Abstract: Self-powered technology provides an effective solution to the energy supply challenges in fields such as wearable electronics and distributed sensor networks, showing broad application prospects. Based on the galvanic cell principle, a self-powered humidity sensor was designed and fabricated. Sodium alginate (SA), graphene oxide (GO), and lithium chloride (LiCl) were utilized as core functional materials for the sensor, and the sensor is prepared by a simple and scalable solution casting-adhesion process. The electrodes are constructed with conductive aluminum and copper foil tape, balancing economic efficiency and practicality. The sensor performance was optimized by adjusting the LiCl concentration. The results demonstrate that the optimized sensor exhibits excellent humidity-sensing characteristics in a wide relative humidity (RH) range of 11%~97%, with response and recovery times as low as 25 s and 22 s, respectively. Additionally, it possesses outstanding long-term stability, cyclic repeatability, mechanical flexibility, and recyclability, meeting the requirements for continuous and reliable monitoring applications. Constructing a series sensor array enables effective charging of capacitors and stable driving of LEDs, good application prospects in physiological health monitoring scenarios, such as real-time breathing monitoring and recognition, non-contact sensing, and diaper humidity detection, can be shown. This study provides an innovative technical reference for the development of self-powered humidity sensors adaptable to multiple scenarios, and plays a positive role in promoting technological progress in the field of sustainable electronic devices.