Polymerized ionic liquids with guanidinium cations as host for gel polymer electrolytes in lithium metal batteries

Abstract

Polymerized ionic liquids (PILs) having guanidinium cations with different counter-anions, such as PF 6− and N(CF 3 SO 2 ) 2 − (TFSI − ), were synthesized by copolymerization of a guanidinium ionic liquid monomer with methyl acrylate followed by an anion exchange reaction. Furthermore, incorporating a guanidinium ionic liquid, LiTFSI salt and nano-size SiO 2 , a quaternary gel polymer electrolyte based on one of the PILs as the polymer host was prepared. The quaternary gel polymer electrolyte was chemically stable even at a higher temperature of 80 • C in contact with the lithium anode. In particular, the electrolyte exhibited high lithium ion conductivity, wide electrochemical stability window and good lithium stripping/plating performance. Li/LiFePO 4 batteries with the quaternary gel polymer electrolyte at 80 • C had capacities of 140 and 130 mA h g −1 respectively at 0.1 and 0.2 C current rates.

Application of quaternary polymer electrolyte based on ionic liquid in LiFePO4/Li, Li4Ti5O12/Li and LiFePO4/Li4Ti5O12 batteries

“…The CV results indicate that the polymer electrolyte has an excellent compatibility and electrochemical stability on cathode materials. A similar CV curve was observed previously by other authors[21,58].The(PE2) LiNTf 2 (2.3 wt.%), MePrPipNTf 2 (63.4 wt.%), PVdF (28.8 wt.%), VC (5.5 wt.%) polymer electrolyte was tested in a Li/LiFePO 4 cell. Fig.…”

“…electric vehicles, EVs) [2]. LiFePO 4 has been shown to have excellent performance levels in lithium batteries based upon both polymer electrolytes [21] and liquid electrolytes [50].…”

“…The next approach consists in synthesizing functional polymeric materials through the polymerization of ionic liquid monomers to be used as matrices for polymer electrolyte systems. The increased interest in polymerized ionic liquids (PILs) is due to their comparatively high ionic conductivity and good mechanical strength [21,22]. Various polymers such as PEO [23][24][25][26][27][28][29][30][31], homo-and co-polymers of poly(vinylidene fluoride) (PVdF) [32][33][34][35][36][37] and poly(ethylene glycol) dimethyl ether [38] have been used to prepare polymer electrolytes with ionic liquids and have been studied over the last few years.…”

Preparation of polymer electrolytes based on the polymerized imidazolium ionic liquid and their applications in lithium batteries

“…Li/LiFePO 4 batteries with the electrolyte PIL‐IL‐0.5 were assembled, and their cycling performances were estimated at 60°C, as shown in Figure . After an initial increase, which may be a result of the generation of improved penetration and contact of the IL component from the electrolyte into the electrode material, the cell discharged a maximum capacity of about 151 mAh g −1 at 0.1 C. In addition, the cell was cycled for 100 cycles with a capacity fading of ∼0.05 mAh g −1 per cycle. After 100 cycles, the discharged capacity of the battery still retained 146 mAh g −1 .…”

“…The gel electrolytes possess higher ionic conductivity as well as good electrode–electrolyte contact and therefore reduced interfacial impedance when compared with solid PIL electrolyte, which makes them more suitable for solid‐state lithium battery applications. In several previous studies, we have prepared a series of gel electrolytes based on various copolymer‐type PILs and incorporating IL, lithium salt, and nanosilica, and their performances in lithium batteries have been evaluated at a high temperature (80°C) . However, at a decreased temperature, the battery performances are not favorable.…”