Dense Li1.5Al0.5Ge1.5(PO4)3 ceramics with 2D-MoS2 interlayer for all-solid-state lithium metal batteries

Abstract

in addition, partially reacted LAGP powders were prepared to analyze the sintering kinetics. LAGP ceramics with 94.2% relative density, 2.3 x 10$^{-4}$ S cm$^{-1}$ maximum ion conductivity at room temperature, 0.34 eV activation energy, and 1 mA cm$^{-2} critical current density were obtained. We also prepared an interlayer of 2D molybdenum disulfide (MoS2) for LAGP ceramics by two fabrication methods: the mechanical process of MoS$_2$ polishing and the arrangement of exfoliated MoS$_2$ nanosheets. Therefore, Li ions are effectively intercalated into the MoS$_2$ interlayer to form a stable interface, which prevents the formation of MCI. Due to the interface modification with MoS$_2$, the interfacial resistance between Li and LAGP reduced dramatically and the cycle life of Li symmetric cells was enhanced from 24.5 h to 83.5 h at 0.5 mA cm$^{-2}$ current density. Additionally, the critical current density of LAGP was increased to 1.5 mA cm$^{-2}$. This study provides the key characteristics to optimize the interlayer material for high performance all-solid-state lithium metal batteries.

NASICON-type lithium aluminum germanium phosphate (Li$_{1.5}$Al$_{0.5}$Ge$_{1.5}$(PO$_4$)$_3$, LAGP) is regarded as one of the most promising solid electrolytes due to good chemical stability with various active materials. However, a number of recent studies have raised the awareness behind the issues of mixed conducting interphase (MCI) forming between LAGP and Li interface due to the degradation of ionic conductivity and fracture of LAGP with volume change during cycling. In this study, we achieved dense LAGP ceramics via pressureless sintering