In-situ characterizations of chemo-mechanical behavior of free-standing vanadium pentoxide cathode for lithium-ion batteries during discharge-charge cycling using digital image correlation

The free-standing V₂O₅ nanobelts cathodes for lithium-ion batteries are synthesized through hydrothermal reaction followed by anneal treatments and vacuum filtration deposition. The well cycling performances of the electrode were verified by battery test system. The microstructure and surface morphologies of the V₂O₅ electrode before and after discharge-charge cycles were analyzed by X-ray diffraction and scanning electron microscope, respectively. The evolutions of strain fields of free-standing V₂O₅ electrodes are in-situ measured by digital image correlation technique. The heterogeneous features of in-plane strains of V₂O₅ electrode surface in macro-scales are characterized and systematically discussed as a function of test time (or voltage). Given the effect that the elastic modulus is dependent on the concentration and cycling number, the evolutions of in-plane stresses of V₂O₅ cathodes during discharge-charge cycling are estimated using a chemo-mechanical constitutive equation. The influences of chemical and mechanical components on in-plane stresses are extracted and discussed, respectively. The results are crucial to further reveal the chemo-mechanical coupling failure mechanism of V₂O₅ cathode and optimize the electrode structure of lithium-ion battery systems.