Suppressing Hydrogen Evolution via Anticatalytic Interfaces toward Highly Efficient Aqueous Zn-Ion Batteries.

Aqueous Zn-ion batteries hold practical promise for large-scale energy storage because of the safety and affordability of aqueous-based electrolytes; in addition, the manufacturing process is significantly simplified by direct employment of Zn metal as an anode. However, hydrogen evolution due to near-surface water dissociation has hindered large-scale applications of them. Here, we report the suppression of the hydrogen evolution reaction via a CuN3-coordinated graphitic carbonitride (CuN3-C3N4) anticatalytic interface to achieve highly efficient aqueous Zn-ion batteries. Based on in situ gas chromatography and in situ synchrotron-based X-ray diffraction spectroscopy, we demonstrated that the hydrogen evolution reaction triggers the Zn4SO4(OH)6·xH2O formation. A combination of in situ infrared spectroscopy and density functional theory simulations has proved to stabilize near-surface H3O+ species and regulate adsorption of H* intermediates by an anticatalytic interface for hydrogen evolution reaction suppression. Consequently, the anticatalytic interface greatly improves the Coulombic efficiency of Zn plating/stripping to ∼99.7% for 5500 cycles and the cycling reversibility to over 1300 h at 1 mA cm-2 and 1 mAh cm-2. With an anticatalytic interface, the full cell shows an excellent Coulombic efficiency of 98.3% over 400 cycles at 1C. These findings provide strategic insight for targeted designing of highly efficient aqueous Zn-ion batteries.

Conversion-Type Nonmetal Elemental Tellurium Anode with High Utilization for Mild/Alkaline Zinc Batteries.

Zinc ion batteries (ZIBs), generally established on an excessive metallic Zn anode and aqueous electrolytes, suffer from severe dendrites and gassing issues at Zn side, resulting in poor cycling life. Substituting Zn metal anode with non-Zn ones is a promising strategy for solving these problems, whereas this is still restricted by the limited anode alternatives. Herein, by replacing metal Zn with chalcogen element tellurium (Te), a conversion-type Te-based ZIB is reported that can work in both mild and alkaline electrolytes. As expected, the as-assembled mild Te/MnO2 and alkaline Te/Ni(OH)2 cells deliver remarkable capacities up to 106 and 161 mAh g-1 anode+cathode , respectively, with a high utilization of anode (50.1% for the Te/MnO2 and 38.9% for the Te/Ni(OH)2 ), which surpass all ZIBs. Ultralong cycling life (over 75% capacity retention after 5000 cycles) is achieved in the two systems, benefiting from the stable conversion mechanisms (mild: Te to ZnTe2 to ZnTe; alkaline: ZnTe to Te to TeO2 ) with thoroughly eliminated dendrites and gassing. Moreover, high gravimetric energy density of ZIBs is also achieved, which are 176.3 Wh kg-1 anode+cathdoe (Te/Ni(OH)2 ) and 81 Wh Kg-1 anode+cathode (Te/MnO2 ), respectively. This work sheds light on the development of advanced conversion-type anode for high-performance batteries with superior stability.

Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies.

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed.