Does Li-ion transport occur rapidly in localized high-concentration electrolytes?

Watanabe, Yoshifumi; Ugata, Yosuke; Ueno, Kazuhide; Watanabe, Masayoshi; Dokko, Kaoru

doi:10.1039/d2cp05319e

Cited by 28 publications

(27 citation statements)

References 42 publications

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“…43−46 Therefore, the ion-conducting [Li(SL) 2 ][TFSA] phase may be partially isolated in the sea of HFE in a ϕ range lower than 0.5, and the Li + exchange/hopping conduction is obstructed by the non-ion-conducting HFE-rich domains. 27…”

Section: Transport Properties Of [Li(sl) 2 ][Tfsa]-xhfementioning

confidence: 99%

“…A similar phenomenon, where the high Li + transference number is retained and the ionic conductivity is improved, was expected when SL-based HCEs are diluted with non-coordinating HFE. However, in practice, the Li + transference number decreased. ,, This could be attributed to the reduced contribution of the Li + exchange/hopping mechanism to the ionic conduction; however, the practical changes in the ion-transport mechanism and Li + -ion coordination structure remained unclear. Therefore, in this study, we investigated the dilution effect on the Li + transference number and Li-ion coordination structure in SL-based LHCEs.…”

Section: Introductionmentioning

confidence: 99%

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Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

et al. 2023

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Localized high-concentration electrolytes (LHCEs), which are mixtures of highly concentrated electrolytes (HCEs) and non-coordinating diluents, have attracted significant interest as promising liquid electrolytes for next-generation Li secondary batteries, owing to their various beneficial properties both in the bulk and at the electrode/electrolyte interface. We previously reported that the large Li+-ion transference number in sulfolane (SL)-based HCEs, attributed to the unique exchange/hopping-like Li+-ion conduction, decreased upon dilution with the non-coordinating hydrofluoroether (HFE) despite the retention of the local Li+-ion coordination structure. Therefore, in this study, we investigated the effects of HFE dilution on the Li+ transference number and the solution structure of SL-based LHCEs via the analysis of dynamic ion correlations and molecular dynamics simulations. The addition of HFE caused nano-segregation in the SL-based LHCEs to afford polar and nonpolar domains and fragmentation of the polar ion-conducting pathway into smaller clusters with increasing HFE content. Analysis of the dynamic ion correlations revealed that the anti-correlated Li+–Li+ motions were more pronounced upon HFE addition, suggesting that the Li+ exchange/hopping conduction is obstructed by the non-ion-conducting HFE-rich domains. Thus, the HFE addition affects the entire solution structure and ion transport without significantly affecting the local Li+-ion coordination structure. Further studies on ion transport in LHCEs would help obtain a design principle for liquid electrolytes with high ionic conductivity and large Li+-ion transference numbers.

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Section: Transport Properties Of [Li(sl) 2 ][Tfsa]-xhfementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

et al. 2023

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“…The enhanced ionic transport could be attributed to the following two reasons: 1) in 1 m LiFSI-TTE/DME LHCE, the Li + -ligand exchange is interrupted by non-solvating TTE since Li + does not coordinate with TTE (Figure S11a), which dismisses the Li + hopping conduction in HCEs as demonstrated by Dokko's recent study. [31,32] While in our 1 m LiFSI-TFMP/DME electrolyte, since the TFMP solvent can weakly solvate with Li + , the Li + hopping network can be reserved (Figure S11b), which maintains the contribution of Li + hopping conduction that enhances both ionic conductivity and Li + transference number, and 2) the 1 m LiFSI-TFMP/DME electrolyte has lower viscosities than 1 m LiFSI-TTE/DME LHCE at all temperatures (Figure S12), which also contributes to fast ionic transport.…”

Section: Core-shell-solvation Induced High Ionic Conductivity Low Des...mentioning

confidence: 99%

An Amphiphilic Molecule‐Regulated Core‐Shell‐Solvation Electrolyte for Li‐Metal Batteries at Ultra‐Low Temperature

Shi

Lai

et al. 2023

Angew Chem Int Ed

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Lithium metal batteries hold great promise for promoting energy density and operating at low temperatures, yet they still suffer from insufficient Li compatibility and slow kinetic, especially at ultra‐low temperatures. Herein, we rationally design and synthesize a new amphiphilic solvent, 1,1,2,2‐tetrafluoro‐3‐methoxypropane, for use in battery electrolytes. The lithiophilic segment is readily to solvate Li+ to induce self‐assembly of the electrolyte solution to form a peculiar core‐shell‐solvation structure. Such unique solvation structure not only largely improves the ionic conductivity to allow fast Li+ transport and lower the desolvation energy to enable facile desolvation, but also leads to the formation of a highly robust and conductive inorganic SEI. The resulting electrolyte demonstrates high Li efficiency and superior cycling stability from room temperature to −40 °C at high current densities. Meanwhile, anode‐free high‐voltage cell retains 87 % capacity after 100 cycles.

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“…Moreover, voltage decay is not observed for continuous 50–150 cycles, as clearly visualized in differential capacity plots (Figure b inset), which proves the excellent structural durability of Li 2 MnO 1.5 F 1.5 as an electrode material. Although concentrated electrolyte solutions with high viscosity show lower ionic conductivity compared with a conventional electrolyte solution, comparable rate capability is obtained for both electrolyte solutions presumably because of a higher transference number for Li ions for the concentrated electrolyte . Although the electrode reversibility is high enough without voltage decay and suitable for use in practical applications, a remaining problem is found in industrial-scale synthesis of the sample.…”

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confidence: 99%

Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li₂MnO_1.5F_1.5

Kanno,

Ugata,

Ikeuchi

et al. 2023

ACS Energy Lett.

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Li-excess manganese-based oxides have been proposed as high-capacity positive electrode materials, but voltage decay associated with gradual oxygen loss hinders its use for practical applications. Herein, Li-excess manganese oxides with different fluorine contents are synthesized by high-energy mechanical milling. Although Li2MnOF2 with only divalent manganese ions cannot be synthesized, Li2MnO2F and Li2MnO1.5F1.5 are successfully synthesized. When the samples are charged to 5.0 V, both oxyfluorides deliver large reversible capacities, ∼350 mA h g–1 and ∼1000 mWh g–1. However, insufficient capacity retention is also observed because of the instability of anionic redox. In contrast, better capacity retention and higher energy density (730 mWh g–1) are obtained for Li2MnO1.5F1.5 with a 4.4 V cutoff because of the enrichment of fluoride ions and activation of Mn2+/Mn4+ cationic redox. Moreover, electrode durability is significantly improved by using a highly concentrated electrolyte, and good capacity retention without voltage decay is achieved for >180 cycles.

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Does Li-ion transport occur rapidly in localized high-concentration electrolytes?

Abstract: The ionic conductivity and lithium-ion transference number of electrolytes significantly influence the rate capability of Li-ion batteries. Highly concentrated Li-salt/sulfolane (SL) electrolytes exhibit elevated Li+ transference numbers due to lithium-ion...

Cited by 28 publications

References 42 publications

Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

An Amphiphilic Molecule‐Regulated Core‐Shell‐Solvation Electrolyte for Li‐Metal Batteries at Ultra‐Low Temperature

Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li₂MnO_1.5F_1.5

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Does Li-ion transport occur rapidly in localized high-concentration electrolytes?

Abstract: The ionic conductivity and lithium-ion transference number of electrolytes significantly influence the rate capability of Li-ion batteries. Highly concentrated Li-salt/sulfolane (SL) electrolytes exhibit elevated Li+ transference numbers due to lithium-ion...

Cited by 28 publications

References 42 publications

Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

Li-Ion Transport and Solution Structure in Sulfolane-Based Localized High-Concentration Electrolytes

An Amphiphilic Molecule‐Regulated Core‐Shell‐Solvation Electrolyte for Li‐Metal Batteries at Ultra‐Low Temperature

Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li2MnO1.5F1.5

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Product

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About

Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li₂MnO_1.5F_1.5