Pore-controlled polymer membrane with Mn (II) ion trapping effect for high-rate performance LiMn2O4 cathode

Abstract

Since Li+ ions can transport through porous channels in the separator containing liquid electrolyte, the electrochemical and structural properties of the separator needs to be improved to develop a high rate performance lithium-ion battery (LIB). In this study, a gel-type polymer membrane using poly (vinylidene fluoride-co-hexafluoropropylene) (P (VDF-HFP)) acting as a matrix and ethylene carbonate (EC) as a separator was applied for a high-performance LIB with LiMn2O4 as a cathode. The cell assembled with the porous polymer gel electrolyte membrane prepared using P (VDF-HFP) with an appropriate amount of EC exhibited an improved capacity (78.8 mAh g−1) and energy density (308.4 mWh g−1) at a current density of 720 mA g−1, and a high capacity retention (94.8%) at a current density of 240 mA g−1, compared to the cell assembled with polyethylene as a separator. The enhanced LIB performance can result from an increased Li+-ion migration between the chains in low-crystalline polymer membranes and an increased volume of the liquid electrolyte for ionic motion in the porous membrane due to an increased porosity.