Electrochemical performance and lifetime of the layered metal oxide electrodes depends on the structural and interfacial stabilities of the electrodes during cycling. Li-ion intercalation into electrodes results in continuous volumetric expansions / shrinkage and associated stress generation, which eventually leads to particle fracture. The interactions between electrode and electrolyte species during cycling could lead to the formation of cathode – electrolyte interface (CEI) layers on the electrode surface. Also, at the deep charge, Coulombic forces could lead to irreversible structural deformations in the layered metal oxides. In this study, our goal is to elucidate the electrochemically driven mechanical deformations in the layered cobalt oxide cathodes during Li-ion and Na-ion intercalation. Layered cobalt oxide is chosen as a model system because it allows intercalation for both Li and Na ions, and it suffers from irreversible structural deformations at deep charge. We performed in situ curvature measurement and digital image correlation measurements to probe stress and strain evolution in the electrode while cycling. Free-standing composite LiCoO2 electrodes were fabricated for strain measurements. Thin film LiCoO2 electrode was prepared using chemical vapor deposition method on a silicon wafer for stress measurements. In this talk, I will present the impact of the structural and interfacial deformations on the chemo-mechanical instabilities of cobalt oxide cathodes during Li and Na intercalation as well as at deep charge cycles. First, mechanical behavior of the LiCoO2 cathode is investigated by monitoring stress and strain generation while cycling between 3.0 – 4.2 V. Electrochemical stiffness is calculated by synchronizing stress and strain measurements. Stiffness calculations provided insight about structural stress and lattice changes on the chemo-mechanical stability of the cathode. Second, LiCoO2 cathode is charged until 5.0V to investigate the structural deformations at deep charge state and electrolyte instabilities at high voltages. Third, the impact of alkali metal ions on the chemo-mechanical instabilities is investigated by utilizing electrochemical Li/Na-ion exchange in layered cobalt oxide.

Electrochemical stiffness in layered cobalt oxide cathodes for li-ion and na-ion batteries

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.