Mechanical seed mechanism to facilitate homogeneous Li metal growth

Abstract

An intriguing mechanical seed (MS) concept that modulates (in)homogeneousLi metal growth is proposed based on an in-depth understanding of itsfundamental mechanism using unified atomistic computations. A largedataset of thermodynamic energies for Li disordered phase decouples thedual-body interactions into three components: i) crystal-like, ii) long, and iii)short bonds of Li─Li based on machine learning assisted by density functiontheory calculations. The contributions of these dual-body interactions offer amechanical factor for controlling the disordered-ordered phase transitionduring electrochemical deposition. Macroscopic molecular dynamicssimulations systematically construct the core–shell sphere andcross-sectional models to reinforce the MS premise. The former reveals thatthe lower energy level of disordered phase under the moderate compressioncauses a slow phase kinetics, whereas the strain-free mode exhibits arelatively fast transition. In addition, the cross-sectional model exhibits asmooth surface landscape for the strain-optimized case. These observationsare attributed to the surface area evolutions depending on the MS conditionsand elucidate the dynamic atomic displacements near the grain boundaryfrom a local structural perspective. The proposed mechanical design conceptfacilitates uniform Li growth and is expected to be a global parameter inharnessing the full potential of Li metal batteries.