Electrolyte Solvation Chemistry for the Solution of High‐Donor‐Number Solvent for Stable Li–S Batteries

Abstract

Passivation of the sulfur electrode by insulating lithium sulfide (Li2S) restricts the reversibility and sulfur utilization of lithium–sulfur (Li–S) batteries. Although electrolytes with high donor number (DN) solvents induce tri‐sulfur radical intermediate thus 3D nucleation of Li2S with fast kinetics can be achieved, their catastrophic reactivities with Li metal hinder practical applications. Here, the use of high DN solvent as an additive instead of as co‐solvent to solve their incompatibility between cathode and anode is proposed, by adopting N‐methyl‐2‐pyrrolidone (NMP) as a proof‐of‐concept. Such a strategy is accomplished by the unique solvation structure of the NMP added electrolyte, where the preference of NMP‐Li+ coordination squeezes out partial 1,2‐dimethoxyethane (DME) molecules while enriching 1,3‐dioxolane (DOL) molecules in the first solvation sheath of Li+ ions. It affords the robust SEI on Li metal from corrosion either by NMP or the dissolved polysulfides. Spectral analyses (Raman and UV–vis) also verify that the coordinated NMP additive preserves its S3•− radicals stabilization ability as it does as a co‐solvent, which effectively improves the sulfur conversion kinetics and reversibility. This approach enables competitive capacity retention and a stable cycling performance of 340 cycles, which is one of the longest lifespans known for the high DN solvent involved Li–S batteries.

Unlocking the Low-Temperature Potential of Propylene Carbonate to −30 °C via N-Methylpyrrolidone

“…To better understand the interaction mechanism between PC and graphite, particularly in electrolytes that support reversible Li-intercalation into graphite when a large proportion of PC is present, we selected N -methylpyrrolidone (NMP, DN = 27.3) as another high-donicity cosolvent to pair with PC. NMP, a massively devoured industrial solvent for the electrode manufacturing of Li-ion batteries, is seldomly considered as a solvent in the electrolyte. , Indeed, in this study, we demonstrated that it was incompatible with the graphite anode, by displaying an analogously irreversible cointercalation process to PC. However, an intriguing synergy was discovered when NMP was united with PC: solvent cointercalation disappeared and Li + could be reversibly intercalated into graphite.…”

Rapid Solution Synthesis of Argyrodite-Type Li6PS5X (X = Cl, Br, and I) Solid Electrolytes Using Excess Sulfur

“…Solvents with high polarity (e.g., ACN, dimethylformamide, and dimethyl sulfoxide) induce a dissociation equilibrium in which S 3 •– radical anions are the dominant chemical species . The S 3 •– radical anions are stabilized in highly polar solvents because the Li + –S 2– interaction weakens by competing electrostatic interactions from the solvent. , Taking this into consideration, the presence of EtOH enhances the chemical stability of the polysulfides, particularly, the S 3 •– radical anions, owing to the strong interaction between Li + and EtOH. This is also observed from the UV–vis spectra of 5Li 2 S·P 2 S 5 ·2LiX·15S (X = Br and I) in the THF/ACN/EtOH solvent, as shown in Figure b,c.…”

“…•− radical anions are stabilized in highly polar solvents because the Li + −S 2− interaction weakens by competing electrostatic interactions from the solvent. 26,27 Taking this into consideration, the presence of EtOH enhances the chemical stability of the polysulfides, particularly, the S 3…”

Rationalizing Functionalized MXenes as Effective Anchor Materials for Lithium–Sulfur Batteries via First-Principles Calculations

“…Rechargeable Li–S batteries have been regarded as one of the most promising candidates for next-generation energy storage systems because of their amazing energy density (2600 Wh kg –1 ), high capacity (1675 mAh g –1 ), and abundant sulfur reserves. − However, the commercialization of Li–S batteries is seriously plagued by the “shuttle effect” and sluggish reaction kinetics. − The dissolution of higher-order polysulfides into solvents [lithium polysulfide (LiPS) shuttle] gives rise to severe self-discharge and a low Coulombic efficiency. Furthermore, the slow redox kinetics hinders rapid charging, leads to accumulation of the LiPSs in the solvent, and aggravates the shuttle effect at the same time.…”