Construction of Hierarchical 2D PANI/Ni3S2 Nanosheet Arrays on Ni Foam for High-Performance Asymmetric Supercapacitors

In this work, a hierarchical 2D polyaniline (PANI)/Ni3S2 nanosheet arrays on Ni foam (NF) with open network was successfully developed by the growth of Ni3S2 nanosheet arrays derived from 2D Ni-MOF templates followed by the electrodeposition of a layer of PANI nanoflakes. The as-prepared PANI/Ni3S2/NF was served as self-standing supercapacitor electrode. The optimized PANI/Ni3S2/NF-100 electrode exhibits a high areal capacity of 1.56 mA h cm(-2) (487.5 mA h g(-1)) at 5 mA cm(-2) and good rate capability (57.7 % retention at 50 mA cm(-2)), which significantly outperforms individual PANI/NF or Ni3S2/NF. Furthermore, an asymmetric supercapacitor fabricated by PANI/Ni3S2/NF-100 and activated carbon electrodes can deliver a high energy density of 48.3 W h kg(-1) at a power density of 799.8 W kg(-1) with outstanding durability (85.7 % retention of the initial capacity) during 15000 consecutive charge-discharge cycles. The superior electrochemical performance of PANI/Ni3S2/NF-100 is attributed to the unique hierarchical PANI/Ni3S2 nanosheet arrays structure. Firstly, the hierarchical open network facilitates the electrolyte ions transport. Secondly, the ultrathin 2D Ni3S2 nanosheets lead to abundant electroactive sites for the Faradaic process, and the conductive PANI layer builds superb highway for fast electron transfer. Thirdly, the free-standing electrode enables fast redox reaction and low interfacial resistance. Finally, the synergetic effect of Ni3S2 and PANI also contributes to the enhanced capacity.