Department of Chemistry
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Item High-voltage LiNi0.5Mn1.5O4 cathodes for Li-ion batteries obtained by sol–gel combustion method: effects of fuel-type and silver doping(Sustainable Energy & Fuels, 2025-09-28) Ehi-Eromosele, Cyril O.; Ajayi, Samuel O.; Ikebudu, Jude N.; Abiaziem, Chioma V.; Mathe, Mkhulu K.High-voltage LiNi0.5 Mn1.5 O4 (LNMO) cathode materials are highly desirable for the fabrication of next-generation lithium-ion batteries (LIBs). In this study, citric acid, glycine, and sucrose fuels were used to optimize the structural and electrochemical properties of LNMO materials obtained by sol–gel combustion synthesis (SCS). The experimental results showed that the type of fuel used in the SCS process influenced the enthalpy of combustion, crystallite size, morphology, cationic disorder and electrochemical properties of the LNMO materials. XRD results indicated that all the LNMO materials have a phase-pure spinel structure with the Fd3m space group. The glycine fuel composition produced LNMO material (LNMO-G) with the least crystallite size, less cationic disorder and the highest crystallinity compared with those having the citric acid fuel (LNMO-C) and sucrose fuel (LNMO-S) compositions. As a result, the LNMO-G cell delivered the highest first discharge capacity of 115.83 mA h g−1 and retained 80.06% of its initial capacity after 200 cycles at a current density of 1C. Moreover, the LNMO-G cell had the best rate capability compared with the LNMO-C and LNMO-S cells, with a discharge capacity of 60 mA h g−1 at a rate of 2C between 3.50 and 5.30 V. Furthermore, Ag doping (LNMAO) improved the rate capability and Li-ion kinetics of the LNMO-G cathode material. The LNMAO cathode achieved a reversible discharge capacity of 100 mA h g−1 at a rate of 2C between 3.50 and 5.30 V. These findings show that LNMO cathode materials can be optimized for ultra-high-voltage (>5.0 V) performance in LIBs for advanced applications.Item Exploring layered lithium-rich spinel composite cathodes for lithium-ion battery obtained by the solution combustion-mechanochemical synthesis(Journal of Alloys and Compounds Volume 1038, 2025-08-20) Ehi-Eromosele, Cyril O.; Ajayi, Samuel O.; Shaaban, Ibrahim A.; Assiri, Mohammed A.; Hessien, Mahmoud M.; Abiaziem, Chioma V.; Sunday, Sam E.; Mathe, Mkhulu K.In this study, layered lithium-rich oxides (LLO) cathode materials were modified with different amounts of the spinel phase to form integrated layered-layered-spinel (LLS) hetero-composites [0.5Li2 MnO3 ꞏ (0.5 − x)LiNi0.5 Mn0.3 Co0.2 O2 ꞏ xLiMn1.5 Ni0.5 O4 (0.05 ≤ x ≤ 0.25)] using a facile solution combustion mechanochemical synthesis method for the first time. The XRD results indicate that all the LLS materials have distinct layered and spinel phases with R3m, C2/m and Fd3m space groups. Notably, the initial coulombic efficiency of the LLS materials increased with increase in the spinel content but showed a reduction both in their charge and discharge capacities. The LLS doped with 5 % spinel content (651LLS), exhibited the best electrochemical performance compared to the ones doped with 15 % spinel content, gave the smallest particle size and the largest unit cell volume. Consequently, the 651LLS cell delivered the highest initial discharge capacity of 279.58 mAh g⁻¹ and a capacity retention of 84.71 % after 50 cycles at a current density of 10 mA g⁻¹ within a voltage window of 2.0 – 4.8 V. Additionally, the 651LLS cell demonstrated superior rate capability with the average capacities 275, 225, 200, 155, and 90 mAh g⁻¹ at 10, 20, 50, 100, and 200 mA g−1. This enhanced performance is attributed to the optimised spinel amount and the smaller particle size which facilitated faster Li-ion transport during cycling. Also, the optimal electrochemical behaviour of the 651LLS cathode is linked to its optimum spinel content (∼5 %) which contributed to its improved structural stability. The results show that the amount of spinel in these LLS materials must be carefully tuned in relation to the operating cycling parameters to produce optimum electrochemical performance.