Porous hollow ZnCo2S4 nanosheet arrays derived from metal-organic framework as efficient cathode for lithium oxygen batteries

Abstract

Abstract Rechargeable non-aqueous lithium oxygen batteries (LOBs) have attracted extensive attention as the most promising next-generation battery technologies due to their extremely high theoretical energy density. However, their practical applications are hampered by sluggish reaction kinetics and severe parasitic reactions, resulting from the insulating and insoluble discharge product-Li2O2. Herein, self-standing ZnCo2S4 nanosheet arrays derived from metal-organic framework (MOF) via low-temperature solvothermal sulfuration method, are fabricated as efficient cathode for LOBs. The hollow structure of ZnCo2S4 nanosheet formed during sulfuration provides more catalytic sites and alleviates stress during repeated discharge/charge progress, while three-dimensional (3D) porous architecture inheriting from MOF shortens the transportation pathway of Li+ and O2 in electrolyte. Compared with pure CoS derived from Co-MOF, more Co3+ exposes on ZnCo2S4 surface due to the introduction of Zn, enhancing the catalytic activity distinctly. Benefitting from the bifunctional catalytic performance, the ZnCo2S4 cathode exhibits an extremely high initial discharge capacity of 9505\u202fmAh g−1 at 100\u202fmA\u202fg−1. Additionally, it also achieves a smaller overpotential of 1.02\u202fV under a cutoff capacity of 1000\u202fmAh g−1 and a longer cycle life of 90 cycles at 100\u202fmA\u202fg−1. This work provides new insights into designing efficient bifunctional catalyst for LOBs.