The development of aqueous zinc (Zn)-based rechargeable batteries is gaining momentum, driven by the inherently high theoretical capacity of Zn metal anodes, Zn abundance, low cost, simple processing, and safety of Zn. In addition, as the cathode material in aqueous Zn-ion batteries, manganese oxides offer advantages in terms of suitable output voltage, high theoretical capacity, low-cost, non-toxic, environmentally friendliness, and better cycle/rate performance. However, the specific energy of current Zn–MnO2 batteries remains unsatisfactory, lower than commercial Li-ion batteries.
Zinc sulfate (ZnSO4), chloride (ZnCl2), perchlorate (ZnClO4), and trifluoromethane sulfonate (Zn(OTF)2) are the commonly used electrolytes in aqueous zinc-ion batteries. While ZnCl2 and ZnClO4 are strongly acidic and corrosive, the alkaline nature of Zn(OTF)2 makes it more gentle with the anode, although it favors the growth of irreversibly discharged Mn(OH)2 at the cathode. On the other hand, ZnSO4 aqueous electrolytes have a weak acidic character that enables proton (H+) intercalation to contribute to the capacity. Besides, during the discharge, a precipitate protects the cathode surface and buffering the electrolyte pH.
In the recently published entitled “Improved Mn4+/Mn2+ Contribution in High-Voltage Zn–MnO2 Batteries Enabled by an Al3+-Ion Electrolyte” from Advanced Energy Materials, researchers reported a hybrid-ion Zn–MnO2 system with enhanced Mn4+/Mn2+ electrochemical contribution introducing aluminum sulfate (Al2(SO4)3) as electrolyte. Compared with conventional zinc electrolytes, the hybrid aluminum ion/zinc ion cell offers higher output voltage, as well as higher capacities, long cycle stability and outstanding energy densities.
This research was a collaborative effort, mainly led by IREC researchers from the Functional Nanomaterials Department (Xingqi Chang, Jesús Chacón-Borrero and Andreu Cabot) and the collaboration of Jian Shang (from the Low-Dimensional Energy Materials Research Center, in China) and the invaluable contributions from several researchers at the Catalonia Institute for Energy Research (IREC), in the Low-Dimensional Energy Materials Research Center (Chinese Academy of Sciences), in the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and in the Advanced Energy Storage Technology Research Center (Chinese Academy of Sciences).
Find more details in the publication: https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202402584
