2D SnSe Cathode Catalyst Featuring an Efficient Facet-Dependent Selective Li_2O_2 Growth/Decomposition for Li–Oxygen Batteries

摘要

2D materials are attracting much attention in the field of cathode catalysts for lithium-oxygen batteries (LOBs) due to their layered structure, unique electronic properties, and high stability. However, different stacking layer structures trigger different catalytic capabilities in LOBs. In this work, tin selenide nanosheets with a black phosphorus-like 2D structure are synthesized and used as the cathode catalyst for LOBs. SnSe nanosheets with exposed stack (200) facets and stack edge facets exhibit superior specific capacity over 20 783 mAh g(-1) and ultralong cycle stability over 380 cycles at 500 mA g(-1) in LOBs. This demonstrates that the growth of discharge products is mainly concentrated on the 2D surface (200) facets, rather than the stack edge facets. Experimental and theoretical studies reveal that the confined adsorption of Li2O2 on the stack edge facets of SnSe, due to the 2D layer structure and the unique electron distribution, restricts the growth of discharge products. The 2D surface facets of SnSe benefit for the formation and stabilization of LiO2 intermediates, leading to the efficient formation/decomposition of discharge products. The findings provide in-depth insight into the elusive electrocatalytic mechanism for 2D layer-structures materials in LOBs.