Solution Processing of Lithium‐Rich Amorphous Li‐La‐Zr‐O Ion Conductor and Its Application for Cycling Durability Improvement of LiCoO2 Cathode as Coating Layer

Lithium‐rich amorphous Li‐La‐Zr‐O (a‐Li‐La‐Zr‐O) electrolyte is successfully synthesized using sol–gel processing method. With unlimited compositions of the amorphous structure, lithium‐rich compositions are systematically investigated to determine optimal composition and optimized processing conditions of a‐Li‐La‐Zr‐O coatings. There is an improvement in ionic conductivity of a‐Li‐La‐Zr‐O with Li content increasing, specifically from 3.0 × 10−8 S cm−1 (Li8La2Zr2O11) to 1.18 × 10−6 S cm−1 (Li18La2Zr2O16), thereby resulting in low activation energy. The high‐ionic‐conductivity a‐Li‐La‐Zr‐O is implemented as an artificial solid electrolyte interface coating layer on cathode materials. The a‐Li‐La‐Zr‐O‐coated LiCoO2 (LCO) and LiNi0.8Mn0.1Co0.1O2 (NMC 811) coin cells exhibit better cycling performance than the bare coin cell at the optimum compositional ratio of a‐Li‐La‐Zr‐O. A‐Li‐La‐Zr‐O can be a promising material for solid electrolyte battery and a potential coating layer for the modification of cathode surface. An excellent low‐temperature‐fabricated amorphous‐Li‐La‐Zr‐O coating layer is found by conventional sol–gel processing, which functions as a protective passivation layer with high lithium‐ion conductivity contributing to impeding the degradation of the core active material during charge/discharge, and significantly extends the cycle life of LiCoO2‐based cathode battery cell.