Comparison of fresh and aged lithium iron phosphate cathodes using a tailored electrochemical strain microscopy technique

Matthias Simolka; Hanno Kaess; Kaspar Andreas Friedrich

doi:10.3762/bjnano.11.46

Comparison of fresh and aged lithium iron phosphate cathodes using a tailored electrochemical strain microscopy technique

Beilstein J Nanotechnol. 2020 Apr 7:11:583-596. doi: 10.3762/bjnano.11.46. eCollection 2020.

Authors

Matthias Simolka¹, Hanno Kaess¹, Kaspar Andreas Friedrich^{2

3}

Affiliations

¹ University of Applied Sciences Esslingen, Faculty of Basic Sciences, 73728 Esslingen, Germany.
² German Aerospace Center (DLR), Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany.
³ University of Stuttgart, Institute of Building Energetics, Thermal Engineering and Energy Storage (IGTE), Pfaffenwaldring 31, 70569 Stuttgart, Germany.

Abstract

Electrochemical strain microscopy (ESM) is a powerful atomic force microscopy (AFM) mode for the investigation of ion dynamics and activities in energy storage materials. Here we compare the changes in commercial LiFePO₄ cathodes due to ageing and its influence on the measured ESM signal. Additionally, the ESM signal dynamics are analysed to generate characteristic time constants of the diffusion process, induced by a dc-voltage pulse, which changes the ionic concentration in the material volume under the AFM tip. The ageing of the cathode is found to be governed by a decrease of the electrochemical activity and the loss of available lithium for cycling, which can be stored in the cathode.

Keywords: LiFePO4; activity; ageing; cathode; electrochemical strain microscopy (ESM).

Grants and funding

The authors gratefully acknowledge the funding by the Federal Ministry of Education and Research within the Framework Concept “Forschung an Fachhochschulen” (13FH113113IN6 and 03FH028IX4) and managed by the Project Management Agency VDI Technologiezentrum GmbH.