Biologically benign, dissolvable materials-based triboelectric nanogenerators hold significant potential as a sustainable power source for bioresorbable, transient electronic systems; however poor options in materials and engineering approaches are major obstacles to the desired electrical, physical, and mechanical properties, particularly when considering operations under restrictive, demanding conditions or environments. Here, we present an elastomeric composites-based triboelectric nanogenerator with a package of completely degradable materials. Assembly of inorganic nanoparticles with high charge affinity/permittivity and micro-pyramid structures with high surface area produces enhanced charge density and power outputs over those of existing elements. Study on mechanical and biochemical characteristics validates the capability of maintaining stable, long-life electrical outputs under cyclic tests and aqueous solutions. Demonstrations of energy harvesting at an artificial knee and self-powered motion sensing at a finger joint suggest the practical feasibility in versatile areas of biomedical and eco-resorbable electronics.