Abstract
An ever present challenge for Li-ion batteries is the formation of metallic
dendrites on cycling that dramatically reduces cycle life and leads to the
untimely failure of the cell. In this work we investigate the modes of
Li-cluster formation on pristine and defective graphene. Firstly, we
demonstrate that on a defect free surface the cluster formation is impeded by
the thermodynamic instability of \ce{Li_2} and \ce{Li_3} clusters. In contrast,
the presence of a vacancy dramatically favours clustering. This provides
insights into the two modes of Li-growth observed: for the pristine basal plane
if the Li-Li repulsion of the small clusters can be overcome then plating type
behaviour would be predicted (rate / voltage dependent and at any point on the
surface); whilst dendritic growth would be predicted to nucleate from vacancy
sites, either pre-existing in the material or formed as a result of processing.