Charging-Mode-Resolved Energy-Storage Mechanisms in TiO₂/MoS₂‑Enabled Photorechargeable Zinc-Ion Batteries

Photorechargeable zinc-ion batteries (PR-ZIBs) offer an attractive route to integrate solar-energy harvesting with electrochemical storage; however, mechanistic understanding of how photogenerated charges are involved in the energy storage chemistry and how to rigorously quantify the photoelectric conversion efficiency remains incomplete. Herein, a heterojunction photoelectrode with TiO₂ nanowires/MoS₂ nanosheets in situ grown on the surface of carbon cloth (CC/TiO₂@MoS₂) was designed to enhance light absorption capacity and charge separation efficiency, thereby improving photoresponse performance and overall battery performance. By systematically benchmarking three charging protocols: conventional galvanostatic charging in the dark, light-assisted electrochemical charging, and light-only charging under an open-circuit-voltage (OCV) model, it is found that photogenerated carriers markedly promote Zn²⁺ deintercalation and increase the contribution of electric double-layer capacitance. Density functional theory (DFT) calculations corroborate light-enhanced ion kinetics, indicating a substantially reduced Zn²⁺ migration barrier across the TiO₂/MoS₂ interface and a lowered maximum barrier along the diffusion pathway. Moreover, synchronous voltage-time and current-time measurements further reveal that the apparent photovoltage recovery during OCV light-only charging occurs without external electron flow, originating instead from electrode/electrolyte interfacial processes. Accordingly, a self-charging-corrected OCV-based protocol is proposed to quantify the net photocharging energy-recovery efficiency. This approach effectively eliminates spurious signals introduced by intrinsic polarization, yielding an OCV-based conversion efficiency η_OCV of 2.13% for the CC/TiO₂/MoS₂ system. Overall, this work deepens the understanding of photogenerated carrier participation in Zn-ion storage and presents an innovative approach for evaluating photoelectric conversion efficiency, laying a foundation for the future development of high-performance light-assisted energy storage systems.