Interfacial Chemistry of Perfluorinated-Anion Additives Deciphering Ether-Based Electrolytes for Sodium-Ion Batteries

Abstract

Ether-based electrolytes with high reductive stability can be compatible with multiple anodes. However, their low oxidative stability and low flash point lead to restrictions for sodium-ion batteries. Here we report a rational coupling design between perfluorinated-anion additives and cathode/solvent to self-assemble a protective cathode-electrolyte interphase (CEI) and concurrently build a −C−F•••H−C− stable interaction network to promote the stability of ethers. The preferential adsorption and oxidization of additives enable the electrolyte to restrain weak oxidation at low voltage and withstand high voltage up to 4.5 V vs Na/Na + . Such additives also facilitate uniform Na deposition and inhibit the growth of Na dendrites. The weak −C−F•••H−C− pseudo hydrogen bond developed between additives and solvents contributes to the markedly elevated thermal stability of the electrolyte up to 60 °C. These results highlight the significance of regulating the interfacial environment and solvation effect by sacrificial additives for boosting the electrochemical and high-temperature performance.S odium-ion batteries (SIBs) have been strongly considered as the best potential candidate to replace lithiumion batteries (LIBs) 1,2 because of abundant resources and the similar operating mechanism. 3,4 Increasing application in low-speed electric vehicles and large-scale energy storage is not only gradually boosting the performance of SIBs, 5,6 including high energy density, fast charging, high safety, and long cycle life, but also has placed more harsh requirements on cell components. 7,8 Compared with the considerable development of electrodes, there are more challenges facing the electrolyte because of its complex solvation structure and diverse interface reaction. 9−11 Therefore, exploring advanced electrolytes and regulating essential electrode/electrolyte interfaces are critical to satisfy the high expectations of SIBs.Recent investigations concluded that the ether-based electrolyte with Na + cointercalation mechanism could be suitable for multiple anode materials, such as hard carbon, 12,13 bismuth, 14 and N-heteropentacenequinone. 15 It avoids the sluggish desolvation process and, accordingly, enhances the kinetics. However, not much research has been done on the Na storage mechanism of ether-based electrolytes for cathodes. Unfortunately, the ether-based electrolyte would oxidate constantly at low voltage and decompose violently beyond 4.0 V vs Na/Na + due to the intrinsic resistance deficiency to oxidability. 16 Meanwhile, the low flash point and high flammability of ethers increase thermal risks especially at high temperature (HT), incurring safety concerns and battery degradation. 17,18 Recently, researchers have developed multiple strategies to improve the oxidation and thermal stability of electrolytes, respectively. Zhou et al. 19 designed a 3 Å zeolite molecular sieve film on the cathode to build a highly aggregated solvation structure of ethers through the size effect, extending the oxidative stability to 4.5 V vs...

Sulfur-Containing Inorganic-Rich Interfacial Chemistry Empowers Advanced Sodium-Ion Full Batteries

“…The electrolyte, as a crucial component of SIBs, is closely related to the formation of EEI. , Numerous researchers demonstrated that electrolyte design is an effective strategy for constructing a robust NaF-rich EEI, including high-concentration electrolyte, localized high-concentration electrolyte, , all fluorinated electrolyte, , etc. However, the practical application of these electrolyte systems is limited by their expensive cost.…”