Electrodes-electrolyte interfacial engineering for realizing room temperature lithium metal battery based on garnet structured solid fast Li+ conductors

Li7La3Zr2O12 (LLZ) is one of the most promising solid electrolyte for all-solid-state batteries, owing to its high Li + conductivity and stability when in contact with lithium metal. However, LLZ has its own challenges in realizing high performance due to its high electrode/electrolyte interfacial resistance. To address this issue, we report a systematic investigation of interfacial resistance, with a metallic Li strip and a thin layer of Li deposition by thermal evaporation (TE) over dense and high Li + conductive pristine Al-LLZ (Li6.28Al0.24La3Zr2O12) and Au||Al-LLZ. Thermal treatment of Li (TE)||Au||Al-LLZ||Au||Li (TE) at 180 °C for 1-h exhibits a dramatic reduction in interfacial resistance along with stable Li platting/stripping at room temperature (25 °C). Scanning Electron Microscopic (SEM) investigation on the interface of the Li (TE)||Au||Al-LLZ||Au||Li (TE) reveals the formation of a favorable thin layer of Li-Au alloy through the heat treatment at 180 °C. A room temperature working cell with LiCoO2 as a cathode, metallic Li (TE) as anode and Al-LLZ as a solid electrolyte is possible by introducing a thin layer of Au at anode interface and a soft polypropylene interlayer at cathode interface.