Inner‐Shell Electron Transition for High‐Density Energy Storage

Comprehensive Summary The abundant quantities and strong binding energies of inner‐shell electrons (ISEs) make them an ideal energy storage medium to break through the energy density limitation of conventional batteries relying on the transfer of valence electrons. However, since the ISEs are strongly bound by the Coulomb potential of the nuclei, the production of highly charged ions through conventional chemical methods becomes unfeasible. Herein, by trapping the charged ions within an electric and magnetic field under vacuum, we present a new energy storage paradigm based on the ISE transition to overcome the fundamental limitations of batteries. Multiple ions, including highly charged barium and oxygen ions, generated via the electron impact ionization within a high‐density, magnetically confined electron beam, are utilized as a proof‐of‐concept. The integration of the photovoltaic module thus enables the efficient conversion of the potential energy into electrical power, which is validated by a series of experimental investigations, including electron beam current and trap voltage modulations. The resulting cell achieves stable current and voltage output with a high energy density of 1.5 × 10 4 Wh·kg –1 according to the ion population and mass.