Experimental Investigation of the Influence of the Electrolyte Composition on the Ageing Behavior of Separators in Lithium-Ion Cells

The most widely used liquid non-aqueous electrolytes for lithium-ion cells used in  HEV (hybrid electric vehicle), PHEV (plug-in-hybrid electric vehicle) and EV (electric vehicle) applications consist of LiPF6 dissolved in carbonates (e.g. EC, DMC and DEC). These electrolytes undergo a variety of hydrolysis and thermal aging mechanisms [1]. Ongoing decomposition reactions lead to further impurities inside the lithium-ion cell which are not well-known. The separator is a second critical component in lithium-ion cells, which can be classified into three groups according to structure and composition: microporous polymer membranes, non-woven fabric mats and inorganic composite membranes [2].

In this contribution, the decomposition reaction mechanisms are evaluated under a number of different thermal conditions for various commercial electrolytes from automotive lithium-ion cells. Furthermore, their influences on the ageing behaviour of different separator types are investigated. Details of the experimental procedure, analytical methods (NMR, GC-MS, SEM/EDX) and first results will be presented. Finally, we will give an overview of our mechanistic interpretation.

References:

 [1]        P. Handel, G. Fauler, K. Kapper, M. Schmuck, C. Stangl, R. Fischer, F. Uhlig, S. Koller, J. of Power Sources 2014,

             doi: 10.1016/j.jpowersour.2014.05.080

 [2]        S. Zhang, J. of Power Sources 2007, 164, 351 – 364

Acknowledgement: 

This research is funded by the German Federal Ministry of Education and Research (BMBF) under the grant number 03X4631E within the cluster “excellence and technological implementation of Battery research (ExcellentBattery).