The Energy Density of Lithium-Ion Batteries

Chapter 14 examines the development of lithium-ion batteries, focusing on energy density growth and cost trends. Lithium-ion technology, introduced commercially in 1991 by Sony and Asahi Kasei, relies on intercalation of lithium ions between a cathode and an anode through an electrolyte and separator. Key contributions came from M. Stanley Whittingham, John Goodenough, and Akira Yoshino, who received the 2019 Nobel Prize in Chemistry. From 1990 to 2024, energy density increased slowly—about 5% to 8% annually—resulting in a doubling time of 16 to 19 years, indicating linear rather than exponential growth. In contrast, cost per kilowatt-hour has declined exponentially. The highest reported energy density for a liquid-based cell is 711 Wh/kg, achieved in research but not yet commercialized. Future advances include solid-state batteries, which replace liquid electrolytes with solid materials, promising higher energy density, improved safety, and extended range for electric vehicles, with BYD planning deployment by 2027.