Li-S batteries have emerged as a highly competitive electrochemical energy storage technology, mainly owing to their remarkable energy density (2,600 Wh kg^-1) and the low cost of their raw materials^[1-3]. However, the widespread commercialization of Li-S batteries is still hindered by several intrinsic drawbacks. The sulfur itself is electronically insulated, and the reaction between sulfur and lithium sulfide (Li₂S) is sluggish. Particularly, the intermediate product lithium polysulfides (LiPSs) dissolve and diffuse in the ether electrolyte, and sulfur electrode suffers from severe shuttle effect, which leads to suboptimal utilization of active materials, poor cycle stability and even battery failure of the Li-S batteries^[4-7]. Current research endeavors are aiming to mitigate the aforementioned concerns. Strategies such as physical confinement^[8-10] and chemical absorption^[11,12] of sulfur were used to suppress the shuttle effect. By introducing heterogeneous catalyst into the sulfur cathode, the redox reaction kinetics are accelerated^[13,14]. Nevertheless, the unavoidable dissolution of long-chain LiPSs in ether-based electrolytes remains a critical issue.

As a sulfur-based cathode material, sulfurized polyacrylonitrile (SPAN) represents a promising candidate for Li-S batteries, which can be readily fabricated via heat treatment of polyacrylonitrile (PAN) under sulfur vapor^[15,16]. Different from conventional sulfur-carbon composites prepared by physical blending, sulfur species in SPAN are covalently bonded to the conductive framework generated from PAN pyrolysis^[17,18]. Although the precise molecular structure of SPAN has not been fully elucidated, it is widely accepted that sulfur is anchored onto the PAN-derived carbon support through covalent linkages. Accordingly, only short-chain LiPSs (Li₂S_n, n ≤ 4) are involved in the electrochemical redox reactions upon cycling^[19,20]. Thus, the notorious dissolution of LiPSs into electrolyte and shuttle effect of the sulfur cathode can be avoided. However, the slow kinetics of the solid-solid conversion reaction of SPAN would deteriorate the utilization of the sulfur and result in capacity fading of SPAN while cycling. In addition, the rate performance and cycle performance of the SPAN electrode under high rates are impacted as well^[21]. To address the issue, electrocatalysts were explored and integrated into SPAN, which effectively anchors polysulfides and significantly improves the redox kinetics of SPAN electrode^[22-24].

To optimize the cathode performance of Li-SPAN batteries, various catalytic materials have been developed to enhance the redox kinetics, including transition metal carbides, transition metal oxides, and transition metal sulfides. Among these candidates, transition metal sulfides presents combined merits, such as relatively higher electronic conductivity and good polar affinity for sulfur species, thus enabling dual functions of anchoring short-chain Li₂S_n and catalyzing their solid-solid conversion reactions during the operation of Li-S batteries^[25-28]. For instance, Li et al.^[29] incorporated cobalt sulfide (CoS₂) into SPAN, which enhanced its reactive activity and cycling stability, allowing the material to sustain over 500 cycles at 1 C. Liu et al.^[30] synthesized NiS₂-SPAN powders using a simple co-heating method, which exhibited superior rate capabilities with a NiS₂ content of less than 3 wt%. Although transition metal sulfides are the most widely investigated category of metal sulfides for SPAN cathode modification, binary transition metal sulfides exhibit more abundant electrochemical active sites and more reactive polar surfaces compared with single transition metal sulfides^[31,32]. This enables stable, rapid charge transport and sustained catalytic effects through multicomponent synergy and regulation of electronic band structures, which would boost the reaction kinetics^[33,34]. Furthermore, to maximize the adsorption sites and catalytic efficiency for LiPSs, quantum dots (QDs), characterized by ultra-small size and superior dispensability, are particularly effective^[35]. These QDs would significantly enhance the host-guest interactions, lower the reaction energy barrier, and provide exceptional catalytic effects on LiPSs^[36,37]. Yet, the application of binary-TMS (transition metal sulfides)-based QDs to modify SPAN for boosting the electrochemical properties of Li-SPAN batteries remains rarely reported.

In this study, we developed a novel FeNiS₂ QDs@SPAN composite by blending PAN/NiFe₂O₄ QDs nanofibers incorporated with sulfur powder, followed by a heat treatment. This process initiates polymerization and dehydrogenation reactions between PAN and sulfur, leading to the formation of pyridine ring structures. In the meantime, the NiFe₂O₄ QDs is sulfurized as FeNiS₂. The uniform dispersion of FeNiS₂ QDs throughout the composite increases the number of active sites, which enhances the charge transfer and accelerates the conversion of short-chain polysulfides. These improvements are crucial for optimizing the redox reaction kinetics. Meanwhile, the one-dimensional (1D) nanofibers maintain the structural integrity of the composite and provide short-distance diffusion pathways for ions. Benefiting from these synergistic advantages, the FeNiS₂ QDs@SPAN nanofibers exhibit excellent cycling stability and rate performance. Notably, the FeNiS₂ QDs@SPAN electrode achieves superior electrochemical performance at high rates, which is rarely reported for SPAN-based electrodes. It also maintains outstanding performance metrics across a wide temperature range and under lean electrolyte conditions, demonstrating great potential for practical application.

Figure 1A and B illustrates the detailed procedure for synthesizing FeNiS₂ QDs@SPAN nanofibers. Initially, NiFe₂O₄ was synthesized using a hydrothermal method, and its aqueous dispersion exhibited bright blue luminescence under 365 nm Ultraviolet (UV) irradiation, confirming its quantum dot nature. A mixture of PAN and NiFe₂O₄ QDs was dispersed in DMF and stirred overnight to ensure solution homogeneity. This homogeneous solution was then loaded into a syringe for electrospinning, yielding NiFe₂O₄ QDs/PAN nanofiber precursors. Subsequently, these nanofibers were combined with sublimed sulfur in a high-pressure reaction vessel and subjected to heat treatment at 450 °C under an argon atmosphere. During this process, elemental sulfur (S₈) decomposed into smaller sulfur chains (-S_x-, where x < 8), facilitating the dehydrogenation and cyclization of PAN. Finally, a further heating step at 200 °C in a quartz tube furnace under argon flow was employed to remove any adsorbed excess sulfur, resulting in the formation of FeNiS₂ QDs@SPAN which exhibited excellent kinetic performance as a cathode [Figure 1C].

SEM images of NiFe₂O₄ QDs@PAN and FeNiS₂ QDs@SPAN are depicted in Supplementary Figure 1 and Figure 2A, respectively. The NiFe₂O₄ QDs@PAN sample displays a nanofiber mesh structure, characterized by long, uniformly interconnected fibers possessing an average diameter of roughly 165 nm. For FeNiS₂ QDs@SPAN, the integrity of the nanofiber network remains intact throughout the vulcanization process, with no visible sulfur particles adhering to the fiber surfaces. In addition, the FeNiS₂ QDs@SPAN sample exhibits an increased fiber diameter of approximately 320 nm, and the nanofiber surface becomes rough, attributed to the infiltration of saturated sulfur species. A similar phenomenon can be observed in both PAN and SPAN, as shown in Supplementary Figure 2.

The High-Resolution Transmission Electron Microscopy (HR-TEM) images reveal the FeNiS₂ QDs@SPAN contains both crystalline and high-contrast disordered regions [Figure 2B and C]. A lattice spacing of 0.26 nm is clearly observed [Figure 2D], combined Fast Fourier Transform (FFT) analysis corroborates that the interplanar spacings that precisely match the (101) planes of the cubic phase FeNiS₂. Furthermore, EDS mapping in the TEM confirm the uniform distribution of Ni, Fe, and S within the nanofibers [Figure 2E-H], indicating the homogeneous dispersion of FeNiS₂ QDs within the SPAN matrix without significant aggregation. And the FeNiS₂ content is 2.6 wt% according to the EDS analysis. The elemental composition of the FeNiS₂ QDs@SPAN and SPAN was quantitatively analyzed via ElementalAanalysis (EA), with the detailed results presented in Supplementary Table 1. The EA results indicate a sulfur content of 42% in SPAN and 46% in FeNiS₂ QDs@SPAN, demonstrating nearly identical levels of sulfur in both materials. The introduction of a trace amount of FeNiS₂ QDs did not impede the crosslinking process of PAN nanofibers with sulfur, thereby retaining a high sulfur content.

XRD measurements are performed to characterize the phase composition and crystalline properties of the resultant materials. The XRD patterns for various samples, including NiFe₂O₄ QDs, FeNiS₂ QDs, SPAN, and FeNiS₂ QDs@SPAN, are illustrated in Figure 2I and Supplementary Figure 3. The XRD spectra for NiFe₂O₄ QDs display characteristic peaks at 30.2°, 35.6°, 37.3°, 43.3°, 53.8°, 57.35°, and 62.92°, corresponding to the (220), (311), (222), (400), (442), (511), and (440) planes respectively, this aligns with the spinel structure of NiFe₂O₄ (PDF #054-0964)^[42]. The XRD patterns for both FeNiS₂ QDs and FeNiS₂ QDs@SPAN closely match the standard phase of FeNiS₂ (PDF card No. 75-0606), with identifiable peaks at 30.25°, 34.4°, 44.8°, 53.8°, 65.4°, and 72.5°, corresponding to the (100), (101), (102), (110), (201), and (202)planes of FeNiS₂^[43]. For the FeNiS₂ QDs@SPAN composites, broad diffraction peaks observed between 20° to 30° predominantly result from the overlap of the characteristic graphene (002) peak with the amorphous peak of SPAN. The above characterization results collectively confirm that the FeNiS₂ QDs@SPAN composite has been successfully synthesized.

The Fourier Transform Infrared Spectroscopy (FT-IR) spectroscopic analysis of the as-prepared samples is presented in Figure 2J. Two distinct absorption peaks appearing at 503 and 920 cm^-1 correspond to the stretching vibrations of disulfide (S-S) linkages, while the absorption signal at 658 cm^-1 is derived from the stretching vibration of carbon-sulfur (C-S) bonds. Additionally, the characteristic peaks at 1,480 and 1,349 cm^-1 belong to the typical vibrational modes of carbon-carbon double bonds (C=C) and single bonds (C-C), in sequence. A peak at 1,227 cm^-1 is attributed to carbon-nitrogen (C=N) bond vibrations, indicating specific organic features. The 797 cm^-1 peak suggests cyclic compounds in the material^[44]. The FT-IR spectra of FeNiS₂ QDs@SPAN and SPAN are almost identical, indicating that the incorporation of FeNiS₂ QDs does not significantly alter the molecular structure of SPAN. The Raman spectroscopic analysis of FeNiS₂ QDs@SPAN and SPAN composites is illustrated in Figure 2K. The FeNiS₂ QDs@SPAN sample exhibits two dominant characteristic peaks at 1,340 and 1,558 cm^-1, corresponding to the D- and G-bands of carbon, respectively. In addition, a distinct absorption peak at 470 cm^-1 is observed, which is assigned to the stretching mode of C-S bonds, verifying that sulfur has been chemically grafted onto the carbon matrix via covalent linkages during the thermal treatment process. The characteristic peak at 920 cm^-1 is attributed to the stretching vibration of six-membered ring structures^[45]. With I_G/I_D values below 1 for both composites, FeNiS₂ QDs@SPAN possesses a graphite-like stacked structure identical to that of pristine SPAN. These results confirm that PAN undergoes dehydrocyclization to form a six-membered aromatic framework with π-π stacking interactions, while sulfur species are anchored to the carbonaceous conductive matrix in the form of short-chain sulfur moieties. In summary, the incorporation of FeNiS₂ QDs exerts no discernible influence on the crosslinking reaction of PAN with sulfur.

To assess the impact of FeNiS₂ QDs on Li-S battery electrochemistry, corresponding cells were assembled with a metallic lithium anode and FeNiS₂ QDs@SPAN/SPAN cathodes for performance investigation. Rate capability is an important parameter for practical rechargeable battery systems. As illustrated in Figure 3A, the rate performance of two cathodes was evaluated by conducting charge/discharge cycles with varying rates from 0.5 C to 5 C. Both specific capacities and current rates are normalized with respect to the sulfur mass. The FeNiS₂ QDs@SPAN cathode delivers specific discharge capacities of 1,300, 1,180, 1,050, 1,005, and 880 mAh g^-1 at 0.5, 1, 2, 3 and 4 C, respectively (1 C = 1,675 mAh g^-1). The FeNiS₂ QDs@SPAN cathode demonstrates a higher discharge capacity compared to the battery with SPAN cathode at all current densities. Even when cycled at an ultra-large current density of 5 C during rate testing, the FeNiS₂ QDs@SPAN cathode retains a specific discharge capacity as high as 761.2 mAh g^-1, which is remarkably superior to that of the pristine SPAN counterpart (438 mAh g^-1). Upon switching the current density back to 0.5 C, the FeNiS₂ QDs@SPAN cathode recovers a high reversible capacity of 1,209 mAh g^-1, verifying its outstanding reversibility and rate stability. Notably, the pure FeNiS₂ QDs electrode shows negligible capacity under identical experimental conditions, as illustrated in Supplementary Figure 4A and B. Furthermore, CV analysis reveals that the FeNiS₂ QDs electrode demonstrates very low peak currents, indicating that the quantum dots themselves contribute little to the electrochemical capacity.

The charge-discharge profiles of the FeNiS₂ QDs@SPAN cathode at various current densities are presented in Figure 3B. Apparently, even under an ultra-high rate of 5 C, all discharge curves show a stable and flat voltage platform. In contrast, it is clear that the SPAN cathode experiences severe capacity degradation and greater polarization as the current density increases [Supplementary Figure 5]. The potential difference (discharge mid-voltage minus charge mid-voltage equals ΔE) between the discharge and charge curves represents the degree of polarization. As shown in Figure 3c, compared to SPAN (ΔE₂ = 312 mV), the FeNiS₂ QDs@SPAN (ΔE₁ = 276 mV) cathode shows a smaller voltage hysteresis and a higher reversible capacity. This mainly benefits from the catalytic activity of FeNiS₂ QDs for the electrochemical redox reactions, which facilitates the kinetic properties.

To evaluate the long-term cycling performance of Li-S batteries under high current densities, both cathodes were cycled at a fixed current rate of 5 C [Figure 3D]. SPAN experiences a structural rearrangement during the first discharge process^[46], therefore the SPAN and FeNiS₂ QDs@SPAN electrodes were activated at 0.1 C for 2 cycles to complete the structural reorganization. After activating the FeNiS₂ QDs@SPAN electrode, it exhibits a discharge specific capacity of 720 mAh g^-1 when the current density is switched to 5 C (8.37 A g^-1). Impressively, after 450 cycles, the FeNiS₂ QDs@SPAN electrode maintains 86.6% capacity retention (624 mAh g^-1), corresponding to a low fade rate of 0.029% per cycle. For the SPAN electrode, the discharge capacity is only 500 mAh g^-1 when initially cycled at 5 C, and it can barely be cycled after 200 cycles. The superior performance of FeNiS₂ QDs@SPAN electrode highlights the role of FeNiS₂ QDs with enhanced adsorption and catalytic sites, which promotes the efficient conversion reaction between lithium polysulfides and Li₂S, and endows the high capacity as well as improved cycle stability over extended cycles.

The long-term cycling test results in Figure 3E reveal that the FeNiS₂ QDs@SPAN cathode delivers an initial specific discharge capacity as high as 1,210 mAh g^-1 under 1 C, with an ultra-low average capacity decay rate of only 0.034% across 1,000 cycles. After 1,000 cycles, the Coulombic Efficiency (CE) of the FeNiS₂ QDs@SPAN cathode can still be stabilized at 99.3%. In contrast, the SPAN cathode initially shows a comparable discharge capacity to the FeNiS₂ QDs@SPAN cathode, and it suffers a drastic capacity drop with the capacity retention of only 24% after 500 cycles at 1 C. This suggests that the FeNiS₂ QDs show a pronounced effect in facilitating the thorough and rapid conversion of the sulfur redox reaction, which sustains the high utilization efficiency of the active materials. Supplementary Figure 6 shows the morphology of the FeNiS₂ QDs@SPAN cathode observed after 200 cycles at 1 C, demonstrating it still maintain its fiber structure after cycling. The above results indicate that FeNiS₂ QDs are crucial for enhancing the reaction kinetics, rate performance, and long-term cycling stability of the FeNiS₂ QDs@SPAN cathode. For comparison, we have collated the electrochemical performance metrics of SPAN-based cathode materials reported in prior works, as summarized in Supplementary Table 2^{[30,44,46-52]}. It can be seen that the rate capacity and cyclic stability of the FeNiS₂ QDs@SPAN electrode are superior to those reported in the literature. Particularly, the FeNiS₂ QDs@SPAN cathode achieves 450 stable cycles at 5 C (8.37 A g^-1), a record cycle and rate performance for SPAN-based cathode, according to the authors’ best knowledge^{[29,30,44,49,53-56]}.

To investigate the catalytic properties of the FeNiS₂ QDs@SPAN composite in lithium-sulfur reactions, the corresponding electrocatalytic performance was systematically investigated by combining CV with Tafel measurements. The typical CV curves of the two electrodes, obtained at a scan rate of 0.2 mV s^-1, are illustrated in Figure 4A. Two well-resolved broad cathodic peaks at 2.08 and 1.73 V can be clearly observed for the FeNiS₂ QDs@SPAN nanofiber electrode, originating from the stepwise electrochemical reduction of short-chain sulfur to Li₂S₂ and Li₂S, in sequence^[29]. For SPAN, merely a single broad cathodic peak emerges at 1.62 V, a feature indicative of pronounced polarization along with a shift toward lower potentials. These results confirm that FeNiS₂ QDs can expedite the reduction reaction of SPAN and enhance the reaction kinetics during the discharging process. To better understand the catalytic activity of FeNiS₂ QDs, we compared the Tafel plots for a single cathodic and anodic process, respectively, as shown in Figure 4B and C. For the reduction process, the estimated Tafel slope for the FeNiS₂ QDs@SPAN cathode is 131.2 mV dec^-1, which is significantly smaller than that of the SPAN electrode (317.3 mV dec^-1). Similarly, for the oxidation process, the FeNiS₂ QDs@SPAN cathode exhibits a lower Tafel slope of 0.998 V dec^-1 in comparison with the SPAN electrode (1.634 V dec^-1). This indicates that with the FeNiS₂ QDs, lower polarization and enhanced redox conversion between LiPS and Li₂S of the FeNiS₂ QDs@SPAN electrode can be realized, in comparison to the SPAN electrode.

To further understand the improved kinetics of FeNiS₂ QDs@SPAN, EIS measurements were conducted. The results demonstrate significantly enhanced charge transfer capability of the FeNiS₂ QDs@SPAN composite before and after cycling. Before cycling, the Nyquist plots [Figure 4D] exhibited characteristic impedance spectra, which comprise a distinct high-frequency semicircle attributed to the interfacial charge transfer resistance (R_ct), as well as a diagonal line at low frequency related to the Warburg impedance (W_o) of Li⁺ diffusion in the electrode. Analysis of the fitting data shows that FeNiS₂ QDs@SPAN exhibits substantially lower R_ct (124.5 Ω) than the SPAN electrode (198.7 Ω) before cycling [Supplementary Table 3]. Furthermore, Figure 4E confirms that the R_ct of FeNiS₂ QDs@SPAN after cycling remains markedly lower than that of SPAN, which is attributable to the composite's superior catalytic properties in promoting Li₂S₂/Li₂S conversion kinetics [Supplementary Table 3]. Additionally, Variable-scan-rate CV (0.2-1 mV s^-1) and Galvanostatic Intermittent Titration Technique (GITT) investigation further confirm the fast reaction kinetics of FeNiS₂ QDs@SPAN, as manifested by enhanced Li diffusion coefficient obtained via the two methods (details see Figure 4F and G, Supplementary Figures 7 and 8).

The adsorption behavior of Li₂S_n (n = 1, 2) on FeNiS₂ was further investigated by DFT calculations. The (102) crystal plane is selected for the DFT calculation since the XRD pattern of the synthesized FeNiS₂ shows that (102) is the strongest peak [Figure 2I]. Figure 4H and I, Supplementary Figure 9 illustrate the optimized adsorption configurations and the corresponding top views of Li₂S and Li₂S₂ on the FeNiS₂ (102) surface, respectively. The adsorption energies of Li₂S₂ and Li₂S on the FeNiS₂ (102) surface are computed to be -7.77 and -10.11 eV, respectively. These values are significantly more negative than those on pyridine nitrogen sites (in N-doped carbon)^[57,58], demonstrating that the introduction of FeNiS₂ provides much stronger anchoring for Li₂S₂ and Li₂S. It might lead to the formation of Li₂S₂ and Li₂S close to the homogeneously dispersed FeNiS₂ during the reduction reaction, which further facilitates the conversion reaction between LiPS and Li₂S₂/Li₂S.

To investigate the feasibility of FeNiS₂ QDs@SPAN for extreme environmental conditions, the performance of SPAN electrodes across a broad temperature range was further evaluated.As shown in Figure 5A and Supplementary Figure 10A, the FeNiS₂ QDs@SPAN cathode delivered a remarkable specific discharge capacity of 751 mAh g^-1 at 0.5 C under 0 °C. Despite the increased electrolyte viscosity and sluggish reaction kinetics at 0 °C, the FeNiS₂ QDs@SPAN cathode still maintained 71% of its initial capacity after 120 cycles. This outstanding cycle stability of FeNiS₂ QDs@SPAN cathode at 0 °C arises from the high electrocatalytic activity of FeNiS₂ QDs, which effectively promotes polysulfide conversion and enhances the reaction kinetics. In stark contrast, SPAN electrode shows an initial capacity of merely 440 mAh/g at 0 °C. It suffers rapid capacity decay and short-circuit after only 60 cycles, demonstrating very poor low-temperature tolerance. The high-temperature cycling performance at 60 °C is presented in Figure 5B and Supplementary Figure 10B. After two activation cycles at 0.1 C, the FeNiS₂ QDs@SPAN composite cathode achieved an impressive specific discharge capacity of 1,487 mAh g^-1 at a current rate of 1 C, and retained a capacity retention of 83% after 120 cycles. By comparison, the SPAN cathode only delivered a much lower specific capacity of 1,054 mAh g^-1 at 1 C and 60 °C. The results highlight that the effects of FeNiS₂ QDs on boosting the reaction kinetics and overall electrochemical performance of the SPAN cathode in the temperature range of 0 and 60 °C.

To demonstrate the commercial viability of FeNiS₂ QDs@SPAN material, its performance was tested under high sulfur loading and lean electrolyte environments. Coin cells with 5 mg cm^-2 FeNiS₂ QDs@SPAN electrode and different electrolyte-to-sulfur (E/S) ratios of 7, 10, 14, and 18 µL mg^-1 were assembled and their performance was evaluated. All cells exhibit similar galvanostatic charge-discharge profiles, and maintain the characteristic SPAN charge-discharge curves [Supplementary Figure 11]. With a lower E/S ratio of 7 µL mg^-1, the polarization is slightly increased. Cycle stability under varied E/S ratios was further investigated. As shown in Figure 5C and D, Supplementary Figure 12, the initial specific capacities of FeNiS₂ QDs@SPAN in all cells are almost same, which confirms the sulfur utilization is unaffected with different E/S ratios. Specifically, the capacities of FeNiS₂ QDs@SPAN in the cells with E/S ratios of 7, 10, 14, and 18 µL mg^-1 are 1,173, 1,159, 1,174, and 1,169 mAh g^-1, respectively. For the cells with E/S ratios of 10, 14, 18 µL mg^-1, they show excellent cycle stability, and the capacity retention is 97.9%, 96.1%, and 98.7% over 120 cycles, respectively. When tested at a lean electrolyte condition with an E/S ratio as low as 7 µL mg^-1, the cell exhibited a gradual capacity decay, and retained 70.6% of its initial capacity after 100 cycles. This performance degradation is mainly ascribed to the increased voltage polarization, as illustrated in Supplementary Figure 10.The results suggest that FeNiS₂ QDs@SPAN electrode with 5 mg cm^-2 mass loading exhibits excellent cycling performance when the E/S ratio is above 10 µL mg^-1. It demonstrates promising application potential of FeNiS₂ QDs@SPAN material for lithium sulfur batteries.

In summary, this work aims to address the intrinsically slow reaction kinetics of SPAN cathodes for Li-S batteries by fabricating FeNiS₂ QDs@SPAN nanofibers via electrospinning coupled with sulfurization heat treatment. The embedded FeNiS₂ QDs act as efficient catalytic sites, which reduce the cathode charge transfer resistance and accelerate the conversion of short-chain polysulfides to Li₂S, thereby effectively boosting the intrinsic reaction kinetics of SPAN. This catalytic modification endows the FeNiS₂ QDs@SPAN cathode with excellent rate performance, cycling stability, and reliable electrochemical performance under harsh working conditions including a wide temperature range and lean electrolyte. Further optimization of electrode structure may enhance the performance of Li//FeNiS₂ QDs@SPAN battery under even leaner electrolyte conditions. This study verifies that integrating FeNiS₂ QDs catalysts into SPAN nanofibers is a feasible and effective strategy for advancing SPAN-based Li-S batteries, and it provides a valuable reference for the design of high-performance catalytic electrodes for high-energy-density Li-S batteries.