Nanoflower Electrode Grown by Electrodeposition Pushes Supercapacitors Toward Battery-Level Energy

Supercapacitors have long been the sprinters of the energy storage world: they can charge and discharge in seconds, survive hundreds of thousands of cycles, and deliver bursts of power that batteries simply cannot match. Their Achilles heel has always been energy density, the amount of energy they can pack into a given area or volume. A team of researchers in China now reports a carefully engineered composite electrode that pushes supercapacitor performance significantly closer to battery territory, and they did it by coaxing two remarkable materials into a flower-shaped partnership at the nanoscale.

The study, published in the journal Ionics by Shisen Bo, Ruifeng Liu, Fang Lei, Mei Wang, Tantan Liu, Yuting Liu and Ying Li, describes a nanoflower-like composite built from iron oxyhydroxide (FeOOH) and titanium carbide MXene, written chemically as Ti₃C₂Tₓ. The researchers grew the composite directly onto nickel foam using electrochemical deposition, a technique that is fast, scalable and operates at low temperatures. The resulting electrode delivered an areal specific capacitance of 745 millifarads per square centimetre at a current density of 1 milliampere per square centimetre, a figure that places it among the more capable pseudocapacitive electrodes reported for this class of materials.

The elegance of the work lies in how the two components compensate for each other’s weaknesses. MXenes, a family of two-dimensional carbides first discovered about a decade ago, are prized for their metallic conductivity and their surface chemistry, which can be tuned with terminations such as oxygen, fluorine and hydroxyl groups, collectively denoted Tₓ. But MXene nanosheets have a stubborn tendency to restack, collapsing into dense layers that block the electrolyte from reaching active sites. FeOOH, by contrast, is a rich source of pseudocapacitance, storing charge through fast surface redox reactions, yet it swells and deforms as ions shuttle in and out during cycling, which eventually grinds the electrode apart.

The Chinese team exploited a simple but clever physical principle to assemble the hybrid. Ti₃C₂Tₓ nanosheets carry a negative surface charge in suspension, while iron ions carry a positive charge. Under an applied electric field during electrodeposition, the electrostatic attraction between the two drives Fe³⁺ ions toward the MXene sheets, where they hydrolyse and precipitate as FeOOH. The result is a nanoflower morphology, with petal-like structures blooming across the nickel foam scaffold. This architecture is not merely decorative: the open, flower-like geometry maximises electrolyte access and keeps the MXene sheets propped apart, preventing the restacking that would otherwise strangle the electrode’s performance.

The partnership works in both directions. While FeOOH acts as a spacer that stops the MXene sheets from clumping, the flexible MXene layers in turn cushion the FeOOH against the mechanical stress of repeated charging and discharging. Volume expansion and structural deformation, the classic failure modes of iron oxyhydroxide electrodes, are mitigated by the compliant two-dimensional scaffold. The researchers report that this mutual reinforcement preserves the structural integrity of the electrode over long-term cycling, which is precisely the property that separates laboratory curiosities from practical devices.

To demonstrate real-world utility, the team went beyond testing the composite in isolation and assembled a full asymmetric supercapacitor. The nanoflower-like FeOOH/Ti₃C₂Tₓ electrode served as the anode, paired with a cathode made of manganese dioxide deposited on carbon paper. Asymmetric designs of this kind extend the operating voltage window beyond what a symmetric cell can achieve, because the two electrodes operate in complementary potential ranges. The device achieved an energy density of 270.3 microwatt-hours per square centimetre at a power density of 1003.5 microwatts per square centimetre, numbers that represent a meaningful step toward the energy densities typically associated with battery-type chemistry while retaining capacitor-like power delivery.

Perhaps even more impressive is the device’s endurance. After 15,000 charge-discharge cycles at a current density of 7 milliamperes per square centimetre, the asymmetric supercapacitor retained 86 percent of its initial capacitance. For a pseudocapacitive material that stores charge through redox reactions, which are inherently more structurally demanding than the pure ion adsorption that occurs in carbon-based double-layer capacitors, this level of cycling stability is a strong indicator that the MXene cushioning strategy works as intended. It suggests the electrode does not simply start strong and fade, but maintains its architecture through tens of thousands of ion insertion and extraction events.

The work sits within a broader and rapidly growing research effort to marry MXenes with transition metal compounds for electrochemical energy storage. Recent studies have explored FeOOH-MXene heterostructures for quasi-solid-state asymmetric supercapacitors, MXene composites with layered double hydroxides for potassium-ion supercapacitors, and electrodeposited iron oxyhydroxide on porous graphene for on-chip micro-supercapacitors. What distinguishes the new study is the one-step electrodeposition route, which grows the composite directly on the current collector without binders, high-temperature treatment or multi-stage synthesis. Electrodeposition has attracted increasing attention as a manufacturing strategy for functional energy storage electrodes precisely because it offers fine control over morphology while remaining compatible with roll-to-roll and substrate-based production.

The choice of nickel foam as the substrate also matters. The three-dimensional, highly conductive metallic foam provides an interconnected pathway for electrons and a porous framework that supports high mass loading of active material without sacrificing rate capability. Combined with the nanoflower architecture grown in place, the design minimises the dead volume and interfacial resistance that plague electrodes assembled from powders and slurries. For applications such as wearable electronics, regenerative braking systems, grid frequency regulation and hybrid electric vehicles, where devices must deliver high power in compact footprints and endure relentless cycling, these are the metrics that count.

Challenges remain before such electrodes reach commercial deployment, including scaling the electrodeposition process to large areas, optimising electrolyte systems, and demonstrating performance at the device level under realistic operating conditions. But the study offers a clear design principle: rather than searching for a single miracle material, engineers can pair a high-capacitance but fragile redox phase with a conductive and mechanically resilient two-dimensional scaffold, letting each material protect the other. With supercapacitors increasingly seen as essential complements to batteries in the electrified economy, nanoflower electrodes like this one suggest that the gap between capacitors and batteries is beginning to close, one carefully engineered petal at a time.

Subject of Research: Electrodeposition of a nanoflower-like FeOOH/Ti₃C₂Tₓ MXene composite electrode for high-performance asymmetric supercapacitors

Article Title: Nanoflower-like FeOOH/Ti₃C₂Tₓ composite fabricated by electrodeposition for superior supercapacitor performance

Article References: Bo, S., Liu, R., Lei, F., Wang, M., Liu, T., Liu, Y., & Li, Y. (2026). Nanoflower-like FeOOH/Ti₃C₂Tₓ composite fabricated by electrodeposition for superior supercapacitor performance. Ionics. https://doi.org/10.1007/s11581-026-07465-4

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07465-4

Keywords: supercapacitor, MXene, FeOOH, electrodeposition, nanoflower structure, energy density, pseudocapacitance, asymmetric supercapacitor, nickel foam, cycling stability, energy storage, two-dimensional materials