Pseudocapacitive electrode materials employed in supercapacitors may bring in high energy density (ED) and specific capacitance (C-sc) which are critical for their practical applications. Accordingly, logical design of advanced electrode materials is highly demanded to progress high-performance supercapacitors. Here, for the first time, we suggest a straightforward route for the synthesis of NiGa2S4-rGO as an advanced cathode material supported on nickel foam (NF) for employed in flexible solid-state asymmetric supercapacitors (FSASCs). Due to an abundant ratio of active sites and large surface area of the NiGa2S4-rGO advanced material, the as-prepared NiGa2S4-rGO/NF electrode illustrates considerable electrochemical properties including remarkable specific capacitance (C-sc) of 2124.34 F g(-1) with excellent rate capability of 73%, and exceptional durability, which are better than NiGa2S4/NF and previously reported transition metal sulfides (TMSs). Furthermore, for the first time a pseudocapacitive advanced anode material of FeSe2-rGO have been successfully fabricated on a nickel foam (NF) substrate by a facile strategy. Element Selenium as the favorable element was offered into the Fe for enhancement and adjustment of the anode material electrochemical performance. The FeSe2-rGO/NF advanced anode electrode presents satisfactory electrochemical properties containing an exceptional specific capacitance (C-sc) of 432.40 F g(-1), significant rate performance of 57.84% and superior durability, which are better than FeSe2/NF electrode and previously studied Fe-based anode material. Considering the remarkable electrochemical performance of the as-prepared pseudocapacitive advanced electrode materials, a FSASC based on the NiGa2S4-rGO/NF as the cathode electrode and FeSe2-rGO/NF as the anode electrode was assembled. The FSASC device delivers superior C-sc of 341.20 F g(-1), outstanding energy density (ED) of 121.31 W h kg(-1), remarkable cycle stability (only 7.30% damage after 5000 charge/discharge (CD) cycles). (C) 2018 Elsevier Inc. All rights reserved.