Conference Dates
October 4-9, 2015
Abstract
The micro-pillar splitting method has been used to assess the influence of lithiation on the fracture toughness of LixMn2O4 micro-particles used as cathode materials in lithium ion battery composites. The materials under investigation consisted of hard LiMn2O4 particles embedded in a soft and compliant epoxy matrix to form the composite electrode. Five different samples were extracted from commercial battery cells at different states of charge (SoC% = 0-20-50-75-100%). These correspond to different lithium concentrations in the particles, as measured by inductively coupled plasma optical emission spectrometry (ICP-OES). Experimental results from the pillar splitting experiments show a significant effect of the SoC%, and therefore the lithiation level, on the fracture toughness and failure mechanisms of the LixMn2O4 particles. Specifically, the toughness of the fully charged electrodes (de-lithiated material) is much lower that the fully discharged electrodes. SEM observation of split pillars (see figure) confirms a significant change in toughness of the materials as a function of the lithium concentration in the particles. The results compare well with recent investigations where a loss in ductility of electrode materials has been observed after de-lithiation. This suggests that a knowledge of the changes in toughness of the materials may be extremely important for prediction of in-service damage of the electrodes due to diffusion-induced stress during charge/discharge cycles. An analysis of pillar splitting for a hard film on a compliant substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties. This ensures a correct estimation of the critical splitting load in the case of the composite materials studied in this investigation
Recommended Citation
Marco Sebastiani, K.E. Johanns, Hugues Amanieu, and G.M. Pharr, "Effects of lithiation on the fracture toughness and mechanical properties of LiMn2O4 cathode battery materials" in "Nanomechanical Testing in Materials Research and Development V", Dr. Marc Legros, CEMES-CNRS, France Eds, ECI Symposium Series, (2015). https://dc.engconfintl.org/nanomechtest_v/89