## 2 Preparation of IL-Based Gel
### Classification of Preparation Methods
#### 2.1.2 Polymerization Method
To fabricate the IL-based gel electrolyte, the P(VDF-HFP), EMIMTFSI IL, and SiO\({}_{2}\) were dissolved in acetone by stirring at 40\({}^{\circ}\)C for 3h. The LiTFSI was added to the solution and stirred for 10 min. Finally, the obtained solution was casted on to a polytetrafluoroethylene mold and dried at 70 \({}^{\circ}\)C overnight and the IL-based gel electrolyte was stored in a glovebox. Recently, [PERSON] and colleagues demonstrated the preparation of IL-based gel electrolyte consisting of P(VDF-HFP) dissolved in acetone, EMIMBF\({}_{4}\) IL, and bis(trifluoromethane) sulfonimide sodium (NaTFSI) salt with different dosages of IL [55]. A significant improvement in the conductivity of the IL-based gel electrolyte was realized by increasing the IL content in the electrolyte. These findings were in good agreement with the experimental results described in previous reports [47; 53]. Meanwhile, by utilizing a simple solution casting method, [PERSON] and colleagues developed a redox-active IL-based gel composed of 1-butyl-3-methylimidazolium iodide (BMIMI) IL, PVDF-HFP, and carbon nanotubes (CNTs) for application in supercapacitors [56]. Figure 2: (a) Synthesis HP-A and IL-based gel from HP-A by photopolymerization [44] and (b) basic overview of polymer/inorganic hybrid electrolyte (HE) [34]. IL-based gels, which are composed of polymeric gelators and ILs, are another potential platform that can offer many possible approaches, with vast research scopes. The properties of the co-polymer gelators are a critical parameter that is directly related to gel performance [57; 58; 59; 60; 61]. Gelation should be accomplished with the lowest quantity of polymer possible to generate highly conductive gels. Thus, coherent molecular design is required to include both IL-soluble and IL-insoluble components [59; 60; 61]. When combined with IL, the IL-soluble segments swell, forming ion conductive channels, while the components that are insoluble in ILs aggregate to limit enthalpically unfavorable interaction with the ILs. Various copolymers such as block [62; 63; 64; 65], star [57; 58], and random [59; 60; 61] types of ion gel have been proposed based on these requirements. Other methods for IL-based gel preparation, namely solvent exchange, click reaction, electrostatic interactions, electro-spinning, 3D printing, H-bonding, mechanical ball milling, and roller pressing, are available in the literature [15; 66; 67; 68; 69; 70; 71; 72]. Figure 3 shows different methods of obtaining IL-based gels. There are still some challenges in the development of IL-based gels due to limitations of the network, such as fewer free ions in IL-based gels, which leads to lower conductivity of the gel electrolytes compared to pure ILs. In addition, a humid environment causes an unstable electrical performance of the IL-based gels containing hydrophilic ILs and polymer chains. However, with the recent development of technology, a large number of IL-based gels have been successfully developed by various preparation methods for application in energy storage and flexible wearable electronics. Although each method offers various advantages such as simplicity, facile synthesis/preparation route, high ionic conductivity, and good performance, several issues are still present in each method. For example, the sol-gel and solvent-casting techniques have a lengthy drying step and the presence of residual solvent, both of which may be detrimental  
Figure 3: (**a**) Locking 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA) IL in poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (PAMPS)-based DN network through electrostatic interactions [70; 71]. (**b**) Forming polyimide ionogels by solution displacement attributed to hydrogen bonding [72]. (**c**) Locking EMIMTFSI IL into the PEA elastomer network through hydrogen bonding [39]. (**d**) The thiol–ene click reaction for preparing DN click ionogel [68]. to battery performance and safety [7].