Preparation of hydrophilic polyethylene/methylcellulose blend microporous membranes for separator of lithium-ion batteries

Abstract

Hydrophilic high density polyethylene/methylcellulose (HDPE/MC) blend microporous membranes were prepared via the thermally induced phase separation process. The effect of MC on the HDPE membranes was investigated by examining the morphology and determining the phase diagram, hydrophilicity, crystallinity, and mechanical properties. In addition, the electrochemical properties were evaluated from button cells consisting of the pure HDPE membrane and HDPE/MC blended microporous membranes as separators saturated by the LiPF6 electrolyte. The obtained results indicated that the cloud point temperature and the surface morphology of the membranes was shifted to high values and changed from dense to porous, respectively, with increasing MC content. The blended membranes also had a higher electrical uptake than the pure HDPE membrane. Moreover, the maximum ionic conductivity (1.01×10−3S/cm) and minimum activation energy (Ea) value (10.48kJ/mol) were obtained at an MC content of 2wt%. Furthermore, compared to those consisting of the pure HDPE membrane, button cells consisting of the HDPE/MC blend microporous membranes exhibited higher charge-discharge capacity and better discharge performance at various current densities.