Nanoscale organization in piperidinium-based room temperature ionic liquids.

Here we report on the complex nature of the phase diagram of N-alkyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide ionic liquids using several complementary techniques and on their structural order in the molten state using small-wide angle x-ray scattering. The latter study indicates that the piperidinium aliphatic alkyl chains tend to aggregate, forming alkyl domains embedded into polar regions, similar to what we recently highlighted in the case of other ionic liquids.

Tin-Decorated Reduced Graphene Oxide and NaLi0.2Ni0.25Mn0.75O as Electrode Materials for Sodium-Ion Batteries.

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA·h·g-1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75O was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA·h·g-1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75O was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell's power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA·h·g-1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

Ionic Liquid-Based Electrolyte Membranes for Medium-High Temperature Lithium Polymer Batteries.

Li⁺-conducting polyethylene oxide-based membranes incorporating N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide are used as electrolyte separators for all-solid-state lithium polymer batteries operating at medium-high temperatures. The incorporation of the ionic liquid remarkably improves the thermal, ion-transport and interfacial properties of the polymer electrolyte, which, in combination with the wide electrochemical stability even at medium-high temperatures, allows high current rates without any appreciable lithium anode degradation. Battery tests carried out at 80 °C have shown excellent cycling performance and capacity retention, even at high rates, which are never tackled by ionic liquid-free polymer electrolytes. No dendrite growth onto the lithium metal anode was observed.