Tiny nanostructured high-energy power sources based on the direct conversion of nuclear energy to electricity are developed for power supply of microelectronic and micromechanical devices, as well as remote objects. The role of energy converters in such power sources is played by metal–insulator–metal (MIM) structures with a characteristic layer thickness of 10–100 nm, and highly thermodynamically stable and radiation resistant asymmetric supercapacitors comprising a nanostructured carbon electrode and an inorganic electrolyte possessing high thermodynamic and radiation resistance are applied for energy accumulation. The predicted autonomous operation time of the power sources is not less than 20 years, specific energy is 103 kWh/kg, and capacity is not less than 1 kWh/kg.