Title: Modeling and Visualization of Anode Materials’ Deformation during Li Insertion

Speaker: Yue Qi, Chemical Sciences and Materials Systems Lab, GM R&D

Date/Time: Wednesday, March 3, 2010, 1:30 – 2:30 pm        

Location: CSRI Building, Room 90 (Sandia NM)

Brief Abstract: The mechanics and microstructure of electrodes are critical in determining the performance and durability of lithium-ion batteries, especially the new large format cells and packs developed for transportation applications. During battery operation, Li flows into and out of electrode particles, causing microstructural changes and deformation-induced degradation. A variety of models have been proposed to interpret these mechanical and microstructural changes, but they lack of proper input materials’ properties and direct experimental supports. In this study, the elastic properties of Li intercalation graphite compounds were predicted from first principles calculations. The modeling results showed a three-fold increase in graphite anode modulus during Li insertion. These properties were then inputted into a finite element model to reveal the deformation of the overall porous anode with packed particles. The results are compared with the first direct in-situ measurements of microstructural strain in a commercial graphite anode. The color variation of graphite with Li concentration creates lithium spatial maps. Digital image correlation analysis provides corresponding deformation and strain fields, displaying both dilation and contraction. Through the combination of experimental measurement and theoretical analysis, the unexpected contraction during lithiation is explained by the stiffening of graphite upon lithiation. The result confirms that the assumption of constant material properties, used in many current battery models, is not appropriate.

CSRI POC: Peter Schultz, (505) 845-7771