Insights into the stability and reactivity of lithiated Si-binder interfaces for next generation lithium-ion batteries

We explore, through a first principle approach based on density functional theory, lithiated-silicon (Li-Si) surfaces and their intricate interactions with binders in lithium-ion batteries. A meticulous analysis of Li insertion in the Si-subsurface layer unveils crucial dynamics, including surface reconstructions, and structural changes in different Si facets (Si-110 and Si-111). The impact of lithium content and Si facet orientation on the binder adhesion strength demonstrates that increasing the number of subsurface Li atoms weakens adhesion. However, a strategic co-binding approach, in which polyvinyl alcohol (PVA) is associated with polyaniline (PANI), polyaniline functionalized PANI with boronic acid groups (B-OH_PANI) or polyvinylidene fluoride (β-PVDF), is revealed to be a decisive factor in stabilizing monomers on the surface. Advanced electronic structure analyses portray changes in the charge density distribution and electronic states due to Li insertion into the Si surfaces. Molecular dynamics simulations of bulk co-binder models provide a concrete visualization of the structural relaxations and bonding interactions at the Li-Si/co-binder interface. The insights derived from this study serve as a foundation for the design and development of cutting-edge lithium-ion battery materials.