Case Studies on Nonaqueous Zn2+ Ion Chemistry with a Reversible Intercalation Cathodes for the Development of Multivalent Metal Batteries
Authors: Han Sang-Don , Senguttuvan Premkumar , Tepavcevic Sanja , Rajput Nav Nidhi , Qu Xiaohui , Kim Soojeong , Yoo Hyun Deog , Lipson Albert L. , Wang Hao , Phillips Patrick J , Klie Robert F , Key Baris , Ingram Brian J. , Cabana Jordi , Fister Timothy T , Persson Kristin A , Markovic Nenad M , Johnson Christopher , Burrell Anthony K. , Vaughey John T. 
Published: February 2020

Recently, new energy storage chemistries based on nonaqueous electrolytes and multivalent metals (e.g., Mg, Zn, Ca and Al) have drawn the attention of the researchers as a promising advanced energy storage technology due to their higher theoretical volumetric capacity, limited dendrite formation and low cost.1 A major developmental need for these systems is the identification of electrolytes compatible with both electrodes while showing reversible deposition/dissolution on an anode and multivalent intercalation into a cathode.1,2 In the case of nonaqueous Mg or Ca ion-based systems, electrolyte compatibility issues (e.g., low Coulombic efficiency, a high overpotential and corrosion) have held back the development of Mg or Ca metal batteries.3 However, the nonaqueous Zn2+ ion chemistry utilized in a Zn metal cells with a reversible intercalation cathode is an exception with a number of promising features including highly-efficient reversible Zn deposition/dissolution on a Zn metal anode with a wide electrochemical window,3 similar ionic radius compared with Li+ and Mg2+ ions,4 relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)5 and high volumetric capacity.1 Considering these advantages, a nonaqueous Zn system provides an opportunity to delve into the mechanisms in multivalent-ion cell chemistry and solve the present issues in multivalent cell design and prototyping.3

In this study, the intercalation chemistry on a variety of cathodes materials (e.g., V2O5, Mn2O4 and FePO4) have been investigated in various nonaqueous Zn electrolytes. The electrochemical and transport properties of the electrolytes (e.g., reversible Zn deposition, anodic/cathodic stability, ionic conductivity and diffusion coefficient) were characterized utilizing the experimental and computational analysis.3 Among various Zn metal cells, a Zn/nanostructured bilayered V2O5 cell with a selected acetonitrile(AN)-Zn(TFSI)2 electrolyte demonstrates good reversibility and stability for 120+ cycles with nearly 100% Coulombic efficiency and ~170 mAhg-1 of gravimetric capacity, albeit operating at a cell voltage of 0.7 V vs. Zn/Zn2+.6 A Zn/nanostructured layered δ-MnO2 cell with an AN-Zn(TFSI)2 electrolyte also shows good reversibility (~100% Coulombic efficiency) and stability for 50+ cycles with ~100 mAhg-1 capacity with an operating voltage of 1.2 V vs. Zn/Zn2+.7 By utilizing a combination of analytical tools, we address numerous factors affecting capacity fade, and issues associated with the second phase formation including Mn dissolution in Zn/δ-MnO2 cells that have been extensively cycled.7

References

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