Development of Amorphous Metallic Surfaces for Energy Storage Applications

Abstract

Amorphous metallic materials have emerged as a promising class of functional materials for energy storage and conversion owing to their disordered atomic structure and unique interfacial properties. This review focuses on amorphous metals and alloys, including metallic glasses and high-entropy amorphous systems, with particular emphasis on their surface- and interface-driven behavior in electrochemical environments. This review analyzes how structural disorder influences key properties such as electronic structure, ion transport, catalytic activity, and mechanical compliance and how these factors govern performance in batteries, supercapacitors, electrolyzers, and fuel cells. Special attention is given to interfacial phenomena, including charge-transfer kinetics, corrosion and passivation processes, and structural evolution during long-term operation. In addition, recent advances in fabrication strategies such as rapid solidification, thin-film deposition, mechanical alloying, thermoplastic forming, and electrodeposition are discussed in relation to their ability to tailor amorphous structures and interfaces. This review also highlights critical failure mechanisms and discusses some strategies to mitigate these effects. Overall, this work provides a focused perspective on the role of amorphous metallic surfaces and interfaces in electrochemical systems, identifying current challenges in scalability, durability, and compositional control, and outlining future directions for their integration into next-generation energy technologies.

1. Introduction

The increasing global demand for energy, driven by technological and societal development, has intensified the need for efficient, reliable, and sustainable energy storage technologies [1]. Electrochemical energy storage systems, including batteries, fuel cells, and supercapacitors, play a critical role in addressing the mismatch between energy generation and consumption [2]. However, their performance is still limited by insufficient energy density, poor cycling stability, and material degradation under operating conditions. Addressing these challenges requires the development of advanced materials with tailored structural and interfacial properties [3].

Material design is a key factor governing the performance of energy storage systems, as the structure, composition, and surface characteristics of electrode materials directly influence ion transport, charge-transfer kinetics, and interfacial stability [4]. While crystalline materials have been widely studied due to their well-defined atomic structures, they often exhibit anisotropic properties, limited active sites, and structural degradation during repeated cycling. These limitations have motivated increasing interest in alternative material systems with enhanced structural flexibility and interfacial functionality [5,6].

Among different systems, amorphous metals have emerged as a promising class of materials for energy storage applications [7]. Their lack of long-range order leads to a high density of unsaturated coordination sites, isotropic behavior, and unique electronic structures, which can enhance electrochemical activity and mechanical resilience [8]. Beyond bulk properties, the surface and interfacial characteristics of these materials are particularly relevant, as electrochemical reactions predominantly occur at interfaces. Amorphous metallic surfaces offer distinct advantages, including uniform energy landscapes, abundant active sites, and the absence of crystallographic defects such as grain boundaries [9], making them highly attractive for improving interfacial processes in electrochemical devices.

In parallel, a wide range of amorphous materials, such as oxides, carbons, sulfides, and phosphates, have been extensively investigated for energy storage applications, demonstrating improved capacity, rate capability, and cycling stability [10,11,12,13,14,15,16,17,18]. However, studies specifically focused on amorphous metallic systems remain comparatively fragmented and are often limited to individual materials or specific applications [19,20,21,22,23]. As a result, a comprehensive understanding of the structure–property–performance relationships governing amorphous metallic surfaces, particularly from an interfacial perspective, is still lacking.

In this context, this review aims to provide a focused and systematic analysis of amorphous metallic materials, with particular emphasis on their surface and interfacial behavior in electrochemical energy storage and conversion systems. By consolidating recent advances, discussing key mechanisms, including interfacial processes and degradation phenomena, and comparing different material systems and fabrication approaches, this work seeks to identify the fundamental principles that govern their performance. Furthermore, current challenges and future research directions are outlined to clarify the unique role of amorphous metallic surfaces and to guide their rational design for next-generation energy technologies.

2. Amorphous Metallic Materials

From a compositional point of view, amorphous metallic materials can be classified into three main categories: single-element amorphous metals, amorphous alloys, and high-entropy amorphous alloys [24]. This classification considers a degree of increasing compositional complexity, which is associated with the number of elements involved in the fabrication of these non-crystalline metals, Figure 1.

Single-element amorphous metals represent the simplest compositional case, as they are composed of one metallic element. Their formation is extremely challenging because pure metals generally exhibit very high crystal nucleation and growth rates during cooling, which strongly suppress vitrification. Nevertheless, various studies have demonstrated that true single-element amorphous metals can be obtained under carefully controlled non-equilibrium conditions, including ultrafast quenching, confined-space quenching, high-pressure routes, and vapor deposition. Reported examples include amorphous Pd, Fe, Ta, V, W, Co, and Ni metallic systems, confirming that amorphization is not restricted to multicomponent alloys [25,26,27].

Amorphous alloys are multicomponent metallic systems composed of two or more constituent elements and represent the most extensively studied class of amorphous metallic materials [28]. The incorporation of multiple elements enhances the glass-forming ability by increasing atomic size mismatch and chemical complexity, thereby suppressing crystallization. Within this category, metallic glasses are more precisely defined as a subclass of amorphous alloys that are specifically formed by rapid quenching techniques from the liquid state and characterized by the presence of a glass transition and, in many cases, a supercooled liquid region prior to crystallization. By contrast, the term amorphous alloy also encompasses non-crystalline metallic systems produced through other non-equilibrium routes, such as physical vapor deposition, electrodeposition, mechanical alloying, or solid-state amorphization, which may not necessarily display the same thermal features typically associated with conventional metallic glasses, i.e., glass transition and supercooled liquid region. Therefore, although all metallic glasses are amorphous alloys, not all amorphous alloys should be strictly referred to as metallic glasses. Representative examples in this category include Fe-, Ni-, Mg-, and Zr-based amorphous alloys, as well as bulk metallic glass systems [29,30,31,32].

Finally, high-entropy amorphous alloys represent the most chemically complex amorphous systems and typically consist of five or more elements in equal or near-equal atomic ratios; they also show low atomic mobility and spatial heterogeneity. By combining high configurational entropy with the structural disorder of the amorphous state, these materials offer expanded compositional design windows and tunable properties [33]. In such systems, sluggish diffusion, severe local structural frustration, and broad compositional tunability promote the stabilization of the amorphous structure and generate unusual combinations of mechanical, electrochemical, and catalytic properties. Co-based and Fe-based high-entropy amorphous alloys are among the most reported examples in the literature [34,35].

3. Short-Range Structures in Amorphous Metals

Although amorphous metallic materials lack long-range atomic order, their atomic arrangement is not fully random. Instead, their structure is governed by well-defined short-range order (SRO) and medium-range order (MRO) [35,36], as schematically illustrated in Figure 2. These local structures play a decisive role in determining their physical, chemical, and electrochemical properties.

SRO refers to the local atomic coordination within the first nearest-neighbor shell, typically extending over one to two interatomic distances (≈2–5 Å). At this length scale, atoms tend to organize into energetically favorable configurations governed by atomic size, bonding characteristics, and electronic interactions. As a result, the local coordination environments in amorphous metals differ significantly from those in crystalline counterparts, leading to broader bond-length distributions and variable coordination numbers [36,37,38]. A widely accepted description of SRO is based on dense atomic packing models, where atoms form distorted polyhedral clusters rather than periodic lattice units [39]. Among these, icosahedral-like clusters are frequently identified as dominant motifs due to their high packing efficiency and inherent geometric frustration, which suppresses crystallization. Other local configurations, such as distorted octahedra or bicapped polyhedra, may also coexist depending on composition and processing conditions [40].

Remarkably, SRO units do not exist in isolation but are spatially interconnected, giving rise to medium-range order. MRO describes the organization and correlation of these local clusters over longer length scales, typically extending from ≈0.5 to 2 nm. Unlike crystalline order, MRO does not imply periodicity; instead, it reflects preferred topological arrangements such as cluster connectivity (e.g., vertex-, edge-, or face-sharing) and the formation of cluster networks. Experimental and simulation studies have shown that such connectivity leads to the emergence of medium-range structural motifs, including icosahedral networks and quasi-equivalent cluster packing configurations, which are essential for understanding structural stability and transport properties in amorphous alloys [40].

The coexistence of SRO and MRO results in a hierarchical structural organization characterized by spatial heterogeneity and topological disorder. In this framework, SRO defines the local atomic packing, while MRO governs how these units are arranged and correlated over extended atomic distances. This structural hierarchy directly influences key material properties, including mechanical strength, diffusion pathways, electronic transport, and resistance to crystallization. Furthermore, variations in composition, atomic size mismatch, and processing routes strongly affect both SRO motifs and MRO connectivity, thereby enabling tunable structure–property relationships in amorphous metallic systems [38,39,40].

4. Implications of Local Structure in Functional Performance of Amorphous Metals

In recent years, advanced characterization techniques such as synchrotron X-ray scattering, pair distribution function analysis, and atomistic simulations have significantly improved the understanding of short- and medium-range structures in amorphous metals [41,42,43]. Despite these advances, establishing direct and quantitative correlations between local atomic configurations and macroscopic performance remains a major challenge. This limitation arises from the intrinsic heterogeneity of amorphous systems, where variations in coordination environments, bond lengths, and cluster connectivity generate spatial fluctuations in electronic structure, bonding strength, and free volume. These local variations are not merely structural features but actively determine functional properties by governing deformation mechanisms, chemical stability, and reaction pathways, particularly at surfaces and interfaces [44,45].

From a mechanical perspective, the influence of local atomic structure is most clearly illustrated in bulk metallic glasses (BMGs), where plastic deformation is governed by shear transformation zones (STZs). The activation of STZs is strongly dependent on local atomic packing efficiency and structural heterogeneity. Recent studies demonstrate that tuning the distribution of densely packed regions increases plastic strain from ~2% to >8% by promoting more homogeneous shear distribution [46]. This behavior reflects a direct structure–property relationship in which SRO and MRO define the spatial distribution of mechanically stiff and compliant regions, thereby controlling deformation pathways at the atomic scale.

A similar structural dependence is observed in chemical stability. In corrosion-resistant amorphous alloys, local atomic environments dictate the formation, composition, and stability of passive oxide layers. For example, alloying additions such as Ta in Zr-based BMGs promote the formation of dense oxide films, reducing corrosion current densities by up to one order of magnitude [47,48]. In contrast, structural relaxation or partial crystallization introduces chemical and topological heterogeneities that act as preferential corrosion sites [49]. These findings highlight that corrosion resistance is not solely a compositional effect but is fundamentally governed by the stability and uniformity of local atomic configurations.

The implications of local structure become even more pronounced in energy-related applications, where atomic-scale heterogeneity directly governs transport and reaction processes. In hydrogen storage systems, the disordered atomic arrangement of amorphous metals creates a broad distribution of interstitial sites with different binding energies, enabling enhanced hydrogen uptake (e.g., ~5–6 wt% in Mg-based systems) and improved diffusion kinetics [50,51,52]. Here, the underlying mechanism is the complex potential energy landscape associated with SRO and MRO, which facilitates reversible hydrogen accommodation without long-range structural constraints. The relationship between local structure and performance extends beyond transport phenomena to include catalytic activity and interfacial stability. Structural disorder modifies ion diffusion pathways, reaction energetics, and phase transformation behavior [53,54,55,56]. For instance, recent studies demonstrate that specific SRO motifs can be actively engineered to optimize electrochemical performance. In Ni–Mo–P–B metallic glasses, slight compositional variations enable the transition between dominant Z9 and Z10 polyhedral motifs, which directly modulate coordination environments and catalytic activity, leading to enhanced sensing performance and reaction kinetics, exhibiting sensitivities of about ~2.2 μA μM⁻¹ cm⁻² and low detection limits down to ~0.3 μM [57]. Similarly, in Pd–Ni–P metallic glass nanoparticles, electrochemical cycling induces MRO rearrangements (from face-sharing to edge-sharing motifs), stabilizing the amorphous structure and preventing crystallization-induced degradation, thereby improving long-term electrocatalytic stability, that is, maintaining high activity over >1000 cycles [58].

Finally, the dynamic nature of amorphous structures further reinforces the importance of local order. Structural relaxation processes, as observed in Fe-based amorphous alloys, lead to measurable changes in electrochemical response, including oxide layer growth and corrosion behavior, as a function of short-range ordering evolution [59]. This demonstrates that local structure is not static, but evolves under operating conditions, continuously redefining structure–property relationships.

These examples demonstrate that the functional performance of amorphous metals is governed not only by composition but fundamentally by the distribution, connectivity, and evolution of local atomic structures. In this context, SRO and MRO act as the primary structural descriptors that define energy landscapes, deformation mechanisms, and reaction environments. However, in practical energy applications, these structure–property relationships are most critically manifested at surfaces and interfaces, where electrochemical and catalytic processes occur. Therefore, particular attention is given to how amorphous surfaces govern interfacial processes and ultimately determine device-level performance in energy conversion and storage systems, as discussed in the following section.

5. Amorphous Surfaces in Energy Conversion and Storage Devices

Amorphous metallic surfaces have emerged as a versatile platform for improving performance across a wide range of energy conversion and storage technologies. Their functional behavior in practical devices, built upon structure–property relationships discussed in the previous sections, is largely governed by the distribution of local atomic environments and the resulting uniformity of reaction pathways at the surface. In this context, the absence of long-range order and the resulting chemical homogeneity at the atomic scale contribute to the formation of more stable and uniform electrode–electrolyte interfaces. These features have been reported to mitigate parasitic reactions, leading to more controlled interfacial processes [60,61,62,63,64,65].

In energy-storage systems, particularly metal-anode batteries (e.g., Zn, Li, Na, and Mg), amorphous surfaces promote more homogeneous ion flux and suppress localized deposition, thereby mitigating dendrite formation and enhancing cycling stability. This effect is especially relevant in aqueous Zn-ion systems, where corrosion and hydrogen evolution typically accelerate performance degradation [66,67]. Amorphous alloy coatings such as Ni–P, Co–P, and Ni–B have demonstrated improved coulombic efficiency and long-term stability under repeated cycling [68,69].

In electrocatalytic environments, including fuel cells and hydrogen-related systems, the disordered atomic structure enables adaptive surface behavior under operating conditions, facilitating stable catalytic activity and resistance to degradation mechanisms such as dissolution or coarsening [70,71,72,73]. For example, nanoporous metallic glass electrodes have shown stable hydrogen evolution performance, with low charge-transfer resistance (~13 Ω) and sustained operation for 20 h at 0.1 A·cm⁻², highlighting their robustness under electrochemical conditions [74].

Amorphous metallic surfaces also exhibit strong performance in supercapacitors and hybrid energy-storage systems [75,76], where their structural flexibility supports rapid charge–discharge cycles and long-term durability. Representative metallic glass electrodes have achieved volumetric capacitances of ≈778 F·cm⁻³ while maintaining high-rate capability and full retention after 8000 cycles, demonstrating their suitability for high-performance and flexible energy-storage applications [77].

Overall, these results illustrate how the local structural features described in Section 3 and Section 4 translate into improved functional performance at the device level. By enabling uniform reaction environments, enhanced mechanical resilience, and stable interfaces, amorphous metallic surfaces provide a robust platform for energy technologies.

5.1. Amorphous Metallic Materials in the Context of Amorphous Systems

A wide range of amorphous materials has been explored for energy storage and conversion applications, highlighting structural disorder as a general design principle across diverse chemistries (Figure 3). Within this broader landscape, amorphous metallic materials can exhibit distinctive behavior compared to other amorphous systems, arising from their metallic bonding and structural disorder. This subsection briefly contextualizes amorphous metallic systems in relation to other amorphous materials, in order to highlight the unique structure–property–performance relationships that distinguish them.

Rather than considering amorphous metallic materials in isolation, their behavior can be more clearly understood when examined along with that of other classes of amorphous systems. As discussed in Section 3 and Section 4, the presence of SRO and MRO governs the distribution of local atomic environments and ultimately controls functional properties. In amorphous metallic systems, this structural framework is coupled with metallic bonding, which enables continuous atomic connectivity and compositional tunability. These features play a key role in defining how structural disorder translates into mechanical response, electrochemical stability, and interfacial behavior.

A useful point of comparison is provided by amorphous transition-metal oxides, such as MnO₂, V₂O₅, Fe₂O₃, Co₃O₄, NiO, and TiO₂. In these systems, structural disorder is primarily manifested through coordination defects and oxygen vacancies, which enhance ionic transport and improve tolerance to repeated ion insertion [10]. However, their electrochemical response is strongly influenced by localized redox processes and specific metal–oxygen bonding configurations, which introduce spatial heterogeneities during operation. In contrast, amorphous metallic systems, where bonding is less directional and more delocalized, tend to exhibit more uniform reaction environments, particularly under dynamic electrochemical conditions.

This distinction becomes more evident when considering amorphous chalcogenides, including MoS₂, WS₂, and metal sulfides/selenides such as FeS_x, CoS_x, and NiSe₂. Here, structural disorder enables reversible conversion reactions and strong interactions with intermediate species, which are critical in Li–S and multivalent-ion batteries [78,79]. Nevertheless, the performance of these materials is closely tied to reaction-specific phase transformations and chemical affinities, whereas in amorphous metallic systems the response is less dependent on discrete reaction pathways and preferentially governed by the continuous distribution of local atomic environments [80].

In other amorphous systems, including phosphates and phosphides (e.g., FePO₄, CoP, NiP), carbon-based materials such as disordered carbons, reduced graphene oxide, and amorphous metal–organic frameworks, structural disorder is primarily associated with stabilizing redox-active frameworks, enhancing electronic conductivity, facilitating ion transport, and buffering volume changes [81,82,83,84,85]. In these materials, the resulting structure–property relationships are often governed by specific local bonding environments, structural motifs, or porosity-driven effects, where electrochemical behavior is closely linked to localized redox processes or adsorption mechanisms.

Amorphous semiconducting systems, particularly amorphous silicon, provide a distinct but complementary example of how structural disorder modifies electrochemical behavior. Unlike metallic systems, amorphous silicon does not exhibit metallic bonding; instead, its response is governed by a covalent network with significant structural flexibility. First-principles calculations have shown that amorphization reduces ion-insertion energies by approximately 0.7–1.8 eV for Li, Na, and Mg species, facilitating a more favorable insertion thermodynamics compared to crystalline silicon [86]. This reduction is associated with a broader distribution of local atomic environments and insertion sites, which enables more homogeneous lithiation pathways and mitigates stress accumulation. Experimentally, this translates into more uniform lithiation fronts, reduced mechanical degradation, and improved cycling stability [87]. These effects are further enhanced in hydrogenated amorphous silicon and composite architectures, where increased network flexibility and more stable interfacial structures contribute to improved electrochemical performance [88,89,90,91].

These examples highlight that, although structural disorder is a unifying feature across amorphous materials, its impact on performance is strongly governed by the underlying bonding characteristics and structural connectivity. In oxide, chalcogenide, carbon-based, and semiconducting systems, disorder often operates through localized structural motifs or reaction-specific pathways. In contrast, amorphous metallic materials exhibit a more collective response, which is consistently reflected across diverse applications,

Table 1. Summary of some amorphous metals, HEAs and MGs reported in the literature.

Material/Composition	Type	Role in Device	Technology	References
a–Si (amorphous silicon)	Amorphous metal	Alloying-type anode film	Li-ion & metal-ion batteries	[64,65]
a–Si:H	Amorphous metal	Thin-film anode	Li-ion; proton batteries	[89]
a–Si/a–Si–HC	Core–shell amorphous	Composite anode	Li-ion	[88]
a–Si nanolayer on graphite	Amorphous metal	Coating for SEAG anode	Fast-charging Li-ion	[90]
3D a–Si on graphene	Amorphous metal	3D supported anode	Ultrafast Li-ion	[91]
Ni–Nb–Zr	Metallic glass	H2-permeable membrane	Hydrogen separation	[93]
Zr–Cu–Al–Ni–Pd	Metallic glass	Electrochemical H host	Hydrogen storage	[94]
Mg–Ce–Ni	Metallic glass	H storage (glass-to-glass)	Solid H storage	[95]
Fe–Si–B–C–Cr	Metallic glass	Negative electrode	Ni–MH batteries	[20]
Cu–Hf–Al	Metallic glass	NPC precursor	Supercapacitors, catalysis	[96]
Mo–Cu–Ti	Metallic glass (nanoporous)	HER electrode	Water electrolysis	[69]
Al–Ni–Co–Y–Cu	Metallic glass	Flexible electrode	Supercapacitors	[97]
Ni–Pd–P–B MG	Metallic glass	Pseudocapacitive/H storage	Alkaline SC, H storage	[98]
Zr–Cu–Al–Ni	Metallic glass	Flow plates, catalyst supports	Micro fuel cells	[99]
Zr–Al–Cu	Thin-film metallic glass	Bipolar plate coating	PEM fuel cells	[100]
Pt–Cu–Ni–P Pd–Pt–Cu–Ni–P	Metallic glass	HOR catalyst	Alkaline fuel cells	[71]
Cu–Zr	Metallic glass	Transparent/flexible electrodes	Wearable supercapacitors	[77]
Ni–Zr–Ti	Metallic glass	Sandwich electrode	Solid-state SC	[78]
Ni–P, Co–P, Ni–B	Amorphous alloys	Protective interlayers	Metal anode batteries	[62,66,67]
Fe-, Ni-, Co-, Cu- based	Metallic glasses	HER/HOR catalysts	Water splitting	[72,73]
Cu–Ti–Mo	Metallic glass	HER electrodes	Electrolysis	[74]
Sn–Si–Co–Cu–P	Amorphous HEA	High-capacity anode	Li-ion	[101]

. For instance, in hydrogen-related systems, metallic glasses such as Ni–Nb–Zr, Fe- and Mg-based alloys enable reversible hydrogen uptake and tunable diffusion pathways without crystallization [20,92,93,94]. In parallel, dealloying of metallic glasses produces nanoporous architectures (e.g., Cu- and Al-based systems) with high surface area and enhanced catalytic or capacitive performance [95,96,97]. In energy-conversion devices, Zr-based metallic glasses and thin-film coatings exhibit improved corrosion resistance and reduced interfacial resistance under fuel-cell conditions [98,99]. Furthermore, multicomponent amorphous and high-entropy systems demonstrate how compositional complexity combined with structural disorder enables high capacity and long-term stability in battery applications [100,101,102]. This response arises from the interplay between SRO/MRO and metallic bonding, which promotes smoother energy landscapes, more uniform reaction environments, and reduced sensitivity to local structural fluctuations, particularly at interfaces where more homogeneous electrochemical behavior and improved stability have been observed under dynamic operating conditions [100].

Despite these advantages, amorphous metallic materials are not free from degradation phenomena and performance limitations under practical conditions. Like other amorphous systems, they undergo structural and interfacial changes that impact long-term stability. These aspects are addressed in the following section.

5.2. Failure Mechanisms of Amorphous Metals

Amorphous metal surfaces exhibit unique electrochemical properties due to their disordered atomic structure; however, this same structural metastability makes them susceptible to various degradation mechanisms under practical operating conditions. One of the primary failure pathways is structural relaxation and crystallization during long-term cycling. Although amorphous alloys lack long-range order, repeated electrochemical insertion/extraction processes (e.g., hydrogen or lithium) induce atomic rearrangements that progressively lower the system’s free energy, leading to partial or localized crystallization. This transition is often associated with a loss of mechanical compliance and reduced electrochemical reversibility, as the amorphous structure originally accommodates volumetric changes more effectively than its crystalline counterpart [89,102].

Another critical degradation mechanism is electrochemically driven corrosion and chemical instability at the electrode/electrolyte interface. Despite the generally improved corrosion resistance of amorphous alloys compared to crystalline materials, prolonged exposure to aggressive electrolytes, especially under polarized conditions, leads to selective dissolution of active elements and modification of surface composition. This process alters the local atomic arrangement and degrades the functional properties of the material. In hydrogen-related environments, corrosion-assisted processes are further coupled with hydrogen absorption and desorption, which may accelerate structural degradation and lead to embrittlement or surface passivation phenomena [89].

Interfacial degradation is also a dominant factor limiting long-term stability. During repeated electrochemical cycling, the formation and evolution of interfacial layers—such as solid electrolyte interphases (SEI) or analogous passivation films—result in increased impedance and loss of active surface area. In amorphous systems, this issue is exacerbated by continuous structural rearrangement and volume changes, which promote the formation of micro-cracks and the progressive loss of electrical contact between the active material and the current collector. For instance, in amorphous silicon-based electrodes, repeated lithiation/delithiation induces significant volumetric expansion and contraction, leading to crack formation, delamination, and eventual capacity fading [89,103]. In Fe-based metallic glasses operating in alkaline media, electrochemical cycling induces the progressive oxidation of Fe⁰ into Fe(OH)₂ and FeOOH, followed by the formation of mixed oxides such as Fe₂O₃ and Fe₃O₄. This evolution is associated with a characteristic activation behavior, where the discharge capacity increases up to ~90 mAh g⁻¹ after ~80 cycles, compared to lower initial values, due to surface roughening and electrochemically active area enlargement [20]. However, continued cycling leads to thickening of the passive layer, increasing charge-transfer resistance and limiting hydrogen diffusion into the bulk alloy. Comparable interfacial stabilization mechanisms have been reported in hybrid systems such as Mn/carbon layered electrodes, where early formation of a stable SEI, detected by in situ techniques (e.g., DEMS and dilatometry), suppresses electrolyte decomposition and enables long-term stability with energy densities up to ~287.7 Wh kg⁻¹ and power densities of ~12.5 kW kg⁻¹ [104]. In addition, XPS depth profiling studies reveal that passive layers in amorphous alloys are often composed of mixed oxides (e.g., Fe-oxide, Cr-oxide, Mo-oxide), with compositional gradients across the thickness. Under proton-exchange-membrane fuel cell (PEMFC) conditions, for a Fe-Cr-Si-based alloy, chromium enrichment at the surface improves corrosion resistance; however, continuous electrochemical cycling can disrupt this protective layer, exposing the underlying alloy to further attack [102]. This cyclic breakdown and reformation of passive films contribute to long-term degradation and performance loss, particularly in aggressive acidic and fluoride-containing environments. Other authors suggest that amorphous alloy electrodes also suffer from parasitic interfacial reactions and unstable solid electrolyte interphase (SEI) formation. For example, in amorphous Al–Si–Mn metallic glass anodes, irreversible electrolyte decomposition during initial cycles leads to significant capacity loss (up to ~30% in early cycles) due to SEI formation and charge consumption [80]. Although amorphous structures can promote the formation of more uniform and stable SEI layers compared to crystalline counterparts, the SEI composition, typically containing LiF, LixPOyFz, and organic carbonate decomposition products, continues to evolve during cycling. This evolution results in thickening of the interphase, increased impedance, and gradual capacity fading. Additionally, preferential surface oxidation (e.g., Al oxidation in Al–Si–Mn systems) alters interfacial chemistry and contributes to voltage hysteresis and kinetic limitations. These results suggest that, regardless of composition, the formation of a thin, ionically conductive and mechanically stable SEI is critical to balancing activation and degradation in amorphous electrode systems.

Additionally, mechanical degradation associated with cyclic stress accumulation plays a crucial role in the failure of amorphous electrode systems. The absence of a crystalline lattice enables initial stress accommodation; however, over-extended cycling and localized strain accumulation generates defects such as voids, shear bands, and micro-cracks. These defects not only compromise structural integrity but also serve as pathways for electrolyte penetration, further accelerating chemical degradation and interfacial instability. Coupling between mechanical damage and electrochemical reactions thus creates a feedback loop that accelerates performance decay [104]. Structural disorder plays a dual role in amorphous metallic systems by enhancing ionic transport while promoting thermodynamic instability. In Al–Si–Ni amorphous alloys, lithium storage occurs through a combination of supersaturated solid solution and nanoscale heterogeneity, where α-Al nanograins (<10 nm) are dispersed within an amorphous matrix. This structure enables high specific capacities, reaching up to ~0.840 Ah g⁻¹ at early cycles and stabilizing around ~0.370–0.660 Ah g⁻¹ after extended cycling, depending on composition (e.g., Al₈₆Si₅Ni₉) [105]. The enhanced performance is attributed to short diffusion paths and high defect density in the amorphous phase. Supporting this mechanism, studies on amorphous oxychloride solid electrolytes (e.g., Li₂O–TaCl₅ systems) have shown that increasing the degree of amorphization via high-energy ball milling raises ionic conductivity from ~6.6 × 10⁻³ to 8.3 × 10⁻³ S cm⁻¹ at room temperature. This improvement is linked to distorted local coordination (e.g., TaCl_6−xO_x units), increased Li–Cl interactions, and reduced migration barriers due to structural disorder [106], boosting the ionic conductivity of amorphous oxychloride solid electrolytes via different degrees of amorphization. However, such defect-rich structures also store significant internal energy, as evidenced by exothermic DSC peaks upon heating, indicating metastability and a tendency toward structural relaxation or crystallization, which may degrade electrochemical performance over time.

Mechanical degradation in amorphous metallic electrodes is strongly associated with phase transformations and volumetric changes during cycling. In Al-based amorphous alloys, lithiation leads to the formation of intermetallic phases such as AlLi, which induces significant volume expansion and local stress accumulation. Although the amorphous matrix partially accommodates these changes, excessive cycling results in pulverization and fragmentation of the electrode, particularly when crystalline phases grow during annealing or cycling. For example, annealed Al–Si–Ni alloys show rapid capacity decay from ~1.379 Ah g⁻¹ to ~0.150 Ah g⁻¹ within ~20 cycles due to grain coarsening and loss of structural buffering [105]. In contrast, as-quenched amorphous alloys exhibit more stable cycling due to their ability to distribute strain more homogeneously. Similar chemo-mechanical degradation has been observed in conversion-type materials such as MnO, where repeated conversion reactions (MnO + 2Li⁺ + 2e⁻ ↔ Mn + Li₂O) generate large volume changes and internal stress, leading to crack formation and electrode disintegration. Despite the absence of grain boundaries in metallic glasses delaying crack propagation, failure still occurs through cumulative localized deformation and interface debonding, highlighting the need for structural stabilization strategies.

In addition to the previously discussed degradation pathways, corrosion-driven compositional instability represents a critical failure mechanism in amorphous metals under realistic electrochemical environments. For instance, Fe-based amorphous alloys such as Fe–Cr–Mo–C–B systems exhibit corrosion behavior that is highly dependent on alloy composition and operating conditions. Under simulated PEM fuel cell environments (1 M H₂SO₄ + 2 ppm F⁻ at 75 °C), alloys with high Cr content (e.g., ~18 at.%) show stable passive behavior with low passive current densities (~0.000078.4 A cm⁻²), whereas alloys with lower Cr content display significantly higher passive currents (~0.00091 A cm⁻²), indicating inferior corrosion resistance [102]. This degradation originates from selective dissolution and the formation of non-uniform passive films, which evolve dynamically depending on whether hydrogen or oxygen environments are present. Furthermore, even when passive layers form (e.g., Cr₂O₃-rich films), their thickness (typically ~2–4 nm) and stability vary under anodic/cathodic cycling, leading to progressive interfacial instability and increased resistance.

Amorphous metallic electrodes exhibit hybrid electrochemical storage mechanisms involving a combination of intercalation, alloying/dealloying, and surface-controlled processes. In Al-based amorphous systems, lithium storage includes both solid-solution insertion into the amorphous matrix and alloy formation (Al–Li), while surface reactions contribute to additional capacity. This is consistent with cyclic voltammetry results showing multiple redox peaks corresponding to SEI formation (~0.55 V), alloying reactions (~0.1–0.2 V), and delithiation processes (~0.6 V) [105]. Analogously, MnO-based layered electrodes demonstrate a multi-electron transfer mechanism combining conversion reactions with surface adsorption and partial intercalation, resulting in high-rate capability and reversible capacities exceeding 0.200 Ah g⁻¹ in LIC configurations [104]. While these hybrid mechanisms enhance power performance, they also introduce kinetic heterogeneity and a non-uniform strain distribution, which accelerate degradation. Therefore, controlling the relative contributions of bulk and surface storage processes is essential to optimize both performance and durability in amorphous metallic systems. The introduction of nanoscale confinement and hierarchical architectures has proven effective in improving the stability of amorphous systems.

In metallic glasses, the coexistence of nanocrystalline phases and amorphous regions creates multiple interfaces that enhance lithium storage and distribute mechanical stress. For example, in Al–Si–Ni alloys, increasing Ni content promotes the formation of a metallic glass matrix that embeds nanoscale α-Al grains, improving cycling stability compared with fully crystalline counterparts. Similarly, in nano-restricted carbon systems, confined domains regulate ion transport pathways and suppress structural collapse, leading to improved cycling stability over hundreds to thousands of cycles [63,106,107]. However, excessive confinement or heterogeneity results in uneven ion flux and localized degradation. In amorphous solid electrolytes, optimal performance is achieved when the amorphous phase is maximized while minimizing insulating crystalline byproducts such as LiCl, whose presence can reduce conductivity by several orders of magnitude (~10⁻⁷ vs. ~10⁻³ S cm⁻¹) [107]. These observations highlight that the careful design of nano- and mesoscale structure is critical to balancing ionic transport, mechanical stability, and long-term durability in amorphous metallic systems.

Based on the aforementioned degradation mechanisms, several optimization strategies can be proposed to enhance the long-term stability of amorphous metallic systems. From a compositional standpoint, the incorporation of corrosion-resistant elements such as Cr and Mo has been shown to promote the formation of stable passive films (e.g., Cr₂O₃-rich layers), reducing dissolution rates and improving interfacial stability under aggressive conditions [102]. Structurally, controlling the degree of amorphization and avoiding excessive crystallization is critical, as partially amorphous systems with nanoscale heterogeneity balance ionic transport and mechanical resilience, as observed in Al–Si–Ni metallic glass systems [105]. Additionally, nanostructuring strategies—such as embedding nanocrystals within an amorphous matrix—have been shown to improve cycling stability by accommodating volume changes and mitigating stress accumulation during repeated lithiation/delithiation processes [63].

Interfacial engineering also plays a key role in the formation of thin, uniform, and ionically conductive SEI layers that minimize continuous electrolyte decomposition and impedance growth. For instance, stable SEI formation in amorphous Al–Si–Mn systems has been associated with reduced irreversible capacity losses (~30% in early cycles) and improved cycling performance [80]. Finally, optimizing electrochemical operating conditions (e.g., potential window, current density, and electrolyte composition) further suppresses parasitic reactions and structural degradation, although these aspects remain less explored for amorphous metallic systems and require further investigation. Altogether, the synergistic combination of composition design, structural control, and interfacial stabilization is essential for improving the durability and practical applicability of amorphous metallic electrodes in energy storage and conversion devices.

6. Fabrication Routes of Amorphous Metallic Alloy Surfaces in Energy Storage and Conversion Applications

To integrate amorphous metals and alloys into devices such as Li-ion batteries, micro-fuel cells, electrolyzers, and hydrogen-storage electrodes, several synthesis pathways enable the formation of metallic amorphous states either as thin films, ribbons, or powders. These routes (see Figure 4) include vapor-phase deposition methods (PVD/CVD), rapid solidification techniques, mechanical alloying–based amorphization, thermoplastic nano-imprinting of pre-formed MGs, and electrochemical deposition–driven amorphization.

Together, they provide a versatile toolbox for engineering metallic amorphous architectures optimized for charge transport, catalytic activity, and structural durability in advanced energy devices. A comparative summary of these fabrication routes is presented in

Table 2. Comparison of fabrication routes for amorphous metallic surfaces.

Method	Key Parameters for Amorphous Phase Retention	Form	Scale	Advantages	Limitations	Example/Performance	References
PVD/CVD	High cooling rates (>106 K/s), deposition temperature, pressure	Thin films	Thickness: nm to μm area: cm2	High uniformity, composition control	High cost, limited thickness	Ni amorphous films prepared by magnetron sputtering (0.48 μm) were deposited on an La1.5Mg0.5Ni6.5Co0.5 alloy (anode, NiMH battery). This film improved the corrosion resistance of the anode around 30%, without capacity decay.	[108]
Rapid solidification	Cooling rates 105–108 K/s, glass forming ability of the alloy	Ribbons	Thickness: μm to mm length: cm to m	Bulk production, good mechanical properties	Limited geometry control	A Ni40Zr20Ti40 metallic glass sandwich electrode (supercapacitor), obtained by melt-spinning. The electrode delivers a high volumetric capacitance of 778 F/cm3.	[77]
Mechanical alloying	Milling time, energy input	Powders	Particle size: nm to μm scalable to kg	Wide compositional flexibility, HEAs production.	High cost, post-processing required	A Mg0.8Ti0.2-xMnxNi (x = 0, 0.025, 0.05, 0.1) amorphous alloy as negative electrode for NiMH batteries with a capacity up to 0.543 Ah/g.	[109]
Thermoplastic forming	Processing temperature within the supercooled liquid region	Structured surfaces	Feature size: nm to μm. device scale: cm	Precise shaping, micro/nano patterning	Requires pre-formed amorphous parts	A Pd40Ni10Cu30P20 alloy as a reversible hydrogen electrode without degradation after 10,000 cycles, being better than conventional Pt/C electrodes.	[110]
Electrodeposition	Potential, pH, current density	Coatings	Thickness: μm area: cm2	Low cost, scalable, conformal coatings	Composition control limitations	Fe–Sb–P amorphous alloy electrodes prepared by electroplating on porous copper current collector for Li-Ion batteries. These electrodes can deliver a discharge capacity of 0.448 Ah/g after 50 cycles.	[111]

, highlighting key process parameters, scalability, advantages, and limitations.

As shown in Table 2, these fabrication routes differ significantly in terms of achievable geometries, processing conditions, and scalability, which directly influence their suitability for specific energy applications. Vapor-phase techniques such as PVD and CVD enable precise control over composition and thickness, making them particularly suitable for the fabrication of thin-film interfaces and micro-scale devices. In contrast, rapid solidification methods allow the production of bulk amorphous structures with high cooling rates, while mechanical alloying offers flexibility in composition design and is especially relevant for powder-based amorphous systems and amorphous high-entropy alloys. Thermoplastic forming provides access to micro- and nano-structured surfaces through processing in the supercooled liquid region, whereas electrodeposition stands out as a scalable and cost-effective route for producing conformal amorphous coatings on complex geometries. The selection of a given fabrication route is therefore not only determined by the ability to achieve an amorphous structure, but also by practical considerations such as processing scale, cost, and integration into device architectures. These approaches are considered complementary pathways for tailoring amorphous metallic surfaces across different length scales and application requirements.

6.1. PVD- and CVD-Based Routes

One of the most widely employed strategies to obtain amorphous metallic surfaces for energy conversion devices involves physical vapor deposition (PVD), particularly magnetron sputtering [112]. TFMGs such as Zr-, Pt-, Cu- or Ni-based glasses can be deposited at sufficiently high cooling rates (>10⁶ K/s) to freeze the disordered atomic structure [113,114]. These thin films have been used in bipolar plates for proton-exchange-membrane fuel cells (PEMFCs) [100], where their amorphous character provides low interfacial contact resistance, superior corrosion resistance, and high durability under acidic conditions. By tuning sputtering power, substrate temperature, and deposition rate, homogeneous amorphous layers of a few micrometers can be produced, as demonstrated for Zr₆₃Al₁₀Cu₂₆ coatings that drastically reduce corrosion currents and maintain metallic conductivity in PEM environments. Similar PVD-deposited amorphous HEA films (e.g., Ti–Zr–Cr–Mn–Fe–Ni, Fe–Mn–Al–Cr–Ti–x) exhibit outstanding hydrogen absorption activity and serve as active layers in hydrogen-storage electrodes or negative electrodes for Ni-MH batteries [115,116].

PVD routes such as magnetron sputtering, thermal evaporation, and electron-beam evaporation remain foundational for producing dense amorphous metallic thin films on current collectors and microdevice structures [117]. These processes quench metal atoms on the substrate at extremely high cooling rates, inhibiting long-range atomic ordering. Amorphous metallic layers produced by sputtering are widely used in micro-fuel cells, microcantilever sensors, and catalytic microreactors because they provide grain-boundary-free, highly uniform films with enhanced corrosion resistance and catalytic uniformity. PVD is often employed for multicomponent alloy processing (e.g., Pt–Cu–Ni–P BMG films), enabling tunable compositions and fast incorporation into MEMS-scale energy devices [118].

Chemical vapor deposition methods such as LPCVD and PECVD are among the most reliable techniques to prepare thin amorphous metallic or metalloid films, particularly for Si-based, Ge-based, and metal/metalloid alloy systems used as battery anodes or catalytic layers [27,119]. LPCVD allows the deposition of amorphous silicon films (a-Si) at moderate temperatures before crystallization kinetics become dominant. These amorphous metallic layers can be grown as highly conformal coatings on conductive substrates, which is crucial for improving interfacial stability, suppressing pulverization, and enhancing cycling life in LIBs [119]. PECVD provides high deposition rates at low temperatures, enabling uniform amorphous metallic coatings on carbonaceous or metallic substrates for industrially scalable battery electrodes.

6.2. Melt-Spinning and Rapid Solidification Techniques

For thicker metallic components in energy-harvesting systems or battery current collectors and electrodes, rapid solidification methods such as melt spinning, planar flow casting, and copper-mold suction casting are key routes to produce MGs [120,121,122,123]. These methods generate cooling rates between 10⁵–10⁸ K/s, enabling the formation of fully amorphous ribbons or plates. Such amorphous ribbons have been investigated as catalyst supports, current collectors, or micro fuel-cell components [110,124]. In micro fuel cells, Zr-based BMG ribbons embossed by thermoplastic forming enable the fabrication of micro-flow-fields and current collectors with excellent corrosion resistance, replacing stainless steel and silicon [125]. Likewise, amorphous HEAs synthesized by rapid solidification (e.g., Ti-based HEA ribbons) show high hydrogen absorption capacity at room temperature, making them suitable for hydrogen-storage electrodes and anodes for Ni-MH batteries [126].

6.3. Amorphization Through the Mechanical Alloying Route

Mechanical routes such as high-energy ball milling and cryomilling provide another major pathway to synthesize amorphous metallic alloys and amorphous HEAs [127]. High-energy deformation disrupts the long-range order of crystalline precursors, producing amorphous powders that can be consolidated into coatings or electrodes. These methods are widely used to create amorphous HEA-based and composite anodes for lithium-ion and sodium-ion batteries [101,102]. For example, amorphous Sn–Si–Co–Cu–P high-entropy alloys produced by ball milling exhibit large initial discharge capacities (>1.800 Ah·g⁻¹) and exceptional lifecycles when hybridized with graphite. Mechanical alloying is especially valuable for compositions that are difficult to vitrify using melt quenching; repeated fracture and cold welding of multi-component HEAs facilitates the formation of amorphous high-entropy metallic states that show enhanced reaction kinetics, high diffusivity of Li⁺/H atoms, and improved structural stability during cycling [128].

6.4. Thermoplastic Forming and Nano-Imprinting of Metallic Glass Surfaces

Once an amorphous metallic alloy is obtained, thermoplastic forming (TPF) can be employed to create micro- and nano-structured surfaces useful for energy devices. Operating within the supercooled liquid region, TPF enables the shaping of metallic glasses into flow-fields, micro-lattices, electrodes, micro-cantilevers, or catalytically active textures [129]. This is particularly relevant for PEM fuel cells [130], where patterned metallic flow plates reduce pressure drop and enhance catalyst utilization. Nano-imprinting on amorphous metals also improves the electrochemically active surface area, enhancing electron transport and reaction kinetics in electrocatalytic electrodes for electrolyzers [130,131]. The key advantage is that the amorphous structure allows for defect-free forming without grain-boundary cracking, enabling scalable manufacturing of complex metallic architectures.

6.5. Electrochemical Amorphization of Metallic Alloys

Although electrodeposition typically yields crystalline metals, carefully controlled electrochemical conditions yield amorphous metallic alloys, especially multicomponent Ni-, Co-, Fe-, or transition-metal-rich systems [132]. By tuning deposition potential, pH, and current density, it is possible to deposit metallic layers where high configurational entropy or atomic-size mismatch suppresses crystallization. These electrodeposited amorphous metallic films are promising for supercapacitor current collectors, electrode scaffolds for electrocatalysis, and hydrogen-evolution electrodes, where metallic conductivity and structural homogeneity are essential [133,134]. In some systems, the electrochemical cycling itself induces amorphization, such as repeated metal-ion insertion/extraction in multi-component alloys, enabling the creation of in situ amorphized metallic electrodes with high defect density and improved reaction sites [110].

7. Perspectives and Conclusions

Amorphous metallic materials constitute a versatile and unifying platform for a wide range of energy-related applications, including supercapacitors, batteries, electrocatalytic systems, and solar energy devices. Across these technologies, performance is increasingly governed by surface- and interface-dominated phenomena rather than bulk properties [135,136,137]. In this context, the intrinsic structural disorder of amorphous materials provides a unique advantage by enabling chemically homogeneous, defect-tolerant, and mechanically compliant interfaces. Looking forward, the future development of amorphous metallic materials for energy applications can be guided by four key research priorities, which are outlined below.

(1)

Atomic-level control of structure and composition. A fundamental challenge lies in achieving precise control over composition, thickness, and local atomic structure, particularly at surfaces and interfaces. Recent advances highlight that short- and medium-range order, as well as local chemical environments, critically determine electrochemical behavior and stability [40]. In addition, emerging studies highlight that establishing quantitative relationships between atomic structure and functional properties remains a key bottleneck for amorphous systems, due to their intrinsic heterogeneity [21]. In this context, so-called structural descriptors—such as coordination numbers, bond-length distributions, and local atomic motifs—are used to represent the disordered structure in a simplified and quantifiable manner. However, unlike crystalline materials, where periodicity enables straightforward structure–property correlations, the lack of long-range order in amorphous systems makes it challenging to identify universal descriptors that reliably predict performance. Therefore, developing strategies to tailor atomic packing, chemical heterogeneity, and electronic structure, especially in multicomponent and high-entropy amorphous systems, represents a primary research direction [138,139].

(2)

Interface engineering under realistic operating conditions. While amorphous materials exhibit intrinsic advantages such as the absence of grain boundaries and improved mechanical compliance, their long-term stability under realistic conditions (e.g., electrochemical cycling, thermal fluctuations, and mechanical stress) remains insufficiently understood. In particular, dynamic disorder–order transitions and interfacial evolution during operation have been identified as critical factors influencing performance degradation and reversibility [21,40]. Systematic studies combining in situ/operating characterization and multiscale modeling are therefore essential.

(3)

Scalable fabrication and data-driven materials design. Translating laboratory-scale materials into practical devices requires scalable and cost-effective manufacturing routes. As discussed in Section 6, several established fabrication strategies, including PVD/CVD, rapid solidification, mechanical alloying, and electrochemical deposition, provide versatile pathways to obtain amorphous metallic structures with controlled properties. In this context, emerging techniques such as thermal spray (cold spray and plasma spray) can be regarded as promising extensions of these approaches toward large-area and industrial-scale production. These methods enable the deposition of thick, dense metallic coatings while preserving the amorphous structure due to rapid solidification upon impact, offering clear advantages for device integration. Although widely explored for crystalline alloys in batteries and hydrogen-related systems, their application to amorphous metallic alloys remains comparatively limited, representing a significant opportunity for future research [140,141,142,143]. At the same time, data-driven approaches and machine learning are increasingly recognized as powerful tools to accelerate the discovery of amorphous materials by linking structural descriptors with catalytic or electrochemical performance. The integration of scalable fabrication with computational and data-driven design frameworks is therefore expected to significantly accelerate materials optimization [21].

(4)

Expansion to new chemical compositions and energy systems. Current research is largely focused on a limited set of amorphous alloy compositions and Li-based systems. However, emerging battery chemistries, including Na-, K-, Zn-, Mg-, and multivalent systems, present significant opportunities where amorphous materials can mitigate phase transitions, suppress dendrite formation, and enable flexible reaction pathways [86,144]. In parallel, the compositional design space of amorphous alloys, particularly high-entropy systems and heterostructures, remains far from fully explored, offering vast potential for discovering new structure–property relationships [145,146].

Overall, these priorities highlight that future progress will depend on integrating atomic-level design, interface stability, scalable processing, and compositional innovation. At the core of this review, a central insight emerges: the unique performance of amorphous metallic materials arises from the interplay between structural disorder (SRO/MRO), tunable chemical environments, and interface-dominated processes, which collectively govern ion transport, catalytic activity, and mechanical stability. However, translating these advantages into practical energy devices requires meeting several critical conditions, including precise control over atomic structure and composition, stabilization of interfaces under realistic operating environments, and the development of scalable and reproducible manufacturing routes. In addition, bridging the gap between fundamental structure–property understanding and device-level performance, potentially through data-driven design and in situ characterization, will be essential. By fulfilling these conditions, amorphous metallic materials can transition from promising laboratory systems to enabling platforms for next-generation energy technologies, where their intrinsic structural disorder is not a limitation but a design advantage for achieving adaptive, durable, and high-performance devices.