Dresden 2017 – wissenschaftliches Programm
SYLI 8.1: Vortrag
Mittwoch, 22. März 2017, 15:45–16:00, IFW D
Process monitoring of charging/discharging of lithium ion battery cathodes by operando SQUID magnetometry — •Roland Würschum1, Gregor Klinser1, Stefan Topolovec1, Harald Kren2, Stefan Koller2, Walter Goessler3, and Heinz Krenn4 — 1Inst. of Mater. Phys., Graz Univ. of Technology, Graz, Austria — 2VARTA Micro Innovation GmbH, Graz — 3Inst. of Chem., Univ. Graz — 4Inst. of Phys., Univ. Graz
The magnetic susceptibility χ of cathode materials, which contain transition metals, substantially changes during charging/discharging and, therefore, serves as highly sensitive fingerprint for the charge state. A novel pathway in this direction has recently opened up by developing in-situ electrochemical techniques for magnetometry. Operando magnetic χ-measurements on LixCoO2  and LixNi1/3Mn1/3Co1/3O2 (NMC) cathode materials  in a SQUID magnetometer during repetitive electrochemical cycling were performed enabling a continuous and bulk sensitive monitoring of the charge compensation process. Upon charging of NMC up to Li contents of x = 1/3 exclusively Ni undergoes oxidation, namely in two consecutive steps Ni2+→Ni3+ for x>2/3 and Ni3+→Ni4+ for 2/3>x>1/3 . Co oxidation for x<1/3 is found to be irreversible . In the case of LixCoO2, evidence is found for a nonmetal−metal transition of Anderson−type . In addition to Co also O undergoes partial oxidation, as also observed for NMC.
 St. Topolevec et al., J. Sol. State Electrochem. 20 (2016) 1491.
 G. Klinser et al., Appl. Phys. Letters 109 (2016) 213901.