Details

Autor(en) / Beteiligte

• Shigenobu, Keisuke
• Shibata, Masayuki
• Dokko, Kaoru
• Watanabe, Masayoshi
• Fujii, Kenta
• Ueno, Kazuhide

Titel

Anion effects on Li ion transference number and dynamic ion correlations in glyme-Li salt equimolar mixtures

Ist Teil von

• Physical chemistry chemical physics : PCCP, 2021-02, Vol.23 (4), p.2622-2629

Ort / Verlag

England: Royal Society of Chemistry

Erscheinungsjahr

2021

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• To achieve single-ion conducting liquid electrolytes for the rapid charge and discharge of Li secondary batteries, improvement in the Li + transference number of the electrolytes is integral. Few studies have established a feasible design for achieving Li + transference numbers approaching unity in liquid electrolytes consisting of low-molecular-weight salts and solvents. Previously, we studied the effects of Li + -solvent interactions on the Li + transference number in glyme- and sulfolane-based molten Li salt solvates and clarified the relationship between this transference number and correlated ion motions. In this study, to deepen our insight into the design principles of single-ion conducting liquid electrolytes, we focused on the effects of Li + -anion interactions on Li ion transport in glyme-Li salt equimolar mixtures with different counter anions. Interestingly, the equimolar triglyme (G3)-lithium trifluoroacetate (Li[TFA]) mixture ([Li(G3)][TFA]) demonstrated a high Li + transference number, estimated via the potentiostatic polarization method ( t PP Li = 0.90). Dynamic ion correlation studies suggested that the high t PP Li could be mainly ascribed to the strongly coupled Li + -anion motions in the electrolytes. Furthermore, high-energy X-ray total scattering measurements combined with all-atom molecular dynamics simulations showed that Li + ions and [TFA] anions aggregated into ionic clusters with a relatively long-range ion-ordered structure. Therefore, the collective motions of the Li ions and anions in the form of highly aggregated ion clusters, which likely diminish rather than enhance ionic conductivity, play a significant role in achieving high t PP Li in liquid electrolytes. Based on the dynamic ion correlations, a potential design approach is discussed to accomplish single-ion conducting liquid electrolytes with high ionic conductivity. Cation-anion interactions and Li ion coordination structure have a significant impact on dynamic ion correlations and Li ion transference number of glyme-Li salt molten mixtures.