Damian Kowalski

Aqueous Zn-metal batteries are promising energy storage technologies due to their high performance, safety, cost-effectiveness, and sustainability. Herein, a Ni–Mn–Fe layered double hydroxide (LDH) is electrochemically synthesized and subjected to controlled electrochemical sulfidation to yield a highly porous, binder-free mixed metal oxide-sulfide (MOS) cathode with a tailored multiphase composition inherited from its LDH precursor. When paired with a chitosan-encapsulated Zn anode for enhanced interfacial stability, the quasi-solid-state Zn||MOS battery effectively reconciles high energy and high power performance by simultaneously delivering a capacity of 1417 123 mAh g-1 at 2 A g-1, an energy density of 2388 215 Wh kg-1 (cathode basis), a power density of 180 kW kg⁻1, and supercapacitor-like rate capability of 120 A g-1. The device also achieves a high voltage of up to 1.9 V, and retains 60% of its capacity after 2100 cycles at 30.0 A g-1 (compared to 810 cycles for bare Zn). DFT calculations elucidate synergistic contributions from metal oxides, sulfides, and residual LDH phases, highlighting their complementary roles in enhancing electronic conductivity, hydroxide adsorption, and ion diffusion. This work establishes a new benchmark for Zn-based cathodes and highlights the potential of multiphase electrode engineering for next-generation aqueous energy storag

In situ Raman spectroscopy fingerprints on the superoxide and lithium peroxide discharge products in nickel substituted manganite perovskite Li–O ₂ battery.

Anodizing is a high-voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, the Al₂O₃-like nanopores and TiO₂-like nanotubes could be successfully synthesized on many valve metals and alloys. Recently, it become possible to form nanotubular structures on iron and consequently control the ratio of hematite (Fe₂O₃) to magnetite (Fe₃O₄) by subsequent thermal treatment.¹ Electrochemically active nanotubes, such as self-organized TiO₂ are of high interest in the battery field due to a unique one-dimensional (1D) geometry offering high volume expansion tolerance and applications without binders and conductive additives. Herein, we report an in-situ Raman spectroscopy study under current control for a better fundamental understanding of Li⁺/Na⁺ storage in nanotubes and correlate the structural fingerprints with the electrochemical data on differential capacity plots of d(Q–Q ₀) dE ^–1.² Real-time measurements revealed that the nanotubes had undergone two major phase transformations with increasing lithium content, disclosing the sequential steps of a lithium intercalation type of storage. In contrast, sodium-ion insertion induced no significant crystal structure modification but instead a slight crystallinity rupture, signifying a dominant nondiffusion-limited capacitive type of storage. The insight into the charge storage in a 1D material in relation to other nanostructures such as nanoparticles³ will be discussed. References: L. Fadillah, D. Kowalski, M. Vincent, C. Zhu, S. Kitano, Y. Aoki and H. Habazaki, ACS Applied Materials & Interfaces , 2023, 15, 52563-52570. M. Vincent and D. Kowalski, ACS Applied Nano Materials , 2023, 6, 6528-6537. M. Vincent, S. Sajeev and D. Kowalski, Electrochimica Acta , 2023, 469, 143161. Figure 1. 3D in situ Raman spectroscopy patterns of Li-ion insertion to TiO₂ nanotubular electrodes. The spectra were obtained under a GCPL protocol. Raman spectra were collected using a Thermo Scientific DXR3 Raman microscope fitted with a 532 nm laser equipped with an in-situ ECC-OPTO El-Cell. Figure 1

Anodizing is a high-voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, the Al₂O₃-like nanopores and TiO₂-like nanotubes could be successfully synthesized on many valve metals and alloys. Recently, it become possible to form nanotubular structures on iron and consequently control the ratio of hematite (Fe₂O₃) to magnetite (Fe₃O₄) by subsequent thermal treatment.¹ Electrochemically active nanotubes, such as self-organized TiO₂ are of high interest in the battery field due to a unique one-dimensional (1D) geometry offering high volume expansion tolerance and applications without binders and conductive additives. Herein, we report an in - situ Raman spectroscopy study under current control for a better fundamental understanding of Li⁺/Na⁺ storage in nanotubes and correlate the structural fingerprints with the electrochemical data on differential capacity plots of d(Q–Q ₀) dE ^–1.² Real-time measurements revealed that the nanotubes had undergone two major phase transformations with increasing lithium content, disclosing the sequential steps of a lithium intercalation type of storage. In contrast, sodium-ion insertion induced no significant crystal structure modification but instead a slight crystallinity rupture, signifying a dominant nondiffusion-limited capacitive type of storage. The insight into the charge storage in a 1D material in relation to other nanostructures such as nanoparticles³ will be discussed. 1. L. Fadillah, D. Kowalski, M. Vincent, C. Zhu, S. Kitano, Y. Aoki and H. Habazaki, ACS Applied Materials & Interfaces , 2023, 15, 52563-52570. 2. M. Vincent and D. Kowalski, ACS Applied Nano Materials , 2023, 6, 6528-6537. 3. M. Vincent, S. S. Kumar and D. Kowalski, Electrochimica Acta , 2023, 469, 143161. Figure 1

For many years gold has been considered as catalytically inactive until Haruta and Hutchings demonstrated its catalytic behaviour in low-temperature CO oxidation.¹ The bulk gold is generally considered as a poor catalyst and becomes surprisingly active when its size is reduced to nanoscale dimension. The recently emerging field of plasmonics require precise control of gold structure at the nanometer and subnanometer scales particularly if combined with secondary materials such as titania. Herein, we aim to control the structure of Au on TiO₂ nanotubes by means of anodizing of TiAu alloys and two step process of anodizing of titanium and subsequent electrodeposition of gold in nanotubes.^2,3 Figure 1a shows comparison of Ti and TiAu alloy anodized in mono-ethylene-glycol electrolyte containing 0.1 mol.dm^-3 ammonium fluoride and 1 mol.dm^-3 of water.² The accumulation of gold at cell boundaries and resulting modification of TiO₂ nanotube outer-shell can be clearly recognized from backscattered SEM images. Figure 1b shows the nanostructure formed by gold electrodeposition in between TiO₂ nanotubes synthesised in di-ethylene-glycol electrolyte containing 2 wt.% HF and 2 wt.% of H₂O.³ The details of nanostructures growth and possible applications will be discussed. References: (1) Haruta, M., Nature, 437, 1098-1099 (2005). (2) Sepúlveda, M., Castaño, J.G., Echeverría, F., Aouki, Y. Kowalski, D., Habazaki, H., Electrochemistry Communications, 120, 106847 (2020). (3) Kowalska E., Juodkazis S., Henkiel P., Kowalski D., ACS Applied Nano Mat., 5 7696-(2022). Figure 1 a) SEM images of Ti and Ti-Au alloy anodized at 60V for 50 s in mono-ethylene-glycol electrolyte containing 0.1 mol.dm^-3 ammonium fluoride and 1 mol.dm^-3 of water; b) top image shows backscattering electron SEM image of Au electrodeposited in between nanotubes, the bottom image shows TEM of FIB lamella and corresponding EDS mapping (red: Ti, yellow: Au) for TiO₂/Au composite, c) FDTD modeling of the light absorption and scattering cross-sectional spectra for nanostructures. Figure 1

Electrochemically active iron oxide nanotubes formed by anodization are of high interest as battery components in various battery systems due to their 1D geometry, offering high volume expansion tolerance and applications without the use of binders and conductive additives. This work takes a step forward toward understanding lithium-ion storage in 1D nanotubes through the analysis of differential capacity plots d(Q - Q₀)·dE^-1 supported by in situ Raman spectroscopy observations. The iron oxide nanotubes were synthesized by anodizing polycrystalline iron and subsequently modified by thermal treatment in order to control the degree of crystallinity and the ratio of hematite (Fe₂O₃) to magnetite (Fe₃O₄). The electrochemical fingerprints revealed a quasi-reversible lithiation/delithiation process through Li₂O formation. Significant improvement in electrochemical performance was found to be related to the high degree of crystallinity and the increase of the hematite (Fe₂O₃) to magnetite (Fe₃O₄) ratio. In situ mechanistic studies revealed a reversible reduction of iron oxide to metallic iron simultaneously with Li₂O formation.