Separator impregnated with polyvinyl alcohol to simultaneously improve electrochemical performances and compression resistance

Abstract

Growing desire for high-performance improves lithium-ion batteries. But separator exhibits poor electrolyte compatibility owing to intrinsic hydrophobicity feature and weak compression resistance caused by inferior microporous structure, which raises lithium-ion migration obstacle. In this article, polyethylene/poly (vinyl alcohol) (PE/PVA) composite separators are prepared by a simple dipping process to reinforce electrochemical properties and compression resistance synchronously. Electrochemical performances of assembled batteries reveal that PE separators dipped with PVA possess superior electrolyte affinity due to abundant hydroxyl of PVA. The more stable formation of solid electrolyte interface layer film and higher Li+ transference number suppress electrode polarization and decrease cell resistances, which further optimizes cycle stability and C-rate performance of cells. Also, compression tests expose that PVA invaded in separator builds effective supporting structure between the multi-layer construction, significantly improving compression resistance of separators. Especially, the PE/PVA separator simultaneously exhibits excellent electrochemical performance and compression resistance as PVA content ascends to 2%, which possesses the highest Li+ transference number of 0.527 and discharge capacity retention of 93.1% after 100 cycles. This study proposes some new viewpoints into the functions of separators within the battery and provides a facile scheme for fabricating high-performance separators.