Correlating Electronic Transition With Electrical Output to Reveal Photon-Mediated Energy Conversion Mechanism in Inner-Shell Electron Battery.

Inner-shell electron batteries present a promising route to ultrahigh-density energy storage by harnessing the potential energy confined within inner-shell orbitals. While prior efforts have demonstrated the conversion of potential energy into electricity with photovoltaic (PV) modules, a direct correlation between inner-shell electron transition and the resulting electrical output remains obscured by interfering photons. Here, by integrating systematic theoretical analysis of electron transition behaviors with a narrowband-filter-based experimental setup, we demonstrate a photon-mediated energy-conversion framework, exemplified by Mo15+ (370.81 nm), Mo16+ (370.85 nm), and La19+ (371.96 nm) as highly charged ions (HCIs) selected near the peak efficiency wavelength of the PV module, which directly correlates specific electronic transition with power output. After filtering out unrelated wavelengths, we achieve a current response of 2.3 × 10-12 C by capturing 7 × 107 photons emitted from 1 × 106 La19+ ions. Furthermore, the replacement of the narrowband filter (365-375 nm) with an infrared filter to collect all emitted photons from HCIs yields an energy density of 1 × 104 Wh kg-1 based on the mass of 1 × 106 La19+ ions, thereby holding great promise for future ultrahigh-density energy storage applications.