Solid-state lithium-sulfur battery chemistries achieving excellent room-temperature cycle performance by high-quality Li7La3Zr2O12-based electrolyte

Abstract

The ceramic materials based on Li6.375La3Zr1.375Nb0.625O12 (LLZNO) with the LiX (XF, Cl, Br) additive have been prepared through the traditional solid−state sintering reaction. The phase evolution of solid-state electrolytes was studied using the X − ray diffraction (XRD) and Raman spectroscopy which confirmed that all prepared samples formed the cubic garnet-type structure. Also, the lattice distortion based on X− doping at partial O2− sites have been detected in the LLZNO by the XRD data. It was worth noting that, according to the observation of scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), the electrolytes were joint occurrence of anion (F−, Cl−, Br−) doping at LLZNO grains and lithiated interface at grain boundaries, thereby leading to the high densification and the excellent wetting. Therefore, the ionic conductivity and transport kinetics of ceramics were obviously improved after LiX (X = F−, Cl−, Br−) incorporation. Meanwhile, LiX addition into LLZNO sample can be conductive to the interfacial contact and lithium-ion movement between the electrode and the electrolytes. Additionally, a transition layer was introduced to further provide a stable contact with Li electrode. The Li| LLZNO/LiCl-Ag interface resistance decreases to 98.2 Ω cm2. The symmetric Li| LLZNO/LiCl-Ag |Li battery can cycle stably for 600 h at 0.2 mA cm−2 and room temperature without a short circuit. Moreover, the Li| LLZNO/LiCl |sulfur-carbon battery exhibited a capacity of 750mAh g−1 after 120th cycle at 0.2 C and room temperature, while maintaining the high coulombic efficiency (over 99.5%) and excellent cycling stability. These results indicate that the LLZNO/LiX ceramics are promising for the production of electrolyte and fabrication of lithium-sulfur batteries.