In this study, we develop a stretchable/self-healable polymer, PEDOT:PAAMPSA:PA, with remarkably high ionic thermoelectric (iTE) properties: an ionic figure-of-merit of 12.3 at 70% relative humidity (RH). The iTE properties of PEDOT:PAAMPSA:PA are optimized by controlling the ion carrier concentration, ion diffusion coefficient, and Eastman entropy, and high stretchability and self-healing ability are achieved based on the dynamic interactions between the components. Moreover, the iTE properties are retained under repeated mechanical stress (30 cycles of self-healing and 50 cycles of stretching). An ionic thermoelectric capacitor (ITEC) device using PEDOT:PAAMPSA:PA achieves a maximum power output and energy density of 4.59 μW‧m−2and 1.95 mJ‧m−2, respectively, at a load resistance of 10 KΩ, and a 9-pair ITEC module produces a voltage output of 0.37 V‧K−1with a maximum power output of 0.21 μW‧m−2and energy density of 0.35 mJ‧m−2at 80% RH, demonstrating the potential for a self-powering source.