M. Stanley Whittingham, working for the oil company Exxon during the energy crisis of the 1970s, develops the first functional lithium-based battery, exploiting metallic lithium's great capacity for releasing electrons easily, but the design proves unstable and prone to spontaneous combustion, severely limiting its commercial viability. John Goodenough, at the University of Oxford, discovers in 1980 that lithium cobalt oxide can act as a far more efficient and stable cathode, capable of generating considerably higher voltages than the materials Whittingham used, an improvement that would become the foundation of virtually every commercial lithium battery thereafter. Akira Yoshino, at the Japanese corporation Asahi Kasei, solves the remaining safety problem in 1985 by replacing pure metallic lithium, inherently unstable, with a carbon material able to safely house lithium ions with no risk of spontaneous combustion, thereby completing the design of the first safe, commercially viable, rechargeable lithium-ion battery. Sony commercializes the first lithium-ion battery in 1991. This lightweight, hundreds-of-times rechargeable, high-energy-density technology becomes the standard power source for mobile phones, laptop computers, and, decisively for the 21st-century energy transition, electric vehicles.