This paper presents a high-efficiency single-inductor triple-source energy harvesting interface for battery-Assisted internet of things (IoT) applications. The proposed converter is capable of harvesting energy from two photovoltaic cells and a thermoelectric generator while providing a 1.2-V regulated output and managing the battery. In addition, a negative internal voltage is produced to improve the efficiency at low input voltage. Four operating modes are employed according to the environment and loading conditions: harvesting mode (HM), storing mode (SM), boosting mode (BTM), and battery mode (BM). The simulation result shows a 87.7%, 91.9% and 93.4% peak efficiency are achieved at harvesting mode, boosting mode and battery mode, respectively.