<p>Cellulose-based ionogels are promising for flexible electronics and energy devices, yet their performance is often constrained by the trade-offs among mechanical robustness, ionic conductivity, and thermal stability. Here, we propose a synergistic strategy that integrates dual-ions complexation with crystallization-induced molecular assembly to fabricate a cellulose ionogel. This strategy results in a comprehensive ionogel (noted as Cry-gel) with high mechanical strength (2.3 MPa in tension and 5.3 MPa in compression) and high ionic conductivity (96.8 mS cm⁻¹). Moreover, the Cry-gel can maintain impressive structural stability across a temperature range of −40 to 80 °C. Flexible thermoelectric devices and smart sensors derived from Cry-gels demonstrate a voltage of 0.28 V at a temperature gradient of 60 K, an impressive Seebeck coefficient of 6 mV K⁻¹, and high sensitivity to pressure, temperature, touch, and human pulse. This work provides a paradigm for creating multifunctional sustainable materials, effectively bridging the gap between high-performance ionogels and their applications in cutting-edge bioelectronics and energy harvesting systems.</p>