Inorganic polyhedral oligomeric silsesquioxane with epoxy functional groups (ePOSS) is newly presented as a co-binder for the ceramic-coated separator (CCS) for safe Li-ion batteries. The ePOSS-incorporated coating layer significantly improved the dimensional stability of the CCS at 140 °C and maintained the original form even after an ignition test. Although the permeability of the CCS was slightly decreased due to the crosslinked structure of the silsesquioxane coating layer, it showed high electrochemical stability up to 5 V. Moreover, the improved liquid electrolyte wettability by ePOSS co-binder enhanced the ionic conductivity and showed 93% of cycle capacity at 0.5C rate in Li-ion batteries.

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