Potential In Sodium-ion Batteries Research Articles

In-situ construction of heterogeneous structure by crystal phase evolution to improve the sodium storage performance of NiCo2O4

Transition metal oxides (TMCs) have great potential in sodium ion batteries (SIBs) due to their significantly higher capacity and lower cost. However, during the cycle, huge volume changes often lead to structural damage, which is a key factor in the rapid decay of capacity. In this paper, a heterogeneous structure was constructed in situ by introducing sulfur element to induce the decomposition of NiCo2O4 crystal phase. The rich heterogeneous interface has enhanced redox reaction kinetics and charge transport properties. For high-capacity conversion anode materials, cross-linked grain boundaries can effectively disperse the local stress caused by volume changes and alleviate the inevitable electrode crushing, thus ensuring the stability of the electrode during long-term cycling. The NiCo2O4/NiCo2S4/CoO/ NiO heterogeneous structure (NCOS-350) exhibits enhanced cycling and rate performance (350 mAh g−1 at 0.5 A g −1 after 100 cycles and 270 mAh g −1 at 5 A g −1) when used as the anode for sodium ion batteries. In addition, it is proved that NCOS-350 has smaller volume change and better structural stability than NiCo2O4 by scanning electron microscopy and other characterizations.

Simple synthesis of MoSSe heterojunction nanosphere for ultrafast kinetics and high-performance sodium-ion battery

Sodium-ion batteries (SIBs) are expected to be an effective solution for energy storage to be applied to various electronic devices due to their cost-effective performance and similar working principles to lithium-ion batteries (LIBs). However, the electrochemical performances of SIBs are currently hindered by the challenges posed by the large size and slow diffusion kinetics of Na+. Chalcogenide heterojunctions have great potential in SIBs anode materials. Therefore, this study presents a MoSSe heterojunction with a three-dimensional flower-like spherical structure. This heterojunction exhibits enhanced Na+ adsorption and storage capabilities, a high rate of Na+ diffusion, and improved structural stability. These excellent structures and characteristics are highly beneficial for Na+ storage, demonstrating superior stability, and large capacity. Consequently, the designed MoSSe exhibits long cycling stability at 5.0 A g−1 (195.2 mAh g−1 after 2000 cycles) and exceptional capacity at 0.1 A g−1 (413.1 mAh g−1). This work demonstrates that heterojunctions can become excellent electrode materials for SIBs to achieve stable sodium energy storage.

Regulating Pseudo-Graphitic Domain and Closed Pores to Facilitate Plateau Sodium Storage Capacity and Kinetics for Hard Carbon.

Hard carbon anode demonstrates exceptional potential in sodium-ion batteries due to their cost-effectivenss and superior plateau capacity. However, the proximity of the plateau capacity to the cut-off voltage of battery operation and the premature cut-off voltage response caused by polarization at high rates greatly limit the exploitation of plateau capacities, raising big concerns about inferior rate performance of high-plateau-capacity hard carbon. In this work, a facile pre-oxidation strategy is proposed for fabricating lignin-derived hard carbon. Both high-plateau capacity and sodiation kinetics are significantly enhanced due to the introduction of expanded pseudo-graphitic domains and high-speed closed pores. Impressively, the optimized hard carbon exhibits an increased reversible capacity from 252.1 to 302.0 mAh g-1, alongside superior rate performance (174.7 mAh g-1 at 5 C) and stable cyclability over 500 cycles. This study paves a low-cost and effective pathway to modulate the microstructure of biomass-derived hard carbon materials for facilitating plateau sodium storage kinetics.

Biomimetic-Mineralization-Assisted Self-Activation Creates a Delicate Porous Structure in Carbon Material for High-Rate Sodium Storage.

Porous carbons have shown their potential in sodium-ion batteries (SIBs), but the undesirable initial Coulombic efficiency (ICE) and rate capability hinder their practical application. Herein, learning from nature, we report an efficient method for fabricating a carbon framework (CK) with delicate porous structural regulation by biomimetic mineralization-assisted self-activation. The abundant pores and defects of the CK anode can improve the ICE and rate performance of SIBs in ether-based electrolytes, whereas they are confined in carbonate ester-based electrolytes. Notably, ether-based electrolytes enable CK anode to possess excellent ICE (82.9%) and high-rate capability (111.2 mAh g-1 at 50 A g-1). Even after 5500 cycles at a large current density of 10 A g-1, the capacity retention can still be maintained at 73.1%. More importantly, the full cell consisting of the CK anode and Na3V2(PO4)3 cathode delivers a high energy density of 204.4 Wh kg-1, with a power density of 2828.2 W kg-1. Such outstanding performance of the CK anode is attributed to (1) hierarchical pores, oxygen doping, and defects that pave the way for the transportation and storage of Na+, further enhancing ICE; (2) a high-proportion NaF-based solid-electrolyte-interphase (SEI) layer that facilitates Na+ storage kinetics in ether-based electrolytes; and (3) ether-based electrolytes that determine Na+ storage kinetics further to dominate the performance of SIBs. These results provide compelling evidence for the promising potential of our synthetic strategy in the development of carbon-based materials and ether-based electrolytes for electrochemical energy storage.

Anion-Induced Uniform and Robust Cathode-Electrolyte Interphase for Layered Metal Oxide Cathodes of Sodium Ion Batteries.

Layer metal oxides demonstrate great commercial application potential in sodium-ion batteries, while their commercialization is extremely hampered by the unsatisfactory cycling performance caused by the irreversible phase transition and interfacial side reaction. Herein, trimethoxymethylsilane (TMSI) is introduced into electrolytes to construct an advanced cathode/electrolyte interphase by tuning the solvation structure of anions. It is found that due to the stronger interaction between ClO4- and TMSI than that of ClO4- and PC/FEC, the ClO4--TMSI complexes tend to accumulate on the surface of the cathode during the charging process, leading to the formation of a stable cathode/electrolyte interface (CEI). In addition, the Si species with excellent electronic insulation ability are distributed in the TMSI-derived CEI film, which is conducive to inhibiting the continuous side reaction of solvents and the growth of the CEI film. As a result, under a current density of 250 mA g-1, the capacity retention of the NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode after 200 cycles in the TMSI-modified electrolyte is 74.4% in comparison to 51.5% of the bare electrolyte (1 M NaClO4/PC/5% FEC). Moreover, the NFM cathode shows better kinetics, with the specific discharge capacity increasing from 22 to 67 mAh g-1 at 300 mA g-1. It also demonstrates greatly improved rate capability, cycling stability, and Coulombic efficiency under various operating conditions, including high temperature (55 °C) and high cutoff voltage (2.0-4.3 V vs Na+/Na).

A high rate and stability cathode material for half/full sodium-ion batteries: Nb-substituted NaNi1/3Mn1/3−xFe1/3NbxO2 layered oxides

O3 layered oxide cathode materials have infinite development potential in sodium ion batteries (SIBs), but complex phase transitions usually result in poor rate capacity. In this study, NaNi1/3Mn1/3−xFe1/3NbxO2 (NFM-Nb x, x = 0, 0.01, 0.02) precursor were synthesized through ball-milling spray drying method. The structure morphology characterization confirmed that Nb was successfully doped into the material and replaced part of Mn in the transition metal. The chemical valence analysis shows that Nb doping promoted the reduction of Mn4+ to Mn3+, and the increase of Mn3+ improved the ionic conductivity. NFM-Nb 0.01 significantly improved long cycle stability and rate capacity, the capacity of NFM-Nb 0.01 at 1 C and 5 C were 125.4 and 115.5 mAh g−1, respectively, and the corresponding cycle retention rate maintained 83. 81% and 83.12%. NFM-Nb 0.01 has a 25.06% higher capacity retention rate than NFM after 100 cycles at 1 C in the voltage range 2–4.3 V. For full-cell, NFM-Nb 0.01//HC delivered the capacity of 79.4 mAh g−1 at 10 C after 200 cycles and kept 71.16% cycle retention. The results of ex-situ XRD further investigated Nb-substitution enhanced the structure recoverability of cathode materials. The failure analysis result showed that Nb substitution is beneficial to stabilize the layered structure of materials, improve the cycling performance under high voltage.

Long-Cycling-Life Sodium-Ion Battery Using Binary Metal Sulfide Hybrid Nanocages as Anode.

Due to the relatively high capacity and lower cost, transition metal sulfides (TMS) as anode show promising potential in sodium-ion batteries (SIBs). Herein, a binary metal sulfide hybrid consisting of carbon encapsulated CoS/Cu2 S nanocages (CoS/Cu2 S@C-NC) is constructed. The interlocked hetero-architecture filled with conductive carbon accelerates the Na+ /e- transfer, thus leading to improved electrochemical kinetics. Also the protective carbon layer can provide better volume accommondation upon charging/discharging. As a result, the battery with CoS/Cu2 S@C-NC as anode displays a high capacity of 435.3mAhg-1 after 1000 cycles at 2.0Ag-1 (≈3.4C). Under a higher rate of 10.0Ag-1 (≈17C), a capacity of as high as 347.2mAhg-1 is still remained after long 2300 cycles. The capacity decay per cycle is only 0.017%. The battery also exhibits a better temperature tolerance at 50 and -5°C. A low internal impedance analyzed by X-ray diffraction patterns and galvanostatic intermittent titration technique, narrow band gap, and high density of states obtained by first-principle calculations of the binary sulfides, ensure the rapid Na+ /e- transport. The long-cycling-life SIB using binary metal sulfide hybrid nanocages as anode shows promising applications in versatile electronic devices.

Boosted sodium storage of GeS2/GeO2/ZnS composite via heterostructure engineering

Transition metal dichalcogenides exhibit tremendous potential for sodium ion batteries (SIBs), owing to the outstanding specific capacity and aboundant reserves. However, the large ionic radius of sodium and poor conductivity often result in the fast decaying performance and inferior reaction kinetics. Herein, the GeS2/GeO2/ZnS@rGO (GGZ/C) ternary metal-based composite is fabricated as an anode material for SIBs. Notably, the GGZ/C composite is derived from the phase transformation of Zn2GeO4 precursor, which is beneficial for the heterostructure engineering. In this hierarchical structure, the metal phases ZnS and GeO2 are used to form the heterogeneous framework, while graphene is applied to build a conductive network and anchor the host nanoparticles. Therefore, the great Na+ diffusion channels are achieved by the rational design of the huge exquisite interfaces among the heterogeneous mixed phases. Notably, it can almost completely relieve the volume expansion and restrain the internal stress of GGZ/C composite, providing the excellent structural tolerance. As expected, the GGZ/C composite exhibits excellent rate capability, with an impressive reversible capacity of 548 mAh g−1 at a high rate of 5.0 A g−1. Meanwhile, the GGZ/C also displays outstanding cycling performance with a specific capacity of 519 mAh g−1 after 650 cycles at high rate of 5.0 A g−1. This strategy offers the inspiration for rational heterostructure engineering for the energy storage materials with excellent reversible capacity and large volume variation.

Two-dimensional silicether: A promising anode material for sodium-ion battery

Sodium-ion batteries (SIBs) are expected to replace lithium-ion batteries as the next generation of commercial secondary batteries. However, the large-scale commercial use is hindered by the lack of suitable anode materials. Based on first-principles calculations, we systematically investigate the electrochemical performance of 2D silicether as an anode material for SIBs. It could turn to the metallic state from semiconductor after being intercalated with a low Na concentration of 0.056. Owing to the special groove-like structure of silicether, Na atom crosses a low energy barrier of 0.40 eV along the armchair direction. The theoretical storage capacity (418 mA h/g), the average electron potential (2.22 V), and no significant volume expansion suggest that silicether has a great potential in SIBs. Moreover, bilayer silicether could preserve the performances of silicether monolayer, such as strong Na adsorption capability and fast ionic mobility. The above-mentioned appealing results make silicether a high-performance anode material for SIBs.

Designing Layered Na3Ni2SbO6 Cathodes with Hierarchical and Hollow Nanostructure for Sodium‐Ion Batteries

AbstractHoneycomb‐ordered Na3M2XO6 (M=Ni, Co, Cu; X=Sb, Bi, etc.) layered oxide cathodes have drawn significant attention by virtue of prominent voltage platform and high energy density in sodium‐ion batteries (SIBs). However, they usually suffer from inferior rate performance and cycling stability due to sluggish Na+ migration kinetics and low electronic conductivity. Designing layered cathodes with hierarchical nanostructure shows great potential in SIBs owing to enhanced charge transfer and reaction kinetics. Herein, layered Na3Ni2SbO6 nanofibers with hierarchical and porous‐structure were prepared through simple electrospinning and subsequent annealing procedure. This unique structure holds the merits of large active surface areas for easy access to the electrolyte, well‐guided paths for electrons/ions transfer, excellent buffering ability for deformation stress, and potential to maintain structural integrity over repetitious sodiation/desodiation process. Thus, compared with the Na3Ni2SbO6 synthesized by conventional sol‐gel approach, the Na3Ni2SbO6 nanofibers exhibit superior rate performance and capacity capability.

Constructing inverse opal antimony@carbon frameworks with multi-level porosity towards high performance sodium storage

Metal antimony (Sb) has excellent electrical conductivity and high theoretical capacity of sodium storage based on alloy reaction mechanism and possesses great application potential in sodium ion batteries (SIBs). However, serious material fracture and volume expansion during the alloy reaction greatly hinder its commercialization process. To overcome these issues, herein a construction method combining ordered silica template, viscous sol casting and high temperature gel reduction is proposed for fabricating ordered 3D antimony/carbon inverse opal framework (3D Sb/C). With the confining effect of the templates, active antimony nanoparticles are highly dispersed. After the etching process, macroporous inverse opal framework can be constructed. The following repeated oxidation and reduction process on active antimony modifies the surrounding microscopic environment, further forming a huge number of mesopores, and finally resulting in the formation of multi-level porous structure. The acquirement of the 3D Sb/C inverse opals realizes the multiple engineering modulations for SIB application, which is conducive to the exposure of active sites, the buffer of volume expansion, and the path of rapid ion diffusion/electron transfer. Benefiting from these structure advantages, the 3D Sb/C 250 inverse opals exhibit excellent sodium storage capacity (550.4 mAh g −1 at 0.1 A g −1 ) and cyclic stability (257.9 mAh g −1 after 200 cycles at 1 A g −1 ). • 3D antimony@carbon inverse opal framework (3D Sb/C) was constructed as SIB anode. • Silica template, sol casting and gel reduction are combined for 3D Sb/C construction. • Active antimony nanoparticles are highly dispersed in carbon inverse opal framework. • The repeated oxidation and reduction process results in multi-level porous structure. • 3D Sb/C with the novel porous structure exhibits excellent Na storage performances.

Advanced Anode Materials for Sodium-Ion Batteries: Confining Polyoxometalates in Flexible Metal-Organic Frameworks by the "Breathing Effect".

Polyoxometalates (POMs) have shown great potential in sodium-ion batteries (SIBs) due to their reversible multielectron redox property and high ionic conductivity. Currently, POM-based SIBs suffer from the irreversible trapping and sluggish transmission kinetics of Na+. Herein, a series of POMs/metal-organic frameworks (MOFs)/graphene oxide (GO) (MOFs = MIL-101, MIL-53, and MIL-88B; POM = [PMo12O40]3-, denoted as PMo12) composites are developed as SIB anode materials for the first time. Unlike MIL-101 with large pore structures, the pores in flexible MIL-53 and MIL-88B swell spontaneously upon the accommodation of PMo12. Particularly, the PMo12/MIL-88B/GO composites deliver an excellent specific capacity of 214.2 mAh g-1 for 600 cycles at 2.0 A g-1, with a high initial Coulombic efficiency (ICE) of 51.0%. The so-called "breathing effect" of flexible MOFs leads to the relatively tight confinement space for PMo12, which greatly modulates its electronic structure, affects the adsorption energy of Na+, and eventually reduces the trapping of sodium ions. Additionally, the straight and multidimensional channels in MIL-88B significantly accelerate ion diffusion, inducing favored energetic kinetics and thus generating high-rate performance.

Mn-doped Na4Fe3(PO4)2(P2O7) facilitating Na+ migration at low temperature as a high performance cathode material of sodium ion batteries

Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) is known as a cathode material with great potential for sodium ion batteries (SIBs) due to its thermodynamic stability, considerable theoretical capacity and small volume change. However, its inherent poor conductivity leads to low discharge capacity and poor cycle stability, which greatly limits its widespread and practical application. In this work, a Mn 2+ doped NFPP together with the graphene modification, is proposed. It is found that the optimal Na 4 Fe 2.7 Mn 0.3 (PO 4 ) 2 P 2 O 7 /rGO(Mn0.3-NFPP/rGO) can provide an initial discharge capacity of 131.5 mAh g −1 at 0.1C, (1C = 129mAh g −1 ) also an excellent rate performance (70.2 mAh g −1 at 50C) and good long cycle stability (97.2% capacity retention after 2000 cycles at 10C) can be obtained. Impressively, the as-prepared Mn0.3-NFPP/rGO also shows excellent low-temperature performance, at −20 °C, it demonstrates a discharge capacity of 85.3 mAh g −1 at 0.2C and good rate performance. Density functional theory (DFT) calculation shows that Mn 2+ doping reduces the Na + migration energy barrier, and also narrows the bandgap of the NFPP lattice, which is beneficial to improve the Na + diffusion kinetics and conductivity. In addition, the doping of Mn 2+ can further help to improve its structural stability during the long cycling process. • Mn-doped Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) together with graphene modification is proposed. • Mn 2+ doping reduces the Na + migration energy barrier. • Mn 2+ doping narrows the bandgap of Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ). • The Na + migration is facilitated by Mn 2+ doping, particularly at low temperature.

Advanced red phosphorus/carbon composites with practical application potential for sodium ion batteries

Although sodium ion batteries (SIBs) are one of the most promising battery technologies, their relatively low energy density impedes further development. This study presents the novel practical application potential of high-capacity red phosphorus (P) in full SIBs with reasonable energy density. Various optimization strategies are implemented systematically, which include the ball mill time, binders, conductive and electrolyte additives, and corresponding functional mechanisms are also conducted. In situ TEM and electrochemical characterization further indicate that the hybridization of hard carbon (HC) with desirable stability and phosphorus/carbon (PC) with large capacity is a preferred strategy to construct P-based full SIBs. The corresponding energy density is increased from 134 Wh Kg−1 (pure HC case) to 150 Wh Kg−1 (HC/PC case) through an electrochemical presodiation method. Notably, despite the various challenges faced by P anodes, the analysis conducted in this study is crucial for enabling the practical application of high-capacity phosphorus beyond laboratory research.

(Invited) Sodium Layered Oxides in the Spotlight: Current State-of-Art and Remaining Challenges

The development of new energy storage technologies is essential for the advancement of a society increasingly dependent on energy supplies. In this context, sodium-ion batteries (SIBs) have proven to be the key to revolutionizing the global energy market, especially for large-scale stationary energy storage and light electromobility [1]. However, the achievement of the full potential of SIBs technology remains a challenge and efforts should be focused on the design of more efficient high energy density and high cycle life sodium-based positive electrodes. In this scenario, sodium-based layered oxide cathodes with general formula NaxMO2 (M = transition metal/s) are an excellent choice due to their electrochemical performance, environmental friendliness and scalability [2,3]. Prof. Claude Delmas pioneered the study of the electrochemical intercalation processes of this family of compounds, being one of the first researchers to exploit their potential in SIBs. Although the virtues of this family of materials as cathodes are clear, there are also several drawbacks such as irreversible structural phase transitions, strong Na+-vacancy ordering tendencies or poor cyclability that should be addressed to ensure the optimum operation of this material in a commercial battery.One of the peculiarities of these cathode materials lies in the diverse structures that they can adopt, being the P2 and O3 structures the most interesting from the electrochemical point of view. P2-type phases present higher rate performance and capacity retention than O3-type phases. However, they are only stable with sodium contents ≤ 0.85, which translates into higher first irreversible capacity. In O3-type phases, on the other hand, it is possible to reach the fully sodiated stoichiometry, delivering thus higher capacities but at the expense of considerable retention nested in O3-P3 phase transitions, which alter the diffusion mechanism of Na+ ions giving rise to a large energy barrier that Na+ ions must overcome.This talk will present the main advances on the development of sodium layered oxide cathodes, as well as the most successful strategies for overcoming current challenges, such as doping with electrochemically active and inactive elements [4], surface coatings [5], the use of sacrificial salts [6] or the synergetic P2/O3 combination effect [7]. Finally, the anionic redox effect and the controversy in the explanation of the extra capacity observed in certain de-sodiated transition metal oxides will also be discussed. Goikolea, T. Rojo, et al. Adv. Energy Mater. 2020, 10, 2002055H. Han, T. Rojo, et al., Energy Environ. Sci. 2015, 8, 81–102Ortiz-Vitoriano, T. Rojo, et al., Energy Environ. Sci. 2017, 10, 1051–1074Gonzalo, T. Rojo, et al. Enegy Storage Mater. 2021, 34, 682–707Zarrabeitia, T. Rojo, et al. J. Mater. Chem. A, 2019, 7, 14169–14179J. Fernández-Ropero, D. Shanmukaraj et al. ACS Appl. Mater Interfaces, 2021, 13, 11814–11821Bianchini, T. Rojo, et al. J. Mater. Chem. A, 2018, 6, 3552–3559.

Microwave-assisted synthesis of self-assembled camellia-like CuS superstructure of ultra-thin nanosheets and exploration of its sodium ion storage properties

The major merit of this work is to use a facile microwave-assisted method to synthesize nanosheet-assembled camellia-like CuS material. When investigated as a novel anode for SIBs, the electrode exhibits an outstanding electrochemical performance. • A novel camellia-like CuS superstructure is first prepared by a microwave-assisted heating method. • Structural evolution is explained by the Ostwald ripening and oriented growth mechanism. • The CuS electrode shows excellent cycling stability and rate performance for SIBs. • The obtained nanosheet-assembled CuS anode delivers a large pseudocapacitive behavior. Layered copper sulfide (CuS) has immense commercial application potential in sodium-ion batteries (SIBs) due to its high capacity, diverse structures, and controllable synthetic methods. Despite these advantages, due to the large volume changes and soluble polysulfide intermediates based on the conversion reaction, it is a huge challenge for CuS electrodes to maintain high-rate performance and long-term cycle stability. Herein, a camellia-like CuS superstructure is designed and synthesized to improve cycling stability and rate performance. The cycling stability reflects in a stable capacity of 347.1 mAh g −1 can still be retained at 0.1 A g −1 after 100 cycles, and even after 1000 cycles at 5.0 A g −1 without decay. The excellent rate performance is embodied in the capacity of 352.4 and 255.7 mAh g −1 at 0.05 and 5.0 A g −1 , respectively. This work provides a feasible route to develop CuS anode material of SIBs with remarkable sodium storage performance.

Atomic Layer Deposition of Sodium Phosphorus Oxynitride: A Conformal Solid-State Sodium-Ion Conductor.

The development of novel materials that are compatible with nanostructured architectures is required to meet the demands of next-generation energy-storage technologies. Atomic layer deposition (ALD) allows for the precise synthesis of new materials that can conformally coat complex 3D structures. In this work, we demonstrate a thermal ALD process for sodium phosphorus oxynitride (NaPON), a thin-film solid-state electrolyte (SSE), for sodium-ion batteries (SIBs). NaPON is analogous to the commonly used lithium phosphorus oxynitride SSE in lithium-ion batteries. The ALD process produces a conformal film with a stoichiometry of Na4PO3N, corresponding to a sodium polyphosphazene structure. The electrochemical properties of NaPON are characterized to evaluate its potential in SIBs. The NaPON film exhibited a high ionic conductivity of 1.0 × 10-7 S/cm at 25 °C and up to 2.5 × 10-6 S/cm at 80 °C, with an activation energy of 0.53 eV. In addition, the ionic conductivity is comparable and even higher than the ionic conductivities of ALD-fabricated Li+ conductors. This promising result makes NaPON a viable SSE or passivation layer in solid-state SIBs.

3D hierarchical microspheres constructed by ultrathin MoS2-C nanosheets as high-performance anode material for sodium-ion batteries

MoS2/C composites are considered to have great application potential in sodium-ion batteries (SIBs). It is a challenging and meaningful subject that developing high-performance anode materials via combining MoS2 and carbon effectively to give free rein to their advantages in sodium ion storage. In this work, a novel MoS2-C material was designed by using cellulose nanocrystals (CNCs) as low-cost and green carbon source. 3D hierarchical microspheres (200–250 nm) constructed by ultrathin MoS2-C nanosheets were synthesized by synchronizing the pre-carbonization of CNCs with the formation of MoS2 in hydrothermal reaction and subsequent pyrolysis process. It is found that the ultrathin MoS2-C nanosheets were composed of CNCs-derived short-range ordered carbon and few-layered MoS2. Benefiting from the unique structure and robust combination of MoS2 and CNCs-derived carbon, the ultrathin MoS2-C nanosheets composite was proved to have excellent cycling stability and superior rate performance in sodium-ion half-cell test and have high first reversible specific capacity of 397.9 mAh/g in full-cell test. This work provides a significant and effective pathway to prepare MoS2-C materials with excellent electrochemical performance for the application in large-scale energy storage systems.

Constructing N-Doped porous carbon confined FeSb alloy nanocomposite with Fe-N-C coordination as a universal anode for advanced Na/K-ion batteries

Sb-based anodes have shown great potential in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) owing to their high theoretical capacities and applicable voltage platforms, but they usually suffer from severe volume change and sluggish ion diffusion kinetic. Herein, a novel N-doped three-dimension porous carbon network confined nanosized FeSb alloy composite (3D FeSb@NC) with a strong Fe-N-C bond is elaborately designed and fabricated, this unique structure sufficiently relieves the volume change of Sb during cycling, reduces the diffusion length for both ion/electrons, enhances the electronic conductivity, and provides abundant active sites for Na+/K+ storage. Moreover, the strong Fe-N-C bond can strengthen the interface adhesion between carbon matrix and alloy particle for sustaining structure integrity. The 3D FeSb@NC anodes delivers outstanding electrochemical performances in both SIBs and PIBs, in terms of ultralong cycling life (capacity retention of 85% after 750 cycles for SIBs and 80% after 1000 cycles for PIBs) and excellent rate capability (231 mAh g−1 at 5 A g−1 for SIBs and 119.7 mAh g−1 at 2 A g−1 for PIBs). The kinetic analysis of Na+/K+ storage reveal that the extrinsic pseudo-capacitive contribution accounts for the high rate performance. This work provides an effective strategy to develop nanocomposite anode with superior structural stability and durability for SIBs/PIBs.

Potential Applications of Heterostructures of TMDs with MXenes in Sodium-Ion and Na-O2 Batteries.

Na-ion batteries are viewed as the alternative to Li-ion batteries for similar electrochemical properties, while they always suffer from a low capacity. Na-O2 batteries are important due to their high energy density; however, they are usually limited by high overpotential. In this manuscript, 16 different heterostructures of TMDs with MXenes (bare and O-terminated case) are constructed and their potential in the application of sodium-ion batteries (SIBs) and Na-O2 batteries is explored. Among these structures, it is proved that only the heterostructures of VS2 with O-terminated MXenes could load five layers of Na+ ions, while the others will have a distortion when Na+ ions intercalate or diffuse in the interlayer or the second adsorption layer. The ultrasmall diffusion barrier of Na+ ion denotes that these structures have a fast charge/discharge speed, and the ultrasmall open circuit voltages (OCVs) of 0.18 and 0.21 V prove that they are promising candidates for SIBs. The ultralow overpotential 0.55 V/0.20 V for the ηORR/ηOER means that the O facet of the VS2/Ti2CO2 heterostructure also has a great potential in the application of Na-O2 batteries. These simulations prove that the heterostructures constructed by TMDs with MXenes have great potential in SIBs and Na-O2 batteries and are important for future battery design.