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Functional binders as graphite exfoliation suppressants in aggressive electrolytes for 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.
2015 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 175, 141-150 p.Article in journal (Refereed) Published
Abstract [en]

A comparative study of various electrode binders for graphite electrodes was conducted in a carbonate-based electrolyte with a high content of propylene carbonate (PC) as a means to evaluate anode degradation in presence of different binders. Because of its direct contact with the active material, a binder can be interpreted as an interfacial layer and as a local part of the electrolyte, the properties of which greatly depend on the interaction with the liquid electrolyte. In this work we demonstrate how a carefully chosen binder can create a specific surface environment that can protect graphite from exfoliation when the binder exhibits poor solubility in the electrolyte solvent and good surface adhesion to the active material. The exceptional stability of graphite electrodes containing poly(acrylic acid) sodium salt (PAA-Na) and carboxymethyl cellulose sodium salt (CMC-Na), respectively, in a PC-rich electrolyte is explained through the understanding of binder swelling and functionality. Interfacial resistances and electrochemical stability were investigated with impedance spectroscopy and galvanostatic cycling. Electrode morphologies and distributions of material were analysed with SEM and EDX. Evidence is presented that the surface selectivity increases with concentration of functional groups and polymer flexibility. Therefore only the less selective, stiff polymer with less functional groups, CMC-Na, provides sufficient protection at low binder contents.

Place, publisher, year, edition, pages
2015. Vol. 175, 141-150 p.
Keyword [en]
Binder, graphite exfoliation, CMC, propylene carbonate, SEI
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-262960DOI: 10.1016/j.electacta.2015.03.072ISI: 000360178600019OAI: oai:DiVA.org:uu-262960DiVA: diva2:857519
Swedish Research Council, 2012-3837
Available from: 2015-09-29 Created: 2015-09-23 Last updated: 2015-11-26Bibliographically approved
In thesis
1. Functional Binders at the Interface of Negative and Positive Electrodes in Lithium Batteries
Open this publication in new window or tab >>Functional Binders at the Interface of Negative and Positive Electrodes in Lithium Batteries
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, electrode binders as vital components in the fabrication of composite electrodes for lithium-ion (LIB) and lithium-sulfur batteries (LiSB) have been investigated.

Poly(vinylidene difluoride) (PVdF) was studied as binder for sulfur-carbon positive electrodes by a combination of galvanostatic cycling and nitrogen absorption. Poor binder swelling in the electrolyte and pore blocking in the porous carbon were identified as origins of low discharge capacity, rendering PVdF-based binders an unsuitable choice for LiSBs. More promising candidates are blends of poly(ethylene oxide) (PEO) and poly(N-vinylpyrrolidone) (PVP). It was found that these polymers interact with soluble lithium polysulfide intermediates generated during the cell reaction. They can increase the discharge capacity, while simultaneously improving the capacity retention and reducing the self-discharge of the LiSB. In conclusion, these binders improve the local electrolyte environment at the electrode interface.

Graphite electrodes for LIBs are rendered considerably more stable in ‘aggressive’ electrolytes (a propylene carbonate rich formulation and an ether-based electrolyte) with the poorly swellable binders poly(sodium acrylate) (PAA-Na) and carboxymethyl cellulose sodium salt (CMC-Na). The higher interfacial impedance seen for the conventional PVdF binder suggests a protective polymer layer on the particles. By reducing the binder content, it was found that PAA-Na has a stronger affinity towards electrode components with high surface areas, which is attributed to a flexible polymer backbone and a higher density of functional groups.

Lastly, a graphite electrode was combined with a sulfur electrode to yield a balanced graphite-sulfur cell. Due to a more stable electrode-electrolyte interface the self-discharge of this cell could be reduced and the cycle life was extended significantly. This example demonstrates the possible benefits of replacing the lithium metal negative electrode with an alternative electrode material.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. 58 p.
binder, lithium-sulfur batteries, graphite, lithium-ion batteries
National Category
Physical Chemistry Polymer Chemistry Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
urn:nbn:se:uu:diva-267557 (URN)
2015-12-16, 2005, Department of Chemistry - Ångström, Lägerhyddsvägen 1, Uppsala, 16:15 (English)
Available from: 2015-11-26 Created: 2015-11-24 Last updated: 2015-11-26Bibliographically approved

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