Piezoelectric-driven self-charging supercapacitor power cells (SCSPCs) emerged as promising energy devices that can simultaneously harvest-, convert-, and store electrical energy in an integrated cell. Recent research efforts have been focused on (i) understanding the fundamental mechanism of the energy transduction process and (ii) improving the self-charging performances, respectively. Herein, we utilized the piezo-ionic properties of Nafion (solid polyelectrolyte) together with their bi-functional properties (separator cum electrolyte) in a SCSPC (using MoS₂ quantum sheets as energy storage electrodes) and examined their self-charging performance. The experiments on the evaluation of piezo-ionic properties of the Nafion polyelectrolyte showed that they can produce a peak-peak voltage of 910 mV due to the generation of Donnan potential. Next, studies on the electrochemical performance of solid state MoS₂-Nafion-MoS₂ SCSPC revealed that they possess a high capacity/capacitance (0.40 μAh cm⁻²/1.81 mF cm⁻²), energy density (252 μJ cm⁻²), and long-cycle life. Finally, studies on the self-charging characteristics of the MoS₂-Nafion-MoS₂ SCSPC show that they can self-charge upto 243 mV with superior electro-mechanical stability. Collectively, the piezo-ionic mediated energy transfer process in the self-charging process of the MoS₂-Nafion-MoS₂ SCSPC is explained in accordance with the Nernst theory for a two-dimensional system. This work opens-up a fresh paradigm towards the development of all-solid-state SCSPCs utilizing solid electrolytes.