Anion-Derived Solid-Electrolyte Interphase Enables Long Life Na-Ion Batteries Using Superconcentrated Ionic Liquid Electrolytes

Abstract

Ionic liquid electrolytes have been utilized in rechargeable batteries, yet their effect on the anode interphase evolution has been barely studied. Herein, we investigate the interfacial characteristics of carbon anodes in sodium-ion batteries (NIBs) in contact with superconcentrated sodium bis(fluoromethane)sulfonimide (NaFSI)/N-methyl-N-propylpyrrolidinium bis(fluoromethane) sulfonimide (C 3 mpyrFSI). A long cycle life of the cell, up to 3500 cycles with 320 mAh/g, is achieved, which is contributed by the anion-derived inorganic solid electrolyte interphase (SEI) layer on the anode. Comparison is made with a traditional carbonate electrolyte using the same sodium salt (1 M NaFSI in EC/DMC), showing that the latter results in a thick organic-dominant SEI layer from decomposition of the organic solvents. Here we correlate the influence of the anion decomposition species in the IL electrolyte with high ionic conductivity, and accelerated Na desolvation and faster diffusion kinetics, giving some fundamental insights into interfacial phenomena in NIBs.

Sustainable Free‐Standing Electrode from Biomass Waste for Sodium‐Ion Batteries

“…The N 1s on the CS_800 °C surface in Figure 3c can be deconvoluted into three peaks at 398.6 eV, 400.6 eV, and 403.6 eV, which are assigned to −NS=O/−N=CO, −N=SO/−NC=O, and N + . The −NS=O and −N=SO species are from the FSI − anion decomposition from the ILs electrolyte, [33,46] whereas the −N=CO and −NC=O are from the functional groups from the pristine sample. It is also noted that N + is observed from the residual C 3 mpyr + that can be etched by the Ar + at 30 s etching depth [47] .…”

“…In this work, a free‐standing hard carbon anode was fabricated by using a silk carbonization procedure reported previously [29] . Two carbonized silk (CS) samples with different annealing temperatures (denoted as CS_800 °C and CS_1300 °C) were examined in superconcentrated ionic liquids (ILs) (3.8 M NaFSI in C 3 mpyrFSI) electrolytes previously suggested for Na battery systems [31–33] . Comparisons of electrochemical performance including cycling and rate capability were undertaken.…”

“…[29] Two carbonized silk (CS) samples with different annealing temperatures (denoted as CS_800 °C and CS_1300 °C) were examined in superconcentrated ionic liquids (ILs) (3.8 M NaFSI in C 3 mpyrFSI) electrolytes previously suggested for Na battery systems. [31][32][33] Comparisons of electrochemical performance including cycling and rate capability were undertaken. Surface functionality, determined by X-ray photoelectron spectroscopy (XPS), indicated more nitrogen and oxygen functional groups on the CS_800 °C surface than on CS_1300 °C.…”

NaFSI and NaTFSI Solutions in Ether Solvents from Monoglyme to Poly(ethylene oxide)—A Molecular Dynamics Study

“…6−14 Several of those works are aimed at the study of highly concentrated salt solutions in search for better performing systems. [11][12][13]15,16 Among the electrolytes using molecular liquids are the systems based on diglyme 17−19 or other short glymes as solventsusually from mono-to pentaglyme. 20−31 There are also studies on polymer-based systems, offering several advantages, such as better mechanical properties and safety.…”

“…Similarly to the Li-based devices, systems investigated as possible electrolytes for Na-ion batteries are sodium salt solutions in molecular solvents, ionic liquids, or mixed solvents. − Several of those works are aimed at the study of highly concentrated salt solutions in search for better performing systems. − ,, Among the electrolytes using molecular liquids are the systems based on diglyme − or other short glymes as solventsusually from mono- to pentaglyme. − There are also studies on polymer-based systems, offering several advantages, such as better mechanical properties and safety. However, conductivity of solid polymer electrolytes is lower than that of liquid systems.…”