Versatile\nPeroxide Route-Based Kinetics-Controlled\nCoating Method to Construct Uniform Alkali Metal-Containing Fast Ionic\nConductor Nanoshells

Constructing a uniform coating of\nalkali metal-containing fast\nionic conductors is crucial for realizing multifunctional responses\nand functionalities. However, the uncontrolled coprecipitation of\nalkali and transition metal ions, stemming from their significant\ndifference in reactivity, poses a significant challenge in pursuing\nhomogeneous and continuous nanoshells for fast ionic conductors. Here,\nwe report a versatile peroxide-based kinetics-controlled coating approach\nfor constructing alkali metal-containing fast ionic conductors using\nLiNbO<sub>3</sub> as a proof-of-concept. Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) was employed as an innovative precipitant,\nand the deposition kinetics could be precisely tuned by adjusting\nthe pH value of the solution to facilitate the coprecipitation of\nthe transition metal and ammonium/hydrogen ions. The latter could\nsubsequently be exchanged with lithium ions and transformed into uniform\nLiNbO<sub>3</sub> nanoshells after low-temperature annealing (280\n°C). The obtained LiNbO<sub>3</sub> coating layers are continuous,\nthickness-tunable, and exhibit significantly higher ionic conductivity,\n2 orders of magnitude greater than conventional counterparts. This\nenhancement enables solid-state batteries with excellent cycling and\nrate performance. Furthermore, this method is extendable to various\nalkali metal-based (Li, Na, and K) fast ionic conductor nanoshells,\ninjecting new vitality into the advanced applications of fast ionic\nconductors in various battery systems.