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Item Dual storage mechanism of Bi2O3/Co3O4/MWCNT composite as an anode for lithium-ion battery and lithium-ion capacitor(Elsevier B.V., 2024) Lakshmi Sagar, G.; Brijesh, K.; Mukesh, P.; Hegde, A.P.; Kumar, A.; Kumar, A.; Bhat, K.S.; Nagaraja, H.S.Bismuth oxide(Bi2O3) and cobalt oxide(Co3O4) are promising owing to their unique properties, high storage capacity, low cost, and eco-friendliness, making them ideal for lithium-ion batteries(LIBs) and lithium-ion capacitors(LICs) anodes. This study presents the synthesis and thorough characterization of Bi2O3/Co3O4 and Bi2O3/Co3O4/MWCNT composites as potential LIB and LIC anode materials. The materials are synthesized using a hydrothermal process succeeded by annealing. Structural, morphological, and compositional studies were analyzed. Various tests evaluated electrochemical performance, including cyclic voltammetry(CV), confirming a dual storage mechanism like alloying and conversion reaction involved for better energy storage. Specific discharge capacities of 834 mAh/g and 1184 mAh/g were recorded for Bi2O3/Co3O4 and Bi2O3/Co3O4/MWCNT composite electrodes at a current density of 100 mA/g, respectively. The composite material exhibited notably enhanced rate capability, with 31 % and 51 % discharge capacities for Bi2O3/Co3O4 and Bi2O3/Co3O4/MWCNT, respectively. The cyclic stability assessment revealed that Bi2O3/Co3O4 and Bi2O3/Co3O4/MWCNT maintained a high coulombic efficiency of around 99 % over 250 charge–discharge cycles at a high current density of 1 A/g. The capacity retention was approximately 253 mAh/g for Bi2O3/Co3O4 and 439 mAh/g for the Bi2O3/Co3O4/MWCNT composite, indicating excellent cyclic stability and minimal energy loss during cycling. Moreover, the LICs assembly of Bi2O3/Co3O4/MWCNT//CB was investigated, revealing a power density of 200 W kg?1 alongside an energy density of 8.64 Wh kg?1. The cyclic stability assessment over 10,000 cycles exhibits a capacity retention of approximately 45 % under a high current density of 2 A/g. © 2024 Elsevier B.V.Item Enhancing conductivity of Bi2O3 through ‘Fe3+’ doping for pseudocapacitor application(Springer Science and Business Media Deutschland GmbH, 2025) G, L.S.; Bhat, K.S.; Mukesh, P.; Hegde, A.P.; Kumar, A.; Brijesh, K.; Nagaraja, H.S.Binary metal oxides have emerged as pSromising materials for advanced electrochemical energy storage systems due to their superior performance characteristics. In this study, we focus on bismuth oxide (Bi?O?), a material renowned for its high theoretical capacity, wide potential range, and exceptional power density, as a potential candidate for supercapacitors. Iron doping was employed as a strategy to enhance its electrochemical performance and modulate the band gap, thereby improving conductivity and charge storage efficiency. Fe-doped bismuth oxide (Fe-Bi?O?) was synthesized via a solvothermal method with varying iron concentrations (2%, 4%, and 6%), followed by annealing. The pure and iron-doped bismuth oxide samples revealed a combination of monoclinic and cubic phases and a prominent micro-sheet architecture. The introduction of iron doping led to a noticeable reduction in the band gap, highlighting its role in fine-tuning the electronic properties for enhanced energy storage capabilities. The electrochemical evaluation highlighted the 4% Fe-Bi?O? sample as the optimal composition, achieving a remarkable specific capacity of 904 F g?1, a substantial improvement over 101 F g?1 for pristine Bi?O?, at 1 A g?1 in a 2 M KOH electrolyte. Moreover, this sample exhibited outstanding cyclic stability, retaining 104 F g?1 after 2000 cycles at 10 A g?1. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.Item Reinforcing NiO microsphere structural stability via amorphous carbon sheets obtained from waste milk for lithium-ion capacitor application(Springer Science and Business Media B.V., 2025) Lakshmi Sagar, G.; Brijesh, K.; Mukesh, P.; Hegde, A.P.; Kumar, A.; Paliwal, A.; Bhat, K.S.; Nagaraja, H.S.In the pursuit of sustainable chemistry and environmentally friendly energy storage, the study addressed the limitations of nickel oxide utilized as the active material for the anode in lithium-ion capacitors. Despite its abundance and favorable environmental properties, NiO suffered from significant volumetric expansion and slow electrochemical kinetics compared to carbon materials. To overcome these issues, amorphous carbon was extracted from spoiled waste milk through a simple combustion process, effectively converting biomass waste into renewable resources. The engineered NiO/amorphous carbon composite, synthesized through hydrothermal and annealing processes, mitigated the limitations of NiO. Field Emission Scanning Electron Microscopy confirmed the deposition of amorphous carbon sheets encasing NiO microspheres, which preserved structural integrity during electrochemical cycling. The amorphous carbon acted as a stabilizing matrix, encapsulating NiO microspheres to mitigate volumetric expansion and enhance lithium-ion transport kinetics. Electrochemical tests demonstrated a specific discharge capacity of 1230 mAh g?1 at a current density of 100 mA g?1, retaining 401 mAh g?1 after 1000 cycles at 1 A g?1, nearly doubling the retention performance of pristine NiO. Furthermore, the NiO/AC//AC lithium-ion capacitor achieved an energy density of 25.4 Wh kg?1 at a power density of 1991 W kg?1, maintaining 96% capacity after 3500 cycles. This study highlighted the potential of waste-derived carbon in developing high-performance, sustainable energy storage systems. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.