Mitigating Silicon Anode Mechanical Damage with Electrode Architecture

Large volume expansions due to lithiation create problems for silicon anode mechanical stability, as volume changes apply large stresses to the electrode composite and copper current collector. The resulting mechanical damage includes current collector wrinkling or active material delamination, or both, which lead to capacity fade and current hotspots. Strategic design of the electrode microstructural properties, including controlling electrode porosity and adhesion, has the potential to help alleviate these issues. Two strategies to control microstructure are the choice of current collector and electrode drying conditions after casting; however, these strategies are not found to be sufficient to fully solve the damage caused by high stress. As a third approach, this paper investigates a different slurry formulation that uses less silicon content (75 wt%, compared to the usual 92 wt% active material) to limit anode mechanical damage. Reducing the silicon content of the anode eliminates delamination from high-strength current collectors, improving electrochemical cycle lifetimes significantly. However, lower silicon content leads to potential losses in energy density, which we address using a multilayer architecture comprising the 75 wt% Si layer as an interface between the current collector and the 92 wt% active material layer; this interfacial layer prevents delamination while maximizing energy density. Despite improvement, minor wrinkles remain evident even with the multilayer architecture, indicating the need to combine this work with additional mitigations in the future.