Synergistically enabling the interface stability of lithium metal batteries with soft ionic gel and garnet-type Li6.4La3Zr1.4Ta0.6O12 ceramic filler

Lithium metal batteries based on solid electrolytes are considered as promising candidates with high energy density and safety. However, the weak solid-solid contact between electrolyte and electrode can easily lead to interface instability and lithium ions discontinuous migration, which seriously reduces the electrochemical performance of the battery. Herein, we construct a soft gel interfacial layer to improve the stability of the solid-solid interface between electrolyte and electrode by means of polyester-based monomers and imidazole-based ionic liquids. Based on this, garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles as inorganic ceramic filler were introduced in the layer to obtain composite electrolytes with high ionic conductivity (up to 1.1 × 10−3 S/cm at 25 °C). As a result, the assembled lithium symmetric battery of Li|THCE-15%LLZTO|Li suggests excellent cycling stability with 700 h at 0.1 mA/cm2 at 50 °C, and the lithium metal batteries of LFP|THCE-15%LLZTO|Li delivers high initial discharge capacity of 128.2 mA ·h/g with capacity retain of 75.48% after 150 cycles at 2 C. This work paves a new route to build safe and stable lithium metal batteries with synergistic introduction of composite electrolytes between electrolyte and electrode using soft gel interfacial layer and inorganic filler.