The thermal stability and intrinsic thermal conductivity of self-powered electronic devices under high-temperature conditions are critical for the long-term operation of triboelectric nanogenerators (TENGs) in harsh environments. In this study, cellulose nanofiber/boron nitride/MXene ternary composite films were achieved by vacuum-assisted filtration. The composite films achieved an excellent thermal conductivity coefficient of 16.72 W m −1 K −1, which is 345 % higher than that of 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized cellulose nanofiber (TOCNF) films. The TENGs assembled by composite films yielded an open-circuit voltage of 79.6 V, a short-circuit current of 7.6 μA, an accumulated charge of 30.7 nC, and a maximum power density of 272.5 mW m −2. More importantly, the TENGs maintained outstanding triboelectric output performance (voltage up to 55.8 V) even at an extreme high temperature of 270 °C. The TCBM-TENGs can be functioned as a self-powered pressure sensor, enabling real-time monitoring of human motion. This work presents an effective strategy to enhance the environmental tolerance and thermal conductivity of triboelectric materials for high-performance energy harvesting and self-powered sensing in harsh environments.