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LiTDI: A Highly Efficient Additive for Electrolyte Stabilization in Lithium-Ion Batteries
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2017 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 5, 2254-2263 p.Article in journal (Refereed) Published
Abstract [en]

The poor stability of LiPF6-based electrolytes has always been a bottleneck for conventional lithium-ion batteries. The presence of inevitable trace amounts of moisture and the operation of batteries at elevated temperatures are particularly detrimental to electrolyte stability. Here, lithium 2trifluoromethy1-4,5-dicyanoimidazole (LiTDI) is investigated as a moisture-scavenging electrolyte additive and can sufficiently suppress the hydrolysis of LiPF6. With 2 wt % LiTDI, no LiPF6 degradation can be detected after storage for 35 days, even though the water level in the electrolyte is enriched by 2000 ppm. An improved thermal stability is also obtained by employing the LiTDI additive, and the moisture-scavenging mechanism is discussed. The beneficial effects of the LiTDI additive on battery performance are demonstrated by the enhanced capacity retention of both the LiNi1/3Mn1/3Co1/3O2 (NMC)/Li and NMC/graphite cells at 55 degrees C. In particular, the increase in cell voltage hysteresis is greatly hindered when LiTDI is presented in the electrolyte. Further development of the LiTDI additive may allow the improvement of elevated-temperature batteries, as well as energy savings by reducing the amount of effort necessary for dehydration of battery components.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC , 2017. Vol. 29, no 5, 2254-2263 p.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-319530DOI: 10.1021/acs.chemmater.6b05247ISI: 000396639400040OAI: oai:DiVA.org:uu-319530DiVA: diva2:1087292
Funder
Swedish Energy Agency, 34191-1 39036-1Swedish Foundation for Strategic Research Carl Tryggers foundation
Available from: 2017-04-06 Created: 2017-04-06 Last updated: 2017-04-26Bibliographically approved
In thesis
1. Non-aqueous Electrolytes and Interfacial Chemistry in Lithium-ion Batteries
Open this publication in new window or tab >>Non-aqueous Electrolytes and Interfacial Chemistry in Lithium-ion Batteries
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lithium-ion battery (LIB) technology is currently the most promising candidate for power sources in applications such as portable electronics and electric vehicles. In today's state-of-the-art LIBs, non-aqueous electrolytes are the most widely used family of electrolytes. In the present thesis work, efforts are devoted to improve the conventional LiPF6-based electrolytes with additives, as well as to develop alternative lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI)-based electrolytes for silicon anodes. In addition, electrode/electrolyte interfacial chemistries in such battery systems are extensively investigated.

Two additives, LiTDI and fluoroethylene carbonate (FEC), are evaluated individually for conventional LiPF6-based electrolytes combined with various electrode materials. Introduction of each of the two additives leads to improved battery performance, although the underlying mechanisms are rather different. The LiTDI additive is able to scavenge moisture in the electrolyte, and as a result, enhance the chemical stability of LiPF6-based electrolytes even at extreme conditions such as storage under high moisture content and at elevated temperatures. In addition, it is demonstrated that LiTDI significantly influences the electrode/electrolyte interfaces in NMC/Li and NMC/graphite cells. On the other hand, FEC promotes electrode/electrolyte interfacial stability via formation of a stable solid electrolyte interphase (SEI) layer, which consists of FEC-derivatives such as LiF and polycarbonates in particular.

Moreover, LiTDI-based electrolytes are developed as an alternative to LiPF6 electrolytes for silicon anodes. Due to severe salt and solvent degradation, silicon anodes with the LiTDI-baseline electrolyte showed rather poor electrochemical performance. However, with the SEI-forming additives of FEC and VC, the cycling performance of such battery system is greatly improved, owing to a stabilized electrode/electrolyte interface.

This thesis work highlights that cooperation of appropriate electrolyte additives is an effective yet simple approach to enhance battery performance, and in addition, that the interfacial chemistries are of particular importance to deeply understand battery behavior.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 72 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1525
Keyword
Lithium-ion batteries, electrolyte, electrolyte additives, electrochemistry, interfacial chemistry
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-319425 (URN)978-91-554-9931-0 (ISBN)
Public defence
2017-06-14, Room 2005, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 34191-1
Available from: 2017-05-23 Created: 2017-04-26 Last updated: 2017-06-08

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