Solid electrolyte interphase in water-in-salt electrolytes

Abstract

The water-in-salt strategy successfully expands the electrochemical window of the aqueous electrolyte from 1.23 to~3.0 V, which can lead to a breakthrough in the energy output of the aqueous battery system while maintaining the advantage of high safety. The expanded electrochemical window of the water-in-salt electrolytes can be ascribed to the decreased water activity and the solid electrolyte interphase formed on the anode. The solid electrolyte interphase in the aqueous system is not fully understood, and the basic composition, the structure, and the formation mechanism are still cloaked in mystery. This perspective summarizes the published research with emphasis on the most possible formation mechanism and composition of the interphase layer in the aqueous system. Further understanding of the interphase as well as rounded assessment of the water-in-salt electrolyte in practical operating conditions is encouraged. The full understanding of the interface will guide the design of aqueous electrolytes and help to build novel aqueous batteries with high safety and high energy density.

Metal organic framework optimized hybrid solid polymer electrolytes with a high lithium-ion transference number and excellent electrochemical stability

“…The nite element method (FEM) simulation was used to detect the diffusion distribution of anions and cations in the electrolyte driven by an electric eld. 44,45 As shown in Fig. 7a and S10a, † the PEM10 electrolyte exhibits small concentration gradients for both Li + and anions, which prevents the formation of a large electric eld.…”

Growth Parameters and Diffusion Barriers for Functional High-Voltage Thin-Film Batteries Based on Spinel LiNi0.5Mn1.5O4 Cathodes

“…Notably, the present work focuses on studying the behavior of LNMO deposited by mid-frequency alternating current (AC) magnetron sputtering in an easily accessible substrate, viz., stainless steel (SS), typically used in coin cell configuration as current collector or spacer. 44,49 In stark contrast to the previous study, mostly focused on nonscalable Pt-coated Al 2 O 3 substrates, 50,51 the stability, acceptable electrical conductivity, availability, and low cost of SS make it one of the preferred substrates for building up batteries, ready for scale-up to industrial scale. 52 Nevertheless, chemical and electrochemical compatibility with the cathode material needs to be carefully analyzed since interdiffusion issues during the thermal treatment have been reported in the literature.…”

Tuning the Electrolyte Solvation Structure via a Nonaqueous Co-Solvent to Enable High-Voltage Aqueous Lithium-Ion Batteries

“…With the ubiquitous applications of lithium-ion batteries (LIBs) in our life, the safety concerns over LIBs also increase as the combustions and explosion accidents are frequently reported, which are usually ascribed to the flammable nonaqueous electrolytes used in LIBs. − Aqueous LIBs (ALIBs) that use aqueous electrolytes are fundamentally safe substitutes with additional advantages such as the low cost of electrolyte solvents and the readily assembled environment, yet their energy densities are limited to a low level (usually lower than 70 Wh kg –1 ) due to the narrow electrochemical stability window (ESW) of water. − Recently, a new kind of electrolyte, “water-in-salt” electrolyte (WiSE), was reported. By dissolving 21 m (mol kg –1 ) lithium bis­(trifluoromethane sulfonyl)­imide (LiTFSI) in water, the ESW of water is expanded to 3 V (1.9–4.9 V versus Li + /Li), thus realizing a 2.3 V ALIB with the LiMn 2 O 4 (LMO) cathode and Mo 6 S 8 anode as well as increased energy density .…”