High-performance black phosphorus (BP)-based micro-supercapacitors (MSCs) hold immense promise for wearable electronics but remain hampered by the material’s intrinsic instability and sluggish electron kinetics. Herein, a two-dimensional phosphorene and bismuthene (2D BP/Bi) heterojunction via liquid nitrogen-assisted exfoliation and mask-assisted filtration was developed as a robust bifunctional electrode for integrated flexible energy-sensing systems. The heterostructure effectively suppresses nanosheet restacking and enhances interfacial stability through strong P-O-Bi covalent bonding and interfacial synergy. Simultaneously, the incorporation of bismuthene constructs high-speed electron transport channels, significantly facilitating ion diffusion and charge transfer. Consequently, the optimized electrode achieved a high areal capacitance of 7.6 mF cm^-2 (1.6-fold enhancement over pure BP) and an ultra-long lifespan with 92.1% retention after 30,000 cycles. Notably, by tailoring the gel electrolyte with DMSO, the device exhibited remarkable freeze-tolerance, maintaining 70% capacitance at -35 °C. Furthermore, an all-flexible integrated system combining the MSC with a pressure sensor was constructed using graphene current collectors, enabling continuous, self-sustained physiological monitoring. This work offers critical insights into interface engineering for designing high-performance BP-based MSCs and paves the way for extreme-environment wearable applications.