Ultra-thin, non-combustible PEO polymer solid electrolyte for high safety polymer lithium metal batteries

Abstract

The safety problems of lithium-ion batteries (LIBs) have aroused great concern on account of their extensive use. It is believed that the replacement of flammable liquid electrolytes with solid electrolytes (SSE) will solve this problem and provide an unmatched energy density for lithium-based batteries. Here, Lithium hexafluorophosphate (LiPF6) and ionic liquid serve as flame retardants for Poly (ethylene oxide) (PEO) solid electrolytes with Polyamide 6 (PA6) membrane as the skeleton. PA membrane can not only decrease the crystallinity of PEO to facilitate lithium-ion migration, but also inhibit the growth of lithium dendrites, which is attributed to its lithium-philic properties, adequate mechanical properties and flexibility. In addition, the increase of ionic liquid, on the one hand, can provide hexafluorophosphoric acid ions, which endow the SSE with excellent flame-retardant performance. The electrolyte exhibits self-extinguishing properties after ignition. On the other hand, the ionic liquid can protect the lithium anode and develop a robust SEI, thus giving the battery smooth long-cycle performance (Capacity retention rate at 1800th cycle: 89.06%). The innovative design idea of developing high-powered LIBs by introducing low-cost PA6 membranes into all solid compounds is appealing, and it can also be expanded to a combination of assorted polymers to encounter the requirements of a variety of batteries.