Spatially Selective Solvation Structure by Electronegative Micro-Arrays for Stable Lithium-Metal Anode Interface

For electrolytes with conventional lithium salt concentration, it is not easy to generate sufficient anion-derived beneficial inorganic components to stabilize the electrolyte-lithium metal anode interface due to the repulsion of the free-state anions by the anode. In this study, the above issues are solved through the strong interaction between electronegative materials and lithium ions (Li+). A locally high Li+ concentration strategy is proposed by preparing micro-arrays of electronegative nano-hydroxyapatite (nHA) on the Cu foil. It is found that the oxygen atoms in the phosphate group (-PO4) of the nHA can strongly adsorb Li+ to form a locally Li+-rich region, which increases the probability of anions interacting with Li+. The formation of more Li+-coordinated anions at the electrolyte-anode interface can reduce the Li+ de-solvation energy barrier, and enable the anions to completely decompose into lithium fluoride (LiF) and lithium nitride (Li3N) on the Li metal anode. The interfacial transfer dynamics is accelerated and the Li dendrites are effectively suppressed. Under high current density, the anode exhibits a long lifespan with high Coulombic efficiency and small polarization voltage. The nHA micro-arrays achieve the targeted solvation structure at the electrolyte-anode interface while ensuring conventional lithium salt concentration in the bulk electrolyte. Nano-hydroxyapatite (nHA) exhibits a high Li+ binding energy of -5.99 eV. With nHA micro-arrays on the Cu foil, a locally Li+-rich region forms at the electrolyte-anode interface, which can promote the generation of aggregates (AGGs) of anions. The decomposition efficiency of anions is significantly improved, leading to the formation of a more protective solid electrolyte interface (SEI) film.image