Photo‐Generated Holes Induced Deep Sodium Storage of TiO2/CdSe/NFPP Cathode for High‐Efficiency Photo‐Rechargeable Sodium Batteries

Resource‐friendly photo‐rechargeable sodium batteries (PRSBs) integrate energy storage devices with solar cells offering a promising path for sustainable energy. Herein, a novel TiO2/CdSe/Na3Fe2(PO4)P2O7 (NFPP) cathode was prepared layer‐by‐layer utilizing resource‐abundant commercialized NFPP and photoactive CdSe. The aligned energy levels with type II band structure ensures effective transfer of photo‐generated holes from CdSe (‐5.71 eV) to higher valence band of NFPP (‐5.10 eV). Experimental results reveal that, during charging, the induced holes in NFPP accelerate the transition of Fe2+ to Fe3+ with a change of O‐Fe hybrid orbitals. The calculations of bond valence sum and energy distribution reveal that NFPP‐holes possesses broad Na+ transport path with reduced transport barrier (from 0.512 to 0.428 eV), improving Na+ extraction efficiency. Additionally, photo‐generated holes could regulate surface charge distribution on NFPP and thus form a film‐forming agent fluoroethylene carbonate (FEC)‐dominated electric double layer. Finally, it converting to a thinner (9.75 nm‐illumination) NaF‐rich cathode interphase layer, avoiding subsequent excessive electrolyte decomposition. As a result, the NFPP under illumination delivers high capacity of 119.1 mAh g‐1 at 1 C, showing 41.11% improvement comparing to dark conditions.