Designing of root-soil-like polyethylene oxide-based composite electrolyte for dendrite-free and long-cycling all-solid-state lithium metal batteries.

• An all-solid-state root-soil-like composite electrolyte are successfully prepared. • Composite electrolyte present excellent mechanical strength, ionic conductivity and thermal stability. • Composite electrolyte can provide more transmission channels for Li+ ions and inhibit the growth of lithium dendrites. • Li symmetric battery and Li|LiFePO 4 battery with the composite electrolyte present stable long cycle performance and safety. Lithium metal with excellent theoretical specific capacity and low reduction potential is thought as the promising anode material for energy storage device. However, the issues of weak security and poor cycle life resulted from the lithium dendrites growth have greatly limited their quick development. In this study, the electrospun polyvinylidene fluoride (PVDF) nanofiber membrane with multi-level structure was introduced into the polyethylene oxide (PEO) polymer as a nano-polymer filler to construct an all-solid-state root-soil-like composite electrolyte. The mutual overlaps of the coarse fiber and the fine fiber in the membrane provide a strong skeleton support for the electrolyte, and the intermolecular hydrogen bond between the PVDF and PEO can further enhance the interfacial interaction between the membrane and polymer, which in turn make the root-soil-like composite electrolytes have excellent mechanical strength to inhibiting the growth of lithium dendrites. Moreover, the existence of the multi-level structure in the membrane can significantly reduce the crystallinity of the polymer and provide more transmission channels for Li+ ions, so that Li+ ions can be uniformly and rapidly deposited during the plating/stripping process, and the interface compatibility between the lithium anode and electrolyte can be effectively enhanced. The voltage value of the Li symmetric battery can be stabilized at 70 mV for 1000 h under 0.3 mA cm−2. And the discharge capacity decay rate of the Li|LiFePO 4 battery after 600 cycles at 1 C is only 0.04% per cycle. The study will provide a promising electrolyte candidate for high energy all-solid-state lithium metal batteries. [ABSTRACT FROM AUTHOR]