Suppression of Water Absorption by Molecular Design of Ionic Liquid Electrolyte for Li–Air Battery

Abstract

revealed that solvate ILs are suitable candidates for Li-S battery electrolytes because they greatly suppress the dissolution of lithium polysulfides [10] due to the formation of the complexes which can weaken the donor ability of the ethers. We have also studied solvate ILs as electrolytes for the Li-air battery. [11] Regarding the design of a future energy storage device based on the nonaqueous lithium-air system, a closed system using pure oxygen within a pressure vessel was proposed. However, an open system is more desirable with respect to high energy density if ambient air can be used as the cathode active material. [12] In this study we focus on overcoming one of the main limitations of this "open" design, namely, the possibility for moisture, as well as CO 2 , from ambient air to react with lithium metal at the anode and also to deteriorate the cathode reaction. [13][14][15][16][17] Most existing reports concern battery experiments under dry conditions, which would incur large energy losses upon removal of moisture to obtain dry gas. [18] Hence a lithium conducting glass-ceramic is known to be a desirable material to protect the lithium metal from moisture. [19,20] However, the cathode reaction would still be deteriorated when employing anode protection. Also hydrophobic membranes that block moisture but permeate O 2 , [21] for example, a commodity polymer [22] such as polytetrafluoroethylene or immobilized liquid membranes [23,24] and other hydrophobic layers [25] have been studied for application with ambient air instead of dry air (O 2 ) as the cathode active material. These strategies can delay the ingress of water vapor, but water absorbed to the electrolyte (i.e., the equilibrium moisture content upon prolonged exposure of the device to humid air) cannot be eliminated in the long term. [26] Hydrophobic ionic liquids offer another potential solution. In order to limit the inherent equilibrium moisture content of the battery, careful consideration of the molecular design of the electrolyte is needed. Considering ionic liquids, both anion and cation can affect the sorption of moisture as previously reported. [27] [TFSA] is known to be a relatively hydrophobic anion, [28] but when applied in the previously reported solvate ILs, such as [Li (G4)] [TFSA], the resulting electrolyte absorbs a considerable amount of water. The equilibrium moisture content in [Li(G4)][TFSA] is more than 25 wt% at 30 °C and 90% RH, corresponding to a molar ratio of H 2 O to Li[TFSA] ([H 2 O]/[Li]) of about 9.9. So it is unlikely that [Li(G4)][TFSA] can be applied as the electrolyte forIn this study, the effect of water on the oxygen reduction reaction is initially investigated in aprotic ionic liquids by cyclic voltammetry, revealing that the presence of water significantly deteriorates the reversibility of the oxygen reduction reaction and oxygen evolution reaction, which will be detrimental to performance of a practical lithium-air battery. In order to prevent moisture intrusion from ambient air, a hydrophobic electrolyte is...

Electrolytes for Rechargeable Lithium–Air Batteries

“…This battery showed reversible ORR and OER characteristics, analogous to that of batteries with aprotic electrolytes . A [Li(TEGDME(G4)) 1 ][TFSI] solvate IL showed quasireversible ORR and OER behavior and high oxidative stability up to 4.5 V versus Li/Li + . However, subsequent work revealed that the presence of water markedly deteriorated the reversibility of the Li–air battery.…”

“…[140] A[ Li-(TEGDME(G4)) 1 ][TFSI] solvate IL showed quasireversible ORR and OER behavior and high oxidative stability up to 4.5 Vv ersus Li/Li + . [141] However,s ubsequent work revealed that the presence of water markedly deteriorated the reversibility of the Li-air battery.T op revent moisture intrusion from ambient air, several hydrophobic electrolytes were designed by mixing the solvate ILs with other hydrophobic ILs.The moisture content in the electrolyte exposed to ambient air was greatly suppressed and the reversibility of the Li-air battery was improved using this design. Adams et al [142] proposed an ew lithium ether derived chelate using a2 ,3-dimethyl-2,3-dimethoxybutane (DMDMB) complex with LiTFSI to form as table [(DMDMB) 2 Li]TFSI salt for use in Li-O 2 batteries.T his salt is compatible with Li anodes and its ether-based framework is more stable than simple glymes against O 2 À -initiated hydrogen abstraction.…”

Elektrolyte für wiederaufladbare Lithium‐Luft‐Batterien

“…Diese zeigte reversible ORR‐ und OER‐Eigenschaften, die analog zu denjenigen von Batterien mit aprotischen Elektrolyten waren . Die Solvat‐IL [Li(TEGDME(G4)) 1 ][TFSI] zeigte quasi‐reversibles ORR‐ und OER‐Verhalten und eine hohe Oxidationsstabilität von bis zu 4.5 V gegen Li/Li + . Allerdings ergaben die nachfolgenden Arbeiten, dass das Vorhandensein von Wasser die Reversibilität der Li‐Luft‐Batterie deutlich verschlechtert.…”

Nanomaterials‐Based Surface Protein Imprinted Polymers: Synthesis and Medical Applications

“…[ 58 ] Therefore, finding functional monomers and cross‐linkers that maintain protein activity has become a research hotspot in recent years. [ 59,60 ] Ionic liquids (ILs), usually composed of organic cations and inorganic or organic anions, are functional materials that exist in an ionic state at room temperature. [ 61,62 ] ILs have multiple interactions with template molecules, thereby making prepared imprinted materials have better thermal stability and structural adjustability.…”