Syringeless electrospun non-woven separator membrane for high-energy and high-power Li-ion battery application

Abstract

Developing separators to meet the various requirements of next-generation Li-ion batteries (LIBs) is quite challenging because safety issues (good mechanical and thermal properties) and high power and energy density (small thickness and large porosity) exhibit a negative correlation, resulting in a technical contradiction. In general, an electrospun nonwoven membrane is a potential candidate for use in next-generation LIBs, but sufficiently thin electrospun-based nonwoven webs cannot be used as separators owing to their poor mechanical properties and exceedingly large porosity, which fail to prevent dendrite growth. To overcome these shortcomings, we fabricated a composite nonwoven separator using polyvinylidene fluoride (PVDF) and lithium lanthanum zirconium oxide (Li6.4La3Zr2Al0.2O12, LLZO) particles via a syringeless colloidal electrospinning method. To demonstrate the feasibility of our separator membrane for use in high-power and high-energy LIBs, we evaluated the electrochemical performance of an assembled LiNi0.6Co0.2Mn0.2O2 (NCM622)/graphite cell at a high C-rate. The assembled cell containing our separator membrane delivered an outstanding capacity of 115 mAh∙g-1 with a capacity retention of 97% after 100 cycles, even at 3 C. In addition, a Li-metal cell with our PVDF/LLZO separator achieved capacity retention of 86% after 250 cycles at 0.5 C.