Researchers at Dalhousie University in Canada tested a new lithium-ion cell battery that could last for roughly 20 years, or one million miles. The best today can give 5 to 6 years. The research was funded by TESLA and like other Tesla batteries these are also lithium-ion .The key to these batteries, is their ability to run even in extreme weather conditions. These are made of a specific type of cell that uses electrolytes capable of holding higher charge at higher temperatures over a longer time span. The new batteries could be used in Robo Taxis.