Dual Anionic Vacancies on Carbon Nanofiber Threaded MoSSe Arrays: A Free-Standing Anode for High-Performance Potassium-Ion Storage

In spite of the low-cost and abundant potassium resources, the potential commercialization of potassium-ion batteries (PIBs) is still confined by the large-sized K+ ions and sluggish kinetic process. A flexible free-standing advanced anode for PIBs is synthesized by tactfully incorporating dual anionic vacancies on MoSSe arrays in combination of carbon nanofiber membrane (v-MoSSe@CM). The vacancy-rich MoSSe arrays in v-MoSSe@CM dramatically enhance the adsorption of K+ ions, leading to a higher capacity of 370.6 ​mAh g−1 at 0.1 ​A ​g−1 over 60 cycles as compared with that 168.5 ​mAh g−1 of vacancy-free MoSSe@CM. Meanwhile, the density functional theory (DFT) calculations demonstrate a facilitated ability for K+ insertion into v-MoSSe interlayers with a much more negative adsorption value of −1.74 ​eV than that (0.53 ​eV) of vacancy-free MoSSe. The thousands of carbon nanofiber-supported three-dimensional frameworks can not only inhibit the agglomeration of MoSSe nanosheets, but also remit the volume expansion and avoid possible collapse of the nanostructures during cycling, resulting into a high capacity retention of 220.5 ​mAh g−1 ​at 0.5 ​A ​g−1 after 1000 cycles. Therefore, this work uncovers the relationship between vacancy engineering and potassium-ion storage performance, guiding a feasible route to develop potential materials for potassium-ion battery.