A Photoresponsive Battery Based on a Redox-Coupled Covalent-Organic-Framework Hybrid Photoelectrochemical Cathode

Photoresponsive batteries promise flexible and low-cost solar-to-electrochemical energy storage (SES), but suffer from a limited SES efficiency due to rapid charge recombination and sluggish redox. Here, we present a porous-shell/core hybrid of covalent organic framework@carbon nanotube. This hybrid ensures long-lived separated charges (τ_ave =3.0 ns) by an electron transfer relay starting from the donor-acceptor molecules to the nanoscale heterojunction. These charges are further allowed to drive high-rate redox of -C=O/-C-O^- and -C-N/-C=N⁺ with facile kinetics. Equipped with this photoelectrochemical cathode, a photoresponsive aqueous battery shows a 5-fold enhancement in SES efficiency (1.1 % at 1 sun) over their counterparts. It is unveiled that the electron relay favors the formation of electron-enriching -C-O- and hole-enriching -C=N⁺ groups responsible for photoelectrochemical Zn²⁺ and OTf^- storage cascade; and further, the general photo coupled ions transfer (PCIT) process is proposed. This work presents an inspiring photoelectrochemical cathode design and theoretical insight for photoresponsive batteries.