Perovskite Quantum Dots for Lewis Acid–Base Interactions and Interface Engineering in Lithium-Metal Batteries

Polymer solid-state electrolytes (SSEs) hold the key to the ever-growing demand for high-performance, flexible, and rugged reliability lithium-metal batteries (LMBs). However, polymer SSEs suffer from sluggish ion-transport dynamics and interface instability because of their low ionic conductivity, poor lithium-ion transfer ability, and uncertain dendrite growth. Here, we show that perovskite quantum dots (PQDs), CsPbX₃ with different halogens (X = Cl, Br, and I), can perform as Lewis acid–base interactions and interface engineering for polyethylene oxide (PEO)-based LMBs. This combined action efficiently promotes large-current characteristics and high-power capability through realizing simultaneously high ionic conductivity and a large lithium-ion transference number. We have observed significant increases in the lithium-ion transference number ranging from 0.39 to 0.66 and ionic conductivity ranging from 2.5 × 10^–6 to 1.0 × 10^–4 S cm^–1 at 30 °C for CsPbI₃ PQDs decorated PEO SSEs. We reveal that the enabling role of Lewis acid–base interactions in PEO-PQD SSEs originates from the kinetically inhibiting crystallization of quantum-sized CsPbX₃ and strong electrostatic adsorption of halogen atoms. These actions in the interface between lithium-metal anodes and PEO SSEs, in turn, trigger the formation of a uniformly homogeneous and mechanically strengthened LiX interface layer and hence grant LMBs robust solid electrolyte interface (SEI), high-rate capability, and high safety.