Robust Multiscale Electron/Ion Transport and Enhanced Structural Stability in SiO_x Semi‐Solid Anolytes Enabled by Trifunctional Artificial Interfaces for High‐Performance Li‐Ion Slurry Flow Batteries

Abstract SiO_x suspension is regarded as an attractive anolyte for high‐energy‐density Li‐ion slurry flow batteries. However, the poor electronic conductivity and non‐negligible volume variation of SiO_x greatly hinder its practical applications. Herein, these issues are successfully addressed by rationally designing a trifunctional interface with mixed electron/ion and hard/soft modulated properties on SiO_x surface via H‐bonding interactions. The interface comprises a lithiated polymer layer (LiPN) interfused with functionalized single‐walled carbon nanotubes. Carbon nanotubes work as electrical tentacles to enhance the multiscale electron conduction. The LiPN layer with transferable Li‐ions facilitates ion transport. In addition, the LiPN layer employs lithiated rigid polyacrylic acid as a framework to provide mechanical support and soft nafion as a buffer to accommodate volume change, which maintains the structural integrity of SiO_x. Hence, SiO_x@LiPN/S anolytes exhibit significantly improved rate and cycle performances. Specially, the interface enables the anolytes to load more active particles (30 wt%) or less conductive additives (0.4 wt%). The semi‐solid pouch cells based on high‐active‐content anolytes with stable cyclability are first demonstrated and the flow cell using low‐conductive‐content anolytes displays a high volumetric capacity of 207 Ah L⁻¹. This strategy paves a novel approach for optimizing semi‐solid electrodes for high‐performance Li‐ion slurry flow batteries.