Anode For Sodium-ion Batteries Research Articles

Advanced Structural Engineering Design for Tailored Microporous Structure via Adjustable Graphite Sheet Angle to Enhance Sodium‐Ion Storage in Anthracite‐Based Carbon Anode

AbstractCarbon material has emerged as a highly promising anode for sodium‐ion batteries (SIBs) due to its abundance of resources, cost‐effectiveness, and high carbon yield. This work elaborately designs the precursor structure for the self‐assembly of melamine‐cyanuric acid on the anthracite surface through hydrogen bonding, and successfully constructs N‐doped carbon with tailored microstructure and expanded interlayer spacing. Serving as anode for SIBs, the optimized sample delivers high specific capacity (371.3 mAh g−1 at 0.05 A g−1), superior rate capability (295.8 mAh g−1 at 10.0 A g−1), and excellent ultra‐long cycling performance (the retention of 91.5% after 3000 cycles at 0.5 A g−1). The systematic investigations reveal the enhancement of sodium‐ion storage in the low‐voltage plateau region involving the interlayer intercalation coupled with nanopores filling. It is discovered that the microporous structure formed by the appropriate graphite sheet angle influences the migration and storage of sodium ions. Density functional theory calculations indicate that the adsorption capacity for sodium ion is enhanced and the migration energy barrier perpendicular to the graphite layer is reduced at the appropriate angle of 8°. This study provides novel insights into the sodium‐ion storage mechanism, offering guidance for the better design of anthracite‐based carbon anode with superior performance.

Fullerene Intercalation of MXene Toward Super‐Long‐Cycle Sodium Ion Storage

Abstract2D layered MXene‐based materials are applied as cation‐intercalation electrode materials for sodium‐ion batteries (SIBs) due to their layered structures but suffer from spontaneous restacking during Na+ insertion and deintercalation processes, resulting in sluggish reaction kinetics and poor cycling stability. Herein, fullerene C60 is intercalated covalently into the interlayer of Ti3C2Tx MXene nanosheets by using a low‐temperature hydrothermal reaction between a water‐soluble C60 derivative and hydrophilic MXene nanosheets, resulting in enlarged interlayer spacing of MXene nanosheets from 12.8 to 14.1 Å and consequently retarded self‐restacking. Moreover, the strong electron extraction ability of C60 facilitates electron transfer from MXene to C60, enabling faster charge transport during Na+ transportation. The as‐prepared C60@MXene hybrid is applied as a novel anode of SIBs, exhibiting outstanding electrochemical performance and super‐long cycling stability. C60@MXene‐based SIB delivers a specific capacity of 226.8 mAh g−1 at 0.1 A g−1 after 300 cycles, which surpasses that obtained from the pristine MXene anode, and retains 94.5% capacity at 1 A g−1 after 10 000 cycles. DFT simulations confirm that C60‐induced enlarged interlayer spacing benefits Na+ migrations, which is responsible for improved electrochemical performance and cycling stability.

N-doped 3D carbon encapsulating nickel selenide nanoarchitecture with cation defect engineering: An ultrafast and long-life anode for sodium-ion batteries

Transition metal chalcogenides (TMCs) hold great potential for sodium-ion batteries (SIBs) owing to their multielectron conversion reactions, yet face challenges of poor intrinsic conductivity, sluggish diffusion kinetics, severe phase transitions, and structural collapse during cycling. Herein, a self-templating strategy is proposed for the synthesis of a class of metal cobalt-doped NiSe nanoparticles confined within three-dimensional (3D) N-doped macroporous carbon matrix nanohybrids (Co-NiSe/NMC). The cation defect engineering within the developed Co-NiSe and 3D N-doped carbon plays a crucial role in enhancing intrinsic conductivity, reinforcing structural stability, and reducing the barrier to sodium ion diffusion, which are verified by a series of electrochemical kinetic analyses and density functional theory calculations. Significantly, such cation defect engineering not only reduces overpotential but also accelerates conversion reaction kinetics, ensuring both exceptional high-rate capability and extended durability. Consequently, the optimally engineered Co-NiSe/NMC demonstrates a remarkable rate performance, delivering 390 mAh g−1 at 10 A g−1. Moreover, it exhibits an unprecedented lifespan, maintaining a remarkable capacity of 403 mAh g−1 after 1400 cycles and 318 mAh g−1 after 4000 cycles, even at high rates of 1.0 and 2.0 A g−1, respectively. This work marks a substantial advancement in achieving both high performance and prolonged cycle life in sodium-ion batteries.

Boosting Molecular Cross-Linking in a Phenolic Resin for Spherical Hard Carbon with Enriched Closed Pores toward Enhanced Sodium Storage Ability.

Phenolic resin (PF) is considered a promising precursor of hard carbon (HC) for advanced-performance anodes in sodium-ion batteries (SIBs) because of its facile designability and high residual carbon yield. However, understanding how the structure of PF precursors influences sodium storage in their derived HC remains a significant challenge. Herein, the microstructure of HC is controlled by the degree of cross-linking of resorcinol-benzaldehyde (RB) resin. We reveal that robust molecular cross-linking in RB resin induced by hydrothermal treatment promotes closed-pore formation in the derived HC. The mechanism is devised for the decomposition of a highly cross-linked RB three-dimensional network into randomly stacked short-range graphitic microcrystals during high-temperature carbonization, contributing to the abundant closed pores in the derived HC. In addition, the high cross-linking degree of RB resin endows its derived HC with a small-sized spherical morphology and large interlayer spacing, which improves the rate performance of HC. Consequently, the optimized hydrothermal treatment HC anode shows a higher specific capacity of 372.7 mAh g-1 and better rate performance than the HC anode without hydrothermal treatment (276.0 mAh g-1). This strategy can provide feasible molecular cross-linking engineering for the development of closed pores in PF-based HC toward enhanced sodium storage.

Rational design of hollow C@SnS2/SnS@C cubes with N-doping to realize stepwise sodium storage induced structural stability for highly stable cycling performance

Current application of SnS2-based anodes in sodium-ion batteries fails to meet the demand for higher Na+ storage capacity due to the structural pulverization induced by significant volume changes during cycling. Herein, a novel composite of hollow C@SnS2/SnS@C cubes with excellent diffusion kinetics and structural stability from stepwise Na+ storage is designed. The SnS with gentle pseudocapacitive reaction acts as the self-supporter to prevent the collapse of SnS2/SnS heterostructure during the Na+ insertion/extraction. Together with the clamping of double carbon layers and hollow construction, the volume change caused structural instability in heterostructure is effectively alleviated. The rapid transport of electrons and ions within the built-in electric field of heterostructure endows the composite an excellent diffusion kinetics, which is generated from the narrow bandgap and outstanding Na+ absorption of heterostructure according to the first-principle calculation. Thus, the as-prepared composite maintains a remarkable capacity of 547.9 mAh g−1 after 200 cycles at current density of 0.5 A g−1. Even a capacity of 502.5 mAh g−1 with a low attenuation rate of 0.035 % per cycle is achieved at 2 A g−1 after 1000 cycles. The work proposes an effective approach to achieve effective Na + storage of SnS2-based anodes with long-lasting structural stability.

Controllable Preparation and Sodium Storage Properties of Sb2Te3–Te Heterojunction

Antimony-based materials possess high theoretical capacities and suitable potential, which could be promising anode materials for sodium-ion batteries (SIB). However, poor stabilities and sluggish kinetics are drawbacks. Building heterojunction is an ideal method to solve these issues. Its unique structure develops internal electric fields spontaneously to boost the charge transport and relieve stress. Nevertheless, the controllable preparation of face-to-face (2D) heterojunctions is still hard-pressed. Herein, Sb2Te3–Te nanoheterojunctions, which consist of two-dimensional Sb2Te3 nanoblades attached to a one-dimensional Te nanorod, are fabricated through a two-step solvothermal method. Among that, the density of nanoblades is adjustable through the engineering feed ratio. When employed as anodes for SIBs, Sb2Te3–Te nanoheterojunctions display a reversible capacity of 463.2[Formula: see text]mAh[Formula: see text]g[Formula: see text] at 100[Formula: see text]mA[Formula: see text]g[Formula: see text]. Even a capacity of 305.5[Formula: see text]mAh[Formula: see text]g[Formula: see text] remains after 1000 cycles under a high current of 1.5[Formula: see text]A[Formula: see text]g[Formula: see text]. Moreover, the density functional theory (DFT) calculations also identify the high conductivity of heterojunction. This work offers an effective way to design the structures and properties of heterojunctions, further expanding their application range.

Pb nanospheres encapsulated in metal–organic frameworks-derived porous carbon as anode for high-performance sodium-ion batteries

Alloying-type anode materials are considered promising candidates for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their application is limited by the severe capacity decay stemming from dramatic volume changes during Na+ insertion/extraction processes. Here, Pb nanospheres encapsulated in a carbon skeleton (Pb@C) were successfully synthesized via a facile metal–organic frameworks (MOFs)-derived method and used as anodes for SIBs. The nanosized Pb particles are uniformly incorporated into the porous carbon framework, effectively mitigating volume changes and enhancing Na+ ion transport during discharging/charging. Benefiting from this unique architecture, a reversible capacity of 334.2 mAh g−1 at 2 A g−1 is achieved after 6000 cycles corresponding to an impressive 88.2 % capacity retention and a minimal capacity loss of 0.00748 % per cycle. Furthermore, a high-performance full sodium-ion battery of Pb@C//NVPF was constructed, demonstrating a high energy density of 291 Wh kg−1 and power density of 175 W kg−1. This facile MOFs-derived method offers insights into the design of high-capacity alloy-type anode materials using Pb sources, opening up new possibilities for innovative approaches to Pb recycling and pollution prevention.

Phenolic Resin Derived Hard Carbon Anode for Sodium-Ion Batteries: A Review

Phenolic Resin Derived Hard Carbon Anode for Sodium-Ion Batteries: A Review

Bismuth-constructed high-speed channeled for Bi/Sb2SnO5@PCFs composite as high-rate and long-life anode for sodium-ion batteries

To cope with the charging-time and driving-range issues of the power batteries, a composite and phase modification tactics is manifested to increase the cycling stability and rate capability of the Sb2SnO5 (SSO) anode for sodium-ion batteries (SIBs). The as-fabricated Bi/SSO@PCFs composite with Bi nanocrystals homogeneously dispersed on and around the SSO surface is prepared by an electrospinning method. The excellently dispersed Bi nanocrystals realize an effective contact with SSO, which effectively lowers the electron conduction barriers and promotes the sodium ion release as well as the transport upon the desodiation/sodiation process, increasing the rate capacity and cycle stability of the SSO anode. Importantly, a high-speed ion channel is constructed through the special layered Bi, and SbBi phase. The prepared Bi/SSO@PCFs anodes deliver a high rate capacity up to 25 A g−1 and long cycle life of 5000 cycles with 83 % capacity retention rate, sustaining an average capacity loss of 0.0034 % for each cycle. Particularly, the intercalation of Na+ between layer-structure Bi and SbBi galleries provides a good basis for excellent cycle performance due to small volume change and unobstructed ion channels. This finding provides an effective strategy to establish ion transport highways, which essentially increase the rate-capacity and cycle-life of the SSO-based anodes for SIBs.

Study on Tin-Cobalt Bimetallic Phosphide Nanoparticles as a Negative Electrode of Sodium-Ion Batteries.

Tin phosphide (Sn4P3) holds great promise because sodium-ion batteries use this material as an anode with impressive theoretical capacity. In this paper, it is reported that Co-doped Sn4P3 is embedded into carbon-based materials and SnCoP/C with a porous skeleton is prepared. As a result, SnCoP/C-2, as the material utilized in sodium-ion battery anodes, exhibits reversible capacities at 415.6, 345.9, and 315.6 mAh g-1 at current intensities of 0.5, 1.0, and 2.0 A g-1, respectively. The electrochemical reversibility, cycle stability, and rate performance of SnCoP/C samples are obviously better than those of Sn4P3/C. Cobalt in SnCoP/C stabilizes the conductive matrix of tin phosphide and promotes the diffusion kinetics of sodium. These results show that, with an appropriate amount of cobalt doping, highly dispersed nanoparticles can be formed in the tin phosphide matrix, which can significantly enhance the cycle stability of tin-based electrode materials.

Vanadium nitride induced method to construct cobalt sulfides homologous heterojunction toward ultrafast and high-capacity sodium-ion storage

In recent years, heterojunction has attracted widespread attention as an anode for sodium-ion batteries since they can effectively optimize the materials’ rate performance and cycling stability. However, the advantage is choked by multi-element composition and stepwise synthesis process. Herein, cobalt sulfide (Co9S8/CoS) homologous heterojunction deposited at vanadium nitride/carbon nanofibers is synthesized as an excellent anode for high-performance sodium-ion batteries in one step by employing the “3d-orbital electron complementary effect” combined with high-temperature heat-treatment technology. The Co9S8/CoS homologous heterojunction successfully overcomes the inherent drawback of Co9S8 and possesses an ultrafast charging/discharging process, outstanding reversible specific capacity, and remarkable rate capability. A systematic study reveals that vanadium nitride is a key trigger for forming Co9S8/CoS heterojunction. When used as anode materials for sodium-ion batteries, it reaches a high specific capacity of 353.0 mAh/g at a current density of 10 A/g (615.8 mAh/g at a current density of 0.05 A/g) due to the presence of heterointerface. Theoretical calculations show that the construction of the heterostructure enhances the sodium-ion storage capacity and storage kinetics compared with pristine Co9S8. This discovery opens an interesting strategy for constructing homogeneous heterojunctions and broadens the horizons for designing energy storage and conversion materials.

Strain engineering of Bi2S3 microspheres via organic intercalation enabled high performance sodium storage

Conversion or alloying-type layered metal chalcogenides, which hold great promise as anodes for sodium storage, encounter a significant challenge of volume expansion due to the accumulation of inner strain during the charge–discharge process. This issue leads to severe stress concentration and necessitates urgent attention in terms of dispersing the distribution of inner strain through advanced strain engineering techniques. In this study, we have successfully fabricated Bi2S3-TTAB microspheres composed of Bi2S3 nanorods intercalated with tetradecyltrimethylammonium bromide (TTAB). By periodically inserting the soft TTAB into the interlayer of Bi2S3, we effectively isolate and confine the Bi2S3 layers while simultaneously expanding the interlamellar spacing. This innovative approach disperses and alleviates the inner strain of Bi2S3 at an atomic level, thereby ensuring electrode stability. As a competitive conversion-alloying-type anode for sodium-ion batteries, the Bi2S3-TTAB microspheres demonstrate remarkable performance in terms of high rate capacities and cycle stability (208.4 mAh g−1 at 15 A g−1; 4910 cycles at 10 A g−1 with 87.8 % capacity retention). This exceptional Na-ion storage capability enables the utilization of Bi2S3-TTAB combined with active carbon as an advanced sodium ion capacitor that demonstrates impressive energy and power densities (144.0 Wh kg−1 and 5.0 kW kg−1).

Liquid metal in prohibiting polysulfides shuttling in metal sulfides anode for sodium-ion batteries

Metal sulfides are a class of promising anode materials for sodium-ion batteries (SIBs) owing to their high theoretical specific capacity. Nevertheless, the reactant products (polysulfides) could dissolve into electrolyte, shuttle across separator, and react with sodium anode, leading to severe capacity loss and safety concerns. Herein, for the first time, gallium (Ga)-based liquid metal (LM) alloy is incorporated with MoS2 nanosheets to work as an anode in SIBs. The electron-rich, ultrahigh electrical conductivity, and self-healing properties of LM endow the heterostructured MoS2-LM with highly improved conductivity and electrode integrity. Moreover, LM is demonstrated to have excellent capability for the adsorption of polysulfides (e.g., Na2S, Na2S6, and S8) and subsequent catalytic conversion of Na2S. Consequently, the MoS2-LM electrode exhibits superior ion diffusion kinetics and long cycling performance in SIBs and even in lithium/potassium-ion battery (LIB/PIB) systems, far better than those electrodes with conventional binders (polyvinylidene difluoride (PVDF) and sodium carboxymethyl cellulose (CMC). This work provides a unique material design concept based on Ga-based liquid metal alloy for metal sulfide anodes in rechargeable battery systems and beyond.

Sandwiched ReS2 nanocables with dual carbon coating for efficient K+/Na+ storage performance

In this work, the nanocables of few-layered ReS2 nanosheets sandwiched between carbon nanotubes (CNTs) and nitrogen-doped amorphous carbon (NC) coating (i.e., CNT@ReS2@NC) are synthesized as high-performance anodes of both potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs). The CNT@ReS2@NC nanocables with dual carbon modifications have the several advantages for efficient K+/Na+ storage. The few-layered ReS2 nanosheets with a wide interlayer spacing of 0.64 nm contribute to accelerated reaction kinetics for fast K+/Na+ intercalation/extraction. The carbon nanotube skeleton with a hollow interior can effectively relieve the volume change and serve as a robust conductive network to boost structural stability. The NC layer provides rich defects as active sites and suppresses the shuttle effect of polysulfides produced in discharge/charge processes. Consequently, the CNT@ReS2@NC nanocables possess outstanding electrochemical performance in both PIBs and SIBs owing to the synergistic effect from the different components. A long cycling lifespan of 3500 cycles with a maintained discharge capacity of 125 mAh/g is achieved for CNT@ReS2@NC at 1 A/g in PIBs. In SIBs, it can keep a high capacity of 202 mAh/g over 3000 cycles at 5 A/g. Moreover, the CNT@ReS2@NC||Na3V2(PO4)3 full cell can exhibit remarkable cycling performance, yielding a low capacity decay rate of 0.019 % per cycle over 1000 cycles at 2C.

Constructing hierarchical MoS2/WS2 heterostructures in dual carbon layer for enhanced sodium ions batteries performance

The escalating global demand for clean energy has spurred substantial interest in sodium-ion batteries (SIBs) as a promising solution for large-scale energy storage systems. However, the insufficient reaction kinetics and considerable volume changes inherent to anode materials present significant hurdles to enhancing the electrochemical performance of SIBs. In this study, hierarchical MoS2/WS2 heterostructures were constructed into dual carbon layers (HC@MoS2/WS2@NC) and assessed their suitability as anodes for SIBs. The internal hard carbon core (HC) and outer nitrogen-doped carbon shell (NC) effectively anchor MoS2/WS2, thereby significantly improving its structural stability. Moreover, the conductive carbon components expedite electron transport during charge–discharge processes. Critically, the intelligently engineered interface between MoS2 and WS2 modulates the interfacial energy barrier and electric field distribution, promoting faster ion transport rates. Capitalizing on these advantageous features, the HC@MoS2/WS2@NC nanocomposite exhibits outstanding electrochemical performance when utilized as an anode in SIBs. Specifically, it delivers a high capacity of 415 mAh/g at a current density of 0.2 A/g after 100 cycles. At a larger current density of 2 A/g, it maintains a commendable capacity of 333 mAh/g even after 1000 cycles. Additionally, when integrated into a full battery configuration with a Na3V2(PO4)3 cathode, the Na3V2(PO4)3//HC@MoS2/WS2@NC full cell delivers a high capacity of 120 mAh/g after 300 cycles at 1 A/g. This work emphasizes the substantial improvement in battery performance that can be attained through the implementation of dual carbon confinement, offering a constructive approach to guide the design and development of next-generation anode materials for SIBs.

Mechanical Activation of Graphite for Na-Ion Battery Anodes: Unexpected Reversible Reaction on Solid Electrolyte Interphase via X-Ray Analysis.

Although sodium-ion batteries (SIBs) offer promising low-cost alternatives to lithium-ion batteries (LIBs), several challenges need to be overcome for their widespread adoption. A primary concern is the optimization of carbon anodes. Graphite, vital to the commercial viability of LIBs, has a limited capacity for sodium ions. Numerous alternatives to graphite are explored, particularly focusing on disordered carbons, including hard carbon. However, compared with graphite, most of these materials underperform in LIBs. Furthermore, the reaction mechanism between carbon and sodium ions remains ambiguous owing to the structural diversity of disordered carbon. A straightforward mechanical approach is introduced to enhance the sodium ion storage capacity of graphite, supported by comprehensive analytical techniques. Mechanically activated graphite delivers a notable reversible capacity of 290.5 mAh·g-1 at a current density of 10 mA·g-1. Moreover, it maintains a capacity of 157.7 mAh·g-1 even at a current density of 1 A·g-1, benefiting from the defect-rich structure achieved by mechanical activation. Soft X-ray analysis revealed that this defect-rich carbon employs a sodium-ion storage mechanism distinct from that of hard carbon. This leads to an unexpected reversible reaction on the solid electrolyte surface. These insights pave the way for innovative design approaches for carbon electrodes in SIB anodes.

Revealing Na+‐coordination Induced Failure Mechanism of Metal Sulfide Anode for Sodium Ion Batteries

Metal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium‐ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+‐coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo‐oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in‐depth perception of failure mechanism and inspiration for realizing advanced conversion‐type anode.

Revealing Na+-coordination Induced Failure Mechanism of Metal Sulfide Anode for Sodium Ion Batteries.

Metal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium-ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+-coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo-oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in-depth perception of failure mechanism and inspiration for realizing advanced conversion-type anode.

Coal-based hard carbon anode for high-performance sodium ion batteries via coal-based graphene oxide as a multi-functional binder

Coal-based hard carbon for sodium ion batteries (SIBs) was successfully prepared using Shenfu bituminous coal (SFC) by one-step pyrolysis method. In the present work, we reported a novel method to fabricate carbon electrodes for SIBs from coal-based hard carbon with coal-based graphene oxide (CGO) as a multi-functional conductive binder to realize dual functional utilization of coal. As compared to traditional binder (CMC), electrodes with the CGO binder exhibits significantly increased reversible capacity and rate capability. This work provides a facile method for coal-based carbon materials used in SIBs.

One-Step Construction of Closed Pores Enabling High Plateau Capacity Hard Carbon Anodes for Sodium-Ion Batteries: Closed-Pore Formation and Energy Storage Mechanisms.

Closed pores play a crucial role in improving the low-voltage (<0.1 V) plateau capacity of hard carbon anodes for sodium-ion batteries (SIBs). However, the lack of simple and effective closed-pore construction strategies, as well as the unclear closed-pore formation mechanism, has severely hindered the development of high plateau capacity hard carbon anodes. Herein, we present an effective closed-pore construction strategy by one-step pyrolysis of zinc gluconate (ZG) and elucidate the corresponding mechanism of closed-pore formation. The closed-pore formation mechanism during the pyrolysis of ZG mainly involves (i) the precipitation of ZnO nanoparticles and the ZnO etching on carbon under 1100 °C to generate open pores of 0.45-4 nm and (ii) the development of graphitic domains and the shrinkage of the partial open pores at 1100-1500 °C to convert the open pores to closed pores. Benefiting from the considerable closed-pore content and suitable microstructure, the optimized hard carbon achieves an ultrahigh reversible specific capacity of 481.5 mA h g-1 and an extraordinary plateau capacity of 389 mA h g-1 for use as the anode of SIBs. Additionally, some in situ and ex situ characterizations demonstrate that the high-voltage slope capacity and the low-voltage plateau capacity stem from the adsorption of Na+ at the defect sites and Na-cluster formation in closed pores, respectively.