Examining the Electrochemical Properties of Hybrid Aqueous/Ionic Liquid Solid Polymer Electrolytes through the Lens of Composition‐Function Relationships

Abstract

Solid polymer electrolytes (SPEs) have the potential to meet evolving Li‐ion battery demands, but for these electrolytes to satisfy growing power and energy density requirements, both transport properties and electrochemical stability must be improved. Unfortunately, improvement in one of these properties often comes at the expense of the other. To this end, a “hybrid aqueous/ionic liquid” SPE (HAILSPE) which incorporates triethylsulfonium‐TFSI (S2,2,2) or N‐methyl‐N‐propylpyrrolidinium‐TFSI (Pyr1,3) ionic liquid (IL) alongside H2O and LiTFSI salt to simultaneously improve transport and electrochemical stability is studied. This work focuses on the impact of HAILSPE composition on electrochemical performance. Analysis shows that an increase in LiTFSI content results in decreased ionic mobility, while increasing IL and water content can offset its impact. pfg‐NMR results reveal that preferential lithium‐ion transport is present in HAILSPE systems. Higher IL concentrations are correlated with an increased degree of passivation against H2O reduction. Compared to the Pyr1,3 systems, the S2,2,2 systems exhibit a stronger degree of passivation due to the formation of a multicomponent interphase layer, including LiF, Li2CO3, Li2S, and Li3N. The results herein demonstrate the superior electrochemical stability of the S2,2,2 systems compared to Pyr1,3 and provide a path toward further enhancement of HAILSPE performance via composition optimization.

Ion and Water Dynamics in the Transition from Dry to Wet Conditions in Salt-Doped PEG

“…While significant progress has been made in understanding ion transport mechanisms in the extremes of dry polymeric electrolytes and highly swollen polymer membranes, these fields have generally been developed independently, leading to knowledge gaps regarding transport in low- to moderately hydrated polymer systems. Recently, significant interest has arisen in such a regime for energy storage applications. − For example, aqueous solid polymer electrolytes (polymer and water-in-salt electrolytes) exhibit high ionic conductivities, preferential lithium transport, and improved safety compared to solid polymer electrolytes, as well as improved electrochemical stability compared to salt-in-water electrolytes . The ability to control ion permeation and ionic conductivity in low to moderately hydrated polymer systems hinges on developing fundamental insights into the interplay between ion–ion, ion–polymer, and ion–water interactions and the role of ion-polymer solvation on ion transport in the transition between “dry” and “hydrated” polymer systems.…”

Engineering High-Performance Li Metal Batteries through Dual-Gradient Porous Cu-CuZn Host

“…Lithium (Li) metal anodes (LMAs) represent a promising energy storage technology based on electrochemical conversion reactions, offering a theoretical specific capacity of up to 3860 mAh g –1 , surpassing conventional Li-ion intercalation chemistry. − This surpasses the gravimetric capacity offered by conventional Li-ion intercalation chemistry, playing a pivotal role in advancing high-energy-density battery systems. − However, the progress of LMAs faces two primary challenges: the nonuniform nucleation and deposition behavior of Li metal, as well as the subsequent growth of Li dendrites resulting from these processes. − Researchers have extensively explored strategies to stabilize LMAs, encompassing anode structure design, − anode interface engineering, − separator engineering, − and electrolyte modification. − Through these efforts, the growth model of Li dendrites has been essentially elucidated. The suppression of Li dendrites and the development of techniques for inducing uniform nucleation/deposition of metallic Li have made significant advancements and garnered widespread consensus. − …”