Affiliations: [a] Tianjin Key Laboratory of Modern Engineering Mechanics, Department of Mechanics, Tianjin University, Tianjin, China | [b] Periodical Centre, Tianjin Normal University, Tianjin, China
Abstract: For Li-ion batteries, the main challenges of performance and lifetime decay are primarily dominated by the electrode mechanical behavior such as stress, fracture and structure degradation. Herein, an in situ experimental method is proposed to investigate the mechanical behavior during the electrochemical process. A customized electrochemical cell with a glass window is designed and used in conjunction with a charge-coupled device optical acquisition system to monitor electrode deformation during the electrochemical process. Further, three equations that characterize the mechanical responses are established, including an equation governing the evolution of elastic modulus as a function of Li concentration and an electrochemical stress model with a Li-dependent elastic modulus for modification of the standard Stoney equation. Finally, combining the measured deformation in the Si-composite electrode with these three equations, the elastic modulus and stresses are quantitatively characterized with capacity such as surface stress in the Si-composite electrode material and tangential stress at the interface. These new results show a significant softening of the Si-composite electrode material by 89%, where the softening significantly relieves the axial stress in the Si-composite electrode material and the tangential stress in the interface by 87%.
Keywords: Si-composite electrode, material properties, stress, mechanical models, in situ experiments
