Cycle stability of lithium/garnet/lithium cells with different intermediate layers

The garnet-type electrolytes such as Ta-doped Li₇La₃Zr₂O₁₂ (LLZTO) have been viewed as the promising electrolytes for solid-state lithium batteries, but it exhibits problem of high interfacial resistance (1960 Ω·cm²) and short circuit when being cycled in Li/LLZTO/Li cells at the current density above 0.5 mA·cm⁻². Introduction of intermediate layers in between lithium and LLZTO is helpful for decreasing the interfacial resistance and suppressing the growth of lithium dendrites. In this work, three kinds of intermediate layers of Au, Nb and Si with the thickness of 100 nm were prepared. Although the interfacial resistance with the Au layer decreases from 1960 to 32 Ω·cm², the cells can only cycle for 0.67 h at 0.5 mA·cm⁻², related to the Au peeled off from the LLZTO. The Nb layers lead to the initial interfacial resistance of 14 Ω·cm², while showing extension of cycle time to 50 h with the increase in interfacial resistance due to the formation of the resistive Li–Nb–O phase. The Si layers induce the interfacial resistance as low as 5 Ω·cm² and the cycles as long as 120 h, which is attributed to the improvement in electrical contact between Li and electrolyte as well as the maintenance of conductive interface during cycles.