Chemo-Mechanical Coupling Measurement of LiMn2O4 Composite Electrode during Electrochemical Cycling

Real-time monitoring of the mechanical behavior of cathode materials during the electrochemical cycle can help obtain an in-depth understanding of the working mechanism of lithium-ion batteries. The LiMn2O4 composite electrode is employed as the working electrode in this artificial cell, which is conceived and produced along with a chemo-mechanical coupling measurement system. The multi-layer beam composite electrode made of LiMn2O4 is monitored in real time using a CCD camera to track its curvature deformation. Experiments show that the curvature of the LiMn2O4 electrode decreases with the extraction of lithium ions and increases during the lithiation process. In the meantime, a theoretical framework was developed to examine the connection between curvature change and mechanical characteristics. Thus, the elastic modulus, strain, and stress of the LiMn2O4 composite electrode were extracted by combining the bending deformation and theoretical model. The results show that the elastic modulus of the LiMn2O4 composite electrode decreases from 59.61 MPa to 12.01 MPa with the extraction of lithium ions during the third cycle. Meanwhile, the stress decreases from 0.46 MPa to 0.001 MPa, and the strain reduces from 0.43 to 0. Its changes reverse during the lithiation process. Those findings could have made a further understanding of the mechanical properties in lithium-ion batteries.