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 behaviours. 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 LiNi0.8Co0.1Mn0.1O2 positive electrode (4 mAh cm–2).