Bartosz Hamankiewicz

Electrochemical properties of lithium–titanium oxide, modified with Ag–Cu particles, as a negative electrode for lithium-ion batteries

Composites of Li4Ti5O12 with Ag–Cu particles were successfully synthesized by solid-state reaction followed by thermal decomposition of the metal substrates. The presence of metallic particles was confirmed by X-ray diffraction, scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Galvanostatic charge–discharge tests showed improved specific capacity and capacity retention of Li4Ti5O12/Ag–Cu composites at a 10C current rate, while cyclic voltammetry and electrochemical impedance spectroscopy revealed changes in Li+ ion chemical diffusion coefficient values and charge-transfer resistance with increasing amount of Ag–Cu in prepared powders. The synthesis and structural, morphological and electrochemical evaluation of Li4Ti5O12/Ag–Cu powders, carried out in this work, were also presented here for the first time.

The effect of compressive stresses on a silicon electrode’s cycle life in a Li-ion battery

Lithium-ion cells are currently very promising electrochemical power sources. New high-capacity electrodes made from silicon are currently under intensive study. As well as its high capacity, silicon undergoes a significant volume increase (up to 300%) during lithiation. This leads to the generation of internal stresses and fast cell degradation due to active material pulverization and separation from the current collector. Stress formation and its effect on silicon lithiation has been theoretically investigated by many researchers. It has been shown that internal compressive stress can slow down or stop silicon lithiation. In our study we applied external stress to an electrode active layer and measured the cell electrochemical parameters: capacity, cycle life, and charge transfer resistance. In contrast with theoretical estimations we observed an increase in capacity and cycle life when high compressive stress was applied. We believe this behavior is related to stress-induced lithiation front slowdown, which entails a longer stress relaxation period and as a consequence improves the cell parameters.

Comparative Physicochemical and Electrochemical Characterization of the Structure and Composition of Thin Pd Binary and Ternary Codeposits with Pt, Ru, and Rh

Pd-Ru, Pd-Rh, Pd-Pt-Ru, and Pd-Rh-Ru electrodes were prepared as thin layers by potentiostatic codeposition or chemical co-precipitation of metals from baths containing mixtures of chloride salts. The formation of substitutional solid solutions, with lattice parameters smaller than that of pure Pd, was confirmed by X-ray diffraction (XRD). The compositions at various levels of sample volume and thickness were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and also electrochemically by cyclic voltammetry (CV) in 0.5 M H2SO4. The differences between surface, subsurface, and bulk compositions were compared for various systems in a wide composition spectrum.