Some New Directions in Solid Electrolytes

Solid electrolytes have the potential to be safe replacements for the liquid electrolytes used in lithium-ion batteries. For the most part, solid electrolytes are based on ceramic materials and while there has been significant progress in this field, it is always interesting to consider alternative approaches.  This presentation will cover the synthesis and properties of two very different solid electrolytes.  In one case, we use sol-gel chemistry to create a pseudo-solid-state electrolyte in which an ionic liquid electrolyte is confined in a mesoporous inorganic matrix.  This ‘ionogel’ leads to a material that possesses the electrochemical properties of the ionic liquid despite being a macroscopic solid.  The effectiveness of this solid electrolyte has been demonstrated in electrochemical cells of the type LiFePO4/ionogel/Li. The versatility of ionogel synthesis and chemistry enables novel fabrication routes for various electrochemical device architectures.  The second approach is based on photo-polymerizing a well known epoxy-based photoresist, SU8, which has been modified with LiClO4 to form a gel electrolyte.  The presence of the lithium salt reduces the degree of cross-linking during UV exposure, leading to increased Li+ conductivity but without sacrificing its excellent photo-patterning properties. The material also exhibits good thermal and electrochemical stability, excellent mechanical integrity and micron-scale patterning. The incorporation of this material into photo-patterned electrochemical energy storage devices has been demonstrated.