Soft ionic conductors are ideal candidates for applications in wearable electronics, soft robotics, and human-machine interfaces. However, achieving a balance between mechanical performance and ionic conductivity remains challenging. Besides, hydrogel-based conductors typically fail at sub-zero temperatures. To overcome these concurrent limitations, we report a fully solid-state ionic conducting elastomer featuring a multi-ionic (LiTFSI/ChCl) dual-network derived from biomass. Molecular dynamics and density functional theory simulations verify synergistic Li─O coordination and hydrogen-bonding networks, which enable a rare combination of mechanical strength (0.877 MPa, 587% elongation) and high ionic conductivity (3.74 × 10−3 S·m−1). The strain sensors based on the elastomers enable stable motion sensing at −20°C and Morse code anti-counterfeiting. Moreover, the elastomer serves as a stretchable triboelectric nanogenerator. At a resistance of 1 MΩ, the power density at −30°C increases to 290% of the value measured at room temperature, demonstrating its potential as a reliable and eco-friendly alternative to conventional batteries in low-temperature conditions. This work provides a novel design strategy for durable, high-performance ionic conductors, paving the way for their use in extreme environment.