A Dual‐Phase Electrolyte for High‐Energy Lithium–Sulfur Batteries

Abstract

Dissolution of lithium polysulfides (LiPSs) is essential for fast cathode kinetics, but detrimental for anode stability, especially under lean electrolyte conditions. In this work, the phase separation phenomenon between solvents with different polarities (tetramethyl sulfone [TMS] and dibutyl ether [DBE]) is utilized to enable the design of a dual‐phase electrolyte. High‐polarity, high‐density TMS–lithium bis(trifluoromethanesulfonyl)imide–ammonium trifluoroacetate as the cathode electrolyte strongly solvates LiPSs, which propel the sulfur redox reaction. Moreover, the composite of DBE and a polymeric ion conductor serves as the anode electrolyte. The addition of DBE in the anode side effectively prevents the crossover of corrosive species (LiPSs and ammonia trifluoroacetate), enabling a significant improvement in Li‐metal anode stability. The electrode‐specific dual‐phase electrolyte design provides electrochemical performance superior to conventional electrolytes. Without additional electrode engineering, pouch cells assemble with the dual‐phase electrolyte cycle under a lean electrolyte (4 µL mg−1) and low‐Li‐excess condition (N/P = 3) for 120 cycles.

Kinetically Favorable Li–S Battery Electrolytes

“…In another study, Ren et al proposed an upgraded dual-phase electrolyte with complete phase separation, which is achieved by the combination of low-density dibutyl ether (DBE) and highdensity tetramethyl sulfone (TMS). 103 Although the TMS with high polarity and donicity will improve the dissolution of polysulfides, the DBE is capable of restraining their diffusion and shuttling toward the Li anode side, thereby alleviating the metallic corrosion and enhancing the interfacial stability (Figure 9d). Besides, the addition of DBE did not change the initial color of the NH 4 + -containing polysulfide solution (Figure 9e), which is located at the upper area and exhibits a good phase separation effect.…”

“…(f) Cycling performance of Li–S batteries equipped with dual-phase and single-phase electrolytes. Reproduced with permission from ref . Copyright 2022 Wiley-VCH.…”

Principles and Design of Biphasic Self‐Stratifying Batteries Toward Next‐Generation Energy Storage

“…Such design eliminated the crossover problem of corrosive electrolyte additive (NH 4 TFA) and dissolved active species (lithium polysulfides, LPS), enabling a stable NABSB based on the high-energy lithiumsulfur chemistry. [73] Jiang et al developed an intrinsically nonaqueous BSSE based on fluoroethylene carbonate and ionic liquids. Good cycle stability was achieved in such NABSB with lithium anode and TEMPO cathode (Figure 5d).…”

“…Reproduced with permission. [73] Copyright 2022, Wiley-VCH. (d) NABSB based on IL (BMP-TFSI) and fluoroethylene carbonate involved the utilization of Tri-TEMPO and lithium anode as the electrode pair, enabling a high-voltage and high-energy BSB system.…”

Starving Free Solvents: Toward Immiscible Binary Liquid Electrolytes for Li‐Metal Full Cells

“…To address this issue, several approaches have been explored, including the introduction of solid electrolyte interlayers [14,15] or thick glass fiber membranes [16,17] between the two liquid electrolytes, and the gelation of liquid electrolytes. [18][19][20] However, these approaches often encounter an unwanted increase in the thickness of the solid electrolyte interlayers, glass fiber membranes, and gel electrolytes and interfacial contact resistance between heterolayers, as well as a decrease in the bulk ionic conduction, which result in the loss of energy densities, rate capability, and cycling retention of resulting cells. Therefore, developing a new binary electrolyte that can fulfill the nonidentical electrochemical requirements of cathodes and anodes without impairing physicochemical properties and electrochemical performances of the cell is required.…”