Interplays of Composition and Function in the Interphases of Metal Anodes for Li-ion Batteries and Beyond

The lithium (Li) metal anode offers significantly higher capacity than graphite and is therefore central to strategies to develop advanced rechargeable battery chemistries that meet range and performance targets for electric vehicles. Although closer than ever, Li anodes still cannot meet the >99.98% Coulombic efficiency (CE) needed for >1,000 cycle life. This shortfall arises from uncontrolled reactivity at the solid electrolyte interphase (SEI) and resulting SEI properties, leading to inhomogeneous plating and stripping, continuous electrolyte consumption and loss of active Li inventory. The lack of precise understanding of the SEI still hinders attempts to rationally design improved interphases, and the electrolytes that build them, towards bridging remaining gaps in CE.

To inform such efforts, our work is advancing quantitative techniques to yield insights into SEI phases and the hidden interplays between their chemistry, properties and function. Most recently, this involves development of analytical tools for cycled electrodes that sensitively report on SEI composition, providing insight beyond what is possible with typical post mortem characterization methods. By applying these tools to native interphases spanning high and low CE, we are identifying effective compositional and performance descriptors for high performance. I will describe our broader efforts towards SEI- and thermodynamics-driven electrolyte design that seeks to sensitively link the coordination environment of Li+ to resulting interphase properties.

Finally, I will share some perspectives on comparisons and unique challenges for beyond-Li chemistries including sodium and calcium metal batteries and their electrolytes, with distinct interphase properties and requirements.