Size‐Controlled Talc Nanosheet Ionogel Electrolytes for Dendrite Suppression in Solid‐State Sodium Metal Batteries

Ionogels composed of solid matrices and ionic liquids are promising candidates as solid-state electrolytes for sodium (Na) metal batteries due to their nonflammability, high thermal stability, and desirable electrochemical and interfacial properties. Among various solid matrices, nanoscale materials are particularly attractive for increasing the mechanical modulus of ionogel electrolytes, contributing to the suppression of Na dendrite growth on metal anodes. However, the mechanistic understanding of this suppression remains limited. Here, size-controlled talc nanosheets are introduced as solid matrices to investigate their influence on the ionogel modulus and the corresponding Na dendrite growth behavior, facilitating the rational design of ionogel electrolytes for dendrite suppression. Talc nanosheets with reduced lateral dimensions and thicknesses provide larger surface areas, enhancing the ionogel modulus through stronger immobilization of ionic liquids. High-modulus ionogels with smaller nanosheets promote uniform Na deposition and reinforce the resistance of the electrolytes to vertical Na dendrite growth. Moreover, smaller talc nanosheets improve the Na-ion transference number of ionogel electrolytes. The resulting talc nanosheet ionogel electrolytes enable Na₃V₂(PO₄)₃|Na cells to exhibit favorable rate capability at room temperature with capacity retention over 99% after 500 cycles at a rate of 0.5 C.