Manipulating the Diffusion Energy Barrier at the Lithium Metal Electrolyte Interface for Dendrite-free Long-life Batteries

Abstract Constructing an artificial solid electrolyte interphase (SEI) on lithium metal electrode is a promising approach to address the rampant growth of dangerous lithium morphologies (dendritic and dead Li0) and low Coulombic efficiency that plague development of lithium metal batteries. But it is not known how the Li+ transfer behavior in the SEI is coupled with mechanical properties. We demonstrate here a facile and scalable solution-processed approach to form a Li3N-rich SEI with a phase-pure crystalline structure that minimizes the diffusion energy barrier of Li+ across the SEI. Compared with a polycrystalline Li3N SEI obtained from conventional practice, our phase-pure/single crystalline Li3N-rich SEI constitutes an interphase of high mechanical strength and low Li+ diffusion barrier. We elucidate the correlation among Li+ transference number, diffusion behavior, concentration gradient, and the stability of the lithium metal electrode by integrating phase field simulations with experiments. We demonstrate extreme reversibility and ultra-stable charge/discharge cycling behaviors for both symmetric cells and full lithium-metal batteries constructed using this Li3N-rich SEI. These studies provide new insight into the designing and engineering an ideal artificial SEI for stable and high-performance lithium metal batteries.