Cellulose Nanocrystal-Based Superionic Hierarchical Liquid Crystal Electrolytes

Abstract

New electrolyte design principles to increase the mechanical properties without sacrificing the ionic conductivities are needed for higher energy density, safer, and sustainable-by-design solid-state batteries. Herein, we describe hierarchical liquid crystal electrolytes based on colloidal scale mechanically reinforcing cellulose nanocrystals (CNCs) in a molecular scale lamellar/smectic medium of trifunctional alcohol ethoxy sulfonate surfactant (AES) containing Lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt. The oligo(ethylene glycol) ionophilic domains of AES provide nanoconfined dynamic layered nanoscopic pathways for ion transport of Li+ cations and TFSI– anions, while CNCs independently reinforce the mechanical properties and direct the ion path continuity. The mechanical properties can be increased three orders of magnitude without deteriorating the ionic conductivity, conceptually suggesting superionic transport behavior, as quantified using Walden plots. As liquid crystalline packing, in general, can also have a potential to promote stabilization of electrode/electrolyte interphases, the present approach suggests new concepts for the next generation multifunctional battery electrolytes.