Engineering of an artificial solid electrolyte interphases on lithium for solid state lithium metal batteries


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Lithium metal batteries (LMBs) gain intensive interest as the most promising candidate for high energy battery systems besides lithium ion batteries (LIBs). Such interest does not only originates to the fact that LIBs is approaching a theoretical limit of its energy density but also in the combination of lithium metal electrode with solid electrolytes. However, poor cycling performance, low Coulombic efficiency (CE) and the uncontrollable dendrite growth during lithium electrodeposition and electrodissolution still remain as main challenges to be overcome ahead LMBs practical application. Yet, the solid electrolyte interphase (SEI) on lithium metal electrodes plays a great importance as it will not only determine the electrochemical performance of the LMB but will also play a key role in buffering the unwanted chemical reactions with the solid electrolytes.

The approach to design a uniform, stable and flexible artificial SEI (a-SEI) on the lithium metal electrode can passivate the Li-metal surface against parasitic reactions, regulate the ion transport at interfaces and lead to Li dendrite suppression. For example, in a recent study Liu and co-workers showed that a uniform coating of the lithium metal surface with lithium methyl carbonate (LMC) is able to protect the surface of the lithium metal electrode. Furthermore, such an approach also enhanced the current distribution and effectively suppressed the lithium dendrite formation during the electrodeposition and electrodissolution process.

In this study, we propose a rational design of the a-SEI, that not only meets the common requirements for the SEI to be permeable only for the Li-ions but also to homogeneously distribute the charge on the surface of such modified electrodes. Therefore, responsible for the “sieving” of the Li-ions, a single component organic layer is prepared on the surface of the lithium metal electrode. Such layer will also have the role to increase the chemical stability with the solid electrolytes. An enriched inorganic Li-intermetallic layer prepared a priori the organic layer will be responsible for stabilizing the overvoltages of the lithium electrodeposition and electrodissolution process and suppress the formation of high surface area lithium (HSAL).

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