Alkoxy-functionalized ionic liquid electrolytes: understanding ionic coordination of calcium ion speciation for the rational design of calcium electrolytes
There is growing interest in the rational design of electrolytes for multivalent-ion batteries by tuning the molecular-level interactions of solvate species present in the electrolytes. Herein, we report our effort to control Ca-ion speciation in ionic liquid (IL) based electrolytes through the desi...
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Published in | Energy & environmental science Vol. 13; no. 8; pp. 2559 - 2569 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Cambridge
Royal Society of Chemistry
13.08.2020
|
Subjects | |
Online Access | Get full text |
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Summary: | There is growing interest in the rational design of electrolytes for multivalent-ion batteries by tuning the molecular-level interactions of solvate species present in the electrolytes. Herein, we report our effort to control Ca-ion speciation in ionic liquid (IL) based electrolytes through the design of alkoxy-functionalized cations. Quantitative analysis reveals that the alkoxy-functionalized ammonium cation (N
07
+
), bearing seven ether oxygen atoms, can effectively displace the bis(trifluoromethanesulfonyl)imide anion (TFSI
−
) from the Ca
2+
ion coordination sphere, facilitating the reversible Ca deposition/stripping process. More importantly, post-analysis of Ca deposits surface chemistry and density functional theory calculations of Ca-ion speciation indicate the formation of an organic-rich, but inorganic-poor solid electrolyte interphase layer, which enables Ca
2+
ion diffusion rather than passivating the Ca metal electrode. Finally, as a proof-of-concept, a prototype Ca/V
2
O
5
cell using the optimized IL-based electrolyte ([Ca(BH
4
)
2
]
0.05
[N
07
TFSI]
0.95
) is demonstrated for the first time, exhibiting a remarkable initial discharge capacity of 332 mA h g
−1
and reversible capacity of 244 mA h g
−1
.
The proof-of-concept demonstration of a rechargeable Ca/V
2
O
5
cell is given, taking advantage of an alkoxy-functionalized ionic liquid-based electrolyte enabling the displacement of the anions from the coordination of the Ca
2+
cations. |
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Bibliography: | 10.1039/d0ee00831a Electronic supplementary information (ESI) available. CCDC1991206. For ESI and crystallographic data in CIF or other electronic format see DOI |
ISSN: | 1754-5692 1754-5706 |
DOI: | 10.1039/d0ee00831a |