Search Results (7)

LiNi_0.9Mn_0.1−xAl_xO₂ (NMA) (x = 0.01, 0.03, 0.05) cathodes were synthesized via the co-precipitation method and continued with the calcination process in a tube furnace at 750 °C under flowing oxygen gas for 12 h. X-ray diffraction (XRD) revealed a well-formed and high-purity phase with a hexagonal structure. LiNi_0.9Mn_0.07Al_0.03O₂ (NMA 973) had the best electrochemical performance with the lowest redox peak separation, the smallest charge transfer resistance (71.58 Ω cm⁻²), the highest initial specific discharge capacity of 172 mAh g⁻¹ at 0.1C, and a capacity retention of 98% after 100 cycles. Under high current density at 1 C, NMA 973 had excellent specific discharge capacity compared to the other samples. The optimal content of Mn and Al elements is a crucial factor to obtain the best electrochemical performance of NMA. Therefore, NMA 973 is a promising candidate as a cathode for high-energy-density lithium-ion batteries. Full article

The increased voltage loading of transformers has led to research on improving transformers’ lifespans to meet demand. Insulation oil acts as cooling medium that can significantly affect the performance of a transformer. This paper discusses an experimental study on the influences of the doping of carbon nanotube (CNT) particles and magnetic fields on the electrical properties of mineral oil (MO). An analysis of electrical properties was conducted using AC breakdown tests, Tan Delta tests, Raman measurements, and simultaneous thermal analysis. Proper preparation was considered before starting the analysis of the electrical properties. The AC breakdown voltages before and after modification were measured. The experiment results indicated that the AC breakdown of mineral oil with a suitable amount of carbon nanotube particles (0.005 g/L) and a suitable magnetic field (0.45 T) gives the highest breakdown voltage. It was found that the proper treatment of nanofluid also greatly influences breakdown voltage. Additionally, Raman measurements analyzed the physical changes in the samples. From the results obtained, the addition of carbon nanotubes and the magnetic field of mineral oil leads to an improved performance of the transformer. Full article

Currently, efforts to address the energy needs of large-scale power applications have expedited the development of sodium–ion (Na–ion) batteries. Transition-metal oxides, including Mn₂O₃, are promising for low-cost, eco-friendly energy storage/conversion. Due to its high theoretical capacity, Mn₂O₃ is worth exploring as an anode material for Na-ion batteries; however, its actual application is constrained by low electrical conductivity and capacity fading. Herein, we attempt to overcome the problems related to Mn₂O₃ with heteroatom-doped reduced graphene oxide (rGO) aerogels synthesised via the hydrothermal method with a subsequent freeze-drying process. The cubic Mn₂O₃ particles with an average size of 0.5–1.5 µm are distributed to both sides of heteroatom-doped rGO aerogels layers. Results indicate that heteroatom-doped rGO aerogels may serve as an efficient ion transport channel for electrolyte ion transport in Mn₂O₃. After 100 cycles, the electrodes retained their capacities of 242, 325, and 277 mAh g⁻¹, for Mn₂O₃/rGO, Mn₂O₃/nitrogen-rGO, and Mn₂O₃/nitrogen, sulphur-rGO aerogels, respectively. Doping Mn₂O₃ with heteroatom-doped rGO aerogels increased its electrical conductivity and buffered volume change during charge/discharge, resulting in high capacity and stable cycling performance. The synergistic effects of heteroatom doping and the three-dimensional porous structure network of rGO aerogels are responsible for their excellent electrochemical performances. Full article

Li₄Ti₅O₁₂ (LTO) is an alternative anode material to substitute commercial graphite for lithium-ion batteries due to its superior long cycle life, small volume change (zero strain), good thermal stability, and relatively high power. In this work, iodide-doped LTO is prepared by solid-state reaction method via ball milling method and subsequently calcined at 750 °C for 10 h in air atmosphere. X-ray diffraction (XRD) of iodide-doped LTO reveals the spinel cubic structure without any impurities detected. The 0.2 mol lithium iodide-doped LTO shows enhanced high-rate capability with a specific discharge capacity of 123.31 mAh g⁻¹ at 15 C. The long cyclic performance of 0.2 mol lithium iodide-doped LTO delivers a specific discharge capacity of 171.19 mAh g⁻¹ at 1 C with a capacity retention of 99.15% after 100 cycles. It shows that the iodide-doped LTO is a promising strategy for preparing a high electrochemical performance of LTO for the anode of lithium-ion batteries. Full article

Owing to their high theoretical capacity, transition-metal oxides have received a considerable amount of attention as potential anode materials in sodium-ion (Na-ion) batteries. Among them, Mn₃O₄ has gained interest due to the low cost of raw materials and the environmental compatibility. However, during the insertion/de-insertion process, Mn₃O₄ suffers from particle aggregation, poor conductivity, and low-rate capability, which, in turn, limits its practical application. To overcome these obstacles, we have successfully prepared Mn₃O₄ nanoparticles distributed on the nitrogen (N)-doped and nitrogen, sulphur (N,S)-doped reduced graphene oxide (rGO) aerogels, respectively. The highly crystalline Mn₃O₄ nanoparticles, with an average size of 15–20 nm, are homogeneously dispersed on both sides of the N-rGO and N,S-rGO aerogels. The results indicate that the N-rGO and N,S-rGO aerogels could provide an efficient ion transport channel for electrolyte ion stability in the Mn₃O₄ electrode. The Mn₃O₄/N- and Mn₃O₄/N,S-doped rGO aerogels exhibit outstanding electrochemical performances, with a reversible specific capacity of 374 and 281 mAh g⁻¹, respectively, after 100 cycles, with Coulombic efficiency of almost 99%. The interconnected structure of heteroatom-doped rGO with Mn₃O₄ nanoparticles is believed to facilitate fast ion diffusion and electron transfer by lowering the energy barrier, which favours the complete utilisation of the active material and improvement of the structure’s stability. Full article

The exponential growth in the production of electric vehicles requires an increasing supply of low-cost, high-performance lithium-ion batteries. The increased production of lithium-ion batteries raises concerns over the availability of raw materials, especially cobalt for batteries with nickel-rich cathodes, in which these constraints can impact the high price of cobalt. The reliance on cobalt in these cathodes is worrisome because it is a high-cost, rare material, with an unstable supply chain. This review describes the need and feasibility of developing cobalt-free high-nickel cathode materials for lithium-ion batteries. The new type of cathode material, LiNi_1−x−yMn_xAl_yO₂ promises a completely cobalt-free composition with almost the same electrochemical performance as that of the conventional high-nickel cathode. Therefore, this new type of cathode needs further research for its commercial applications. Full article

MnCoGe-based compounds have been increasingly studied due to their possible large magnetocaloric effect correlated to the magnetostructural coupling. In this research, a comprehensive study of structure, magnetic phase transition, magnetocaloric effect and thermomechanical properties for MnCoGe_1−xSi_x is reported. Room temperature X-ray diffraction indicates that the MnCoGe_1−xSi_x (x = 0, 0.05, 0.1, 0.15 and 0.2) alloys have a major phase consisting of an orthorhombic TiNiSi-type structure with increasing lattice parameter b and decreasing others (a and c) with increasing Si concentration. Along with M-T and DSC measurements, it is indicated that the T_c value increased with higher Si concentration and decreased for structural transition temperature T_str. The temperature dependence of the magnetization curves overlaps completely, indicating that there is no thermal hysteresis, and it is shown that the transition is the second-order type. It is also shown that the decreased magnetization on the replacement of Si for Ge decreases the value of −ΔS_M from −ΔS_M~8.36 J kg⁻¹ K⁻¹ at x = 0 to −ΔS_M~5.49 J kg⁻¹ K⁻¹ at x = 0.2 with 5 T applied field. The performed Landau theory has confirmed the second-order transition in this study, which is consistent with the Banerjee criterion. The magnetic measurement and thermomechanical properties revealed the structural transition that takes place with Si substitution of Ge. Full article