Abstract
Aqueous batteries have received a great deal of attention for grid-scale energy storage applications but suffer from low-capacity retention and utilization. A lack of understanding of chemomechanical instabilities and charge storage mechanisms in cathodes limits the development of advanced aqueous batteries. To shed light on these instabilities, operando techniques are necessary to probe the complex interplay between electrochemistry and mechanics during cycling. Here, we report an operando technique to probe electrochemical strains in cathodes in aqueous electrolytes during battery cycling via optical imaging and digital image correlation. Operando mechanical measurements indicate that the cathode undergoes positive strain generation during discharge and negative generation during charge. Strain derivatives reveal a close correlation between electrochemical and mechanical behaviors, highlighting the connection between electrochemistry and mechanics. This operando imaging technique is broadly applicable and paves the way for a deeper understanding of deformation mechanisms in aqueous, multivalent ion battery materials.