## 3 Applications of IL-Based Gels
### Li-Ion Batteries
[37] introduced trimethylolpropane trimethylacrylate (TMPTMA)-based GPE polymerized with LiTFSI, dimethylcarbonate (DMC) and IL tributylmethylammonium bis(trifluoromethanesulfonyl) imide (TBMA-TFSI), which turned out to have the highest ionic conductivity compared to other LiTFSI-polymerized GPEs. Playing with widely developed materials, [PERSON] et al. [50; 51; 52] studied the composition dependency of LiTFSI and P(VDF-HFP) and Pyr\({}_{13}\)TFSI and found the maximal ionic conductivity of these electrolytes. A new introduction was also made this year by [PERSON] et al. to replace IL-based gel electrolytes using IL mixtures in the form of layered heterostructures because they can extend the window while maintaining high ionic conductivity [44]. This is a potential new development for further research. Li-oxygen batteries are batteries that use the oxidation of Li at the anode and the reduction of oxygen at the cathode to induce an electric current. The development of the Li-oxygen GPE battery was initiated by [PERSON] et al. [86] who incorporated the zwitterionic (ZI) sulfobetaine functional group into the IL EMIMTFSI supported by a polymer scaffold. ZI forms dipole-dipole interactions and ion-dipole interactions between them and the ILG, which promote the formation of physical polymer cross-links and the dissociation of IL cation/anion pairs, thereby increasing the ionic conductivity but still being able to maintain the thermal stability of the liquid. Then, in 2020, [PERSON] et al. [87] explored ZI (N-methyl-N-(propane sulfonate) pyrrolidinium (MPSP)) in Li-Oxygen GPE batteries. They used a poly(methyl methacrylate) (PMMA) and the same IL containing ZI as previously reported. In Li-metal batteries, only a few studies have been reported in the last 6 years: by [PERSON] et al. in 2016 and [PERSON] et al. in 2018 focusing on GPE; by [PERSON] et al. in 2019 with their improved organic-inorganic IL-based gel; and by [PERSON] et al. in 2020 who summarized the IL-based gel electrolyte-based hybrid of polymer/inorganic [34]. The GPE made by [PERSON] et al. [88] was carried out in two steps: membrane synthesis P(VDF-HFP)(SiO\({}_{2}\)-like silica airgel)-(butanone)(NMP) and membrane activation by immersion in diethyl ether for 24 h in 1 M LiTFSI solution in 1-ethyl- 3-methylimidazolium trifluoromenthanesulfonate/ethylene carbonate/propylene carbonate (EMITFSI/EC/PC), which produced a nonflammable GPE IL-based gel with lower strength than that proposed by [PERSON] et al. [48]. They proposed a solution for the growth of Li dendrites by exploiting the strength of the ion-dipole interaction between the immobilized IL imidazolium (EMIMTFSI and GPE polysulfides (P(VDF-HFP)). This IL-GPE battery is auto rechargeable. The organic-inorganic electrolyte IL-based gel electrodes with semi-interpenetrated networks are designed for flame retardance, non-volatility, 83% capacity retention after 1000 cycles, and various other safety improvements because [PERSON] et al. considered traditional organic liquid electrolytesimpractical and with low physicochemical properties. They combined Poly(IL), LiTFSI, GPOSS (cross-linker), and [EtO(CH\({}_{2}\))\({}_{2}\)MMI]TFSI dissolved in acetone onto glass fiber (GF) [89]. Practicality is also the reason why, in the following year, [PERSON] et al. [34] made a summary on a polymer/inorganic hybrid electrode (HE).