Ultrasonic diagnosis of the nonlinear aging characteristics of lithium-ion battery under high-rate discharge conditions

The diagnosis and analysis of the nonlinear aging behavior of lithium-ion batteries are of great necessity for its safety monitoring and management. In this paper, an important non-destructive characterization technique, i.e., ultrasonic is adopted to detect the evolution of the mechanical structure within the battery by analyzing the changes of acoustic waves. Specifically, S-value is proposed to reflect the energy dissipation of acoustic waves, which reveals the nonlinear decay trajectory of battery capacity. Meanwhile, the collapse of the cathode material is confirmed to be the main cause of the capacity fade for the battery under high-rate discharging conditions, proved by the reduction of the characteristic peak. Moreover, both theoretical analysis and experimental verification demonstrate the most serious damage of tensile type rupture on battery performance. All the above results can provide a reliable reference for the early warning of battery health state.