A flexible, highly conductive, tough ionogel electrolyte containing LiTFSI salt and ionic liquid [EMIM][TFSI] based on PVDF-HFP for high-performance supercapacitors

Abstract

Ionogel electrolytes (IGEs) with chemical and thermal stability properties have attracted considerable attention for all-solid-state energy storage devices, particularly for high-performance supercapacitors (SCs). However, achieving high conductivity, flexibility, and toughness, as well as deformation and impact resistance in special cases, is challenging with the typical polymer based on ionic liquids (ILs). Here, an effective gelation strategy is proposed for the preparation of free-standing LiTFSI/[EMIM][TFSI]/PVDF-HFP ionogels (IGs) by double-additive induced physical cross-linking. The mechanical and electrochemical properties of the IGs can be synergistically optimized by the cross-linking and entanglement of LiTFSI and [EMIM][TFSI] with the PVDF-HFP network. The target IGs simultaneously exhibit excellent deformation capacity (over 50 %), high ionic conductivity (10.3 × 10−3 S cm−1 at 25 °C), hardness (H: 728.6 kPa), and Young's modulus (E: 11.4 MPa), which can exhibit the specific capacitance of 274. 55 F g−1, energy density of 38.13 Wh kg−1 and maximum power density of 2499.93 W kg−1 in the fabricated symmetric supercapacitor. The results will motivate us to further explore their applications for flexible electronic devices, wearable electronic skin, and flexible energy storage.