Novel Materials and Optimal Electrochemical Conditions for Enhancing Ecofriendly Aqueous Batteries
Aqueous batteries have garnered considerable interest in humanity’s quest for clean, sustainable energy solutions. Development of enhanced aqueous batteries with large capacity, rapid charging ability, and long life could potentially help realize our goal of carbon neutrality. Additional features of aqueous batteries such as low fabrication cost and high safety make them ideal candidates for research and development. However, there is a need to identify novel materials with suitable properties and optimal electrochemical conditions for realizing high performance aqueous batteries.
Recently, researchers led by Professor Masashi Okubo from Waseda University, Japan, have conducted a series of investigations to discover new materials with enhanced electrochemical features suitable for high power aqueous batteries.
First, they focused on layered vanadyl phosphate, one of the most-studied host materials for intercalation electrodes with organic electrolytes. This electrode has limited applications in aqueous lithium-ion systems because it dissolves in water. To address this, the research team innovatively controlled the water concentration using experimental analyses and ab initio calculations and discovered the ideal condition for stable, reversible operation of a layered vanadyl phosphate electrode in an aqueous lithium-ion electrolyte.
Next, the team demonstrated a novel aqueous proton battery, an attractive candidate for high-power energy storage devices. The small size of the proton and its ultrahigh mobility in water makes proton transfer ultrafast through the hydrogen-bonded networks of water molecules by means of the “Grotthuss mechanism.” The team identified similar continuous hydrogen bond networks in a novel dense oxide-ion array of solid alpha molybdenum oxide. The novelty of this discovery lies in the fact that these newly discovered networks enable anhydrous proton transport even in the absence of water. The researchers used a zinc anode and a super-concentrated zinc/hydrogen electrolyte and demonstrated the steady operation of an aqueous molybdenum oxide zinc proton battery with large capacity, long life, and fast charge–discharge abilities.
Finally, the researchers employed a high-salt-concentration strategy for aqueous electrolytes to enhance the electrochemistry of aqueous lithium-ion batteries. They evaluated the compatibility of conventional ruthenium-, nickel-, and manganese-based large-capacity lithium oxygen-redox cathodes with hydrate-melt electrolytes. Their findings suggest that stable progress of the oxygen redox reaction in concentrated aqueous electrolytes can only be achieved by avoiding the use of transition metals with high catalytic activity for the oxygen evolution reaction.
Taken together, the discoveries of advanced materials and ideal electrochemical conditions take us a step closer to realizing high-power aqueous batteries. This would facilitate a wide deployment of renewable energy in electricity supply to meet our ever-increasing energy demands. Further, the discoveries are major milestones in our quest for a sustainable, carbon-neutral society.
Link to the original journal articles:
https://pubs.rsc.org/en/content/articlelanding/2021/sc/d0sc04647g
https://onlinelibrary.wiley.com/doi/10.1002/adma.202203335
https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202104907
About the author
Dr. Masashi Okubo received his Ph.D. in coordination chemistry from the University of Tokyo in 2005. After serving as a postdoctoral fellow, an Assistant Professor, a senior researcher, and an Associate Professor at Université Pierre et Marie Curie, National Institute of Advanced Industrial Science and Technology, and the University of Tokyo for 16 years, he is currently a Professor in the Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering, at Waseda University. His research focuses on solid state chemistry and electrochemistry. He has authored over 120 research articles and garnered over 7600 citations till date.
