Understanding\nthe\nCarbon Additive/Sulfide Solid Electrolyte\nInterface in Nickel-Rich Cathode Composites and Prioritizing the Corresponding\nInterplay between the Electrical and Ionic Conductive Networks to\nEnhance All-Solid-State-Battery Rate Cap

All-solid-state\nlithium batteries, including sulfide\nelectrolytes\nand nickel-rich layered oxide cathode materials, promise safer electrochemical\nenergy storage with high gravimetric and volumetric densities. However,\nthe poor electrical conductivity of the active material results in\nthe requirement for additional conducive additives, which tend to\nreact negatively with the sulfide electrolyte. The fundamental scientific\nprinciple uncovered through this work is simple and suggests that\nthe electrical network benefits associated with the introduction of\nshort-length carbons will eventually be overpowered by the increase\nin bulk resistance associated with their instability in the sulfide\nelectrolyte. However, applying just the right amount of short carbon\nfibres minimizes degradation of the sulfide solid electrolyte and\nmaximizes the electron movement. Therefore, we propose the application\nof a low-weight-percent carbon nanotubes (CNTs) coating on the nickel-rich\ncathode LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> (NCM811) along with large-aspect-ratio carbon nanofibers (CNFs)\nas the primary conductive additive. When only 0.3 wt % CNTs was utilized\nwith 4.7 wt % CNFs, an initial Coulombic efficiency of 83.55% at 0.05<i>C</i> and a notably excellent capacity retention of 90.1% over\n50 cycles at 0.5<i>C</i> were achieved along with a low\nionic resistance. This work helps to confirm the validity of applying\nshort carbon pathways in sulfide-electrolyte-based cathode composites\nand proposes their combination with a larger primary carbon additive\nas a solution to the ongoing all-solid-state battery rate and instability\nissues.