A thin inorganic composite separator for lithium-ion batteries

A thin inorganic composite membrane composed of 94   wt% Al 2 O 3 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   µm-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 Al 2 O 3 /SBR separator shows a superior thermal stability under 130   °C with no any shrinkage, higher electrolyte uptake/retention and ionic conductivity than the common polyethylene (PE) separator. In LiNi 1/3 Co 1/3 Mn 1/3 O 2 |graphite cells, the inorganic composite separator exhibits excellent cycling stability and good rate performance.