Elastic ionogels with freeze-aligned pores exhibit enhanced electrochemical performances as anisotropic electrolytes of all-solid-state supercapacitors

Abstract

Bio-inspired by bone materials, hierarchical porous materials with aligned structure have been designed and applied in various fields. However, the realization of anisotropic function based on aligned structures is still a challenge. Herein, we prepare nanocomposite ionogel electrolytes with aligned porous structures via a directional freezing of BMIMPF₆, PEGMA (PEGDA), and TiO₂ at −18 °C and further TiO₂-initiated cryopolymerization under UV irradiation. The crystals of PEG derivatives at −18 °C provide a directional template for the formation of aligned porous structures within the ionogel networks. The additional TiO₂ nanoparticles, as photoinitiators and nanofillers, endow the aligned ionogels with high mechanical strength. The aligned ionogel-based supercapacitor exhibits anisotropic electrochemical performance and flexibility. The specific capacitance of the device with the vertically aligned ionogel is 172 F g⁻¹ at the current density of 1 A g⁻¹, which is larger than those of the parallel aligned and non-aligned devices.