Solvent-free lithium and sodium containing electrolytes based on pseudo-delocalized anions

Abstract

Synthesis and characterisation of super-cooled solvent-free liquid electrolytes for Li and Na batteries.

Engineering Sodium-Ion Solvation Structure to Stabilize Sodium Anodes: Universal Strategy for Fast-Charging and Safer Sodium-Ion Batteries

“…Rechargeable sodium-ion batteries are a promising candidate to replace current lithium-ion batteries (LIBs) due to their reduced cost and global availability. − However, the energy density of Na-ion batteries is only about 50% of LIBs, which is the main bottleneck for their large-scale applications. − This lower energy density adds to the cost of packaging materials since the Na-ion battery size has to be bigger than LIBs to store the same energy. , Great effort has been devoted to using sodium metal as the anode in mobile-ion batteries. − However, the poor Coulombic efficiency (CE) and large irreversibility of the Na + plating/stripping processes lead to severe sodium anode consumption upon cycling, which shortens the lifetime of the battery. − Although many strategies have been reported to enhance the battery performance such as nanostructural control, modification of current collectors and/or sodium anodes, and increased electrolyte concentration (i.e., so-called superconcentrated electrolyte), the CE and cycle life of the battery remain unsatisfactory. ,,,− Therefore, a new approach is needed to achieve significant improvement in Na-ion battery performance.…”

Water-in-Bisalt Electrolyte with Record Salt Concentration and Widened Electrochemical Stability Window

“…LiTFSI was bought from Solvionic (99+%) while LiMM3411 was synthesized as described elsewhere. 9 Both salts were dried overnight under vacuum before use. Thermogravimetric analysis (TGA) was performed on ca.…”

“…−58 °C (Figure a), the WiBS electrolyte is highly viscous at room temperature (without any crystallization observed for weeks). Yet as compared with the dry system, the ionic conductivity is much higher, reaching ca. 0.33 mS cm –1 at 25 °C and 2.83 mS cm –1 at 80 °C (Figure b).…”

“…The key characteristic of the LiMM3411 salt is its capacity to effectively prevent the crystallization of LiTFSI, allowing the preparation of the present WiBS electrolytes. We have previously shown 9 that other related anions also share this property and thus may be applied to produce WiBS electrolytes. Even further, the basic design of this anion family allows for the facile modification of its different side chains to produce different decomposition products at the electrode surface.…”

“…With this in mind, the standard LiTFSI salt and the previously reported LiMM3411 salt (Figure ) − were combined to create a WiBS electrolyte of extremely high lithium salt concentration: 31.4 m (mol kg –1 ) LiTFSI + 7.9 m LiMM3411. This is the first example of using a large nonfluorinated anion for WiSEs and WiBS electrolytes.…”