Superionic-conductor-modified nickel foam enables region-induced deposition for stable sodium anodes

Abstract

The practical application of Na metal batteries is severely hindered by uncontrolled Na dendrite growth and large volume fluctuations, which lead to safety hazards and poor cycling stability. Herein, we designed a composite 3D Ni foam skeleton modified with fast-ion conductor (FIC) networks to achieve dual ionic/electronic conductivity, enabling spatially guided Na deposition and confined growth. The FIC modification exhibits strong Na⁺ affinity, which ensures uniform ion distribution and directs Na deposition preferentially within the porous Ni framework rather than on its surface. This unique structure facilitates region-induced deposition and spatial confinement of Na metal, effectively suppressing dendrite formation and mitigating volume expansion. Moreover, the FIC network significantly enhances Na⁺ transport kinetics during plating/stripping processes, improving electrochemical reversibility. As a result, the FIC-modified 3D Ni host provides stable Na metal anodes with a prolonged cycling life and reduced polarization. The symmetric cells exhibit stable operation for 300 hours at 0.5 mA cm⁻² and 2 mAh cm⁻², while full cells demonstrate an outstanding capacity retention of 94.6% at 5C over 400 cycles. This work presents a rational electrode design strategy that combines guided ion redistribution and physical confinement to achieve dendrite-free Na metal anodes, providing new insights for developing high energy density Na-based batteries.

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Introduction

The escalating demand for sustainable and electrochemical energy storage systems has positioned sodium metal batteries (SMBs) as a complementary candidate to lithium-ion batteries, owing to sodium's natural abundance, low cost, and high specific capacity (1166 mAh g⁻¹).^1–4 However, the intrinsic challenges associated with sodium (Na) metal anodes significantly constrain their practical applicability, such as uncontrollable dendrite growth and significant volume fluctuations during cycling.^5–7 Dendrite formation not only generates electrochemically inactive “dead sodium” that accelerates capacity fading, but also poses serious safety risks, including internal short-circuits and potential thermal runaway.^8,9 Moreover, repetitive Na deposition/stripping induces mechanical stress, leading to large volume fluctuations and rapid performance degradation.^10,11

To address these challenges, extensive research efforts have been focused on developing strategies to control sodium deposition and improve the stability of the Na⁺ (de)intercalation process. One of the most investigated approaches is using three-dimensional (3D) conductive frameworks as Na hosts. These frameworks, including metal foam,^12,13 carbon scaffolds,^14–16 and metal–organic framework-derived carbon structures,^17,18 offer large surface areas, excellent electronic conductivity and interconnected pore structures. Such properties enable them to buffer volume changes during Na deposition/dissolution and reduce the local current density.^19,20 Nevertheless, conventional 3D conductive frameworks suffer from a critical limitation: sodium ions tend to preferentially deposit on the external surface of 3D frameworks rather than distribute uniformly within interior pores.²¹ This undesirable surface-dominant deposition behavior is primarily attributed to three factors: (i) uneven ion flux distribution. The high electronic conductivity of metal/carbon frameworks drives rapid electron transfer to the surface, creating localized high-current-density zones that favor top-layer Na plating. (ii) Sluggish ionic diffusion. Without efficient ion-conductive pathways, Na⁺ migration into deeper regions of the framework is kinetically hindered, leading to concentration polarization and superficial deposition. (iii) A concentrated electric field. Na preferentially deposits at the top of the framework, while its penetration into the interior is hindered by the non-uniform electric field distribution.^22,23 Consequently, Na accumulates unevenly on the framework surface, forming protrusions that evolve into dendrites, eventually undermining the benefits of 3D conductive hosts.

Recent studies proposed integrating sodiophilic materials with 3D frameworks to guide uniform Na deposition. For instance, Shi et al. prepared Co-doped Ni₃S₂ modified Ni foam as a substrate for Na deposition.²⁴ The high sodiophilicity of Co–Ni₃S₂ provides abundant nucleation sites, enabling uniform Na deposition. Kang et al. dispersed SnO₂ quantum dots on 3D carbon cloth, leveraging the high affinity between SnO₂ and Na.²⁵ This interaction enables SnO₂–Na alloying, reducing the sodium nucleation barrier and guiding site-directed, dendrite-free Na plating. Notably, fast ion conductor (FIC) sodiophilic materials, such as Na₃V₂(PO₄)₃, offer unique advantages by combining sodiophilicity with high ionic conductivity.^26,27 When decorated onto 3D frameworks, the FIC materials can uniformly distribute the Na-ion flux through strong adsorption affinity and realize low-barrier nucleation, directing Na deposition into the framework's interior pores. Moreover, the rapid Na⁺ migration capability enhances electrode kinetics during plating/stripping.

Herein, we constructed a FIC-modified 3D Ni foam (NF@FIC) to achieve dual ion/electron conductivity and spatially regulated Na deposition. The FIC material (Na₃V₂(PO₄)₃) anchored to the Ni foam surface exhibits strong adsorption affinity towards sodium ions, enabling uniform Na-ion dispersion and a low nucleation barrier. This facilitates region-induced deposition within sodium metal anodes. By directing Na deposition into the interior pores of the 3D Ni framework, the composite structure creates a confined growth environment for sodium metal. This confined growth not only suppresses sodium dendrite formation, but also effectively mitigates volume changes associated with sodium deposition and stripping. Furthermore, the FIC material significantly enhances electrode kinetics by facilitating rapid Na⁺ migration during both plating and stripping processes. This ensures efficient ion transport and improves the overall electrochemical reversibility of the anode. As a result, the composited Na-NF@FIC anodes demonstrate exceptional cycling stability (300 h at 0.5 mA cm⁻², 2 mAh cm⁻² in symmetric batteries) and superb rate capability (74.4 mAh g⁻¹ at 30C in full cells), outperforming the pristine 3D Ni hosts.

Experimental section

Preparation of the NF@FIC framework

The modified host was prepared through a hydrothermal method followed by calcination. Commercial nickel foam (NF, thickness: 0.5 mm, Canrd Co. Ltd) was cut into 3 × 5 cm² pieces and treated with concentrated hydrochloric acid for 2 min to remove surface oxide layers and impurities. The treated NF was subjected to ultrasonic cleaning with deionized water (three times) and ethanol (once), followed by natural drying for further use.

To prepare the hydrothermal reaction solution, Na₂CO₃ (1.5 mmol, 0.1598 g), NH₄H₂PO₄ (3 mmol, 0.3453 g) and V₂O₅ (1 mmol, 0.1824 g) were dissolved in 70 mL deionized water under stirring for 20 min. Subsequently, polyethylene glycol (PEG-4000, 0.005 g) and lauryl sodium sulfate (SDS, 1.25 mmol, 0.3649 g) were added and stirring was continued for another 20 min. For comparison, control solutions were prepared (i) without SDS&PEG-4000 and (ii) with SDS&PEG-4000 only.

The pretreated NF was immersed in the reaction solution within a Teflon-lined autoclave and kept at 180 °C for 24 h. Subsequently, the sample was freeze-dried for 12 h. The dried sample was annealed in a tube furnace under an Ar atmosphere. The thermal treatment consisted of a 4 h preheating step at 350 °C, followed by a ramping to 750 °C at a rate of 2 °C min⁻¹ and holding for 6 h, yielding the final NF@FIC substrate. The control groups were labeled as NF@FIC-noSDS&PEG (without SDS&PEG-4000) and NF-SDS&PEG (with SDS&PEG-4000 only).

Fabrication of the NVP cathode

The Na₃V₂(PO₄)₃ (NVP) cathode was fabricated via a slurry-coating process. The slurry consisted of the active material (NVP, Canrd Co. Ltd), conductive carbon (Super P), and a binder (polyvinyl difluoride, PVDF) in a weight ratio of 7 : 2 : 1. The solvent of the slurry is N-methyl-2-pyrrolidone (NMP). The homogeneous slurry was coated on the Al foil current collector and dried at 90 °C under vacuum for 12 h. The dried electrode was cut into wafers with a diameter of 12 mm. The mass loading of NVP was controlled at approximately 2 mg cm⁻².

Materials characterization

Scanning electron microscopy (SEM, JSM-6360LV) coupled with energy-dispersive spectroscopy (EDS) was used to analyze the morphological characteristics and elemental distribution of samples. X-ray diffraction (XRD) patterns were collected on an Empyrean diffractometer with Cu Kα radiation (2θ range: 10–80°). Surface electronic states were analyzed by X-ray photoelectron spectroscopy (XPS, K-Alpha). A Micromeritics ASAP2020Plus analyzer was used to determine the specific surface areas by nitrogen physisorption measurements.

Electrochemical measurements

All cells were assembled in an Ar-filled glove box using CR2032 coin cells. A glass fiber separator (Whatman GF/D) was employed, while the electrolyte consisted of 1 M NaClO₄ dissolved in PC with 5% FEC additive. The composite sodium anode (Na-NF@FIC) was gained by galvanostatic deposition of 10 mAh cm⁻² sodium metal onto the NF@FIC framework at a current density of 0.1 mA cm⁻². For comparison, the pristine NF substrate was subjected to the same electrodeposition process to prepare the control anode (designated as Na-NF). The electrochemical performances were measured by using a Neware battery test system and cells were tested in a 30 °C thermotank. In order to observe the deposition of Na plating in reality, a symmetric cell was assembled in the Swagelok cell to optically observe Na deposition. The galvanostatic intermittent titration technique (GITT) was employed at a current density of 0.5 mA cm⁻², with 10 min charge/discharge intervals followed by 40 min relaxation periods. Electrochemical Impedance Spectroscopy (EIS) measurements were conducted over a frequency range spanning from 100 kHz to 0.01 Hz, employing an amplitude of 5 mV. Cyclic voltammetry (CV) was carried out at a scan rate of 0.1 mV s⁻¹ using an electrochemical workstation (VSP, Biologic). Symmetric cells were subjected to EIS analysis at various cycles under room-temperature conditions. Tafel curves were acquired through linear sweep voltammetry (LSV) at a scan rate of 1 mV s⁻¹. Full cells were assembled using NVP cathodes and the Na-NF@FIC anode, with an operational voltage window of 2.3–4.0 V. Control experiments were performed using the Na-NF composite anode and pure Na foil as the anode.

Results and discussion

Fig. 1a schematically illustrates the structure of the NF@FIC substrate. The NF@FIC skeleton first undergoes hydrothermal treatment to ensure uniform growth of the NVP precursor on the Ni foam surface. Subsequent annealing under an inert atmosphere anchors NVP products onto the 3D host structure. During hydrothermal synthesis, surfactants (SDS, PEG-4000) play a critical role in dispersing NVP particles. As shown in Fig. S1 in the SI, surfactant-free NF@FIC exhibits severe NVP particle agglomeration and restricted growth, confirming that surfactants promote well-dispersed NVP crystallization. Furthermore, these surfactants undergo in situ pyrolysis during thermal treatment, forming a continuous carbon coating on the NVP particle surface.²⁸ The optical photograph reveals significant darkening of the NF@FIC skeleton compared to pristine NF (Fig. S2), confirming the incorporation of black NVP particles. SEM images demonstrate that the NF@FIC retains its 3D porous architecture after calcination (Fig. 1b). Notably, NF@FIC exhibits dense and even coverage of needle-like NVP particles on the Ni metal surface (Fig. S3b), whereas the pristine Ni foam retains a smooth and uncovered surface after identical treatment (Fig. S3a). To investigate the impact of calcination temperature, control samples were synthesized at 650 °C (NF@FIC-650) and 850 °C (NF@FIC-850). As shown in Fig. S4, both samples exhibit more heterogeneous NVP distribution and severe agglomeration compared to the optimized sample NF@FIC calcined at 750 °C. Correspondingly, their sodium nucleation overpotentials (20.2 mV and 22.4 mV, respectively, Fig. S5) are significantly higher than that of the 750 °C benchmark. The inferior performance at 650 °C is attributed to incomplete NVP phase formation and low crystallinity due to insufficient thermal energy. The 850 °C sample likely suffered from structural degradation or element volatilization, leading to non-uniform NVP distribution and increased nucleation energy barriers. Nitrogen physisorption analysis (Fig. S6) indicates that the NVP-modified 3D framework exhibits a more pronounced microporous structure compared to bare Ni foam.²⁹ The specific surface area of NF@FIC (0.6560 m² g⁻¹) nearly doubles that of bare NF (0.3826 m² g⁻¹), confirming successful NVP anchoring on the Ni surface. Fig. 1c presents the XRD patterns of NF and NF@FIC, where distinct peaks corresponding to the (104), (113), (024) and (211) planes of NVP (PDF #053-0018) confirm its successful loading. The weak intensity of the NVP peaks is likely due to the low mass loading and high dispersion of the NVP layer. The strong background signal of Ni foam can also overshadow the weak diffraction signals, making the NVP peaks appear less intense by comparison. XPS analysis (Fig. 1d and S7) further verifies the presence of NVP, with characteristic V 2p_1/2 and V 2p_3/2 peaks observed at 523.9 eV and 517.4 eV, respectively, along with a distinct P 2p peak at 133.3 eV. EDS mapping (Fig. 1e and Fig. S8) confirms that the coating consists of Na, P, O and V elements. The NVP-functionalized NF surface combines excellent sodiophilicity with high ionic conductivity, offering numerous nucleation sites and fast ion-transfer channels for Na⁺. This composite NF@FIC skeleton is expected to demonstrate dual ion/electron conductivity, facilitating low-energy nucleation and dendrite-free growth.

Fig. 1 (a) Schematic illustration of NF and the NF@FIC skeleton. (b) SEM image of NF@FIC. (c) XRD patterns of NF@FIC and bare NF, with a zoomed-in view of the selected range for NVP diffractions. (d) XPS spectra of V 2p and P 2p for NF@FIC. (e) EDS mappings of NF@FIC.

The nucleation behavior of Na metal significantly influences its subsequent deposition and stripping processes. The unique sodiophilic feature of NF@FIC with uniformly dispersed NVP particles and an increased specific surface area can effectively regulate Na⁺ adsorption and nucleation dynamics. Fig. 2a presents the deposition curves of NF@FIC and the bare NF skeleton. During sodium deposition, the FIC network preferentially attracts Na⁺ ions and undergoes a sodium intercalation reaction at potentials below 1 V. The sodiation capability of NVP (Na₃V₂(PO₄)₃ + Na⁺ + e⁻ ↔ Na_3+xV₂(PO₄)₃) enhances the substrate's affinity for Na⁺. This process homogenizes Na⁺ distribution and directs ion migration toward the 3D framework interior, guiding inward sodium deposition within the scaffold. In contrast, the deposition profile of the pristine NF exhibits an immediate transition to the Na plating regime without prior sodiation. Fig. 2b and Fig. S9–S10 compare the nucleation overpotentials of sodium on various substrates at 0.1 mA cm⁻². Cu foil exhibits the highest nucleation overpotential of 77.8 mV, while the NF substrate shows a reduced value (52.4 mV), attributable to its excellent electron conductivity. Furthermore, the modified NF@FIC shows the lowest nucleation overpotential of 7.8 mV, indicating the superior sodiophilicity and low nucleation barrier. To evaluate the effect of surfactants, the nucleation behavior of the surfactant-free framework (NF@FIC-noSDS&PEG) and the surfactant-only modified framework (NF-SDS&PEG) was further investigated. As shown in Fig. S11, the NF-SDS&PEG substrate exhibits a nucleation overpotential of 66.9 mV, which is significantly higher than that of the NF@FIC scaffold (7.8 mV). This result indicates that the reduced nucleation overpotential of the NF@FIC substrate is not primarily caused by the carbon layer derived from surfactant decomposition. Furthermore, the NF@FIC-noSDS&PEG sample, synthesized without SDS and PEG-4000 displays a higher overpotential (46.5 mV), likely due to the non-uniform growth of NVP. These findings suggest that the surfactants facilitate the uniform growth of the fast-ion conductor layer during the hydrothermal process, thereby improving the sodiophilicity of the composite substrate and promoting more stable sodium deposition. Additionally, the electrochemical performance of NF subjected to deionized water hydrothermal treatment and calcination was tested to verify the effects of the hydrothermal and calcination processes on the performance. As shown in Fig. S12, the treated NF exhibits a comparable nucleation overpotential to bare NF and the symmetric cell assembled with Na-treated NF shows normal cycle ability, indicating that treatment protocols exert negligible influence on the resultant experimental outcomes. An elevated nucleation overpotential typically promotes island-like deposition rather than planar growth, exacerbating dendrite formation.^30,31 Consequently, the diminished nucleation overpotential of the NF@FIC skeleton facilitates planar sodium electrodeposition instead of vertical growth. This result demonstrates that the NVP-modified 3D framework offers superior nucleation behavior and a more favorable electrodeposition environment compared to pristine Ni foam. This dual electron–ion conductive architecture enables low-barrier nucleation and region-induced internal deposition within the composite framework. Such uniform nucleation promotes more stable and homogeneous sodium plating, effectively suppressing dendrite formation and enhancing the overall cycling stability of the Na metal anode.

Fig. 2 (a) Deposition curves of Na platting on Na-NF@FIC and Na-NF. (b) Nucleation overpotential of Na deposit on NF@FIC, NF and Cu foil. (c) Schematic of Na atom adsorption on Ni (111), Na (100) and NVP (116). (d) DFT calculation of the adsorption energy of Na on Ni (111), Na (100) and NVP (116). (e) Schematic representation of the Na deposition process on NF and NF@FIC.

DFT calculation was employed to explore Na atom adsorption energies on different substrates.^32–36 It should be noted that the calculated “Na adsorption energy” serves as a quantitative descriptor of the substrate's intrinsic affinity for sodium, rather than representing the actual solvated Na⁺ environment. As shown in Fig. 2c and d, the NVP substrate exhibits the most negative adsorption energy (−1.89 eV), confirming its superior sodiophilicity and preferential deposition at NVP sites. In contrast, metallic Na (−0.90 eV) and Ni foam (−0.66 eV) show weaker Na atom affinity. This thermodynamic preference directly impacts the sodium deposition morphology. As depicted in Fig. 2e, non-uniform sodium deposition occurs due to tip effects and poor sodium affinity on bare NF substrates, ultimately causing surface dendritic growth.^37,38 Conversely, the uniform NVP distribution throughout the NF@FIC matrix provides abundant sodiophilic nucleation sites, regulating Na⁺ flux distribution and enabling low-energy barrier Na deposition. During this process, Na⁺ migrates toward sodiophilic NVP sites, directing Na⁺ diffusion into pore channels and confined growth within pore cavities, while avoiding the aggregation Na growth on the NF substrate surface.

Galvanostatic charge/discharge tests were carried out to assess the cycling properties of symmetric cells. As shown in Fig. 3a, the Na-NF@FIC||Na-NF@FIC cell exhibits a reduced overpotential and improved cycling stability (300 h) at 0.5 mA cm⁻² and 0.5 mAh cm⁻² compared to other configurations. Notably, both Na-NF (∼35 mV) and Na-NF@FIC (∼30 mV) cells demonstrate lower overpotentials than the bare Na counterpart (∼90 mV) (Fig. S13a). Even though the unmodified NF substrate lacks NVP functionality, the Na–NF composite anode still outperforms bare Na due to Ni foam's high electron conductivity and volume expansion buffering effect. However, its cycling stability at 0.5 mA cm⁻² and 0.5 mAh cm⁻² remains inferior to that of Na-NF@FIC cells. At an elevated areal capacity of 2 mAh cm⁻² (Fig. 3b and Fig. S13b), the Na-NF@FIC cells maintain a prolonged cycling lifespan with minimal overpotential. Furthermore, upon increasing the current density to 1 mA cm⁻² (Fig. 3b and Fig. S13c), Na-NF@FIC achieves a cycle life of 200 h, whereas bare Na and Na-NF display rapid degradation, sustaining only 65 h and 30 h, respectively. These findings demonstrate that the Na-NF@FIC composite anode possesses enhanced structural stability and improved electrochemical reversibility. Additionally, the cycling performance of symmetric cells assembled with the Na-NF@FIC-noSDS&PEG and Na-NF-SDS&PEG electrodes was evaluated. As shown in Fig. S14, both electrodes exhibited gradually increasing electrochemical polarization over 100 cycles. This result suggests that the enhanced long-term cycling stability of the Na-NF@FIC electrode is not mainly due to the surfactants alone.

Fig. 3 Electrochemical properties of Na-NF@FIC and Na-NF symmetric cells: (a–c) voltage–time curves at different current densities; (d) rate capability from 0.5–8 mA cm⁻². (e) Coulombic efficiency of Cu foil, pure NF, and NF@FIC electrodes.

A comprehensive rate performance test was further investigated from 0.5 to 8 mA cm⁻² (Fig. 3d and S15). The bare Na symmetric cell exhibits the highest polarization at all tested rates and fails at 5 mA cm⁻² due to unstable sodium deposition and insufficient Na storage capability. In contrast, Na-NF and Na-NF@FIC symmetrical cells show negligible overpotential differences below 1 mA cm⁻². However, when the current density exceeds 2 mA cm⁻², the Na-NF||Na-NF cell displays significantly increased polarization compared to the Na-NF@FIC counterpart, underscoring the latter's superior rate performance. Additionally, the coulombic efficiency (CE) was measured in Na half-cells at 0.5 mA cm⁻¹ and 1 mAh cm⁻² (Fig. 3e). The conventional Cu foil current collector displays unstable cycling with continuous CE decay, while the 3D Ni foam slightly outperforms bare Na metal. After NVP modification, the NF@FIC substrate maintains significantly enhanced CE stability, attributed to the high sodium affinity and fast-ion conductor capability of NVP. These features endow the composite framework with increased interfacial stability and minimize parasitic reactions, ensuring highly reversible sodium deposition/dissolution. The loss of CE can be attributed to persistent side reactions. The large surface area of the Ni foam substrate amplifies these reactions, leading to significant sodium loss, especially under limited deposition capacity. Therefore, improving the CE by suppressing side reactions is a crucial objective for our subsequent work.

XPS analysis was employed to investigate the stability of the SEI on Na-NF@FIC and Na-NF electrodes after 20 cycles at 0.5 mA cm⁻² and 0.5 mAh cm⁻². Fig. S16a and e show the C 1s spectra; both samples exhibit distinct peaks corresponding to C–C (284.7 eV), C–O (286.1 eV), and C=O (289.0 eV) bonding configurations. The C–C peak predominantly originates from organic constituents within the SEI layer (or potentially the carbon coating of NVP), whereas the C=O peak is indicative of Na₂CO₃ formation.³⁹ In the Na-NF@FIC electrode, the C–C content is markedly elevated (C–C : C=O = 2 : 1), with the increased organic fraction enhancing the SEI flexibility, thereby facilitating accommodation of interfacial volume variations during sodium plating/stripping processes. In contrast, alkali carbonates contribute to SEI brittleness and structural instability.^40,41 By comparison, the Na-NF electrode exhibits a lower C–C : C=O ratio (1.7 : 1). Consequently, the diminished carbonate concentration on the NF@FIC substrate promotes the formation of a more robust SEI layer, thereby enhancing the electrode's cycling stability. The high-resolution F 1s spectra reveal attenuated surface signals for both electrodes (Fig. S16b and f), presumably attributable to the residual separator interference. Post-etching analysis demonstrates that the Na-NF@FIC electrode exhibits a substantially greater Na–F (683.9 eV) bonding contribution (82.6%), compared to merely 73% for the unmodified NF electrode, indicating a higher NaF content in the SEI composition of Na-NF@FIC.⁴² In the O 1s spectra (Fig. S16c and g), the C–O (532.0 eV) peak arises from organic components generated by electrolyte decomposition, while the Na–O (530.1 eV) bond represents the inorganic component Na₂O. Surface analysis reveals a hybrid organic–inorganic SEI architecture for both electrodes. Subsequent depth profiling via etching discloses a pronounced enrichment of the Na₂O inorganic phase, particularly in the Na-NF@FIC system where inorganic constituents become predominant. These observations collectively demonstrate that Na-NF@FIC develops a thermodynamically stable passivation layer with superior electrolyte corrosion resistance.⁴³ Furthermore, comparative analysis of Na 1s spectra (Fig. S16d and h) confirms the enhanced spectral weight of inorganic phases (NaF and Na₂O) within the SEI of Na-NF@FIC relative to the pristine substrate, providing compelling evidence for the formation of a structurally robust SEI.

The morphological evolution of 3D Na metal anodes was carefully characterized during repeated stripping/plating cycles at 0.5 mA cm⁻² and 0.5 mAh cm⁻². As presented in Fig. 4a and b, the Na-NF@FIC electrode maintains a smooth surface morphology after 50 cycles, demonstrating effective dendrite suppression. Notably, the interior of the 3D Ni foam framework was filled with Na metal, highlighting NVP's exceptional sodiophilicity for inducing homogeneous Na nucleation and deposition. Even after 100 cycles (Fig. 4c and d), the Na-NF@FIC anode retains its structural integrity without abnormal whisker formation, and the metallic Na still deposits inside the framework rather than on the surface. These observations confirm that the composite 3D architecture possesses long-term structural stability, preserving both its superior sodiophilicity and dendrite-inhibiting efficacy during prolonged cycling. In contrast, the Na-NF cell displays significantly poorer cycling properties, suffering a short circuit after only 39 cycles. SEM analysis (Fig. 4e) reveals that sodium plating occurs primarily on the NF surface rather than within the framework. The poor sodium affinity of unmodified NF results in limited deposition capacity, revealing incomplete Na filling with large surface porosity. Fig. 4f further demonstrates the formation of large protrusions due to non-uniform Na deposition/dissolution, which severely compromises the electrochemical performance and cycle life. For comparison, the bare Na anode (Fig. S17) displays extreme surface inhomogeneity after only 25 cycles under identical conditions, exhibiting disordered nucleation behavior and uncontrolled volume changes. These results collectively demonstrate the critical role of 3D host structures in mitigating mechanical strain and promoting uniform sodium deposition. As shown in Fig. S18, after a deposition of 10 mAh cm⁻², sodium metal predominantly accumulates on the surface of the bare Ni foam (NF), resulting in a composite anode with a thickness of approximately 316 μm. Following 20 cycles at 0.5 mA cm⁻² and 0.5 mAh cm⁻², the electrode thickness increased to 346 μm and exhibited partial structural collapse. This phenomenon indicates unstable sodium plating/stripping behavior with a tendency for sodium to aggregate on the surface of the 3D framework. In contrast, for the NVP-modified electrode under the same deposition capacity, sodium primarily fills the internal pores of the framework, leading to a relatively flat surface. After 20 cycles, its thickness increased from 136 μm to 158 μm. The structural integrity was well preserved, with no detectable dendrites on the surface, demonstrating the enhanced cycling stability afforded by the sodiophilic NVP modification.

Fig. 4 SEM images of symmetric cells under various stripping/plating cycles at 0.5 mA cm⁻² and 0.5 mAh cm⁻²: (a, b) 50 cycles and (c, d) 100 cycles for Na-NF@FIC; (e, f) 39 cycles (short circuit) for Na-NF. In situ optical observation of the plating process at 1 mA cm⁻²: (g) bare NF, (h) NF@FIC.

In situ optical microscopy was employed to directly observe sodium nucleation and growth behavior across different substrates within a Swagelok cell configuration. Fig. 4g illustrates the morphological evolution during Na plating on pristine NF at 1 mA cm⁻². Initially, the NF surface shows a metallic luster and smooth appearance. As the deposition capacity increased (Fig. S19a), sodium dendrites became increasingly pronounced on the surface of the unmodified Ni foam, indicating that sodium deposition primarily occurred on the exterior of the framework. In contrast, for the NVP-modified Ni foam, the growth of surface dendrites was significantly suppressed during the initial deposition stage. This suggests that sodium ions were predominantly deposited within the framework's interior (Fig. S19b). This phenomenon can be primarily attributed to the guiding effect of the NVP layer. At 0.5 mAh cm⁻² capacity, significant dendritic growth appears, with Na preferentially accumulating on the NF surface. As deposition progresses, these dendrites undergo substantial vertical elongation, developing severe dendritic structures exceeding the NF substrate thickness (0.5 mm) at 1 mAh cm⁻². When the deposition capacity reached 1 mAh cm⁻², numerous fractured sodium dendrites are observed on both the conductive substrate surface of the optical observation device and in the electrolyte solution, indicating the poor performance of the sodium anode.

In striking contrast, the NF@FIC composite demonstrates markedly different deposition behavior (Fig. 4h). The deposited sodium metal will grow inward towards the framework under the influence of the NVP ion channels, rather than undergoing vertical propagation. At a deposition capacity of 1 mAh cm⁻², sodium uniformly infiltrates nickel foam's porous network, which can effectively accommodate volumetric changes and achieve confined growth. The inward-growing deposition mode enabled by the sodiophilic 3D skeleton prevents vertical sodium propagation along the substrate surface. The in situ optical microscopy observation provides compelling morphological evidence that the NVP-modified host effectively regulates Na nucleation behavior, resulting in region-induced deposition. The synergistic combination of sodiophilic sites and the porous architecture enables stable, dendrite-free Na plating/dissolution cycles. When the deposition capacity reached 5 and 8 mAh cm⁻², the 3D framework attained near-complete sodium metal occupancy within its interior (Fig. S20c and d). The electrode surface remained relatively flat, with some glass fibers adhering to it. Cross-sectional SEM imaging of the Na-NF@FIC electrode confirmed that the deposited sodium primarily filled the internal pores, rather than forming a thick layer on the top surface.

Electrochemical kinetic analysis of symmetric cells was systematically performed (Fig. 5). The Tafel plots in Fig. 5a show that Na-NF@FIC demonstrates the highest exchange current density, indicating superior mass transport properties and fast Na⁺ deposition/dissolution kinetics. While the Na-NF configuration exhibits lower exchange current density compared to Na-NF@FIC, it still outperforms unmodified Na electrodes, demonstrating the intrinsic advantages of the 3D framework. To further explore interfacial stability evolution during cycling, electrochemical impendence spectroscopy measurements at various cycle intervals (Fig. 5b–d, with the corresponding voltage–time profiles in Fig. S21) were performed. The Na-NF@FIC||Na-NF@FIC cell maintains small and stable impedance throughout cycling compared to the Na-NF counterpart, reflecting both faster reaction kinetics and superior interfacial stability. Notably, the rapid impedance stabilization suggests efficient electrode activation and the establishment of a robust solid-electrolyte interphase. In contrast, the bare Na cell exhibits characteristically high initial impedance (Fig. 5d), which abruptly decreases after 16 cycles (Fig. S21c) due to dendrite-induced short-circuiting. The Na-NF||Na-NF system shows intermediate performance, where the impedance fluctuations indicate unstable interfacial kinetics and progressive degradation of the electrode–electrolyte interface during cycling (Fig. 5e).

Fig. 5 (a) Tafel curves of Na-NF@FIC, Na-NF and bare Na symmetric cells. (b–d) Impedance spectra of Na-NF@FIC, Na-NF and bare Na symmetric cells under various cycles at 0.5 mA cm⁻² (0.5 mAh cm⁻²). (e) Comparison of R_ct for Na-NF@FIC, Na-NF and bare Na. (f) GITT curves of Na-NF@FIC, Na-NF and bare Na cells, with a zoomed-in region shown in (g).

GITT was utilized to analyze the Na⁺ transport kinetics. As illustrated in Fig. 5f and g, the substantial and fluctuating overpotential in the Na-NF symmetric cell shows sluggish kinetic behavior and interfacial instability. The observed voltage spikes at the beginning of each cycle are associated with the nucleation energy barrier. The Na-NF system exhibits a higher voltage spike than the Na-NF@FIC system, which is consistent with the nucleation overpotential measurements in Fig. 2b. Compared with NF@FIC, pure Na exhibits more significant polarization differences. The prominent voltage spikes at the start and end of each charge/discharge cycle correspond to higher nucleation and dissolution barriers.^44,45 In contrast, the Na-NF@FIC||Na-NF@FIC cell has a relatively flat voltage plateau, suggesting lower energy barriers for Na deposition/dissolution processes. This highlights the improved electrochemical performance of the NF@FIC composite in facilitating sodium ion transport and stabilizing the electrode–electrolyte interface.

To assess the practical applicability of the Na-NF@FIC anode, full cells were assembled by coupling NVP cathodes with pure Na, Na-NF and Na-NF@FIC anodes (Fig. 6a). As shown in Fig. 6b, cyclic voltammetry (CV) profiles reveal typical NVP redox peaks at approximately 3.5 V (oxidation) and 3.3 V (reduction). The differences in peak position and intensity demonstrate that the Na-NF||NVP cell manifests significantly higher polarization and diminished peak current density relative to the Na-NF@FIC||NVP cell at the scan rate of 0.1 mV s⁻¹. Fig. 6c reveals that the full cell incorporating the Na-NF@FIC anode exhibits significantly superior rate capability. During the first few charge/discharge cycles (0.2–0.5C), the specific capacities of both cells exhibit slight divergence (∼99.8 mAh g⁻¹). However, with increasing current rates, the Na-NF||NVP cell undergoes a precipitous decline in discharge specific capacity, culminating in complete capacity loss at 50C. In contrast, the Na-NF@FIC||NVP cell shows superior rate stability. The specific capacity attenuation of Na-NF@FIC from 0.2 to 12C is within 10 mAh g⁻¹ (90.5 mAh g⁻¹ at 12C), and it even retains 31.0 mAh g⁻¹ at 50C, indicating the excellent electrochemical reversibility.

Fig. 6 (a) Schematic diagram of the Na-NF@FIC||NVP full cell. (b) CV comparison of Na-NF and Na-NF@FIC full cells at 0.1 mV s⁻¹. (c) Rate capability of Na-NF||NVP and Na-NF@FIC||NVP full cells. (d) Voltage polarization at different rates. (e) Cycling stability after 400 cycles at 5C.

The polarization overpotentials of both cells at different C-rates are compared in Fig. 6d and the corresponding discharge/charge curves are provided in Fig. S22. The Na-NF@FIC||NVP cell exhibits a limited polarization of 21.4, 46.8, 166.7, 224.9 and 314.8 mV at 0.2, 1, 5, 7 and 10C, respectively. However, the pristine sample shows severe polarization, reaching an excessive potential difference of 1119.1 mV at 10C, indicating irreversible electrochemical behavior. To further demonstrate the superiority of the composite anode Na-NF@FIC, a full cell was assembled using commercially available NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) layered oxide as the cathode. As shown in Fig. S23, the Na-NF@FIC||NFM cell exhibits improved rate capability and lower polarization in the charge/discharge curves compared to the Na-NF||NFM cell, indicating a more stable Na⁺ extraction/insertion ability of the composite anode. Fig. 6e compares the cycling stability of both cells at 5C. The Na-NF@FIC||NVP cell shows outstanding long-term cyclability, retaining 94.6% of its capacity with a high average CE of ∼99% over 400 cycles. In contrast, the unmodified Na-NF||NVP cell suffers from rapid degradation, retaining only 57.5% capacity retention under identical conditions. The evolution of the charge–discharge curves for both cells during cycling at 5C is compared in Fig. S24. For the Na-NF||NVP cell, the characteristic voltage plateau of the NVP cathode gradually disappears with cycling, accompanied by a rapid decay in specific capacity. After 300 cycles, the median voltage polarization difference reaches 1019.3 mV, where this difference is defined as the voltage gap between the midpoints (50% state of charge/discharge) of the charge and discharge plateaus. In contrast, the Na-NF@FIC||NVP cell exhibits a smaller polarization difference of 416.3 mV after 300 cycles at 5C, confirming its improved long-term cycling stability. Upon reaching 400 cycles, the Na-NF@FIC||NVP cell demonstrated an overpotential of 480.7 mV, whereas the unmodified counterpart exhibited a significantly higher overpotential of 1097.1 mV.

The Na-NF@FIC anode also demonstrates superior electrochemical performance in full-cell configurations in comparison with pure Na anodes. As demonstrated in Fig. S25, the Na||NVP control cell retains a discharge capacity of 35.2 mAh g⁻¹ at 20C while preserving 86.8% of its initial 0.2C capacity. Notably, the Na-NF||NVP cell exhibits inferior capacity retention compared to the Na||NVP cell, primarily due to the inherently poor sodiophilicity of NF, which results in non-uniform Na deposition. More critically, pronounced dendrite formation and heterogeneous Na plating promote uneven Na distribution, exacerbating both Na loss and the accumulation of electrochemically inactive dead Na. These cumulative effects directly correlate with the observed performance degradation, manifested through enhanced polarization and capacity fading. In contrast, the exceptional electrochemical performance of the Na-NF@FIC||NVP full-cell unambiguously validates the advantageous role of NVP modification in optimizing the 3D current collector architecture. Additionally, the full-cell performance in our work was compared with recently published studies (Table S1). Under similar cycling conditions, the NVP-modified NF@FIC||NVP cell demonstrated competitive capacity retention at 5C after 400 cycles, indicating the effectiveness of the sodiophilic dual-conductivity strategy in improving the long-term structural stability of the Na metal anode.

Conclusions

A 3D sodiophilic current collector modified with fast ionic conductor NVP has been successfully synthesized via a hydrothermal method. The sodiophilic fast-ion conductor network not only regulates the inward Na⁺ flux for spatially uniform Na deposition, but also facilitates low-energy-barrier Na nucleation, thermodynamically suppressing dendrite formation. Moreover, the interconnected ion-conduction network in the Na-NF@FIC composite anode facilitates rapid charge transfer, thereby improving the reversibility of Na⁺ plating/stripping processes. Additionally, the 3D conductive nickel foam framework helps reduce the localized current density, promoting spatially confined Na growth while alleviating volume fluctuations during Na ion (de)intercalation processes. Consequently, the Na-NF@FIC anode demonstrates remarkable electrochemical stability, showing progressively reduced overpotentials during prolonged Na plating/stripping cycles. It maintains stable operation for 300 hours at 0.5 mA cm⁻² and 0.5 mAh cm⁻². When configured in a full-cell with the NVP cathode, the Na-NF@FIC||NVP cell delivers exceptional rate capability and retains 94.6% of its initial capacity after 400 cycles at 5C. By simultaneously addressing nucleation, ion transport, and volume change challenges, this 3D current collector design provides a comprehensive solution for stable sodium metal anodes, paving the way for developing high-energy-density sodium-based batteries.

Conflicts of interest

The authors declare no conflict of interest.

Data availability

Data will be made available from the authors upon reasonable request.

Supplementary information (SI) is available. See DOI: https://doi.org/10.1039/d5qi01606a.

Acknowledgements

The authors would like to acknowledge the financial support from the Zhejiang Provincial Natural Science Foundation of China (No. LQ23B030005) and the National Natural Science Foundation of China (No. 22208220).

References

1. P. Simon and Y. Gogotsi, Perspectives for electrochemical capacitors and related devices, Nat. Mater., 2020, 19, 1151–1163.
2. Q. Wang, X. He, D. Zhang, Z. Li, H. Sun, Q. Sun, B. Wang and L.-Z. Fan, A composite electrolyte based on aluminum oxide filler/polyester polymer via in situ thermal polymerization for long-cycle sodium metal batteries, Inorg. Chem. Front., 2024, 11, 2300–2311.
3. S. Osman, S. Hu, Y. Wei, J. Liu, J. Xiao, W. Yao, C. Han, X. Guo, J. Liu and Y. Tang, Deep layer pillaring reinforced electronic states and structural defects toward high–performance sodium ion battery, Adv. Energy Mater., 2024, 15, 2404685.
4. A.-M. Li, P. Y. Zavalij, F. Omenya, X. Li and C. Wang, Salt-in-presalt electrolyte solutions for high-potential non-aqueous sodium metal batteries, Nat. Nanotechnol., 2025, 20, 388–396.
5. F.-Y. Tao, D. Xie, D.-H. Wang, W.-Y. Diao, C. Liu, X.-L. Wu, W.-L. Li and J.-P. Zhang, In situ formed self-embedded ion/electron conductive skeletons enabling highly stable sodium metal anodes, Inorg. Chem. Front., 2024, 11, 3211–3220.
6. B. Chen, Y. Zhao, B. Yuan, Y. Zhu and S. Chong, Antimony telluride as bifunctional host material for dendrite-free sodium metal batteries, Nano Lett., 2025, 25, 4869–4877.
7. B. Sayahpour, W. Li, S. Bai, B. Lu, B. Han, Y.-T. Chen, G. Deysher, S. Parab, P. Ridley, G. Raghavendran, L. H. B. Nguyen, M. Zhang and Y. S. Meng, Quantitative analysis of sodium metal deposition and interphase in Na metal batteries, Energy Environ. Sci., 2024, 17, 1216–1228.
8. A. Singla, K. G. Naik, B. S. Vishnugopi and P. P. Mukherjee, Chemo–mechanics interplay dictates interface instability and asymmetry in plating and stripping of sodium metal electrodes, Adv. Funct. Mater., 2025, 35, 2418033.
9. M. Li, C. Li, G. Lu, R. Wang, Z. Luo, Z. Li, R. Deng, W. Zheng, W. Wang, Y. Fang, B. Qu and C. Xu, Manipulation of the anode interphase by multicomponent composite sodium for fast–charging and low–temperature sodium metal batteries, Adv. Funct. Mater., 2025, 35, 2422892.
10. Z. Huang, Z. Zhang, N. Shen, A. Li, H. Wang, C. Fang, T. Xu, D. Kong, X. Li, Y. Shi, X. Liu, L. Zeng, H. Y. Yang, Y. Wang and C. Shan, Diamane facilitated the stability of sodium metal anodes, Nano Lett., 2025, 25, 9589–9596.
11. Z. Lu, J. Xiao, H. Xie, W. Song, M. Fujishige, K. Takeuchi, M. Endo, Z. Li, J. Niu and F. Wang, From waste to wealth: Cd-adsorbed rapeseed meal towards CdS-decorated nanocarbons for high-performance sodium metal batteries, Energy Storage Mater., 2025, 80, 104393.
12. Y. Wu, J. Zhu, J. Ni and L. Li, Liquid metal–modified 3D Cu foam for dendrite–free sodium plating, Small, 2024, 20, 2405357.
13. X. Zheng, Z. Zhang, Z. Li, C. Shi, Y. Yamauchi and J. Tang, In situ formation of inorganic-rich solid electrolyte interphase by using antimony and fluorine-modified Cu foam for dendrite-free sodium metal anodes, Nano Energy, 2025, 138, 110858.
14. Y. Tian, H. You, Y. Lu, T. Sun, S. Guo and Y. Liu, Nitrogen-doped carbon confined V₂O₃ with 3D porous network structure for high performance Na⁺ and K⁺ storage, J. Energy Storage, 2024, 90, 111918.
15. P. Liu, S. Zhao, S. Gao, L. Yang, K. Fang, Y. Zhu, H. Niu, X. Jia and J. Zhou, Utilizing MOFs melt-foaming to design functionalized carbon foams for 100% deep-discharge and ultrahigh capacity sodium metal anodes, ACS Nano, 2024, 19, 1577–1587.
16. Q. Zhang, Y. Lu, M. Zhou, J. Liang, Z. Tao and J. Chen, Achieving a stable Na metal anode with a 3D carbon fibre scaffold, Inorg. Chem. Front., 2018, 5, 864–869.
17. F. Chen, C. Yu, J. Cui, D. Yu, P. Song, Y. Wang, Y. Qin, J. Yan and Y. Wu, A core-shell structured metal-organic frameworks-derived porous carbon nanowires as a superior anode for alkaline metal-ion batteries, Appl. Surf. Sci., 2021, 541, 148473.
18. N. Mubarak, M. Ihsan-Ul-Haq, H. Huang, J. Cui, S. Yao, A. Susca, J. Wu, M. Wang, X. Zhang, B. Huang and J.-K. Kim, Metal–organic framework-induced mesoporous carbon nanofibers as an ultrastable Na metal anode host, J. Mater. Chem. A, 2020, 8, 10269–10282.
19. Y. Wang, C. Ye, J. Wang, F. Chen, J. Qian, C. Yang, Y. Song, L. Bi, Q. Xie, L. He, J. Yu, X. Wei, H. Song, J. Liao, S. Wang and R. Chen, Promoting homogeneous lithium deposition by facet-specific absorption of CoIn₃ for dendrite-free lithium metal anodes, Nano Energy, 2024, 119, 109093.
20. C. Chu, R. Li, F. Cai, Z. Bai, Y. Wang, X. Xu, N. Wang, J. Yang and S. Dou, Recent advanced skeletons in sodium metal anodes, Energy Environ. Sci., 2021, 14, 4318–4340.
21. Q. Chen, B. Liu, L. Zhang, Q. Xie, Y. Zhang, J. Lin, B. Qu, L. Wang, B. Sa and D.-L. Peng, Sodiophilic Zn/SnO₂ porous scaffold to stabilize sodium deposition for sodium metal batteries, Chem. Eng. J., 2021, 404, 126469.
22. Z. Wang, J. Ni and L. Li, Gradient designs for efficient sodium batteries, ACS Energy Lett., 2022, 7, 4106–4117.
23. W. Cao, M. Liu, W. Song, Z. Li, B. Li, P. Wang, A. Fisher, J. Niu and F. Wang, Regulating sodium deposition behavior by a triple-gradient framework for high-performance sodium metal batteries, Adv. Sci., 2024, 11, e2402321.
24. C. Shi, X. Zheng, Z. Li, Q. Fang and J. Tang, Solid electrolyte interphase engineering by designing cobalt–doped Ni₃S₂–NF anode for sodium metal anode, ChemCatChem, 2025, 17, e202402160.
25. Y. Xu, E. Matios, J. Luo, T. Li, X. Lu, S. Jiang, Q. Yue, W. Li and Y. Kang, SnO₂ quantum dots enabled site-directed sodium deposition for stable sodium metal batteries, Nano Lett., 2021, 21, 816–822.
26. Y. Zhu, H. Xu, J. Ma, P. Chen and Y. Chen, The recent advances of NASICON-Na₃V₂(PO₄)₃ cathode materials for sodium-ion batteries, J. Solid State Chem., 2023, 317, 123669.
27. C. Wang, D. Du, M. Song, Y. Wang and F. Li, A high–power Na₃V₂(PO₄)₃–Bi sodium–ion full battery in a wide temperature range, Adv. Energy Mater., 2019, 9, 1900022.
28. R. Ling, S. Cai, D. Xie, X. Li, M. Wang, Y. Lin, S. Jiang, K. Shen, K. Xiong and X. Sun, Three-dimensional hierarchical porous Na₃V₂(PO₄)₃/C structure with high rate capability and cycling stability for sodium-ion batteries, Chem. Eng. J., 2018, 353, 264–272.
29. J. Li, H. Su, Z. Jiang, Y. Zhong, X. Wang, C. Gu, X. Xia and J. Tu, Domain-limited laminar lithium deposition behavior mediated by the design of hybrid anode for sulfide-based all-solid-state batteries, Acta Mater., 2023, 244, 118592.
30. A. Bagmut, Layer, island and dendrite crystallizations ofamorphous films as analogs of Frank-van derMerwe, Volmer-Weber and Stranski-Krastanovgrowth modes, Funct. Mater., 2019, 26, 6.
31. L. Guo, G. Oskam, A. Radisic, P. M. Hoffmann and P. C. Searson, Island growth in electrodeposition, J. Phys. D: Appl. Phys., 2011, 44, 443001.
32. J. Guo, Y. Li, K. Xu, Z. Huang, W. Hu, Y. Tan, C. Sun, J. Yang and H. Geng, Manipulating interfacial renovation via in situ formed metal fluoride heterogeneous protective layer toward exceptional durable sodium metal anodes, Adv. Funct. Mater., 2024, 34, 2411760.
33. P. Liu, L. Miao, Z. Sun, X. Chen, Y. Si, Q. Wang and L. Jiao, Inorganic-organic hybrid multifunctional solid electrolyte interphase layers for dendrite-free sodium metal anodes, Angew. Chem., Int. Ed., 2023, 62, e202312413.
34. F. Liu, L. Wang, F. Ling, X. Zhou, Y. Jiang, Y. Yao, H. Yang, Y. Shao, X. Wu, X. Rui, C. He and Y. Yu, Homogeneous metallic deposition regulated by porous framework and selenization interphase toward stable sodium/potassium anodes, Adv. Funct. Mater., 2022, 32, 2210166.
35. P. Liu, H. Yi, S. Zheng, Z. Li, K. Zhu, Z. Sun, T. Jin and L. Jiao, Regulating deposition behavior of sodium ions for dendrite–free sodium–metal anode, Adv. Energy Mater., 2021, 11, 2101976.
36. C. Bao, B. Wang, Y. Xie, R. Song, Y. Jiang, Y. Ning, F. Wang, T. Ruan, D. Wang and Y. Zhou, Sodiophilic decoration of a three-dimensional conductive scaffold toward a stable Na metal anode, ACS Sustainable Chem. Eng., 2020, 8, 5452–5463.
37. X. Lu, H. Zhao, Y. Qin, E. Matios, J. Luo, R. Chen, H. Nan, B. Wen, Y. Zhang, Y. Li, Q. He, X. Deng, J. Lin, K. Zhang, H. Wang, K. Xi, Y. Su, X. Hu, S. Ding and W. Li, Building fast ion-conducting pathways on 3D metallic scaffolds for high-performance sodium metal anodes, ACS Nano, 2023, 17, 10665–10676.
38. Z. Li, H. Qin, W. Tian, L. Miao, K. Cao, Y. Si, H. Li, Q. Wang and L. Jiao, 3D Sb–based composite framework with gradient sodiophilicity for ultrastable sodium metal anodes, Adv. Funct. Mater., 2023, 34, 2301554.
39. J. Zhang, S. Wang, W. Wang and B. Li, Stabilizing sodium metal anode through facile construction of organic-metal interface, J. Energy Chem., 2022, 66, 133–139.
40. G. Zheng, Y. Xiang, S. Chen, S. Ganapathy, T. W. Verhallen, M. Liu, G. Zhong, J. Zhu, X. Han, W. Wang, W. Zhao, M. Wagemaker and Y. Yang, Additives synergy for stable interface formation on rechargeable lithium metal anodes, Energy Storage Mater., 2020, 29, 377–385.
41. B. Han, Z. Zhang, Y. Zou, K. Xu, G. Xu, H. Wang, H. Meng, Y. Deng, J. Li and M. Gu, Poor stability of Li₂CO₃ in the solid electrolyte interphase of a lithium-metal anode revealed by cryo-electron microscopy, Adv. Mater., 2021, 33, e2100404.
42. Z. Hu, L. Liu, X. Wang, H. Lu, Q. Zheng, Y. Gao, J. Wang, Y. Qi, C. Han and W. Li, In situ integration of rapid ion-diffusion interlayers on Cu current collectors toward ultrafast anode-free sodium metal batteries, ACS Nano, 2025, 19, 23193–23208.
43. X. Zheng, W. Yang, Z. Wang, L. Huang, S. Geng, J. Wen, W. Luo and Y. Huang, Embedding a percolated dual-conductive skeleton with high sodiophilicity toward stable sodium metal anodes, Nano Energy, 2020, 69, 104387.
44. S. Tang, Z. Qiu, X.-Y. Wang, Y. Gu, X.-G. Zhang, W.-W. Wang, J.-W. Yan, M.-S. Zheng, Q.-F. Dong and B.-W. Mao, A room-temperature sodium metal anode enabled by a sodiophilic layer, Nano Energy, 2018, 48, 101–106.
45. K.-H. Chen, K. N. Wood, E. Kazyak, W. S. LePage, A. L. Davis, A. J. Sanchez and N. P. Dasgupta, Dead lithium: mass transport effects on voltage, capacity, and failure of lithium metal anodes, J. Mater. Chem. A, 2017, 5, 11671–11681.

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