Fig. 1: Towards the development of all-solid-state batteries.

a Evolution of global energy consumption during the past two centuries. The dashed arrow notes a surge in oil consumption in the 1970s. b Brief outline of batteries developed before the 1970s, including the primary Voltaic pile, primary Daniell cell, secondary lead-acid battery, secondary nickel–iron alkaline battery, and secondary nickel-cadmium battery²⁷. c Photographic picture of the first solid-state cell assembled in 1972, in which sodium metal and chromium oxide intercalated into graphite (CrO₃@graphite) were utilized as negative and positive electrode active materials, respectively. The solid-state sodium-ion conductor β-alumina was adopted as the electrolyte for supporting the operation of solid-state cell at room temperature (25 °C) with moderate stacking pressure (ca. 10 MPa). The crystal structures of sodium metal, CrO₃@graphite, and β-alumina are obtained from Materials Projects¹²⁰ and re-constructed with VESTA software¹²¹.