A thin inorganic composite separator for lithium-ion batteries

•An inorganic composite membrane composed of 94% Al2O3 and 6% polymer binder is prepared.•Polyethylene glycol is introduced into the casting suspension to receive a 37 µm-thick separator.•The inorganic composite membrane exhibits better rate capability.

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 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 Al2O3/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 LiNi1/3Co1/3Mn1/3O2|graphite cells, the inorganic composite separator exhibits excellent cycling stability and good rate performance.

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