PY₁₃FSI-Infiltrated SBA-15 as Nonflammable and High Ion-Conductive Ionogel Electrolytes for Quasi-Solid-State Sodium-Ion Batteries

Abstract

Exploring electrolytes of high safety is essential to pave the practical route for sodium-ion batteries (SIBs) toward their important applications in large-scale energy storage and power supplies. In this regard, ionogel electrolytes (IEs) have been highlighted owing to their high ionic conductivity, prominent electrochemical and thermal stability, and, more crucially, high interfacial wettability. However, present studies lack an understanding of the interaction of IEs, which determines the ion desolvation and migration. In this article, IEs comprising an SBA-15 host, an ionic liquid, sodium salt, and poly­(vinylidene fluoride)–hexafluoro propylene (PVDF–HFP) have been proposed by mechanical ball milling and roller pressing. The component ratio has been optimized based on the balance between ionic conductivity and self-supporting capability of IEs. The optimal IEs showed sufficiently high ionic conductivity (2.48 × 10–3 S cm–1 at 30 °C), wide electrochemical window (up to 4.8 V vs Na+/Na), and high Na+ transference number (0.37). Due to the presence of SBA-15 and an ionic liquid, the IEs exhibited much improved thermal resistance than that of the conventional organic liquid electrolytes (OLEs). Furthermore, Fourier transform infrared (FT-IR) spectroscopy revealed the hydrogen bonding interaction between silanols and the dissolved salts, not only anchoring anions for immobilization but also promoting the dissociation of sodium salts. After being matched with the Na3V2(PO4)3 (NVP) cathode and metallic Na anode, the SIBs presented a specific discharge capacity of up to 110.7 mA h g–1 initially at room temperature with 92% capacity retention after 300 cycles. The improved safety and electrochemical performance provided insights into rationally regulating IEs and their interactions with the prospect of strengthening their practical applications in SIBs.

Siloxane-Modified, Silica-Based Ionogel as a Pseudosolid Electrolyte for Sodium-Ion Batteries

“…31,32 Another advantage of the sol−gelderived IG synthesis is the ability to tune the pore size and surface functionality of the silica structure. To the best of our knowledge, the only other inorganic IG electrolyte for SIBs was reported by Gao et al 32 In this study, the authors created a physical gel by ball-milling SBA-15 molecular sieves, ILE, and PVDF-HFP binder.…”

Ionic Liquid-Based Electrolytes for Aluminum/Magnesium/Sodium-Ion Batteries

“…Pyrrolidinium-Based Ionic Liquid Electrolytes. Pyrrolidinium-based ionic liquid electrolytes including N-propyl Nmethylpyrrolidinium (Pyr 13 -) and N-butyl-N-methylpyrrolidinium (Pyr 14 -or BMP-) are very attractive for SIB applications [172]. At present, there are mainly two kinds of pyrrolium-based ionic liquid electrolyte systems used in SIBs, namely, NaFSI/Pyr 13 FSI and NaTFSI/BMPTFSI.…”

“…(e) Cyclic stability of Na 0.44 MnO 2 /HC full battery in ionic liquid and organic electrolytes [176]. (f) SEM micrographs of (A) and (C) NMO electrodes and (B and D) HC electrodes taken from (A and B) IL and (C and D) organic electrolyte full cells after 100 cycles [172]. Energy Material Advances electrolyte/anode (hard carbon) interface.…”

Ionic Liquid-Based Gels for Applications in Electrochemical Energy Storage and Conversion Devices: A Review of Recent Progress and Future Prospects

“…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.…”

“…Future perspectives [ 92 ] and suitable materials [ 90 ] for Na batteries have also been explained previously. Starting in 2020, several IL-based gel breakthroughs in Na-ion batteries were also developed, one of which was by Gao et al using polymer-based IL-based gel [ 69 ] and Zheng et al using inorganic-based IL-based gel [ 93 ]. Gao et al reported an electrochemical enhancement of high safety IL-based gels using Pyr 13 FSI comprising SiO 2 -based mesoporous sieve (SBA-15) host as an ionic conductor due to its high conductivity, Na bis(trifluoromethane)-salt sodium sulfonymide (NaTFSI) because of its larger anionic radius than other Na salts, and 12 P(VDF-HFP) as a binder due to its high dielectric constant.…”