Anode For Sodium-ion Batteries Research Articles

Amorphous Fe2O3 Anchored on N-Doped Graphene with Internal Micro-Channels as an Active and Durable Anode for Sodium-Ion Batteries.

The reduced graphene oxide (rGO) exhibits outstanding electrical conductivity and a high specific surface area, making it a promising material for various applications. Fe2O3 is highly desirable due to its significant theoretical capacity and cost-effectiveness, high abundance, and environmental friendliness. However, the performance of these r-GO/Fe2O3 composite electrodes still needs to be further improved, especially in terms of cycle stability. The composite of Fe2O3 anchored on N-doped graphene with inside micro-channels (Fe2O3@N-GIMC) was used to be efficiently prepared. Because the inside channels can furnish extra transmission pathways and absorption websites and the interconnected structure can efficaciously forestall pulverization and aggregation of electrode materials. In addition, N doping is also beneficial to improve its electrochemical performance. Thus, it demonstrates exceptional sodium storage characteristics, including notable electrochemical activity, impressive initial Coulombic efficiency, and favorable rate performance. The optimized Fe2O3@N-GIMC indicates outstanding discharge capacity (573.5 mAh g-1 at 1 A g-1), significant rate performance (333.6 mAh g-1 at 8 A g-1), and stable long-term cycle durability (308.9 mAh g-1 after 1000 cycles at 1 A g-1, 200.8 mAh g-1 after 4000 cycles at 1 A g-1) as a sodium-ion battery anode. This presents a new approach for preparing graphene-based high-functional composites and lays a stable basis for further expanding its application field.

Coupling the fast electron transportation of cobalt diselenide-based anode via cationic modulation for high rate Na+ storage

The sodium-ion batteries (SIBs), as compelling candidate for partially replacing lithium-ion batteries (LIBs) in relevant application scenarios, is gaining increasing attention. The development of high-rate performance anode materials for sodium-ion batteries is exceptionally crucial. Here, a ZIF (zeolitic imidazolate framework) compound targeting bimetallic cations has applied through a pyrolysis-induced in-situ selenization strategy. This resulted in a nitrogen-doped porous carbon-encapsulated Fe-ion-modified CoSe2 material with a rhombic dodecahedron morphology (Fe-CoSe2@NC). The architecture not only effectively alleviates the bulk stress induced by the insertion/extraction of sodium ions, but also enhances the migration and transport of electrons/ions. Additionally, Fe doping enhances the material's conductivity and expedites reaction kinetics. Consequently, the Fe-CoSe2@NC exhibits outstanding rate performance and cycling stability (362.54 mAh g-1 after 1000 cycles at a current density of 10.0 A g-1) when utilized as an anode for SIBs in a coin-type half-cell. The Fe-CoSe2@NC also delivers a high initial coulombic efficiency (ICE) of 70.14%. This is substantiated by diffusion analysis and in-situ electrochemical impedance spectroscopy (EIS) characterization. The charging and discharging mechanisms of Fe-CoSe2@NC were verified through XRD and TEM characterizations during the electrochemical processes. When coupled with Na3V2(PO4)3 as the cathode material to form a full cell, the Fe-CoSe2@NC// Na3V2(PO4)3 battery system achieves a high energy density of 112.05 Wh kg-1. In this study, the successful construction of a transition metal selenide anode material for SIBs characterized by a stable structure and facilitation of rapid ion migration was demonstrated.

Oxygen-driven closing pore formation in coal-based hard carbon for low-voltage rapid sodium storage

The coal-derived hard carbon is considered a promising anode material for sodium-ion batteries (SIBs) due to its ample resources, low cost, and unique pore structure. However, the ordered carbon microstructure of this material leads to inferior sodium storage capacity and low initial Coulombic efficiency (ICE). Herein, we propose a strategy to inhibit over-graphitization and promote the formation of closed pores during subsequent carbonation processes through oxygen-driven carbon sheets development. The formation mechanism of closed pores in coal-based hard carbon has been systematically established, and its contribution to the capacity of the low-voltage plateau in hard carbon anode for SIBs has been explained. In-situ characterizations demonstrate that the presence of abundant closed pores and moderate graphitization provides sufficient active sites for Na+ ion pore-filling. The closed pore structure ensured the realization of a high plateau capacity, resulting in a high reversible capacity of 303.1 mA h g−1, which was significantly higher than that of the open-pore dominant carbon (161.1 mA h g−1). This study offers innovative perspectives on designing high-performance carbon anodes with closed porosity, utilizing cost-effective and highly aromatic precursors.

Pseudocapacitive contribution in sulfur-doped porous carbon nanosheets enables high-performance sodium-ion storage

Sulfur-doped carbon materials have sparked considerable attention as the anodes for sodium-ion batteries (SIBs) due to their relatively high reversible specific capacity and excellent pseudocapacitive effect. However, the content of sulfur dopants in carbon materials is usually limited and an efficient doping strategy is urgently imperative to date. Herein, a space-confined doping strategy is proposed to fabricate porous carbon nanosheets with high sulfur dopant content by using low-cost pitch as a precursor with the help of sodium thiosulfate (Na2S2O3). The thermostable nano-MgO used in this system can occupy the specific space during pitch decomposition to induce the formation of hierarchical carbon nanosheets. Interestingly, such a space-confinement effect of nano-MgO is able to enlarge the accessible contact area of reactants and inhibit the loss of sulfur from Na2S2O3, thus significantly increasing sulfur dopant content within carbon frameworks. The optimized sulfur-doped carbon nanosheets (S-PCNs-2) with a high sulfur content of about 20.56 wt% as anode for SIBs delivers an ultrahigh pseudocapacitive contribution of 92.55 % at 5 mV s−1 and thus enable a desirable specific capacity of 428.6 mAh g−1 at 0.1 A g−1 with a high initial Coulombic efficiency of 84.9 % and superior rate performance of 380.6 mAh g−1 at 5 A g−1. Furthermore, a long cycling lifespan with a capacity retention of 88 % after 1000 charge/discharge cycles can be achieved for the S-PCNs-2 anode. This work provides a simple yet efficient doping approach to fabricate carbon anodes with high heteroatom contents for SIBs.

Hybrid catalyst‐assisted synthesis of multifunctional carbon derived from Camellia shell for high‐performance sodium‐ion batteries and sodium‐ion hybrid capacitors

AbstractBiomass‐derived carbon as energy storage materials have gradually attracted widespread attention due to their low cost, sustainability, and inherent structural advantages. Herein, hard carbon (H‐1200) and porous carbon (PC‐800) for sodium‐ion batteries (SIBs), sodium‐ion capacitors (SICs) half cells and sodium‐ion hybrid capacitors (SIHCs) have been synthesized from the same biomass precursor of Camellia shells through different treatments. H‐1200 synthesized by directly high‐temperature carbonization possesses a rational graphitic layer structure and plentiful heteroatoms. When applied as anode for SIBs, it exhibits a reversible capacity of 365.5 mAh g–1 at 25 mA g–1 and capacity retention 89.0% after 400 cycles at 200 mA g–1. Additionally, PC‐800 prepared by catalytic carbonization of K2C2O4/CaC2O4 hybrid catalyst has a sophisticated porous structure and a high surface area of 2186.9 m2 g–1. When employed as a cathode for SICs, it delivers a maximum capacity 104.2 mAh g–1 at 100 mA g–1 and 35.0 mAh g–1 at 5 A g–1. Furthermore, the all carbon assembled SIHC (H‐1200||PC‐800) using H‐1200 as anode and PC‐800 as cathode, features a broad output voltage range (0.01 ~ 4.1 V), high energy density of 161.5 Wh kg–1, power density of 12896.1 W kg–1, and superior capacity retention of 90.32% after 10000 cycles at 10 A g–1. This research result provide a new horizon for constructing low‐cost and large‐scale production of biomass derived carbon for energy storage materials.

Hydrothermally Assisted Conversion of Switchgrass into Hard Carbon as Anode Materials for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are emerging as a viable alternative to lithium-ion batteries, reducing the reliance on scarce transition metals. Converting agricultural biomass into SIB anodes can remarkably enhance sustainability in both the agriculture and battery industries. However, the complex and costly synthesis and unsatisfactory electrochemical performance of biomass-derived hard carbon have hindered its further development. Herein, we employed a hydrothermally assisted carbonization process that converts switchgrass to battery-grade hard carbon capable of efficient Na-ion storage. The hydrothermal pretreatment effectively removed hemicellulose and impurities (e.g., lipids and ashes), creating thermally stable precursors suitable to produce hard carbon via carbonization. The elimination of hemicellulose and impurities contributes to a reduced surface area and lower oxygen content. With the modifications, the initial Coulombic efficiency (ICE) and cycling stability are improved concurrently. The optimized hard carbon showcased a high reversible specific capacity of 313.4 mAh g-1 at 100 mA g-1, a commendable ICE of 84.8%, and excellent cycling stability with a capacity retention of 308.4 mAh g-1 after 100 cycles. In short, this research introduces a cost-effective method for producing anode materials for SIBs and highlights a sustainable pathway for biomass utilization, underscoring mutual benefits for the energy and agricultural sectors.

Low-Surface-Area Nitrogen-Doped Carbon Submicrospheres as High-Coulombic-Efficiency and High-Capacity Anodes for Practical Sodium-Ion Batteries.

Nitrogen-doped carbon submicrospheres (NCSMs) are synthesized via an efficient and environmentally friendly one-pot polymerization reaction at room temperature, in which dopamine hydrochloride serves as the source for both carbon and nitrogen. Through leverage of its distinctive structure characterized by minimal surface area, fewer oxygen-containing functional groups, and a heightened presence of active nitrogen-doping sites, the synthesized NCSM showcases a noteworthy initial Coulombic efficiency (ICE) of 84.8%, a remarkable sodium storage capacity of 384 mAh g-1, an impressive rate capability of 215 mAh g-1 at 10 A g-1, and a superior cyclic performance, maintaining 83.0% of its capacity after 2000 cycles. The submicron spherical structure, with its limited surface area and scarce oxygen-containing moieties, effectively curtails the irreversible sodium-ion loss in solid-electrolyte interphase film formation, resulting in heightened ICE. The abundant nitrogen doping can expand carbon-layer spacing as well as improve the electron/ion-transport dynamics, guaranteeing a high sodium storage capacity and a strong rate capability. Crucially, the synthesis method presented here is straightforward, effective, and amenable to scaling, offering a novel avenue for the commercialization of sodium-ion batteries.

Pre‐Doping of Dual‐Functional Sodium to Weaken Fe─S Bond and Stabilize Interfacial Chemistry for High‐Rate Reversible Sodium Storage

AbstractFerrous sulfides with the high theoretic capacity are the promising anode for sodium ion batteries. However, capacity fading and inferior rate capability still hinder their practical application. In this work, Na‐doped Fe7S8 microrods with cationic vacancies and weakened Fe─S bond are constructed through a facile and scalable sulfurized route. The experimental results combined with theoretical analysis thoroughly reveal the generation of Fe vacancies and weakened Fe─S bond strength induced by sodium doping, which modulates the energy band structure of Na‐doped Fe7S8, provides more active sites, and accelerates the sodiation/desodiation reaction kinetics, simultaneously. Moreover, the pre‐doping sodium delivers a strong guiding effect on the formation of thin and stable solid electrolyte interface films. As the result, the optimal sample exhibits the excellent sodium storage performance, including the high and stable reversible capacity (674 mAh g−1 after 200 cycles at 0.5 A g−1 and 503 mAh g−1 after 1500 cycles at 10 A g−1), superior rate capability, and increased initial coulombic efficiency. Furthermore, the full cell paired with commercial Na3V2(PO4)3 also displays the outstanding cyclic stability with 95.9% capacity retention at 0.5 A g−1 after 100 cycles.

Binary Co3S4/SnS chalcogenide composites anchored on graphene oxide and carbon nanotubes as anodes for Na-ion batteries

Hetero-architectures are smart for modern energy storage appliances owing to fast charge transportation. However, the smooth and rational assembly with adequate Na+ storage kinetics so far is a significant challenge. Herein, transition-bimetallic sulfides hetero-structured Co3S4/SnS (CTS) and its composites implanted in reduced graphene oxide (CTS.rGO) and carbon nanotubes (CTS.CNTs) have been synthesized and employed as anodes for sodium-ion batteries. The use of highly conductive nature of carbon frames benefits the stability and conductivity of the bimetallic sulfides CTS composites. As a result, the CTS.CNTs delivered a charge capacity 298 mAh/g, whereas CTS.rGO and bare CTS exhibited 229 and 76 mAh/g after 200cycles at 0.05C. In addition, the CTS.CNTs and CTS.rGO displayed excellent rate performance at different rates (0.05C – 10.0C) and upon reversing the C-rate to 0.05C, CTS.CNTs fully restored the charge capacity 329 mAh/g while CTS.rGO restored to 293 mAh/g. The ultra-cyclic stability and improved rate performance enlightening the synergistic effect between CTS and carbon conducting agents. Moreover, the CTS.CNTs displayed the lowest charge transfer resistance (Rct = 604 Ω) as compared to CTS.rGO and bare CTS (Rct = 618 Ω, Rct = 642 Ω), indicating the rapid charge transport.

Regulating the “core-shell” microstructure of hard carbon through sodium hydroxide activation for achieving high-capacity SIBs anode

Pore structure engineering has been acknowledged as suitable approach to creating active sites and enhancing ion transport capabilities of hard carbon anodes. However, conventional porous carbon materials exhibit high BET and surface defects. Additionally, the sodium storage mechanism predominantly occurs in the slope region. This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries. In our work, we prepared a novel “core-shell” carbon framework (CNA1200). Introducing closed pores and carboxyl groups into coal-based carbon materials to enhance its sodium storage performance. The closed pore structure dominates in the “core” structure, which is attributed to the timely removal of sodium hydroxide (NaOH) to prevent further formation of active carbon structure. The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region. And the “shell” structure originates from coal tar pitch, it not only uniformly connects hard carbon particles together to improve cycling stability, but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region. CNA1200 has excellent electrochemical performance, it exhibits a specific capacity of 335.2 mAh g−1 at a current density of 20 mA g−1 with ICE = 51.53 %. In addition, CNA1200 has outstanding cycling stability with a capacity retention of 91.8 % even when cycling over 200 times. When CNA1200 is used as anode paired with Na3V2(PO4)3 cathode, it demonstrates a capacity of 109.54 mAh g−1 at 0.1 C and capacity retention of 94.64 % at 0.5 C. This work provides valuable methods for regulating the structure of sodium-ion battery (SIBs) anode and enhances the potential for commercialization.

Stable Structure and Fast Ion Diffusion: A Flexible MoO2@Carbon Hollow Nanofiber Film as a Binder-Free Anode for Sodium-Ion Batteries with Superior Kinetics and Excellent Rate Capability.

Designing innovative anode materials that exhibit excellent ion diffusion kinetics, enhanced structural stability, and superior electrical conductivity is imperative for advancing the rapid charge-discharge performance and widespread application of sodium-ion batteries. Hollow-structured materials have received significant attention in electrode design due to their rapid ion diffusion kinetics. Building upon this, we present a high-performance, free-standing MoO2@hollow carbon nanofiber (MoO2@HCNF) electrode, fabricated through facile coaxial electrospinning and subsequent heat treatment. In comparison to MoO2@carbon nanofibers (MoO2@CNFs), the MoO2@HCNF electrode demonstrates superior rate capability, attributed to its larger specific surface area, its higher pseudocapacitance contribution, and the enhanced diffusion kinetics of sodium ions. The discharge capacities of the MoO2@HCNF (MoO2@CNF) electrode at current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g-1 are 195.55 (155.49), 180.98 (135.20), 163.81 (109.71), 144.05 (90.46), 121.16 (71.21) and 88.90 (44.68) mAh g-1, respectively. Additionally, the diffusion coefficients of sodium ions in the MoO2@HCNFs are 8.74 × 10-12 to 1.37 × 10-12 cm2 s-1, which surpass those of the MoO2@CNFs (6.49 × 10-12 to 9.30 × 10-13 cm2 s-1) during the discharging process. In addition, these prepared electrode materials exhibit outstanding flexibility, which is crucial to the power storage industry and smart wearable devices.

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.

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.

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).

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.

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.

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.