Heterogeneous Mediator Enabling Three-Dimensional Growth of Lithium Sulfide for High-Performance Lithium-Sulfur Batteries

Two-dimensional(2D)deposition regime of insulating lithium sulfide(Li_(2)S)is a major obstacle to achieve high reversible capacity in the conventional glyme-based lithium-sulfur(Li-S)batteries as it leads to rapid loss of active electrode surface and low sulfur utilization.Achieving three-dimensional(3D)growth of Li_(2)S is therefore considered to be necessary,but the available strategies are mainly based on the electrolyte manipulations,which inevitably lead to added complexity of the electrode-electrolyte compatibility and,in particular,instability of the lithium anode.In this work,we have developed a heterogeneous polysulfide mediator composed of discrete Mo_(5)N_(6) anchored on graphene,which functions on the cathode side,to regulate the deposition mode of Li_(2)S.Mo_(5)N_(6) can efficiently boost the formation of Li_(2)S as demonstrated by a series of experimental and computational results.More importantly,the discrete distribution of Mo_(5)N_(6) nucleants on graphene postpones the merging of adjacent Li_(2)S nuclei to promote their isotropic growth.Thus,3D deposits of Li_(2)S is guided by the heterogeneous mediator.Benefiting from these unique superiorities,Li-S cells with high rate capability of 954 mAh g^(-1) at 2 C and long cycle life exceeding 1000 cycles are realized without advanced lithium anode protection.