Design of Ultrathin Current Collectors via Cyclically Plastic Yield for Fabrication of High Capacity Lithium Ion Batteries

In this manuscript a strategy is developed for the design of ultrathin current collectors in the fabrication of high capacity lithium ion batteries. A lithiation-delithiation induced elastoplasticity analysis is performed to determine the thickness limit of a current collector for a given cycle life. The calculation results show that both the plastic yield and cyclical plastic deformation of current collectors are beneficial to not only the battery capacity due to a less inactive packing but also the cyclic performance because of lower stresses in the active layers. There are three possible elastoplastic behaviors for current collectors of different thicknesses, i.e. pure elastic, plastic shakedown and cyclic plasticity. Cyclic plasticity is preferred because it occurs in the thinnest current collector where the stress in the active layer is found to be the lowest. Furthermore, a fatigue analysis is carried out to determine the relation between current collector thickness and cycle life. Finally, by using this design method to evaluate three commercial 18650 lithium ion batteries reported in literature, it is found that all the examined battery structures can be optimized using thinner current collectors; in some cases, the thickness of these collectors could be even reduced to half their original thickness.