Mixed oxides Ca2Fe2O5 and Ca2Co2O5 as anode materials for Li-ion batteries

Investigating the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste

Efficient and reliable energy storage systems are necessary to address the intermittency and variability of renewable energy sources. Thermochemical energy storage (TCES) has emerged as a promising solution for long-term renewable energy storage, with limestone being a widely studied material due to its abundance and high energy density. However, the practical implementation of limestone-based TCES systems faces challenges related to performance degradation upon multiple energy storage/release cycles, impacting their long-term viability and efficiency. In this study, we investigate the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste. Ca2Fe2O5 additives were synthesized by a wet precipitation method using three different Ca/Fe molar ratios and added to limestone waste in a 5, 10, and 20 weight concentration. The synthesized samples were characterized using XRD, SEM, EDS, BET, and XPS techniques. The thermal properties and heat storage performance of the samples were evaluated through thermogravimetric analysis of calcination/carbonation cycling experiments. The results demonstrate the potential of Ca2Fe2O5 additives to improve the cycling stability and energy storage density of limestone-based TCES systems. The sample with 5 wt% of Ca2Fe2O5 additive having Ca : Fe molar ratio of 1 : 1 outperformed all samples with an effective conversion rate of 0.21 after 40 cycles, 1.31 times higher than limestone waste.

Acmella oleracea induced nanostructured Ca2Fe2O5 for evaluation of photo catalytic degradation of cardiovascular drugs and bio toxicity

Biosynthesis of nanoparticles is increasingly becoming popular due to the demand for sustainable technologies worldwide. In the present investigation, Acmella oleracea plant extract fuelled combustion technique followed by calcination at 600 °C was adopted to prepare nanocrystalline Ca₂Fe₂O₅. The prepared nano compound was characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Ultra Violet (UV) spectroscopy, Infrared (IR) spectroscopy and its role was assessed for photocatalytic pollutant degradation along with bactericidal action in the concentration range of 1 μg/mL to 320 μg/mL. The photocatalytic degradation efficiency of pollutant drugs Clopidogrel Bisulphate and Asprin used for cardiovascular disorders is around 80% with 10 mg/L photocatalyst. The results showed that the photocatalytic activity increased with rising pH from 4, to 10, along with a significant antibacterial action against Enterococcus faecalis bacteria and a slight cytotoxic effect at high concentrations. The antibacterial property was reinforced by Minimum inhibitory concentrations (MIC) and Minimum bactericidal concentrations (MBC) studies with an average value of 0.103 at 600 nm which was further proved by significant anti-biofilm activeness. Adhesion tests in conjunction with cryogenic-scanning electron microscopy displayed a morphological change through agglomeration that caused an expansion in nano particles from 181 nm to 223.6 nm due to internalization followed by inactivation of bacteria. In addition, the non-toxicity of nano Ca₂Fe₂O₅ was confirmed by subtle cytological changes in microscopic images of Allium Cepa root cells in the concentration range 0.01-100 μg/mL and a slight inhibition in HeLa cell proliferation indicated by IC₅₀ value of 170.94 μg/mL. In total, the current investigation for the first time reveals the application of bio based synthesis of Nano Ca₂Fe₂O₅ to new possibilities in bioremediation namely degrading cardiovascular pharmaceutical pollutants, endodontic antibacterial action and cytological activity.

On Thermodynamic Aspects of Oxide Crystal Growth

Several metal oxide compounds, especially those containing metals possessing several valence states, are able to absorb or release oxygen under suitable thermodynamic conditions. Such behavior is found often in systems containing oxides of transition metals. It is important to note that the equilibrium oxidation level of those metal oxides can depend on the aggregation state, which may significantly impede crystal growth processes from the melt. If during the melt growth of such oxide crystals, the average valence state of the oxides is different in the molten and solid state, then crystallization is connected with the absorption of free oxygen from the ambient gas, or with the release of free oxygen into it. This phenomenon can be detected by simultaneous DTA/TG measurements and can deteriorate the stability of crystal growth. This holds especially if the average valence in the solid is smaller than in the melt, because oxygen release can lead to bubble formation at the crystallization front.

Co-activated Conversion Reaction of MoO2:CoMoO3 as a Negative Electrode Material for Lithium-Ion Batteries

Extensive studies to develop high-capacity electrodes have been conducted worldwide to meet the urgent demand for next-generation lithium-ion batteries. In this work, we demonstrated a novel strategy to alter the lithiation mechanism of the transition metal oxide to increase the reversible capacity of the electrode material. A representative insertion-type negative electrode material, MoO₂, was modified by introducing a heterogeneous element (Co) to synthesize the solid solution of CoO and MoO₂ (CoMoO₃). CoMoO₃ exhibited a notably improved reversible capacity of 860 mA h g^-1, attributed to the conversion reaction, in contrast to MoO₂ that delivers 310 mA h g^-1, as it is limited by the insertion reaction. X-ray absorption spectroscopy and X-ray diffraction demonstrated that CoO is converted to Co and Li₂O, amorphizing the host structure, whereas the conversion of MoO₂ takes place subsequently. Furthermore, the superior initial Coulombic efficiency of CoMoO₃ (84.4%) to that of typical conversion materials is attributed to the highly conductive Co and MoO₂, which reinforce the electronic conductivity of the active particles. The results obtained from this study provide significant insights to explore high capacity metal oxides for the advanced lithium-ion batteries.

Bricklike Ca9Co12O28 as an Active/Inactive Composite for Lithium-Ion Batteries with Enhanced Rate Performances

Transition-metal oxides are considered as promising anode materials because of the high theoretical specific capacities. However, the fast capacity fading and unstable cycling performance restricted their electrochemical performance. To achieve fast and stable lithium storage capability, in this work, bricklike Ca₉Co₁₂O₂₈ is synthesized via a modified Pechini method with the assistance of the C₁₂H₂₅SO₄Na surfactant. The as-obtained Ca₉Co₁₂O₂₈ ternary oxides exhibit stable structural stability, which may be attributed to the in situ formed CaO layers during the first discharge process. When tested as an anode material in lithium-ion batteries (LIBs), bricklike Ca₉Co₁₂O₂₈ exhibits an excellent reversible capacity of 517 mA h g^-1 at 1 C after 200 cycles. Even at the high rate of 3 C, the discharge capacity can still reach 392 mA h g^-1 after 200 cycles. It reveals a great application prospect in anode materials of LIBs.

Cheese-like bulk carbon with nanoholes prepared from egg white as an anode material for lithium and sodium ion batteries

Cheese-like bulk carbon fabricated from egg white exhibits an excellent electrochemical performance when evaluated as an anode for LIBs.

Fabrication of free-standing ZnMn2O4 mesoscale tubular arrays for lithium-ion anodes with highly reversible lithium storage properties

In this paper, ZnMn2O4 mesoscale tubular arrays on current collectors were successfully synthesized using a reactive template route combined with a postcalcination process through the shape-preserving conversion of ZnO nanorod arrays in aqueous solutions at room temperature. On the basis of the experimental analyses, including X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, a plausible formation mechanism of ZnMn2O4 tubular arrays was proposed in which solid ZnO nanorods are gradually transformed to ZnMn2O4 tubules via a simple cation exchange process between Zn(2+) and Mn(2+), followed by a postannealing process. Moreover, the lithium storage properties of the as-prepared ZnMn2O4 tubular structures were investigated by applying the structures as an active electrode material without auxiliary additives. The ZnMn2O4 array electrodes showed an excellent discharge capacity of ca. 1198.3 mAh g(-1) on the first cycle and exhibited outstanding cycling durability, rate capability, and Coulombic efficiency. These results indicate that the free-standing tubular array architectures of ZnMn2O4 prepared directly on the current collector can be powerful candidates for a highly reversible lithium storage electrode platform.