Mariusz Walkowiak

Increase in efficiency of dye-sensitized solar cells by porous TiO2 layer modification with gadolinium-containing thin layer

Modified with gadolinium-containing layer, nanoporous titania electrode and its application in dye-sensitized solar cells were reported. The electrode prepared was characterized with UV-Vis and X-ray diffraction (XRD) techniques. The amount of gadolinium was measured with inductively coupled plasma-optical emission spectrometry (ICP-OES) experiments. The modified electrode showed reduced N3 dye adsorption ability, but increased light conversion efficiency in comparison with the non-modified electrode. The overall conversion efficiencies, determined under 400 W/m2 irradiation with tungsten-halogen lamp at room temperature, were 0.55% for non-modified and 0.74% for modified electrodes.

Synthesis and characterization of a new hybrid TiO2/SiO2 filler for lithium conducting gel electrolytes

This paper describes the synthesis and properties of a new type of ceramic fillers for composite polymer gel electrolytes. Hybrid TiO2-SiO2 ceramic powders have been obtained by co-precipitation from titanium(IV) sulfate solution using sodium silicate as the precipitating agent. The resulting submicron-size powders have been applied as fillers for composite polymer gel electrolytes for Li-ion batteries based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF/HFP) copolymeric membranes. The powders, dry membranes and gel electrolytes have been examined structurally and electrochemically, showing favorable properties in terms of electrolyte uptake and electrochemical characteristics in Li-ion cells.

Impact of selected supramolecular additives on the initial electrochemical lithium intercalation into graphite in propylene carbonate

Impact of silicon tripodand-type electrolyte additives and graphite pre-treatment agents on the electrochemical intercalation of lithium cations into graphite was investigated. Addition of Si-tripodand-type silanes to propylene carbonate-based electrolytes was found to suppress detrimental solvent co-intercalation and graphite exfoliation. Similar effects were observed for graphite pre-treated with the reported silane agents. It was observed that the presented supramolecular additives allow for the formation of effective passive layers on graphite during first charging, and thus can be considered as novel low-cost film-forming components for rechargeable lithium batteries.

Charge–discharge studies of all-solid-state Li/LiFePO4 cells with PEO-based composite electrolytes encompassing metal organic frameworks

Lithium batteries with high energy density can be achieved only with a metallic-lithium anode in conjunction with solid polymer electrolyte. Unfortunately, the undesirable interfacial properties and the subsequent formation of a solid electrolyte interface (SEI) layer and poor ionic conductivity at ambient temperature hamper this system from being commercialized. In order to conquer these issues, numerous attempts have been made. Herein we report the preparation and electrochemical properties of a nickel-1,3,5-benzene tricarboxylate metal organic framework (Ni3–(BTC)2–MOF) laden-composite polymer electrolyte with a lithium salt (LiTFSI). The added Ni3–(BTC)2–MOF plays a vital role in enhancing the ionic conductivity, and the mechanical and thermal properties. The scavenging properties of the highly porous MOF significantly improved the Li/electrolyte interfacial properties. A 2032-type coin cell composed of Li/CPE/LiFePO4 was assembled and its cycling profile is discussed.

Graphene oxide-multiwalled carbon nanotubes composite as an anode for lithium ion batteries

Abstract Nowadays reduced graphene oxide (rGO) is regarded as a highly interesting material which is appropriate for possible applications in electrochemistry, especially in lithium-ion batteries (LIBs). Several methods were proposed for the preparation of rGO-based electrodes, resulting in high-capacity LIBs anodes. However, the mechanism of lithium storage in rGO and related materials is still not well understood. In this work we focused on the proposed mechanism of favorable bonding sites induced by additional functionalities attached to the graphene planes. This mechanism might increase the capacity of electrodes. In order to verify this hypothesis the composite of non-reduced graphene oxide (GO) with multiwalled carbon nanotubes electrodes was fabricated. Electrochemical properties of GO composite anodes were studied in comparison with similarly prepared electrodes based on rGO. This allowed us to estimate the impact of functional groups on the reversible capacity changes. As a result, it was shown that oxygen containing functional groups of GO do not create, in noticeable way, additional active sites for the electrochemical reactions of lithium storage, contrary to what has been postulated previously.

Titanium dioxide high aspect ratio nanoparticle hydrothermal synthesis optimization

Abstract TiO2-B (bronze) nanowires were synthesized via simple hydrothermal treatment of commercial titanium dioxide nanopowder in aqueous NaOH. The reaction temperature, calcination temperature, reaction time, NaOH concentration, autoclave filing fraction and precursor were systematically varied to optimize the nanowire morphology. The crystal structure, morphology and particle size were investigated by XRD, SEM and TEM. The morphology and structure are sensitive to experimental conditions. A reaction temperature of at least 150°C and NaOH concentration at least 10 M are essential, but reaction time from 24 to 72 h makes little difference. Nanowires obtained at 150°C were 60-180 nm wide and 2-4 μm long, while those after treatment at 200°C were thinner (40-100 nm) and longer (2-6 μm). The relationship between reaction conditions and morphology is discussed and practical guidelines for titanium dioxide nanowire synthesis are suggested Graphical Abstract