A highly ionic conductive succinonitrile-based composite solid electrolyte for lithium metal batteries

Solid-state Li metal batteries with solid electrolytes have built a potential way to solve the safety and low energy density problems of current commercial Li-ion batteries with liquid electrolyte. As a key component of solid-state Li metal batteries, solid electrolytes require high ionic conductivities and good mechanical properties. We have designed a composite solid electrolyte (CSE) consisting of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO)-succinonitrile (SN) and Li bis(trifluoromethylsulphonyl)imide (LiTFSI). The PVDF-HFP-based porous matrix made by electrospinning ensures good mechanical properties of the electrolyte membrane, and the large proportion of SN filling material makes the electrolyte membrane have an ionic conductivity of 1.11 mS·cm^–1 without the addition of liquid electrolyte. The symmetric battery assembled with CSE can be cycled stably for more than 600 h, and the LiFePO₄|CSE|Li full battery can also be cycled stably for more than 200 cycles. In addition to Li metal batteries, Li-O₂ and Li-CO₂ batteries that use CSE as electrolytes also have good performances, reflecting the universality of CSE. CSE does not only guarantee good mechanical properties but also obtain a high ionic conductivity. This design provides a new idea for the commercial application of polymer-based solid batteries.