Using NMR and computer simulations enables an understanding of how these unique electrolyte formulations improve lithium metal battery performance at the molecular level. These are tools to enable optimization of electrolyte design and enable stable lithium metal batteries.
The Columbia Engineering team is testing alkali metal additives that stop the formation of deleterious surface layers in combination with more traditional additives that encourage the growth of conductive layers on lithium metal. They are also actively using NMR to directly measure the rate of lithium transport through this layer.
Alkali metal additives improve Li metal batteries by tuning electrolyte decomposition
Post-mortem elemental analyses show that K+ additive is inert and does not deposit
Quantitative NMR analysis shows a thinner, less soluble SEI in the presence of K+
DFT calculations show clear differences in adsorption on Li metal between K+ and Li+
Engineering the solid electrolyte interphase (SEI) is a promising approach to improving Li metal battery performance. Recent work has shown that alkali metal additives can lead to smooth Li deposits, yet the underlying mechanisms are not understood. In this work, we demonstrate that alkali metal additives (here, K+) alter SEI composition, thickness, and solubility. Through post-mortem elemental analyses, we find that K+ ions do not deposit, but instead modify the reactivity of the electrode-electrolyte interface. Using quantitative nuclear magnetic resonance (NMR) and density functional theory (DFT), we show that K+ mitigates solvent decomposition at the Li metal surface. These findings suggest that alkali metal additives can be leveraged to suppress the formation of undesired SEI components (e.g., Li2CO3, soluble organic species), serving as an alternative approach for SEI modification compared to sacrificial additives. We believe that our work will spur further interest in the underexplored area of cation engineering.