Porous Mo-Co-S Nanosheets on Carbon Cloth for All-Solid-State Flexible Asymmetric Supercapacitors

High-performance and flexible supercapacitors (SCs) have great potential for powering wearable and portable devices. Herein, Mo-doped Co9S8 porous nanosheets on carbon cloth (denoted as Mo-Co-S/CC) are prepared for all-solid-state flexible asymmetric SCs via a two-step method. Na2MoO4 is selected as both Mo source and etching agent to create Mo-doped porous structure, which provides plenty of reaction sites contributing to the decrease of electrochemical barrier and increase of electrochemical performances. The Mo-Co-S/CC electrode demonstrates a high specific capacity of 771.5 F g(-1) at 2 A g(-1), excellent rate capability of 660.0 F g(-1) at 20 A g(-1), and 109% cycling capacitance retention after 30 000 cycles. By using poly(vinyl alcohol)/KOH (PVA/KOH) gel as electrolyte, a flexible all-solid-state asymmetric supercapacitor (Mo-Co-S/CC//KOH//AC/CC, FASCs) is assembled, which can work under different bending angles and deliver a specific capacitance of 37.37 F g(-1) at 1 A g(-1). Furthermore, the FASCs can deliver a maximum energy density of 14.68 Wh kg(-1) at power density of 369 W kg(-1), with the capacity retention of 80.07% over 30 000 cycles at a high rate of 20 A g(-1).