Design of Dual-conducting Interface in Composite Cathode by Semi-Cyclized Polyacrylonitrile Soft Coating for Practical Solid-State Lithium-Metal Batteries

Solid-solid interfaces in the composite nickel-rich layered oxide LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode for solid-state lithium-metal batteries face the thorny issues of macroscopic contact interface, significant side reaction, intergranular cracking and sluggish Li⁺/e^- transfer. To avoid such problems, we designed a high ionic/electronic dual-conducting soft gel coating on NCM811 cathode particles through the high-temperature semi-cyclized polyacrylonitrile strategy, aiming to build an unobstructed channel for enhanced transport kinetics in solid composite cathode. Additionally, an inner electrochemically stable interface layer is constructed between the coating layer and cathode particles vialing in situ electrochemical conversion. Thus, the coating layers with specific properties can maintain structural integrity of NCM811 cathode via buffering the internal stress during lithiation/delithiation and endows the solid-state battery with low interfacial resistance, outstanding cycling stability and thermal safety stability. Notably, this facile and scalable surface engineering provides a novel solution for the application of high nickel cathode materials in solid-state batteries.