All-Solid High-Performance Asymmetric Supercapacitor Based on Yolk–Shell NiMoO₄/V₂CT_x@Reduced Graphene Oxide and Hierarchical Bamboo-Shaped MoO₂@Fe₂O₃/N-Doped Carbon

Abstract

The development of high-performance electrochemical energy storage systems is highly desirable for portable and wearable electronic devices. In this study, we proposed a new method to prepare a yolk−shell NiMoO 4 / V 2 CT x @reduced graphene oxide (rGO) composite material using a roomtemperature ionic liquid (RTIL)-assisted hydrothermal method. NiMoO 4 was incorporated into the V 2 CT x MXene layer in the presence of the RTIL 1-butyl-3-methylimidazole tetrafluoroborate ([Bmim]BF 4 ). rGO was coated on the NiMoO 4 /V 2 CT x yolk under electrostatic forces. [Bmim]BF 4 effectively prevents the overoxidation of V 2 CT x MXene during the hydrothermal synthesis of NiMoO 4 and reduces its surface energy, which makes the NiMoO 4 /V 2 CT x @ rGO composite highly stable. This alternating arrangement facilitates the rapid diffusion and transport of electrolyte ions, resulting in excellent electrochemical performance of the NiMoO 4 /V 2 CT x @rGO composites. Bamboo-shaped MoO 2 @Fe 2 O 3 /N-doped carbon (NC) was used as a negative electrode material to assemble a solid asymmetric supercapacitor (ASC) with NiMoO 4 /V 2 CT x @rGO (NiMoO 4 /V 2 CT x @rGO//MoO 2 @ Fe 2 O 3 /NC). The ASC possesses a high energy density of 56.1 W h kg −1 at 800 W kg −1 . The capacitance retention rate remains as high as 90.7% after 5000 cycles, demonstrating that the proposed material has promising performance for supercapacitor applications.

MXene in core–shell structures: research progress and future prospects

“…V 2 AlC MAX powder was used to prepare MXene as the substrate to grow NiMoO 4 and rGO. 180 Fig. 16c shows the resulting yolk–shell NiMoO 4 /V 2 CT x @rGO featuring distinct void spaces between the outer shell and the inner core.…”

MXene-Derived Quantum Dots for Energy Conversion and Storage Applications

“…These are (1) the 2D lamellar morphology enables the fast ion transport and intercalation of different metals ions into the 2D sheet enhance the energy storage performance; (2) high electrical and metallic conductivity enhance the electron transport and increase the capacitive performance; (3) surface redox activity like other transition metal elements; (4) the surface functional group of Ti 3 C 2 T x ( x = −O, −OH, −F) increases the hydrophilicity and significantly impacts the charge-storage mechanism in aqueous electrolytes. Also, the surface functional group supplies abundant catalytic sites and affects the electrocatalytic performance; and (5) its high surface area increases the capacitive behavior. − Thus, MXene-based catalysts exhibit a higher electrocatalytic performance toward energy storage applications. − Further, to increase the energy storage performance, different engineering strategies have been adapted to enhance the capacitance value of MXene and decrease the particle size or synthesize the quantum dots on them. The smaller size lowers the ion diffusion path and makes easy electrolytes available to the catalytic sites, improving energy storage performance.…”

Boosting the Supercapacitive Performance via Incorporation of Vanadium in Nickel Phosphide Nanoflakes: A High-Performance Flexible Renewable Energy Storage Device

“…As supercapacitors offer a specific power density, rapid charge and discharge process, and long-term durability, thus they have emerged as a popular system for certain applications in vehicles, cranes, emerging hybrid automobiles, G-series high-speed trains, and so on. , Nevertheless, supercapacitors are mostly made of a carbonaceous matrix and have some fatal drawbacks of delivering low energy density (∼10 Wh kg –1 ) in modern commercial applications due to a low potential window and limited electrochemically active surface functionality. ,, To overcome this issue, since last decade, asymmetric supercapacitors (ASCs) are assembled by different positive and negative electrode materials to successfully modulate the energy density without disturbing their power density. Currently, researchers have focused on transition metal-based compounds as a positive electrode and carbon-based materials as a negative electrode to enhance the voltage window and overall capacitance of supercapacitors. − Out of which, transition metal phosphides (TMPs) can be investigated as one of the best valuable electrode materials in the fields of electrocatalysis, − batteries, − supercapacitors, − and other energy device applications. , It is due to rich valences, weak ionic bond due to a lower electronegativity, and superior electronic conductivity of TMPs that make them environmentally stable, kinetically favorable for faster charge transport, and sustainable under high applied potentials. , Thus, TMPs have emerged as new battery-type electrode materials and gained more attention because they can improve the specific capacity along with the better rate capability of devices as compared to other electroactive materials. − …”