Li6.75La3Zr1.75Ta0.25O12@amorphous Li3OCl composite electrolyte for solid state lithium-metal batteries

Li7La3Zr2O12 (LLZO) garnet-type oxide has become a promising inorganic electrolyte for solid-state lithium-ion batteries due to its high ionic conductivity and good chemical stability with the lithium metal. However, the poor wettability of LLZO garnet-type oxide with lithium metal and its incompact structure have impeded their extensive applications in solid-state lithium-ion batteries. Herein, Li6.75La3Zr1.75Ta0.25O12 (LLZTO) particles were embedded in the amorphous Li3OCl to form an integrated composite electrolyte (LLZTO-2wt.% Li3OCl) with compact and stable structure at 350 °C, which presents high ionic conductivity (2.27 × 10−4 S cm−1), low interfacial resistance and high electrochemical stability (up to 10 V vs. Li/Li+) at room temperature. The amorphous Li3OCl acting as a binder, filler and bridge promotes the formation of an integrated composite electrolyte and continuous ionic conductive network among LLZTO particles. Furthermore, the Li3OCl with excellent affinity to lithium metal in-situ reacts with the lithium metal to form a stable and dense interfacial layer, which greatly decreases the interfacial resistance between the composite electrolyte and lithium metal (from 1850 to 90 Ω cm2). The interfacial layer allied compact composite electrolyte also effectively suppresses the lithium dendrite growth during lithium plating-striping. The symmetrical Li/LLZTO-2wt.% Li3OCl/Li cell can stably cycle 1000 h without short circuit. The stable specific capacity of solid-state LiFePO4/LLZTO-2wt.% Li3OCl/Li battery is as high as 157.5 mAh g−1 and 85.7 mAh g−1 at 0.05 C and 0.5 C, respectively. Combining the garnet-type electrolyte with amorphous Li3OCl is a promising way to develop the compact garnet-type electrolyte at low temperature for solid-state lithium-ion batteries.