Anode Material For Sodium-ion Batteries Research Articles

Pomegranate-like heterostructured SnS2/CoS2 particles encapsulated in S, N dual-doped carbon framework enabling high-rate and durable sodium ion storage

As a promising anode material for sodium-ion batteries, SnS2 has attracted increasing attention owing to its high theoretical capacity and abundant reserves. Unfortunately, the poor electrical conductivity and drastic volume changes lead to unsatisfactory cycling and rate performance, largely limiting its practical application. Herein, we report a pomegranate-like composite of heterostructured SnS2/CoS2 spheres encapsulated in S, N dual-doped carbon framework (SnS2/CoS2@SNC) obtained by a simple ion adsorption, in situ polymerization coating of polydopamine and subsequent calcination strategy. The integration of CoS2 with SnS2 particles with abundant interfaces can provide rich redox chemistry and accelerated ion diffusion kinetics, while the coated S, N dual-doped carbon shell enables good electrical conductivity and reinforced structural integrity as well by accommodating the volume changes and inhibiting the collapse/pulverization of active materials during the cycling process. As a consequence, the pomegranate-like heterostructured SnS2/CoS2@SNC anode exhibited a higher capacity (743 mAh g−1 at 1 A g−1), excellent rate capability (213 mAh g−1 at 50 A g−1) and outstanding cycling stability (560 mAh g−1 at 5 A g−1 after 1000 cycles), showing the application feasibility of this anode material for developing high-rate and durable SIBs.

Biomass carbon-reinforced zinc-based composite oxide as an anode for superior sodium storage

The pursuit of high-abundance, cost-effective sodium-ion batteries represents a longstanding and valuable objective in the field. However, significant challenges remain in the quest for breakthroughs, particularly in the discovery of high-performance anode materials and a deeper understanding of the sodium storage mechanism. In this study, we present novel insights into the sodium storage properties of biomass carbon-reinforced Zn2P2O7 (Zn2P2O7/C-c) synthesized via a hydrothermal method followed by annealing, marking the first report of its kind. The unique loose porous structure of the Zn2P2O7/C-c composite offers multiple advantages. It facilitates efficient electrolyte infiltration, enhances the diffusion pathways for sodium ions, expedites electron transfer, and crucially, promotes the retention of Zn2P2O7 on the carbon substrate, even under conditions of mechanical stress or pulverization. Consequently, the Zn2P2O7/C-c composite demonstrates significantly improved rate capability, exhibiting specific capacities of 276.11, 234.41, 195.28, and 149.56 mA h g−1 at current densities of 0.2, 0.5, 1, and 2 A g−1, respectively. Furthermore, it exhibits exceptional cyclic stability with a capacity retention rate of 71% after 1000 charge-discharge cycles at 1 A g−1. In-depth in-situ/ex-situ characterization techniques confirm that the sodium storage mechanism involves a conversion reaction between Zn2P2O7 and Zn, as well as an alloying reaction between Zn and ZnNa13. Kinetic analysis underscores the predominant role of pseudocapacitance in facilitating sodium storage, particularly at high charge-discharge rates. These findings offer valuable insights and inspiration for the exploration of high-performance Zn2P2O7-based anode materials for sodium-ion batteries, representing a significant step toward the realization of cost-effective and efficient sodium-ion battery technology in the future.

Comparison and optimization of biomass-derived hard carbon as anode materials for sodium-ion batteries

Hard carbon made from biomass-based precursors has many advantages as anode for sodium-ion batteries such as low cost and sustainability. In this work, three different hard carbon materials derived from bamboo, wood and coconut shell with the same particle size are screened, combining acid etching and carbonization at 1200 °C, to compare the sodium ion storage performances. The anode material originated from bamboo shows the highest specific capacity among them. Subsequently, the hard carbon from bamboo is optimized by the same process, but changing the carbonization temperature ranging from 1000 °C to 1400 °C. Among the hard carbon materials, the bamboo-derived one prepared at 1300 ℃ exhibits excellent electrochemical performances at a current density of 30 mA g−1, with a high reversible specific capacity of 303.8 mAh/g and an initial coulombic efficiency of 83.7 %. After 150 cycles, a capacity retention of 94.7 % is achieved at a current density of 300 mA g−1. This work provides a potential hard carbon anode for sodium-ion batteries to realize large-scale energy storage due to the cheap sources of bamboo.

Theoretical prediction of two-dimensional CrSi2N4 as a potential anode material for Na-ion batteries

Efficient anode materials are critical for high-performance rechargeable lithium-ion batteries (LIBs) and sodium-ion batteries. This paper systematically investigates the potential of the CrSi2N4 monolayer as anode material for LIBs and sodium-ion batteries by first-principles density functional theory calculations. It was found that CrSi2N4 exhibits outstanding performance in sodium-ion batteries, with a low diffusion energy barrier of 0.10 eV and a high theoretical specific capacity of 490 mAh g−1. Meanwhile, the average open circuit voltage is 0.47 V, comparable to the typical anode materials. In addition, a small lattice constant change of 0.3%–3.1% ensures the cycling stability of CrSi2N4 in sodium-ion batteries. This work suggests a promising candidate anode material for sodium-ion batteries.

Heterogeneous engineering and carbon confinement strategy to synergistically boost the sodium storage performance of transition metal selenides

Transition metal selenides (TMSs) stand out as a promising anode material for sodium-ion batteries (SIBs) owing to their natural resources and exceptional sodium storage capacity. Despite these advantages, their practical application faces challenges, such as poor electronic conductivity, sluggish reaction kinetics and severe agglomeration during electrochemical reactions, hindering their effective utilization. Herein, the dual-carbon-confined CoSe2/FeSe2@NC@C nanocubes with heterogeneous structure are synthesized using ZIF-67 as the template by ion exchange, resorcin-formaldehyde (RF) coating, and subsequent in situ carbonization and selenidation. The N-doped porous carbon promotes rapid electrolyte penetration and minimizes the agglomeration of active materials during charging and discharging, while the RF-derived carbon framework reduces the cycling stress and keeps the integrity of the material structure. More importantly, the built-in electric field at the heterogeneous boundary layer drives electron redistribution, optimizing the electronic structure and enhancing the reaction kinetics of the anode material. Based on this, the nanocubes of CoSe2/FeSe2@NC@C exhibits superb sodium storage performance, delivering a high discharge capacity of 512.6 mA h g−1 at 0.5 A g−1 after 150 cycles and giving a discharge capacity of 298.2 mA h g−1 at 10 A g−1 with a CE close to 100.0 % even after 1000 cycles. This study proposes a viable method to synthesize advanced anodes for SIBs by a synergy effect of heterogeneous interfacial engineering and a carbon confinement strategy.

Metal-organic frameworks derived flower-like V2O3/C/N for high‐performance sodium storage

Vanadium oxide is a promising anode material for sodium-ion batteries due to its high theoretical capacity. However, its electrochemical performance is limited by its low electron transport capacity. To address this issue, we synthesized V2O3/C/N materials with a flower-like structure composed of ultra-thin nanosheets using V-MOFs as a template. The flower-like structure composed of nanosheets shortens the diffusion distance of sodium ions. Additionally, N doping regulates the electronic structure of the carbon layer and introduces defects, improving conductivity and generating more active sites. Consequently, V2O3/C/N-550 demonstrates outstanding electrochemical performance. It achieves an initial coulombic efficiency (ICE) of 90.5% at 0.1 A/g, with the highest capacity reaching 332.4 mAh/g. Even after 300 cycles, the capacity remains at 107.6% of its initial value. Additionally, it exhibits a discharge capacity of 190.7 mAh/g at 2 A/g. CV and GITT analyses confirm that V2O3/C/N-550 has a higher pseudocapacitance contribution and sodium ion diffusion kinetics. This can be attributed to its higher crystallinity, the flower-like structure composed of nanosheets, and the synergistic effect of N-doped carbon. Overall, this study provides valuable insights for the development of high-performance sodium-ion anode materials.

Structural engineering of MoSe2 via interfacial effect and phosphorus doping incorporation for high energy density sodium ion storage

Sodium-ion batteries (SIBs) are gaining increasing attention for the development of electrode materials due to their potential to alleviate the safety concerns and resource scarcity associated with lithium-ion batteries (LIBs). Based on this, the present work, built upon the electrospinning preparation of hollow carbon nanofibers (HCNFs), facilitated the in-situ growth of MoSe2 nanosheets on their surface. Subsequently, an in-situ phosphorization treatment was applied, resulting in phosphorus-doped MoSe2 (P-MoSe2)@HCNFs. The dual-channel inner layer of HCNFs in this structure promotes ion transport and directly interfaces with MoSe2, leading to abundant interfacial effects. The outer layer of MoSe2 serves as the primary redox-active unit for sodium ions, retaining numerous active sites. P doping further optimizes the overall electronic structure of the material. P-MoSe2@HCNFs serves as the anode material in SIBs, demonstrating exceptional reversible specific capacity and rate capabilities. It achieves a remarkable 479.17 mAh g−1 over 500 cycles at 1 A g−1 and 397.01 mAh g−1 over 950 cycles at 10 A g−1, showcasing its outstanding performance. These values significantly surpass those of MoSe2@HCNFs and pure MoSe2, validating the pronounced advantages of the structure we have constructed. Leveraging the outstanding kinetic performance of P-MoSe2@HCNFs, when assembled with Na3V2(PO4)3 as the cathode, the full cell exhibits remarkable sodium storage capability. It achieves a high energy density of up to 194.75 Wh kg−1, providing a feasible solution for the application of transition metal selenides in sodium-ion battery systems.

Precursor screening of fruit shell derived hard carbons for low-potential sodium storage: A low lignin content supports the formation of closed pores

Biomass hard carbons are being explored for anode materials of sodium-ion batteries due to the wide availability. However, the precursor screening for optimal microstructure and sodium storage performance is tedious and time-consuming. Here, we selected three kinds of fruit shells to prepare hard carbons for sodium-ion batteries and investigated their structure characteristics and sodium storage performance. It is demonstrated that a low lignin content in fruit shells is favor to the formation of closed pores in the derived hard carbons, thus generating a high low-potential plateau capacity. Among the main component of biomass, lignin with rich aromatic ring structure possesses higher thermal stability than cellulose and hemicellulose. During the pyrolysis and carbonization, lignin may decompose to large-size crystalline domains, which hinders the random stacking of carbon layers. Therefore, as the lower lignin content than pine nut shell and macadamia nut shell (28.4% vs. 39.2% and 37.4%), the walnut shell derived hard carbon shows a largest interlayer distance of 0.397 nm and a highest closed pore area of 391 m2 g−1, contributing to the supreme specific capacity of 362.6 mAh g−1, with a plateau capacity of 195.8 mAh g−1 as well as a remarkable cycle stability. The assembled WNSC//NVP full-cell remains a discharge capacity of 53.1 mAh g−1 after 100 cycles at 0.1 A g−1. This work gives a deep insight of the relationship between biomass composition and microstructure of the derived hard carbons to explore its high sodium storage ability in low-potential region.

Progress and Prospect of Bimetallic Oxides for Sodium-Ion Batteries: Synthesis, Mechanism, and Optimization Strategy.

Sodium-ion batteries (SIBs) are considered as an alternative to and even replacement of lithium-ion batteries in the near future in order to address the energy crisis and scarcity of lithium resources due to the wide distribution and abundance of sodium resources on the earth. The exploration and development of high-performance anode materials are critical to the practical applications of advanced SIBs. Among various anode materials, bimetallic oxides (BMOs) have attracted special research attention because of their abundance, easy access, rich redox reactions, enhanced capacity and satisfactory cycling stability. Although many BMO anode materials have been reported as anode materials in SIBs, very limited studies summarized the progress and prospect of BMOs in practical applications of SIBs. In this review, recent progress and challenges of BMO anode materials for SIBs have been comprehensively summarized and discussed. First, the preparation methods and sodium storage mechanisms of BMOs are discussed. Then, the challenges, optimization strategies, and sodium storage performance of BMO anode materials have been reviewed and summarized. Finally, the prospects and future research directions of BMOs in SIBs have been proposed. This review aims to provide insight into the efficient design and optimization of BMO anode materials for high-performance SIBs.

A Review on the Upgradation of Biomass-derived Hard Carbon Materials

Abstract: Sodium-ion battery is a promising alternative to lithium-ion battery because of its abundant raw material resources, low price, and high specific capacity. Amorphous carbon materials (hard carbon) have micropores and impurities, facilitating the intercalation of sodium ions to form "quasi-metallic sodium," resulting in a high sodium storage capacity and a low sodium storage potential. Consequently, hard carbon is one of the most widely studied negative electrode materials. It can be prepared from biomass by thermochemical conversion and has the advantages of large specific capacity, low cost, good cycling stability, and renewability. This review focuses on the recent advances in biomass-based hard carbon materials. Firstly, the preparation methods of hard carbon, including precursor selection, pretreatment, drying methods, and carbonization processes, are summarized. Secondly, the effects of precursor composition and heteroatom doping structure and properties of hard carbon are examined, and the changes in carbon material pores during the activation process, as well as the selection of optimal drying method, pyrolysis temperature, carbonization temperature, activator dosage, and additive, are discussed. Thirdly, the impact of preparation methods on hard carbon's cost, efficiency, and stability is briefly summarized, and the relevant improvement measures and prospects are proposed. Finally, some insights are provided into preparing highperformance biomass-based anode materials for sodium-ion batteries.

Strongly coupled C@MoSe2@OMWCNT heterostructure as an anode for sodium-ion batteries

MoSe2, with its extraordinary theoretical capacity, has emerged as a profoundly auspicious anode material for Sodium-ion Batteries (SIBs). However, the actual realization of SIBs encounters hurdles arising from insufficient electron and ion transportation capabilities, along with the irreversible transformation of Mo/Na2Se into MoSe2, eventually substituted by Mo/Se. In this investigation, By employing Mo-based complexes, we have achieved a triumphant synthesis of C@MoSe2@OMWCNT (oxidized multiwall carbon nanotubes) materials, wherein OMWCNTs serve as the fundamental substrate. Theoretical analysis has revealed that the utilization of OMWCNTs not only enhances the structural stability of the anode materials but also improves the electrical conductivity and Na+ ion mobility (the Na+ diffusion barrier: (MoSe2) 0.91 eV vs (C@MoSe2@OMWCNT) 0.41 eV) of the C@MoSe2@OMWCNT. These properties make C@MoSe2@OMWCNT a promising candidate for the development of high-performance SIBs. Furthermore, the Ex-situ Transmission Electron Microscopy (TEM) examination, unveils the emergence of Se and MoSe2 within the C@MoSe2@OMWCNT. The findings indicate that the outer carbon coating layer efficiently prevents contact between Se and the electrolyte, thereby impeding the formation of polyselenides. When C@MoSe2@OMWCNT is employed as the anode for the SIB, it exhibits exceptional cycle stability, with a capacity of 303 mA h g−1 and 189 mA h g−1 after 500 and 3000 cycles, respectively, under a current density of 5 A g−1. Overall, this investigation provides valuable insights into the design and synthesis of advanced anode materials for SIBs, which could have significant implications for the development of next-generation energy storage devices.

A Defective Disc-Like Cu1.96S Anode Material with the Efficient Cu Vacancies for High-Performance Sodium-Ion Storage.

Due to their significant capacity and reliable reversibility, transition metal sulphides (TMSs) have received attention as potential anode materials for sodium-ion batteries (SIBs). Nonetheless, a prevalent challenge with TMSs lies in their significant volume expansion and sluggish kinetics, impeding their capacity for rapid and enduring Na+ storage. Herein, a Cu1.96S@NC nanodisc material enriched with copper vacancies is synthesised via a hydrothermal and annealing procedure. Density functional theory (DFT) calculations reveal that the incorporation of copper vacancies significantly boosts electrical conductivity by reducing the energy barrier for ion diffusion, thereby promoting efficient electron/ion transport. Moreover, the presence of copper vacancies creates ample active sites for the integration of sodium ions, streamlines charge transfer, boosts electronic conductivity, and, ultimately, significantly enhances the overall performance of SIBs. This novel anode material, Cu1.96S@NC, demonstrates a reversible capacity of 339mAhg-1 after 2000 cycles at a rate of 5Ag-1. In addition, it maintains a noteworthy reversible capacity of 314mAhg-1 with an exceptional capacity retention of 96% even after 2000 cycles at 20Ag-1. The results demonstrate that creating cationic vacancies is a highly effective strategy for engineering anode materials with high capacity and rapid reactivity.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.

Superior initial Coulombic efficiency and areal capacity of hard carbon anode enabled by graphite-assisted carbonization for sodium-ion battery

Hard carbons are perceived as promising anode materials in sodium-ion batteries, while their practical implementation is largely impeded by the insufficient initial Coulombic efficiency (ICE). Hard carbons with self-supporting architecture are intriguing to enhance ICE owing to the omission of binder and conductive agent; whereas elaborate architecture and microstructure design are still required to further raise the ICE to the level of commercial graphite in lithium-ion batteries, especially under high areal capacity. Herein, we propose a graphite-assisted pressurization strategy during carbonization to achieve remarkable ICE and high areal capacity in resulting self-supporting cellulose tissue derived hard carbon anode. The intimate contact of graphite plate enables suitable local ordering of pseudo-graphitic nanodomains with low intrinsic defects, responsible for enhanced ICE. While the pressure-reinforced dense yet self-interwoven fibrous networks render high areal capacity. Consequently, the as-prepared self-supporting hard carbon anode displays remarkable ICE to 95% and areal capacity of 2.4 mAh cm−2, far exceeding the reported value of less than 0.8 mAh cm−2. Meanwhile, the rate and durability are not scarified under such superior ICE due to the well-manipulated pseudo-graphitic nanodomains and porous fibrous networks. The practicality is further demonstrated in coin-type and pouch-type full cells delivering high capacity and long-term stability. Our finding offers an impetus for the development of high ICE and areal capacity for sodium-ion battery anode.

Low‐Temperature Sodium‐Ion Batteries: Challenges and Progress

AbstractAs an ideal candidate for the next generation of large‐scale energy storage devices, sodium‐ion batteries (SIBs) have received great attention due to their low cost. However, the practical utility of SIBs faces constraints imposed by geographical and environmental factors, particularly in high‐altitude and cold regions. In these areas, the low‐temperature (LT) performance of SIBs presents a pressing technological challenge that requires significant breakthroughs. In LT environments, the electrochemical reaction kinetics of SIBs are sluggish, the electrode/electrolyte interface is unstable, and the diffusion of sodium ions in electrode materials is slow, leading to a decrease in battery performance. Therefore, the reasonable design of electrolyte and electrode materials is of great significance for optimizing the LT performance of SIBs. In this review, the research progress of LT SIBs electrolytes, cathode, and anode materials, as well as sodium metal batteries and solid‐state electrolytes is systematically summarized in recent years, aiming to understand the design principles of LT SIBs, clarify the basic research and development of high‐performance SIBs in practical applications, and promote the development of SIBs technology in the full temperature range.

Flexible Self-Supporting MOF-Based Bean Pod Cube Hollow Nanofibers for Ultralong Cycling and High Rate Na Storage.

Sodium-ion batteries (SIBs) have garnered significant attention due to their potential as an emerging energy storage solution. Tin sulfide (SnS) has emerged as a promising anode material for SIBs due to its impressive theoretical specific capacity of 1022 mA h g-1 and excellent electrical conductivity. However, its practical application has been hindered by issues such as large volume expansion, which adversely affects cycling stability and rate performance during the charge/discharge processes. In this study, a novel approach to address these issues by synthesizing the bean pod cube hollow metal-organic framework (MOF)-SnSx/NC@N-doped carbon nanofibers through a process involving electrospinning, PDA coating, and calcination. The Sn-MOF serves as a self-sacrificing template, facilitating the simultaneous dissociation of MOF and polymerization of dopamine, leading to the creation of hollow intermediates that retain tin components. Subsequent sulfidation results in the integration of the hollow MOF-SnSx/NC nanoparticles within 3D nitrogen-doped carbon nanofibers, forming the distinctive bean pod cube composite structure. This unique configuration effectively shortens the diffusion path and mitigates volume expansion for sodium ions, ultimately yielding an exceptional high rate performance of 130 mA h g-1 (10 A g-1) and an ultralong cycling performance of 328 mA h g-1 even after 3500 cycles (2 A g-1) as the anode for SIBs.

Microporous Sulfur-Carbon Materials with Extended Sodium Storage Window.

Developing high-performance carbonaceous anode materials for sodium-ion batteries (SIBs) is still a grand quest for a more sustainable future of energy storage. Introducing sulfur within a carbon framework is one of the most promising attempts toward the development of highly efficient anode materials. Herein, a microporous sulfur-rich carbon anode obtained from a liquid sulfur-containing oligomer is introduced. The sodium storage mechanism shifts from surface-controlled to diffusion-controlled at higher synthesis temperatures. The different storage mechanisms and electrode performances are found to be independent of the bare electrode material's interplanar spacing. Therefore, these differences are attributed to an increased microporosity and a thiophene-rich chemical environment. The combination of these properties enables extending the plateau region to higher potential and achieving reversible overpotential sodium storage. Moreover, in-operando small-angle X-ray scattering (SAXS) reveals reversible electron density variations within the pore structure, in good agreement with the pore-filling sodium storage mechanism occurring in hard carbons (HCs). Eventually, the depicted framework will enable the design of high-performance anode materials for sodium-ion batteries with competitive energy density.

Zn/Co-ZIF-Derived Composites as High-Performance Anode Materials for Sodium-Ion Batteries

Zn/Co-ZIF-Derived Composites as High-Performance Anode Materials for Sodium-Ion Batteries

Unleashing the Power of Sn2S3 Quantum Dots: Advancing Ultrafast and Ultrastable Sodium/Potassium-Ion Batteries with N, S Co-Doped Carbon Fiber Network.

Tin sulfide (Sn2S3) has been recognized as a potential anode material for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its high theoretical capacities. However, the sluggish ion diffusion kinetics, low conductivity, and severe volume changes during cycling have limited its practical application. In this study, Sn2S3 quantum dots (QDs) (≈1.6nm) homogeneously embedded in an N, S co-doped carbon fiber network (Sn2S3-CFN) are successfully fabricated by sequential freeze-drying, carbonization, and sulfidation strategies. As anode materials, the Sn2S3-CFN delivers high reversible capacities and excellent rate capability (300.0 mAh g-1 at 10 A g-1 and 250.0 mAh g-1 at 20 A g-1 for SIBs; 165.3 mAh g-1 at 5 A g-1 and 100.0 mAh g-1 at 10 A g-1 for PIBs) and superior long-life cycling capability (279.6 mAh g-1 after 10 000 cycles at 5 A g-1 for SIBs; 166.3 mAh g-1 after 5 000 cycles at 2 A g-1 for PIBs). According to experimental analysis and theoretical calculations, the exceptional performance of the Sn2S3-CFN composite can be attributed to the synergistic effect of the conductive carbon fiber network and the Sn2S3 quantum dots, which contribute to the structural stability, reversible electrochemical reactions, and superior electron transportation and ions diffusion.

A superior sodium-ion anode material from PAN/lignin-derived carbon nanofibers with inter-connected structure prepared through phosphoric acid induced cross-linking

A feasible route to fabricate phosphorus-doped carbon nanofibers (P-CNFs) with an inter-connected structure has been demonstrated through electrospinning, stabilization, and subsequent phosphoric acid impregnation and carbonization processes using polyacrylonitrile and lignin as carbon sources. The results illustrate that the phosphoric acid induced cross-linking could be beneficial to acquire the closed-pore structure and the heteroatom-doped surface chemistry of nanofibers. As a result, the P-CNFs exhibit higher interlayer spacing of graphite and lower BET specific surface area compared to the pristine CNFs. The P-CNFs as an anode material for sodium-ion batteries (SIBs) present a high reversible capacity 278 mA h g−1 at 0.2 A g−1 and a superior initial Coulomb efficiency (ICE) of 78.86 %. Moreover, the reversible capacity of P-CNFs can be stably maintained near the initial capacity after 5000 cycles at 1 A g−1, showing exceptional structural stability and cycling durability. Meanwhile, the sodium storage mechanism of P-CNFs was investigated using in-situ Raman and ex-situ XRD analysis to understand the exceptional structural stability and Na+ adsorption capacity of P-CNFs. This work provides valuable insights for the design of carbon nanofibers with an inter-connected structure as anode materials for SIBs, exhibiting outstanding electrochemical properties.