## 3 Applications of IL-Based Gels
### Supercapacitors
polymerized poly(hydroxyethyl methacrylate-co-poly (ethylene glycol) dimethacrylate) copolymer (PHEMA-co-PEGDMA) in EMIMBF\({}_{4}\) under UV irradiation to obtain an IL-based gel electrolyte for flexible SCs with commercially activated carbon (MSP-20) as electrode materials [115]. The synthesized IL-based gels exhibited an ionic conductivity of 12.27 mS cm\({}^{-1}\), which is comparable to pristine ILs. The electrochemical test for SCs' cells showed a good performance by possessing a specific capacitance of 163.17 F g\({}^{-1}\) and retaining 59% of its initial capacitance. A study published in 2017 demonstrated the preparation of a hybrid IL-based gel electrolyte consisting of epoxy-functionalized POSS, amine-terminated polypropylene glycol, and 1 M LiTFSI in BMPTFSI IL for high-temperature LICs [109]. The authors further evaluated the cyclingperformance of the hybrid IL-based gel electrolyte using CR-2032 coin-type cells consisting of a separator, Li metal, and AC electrode at a constant current density of 0.2 C/0.5 C at 80 \({}^{\circ}\)C. The as-designed cell with IL-based gels exhibited excellent cycling behavior with >97% coulombic efficiency. In the following year, 2018, [PERSON] and colleagues developed quasi-solid-state Li-ion-type asymmetric supercapacitors (ASCs) based on \(T\)-Nb\({}_{2}\)O\({}_{5}\)/rGO nanohybrids for the anode, LiTFSI-EMIMBF\({}_{4}\) mixture for the electrolyte, and a P(VDF-HFP)/EMIMBF\({}_{4}\)/LiTFSI IL-based gel separator. They suggested that the \(T\)-Nb\({}_{2}\)O\({}_{5}\)/rGO electrodes have great potential for Li\({}^{+}\) storage [116]. Recently, in 2020, [PERSON] et al. reported optimized solid lithium ion-type ASCs based on a TiNb\({}_{2}\)O\({}_{7}\)@MoS\({}_{2}\)/C anode, AC cathode, and the IL-based gel electrolyte composed of EMIMTFSI IL, LiTFSI salt, P(VDF-HFP), and SiO\({}_{2}\)[54]. From electrochemical performance, the maximum energy density and power density of lithium ion-type ASCs were estimated to be 147.2 Wh kg\({}^{-1}\) and 2470.5 W kg\({}^{-1}\), respectively, at 60 \({}^{\circ}\)C. Similarly, [PERSON] et al. developed TiNb\({}_{2}\)O\({}_{7}\)@carnon nanofiber(CNF)-based LICs exhibiting a superior energy density of 397.3 \(\mu\)Wh cm\({}^{-2}\) with an EMIMBF\({}_{4}\)/P(VDF-HFP)/LiTFSI IL-based gel as the separator [117]. Meanwhile, [PERSON] and coworkers used a P(VDF-HFP)/tetraethylammonium tetrafluoroborate (TEABF\({}_{4}\)) ion gelled, electrospun PVDF/NaNbO\({}_{3}\) nanofibrous mat separator and a 2D-MoSe\({}_{2}\) nanosheets electrode for the construction of self-charging SCs [118]. On the other hand, [PERSON] et al. constructed a new NiO/rGO//AC-based LIC using P(VDF-HFP)-EMIMBF\({}_{4}\)-LiTFSI IL-based gel electrolyte obtained via the solution casting method [104]. Besides LICs, in 2020, [PERSON] et al. introduced solid-state sodium ion capacitors using a MoS\({}_{2}\)/CNT working electrode and sodium foil counter-electrode in P(VDF-HFP)/EMIMBF\({}_{4}\)/NaTFSI IL-based gel electrolyte [57; 58]. The sodium ion capacitors showed profound performances with an outstanding cyclic stability of 81.2% after 8000 cycles at above 30 \({}^{\circ}\)C.  
Meanwhile, [PERSON] et al. assembled high-temperature EDLCs using carbon electrodes and a sol-made IL-based gel composed of EMIMTFSI, TMOS, and DMDMS [29]. From Figure 7a, the TGA thermograms show that the mass of IL-based gel remains unchanged until 350 \({}^{\circ}\)C. A complete degradation observed at about 470 \({}^{\circ}\)C and 440 \({}^{\circ}\)C for EMIMTFSI and IL-based gel, respectively, indicated that IL-based gel exhibits favorable thermal stability. The IL-based gel displayed the ionic conductivity of 4 mS cm\({}^{-1}\) at 20 \({}^{\circ}\)C, which was found to increase to up to 26 mS cm\({}^{-1}\) at 100\({}^{\circ}\)C (Figure 7b).