Aqueous Zinc-Chlorine Battery Modulated by a MnO Redox Adsorbent.

Aqueous zinc-chlorine battery with high discharge voltage and attractive theoretical energy density is expected to become an important technology for large-scale energy storage. However, the practical application of Zn-Cl batteries has been restricted due to the Cl cathode with sluggish kinetics and low Coulombic efficiency (CE). Here, an aqueous Zn-Cl battery using an inexpensive and effective MnO redox adsorbent (referred to Zn-Cl@MnO battery) to modulate the electrochemical performance of the Cl cathode is developed. Density functional theory calculations reveal that the existence of the intermediate state Cl free radical catalyzed by MnO on the Cl cathode contributes to the charge storage capacity, which is the key to modulate the electrode and improve the electrochemical performance. Further analysis of the Cl cathode kinetics discloses the adsorption and catalytic roles of the MnO redox adsorbent. The Zn-Cl@MnO battery displays an enhanced discharge voltage of 2.0 V at a current density of 2.5 mA cm, and stable 1000 cycles with an average CE of 91.6%, much superior to the conventional Zn-Cl battery with an average CE of only 66.8%. The regulation strategy to the Cl cathode provides opportunities for the future development of aqueous Zn-Cl batteries.