## 3 Applications of IL-Based Gels
### Li-Ion Batteries

Table 1: The difference between GPE and OIG. In 2019, the GPE stretch film was again proposed by [PERSON] et al. [49] for battery application with an elongation at break of 178%, a breaking strength of 6.65 MPa, and a high ionic conductivity of 0.80 mS cm\({}^{-1}\). A used IL-based gel component is a mixture of P(VDF-HFP) poured on PyrT\({}_{3}\)TFSI and 0.6 g Li salt LiTFSI + 0.7 g IL PyrT\({}_{3}\)TFSI. In addition, the synthesis of a new family of chemically crossed IL-based gels was introduced by photopolymerization of branched aliphatic polyesters (HP-OH) with terminal acrylic groups [45]. Although quite complex, the results of this IL-based gel can achieve a mechanical strength up to 1.6 MPa, and are mechanically stable up to 200 \({}^{\circ}\)C, thermal up to 371.3 \({}^{\circ}\)C, and have an electrochemical window up to >4.3 V.  
Additionally in 2019, [PERSON] et al. [30] paid attention to the flammable Li-ion battery electrolyte and then made a solution in the form of two types of quasi-solid-state IL-based gel electrolytes (IE-T and IE-B) using the fast sol-gel method and the structure of porous silica. A diamagnetic stirrer of 50 \({}^{\circ}\)C ethanol (EtOH) with Li trifluoromethanesulfonate (LiOTf) salt was used to prepare IE-T or LiTFSI salt to prepare IT-B with tetraethylorthosilicate (TEOS), then this was added to IL BMIMBF\({}_{4}\). After that, it was printed and dried in a vacuum oven. IE-T has richer pores and a stable discharge capacity of 141 mAh g\({}^{-1}\) at 0.1C for more than 100 cycles, whereas IE-B has low coulomb efficiency, poor reversibility, and high impedance. Based on that, IE-T is more secure. Figure 4: Schematic illustration of (a) spin-coating of TMOS/VTEOS IL-based gel electrolyte. (b) GV measurements of different electrolytes on LFP at C/10. Results are shown for gel 1 and gel 2, with the ionic liquid electrolyte (ILE) serving as a comparison (A). The inset shows the dQ/dV versus V curves extrapolated from the GV measurements. (b) Capacity variation with cycling for gel 1. Majority of the 150 cycles were at C/2 (B). Capacity variation with cycling for gel 2. Majority of the 80 cycles were at C/2 (C). Reprinted with permission from ref. [20]. In 2020, three Li-ion battery developments were reported by [PERSON] et al., [PERSON] et al., and [PERSON] et al. [32; 49; 84]. [PERSON] et al. [84] focused on improving the quality of refractory GPE with a simple and scalable phase inversion method. Moreover, poly(1,2-diethoxyylimidazolium TFSI) (PDEIm)/P(VDF-HFP), which they tested directly on wax, also had rollable and scrunchable characters. LiFePO\({}_{4}\)/Li batteries using PDEim/P(VDF-HFP) show superior performance than those using a commercial Celgard 2325 separator saturated with a liquid electrolyte. Meanwhile, [PERSON] et al. [32] made a new breakthrough 40 \(\upmu\)m film mesoporous silica monolith matrix composite (nano-SCE) filled with BMPTFSI nonvolatile IL filler as a solid electrolyte option with Li-TFSI/TEOS salt. Furthermore, [PERSON] et al. [49] paid attention to the thermal stability of Li-ion batteries by separating mechanical strength and ionic conductivity through the non-solvent induced phase separation (NIPS) method to produce an IL-based GPE gel P(VDF-HFP)-N-Methyl-2-Pyrrolidone (NMP)/IL Pyr\({}_{13}\)TFSI/LiTFSI with elongation at break of 178% and high thermal stability up to 220 \({}^{\circ}\)C. In the same year, [PERSON] et al. [53] tested IL-GPE P(VDF-HFP)/PYR\({}_{13}\)FSI/LiTFSI on a LiNi\({}_{0.33}\)Mn\({}_{0.33}\)Co\({}_{0.33}\)O\({}_{2}\) (LNMC) coated Li\({}_{2}\)CuO\({}_{2}\) cathode to study the structural and cyclical stability of the cathode and found a twofold increase in its ionic conductivity compared to [PERSON] et al. [49]. Another report submitted in 2020 by [PERSON] et al. [85] shows the synthesis of tetra-arm poly(ethylene glycol) (TetraPEG) in triethylpentylphosphonium (P\({}_{225}\)) with Li-TFSI salt solution with an increased electrochemical window up to 4.2 V with 95% efficiency. The following year, [PERSON] et al.