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Quantifying mass transport during polarization in a Li Ion battery electrolyte by in situ 7Li NMR imaging
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.ORCID iD: 0000-0003-4901-5820
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
Show others and affiliations
2012 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 36, 14654-14657 p.Article in journal (Refereed) Published
Abstract [en]

Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ 7Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li + transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.

Place, publisher, year, edition, pages
2012. Vol. 134, no 36, 14654-14657 p.
Keyword [en]
Electrolytes, Magnetic resonance imaging, Transport properties
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-103644DOI: 10.1021/ja305461jISI: 000308574800006Scopus ID: 2-s2.0-84866398560OAI: oai:DiVA.org:kth-103644DiVA: diva2:561317
Funder
Swedish Research CouncilStandUp
Note

QC 20150624

Available from: 2012-10-18 Created: 2012-10-17 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Electrochemical Studies of Aging in Lithium-Ion Batteries
Open this publication in new window or tab >>Electrochemical Studies of Aging in Lithium-Ion Batteries
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lithium-ion batteries are today finding use in automobiles aiming at reducing fuel consumption and emissions within transportation. The requirements on batteries used in vehicles are high regarding performance and lifetime, and a better understanding of the interior processes that dictate energy and power capabilities is a key to strategic development. This thesis concerns aging in lithium-ion cells using electrochemical tools to characterize electrode and electrolyte properties that affect performance and performance loss in the cells.

 

A central difficulty regarding battery aging is to manage the coupled effects of temperature and cycling conditions on the various degradation processes that determine the lifetime of a cell. In this thesis, post-mortem analyses on harvested electrode samples from small pouch cells and larger cylindrical cells aged under different conditions form the basis of aging evaluation. The characterization is focused on electrochemical impedance spectroscopy (EIS) measurements and physics-based EIS modeling supported by several material characterization techniques to investigate degradation in terms of properties that directly affect performance. The results suggest that increased temperature alter electrode degradation and limitations relate in several cases to electrolyte transport. Variations in electrode properties sampled from different locations in the cylindrical cells show that temperature and current distributions from cycling cause uneven material utilization and aging, in several dimensions. The correlation between cell performance and localized utilization/degradation is an important aspect in meeting the challenges of battery aging in vehicle applications.

 

The use of in-situ nuclear magnetic resonance (NMR) imaging to directly capture the development of concentration gradients in a battery electrolyte during operation is successfully demonstrated. The salt diffusion coefficient and transport number for a sample electrolyte are obtained from Li+ concentration profiles using a physics-based mass-transport model. The method allows visualization of performance limitations and can be a useful tool in the study of electrochemical systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. x, 72 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:16
Keyword
aging, EIS modeling, electrolyte characterization, graphite, hybrid electric vehicles, impedance spectroscopy, LiFePO4, Li-ion batteries
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-145057 (URN)978-91-7595-116-4 (ISBN)
Public defence
2014-05-28, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Note

QC 20140512

Available from: 2014-05-12 Created: 2014-05-07 Last updated: 2017-02-22Bibliographically approved
2. Characterizing ions in solution by NMR methods
Open this publication in new window or tab >>Characterizing ions in solution by NMR methods
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution.  Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association.

The effective charge of the tetramethylammonium cation ion in water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol was estimated by eNMR and diffusion measurements and compared to the value predicted by the Debye-Hückel-Onsager limiting law. The difference between the predicted and measured effective charge was attributed to ion pairing which was found to be especially significant in ethanol.

The association of a large set of cations to polyethylene oxide (PEO) in methanol, through the ion-dipole interaction, was quantified by eNMR. The trends found were in good agreement with the scarce data from other methods. Significant association was found for cations that have a surface charge density below a critical value. For short PEO chains, the charge per monomer was found to be significantly higher than for longer PEO chains when binding to the same cations. This was attributed to the high entropy cost required to rearrange a long chain in order to optimize the ion-dipole interactions with the cations. Moreover, it was suggested that short PEO chains may exhibit distinct binding modes in the presence of different cations, as supported by diffusion measurements, relaxation measurements and chemical shift data.

The protonation state of a uranium (VI)-adenosine monophosphate (AMP) complex in aqueous solution was measured by eNMR in the alkaline pH range. The question whether or not specific oxygens in the ligand were protonated was resolved by considering the possible association of other species present in the solution to the complex.

The methodology of eNMR was developed through the introduction of a new pulse-sequence which suppresses artifactual flow effects in highly conductive samples.

In another experimental setup, using NMR imaging, a constant current was applied to a lithium ion (Li ion) battery model. Here, 7Li spin-echo imaging was used to probe the spin density in the electrolyte and thus visualize the development of Li+ concentration gradients. The Li+ transport number and salt diffusivity were obtained within an electrochemical transport model. The parameters obtained were in good agreement with data for similar electrolytes. The use of an alternative imaging method based on CTI (Constant Time Imaging) was explored and implemented.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xii, 58 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:29
Keyword
electrophoretic NMR, diffusion NMR, NMR imaging, ion pairing, ion association, polyethylene oxide, metal-ion complex, Li ion batteries, electrolyte characterization
National Category
Natural Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-149552 (URN)978-91-7595-208-6 (ISBN)
Public defence
2014-09-12, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20140825

Available from: 2014-08-25 Created: 2014-08-22 Last updated: 2014-08-25Bibliographically approved

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Klett, MatildaWreland Lindström, RakelLindbergh, GöranFuró, Istvan

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