Comprehensive Insights into the Reactivity of Electrolytes Based on Sodium Ions

Abstract

We report a systematic investigation of Na-based electrolytes that comprise various NaX [X=hexafluorophosphate (PF6 ), perchlorate (ClO4 ), bis(trifluoromethanesulfonyl)imide (TFSI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI)] salts and solvent mixtures [ethylene carbonate (EC)/dimethyl carbonate (DMC), EC/diethyl carbonate (DEC), and EC/propylene carbonate (PC)] with respect to the Al current collector stability, formation of soluble degradation compounds, reactivity towards sodiated hard carbon (Nax -HC), and solid-electrolyte interphase (SEI) layer formation. Cyclic voltammetry demonstrates that the stability of Al is highly influenced by the nature of the anions, solvents, and additives. GC-MS analysis reveals that the formation of SEI telltales depends on the nature of the linear alkyl carbonates and the battery chemistry (Li(+) vs. Na(+) ). FTIR spectroscopy shows that double alkyl carbonates are the main components of the SEI layer on Nax -HC. In the presence of Na salts, EC/DMC and EC/DEC presented a higher reactivity towards Nax -HC than EC/PC. For a fixed solvent mixture, the onset temperature follows the sequence NaClO4 <NaFTFSI<NaPF6 <NaTFSI<NaFSI, and the total heat generated increases in the order NaFSI<NaTFSI<NaClO4 <NaPF6 <NaFTFSI.

Electrolytes for electrochemical energy storage

“…268,269 A systematic evaluation of the intrinsic Al stability in electrolytes based on various NaX [X=PF6, ClO4, TFSI, FTFSI, FSI] salts dissolved in solvent mixtures showed a trend of the Al dissolution increasing in an order of NaPF6 < NaClO4 < NaTFSI < NaFTFSI < NaFSI. 270 When adding 5 wt.% NaPF6 to the base electrolyte, the stability of Al in imide-based electrolytes could be improved, which may be attributed to the formation of a protection passivation layer on the Al surface. Notably, compared to NaClO4 and NaPF6 (see Fig.…”

Exceptional long-life performance of lithium-ion batteries using ionic liquid-based electrolytes

“…33,34 RTILs can be engineered by changing their structure, thus tailoring their properties, in order to contemporarily meet various important needs such as high ionic conductivity, interfacial and electrochemical stabilities as well as thermal stability and low-flammability. 35,36 These features allow the realization of safer electrochemical storage devices such as supercapacitors, [37][38][39] batteries [40][41][42][43][44][45][46][47][48][49][50][51][52][53] and solar cells. 54 Herein, mixtures of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 14 TFSI), N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr 14 FSI), N-methoxy-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 12O1 TFSI) or N-N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEMETFSI) [55][56][57][58] ionic liquids with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt are comparatively evaluated for application as electrolytes in Li-ion batteries (see structural details in Fig.…”

A Water‐Soluble NaCMC/NaPAA Binder for Exceptional Improvement of Sodium‐Ion Batteries with an SnO2‐Ordered Mesoporous Carbon Anode

“…[47,48] Both factorsa re associated with the thermal stabilityo ft he SEI layer. Two key factorsa re of major concern:( i) the exothermic onset temperature, which governs the initial step that triggers af ire/explosion,a nd (ii)the total heat released, which is indicative of the magnitude of reactione nthalpy.…”