Sulfur defect engineering controls Li₂S crystal orientation towards dendrite-free lithium metal batteries

Controlling nucleation and growth of Li is crucial to avoid dendrite formation for practical applications of lithium metal batteries. Li₂S has been exemplified to promote Li transport, but its crystal orientation significantly influences the Li deposition behaviors. Here, we investigate the interactions between Li and various surface structures of Li₂S, and reveal that the Li₂S(111) plane exhibits the highest Li affinity and the lowest diffusion barrier, leading to dense Li deposition. Using sulfur defect engineering for Li₂S crystal orientation control, we construct three-dimensional vertically oriented Li₂S(111)@Cu nanorod arrays as a Li metal electrode substrate and identify a substrate-dependent Li nucleation process and a facet-dependent growth mode. Furthermore, we demonstrate the versatility of the Li₂S(111)@Cu substrate when paired with two positive electrodes: achieving an initial discharge capacity of 138.8 mAh g^-1 with 88% capacity retention after 400 cycles at 83.5 mA g^-1 with LiFePO₄, and an initial discharge capacity of 181 mAh g^-1 with 80% capacity retention after 160 cycles at 60 mA g^-1 with commercial LiNi_0.8Co_0.1Mn_0.1O₂ positive electrode (4 mAh cm^-2).