Natalia Borisenko

The interface ionic liquid(s)/electrode(s): in situ STM and AFM measurements.

The structure of the interfacial layer(s) between the extremely pure air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate and Au(111) has been investigated using in situ scanning tunneling microscopy (STM) at electrode potentials more positive than the open circuit potential. The in situ STM measurements show that layers/islands form with increasing electrode potential. According to recently published atomic force microscopy (AFM) data the anion is adsorbed even at low anodic overvoltages and adsorption becomes slightly stronger with increasing electrode potential. Furthermore, the number of interfacial layers increases with increasing electrode potential. The present discussion paper shows that these layers are not uniform and have a structure on the nanoscale, supporting earlier results that the interface electrode/ionic liquid is highly complex. It is also shown that the addition of solutes changes this structure considerably. AFM results reveal that in the pure liquid, interfacial layers lead to a repulsive force but the addition of 10 wt% of LiCl leads to an attractive force close to the surface. These preliminary results show that solutes strongly alter the interfacial structure of the ionic liquid/ electrode interface.

An in situ STM and DTS study of the extremely pure [EMIM]FAP/Au(111) interface.

Herein the structure of the interfacial layer between the air- and water-stable ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM]FAP) and Au(111) is investigated using in situ scanning tunneling microscopy (STM), distance tunneling spectroscopy (DTS) and cyclic voltammetry (CV) measurements. The in situ STM measurements reveal that structured interfacial layers can be probed in both cathodic and anodic regimes at the IL/Au(111) interface. The structure of these layers is dependent on the applied electrode potential, the number of subsequent STM scans and the scan rate. Furthermore, first DTS results show that the tunneling barrier during the 1st STM scan does not seem to change significantly in the cathodic potential regime between the ocp (-0.2 V) and -2.0 V.

Investigation of Various Ionic Liquids and Catalyst Materials for Lithium-Oxygen Batteries

Abstract We report about the use of different ionic liquids and catalyst materials in lithium-oxygen batteries. Different types of oxygen electrodes such as self-supporting oxygen electrodes and catalyst-coated separators were prepared by hot-pressing and spray-coating procedures, respectively. Porous carbon material such as Ketjen Black, binder material and different metal oxides were used to prepare the cathodes. Self-supporting oxygen electrodes and catalyst-coated separators consist of a carbon material loading of 10 and 1.5 mg/cm2, respectively. Electrolyte systems based on lithium bis-(trifluoromethylsulfonyl) imide (LiTFSI) in ionic liquids and lithium hexafluorophosphate (LiPF6) in carbonate solvents were investigated in lithium-oxygen batteries. 1-butyl-1-methyl-pyrrolidinium bis-(trifluoromethylsulfonyl) imide and 1-butyl-1-methyl-pyrrolidinium tetracyanoborate as well as 1-ethyl-3-methyl-imidazolium bis-(trifluoromethylsulfonyl) imide, thi oisocyanat and dicyanamide were tested. The cell potential recorded for ionic liquids ranged from 2 to 2.5 V during the discharge process. At a current density of 0.1 mA/cm2geom discharge capacities were found to be higher for lithium-oxygen cells using imidazolium-based ionic liquids compared to pyrrolidinium-based ionic liquids. Discharge voltages between 2.7 and 2.8 V were observed for the carbonate-based solvents. The discharge potentials observed were independent of the metal oxide used, but the charge potentials were highly dependent on the catalyst materials employed. Good reversibility was obtained when the corresponding lithium-oxygen cells were cycled at 20–40% of their maximum capacity (mA h/g C).

Electrodeposition of Lithium/Polystyrene Composite Electrodes from an Ionic Liquid: First Attempts

Abstract One challenge in the use of metallic lithium in secondary lithium ion or lithium air batteries is the dendritic growth of lithium upon repeated cycling which might either lead to a short circuit or at least to an uneven current distribution and bad cycling stability. In the present paper we present our first results on the electrodeposition of lithium from an ionic liquid within the voids of a polystyrene opal structure on copper. For this purpose polystyrene spheres with an average diameter of about 600 nm were applied onto a copper sheet by a simple dipping process resulting in a layer thickness of about 10 μm. Lithium can be deposited within this polymer structure without damaging it and the subsequent dissolution of the polystyrene spheres delivers a macroporous lithium film, proving that a mechanically stable composite electrode is feasible.

Electroless Deposition of III–V Semiconductor Nanostructures from Ionic Liquids at Room Temperature

Group III-V semiconductor nanostructures are important materials in optoelectronic devices and are being researched in energy-related fields. A simple approach for the synthesis of these semiconductors with well-defined nanostructures is desired. Electroless deposition (galvanic displacement) is a fast and versatile technique for deposition of one material on another and depends on the redox potentials of the two materials. Herein we show that GaSb can be directly synthesized at room temperature by galvanic displacement of SbCl3 /ionic liquid on electrodeposited Ga, on Ga nanowires, and also on commercial Ga. In situ AFM revealed the galvanic displacement process of Sb on Ga and showed that the displacement process continues even after the formation of GaSb. The bandgap of the deposited GaSb was 0.9±0.1 eV compared to its usual bandgap of 0.7 eV. By changing the cation in the ionic liquid, the redox process could be varied leading to GaSb with different optical properties.

Hydrofluoric Acid-Free Electroless Deposition of Metals on Silicon in Ionic Liquids and Its Enhanced Performance in Lithium Storage

Metal nanoparticles such as Au, Ag, Pt, and so forth have been deposited on silicon by electroless deposition in the presence of hydrofluoric acid (HF) for applications such as oxygen reduction reaction, surface-enhanced Raman spectroscopy, as well as for lithium ion batteries. Here, we show an HF-free process wherein metals such as Sb and Ag could be deposited onto electrodeposited silicon in ionic liquids. We further show that, compared to electrodeposited silicon, Sb-modified Si demonstrates a better performance for lithium storage. The present study opens a new paradigm for the electroless deposition technique in ionic liquids for developing and modifying functional materials.

Electrodeposition of Semiconductors in Ionic Liquids

Ionic liquids are superior media for production of semiconductors by a relatively simple electrochemical process. Nowadays ionic liquids are developing rapidly and their scientific and technological importance compasses a wide range of applications that attract the interest of the scientists. In this chapter the literature data on the feasibility of ionic liquids for electrochemical synthesis of semiconductors will be discussed.

Electrochemical Synthesis of Battery Electrode Materials from Ionic Liquids

Electrode materials as well as the electrolytes play a decisive role in batteries determining their performance, safety, and lifetime. In the last two decades, different types of batteries have evolved. A lot of work has been done on lithium ion batteries due to their technical importance in consumer electronics, however, the development of post-lithium systems has become a focus in recent years. This chapter gives an overview of various battery materials, primarily focusing on development of electrode materials in ionic liquids via electrochemical route and using ionic liquids as battery electrolyte components.

Ionic liquids at interfaces: general discussion

Andrew Abbott, Matthew Addicoat, Leigh Aldous, Radha Gobinda Bhuin, Natalia Borisenko, José Nuno Canongia Lopes, Ryan Clark, Samuel Coles, Margarida Costa Gomes, Benjamin Cross, Jeffrey Everts, Millicent Firestone, Ramesh Gardas, Matthieu Gras, Simon Halstead, Christopher Hardacre, John Holbrey, Toshiyuki Itoh, Vladislav Ivaništšev, Johan Jacquemin, Philip Jessop, Robert Jones, Barbara Kirchner, Sichao Li, Ruth Lynden-Bell, Doug MacFarlane, Florian Maier, Markus Mezger, Aǵılio Pádua, Octavian D. Pavel, Susan Perkin, Simon Purcell, Mark Rutland, John M. Slattery, Sefik Suzer, Kazuhisa Tamura, Morgan L. Thomas, Shraeddha Tiwari, Seiji Tsuzuki, Betul Uralcan, William Wallace, Masayoshi Watanabe and James Wishart