A thin inorganic composite membrane composed of 94 wt% Al2O3 and 6 wt% styrene-butadiene rubber (SBR) polymer binder is prepared via an aqueous solution casting process. 1 wt% polyethylene glycol (PEG) is introduced into the casting suspension for the preparation of a 37 mu m-thick inorganic composite separator. PEG plays a key role to enhance the stability of the casting suspension to separate the thin membrane from the substrate, and to increase the porosity of the membrane. The as-prepared Al2O3/SBR separator shows a superior thermal stability under 130 degrees C with no any shrinkage, higher electrolyte uptake/retention and ionic conductivity than the common polyethylene (PE) separator. In LiNi1/3Co1/ (3)Mn(1/3)O(2 vertical bar)graphite cells, the inorganic composite separator exhibits excellent cycling stability and good rate performance. (C) 2016 Elsevier B.V. All rights reserved.