Ionic liquid-based sodium ion-conducting composite gel polymer electrolytes: effect of active and passive fillers

Abstract

We report the studies on composite gel polymer electrolytes (GPEs) comprising 0.5 M solution of sodium trifluoromethane sulfonate (Na-triflate or NaTf) in ionic liquid 1-ethyl 3-methyl imidazolium trifluoromethane sulfonate (EMITf) entrapped in poly (vinylidinefluoride-cohexafluoropropylene) (PVdF-HFP) dispersed with passive filler Al 2 O 3 and active filler NaAlO 2 particles. The freestanding films of the composite GPEs, prepared from solution-cast method, offer optimum ionic conductivity at room temperature (6.3-6.8 × 10 − 3 S cm − 1 and 5.5-6.5 × 10 −3 S cm −1 for Al 2 O 3 -and NaAlO 2 -dispersed GPEs, respectively), with sufficient electrochemical stability and excellent thermal stability up to 340°C. As observed from XRD and SEM, the composites are of predominantly amorphous and porous character, which support the high ionic conduction. The sodium ion transport number has been found to be ∼0.27 for Al 2 O 3 -dispersed GPE and 0.42 for NaAlO 2 -dispersed GPE, which indicates the predominant role of passive and active fillers, Al 2 O 3 and NaAlO 2 , respectively. The dispersion of NaAlO 2 enhances the sodium ion conductivity in composite GPE substantially. The overall ionic conductivity is same as in the case of Al 2 O 3 dispersion. The performance characteristics of GPE, particularly, dispersed with active filler NaAlO 2 show its potential applicability as electrolyte/ separator in sodium batteries.

Electrolytes and Interphases in Sodium‐Based Rechargeable Batteries: Recent Advances and Perspectives

“…Kumar and Hashmi [ 215 ] reported in 2010 a GPE with an ionic conductivity of 5 × 10 −3 S cm −1 , obtained by a mixture of PVdF‐HFP, 1‐ethyl 3‐methyl imidazolium trifluoromethanesulfonate (EMIMTf) and sodium triflate (NaTf). Hashmi and co‐workers [ 216 ] described a similar GPE composition (PVdF‐HFP:EMIMTf:NaTf) while incorporating Al 2 O 3 and NaAlO 2 particles as ceramic fillers reporting a conductivity of 6.3–6.8 × 10 −3 S cm −1 and 5.5–6.5 × 10 −3 S cm −1 for Al 2 O 3 and NaAlO 2 dispersed GPEs respectively. The use of ceramic filler greatly improved the mechanical stability of the GPE.…”

Recent Advances in Poly(vinylidene fluoride) and Its Copolymers for Lithium-Ion Battery Separators

“…In some cases, nanoparticles are added to the matrix as fillers to increase its mechanical stability or ionic conductivity. In composites separators, the most widely used fillers are oxide ceramics (ZrO 2 [ 12 , 13 ], Al 2 O 3 [ 14 , 15 ], SiO 2 [ 16 , 17 ]), carbonaceous fillers (graphene [ 18 ], carbon black [ 19 ], carbon nanofiber [ 20 ]), and ionic liquids [ 21 ], among others.…”

“…A comparative study of Al 2 O 3 and NaAlO 2 particles in a gel polymer electrolyte proved that NaAlO 2 membranes present higher ionic conductivity than Al 2 O 3 , as well as improved mechanical properties [ 14 ].…”

Nanocomposite Ionogel Electrolytes for Solid‐State Rechargeable Batteries

“…[36][37][38] Moreover, NIEs based on hydrophobic nanoparticle matrices and ILs have been utilized for lithium-air batteries to protect the lithium-metal anode from moisture in atmosphere (Figure 3c), thereby improving the lifespan of this open-architecture battery in ambient conditions. [39,40] NIEs have also been explored for rechargeable batteries based on earth-abundant materials such as sodium, [41][42][43][44] zinc, [45,46] and magnesium. [47] For example, a sodium-ion-conducting hybrid NIE based on poly(ethylene oxide), SiO 2 nanoparticles, and EMIM-FSI/NaClO 4 demonstrated solid-state sodium-metal batteries with an initial capacity of 90.5 mAh g −1 at 0.05C at room temperature and a capacity retention of 51% after 100 cycles.…”