Grain boundary modification in garnet electrolyte to suppress lithium dendrite growth

The grain boundary modification gives the garnet electrolyte superior lithium dendrite suppression capability. [Display omitted] •Li6Zr2O7 is a novel additive for LLZT none mother powder sintering.•LLZT-LZO composite electrolyte possess high density and ionic conductivity.•Enhanced LLZT dendrite-suppression ability benefits from grain boundary modification.•Li-S battery exhibits excellent rate capability and long-term cycling performance. Solid-state batteries (SSBs) have attracted many attentions due to its higher energy density and improved safety. As one of the most promising solid electrolytes, garnet Li7La3Zr2O12 (LLZO) has achieved significant advances in its cell performance, however, its application in Li-metal batteries is still hindered by lithium dendrite growth at voids or grain boundaries inside the solid electrolyte. Herein, a novel grain-boundary enhancement strategy was demonstrated by introducing Li6Zr2O7 (LZO), which can be decomposed into Li2O in situ, into Ta-doped LLZO (LLZT). The Li2O provides a sufficient inner Li2O atmosphere, achieving none mother powder sintering. The Li2ZrO3 stays at garnet grain boundaries or fills up the pores, which have been shown to effectively suppress the lithium dendrite growth. More importantly, the critical current density (CCD) of the Li | LLZT-LZO | Li symmetric cell achieved as high as 1.4 mA cm−2 at 25 °C and 2.0 mA cm−2 at 60 °C, and the long-term lithium cycling remained stable over 2000 h at 0.3 mA cm−2. Moreover, the Li-S battery maintained high discharge capacity of 816 mAh g−1 after 200 cycles at 0.5C. Therefore, our work provides a facile and effective strategy to prepare a safety-enhanced electrolyte for future applications of SSBs.