Volkswagen AG (VOW) bought a stake in battery startup QuantumScape Corp. with the aim of developing technology that can more than triple the range of its electric cars, according to people familiar with the matter.

VW is considering using the energy-storage technology, which is fireproof, for vehicles from the namesake brand as well as Porsche and Audi, said the people, who asked not to be identified because the plans are private. Tests to show the system is viable for cars are due to be completed in mid-2015, they said. The VW of America unit bought a 5 percent holding and has options to raise the stake, one of the people said.