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Ionic liquids (ILs) containing zwitterions have been studied as electrolytes for lithium-ion batteries (LIBs). The effects of addition of a pyrrolidinium zwitterion in an IL electrolyte on the thermal and electrochemical stability and charge/discharge properties of Li/LiCoO 2 and graphite/Li cells were investigated. The thermal decomposition temperature of the IL electrolyte composed of N -methyl- N -propylpyrrolidinium bis(fluorosulfonyl)amide ([P13][FSA])/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) with 3-(1-butylpyrrolidinium)propane-1-sulfonate (Bpyps) as the zwitterionic additive, the thermal decomposition temperature was about 300 °C. The electrochemical window of [P13][FSA]/LiTFSA/Bpyps was 0–+5.4 V vs. Li/Li + , which was almost identical to that of [P13][FSA]/LiTFSA. Li|electrolyte|LiCoO 2 cells containing the IL/Bpyps electrolyte system exhibited high capacities in the cut-off voltage range of 3.0–4.6 V, even after 50 cycles. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions were observed in the range of 0 and + 0.4 V vs. Li/Li + . Further, graphite|electrolyte|Li cells containing [P13][FSA]/LiTFSA/Bpyps exhibited stable charge/discharge cycle behaviour over 50 cycles. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) containing zwitterions were studied as electrolytes for lithium-ion batteries. The effect of a pyrrolidinium zwitterion with a long ether side chain on the thermal and electrochemical properties of an IL and the charge/discharge properties of Li/LiCoO 2 , Li/LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC), and graphite/Li cells with IL/zwitterion electrolytes was investigated. The melting temperature of the IL-based electrolyte composed of N -methyl- N -methoxymethylpyrrolidinium bis(fluorosulfonyl)amide ([Pyr 1,1O1 ][FSA]) and lithium bis(fluorosulfonyl)amide (LiFSA) with 3-(1-(2-(2-methoxyethoxy)ethyl)pyrrolidin-1-ium-1-yl)propane-1-sulfonate (OE2pyps) as the zwitterionic additive was about −18 °C. The electrochemical window of [Pyr 1,1O1 ][FSA]/LiFSA/OE2pyps was over 5 V vs. Li/Li + . Li|electrolyte|LiCoO 2 cells containing the [Pyr 1,1O1 ][FSA]/LiFSA/OE2pyps electrolyte system exhibited high capacity values in the cut-off voltage range of 3.0–4.3 V, even after 50 cycles. Moreover, increases of interfacial resistance between the electrolyte and cathode during cycling were suppressed. Li|electrolyte|NMC cells containing this electrolyte system also exhibited high capacities in a wide cut-off voltage range of 3.0–4.6 V, even after 50 cycles. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions was observed between 0 and + 0.4 V vs. Li/Li + . Further, graphite|electrolyte|Li cells containing [Pyr 1,1O1 ][FSA]/LiFSA/OE2pyps exhibited stable charge/discharge cycle behavior over 5 cycles. [ABSTRACT FROM AUTHOR]

Zwitterions with a cyano group on the side chain (CZ) were synthesized. Although the addition of CZ caused a slightly negative effect on viscosity, ionic conductivity, limiting current density, and lithium transference number, the oxidation limit of PEGDME/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) composites was improved to over 5 V. For charge/discharge testing using Li|electrolyte|LiCoO 2 cells, the cycle stability of PEGDME/LiTFSA with CZ in the voltage range of 3.0–4.6 V was much higher than that of PEGDME/LiTFSA. Incorporating a small mole fraction of CZ into PEGDME-based electrolytes prevented an increase in the interface resistance between the electrolyte and cathode with increasing numbers of the cycle. [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes show great potential in electrochemical devices. Poly(ethylene oxide) (PEO) has been studied as a matrix for solid polymer electrolytes because it has relatively high ionic conductivity. In order to investigate the effect of zwitterions on the electrochemical properties of poly(ethylene glycol) dimethyl ether (G5)/lithium bis(fluorosulfonyl) amide (LiFSA) electrolytes, a liquid zwitterion (ImZ2) was added to the G5-based electrolytes. In this study, G5, which is a small oligomer, was used as a model compound for PEO matrices. The thermal properties, ionic conductivity, and electrochemical stability of the electrolytes with ImZ2 were evaluated. The thermal stabilities of all the G5-based electrolytes with ImZ2 were above 150 °C, and the ionic conductivity values were in the range of 0.8–3.0 mS cm −1 at room temperature. When the electrolytes contained less than 5.5 wt% ImZ2, the ionic conductivity values were almost the same as that of the electrolyte without ImZ2. The electrochemical properties were improved with the incorporation of ImZ2. The anodic limit of the electrolyte with 5.5 wt% ImZ2 was 5.3 V vs. Li/Li + , which was over 1 V higher than that of G5/LiFSA. [ABSTRACT FROM AUTHOR]