Electrode binders play a crucial role in electrochemical performance and stability of supercapacitors. Polyvinylidene fluoride (PVDF) with N-methyl-2-pyrrolidone (NMP) solution as an electrode binder for energy storage systems is prompting environmental and health concerns due to its high toxicity and cost. Thus, it has been restricted in both the European Union (EU) and the United States (US). Herein, the electrode using tapioca starch (TS) as binder was fabricated to be cost effective, safe, and performance-promising alternative for supercapacitors. Electrode material with activated carbon, carbon black, and binder with weight ratio 8:1:1 and 9:0.5:0.5 with temperature 100 °C were studied to select the best formulation that flexible, no cracking and stable in electrochemical performance. The 8:1:1 weight ratio electrode (TS100-1) with 100 °C preparation temperature demonstrated the best performance, showing good flexibility without cracking. This has been confirmed with the SEM morphology analysis. TS100-1 also passed both the wettability and electrolyte stability test. The electrochemical performance of the fabricated electrode was evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in water-in-salt electrolyte (WiSE) system. The potential window of the selected WiSE could reach up to 2.2 V. The maximum specific capacitance (Cs) of TS100-1 is 330.24 Fg−1 with energy density of 221.99 Whkg−1 at 1A. This research revealed the potential of tapioca starch as an alternative binder to produce stable, high-performance, and environmentally friendly supercapacitors.