High-entropy metal oxides (HEMOs) with several functional properties, including high structural stability and superior conductivity, have been recently utilized in energy-storage devices. Morphology control is the key factor to optimizing HEMO performance for successful use in lithium-ion anode materials. Hence, in this study, HEMO ((NiMnCrCoFe)₃O₄) was synthesized via a hydrothermal reaction and subsequent post-annealing process, where cetyltrimethylammonium bromide (CTAB) and urea were used to optimize the morphological structure of HEMO particles to ensure a bimodal distribution. A bimodal particle distribution of HEMO was observed and the electrochemical performance was also investigated for an anode in lithium-ion batteries (LIBs). The proposed bimodal HEMO manifests a superior electrochemical performance compared to existing HEMO, which is controlled by uniform nanoscale or micro-sized secondary particles. The present study shows that collective metal cations with different ionic radii, valence states, and reaction potentials, and a diversification of structures, enable a synergistic effect for the excellent performance of HEMOs in LIBs. The proposed HEMO shows an improved initial discharge capacity of 527 mAh g⁻¹ at a high current density of 5 A g⁻¹ compared to the other referred HEMO systems, and 99.8% cycle retention after 300 cycles. Further, this work allows a new approach for designing multi-element transition metal oxide anode materials using a high-entropy strategy, which can be employed in the development of advanced LIBs.

Porous TiO₂ nanofibers (PTFs) and dense TiO₂ nanofibers (DTFs) were prepared using simple electrospinning for application in dye-sensitized solar cells (DSSCs). TiO₂ nanoparticles (TNPs) were prepared using a hydrothermal reaction. The as-prepared PTFs and DTFs (with a fiber diameter of around 200 nm) were mixed with TNPs such as TNP-PTF and TNP-DTF nanocomposites used in photoelectrode materials or were coated as light scattering layers on the photoelectrodes to improve the charge transfer ability and light harvesting effect of the DSSCs. The as-prepared TNPs showed a pure anatase phase, while the PTFs and DTFs showed both the anatase and rutile phases. The TNP-PTF composite (TNP:PTF = 9:1 wt.%) exhibited an enhanced short circuit photocurrent density (J_sc) of 14.95 ± 1.03 mA cm⁻² and a photoelectric conversion efficiency (PCE, η) of 5.4 ± 0.17% because of the improved charge transport and accessibility for the electrolyte ions. In addition, the TNP/PTF photoelectrode showed excellent light absorption in the visible region because of the mountainous nature of light induced by the PTF light scattering layer. The TNP/PTF photoelectrode showed the highest J_sc (16.96 ± 0.79 mA cm⁻²), η (5.9 ± 0.13%), and open circuit voltage (V_oc, 0.66 ± 0.02 V).

Ni₃S₂ nanowires were synthesized in situ using a one-pot hydrothermal reaction on Ni foam (NF) for use in supercapacitors as a positive electrode, and various contents (0.3−0.6 mmol) of Co(OH)₂ shells were coated onto the surfaces of the Ni₃S₂ nanowire cores to improve the electrochemical properties. The Ni₃S₂ nanowires were uniformly formed on the smooth NF surface, and the Co(OH)₂ shell was formed on the Ni₃S₂ nanowire surface. By direct NF participation as a reactant without adding any other Ni source, Ni₃S₂ was formed more closely to the NF surface, and the Co(OH)₂ shell suppressed the loss of active material during charging–discharging, yielding excellent electrochemical properties. The Co(OH)₂–Ni₃S₂/Ni electrode produced using 0.5 mmol Co(OH)₂ (Co_0.5–Ni₃S₂/Ni) exhibited a high specific capacitance of 1837 F g⁻¹ (16.07 F cm⁻²) at a current density of 5 mA cm⁻², and maintained a capacitance of 583 F g⁻¹ (16.07 F cm⁻²) at a much higher current density of 50 mA cm⁻². An asymmetric supercapacitor (ASC) with Co(OH)₂–Ni₃S₂ and active carbon displayed a high-power density of 1036 kW kg⁻¹ at an energy density of 43 W h kg⁻¹ with good cycling stability, indicating its suitability for use in energy storage applications. Thus, the newly developed core–shell structure, Co(OH)₂–Ni₃S₂, was shown to be efficient at improving the electrochemical performance.