Ether Based Electrolyte, LiB(CN)(4) Salt and Binder Degradation in the Li-O-2 Battery Studied by Hard X-ray Photoelectron Spectroscopy (HAXPES)
Magazine article, 2012

Li-O-2 cells composed of a carbon cathode containing an alpha-MnO2 nanowire catalyst and a Kynar (PVDF-HFP) binder were cycled with different electrolytes containing 0.5 M LiB(CN)(4) salt in polyethylene glycol dimethyl ether (PEGDME) or tetraethylene glycol dimethyl ether (Tetraglyme) solvents. All cells exhibited fast capacity fading. To explain this, the surface chemistry of the carbon electrodes were investigated by synchrotron based hard X-ray photoelectron spectroscopy (HAXPES) using two photon energies of 2300 and 6900 eV. It is shown that the LiB(CN)(4) salt and Kynar binder were degraded during cycling, forming a layer composed of salt and binder residues on the cathode surface. The degradation mechanism of the salt differed in the two tested solvents and, consequently, different types of boron compounds were formed during cycling. Larger amounts of the degraded salt was observed using Tetraglyme as the solvent. With a nonfluorined Li-salt, the observed formation of LiF, which might be a reason for the observed blockage of pores in the cathode and for the observed capacity fading, must be due to Kynar binder decomposition. The amount of LiF formed in the PEGDME cell was larger than that formed in the Tetraglyme cell. The results indicate that not only the electrolyte solvent, but also electrolyte salt as well as the binder used for the porous cathode must be carefully considered when building a successful rechargeable Li-O-2 battery.

chemistry

nanowires

ionic liquids

lithium-oxygen battery

b(cn)(4)(-) anion

graphite

li-air cells

alpha-mno2

stability

polymer electrolyte

carbonate electrolytes

Author

S. R. Younesi

Uppsala University

M. Hahlin

Uppsala University

Marcel Treskow

Chalmers, Applied Physics, Condensed Matter Physics

Johan Scheers

Chalmers, Applied Physics, Condensed Matter Physics

Patrik Johansson

Chalmers, Applied Physics, Condensed Matter Physics

K. Edstrom

Alistore - European Research Institute

Uppsala University

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 116 35 18597-18604

Areas of Advance

Transport

Energy

Materials Science

Subject Categories

Chemical Sciences

DOI

10.1021/jp303691m

More information

Latest update

9/6/2018 2