Photogenerated Holes Induced Deep Sodium Storage of TiO ₂ /CdSe/NFPP Cathode for High‐Efficiency Photorechargeable Sodium Batteries

Abstract

Abstract Resource‐friendly photorechargeable sodium batteries (PRSBs) integrate energy storage devices with solar cells, offering a promising path for sustainable energy. Herein, a novel TiO 2 /CdSe/Na 3 Fe 2 (PO 4 )P 2 O 7 (NFPP) cathode was prepared layer‐by‐layer utilizing resource‐abundant commercialized NFPP and photoactive CdSe. The aligned energy levels with type II band structure ensure effective transfer of photogenerated 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 Fe 2+ to Fe 3+ 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, photogenerated holes could regulate surface charge distribution on NFPP and thus form a film‐forming agent fluoroethylene carbonate (FEC)‐dominated electric double layer. Finally, it converts 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 compared to dark conditions.