Capacity dependent mechanical behaviour of anodes in lithium-ion batteries

Abstract

It is well known that the rapid growth of battery capacity brings more serious safety concerns. To investigate capacity dependent mechanical behaviour of electrodes, uniaxial tensile tests are performed on the anodes from three different capacity of batteries. The structural changes and the stress mechanism in the anodes are obtained through scanning electron microscopy (SEM) images and theoretical calculations. The experimental results show that the elasticity modulus, tensile strength and fracture energy of anodes decrease with increasing battery capacities. Besides, the stress-strain curves of anodes show ductile-to-brittle transition as the battery capacity increases. Microstructure observation through SEM reveals that the reason for this phenomenon is the thickness effect of electrode thin films. The active material layer of high capacity anodes is thicker than that of low capacity anodes. The mechanical properties of anodes exhibit a significant thickness effect and the thinner anodes possess better resistance to tensile fracture than the thick anodes. This study provides a reference for the safety design and optimization of battery.