In-situ engineered highly crystalline polythiophene empowered electrochemical capacitor-I: Synthesis, characterization, and electrochemical charge storage We report on synthesis of highly crystalline polythiophene and its application in supercapacitor electrodes. The material exhibits a remarkably stable electrochemical behavior and an excellent device performance. The device delivers an electrode specific capacitance (Csp) of 129.13F g−1, Cell Csp of 32.28F g−1 at 0.5 A/g; energy, and power densities of ∼ 3 Wh kg−1 and 250 W kg -1, respectively at 0.5 A/g. Also, it exhibits an excellent retention of Cell Csp and coulombic efficiency up to ∼ 95 % over 10,000 continuous galvanostatic charge discharge (GCD) cycles indicating a remarkable performance by a standalone, pristine and undoped polythiophene. Electrochemical impedance spectroscopy (EIS) studies further suggest material’s stable capacitive behavior. The material’s enhanced electrochemical properties, stable behavior and outstanding performance in device application are attributed to the crystalline phases present in the polymer matrix achievable via a slow rate of synthesis; overall, an edge over other conventional synthesis methods. 365 Elsevier