Stabilizing Li-Metal Anodes via Ion Rectification

Li metal batteries (LMBs) have garnered considerable attention as a promising alternative to commercial Li-ion batteries (LIBs) owing to the high theoretical capacity (3860 mAh g-1) and low electrode potential of Li metal anodes (-3.04 V vs. standard hydrogen electrode. However, the poor Li plating/stripping cyclability, uneven Li dendrites growth, formation of unstable solid-electrolyte interphase (SEI) layers, and generation of electrically inactive “dead Li”, have plagued the practical application of LMBs. These challenges have forced the use of thick Li metal electrodes (> 100 µm) with low utilization (< 10 %), resulting in serious losses of cell energy density. Several works, including the electrolyte design, solid-state electrolytes, artificial SEI layers, and 3D-structured Li hosts, have been implemented to address the aforementioned challenges. This talk describes new material chemistry and architectural strategies for stabilizing Li-metal anodes, with focus on ion rectification and ion flux toward Li-metal anodes. In contrast to conventional dual-ion conductors (e.g., a mixture of organic solvents (or polymer matrices) and lithium salts), single-ion conductors featuring the ion rectification capability do not allow freely movable anions which could often trigger unwanted side reactions with electrodes and charge polarization, thus providing improvements in the electrode-electrolyte stability and electrochemical sustainability of cells. In addition to the ion rectification effect of the electrolytes, well-defined nanoporous structure of protective layers and hosts allow facile and uniform ion flux toward Li metal electrodes, thereby adjusting tortuous paths of dendrite growth without hampering ion transport. Our approaches presented herein include the regulation of ion coordination of electrolytes, synthesis of single-ion conductors with directional 1D channels, and structural design of ordered nanoporous protective layers and electroactive hosts based on microgrid-patterned Si anodes.

References

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2. Sang-Young Lee et al., “Enabling sustainable lithium metal electrodes via cholesteric liquid crystalline cellulose nanocrystal nanomembranes”, Adv. Energy. Mater. 2022, 2200799.
3. Sang-Young Lee et al., “Microgrid-patterned silicon electrode as an electroactive lithium host”, Energy Environ. Sci. 2022, 15, 2581.