Aqueous Zinc-Chlorine Battery Modulated by a MnO 2 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 2 batteries has been restricted due to the Cl 2 cathode with sluggish kinetics and low Coulombic efficiency (CE). Here, an aqueous Zn-Cl 2 battery using an inexpensive and effective MnO 2 redox adsorbent (referred to Zn-Cl 2 @MnO 2 battery) to modulate the electrochemical performance of the Cl 2 cathode is developed. Density functional theory calculations reveal that the existence of the intermediate state Cl ads free radical catalyzed by MnO 2 on the Cl 2 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 2 cathode kinetics discloses the adsorption and catalytic roles of the MnO 2 redox adsorbent. The Zn-Cl 2 @MnO 2 battery displays an enhanced discharge voltage of 2.0 V at a current density of 2.5 mA cm -2 , and stable 1000 cycles with an average CE of 91.6%, much superior to the conventional Zn-Cl 2 battery with an average CE of only 66.8%. The regulation strategy to the Cl 2 cathode provides opportunities for the future development of aqueous Zn-Cl 2 batteries.