Enabling room-temperature solid-state lithium-metal batteries with fluoroethylene carbonate-modified plastic crystal interlayers

Solid-state batteries (SSBs) with Li7La3Zr2O12 (LLZO) ceramic oxide electrolytes are attracting significant interest because of LLZO's non-flammability, excellent ionic conductivity, electrochemical stability against Li metal anodes, and processability in air. However, the poor solid-solid contact between the electrolyte and the electrodes leads to large interfacial impedances, which are detrimental to the functioning of LLZO-based SSBs. In this work, we modified the electrode vertical bar Ta-doped-LLZO (LLZTO) interfaces by employing a plastic crystal interlayer based on succinonitrile with a fluoroethylene carbonate additive. The interlayer, which can be easily applied, drastically reduces the interfacial resistances and allows the stable operation of Li-metal based batteries. A Li vertical bar LLZTO vertical bar LiFePO4 battery with this interlayer can stably cycle at room-temperature for 50 times at 0.1 C while still retaining a capacity of 140 mAh g(-1). The symmetric Li vertical bar LLZTO vertical bar Li cell with the interlayer can cycle at 0.2 mA cm(-2) for over 150 hours. It also has a higher critical current density for the growth of dendrites compared with an analogous cell without the interlayer. In short, this work provides a facile and efficient methodology to enhance the effective Li transportation rates at the electrode vertical bar electrolyte interfaces of SSBs and can be readily applied to other types of electrolytes beyond LLZO.