Understanding the Nature of Solid‐Electrolyte Interphase on Lithium Metal in Liquid Electrolytes: A Review on Growth, Properties, and Application‐Related Challenges

Abstract

A stable solid‐electrolyte interphase (SEI) is of crucial essence for realization of lithium (Li) metal batteries. This article provides an overview of attempts undertaken to understand the nature of the natural SEI, including growth behavior at the open circuit potential and under cycling conditions as well as underlying causes of instabilities. Additionally, the influence of features such as morphology and composition of the SEI and electrolyte properties on the charge transport and transfer mechanism, resulting in distinct growth behavior and overall stability, is elaborated. Finally, it will be discussed how already at the fundamental stage of research, it is crucial to take into account the implications that progressing from coin‐cell level to more realistic cell and cycling conditions has on SEI properties and stability.

Suitable Salt for Solid Electrolyte Interphase Formation in Al Anode Dual-Ion Battery

“…On one hand, SEI formation requires the decomposition of various electrolyte components, a robust SEI once formed restricts further direct contact between the electrode and electrolyte thereby obstructing further electrolyte decomposition which can positively contribute to the longevity of the battery . In various reports, it has been proposed that an inorganic-rich SEI layer is recommended as it is robust and stops dendrite formation. , The organic rich SEI on the other hand leads to low ionic conductivity in the battery . Among the considered salts (LiPF 6 , LiBF 4 , and LiTFSI) in our study, LiBF 4 is found to have the least tendency to participate in SEI formation.…”

“…14 In various reports, it has been proposed that an inorganic-rich SEI layer is recommended as it is robust and stops dendrite formation. 46,47 The organic rich SEI on the other hand leads to low ionic conductivity in the battery. 21 Among the considered salts (LiPF 6 , LiBF 4 , and LiTFSI) in our study, LiBF 4 is found to have the least tendency to participate in SEI formation.…”

Ion transport and growth behavior of solid electrolyte interphases on Li and Na with liquid electrolytes based on impedance analysis

“…[12][13][14] The experimental difficulties of SEI studies include air-sensitivity and the inherently complex and fragile SEI morphology composed of many chemical compounds with variable mechanical properties and sometimes non-negligible amount of pores. [15][16][17][18][19][20][21][22][23] The above mentioned problems pose even greater challenges for the studies of SEIs on the reactive Li/Na metals, currently considered to be the attractive anode materials for future-generation batteries. [24][25][26][27][28] Although novel experimental strategies such as cryo-transmission electron microscopy (TEM), [29][30][31][32] X-ray-based analytical tools [33][34][35] and nuclear magnetic resonance (NMR) spectroscopy have been recently applied in SEI research, 32,[36][37][38][39][40] EIS offers particular advantages, as it enables us to distinguish between different electrochemical transport processes in situ and in a non-destructive way.…”

Molecular/Ionic Designs in the Electrolyte and Interphases for Lithium Metal Anode

“…The SEI generated in traditional carbonate electrolytes is composed primarily of Li 2 CO 3 , Li 2 O, and Li alky carbonate (mosaic model, Figure 1e). [12,15,17,32] These components would not satisfy the demand of homogeneity, rapid ion transport, and mechanical strength (Figure 1f), which are needed to achieve high reversibility of Li metal anode [29,33–35] . Recent studies have shown that many inorganic molecules (LiF, Li 3 N, Li 2 S, etc.)…”