MXene-Supported Vanadium Sulfide Composites Reinforced by Tailored Carbon Nanotube Networks for High-Performance Supercapattery

Abstract

The strategic engineering of multidimensional electrode materials is essential for next-generation hybrid energy storage systems, specifically supercapatteries, which integrate the high energy density of batteries and high-power density of supercapacitors. A rationally engineered composite comprising vanadium sulfide (VS₄) nanosheets uniformly anchored onto 2D MXene (Ti₃C₂T_x) sheets through a facile solvothermal method, further reinforced with carbon nanotubes (CNTs) to construct a 3D conductive network, is demonstrated. The uniform dispersion of VS₄ on MXene, facilitated by strong V─C interfacial bonding, mitigates MXene restacking, enhances electrical conductivity, and stabilizes the hybrid structure. Meanwhile, CNTs further improve electron mobility, reduce particle aggregation, and reinforce mechanical strength. This multidimensional design significantly boosts redox kinetics and cycle stability. The optimized VS₄-MXene-CNT electrode delivers a high specific capacity of 802.46 C g^-1 (1337.44 F g^-1) at 0.3 A g^-1 in 6 M KOH, retaining 97% capacitance after 5000 cycles. The fabricated asymmetric supercapattery device (ASD) exhibits a specific capacity of 148.18 C g^-1 (246.97 F g^-1) at 0.3 A g^-1, achieving specific energy of 12.35 Wh kg^-1 and specific power of 1856.43 W kg^-1, with 93% capacitance retention over 5000 cycles. This work offers a promising route toward designing for durable, high-performance supercapattery electrodes.

Keywords: MXene; carbon nanotube; energy storage; multidimensional hybrid electrode; solvothermal synthesis; supercapattery; vanadium sulfide.

Figure 1

a) Schematic representation of the synthesis route for MXene and MXene‐supported vanadium sulfide composites via an in situ solvothermal method, highlighting each stage from precursor preparation to composite formation. b) Illustration of the complete electrode fabrication process where the active material slurry is uniformly applied onto a nickel foam current collector using the slurry coating technique.

Figure 2

a) XRD patterns of the pure MXene, vanadium sulfide (VS₄), and MXene‐supported vanadium sulfide (MXene‐VS₄) composites. b) XRD patterns of MXene‐VS₄ composites synthesized with various concentrations of MXene.

Figure 3

a) XPS survey spectra of the pure MXene, VS₄, and MXene‐VS₄ composite samples. b–e) High‐resolution XPS spectra of key elements present in the MXene‐VS₄ composites: (b) Vanadium 2p spectrum; (c) Sulfur 2p spectrum; (d) Titanium 2p spectrum; and (e) Carbon 1s spectrum.

Figure 4

FE‐SEM images taken at low (left column) and higher (right column) magnifications for the synthesized materials: a,b) Pure MXene; c,d) VS₄; e,f) MXene‐VS₄ composite (VS‐MX100).

Figure 5

TEM images captured at various magnifications – low magnification to highlight the general morphology, and higher magnification to reveal finer structural details: a–c) Pure MXene; d–f) VS₄; g–i) MXene‐VS₄ composite (VS‐MX100). The inset images of (c,f,i) show the SAED patterns of the corresponding structures.

Figure 6

a) N₂ adsorption–desorption isotherms and b) BJH pore size distribution curves of the MXene, VS₄, and MXene‐VS₄ composite (VS‐MX100) samples, confirming their mesoporous nature and enhanced surface area for improved ion diffusion and energy storage performance.

Figure 7

a) CV analysis of the pristine MXene, pristine VS₄, and VS‐MX100. b) CV analysis of VS‐MX‐based composites, including VS‐MX100 and CNT‐enhanced variants denoted as VS‐MX100‐CNT1, VS‐MX100‐CNT3, VS‐MX100‐CNT5, and VS‐MX100‐CNT10. c) Scan rate‐dependent CV profiles of the optimized composite electrode, VS‐MX100‐CNT5. d) GCD analysis of the MXene, VS₄, and VS‐MX100. e) GCD profiles of the CNT‐reinforced VS‐MX composites (VS‐MX100‐CNT1, 3, 5, and 10), and VS‐MX100. f) Current density‐dependent GCD performance of the VS‐MX100‐CNT5 electrode.

Figure 8

a,b) Electrochemical Performance Analysis: (a) Cyclic stability profiles, and (b) EIS results of the pristine MXene, pristine VS₄, VS‐MX100, and VS‐MX100‐CNT5 electrodes. c,d) Kinetic Analysis: (c) Determination of the b‐values, and (d) Quantification of capacitive versus diffusion‐controlled contributions at various scan rates for the VS‐MX100 and VS‐MX100‐CNT5 electrodes.

Figure 9

Electrochemical evaluation of the assembled ASD employing a PVA–KOH polymer gel electrolyte. a) CV curves recorded at a scan rate of 5 mV s⁻¹ at various potentials ranging from 0.6–1.6 V; the inset displays CV responses at various scan rates from 5 to 100 mV s⁻¹ in a 1.6 V window. b) GCD profiles at current densities ranging from 0.3 to 0.7 A g⁻¹. c) Nyquist plot derived from EIS, providing insight into charge‐transfer resistance and ion diffusion behavior. d) Cyclic stability of the device over 5000 charge–discharge cycles, demonstrating long‐term electrochemical durability.