Enabling the Li-ion conductivity of Li-metal fluorosulphates by ionic liquid grafting

Abstract

Recently unveiled 'alkali metal fluorosulphate (AMSO 4 F)' class of compounds offers promising electrochemical and transport properties. Registering conductivity value as high as 10 −7 S cm −1 in NaMSO 4 F phases, we explored the fluorosulphate group to design novel compounds with high Li-ion conductivity suitable for solid electrolyte applications. In the process, we produced sillimanite-structured LiZnSO 4 F by low temperature synthesis (T ≤ 300°C). Examining this phase, we accidentally discovered the possibility of improving the ionic conductivity of poor conductors by forming a monolayer of ionic liquid at their particle surface. This phenomenon was studied by solid-state NMR, XPS and AC impedance spectroscopy techniques. Further, similar trends were noticed in other fluorosulphate materials like tavorite LiCoSO 4 F and triplite LiMnSO 4 F. With this study, we propose 'ionic liquid grafting' as an interfacial route to enable good Li-ion conductivity in otherwise poor conducting ceramics.

Influence of relative humidity on the structure and electrochemical performance of sustainable LiFeSO4F electrodes for Li-ion batteries

“…Smaller particles lead to a shortened diffusion path for Li + and to better electrode kinetics in agreement with our experimental results. Another possibility to account for such a difference could be the presence of an EMI-TFSI grafting layer at the surface of LiFeSO 4 F which will enhance the ionic conductivity, as previously reported for LiZnSO 4 F. 12 This would contrast with an ionic blocking thin layer of TTEG at the surface of LiFeSO 4 F made in glycol-based media, although such a possibility is therefore quite unlikely given that repeatedly washing the sample yielded no changes in performance.…”

Energy Storage Materials Synthesized from Ionic Liquids

“…For a while, Barpanda and coworkers sustained their effort towards understanding the underlying mechanism of such increment in ionic conductivity for the IL-assisted synthesized LiZnSO 4 F. The presence of a thin layer of IL attached to the LiZnSO 4 F surface resulted in the formation of a slightly Li-rich ceramic IL composite claimed to contribute to the improvement in conductivity. [60] With the intention of attesting the flexibility of the ILgrafting-induced conductivity enhancement and its crystalstructure-independent nature, this phenomenon was extended to other non-isostructural Li-metal fluorosulfate family members such as LiMSO 4 F (M = Co, Mn). Thus, the IL grafting can be utilized as an alternative process for the synthesis of ceramic-IL composites endowed with much higher ionic conductivity, very close to the benchmarking range needed for solid electrolyte applications.…”

Sulfate Chemistry for High‐Voltage Insertion Materials: Synthetic, Structural and Electrochemical Insights

“…When the LiMSO 4 F materials are prepared using ionic‐liquid media, a thin layer of ionic liquid is permanently attached to the grain boundaries (Figure 4d). An XPS and solid‐state NMR spectroscopy study proves the presence of the 8–15 nm thick ionic‐liquid graft (IG) 23b. This offers excellent Li + permeability to form a percolating network for Li + migration, although the bulk of the material is not so conducting.…”