A stable, ionically-conductive solid electrolyte interphase (SEI) is vital to lithium (Li) metal anodes, yet key properties of common SEI phases remain unknown. Among these, Li2CO3, central to foundational SEI models, has been difficult to probe given its metastability on Li. To address this, we adopted two approaches: (i) synthesis and study of model Li2CO3-based SEI and (ii) cycling and titration-based analysis of SEI from Li–Cu cells with or without additive CO2, with the aim of modulating Li2CO3content natively. In (i), reductive instability of Li2CO3led to co-formation of Li2O and Li2C2in a multiphasic film with a Li+conductivity (∼8 × 10−9S cm−1) more than 4x higher than previously-measured Li2O or LiF films. Li2CO3content in native interphases from (ii) was found to correlate with decreased inactive Li0accumulation and improved Coulombic efficiency (CE) across diverse electrolytes having moderate CE. In high CE electrolytes, however, capacity losses become dominated by SEI formation rather than inactive Li0, and Li2CO3enrichment had negligible impact. This work updates understanding of SEI Li2CO3formed in modern electrolytes, reveals a leading mechanism by which Li2CO3can boost CE despite its metastability, and indicates the potential and limitations of enriching this phase through electrolyte design.
It has been widely suggested in literature that a lithium fluoride (LiF)-rich solid electrolyte interphase (SEI) affects Coulombic efficiency (CE) of the Li metal anode used with liquid electrolytes. Yet, the influence of LiF on Li metal deposition has been challenging to examine. Herein, we developed a method to synthesize LiF nanoscale particles with tunable sizes (30–300 nm) on Cu electrodes by electrochemical reduction of fluorinated gases under controlled discharge rates and capacities. The impact of LiF nanoparticles on overpotential and morphology of Li deposition was further studied in a conventional carbonate electrolyte. By cyclic voltammetry, Li plating overpotentials exhibit a clear correlation with the total surface area of LiF particles. Additionally, Li metal deposits (10
- PAR ID:
- 10376209
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 169
- Issue:
- 10
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 100523
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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