Revealing the Thermodynamics of Magnesium and Lithium Ion Insertion Chemistry in Ultrafast Discharging Hybrid Rechargeable Batteries

Tuesday, 26 May 2015: 15:40
Salon A-3 (Hilton Chicago)
M. Aykol, S. Kim (Northwestern University), J. H. Cho (Korea Institute of Science and Technology, Yonsei University), J. H. Ha, K. Y. Chung (Korea Institute of Science and Technology), K. B. Kim (Yonsei University), B. W. Cho (Korea Institute of Science and Technology), and C. Wolverton (Northwestern University)
We present a combined experimental and theoretical strategy to design dual-salt Mg2+/Li+ batteries with very high electrochemical performance.[1] In this work, we first investigate the (co)-insertion mechanisms of Mg2+ and Li+ ions into the Mo6S8 cathode by using density functional theory (DFT) calculations together with the Nernst relation. We show that there exists a threshold for the Li+ activity in the electrolyte above which lithiation is preferred instead of magnesiation. Based on the DFT results, to achieve high electrochemical performance, we suggest an approach to control the insertion chemistry by varying the Li salt content of the electrolyte. Using this approach, we have carefully revealed the ion insertion chemistry for the Mg-metal anode/Mo6S8cathode hybrid Mg/Li batteries with all-phenyl complex (APC) and LiCl electrolytes.

Our experimental results confirm that at low Li+ activities in the electrolyte, Mg2+ insertion dominates and the battery can cycle only below 80 mAh g-1, whereas at high Li+ activities, fast Liionic transport in the entire intercalation range leads to higher voltage, capacity and rate capability. We find that the Mg/Li hybrid rechargeable battery with an APC 0.2 M and LiCl 0.5 M dual-salt electrolyte has a remarkable electrochemical performance. This hybrid battery with optimized insertion chemistry achieves 93.6% capacity retention at 20 C and 87.5% at 30 C at room temperature. Our combined computational and experimental study suggests an effective route to develop new dual-salt hybrid systems with controlled insertion chemistry.


This work has been supported by The Dow Chemical Company and Northwestern-Argonne Institute of Science and Engineering (NAISE).


[1] J.-H. Cho, M. Aykol, S. Kim, J.-H. Ha, C. Wolverton, K. Y. Chung, K.-B. Kim, and B. -W. Cho, J. Am. Chem. Soc. 2014, 136, 16116.