Correlating the mechanical strength of positive electrode material particles to their capacity retention

Strategies to maximize the energy density of Li-ion cells include increasing the Ni content of the cathode active material (CAM), decreasing the porosity of the cathode, and increasing the depth of discharge during cycling. These strategies put high mechanical stress on the typically polycrystalline CAM, whether it is due to anisotropic volume expansion of the crystallites during charge-discharge cycling or to the high calendering pressures needed to reach target electrode porosities. Here, we study the impact that Al and W dopants have on the mechanical properties of polycrystalline LiNiO2 by conducting “crush tests.” This method is a simple way to predict whether a material can bear the mechanical stress it will endure in cell cycling. A universal tension/compression testing system is also used to quantify the compression work of the studied materials. Materials with higher compression work also have higher capacity retention during cycling.