Noncovalent Approach to Liquid-Crystalline Ion Conductors: High-Rate Performances and Room-Temperature Operation for Li-Ion Batteries

Abstract

We report advanced liquid-crystalline (LC) electrolytes for use in lithium-ion batteries (LIBs). We evaluated the potential of LC electrolytes with a half cell composed of Li metal and LiFePO 4 which is a conventional positive electrode for LIBs. Low-molecular-weight carbonates of ethylene carbonate or propylene carbonate were incorporated into the two-dimensional (2D) nanostructured electrolyte composed of mesogen-containing carbonate and lithium bis(trifluoromethylsulfonyl)imide. The incorporation of low-molecular-weight carbonates increased the ionic conductivity with maintaining 2D nanostructures in the LC state. High-power performances at relatively high current densities induced by higher ionic conductivities have been achieved by LC electrolytes with low-molecular-weight carbonates. Furthermore, room-temperature operation of LIBs using LC electrolytes is reported for the first time. In the research field of electrolytes for LIBs, we demonstrate the progress of a new category of LC electrolytes.

Supramolecular Association and Nanostructure Formation of Liquid Crystals and Polymers for New Functional Materials

“…(68-70) Two-dimensional self-assembled ion-conductive pathways were obtained with a rod-like LC molecule 21 having a cyclic carbonate moiety and mixing it with lithium bis(trifluoromethylsulfonyl)imide (Figure 8b) (68). Low-molecular-weight ethylene carbonate or propylene carbonate were incorporated which increased the ionic conductivity while maintaining 2D nanostructures in the LC state (69). Recently, we reported that LC Li-ion conductors with high oxidation resistance were achieved based on a bicyclohexyl mesogen using DFT (Density Functional Theory) calculation.…”

Nanostructured liquid-crystalline Li-ion conductors with high oxidation resistance: molecular design strategy towards safe and high-voltage-operation Li-ion batteries

“…These properties are advantageous for versatile large-scale applications, especially for portable and exible electronics. Recently, ion-transport materials based on liquid crystals have attracted much attention [8][9][10] as organic-based quasi-solid electrolytes that can reduce inherent risks associated with liquid organic electrolytes, for example, leakage, evaporation and combustion. Furthermore, solid and quasi-solid electrolytes suppress dendrite formation that causes short circuiting during chargedischarge reactions.…”

“…25,26 We have designed liquid-crystalline (LC) molecules having high miscibility with ionic salts and ion conductive properties for use as quasi-solid electrolytes in dye-sensitized solar cells 16 and Li-ion batteries. 9,10 Nanosegregation between polar and non-polar mesogenic moieties provide efficient ion-conductive pathways in the LC nanostructures 8,27 as well as high boiling point and desired viscosities owing to molecular interactions (Fig. 1).…”

Bicontinuous Cubic and Hexagonal Columnar Liquid Crystalline Ion-Conductors at Room Temperature in Ion-Doped Dendritic Amphiphiles

“…In particular, crystallization between aromatic groups prevents the Cub bi phase from being obtained at RT. Considering its practical use, the complete suppression of crystallization would be ideal [25].…”