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Mechanical Degradation in LiMn1.95Al0.05O4 Electrodes

Di Chen (), Zungsun Choi (Karlsruhe Institute of Technology), Dominik Kramer (Helmholtz Institute Ulm), Reiner Moenig (Karlsruhe Institute of Technol)

Lithium ion batteries: When Chemistry meets Mechanics

Wed 9:00 - 10:30

Salomon 003

Lithium ion batteries are promising candidates for future electrical energy storage. For many applications the long term reliability of these systems is of very high importance. We have performed electrochemical tests and electron microscopic investigations in order to assess the reliability of LiMn1.95Al0.05O4 electrodes. Conventional electrodes were made from a commercial cathode material and tested to cycle numbers of up to 800 cycles. Using a special SEM technique it was possible to exclude reactions with atmosphere and to be able to monitor a given location over the course of many cycles. In the experiments, a significant amount of mechanical damage was detected which mainly consisted of cracks running through the electrode particles. Such cracks create additional surfaces but also can lead to the loss of electrical contact. A statistical analysis of the cracks showed that there is a strong dependence of the fracture probability on the electrode particle size. An additional mechanism was identified in experiments at higher number of cycles. Besides the cracks that seem to be caused by brittle fracture, sheared particles were found. This type of damage appears to be based on dislocations and increases with increasing number of cycles. The evolution and the form of damage shows similarities to fatigue damage as found in metals. In this presentation details on the damage mechanisms will be given, their effect on the electrochemical performance will be addressed and suggestions will be made in order to improve the reliability of electrodes made from this insertion material.