AbstractConverting building and environment heat into electricity is a promising strategy for energy harvest to tackle global energy and environmental problems. The processing challenges, mechanical brittleness, and low environmental tolerance of typical thermoelectric materials, however, prevent them from realizing their full potential when employed in outdoor building systems. Herein, a general concept based on synergistic ionic associations to significantly improve the mechanical properties and harsh environment stability for high‐performance ionic‐type thermoelectric (i‐TE) gels is explored. They demonstrate extraordinarily high stretchability (1300–2100%), fast self‐healing (120 s), temperature insensitivity, and great water‐proof performance, and could be painted on a variety of surfaces. The n‐type ionic Seebeck coefficient is up to −8.8 mV K−1and the ionic conductivity is more than 0.14 mS cm−1. Both exhibit remarkable thermal and humidity stability (293–333 K, 20–100 RH%), which are rarely achieved in previous studies. Even on a cloudy day, the open‐circuit thermovoltage for a painted i‐TE array with an area of about 8.5 × 10−3m2is above 2 V. This research offers a promising approach for gathering significant waste heat and even solar energy on outside building surfaces in an effective and sustainable manner.