Photo‐assisted chemical self‐rechargeable zinc ion batteries with high charging and discharging efficiency

Abstract Chemical self‐recharging zinc ion batteries (ZIBs), which are capable of auto‐recharging in ambient air, are promising in self‐powered battery systems. Nevertheless, the exclusive reliance on chemical energy from oxygen for ZIBs charging often would bring some obstacles in charging efficiency. Herein, we develop photo‐assisted chemical self‐recharging aqueous ZIBs with a heterojunction of MoS 2 /SnO 2 cathode, which are favorable to enhancing both the charging and discharging efficiency as well as the chemical self‐charging capabilities under illumination. The photo‐assisted process promotes the electron transfer from MoS 2 /SnO 2 to oxygen, accelerating the occurrence of the oxidation reaction during chemical self‐charging. Furthermore, the electrons within the MoS 2 /SnO 2 cathode exhibit a low transfer impedance under illumination, which is beneficial to reducing the migration barrier of Zn 2+ within the cathode and thereby facilitating the uniform inserting of Zn 2+ into MoS 2 /SnO 2 cathode during discharging. This photo‐assisted chemical self‐recharging mechanism enables ZIBs to attain a maximum self‐charging potential of 0.95 V within 3 hours, a considerable self‐charging capacity of 202.5 mAh g −1 and excellent cycling performance in a self‐charging mode. This work not only provides a route for optimizing chemical self‐charging energy storage, but also broadens the potential application of aqueous ZIBs.