Versatile Peroxide Route-Based Kinetics-Controlled Coating Method to Construct Uniform Alkali Metal-Containing Fast Ionic Conductor Nanoshells

Constructing a uniform coating of alkali metal-containing fast ionic conductors is crucial for realizing multifunctional responses and functionalities. However, the uncontrolled coprecipitation of alkali and transition metal ions, stemming from their significant difference in reactivity, poses a significant challenge in pursuing homogeneous and continuous nanoshells for fast ionic conductors. Here, we report a versatile peroxide-based kinetics-controlled coating approach for constructing alkali metal-containing fast ionic conductors using LiNbO₃ as a proof-of-concept. Hydrogen peroxide (H₂O₂) was employed as an innovative precipitant, and the deposition kinetics could be precisely tuned by adjusting the pH value of the solution to facilitate the coprecipitation of the transition metal and ammonium/hydrogen ions. The latter could subsequently be exchanged with lithium ions and transformed into uniform LiNbO₃ nanoshells after low-temperature annealing (280 °C). The obtained LiNbO₃ coating layers are continuous, thickness-tunable, and exhibit significantly higher ionic conductivity, 2 orders of magnitude greater than conventional counterparts. This enhancement enables solid-state batteries with excellent cycling and rate performance. Furthermore, this method is extendable to various alkali metal-based (Li, Na, and K) fast ionic conductor nanoshells, injecting new vitality into the advanced applications of fast ionic conductors in various battery systems.