Multifunctional Chloride-Oxide Additive Enabling Simultaneous Ionic/Electronic Conduction for High-Rate...

To address the challenges of insufficient electron transport and solid-solid contact failure caused by volume expansion in NCM cathodes in solid-state batteries, this study developed a multifunctional cathode additive─LiW₂O_(11-x)/2Cl_x (x = 0.5-10). This additive exhibits a glass-ceramic composite structure featuring dispersed nanocrystalline domains within an amorphous matrix. LiW₂O_3.5Cl₄ (C4W) combines a high electronic conductivity (1.86 S cm^-1) with a moderate ionic conductivity (0.73 mS cm^-1) at 25 °C, and its Young's modulus (12.3 GPa) matches well with that of the solid electrolyte. It can not only improve interface stability by reducing mechanical stress during cycling but also form a soft conductive network, serving as an effective alternative to traditional rigid and brittle conductive additives. Due to this synergistic effect, all-solid-state batteries exhibit excellent cycling and rate performance (capacity retention exceeding 81.31% after 10000 cycles at 5C (1C = 200 mA g^-1) at a cutoff voltage of 4.5 V and stable cycling at 1C for over 3000 cycles at 20 MPa). This study highlights the critical role of synergistically controlling electrochemical and mechanical properties in the design of composite cathodes for solid-state batteries.