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All-solid-state lithium-ionbattery is considered to be one of the most promising next-generationbattery technologies. Understanding the interfacial evolution of asolid electrolyte and a cathode electrode during mixing and sinteringis of great importance and can provide guidance to avoid forming unwantedcompounds and decrease the interfacial resistance. In this work, chemicalcompatibilities are investigated between a Ta-doped Li7La3Zr2O12 （LLZO） solid electrolyteand major commercial metal-oxide cathodes LiCoO2 （LCO）and Li-（NiCoMn）1/3O2 （NCM） through ball-millingand cosintering processes. As revealed by X-ray absorption spectroscopyand transmission electron microscopy, LLZO spontaneously covers themajority of the large LCO and NCM particles with a thickness of ～100nm after ball milling. The thickness of LLZO layer on these cathodesdecreases to about 10 nm after?cosintering at 873 K, and an interfaciallayer of approximately 3 nm is observed for NCM/LLZO. LCO shows ahigher thermal stability than NCM. Density functional theory （DFT）-basedsimulations and electrochemical measurements suggest Ni–Laand Ni–Li exchange could happen at the NCM/LLZO interface andLi can diffuse from the interface into NCM to occupy the Ni vacancyat high temperature. The Li depletion layer after diffusion at theinterface induces the decomposition of LLZO and the formation of La2Zr2O7 and LaNiO3 interfaciallayer.
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