cathodes exhibited improved specific capacity retention at room temperature as well as at high temperature (DMS-NCM811: 99.4%, DMSO-NCM811: 88.6%, and NCM811: 78.4%), as the SO x-based artificial CEI layer effectively suppresses undesired surface reactions such as electrolyte decomposition.