Ultra-high molecular weight polyethylene (UHMWPE) is a promising material for preparation of membranes and Li-ion battery separators. Existing methods of their preparation are either hardly scalable or demand rather complex equipment. In this work UHMWPE separators were prepared via thermally induced phase separation method (TIPS) without additional drawing from the blends of the polymer with decalin and its mixtures with dioctyl adipate (DOA). It was shown that the final membrane morphology is a result of significant shrinkage of the initially formed structure upon drying form the extractant. In this case, shrinkage was favorable since it enables formation of the samples with intermediate porosity (63–86 %) from a very dilute solution of UHMWPE (1.5 % wt.). The shrinkage behavior was examined using optical microscopy. Mechanical and transport properties were evaluated using standard methods whereas electrochemical performance of the prepared samples was investigated by assembling the disc-like batteries and their exploitation at different C-rates. It was shown that the TIPS method can be successfully used to prepare porous flat films with a thickness as low as 30 μm are applicable as Li-ion battery separators. The structure of the prepared membranes consists of three-dimensional, irregularly shaped leaf-like particles that are mechanically interlocked (entangled) rather than chemically bonded. An increase in the DOA content in the mixed solvent (from 0 to 30 % wt.) was detected to increase the crystallinity (from 74 to 91 %), melting point (from 132.8 to 134.2 °C), tensile strength (from 0.8 to 4.0 MPa), elongation at break (from 420 to 660 %) and puncture strength (from 0.27 to 1.83 gf μm−1) and decrease the thickness (from 72 to 30 μm), mean through pore size (from 0.6 to 0.33 μm) and permeance (from 2050 to 280 L m–2h−1 bar−1).
