By 2020 ‘gigafactories’ in Europe and the US should each produce lithium ion batteries with a capacity, per annum, of over 100 GWh. Review the chemistry involved in the development of commercial lithium ion batteries (J.B. Goodenough and K.-S. Park, J. Am. Chem. Soc., 2013, 135, 1167). Discuss the materials and processes that have led to the reduction of Li-ion battery costs over the last decade.