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

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 O-2 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 mAh g(-1) at 100 mA g(-1). Additionally, it also achieves a smaller overpotential of 1.02 V under a cutoff capacity of 1000 mAh g(-1) and a longer cycle life of 90 cycles at 100 mA g(-1). This work provides new insights into designing efficient bifunctional catalyst for LOBs. (C) 2020 Published by Elsevier B.V.

Automated summary

Rechargeable non-aqueous lithium oxygen batteries (LOBs) are considered promising next-generation battery technologies due to their high theoretical energy density, but face challenges due to slow reaction kinetics and parasitic reactions. This study successfully fabricated self-standing ZnCo2S4 nanosheet arrays as efficient cathodes for LOBs, with a hollow and porous structure that enhances catalytic activity and improves ion transportation. The introduction of Zn in the ZnCo2S4 structure increases catalytic activity, leading to high initial discharge capacity, smaller overpotential, and longer cycle life.