The practical application of lithium (Li) metal anode (LMA) is still hindered by non‐uniformity of solid electrolyte interphase (SEI), formation of “dead” Li, and continuous consumption of electrolyte although LMA has an ultrahigh theoretical specific capacity and a very low electrochemical redox potential. Herein, a facile protection strategy is reported for LMA using a double layer (DL) coating that consists of a polyethylene oxide (PEO)‐based bottom layer that is highly stable with LMA and promotes uniform ion flux, and a cross‐linked polymer‐based top layer that prevents solvation of PEO layer in electrolytes. Li deposited on DL‐coated Li (DL@Li) exhibits a smoother surface and much larger size than that deposited on bare Li. The LiF/Li2O enriched SEI layer generated by the salt decomposition on top of DL@Li further suppresses the side reactions between Li and electrolyte. Driven by the abovementioned advantageous features, the DL@Li||LiNi0.6Mn0.2Co0.2O2cells demonstrate capacity retention of 92.4% after 220 cycles at a current density of 2.1 mA cm–2(C/2 rate) and stability at a high charging current density of 6.9 mA cm–2(1.5 C rate). These results indicate that the DL protection is promising to overcome the rate limitation of LMAs and high energy‐density Li metal batteries.
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.
more » « less- PAR ID:
- 10535129
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 171
- Issue:
- 8
- ISSN:
- 0013-4651
- Format(s):
- Medium: X Size: Article No. 080530
- Size(s):
- Article No. 080530
- Sponsoring Org:
- National Science Foundation
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