Chelate Effects in Glyme/Lithium Bis(trifluoromethanesulfonyl)amide Solvate Ionic Liquids, Part 2: Importance of Solvate-Structure Stability for Electrolytes of Lithium Batteries

Citations Over TimeTop 1% of 2014 papers

Abstract

Highly concentrated, molten mixtures of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and ether solvents (tetrahydrofuran (THF), monoglyme (G1), diglyme (G2), and triglyme (G3)) were investigated as electrolytes for Li batteries. To compare the electrochemical reactions in the electrolytes with different solvents, the ratio of ether–oxygen atoms and Li+ ([O]/[Li]) in the electrolytes was fixed at four. The capacity of a Li–LiCoO2 cell with [Li(THF)4][TFSA] dramatically decreased upon charge/discharge cycling, whereas [Li(G3)1][TFSA] allowed the cell to have a stable charge–discharge cycles and a Coulombic efficiency of greater than 99% over 100 cycles. Corrosion of the Al current collector of the cathode was also affected by the composition of the electrolytes. Persistent Al corrosion took place in [Li(THF)4][TFSA] and [Li(G1)2][TFSA], which contain shorter ethers, but the corrosion was effectively suppressed in [Li(G3)1][TFSA]. Furthermore, lithium polysulfides, which are formed as discharge intermediates at the sulfur cathode of the Li–S cell, were much less soluble in electrolytes with longer ethers. Therefore, a higher Coulombic efficiency and more stable cycle ability were achieved in Li–S cells with [Li(G3)1][TFSA]. All the electrochemical properties in the batteries were dominated by the presence or absence of uncoordinating solvents in the concentrated electrolytes. This paper demonstrates that the structural stability of [Li(glyme or THF)x]+ cations in electrolytes plays an important role in the performance of Li batteries.

Related Papers

• → Reactivity of the europium hexafluoroacetylacetonate (hfac) complex, Eu(hfac)3(diglyme), and related analogs with potassium: formation of the fluoride hfac “ate” complexes, [LnF(hfac)3K(diglyme)]2(2002)73 cited
• → Polyether Adducts of d‐Block Metal Compounds as Starting Materials for New Cluster Compounds(2010)22 cited
• → Novel fluorenyl alkali metal DIGLYME complexes: synthesis and solid state structures(2002)35 cited
• → Synthesis and structure of the diglyme-bridged lead hexafluoroacetylacetonate complex [Pb(hfac)2(μ-η3:η1-diglyme)]2(2006)16 cited
• Study on Syntheses and Characterizations of Polymethylphenethylsilane, Polymethylcyclohexylsilane and their Copolymers(2000)