  Dendrite formation is a major obstacle, such as capacity loss and short
circuit, to the next-generation high-energy-density lithium (Li) metal
batteries. The development of successful Li dendrite mitigation strategies is
impeded by an insufficient understanding of Li dendrite growth mechanisms.
Li-plating-induced internal stress in Li metal and its effect on dendrite
growth have been studied in previous models and experiments, while the
underlying microcosmic mechanism is elusive. Here, we analyze the role of
plating-induced stress in dendrite formation through first-principles
calculations and ab initio molecular dynamics simulations. We show that the
deposited Li forms a stable atomic nanofilm structure on copper (Cu) substrate.
It is found that the adsorption energy of Li atoms increases from the Li-Cu
interface to deposited Li surface, leading to more aggregated Li atoms at the
interface. Compared to the pristine Li metal, the deposited Li in the early
stage becomes compacted and suffers in-plane compressive stress. Interestingly,
we find that there is a giant strain gradient distribution from the Li-Cu
interface to deposited Li surface, which makes the deposited atoms adjacent to
the Cu surface tend to press upwards with perturbation, causing the dendrite
growth. This understanding provides an insight to the atomic-scale origin of Li
dendrite growth and may be useful for suppressing the Li dendrite in the
Li-metal-based rechargeable batteries.

Materials Science