"The logic behind this is the circular economy," said Cecile Sobole, programme manager for Renault SA's EV business. "The battery coming from the electric vehicle will become more and more a part of the energy world." Yet as many companies dive in, the biggest US electric-car maker—Tesla—stays on the sidelines. The Palo Alto, California-based company said its batteries probably won't be suitable for a new task after 10 to 15 years of use, and it's focusing on recovering the raw materials. Repurposing efforts may slow if it becomes more profitable to extract materials like cobalt and simply make new batteries. Declining performance for an EV battery is evidenced by fewer miles of driving per charge and more frequent plug-ins by owners. The components typically will be swapped out after about a decade in family cars and four years in harder-working buses and taxis.