Reducing Diffusion Induced Stress of Bilayer Electrode System by Introducing Pre-Strain in Lithium-Ion Battery

Lithium-ion battery (LIB), as energy storage devices, is widely used in portable electronic devices and have the promising applications in electric vehicles. The volume change and large stress can lead to electrode pulverization and resultant loss of electrical contact from current collector, which is considered to be one of the main reasons in capacity degradation of LIB. To reduce diffusion induced stress of electrode system during lithium ion diffusion, a chemo-mechanical coupled theoretical model of bilayer electrode system of electrode layer bonded to the current collector is established. The theoretical results show that diffusion induced stresses at the electrode-collector interface and maximum tensile stress at the top surface of electrode layer are alleviated greatly by introducing pre-strain. The effects of pre-strain and lithium ion concentration on chemo-mechanical coupled behavior of bilayer electrode system are discussed. In particular, the lithium ion concentration difference strongly depends on the diffusion thickness and time. In addition, the effects of plastic deformation of current collector and diffusion time on biaxial stress distribution are also discussed. The biaxial stress decreases with the increasing of pre-strain and with the decreasing of time during galvanostatic charging. The curvature and biaxial stress when considering plastic deformation is smaller than that when not considering the plastic deformation. The results obtained from this investigation will provide the reference to reduce the diffusion induced stress and improve the ion diffusion performance of LIB.