Gel Polymer Electrolytes Based on Crosslinked Networks by the Introduction of an Ionic Liquid Crosslinker with Ethylene Oxide Arms

Abstract

The volatility of liquid electrolytes is a major obstacle in the fabrication of efficient lithium-ion batteries that are safe. Solid-state electrolytes such as solid polymer electrolytes have been studied as a potential substitute for liquid electrolytes. However, their practical application is impeded owing to their low ionic conductivity and high interfacial resistance between the electrolyte and electrodes. Herein, we synthesize a novel ionic liquid crosslinker and use thermal crosslinking to prepare a gel polymer electrolyte (GPE), which shows a higher thermal stability than that of liquid electrolytes and a better ionic conductivity than that of solid electrolytes. The crosslinker, IL2, is designed to have a pyrrolidinium-bis­(trifluoromethyl sulfonyl)­amide structure and an acrylate terminal group with an ethylene oxide spacer connected between them. IL2-GPE, which is prepared by in situ thermal crosslinking, shows an ionic conductivity up to 5.37 mS cm–1 and high thermal and electrochemical stabilities. A cell with IL2-GPE sandwiched between a LiFePO4 cathode and lithium anode exhibits a capacity above 160 mA h g–1 and a high rate capability. By combining a crosslinker having four acrylate terminals with the IL2 crosslinker, we obtain HIL2-GPE, whose ionic conductivity is 20% higher than that of IL2-GPE. The HIL2-GPE cell exhibits capacities of 165 and 146 mA h g–1 at 0.1 and 1.0 C, respectively, thereby demonstrating better performance than that of the cell with IL2-GPE. We also prepared a cell using high-voltage cathode LiNi0.6Co0.2Mn0.2O2 (NCM622). The result suggested that the cell based on the GPEs maintained superior long-term stability even with high-voltage cathode materials over 100 cycles.

Apple Pectin-Based Hydrogel Electrolyte for Energy Storage Applications

“…12,35 However, the addition of cross-linking agents to improve the hydrogel's mechanical strength is considered for further studies. 36,37 Rheological tests were performed (Figure S3), in the linear viscoelastic region, on each membrane; the storage modulus G′ in every membrane is higher than the loss modulus G″ showing solid behavior characteristics, explained by the physical and chemical interactions within the hydrogel membrane. 35 A weaker modulus is observed for the AP membrane containing 1 M Li 2 SO 4 , compared to the other membranes: its mechanical modulus is lower [confirming the previous visual observation (Figure 1)].…”

“…No mechanical tests such as tensile or compressive tests could be conducted due to the vulnerability of the hydrogel. The mechanical properties of these hydrogels are not yet optimized in this regard when compared to other examples. , However, the addition of cross-linking agents to improve the hydrogel’s mechanical strength is considered for further studies. , …”

Advances in Electrospun Materials and Methods for Li-Ion Batteries

“…This addition of plasticizers leads to swelling of the solution forming a viscous solution known as the gel polymer electrolyte (GPE). Polyethylene oxide (PEO), poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinyl acetate (PVAc), and polyvinylidene fluoride (PVDF) were the generally used Polymer for GPE [ 61 , 62 , 63 ]. Another method to improve safety was through co-axial electrospinning, where inorganic ceramics are coated on polymers to further improve their mechanical properties and to provide thermal resistance [ 64 , 65 ].…”