Decoupling light-assisted and pure-light charging mechanisms in TiO2-based photorechargeable Li-ion batteries

The integration of photocatalysis with electrochemical energy storage offers promising solutions for off-grid power supply. Herein, carbon cloth-supported TiO₂ nanorod arrays are engineered as a model platform to explore photoelectrochemical synergy in integrated photo-rechargeable lithium-ion batteries (PRLiBs). Through operando characterizations and theory calculations, we found that photoexcitation lowers the Li⁺ migration barrier by 0.16 eV through electronic states redistribution near the Fermi level, thereby accelerating Li⁺ transport and enhancing the intercalation process during photo-assisted charging and discharging. Three key principles governing dual operational modes (light-assisted charge/discharge and pure light charging) are established for PRLiBs: (i) the capacity enhancement during photo-assisted charging is primarily due to photocatalytic Li⁺ extraction via hole-driven oxidation at the TiO₂/electrolyte interface and electric double-layer reconstruction; (ii) the long-standing controversy in solar-to-electricity conversion efficiency (η) is resolved by introducing a polarization-decoupled model to quantify η, distinguishing genuine catalytic contributions from parasitic self-charging effects; and (iii) during light-only charging without external bias, the capacity increase is predominantly driven by the photocatalytic oxidation of the TiO₂ photoelectrode, a single-electrode process without electron transfer through an external circuit, distinct from conventional dual-electrode charging. This work lays a solid theoretical foundation for understanding the mechanisms of PRLiBs and provides precise guidelines for η calculations, offering valuable insights for the future development of photo-energy storage devices.