Chemical interface engineering of solid garnet batteries for long-life and high-rate performance

The solid garnet battery is viewed as one of the most attractive candidates for investigating the solid-state lithium batteries with high energy density and safety. However, the crucial interfacial problems between the solid electrolytes and the electrodes severely hinder the improvement of battery performance. In this work, the reactive intermediate layers are introduced in between the garnet electrolytes and the electrodes. On the anode side, the ether-based electrolyte layer is in-situ converted into a gradient solid-electrolyte-interphase (SEI) film with the organic-rich outer layer and the inorganic-rich (LiF and Li3N) inner layer, leading to the conductive contact and the homogeneous potential distribution. Consequently, the modified Li symmetric cells exhibit the dendrite-free Li plating/stripping at the remarkable current density as high as 2.1 mA cm−2 at 60 °C. On the cathode side, the ionically conducting species composed of solid-phase LiF and Li3N is in-situ formed through the decomposition of the 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-based ionic liquid layer, leading to the decreased interfacial resistance and enhanced Li+ conduction. The resultant LiNi0.6Co0.2Mn0.2O2/Li batteries with the residual liquid-phase electrolytes at the solid-phase boundaries deliver the high discharge capacity of 162.4 mAh g−1 with the capacity retention of 87.6% after 100 cycles at 0.2C and 60 °C. This work demonstrates a useful strategy to make the ideal interfaces through the in-situ conversion reactions for construction of high-performance solid garnet batteries.