This paper covers a new type of batteries that allows the following possibilities for high-temperature applications, namely: (a) safety and full operational capability at temperatures up to 275 °C (527 °F); (b) possibility of battery recharging at high temperatures; (c) full operational capability under severe industrial conditions (vibration, shock); (d) environmental safety under transportation, storage, use and disposal; (e) safety under harsh conditions including emergency situations as a fire (this has been demonstrated with discharge tests of battery prototypes placed in a diesel fuel fire). Two technological generations of the battery prototypes have been designed, fabricated and tested over an operating temperature range of 4 °C (39 °F) to 275 °C (527 °F). The battery prototypes have been also tested under super-harsh conditions. The variety of form-factors is available for this type of batteries, including for their application in MWD/LWD tools and long-term power supply of monitoring systems in producing wells. Efforts are underway to develop the third generation of the batteries of sub-micron size (micro-batteries for microelements including high-temperature ones).