Giridhar Pulletikurthi

A Prussian Blue/Zinc Secondary Battery with a Bio-Ionic Liquid–Water Mixture as Electrolyte

The development of rechargeable zinc ion batteries with high capacity and high cycling stability is a great challenge in aqueous solution due to hydrogen evolution and dendritic growth of zinc. In this study, we present a zinc ion secondary battery, comprising a metallic zinc anode, a bio-ionic liquid-water electrolyte, and a nanostructured prussian blue analogue (PBA) cathode. Both the Zn anode and the PBA cathode exhibit good compatibility with the bio-ionic liquid-water electrolyte, which enables the electrochemical deposition/dissolution of zinc at the zinc anode, and reversible insertion/extraction of Zn(2+) ions at the PBA cathode. The cell exhibits a well-defined discharge voltage plateau of ∼1.1 V with a specific capacity of about 120 mAh g(-1) at a current of 10 mA g(-1) (∼0.1 C). The Zn anode shows great reversibility, and dendrite-free Zn deposits were obtained after 100 deposition/dissolution cycles. The integration of an environmentally friendly PBA cathode, a nontoxic and low-cost Zn anode, and a biodegradable ionic liquid-water electrolyte provides new perspective to develop rechargeable zinc ion batteries for various applications in electric energy storage.

Dendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteries.

Metallic zinc is a promising anode material for rechargeable Zn-based batteries. However, the dendritic growth of zinc has prevented practical applications. Herein it is demonstrated that dendrite-free zinc deposits with a nanocrystalline structure can be obtained by using nickel triflate as an additive in a zinc triflate containing ionic liquid. The formation of a thin layer of Zn-Ni alloy (η- and γ-phases) on the surface and in the initial stages of deposition along with the formation of an interfacial layer on the electrode strongly affect the nucleation and growth of zinc. A well-defined and uniform nanocrystalline zinc deposit with particle sizes of about 25 nm was obtained in the presence of Ni(II) . Further, it is shown that the nanocrystalline Zn exhibits a high cycling stability even after 50 deposition/stripping cycles. This strategy of introducing an inorganic metal salt in ionic liquid electrolytes can be considered as an efficient way to obtain dendrite-free zinc.

Electrodeposition and stripping behavior of a zinc/polystyrene composite electrode in an ionic liquid

The cycling behavior of a zinc/polystyrene composite electrode in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py1,4]TfO) was studied at room temperature. A brass substrate covered by polystyrene spheres was used to produce a zinc composite electrode. The obtained electrode was investigated using various techniques like potentiostatic and galvanostatic deposition/stripping cycles, scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX). The effect of a uniaxial mechanical pressure on adhesion and cycling behavior was also investigated. The results show that zinc grows uniformly within the voids of the polystyrene structures with no hints of dendritic growth. Such a composite material is interesting as electrode material for zinc-based batteries.

Electrodeposition of Ge, Sn and GexSn1-x from two different room temperature ionic liquids

In this paper, we present a simple and viable route for the synthesis of germanium-tin alloys (GexSn1-x) from two different ionic liquids, namely, 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py1,4]TfO) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]Tf2N). Cyclic voltammetric analysis showed that in the presence of both SnCl2 and GeCl4 precursors, a shoulder peak is obtained which is related to the formation of GexSn1-x. Constant potential deposition was performed to obtain GexSn1-x thin films. Furthermore, on changing the concentration of GeCl4 and SnCl2 in [Py1,4]TfO, the GexSn1-x composition could be varied.

Modification of the Electrolyte/Electrode Interface for the Template-free Electrochemical Synthesis of Metal Nanowires from Ionic Liquids

In electrochemistry, the electrode/electrolyte interface (EEI) governs the charge/mass-transfer processes and controls the nucleation/growth phenomena. The EEI in ionic liquids (ILs) can be controlled by changing the cation/anion of the IL, salt concentration, electrode potential, and temperature. Here, we show that adding a dopant salt leads to the deposition of nanowires. To illustrate, zinc nanowires were electrodeposited from ZnCl2/1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate in the presence of GaCl3 as a dopant salt. The choice of Zn salt and its ratio to GaCl3 were found to be crucial for Zn nanowires formation. AFM studies revealed that the solvation structure of Au(111)/IL changes significantly in the presence of GaCl3 and ZnCl2. Chronoamperometry showed changes in the nucleation/growth process, consequently leading to the formation of nanowires. A similar approach was adopted to synthesize Sn nanowires. Thus, modification of the EEI by adding a dopant to ILs can be a viable method to obtain nanowires.

Electrochemically induced phase separation and in situ formation of mesoporous structures in ionic liquid mixtures

Tailoring mesoporous structures via electrochemically induced phase separation at solid/ionic-liquid interface is shown. Liquid-liquid phase separation is mainly dependent on temperature and composition. Electric fields have also been shown to influence demixing of binary liquid mixtures. However, a puzzling behavior that remains elusive is the electric field–induced phase separation in ion-containing solvents at low voltages, as predicted by Tsori and Leibler. Here, we report the first experimental study of such a phenomenon in ionic liquid–silane mixtures, which not only results in phase separation at the electrode-electrolyte interface (EEI) but also is accompanied by deposition of porous structures of micrometer size on the electrode. This multiscale phenomenon at the EEI was found to be triggered by an electrochemically induced process. Using several analytical methods, we reveal the involved mechanism in which the formation of new Si–N bonds becomes unstable and eventually decomposes into the formation of silane-rich and silane-poor phases. The deposition of porous structures on the electrode surface is therefore a realization of the silane-rich phase. The finding of an electrochemically induced phase separation not only brings a paradigm shift in understanding the EEI in ionic liquids but also provides alternative strategies toward designing porous surfaces.

How a Transition Metal(II) Chloride Interacts with a Eutectic AlCl₃‐based Ionic Liquid: Insights into the speciation of the Electrolyte and electrodeposition of Magnetic Materials

Electrostatic interactions are characteristic of ionic liquids (ILs) and play a pivotal role in determining the formation of species when solutes are dissolved in them. The formation of new species/complexes has been investigated for certain ILs. However, such investigations have not yet focused on eutectic liquids, which are a promising class of ILs. These liquids (or liquid coordination complexes, LCCs) are rather new and are composed of cationic and anionic chloro complexes of metals. To date, these liquids have been employed as electrolytes to deposit metals and as solvents for catalysis. The present study deals with a liquid that is prepared by mixing a 1.2:1 mol ratio of AlCl3 and 1-butylpyrrolidine. An attempt has been made to understand the interactions of FeCl2 with the organic molecule using spectroscopy. It was found that dissolved Fe(II) species interact mainly with the IL anion and such interactions can lead to changes in the cation of the electrolyte. Furthermore, the viability of depositing thick magnetic films of Fe and Fe-Al has been explored.