Flexible Lithium‐Ion Conducting Composite Electrolyte

Abstract Incorporation of a solid electrolyte into lithium‐ion batteries brings with it the potential to increase energy density, improve operational lifetime, and enhance safety. Although numerous ceramics with high lithium‐ion conductivity have been identified, use in batteries is hindered by fragility, inefficiency of fabrication processes, and difficulty sintering to a hermetic state. We present a novel composite electrolyte with nearly single crystal grains of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 embedded within a flexible, PDMS polymer matrix. Each lithium‐ion conducting particle is exposed on both sides of the membrane to provide a fast conduction pathway that is unimpeded by grain boundaries. Membranes made with this structure and grains grown by slow cooling from the melt are hermetic and have lithium conductivity of ∼2.7×10 −4 S cm −1 . The principal conductivities of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 crystals are σ a =3.4×10 −3 and σ c =1.1×10 −3 S cm −1 .