Hierarchical Architecture Engineering of Branch-Leaf-Shaped Cobalt Phosphosulfide Quantum Dots: Enabling Multi-Dimensional Ion-Transport Channels for High-Efficiency Sodium Storage

Defect engineering constructs two-dimensional metal sulfoselenide with expanded interlayers for fast and efficient sodium ion storage

Leveraging abundant natural reserves and lower cost profiles, sodium-ion batteries (SIBs) are poised to supersede lithium-ion batteries (LIBs) within the domain of large-scale energy storage systems. Many achievements have been made in improving the properties of anodes in SIBs from the aspects of nanostructure and surface modification. Recently, the incorporation of anionic species into metal sulfides via defect engineering has emerged as an innovative strategy to boost sodium storage capabilities. Herein, a nitrogen-doped carbon-coated two-dimensional metal sulfide with partial selenium substitution (SnS0.6Se1.4@NC) is constructed and utilized as an anode material for SIBs. The substitution of Se2- effectively expanded the interlayer distance of SnS2, making it more favorable for Na+ intercalation/deintercalation. The lattice defects introduced thereby have catalyzed the swift nucleation of conversion-alloying reaction products, acting as effective stabilizers and dispersants. The establishment of heterogeneous interfaces has expedited ion/electron transport, thereby enhancing electrochemical kinetics. Furthermore, the external carbon layer has mitigated the volumetric expansion of the electrode material. This innovative strategy has endowed the anodes with superior cyclic performance (506.6 mA h g-1 at 0.1 A g-1 after 200 cycles) and rate capability (312.4 mA h g-1 at 1 A g-1 after 500 cycles) in SIBs, offering a novel pathway for the design of high-performance metal sulfide anode materials.

Synchronous Regulation of S-Deficient ZnS-MoS2 Heterostructure Nanoreactor for Fast and Durable Sodium Storage

The enhancement of charge transfer and the relief of volume stress of anode materials contribute to fully exploiting electrochemical performance for sodium ion storage. Herein, a hollow carbon polyhedra nanoreactor adhered with a ZnS-MoS2 heterostructure with tunable sulfur vacancy content (denoted as hp-ZMS-600/700/800) is prepared by self-assembly and a temperature dependent sulfurization procedure. The intimate heterointerface and moderate sulfur vacancies provide fast ion/electron transfer channels, and the hollow nanoreactors afford large volume variation and maintain structural integrity during the sodiation/desodiation process. Theoretical calculations and in situ/ex situ characterization techniques reveal both excellent electron/ion diffusion dynamics and a sodium storage mechanism. As a result, the optimized hp-ZMS-700 anode in sodium-ion batteries delivers a high initial Coulombic efficiency of 96.3%, a high capacity of 398 mAh g-1 at 0.1 A g-1, good rate capability of 119.8 mAh g-1 at 5 A g-1, and an excellent capacity retention of 84.6% after 1000 cycles at 2 A g-1.

High-entropy sulfoselenide as negative electrodes with fast kinetics and high stability for sodium-ion batteries

Conversion electrodes offer higher reversible capacity and lower cost than conventional intercalation chemistry electrodes, but suffer from kinetic limitation and large volume expansion. Despite significant efforts, developing conversion electrodes with fast charging capability and extended lifespan remains challenging. Here, by leveraging the advantages of high-entropy doping and morphology tailoring, we develop a high-entropy hierarchical micro/nanostructured sulfoselenide Cu0.88Sn0.02Sb0.02Bi0.02Mn0.02S0.9Se0.1 electrode with entropy-driven fast-charging capability. When used as a negative electrode material for sodium-ion batteries, it achieves a stable cycle life of 10,000 cycles at 30 A g-1 and a high reversible capacity of 365.7 mAh g-1 under fast charging in 13 seconds at 100 A g-1. Moreover, high-entropy sulfoselenide also demonstrates stable cycling and good rate capability as a positive electrode material for lithium metal batteries, achieving a fast-charging capability of 37 seconds that is comparable with state-of-the-art layered cathodes. High-entropy sulfoselenide is characterized by its robust crystal structure, low ion diffusion barrier, and effective suppression of side reactions with electrolytes during cycling. Importantly, transmission X-ray microscopy affirms the chemical stability of HESSe, which underpins its fast-charging performance.

Se-Regulated MnS Porous Nanocubes Encapsulated in Carbon Nanofibers as High-Performance Anode for Sodium-Ion Batteries

Manganese-based chalcogenides have significant potential as anodes for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, abundant natural reserves, and environmental friendliness. However, their application is hindered by poor cycling stability, resulting from severe volume changes during cycling and slow reaction kinetics due to their complex crystal structure. Here, an efficient and straightforward strategy was employed to in-situ encapsulate single-phase porous nanocubic MnS0.5Se0.5 into carbon nanofibers using electrospinning and the hard template method, thus forming a necklace-like porous MnS0.5Se0.5-carbon nanofiber composite (MnS0.5Se0.5@N-CNF). The introduction of Se significantly impacts both the composition and microstructure of MnS0.5Se0.5, including lattice distortion that generates additional defects, optimization of chemical bonds, and a nano-spatially confined design. In situ/ex-situ characterization and density functional theory calculations verified that this MnS0.5Se0.5@N-CNF alleviates the volume expansion and facilitates the transfer of Na+/electron. As expected, MnS0.5Se0.5@N-CNF anode demonstrates excellent sodium storage performance, characterized by high initial Coulombic efficiency (90.8%), high-rate capability (370.5 mAh g-1 at 10 A g-1) and long durability (over 5000 cycles at 5 A g-1). The MnS0.5Se0.5@N-CNF //NVP@C full cell, assembled with MnS0.5Se0.5@N-CNF as anode and Na3V2(PO4)3@C as cathode, exhibits a high energy density of 254 Wh kg-1 can be provided. This work presents a novel strategy to optimize the design of anode materials through structural engineering and Se substitution, while also elucidating the underlying reaction mechanisms.

Rational Design of Cobalt-Based Prussian Blue Analogues via 3 d Transition Metals Incorporation for Superior Na-Ion Storage

Understanding the relationship between structure regulation and electrochemical performance is key to developing efficient and sustainable sodium-ion batteries (SIBs) materials. Herein, seven Cobalt-M-based (M=V, Mn, Fe, Co, Ni, Cu, Zn) Prussian blue analogues (CoM-PBAs) are designed as anodes for SIBs via a universal low-energy co-precipitation approach with the strategic inclusion of 3d transition metals. Density Functional Theory (DFT) simulation and experimental validation reveal that a moderate p-band center of cyanide linkages (-CN-) is more favorable for Na+ intercalation and diffusion, while the d-band center of metal cations is linearly related to electrode stability. Among seven CoM-based PBAs, CoV-PBAs possess the best sodium-ion adsorption/diffusion kinetics and overall cycling performance, including high specific capacity (565 mAh/g at 0.1 A/g), cycling stability (over 15000 cycles with 97.7 % capacity retention), and superior rate capability (174.7 mAh/g at 30 A/g). In situ/ex situ techniques further demonstrate that the π-electron regulation by V introduction enhances the reversibility and kinetics of redox reactions. Moreover, the study identified the "p-band center" and "d-band center" may serve as key descriptors for quantifying the capability and stability of other-type bimetal Co-based anodes (oxides, phosphides, sulfides, and selenides) with similar theoretical capacity, offering a potentially transformative approach for selecting practical SIB electrode materials.

Multitrack Boosted Hard Carbon Anodes: Innovative Paths and Advanced Performances in Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are emerging as a potential alternative to traditional lithium-ion batteries due to the abundant sodium resources. Carbon anodes, with their stable structure, wide availability, low cost, excellent conductivity, and tunable morphology and pore structure, exhibit outstanding performance in SIBs. This review summarizes the research progress of hard carbon anodes in SIBs, emphasizing the innovative paths and advanced performances achieved through multitrack optimization, including dimensional engineering, heteroatom doping, and microstructural tailoring. Each dimension of carbon material-0D, 1D, 2D, and 3D-offers unique advantages: 0D materials ensure uniform dispersion, 1D materials have short Na+ diffusion paths, 2D materials possess large specific surface areas, and 3D materials provide e-/Na+ conductive networks. Heteroatom doping with elements such as N, S, and P can tune electronic distribution, expand interlayer spacing of carbon, and induce Fermi level shifts, thereby enhancing sodium storage capability. In addition, defect engineering improves electrochemical performance by modifying graphitic crystal structure. Furthermore, suitable pore structure design, particularly closed pore structures, can increase capacity, minimizes side reactions, and suppress degradation. In future studies, optimizing morphology design, exploring heteroatom co-doping, and developing environmentally friendly, low-cost carbon anode methods will drive the application of high-performance and long cycle life SIBs.

Binary Metal Alloy Electrocatalyst Synergistically Accelerates the Bidirectional Polysulfide Conversions in Lithium-Sulfur Batteries

The sluggish redox kinetics of polysulfides and the resulting shuttle effect remain significant challenges for the practical utilization of lithium-sulfur (Li-S) batteries. To address the unidirectional catalytic limitations of conventional electrocatalysts, we herein report a binary metal (CoNi) alloy embedded in a carbon matrix on carbon nanofibers (CoNi@C-CNFs) as a highly efficient electrocatalyst to accelerate bidirectional polysulfide conversions. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals a significantly improved catalytic effect of the CoNi alloy toward polysulfide conversions after introducing the Ni component. Theoretical simulations further confirm that the synergistic interaction between the Co and Ni atoms enhances catalytic performance. Electrochemical measurements demonstrate a high specific capacity of 705 mAh g-1 at 3.0 C and exceptional long-term cyclic stability at both 1.0 and 2.0 C. Impressively, an areal capacity of 5.28 mAh cm-2 is achieved under a sulfur loading of ∼6.1 mg cm-2 with lean electrolyte conditions (∼6.5 μL mgs-1).

Design of Ligand-Nonbridging Sites in Metal-Organic Frameworks for Boosting Lithium Storage Capacity

Metal-organic frameworks (MOFs) are lagging in the use of lithium-ion batteries (LIBs), ascribing to full coordination between metal nodes and organic ligands, to a large extent. By integrating a modulator into a ligand with missing bridging functionality, this study elucidates the role of non-bridging defect sites in MOFs in tailoring lithium storage performance. A fully bridged pristine MOF (p-MOF) utilizing the meso-tetra(4-carboxylphenyl) porphyrin ligand is compared with a modified MOF containing non-bridging defects (d-MOF) introduced by a homologous ligand, tris(4-carboxyphenyl) porphyrin. Spectroscopic and cryogenic low-dose electron microscopy techniques verify the presence of non-bridging defect sites in the d-MOF and reveal their explicit local structure. Density functional theory calculations show significantly enhanced Li+ adsorption energies and reduced Li+ migration barriers at the non-bridging sites in the d-MOF compared to the fully bridging sites in the p-MOF. As a result, the d-MOF exhibits exceptional lithium storage performance, achieving a high capacity of 761 mAh g-1 at 0.05 A g-1 and superior rate performance of 203 mAh g-1 at 5 A g-1, which substantially outperform the p-MOF. This study highlights the potential of modulating MOFs with non-bridging defects to develop high-performance LIBs.

Mechanically Robust Bismuth-Embedded Carbon Microspheres for Ultrafast Charging and Ultrastable Sodium-Ion Batteries

Advancements in the development of fast-charging and long-lasting microstructured alloying anodes with high volumetric capacities are essential for enhancing the operational efficiency of sodium-ion batteries (SIBs). These anodes, however, face challenges such as declined cyclability and rate capability, primarily due to mechanical degradation reduced by significant volumetric changes (over 252%) and slow kinetics of sodium-ion storage. Herein, we introduce a novel anode design featuring densely packed bismuth (Bi) embedded within highly conductive carbon microspheres to overcome the aforementioned challenges. Remarkably, the high loading Bi anode within carbon microspheres with a high tap density of 2.59 g cm-3 possesses significant mechanical strength exceeding 590 MPa and limits volume swelling of only 10.9% post-sodiation. This anode demonstrates a high volumetric capacity (908.3 mAh cm-3), ultrafast chargeability (200 A g-1, full charge/discharge in just 5.5 s), and outstanding cyclability over 12,000 cycles and maintains exceptional cycling stability even at -30 °C. The full cell paired with a Na3V2(PO4)3 cathode retains over 80% capacity after 600 cycles at 36 C, demonstrating a remarkable rate capability of 126 C (full charge/discharge in 28.6 s). Our comprehensive experimental evaluations and chemo-mechanical simulations shed light on the mechanisms underpinning the anode's superior performance. This development marks a significant advancement in the design of durable and fast-charging anodes for high-performance SIBs.

Hierarchical core-shelled CoMo layered double hydroxide@CuCo2S4 nanowire arrays/nickel foam for advanced hybrid supercapacitors

The development of core-shelled heterostructures with the unique morphology can improve the electrochemical properties of hybrid supercapacitors (HSC). Here, CuCo2S4 nanowire arrays (NWAs) are vertically grown on nickel foam (NF) utilizing hydrothermal synthesis. Then, CoMo-LDH nanosheets are uniformly deposited on the CuCo2S4 NWAs by electrodeposition to obtain the CoMo-LDH@CuCo2S4 NWAs/NF electrode. Due to the superior conductivity of CuCo2S4 (core) and good redox activity of CoMo-LDH (shell), the electrode shows excellent electrochemical properties. The electrode's specific capacity is 1271.4 C g-1 at 1 A g-1, and after 10, 000 cycles, its capacity retention ratio is 92.2 % at 10 A g-1. At a power density of 983.9 W kg-1, the CoMo-LDH@CuCo2S4 NWAs/NF//AC/NF device has an energy density of 52.2 Wh kg-1. This indicates that CoMo-LDH@CuCo2S4/NF has a great potential for supercapacitors.

Optimizing Reversible Phase-Transformation of FeS2 Anode via Atomic-Interface Engineering Toward Fast-Charging Sodium Storage: Theoretical Predication and Experimental Validation

Sodium-storage performance of pyrite FeS2 is greatly improved by constructing various FeS2-based nanostructures to optimize its ion-transport kinetics and structural stability. However, less attention has been paid to rapid capacity degradation and electrode failure caused by the irreversible phase-transition of intermediate NaxFeS2 to FeS2 and polysulfides dissolution upon cycling. Under the guidance of theoretical calculations, coupling FeS2 nanoparticles with honeycomb-like nitrogen-doped carbon (NC) nanosheet supported single-atom manganese (SAs Mn) catalyst (FeS2/SAs Mn@NC) via atomic-interface engineering is proposed to address above challenge. Systematic electrochemical analyses and theoretical results unveil that the functional integration of such two type components can significantly enhance ionic conductivity, accelerate charge transfer efficiency, and improve Na+-adsorption capability. Particularly, SAs Mn@NC with Mn-Nx coordination center can reduce the decomposition barrier of Na2S and NaxFeS2 to further accelerate reversible phase transformation of Fe/Na2S→NaFeS2→FeS2 and polysulfides decomposition. As predicted, such FeS2/SAs Mn@NC showcases outstanding rate capability and fascinating cyclic durability. A sequence of kinetic studies and ex situ characterizations provide the comprehensive understanding for ion-transport kinetics and phase-transformation process. Its practical use is further demonstrated in sodium-ion full cell and capacitor with impressive electrochemical capability and excellent energy-density output.

Chemistry of Materials for Energy and Environmental Sustainability

In contemporary society, energy serves as the cornerstone of human survival and development, exerting a profound influence on the economic development of nations and the trajectory of global progress [...].

Unraveling the Ionic Storage Mechanism of Flexible Nitrogen-Doped MXene Films for High-Performance Aqueous Hybrid Supercapacitors

2D MXene nanomaterials have excellent potential for application in novel electrochemical energy storage technologies such as supercapacitors and batteries, but the existing pure MXene is difficult to meet the practical needs. Although the electrochemical properties of modified MXene have been improved, the unclear ion storage mechanism still hinders the development of MXene-based electrode materials. Herein, the study develops flexible self-supported nitrogen-doped Ti3C2 (Py-Ti3C2) films by the highly mobile, high nitrogen content, oxygen-free pyridine-assisted solvothermal method, and then deeply investigates the energy storage mechanism of hybrid supercapacitors in four aqueous electrolytes (H2SO4, Li2SO4, Na2SO4, and MgSO4). The experimental results suggest that the Py-Ti3C2 film electrode exhibits a pseudocapacitance-dominated energy storage mechanism. Particularly, the specific capacity of the Py-Ti3C2 in 1 M H2SO4 (506 F g-1 at 0.1 A g-1) is 4-5 times higher than other electrolytes (≈110 F g-1), which could be attributed to the substantially higher ionic diffusion coefficient of H+ than those of Li+, Na+, Mg2+ with small ionic size, high ionic conductivity, and fast pseudocapacitance response. Theoretical analysis further confirms that Py-Ti3C2 has strengthened conductivity and electrical double-layer capacitance performance. Meanwhile, it has lower free energy for protonation and deprotonation of functional groups, which gives excellent pseudocapacitance performance.

Nanoarchitectured Fe3C@N-Doped C/FeVO4 as High-Performance Anode for Sodium-Ion Batteries

Ferric vanadate exhibits potential as an attractive anode material for sodium-ion batteries (SIBs) due to the multiple oxidation states of vanadium and natural abundances of iron. However, the design and fabrication of high-performance ferric vanadate-based SIB anode materials with unique composite nanostructures are still challenging. Herein, a facile self-template method is reported to synthesize 1D nanostructured Fe3C@N-doped C/FeVO4 (Fe3C@NC/FeVO4) anode materials by the combination of morphology regulation with hybrid composite construction, for the first time. To this end, a 1D Fe, N-doped carbon nanotube (FeNC) is used as a template, followed by etching and re-growth to obtain the 1D Fe3C@N-doped C/FeVO4 nanostructure. The introduction of Fe3C can improve its electronic conductivity and enhance capacitive behavior. Additionally, the 1D nanostructure can effectively shorten the ions transport path and alleviate volume expansion during the charge-discharge processes. With these advantages, the SIBs using such anodes show a remarkable rate performance with a capacity of 325.4 mAh g-1 at 0.1 A g-1, 150.6 mAh g-1 at 5 A g-1, and excellent cycling stability with a reversible capacity of 139.6 mAh g-1 at 1 A g-1 after 1500 cycles. This work offers a new strategy for the future development of SIBs with ferric vanadate-based anode.

Heterojunction and vacancy engineering strategies and dual carbon modification of MoSe2-x@CoSe2-C /GR for high-performance sodium-ion batteries and hybrid capacitors

Sodium-ion batteries (SIBs) and hybrid capacitors (SIHCs) have great potential in related electrochemical energy storage fields. However, the inferior cycling performance and sluggish kinetics of Na+ transport in conventional anodes continue to impede their practical applications. Here, we propose a refined design by utilizing well-organized MoSe2 nanorods as precursors and introducing a metal-organic framework and graphene (GR), while resulting in the formation of bimetallic selenide heterostructures/carbon MoSe2-x@CoSe2-C/GR (MCCR) composite through electronegativity. The MoSe2-x/CoSe2 heterostructure can spontaneously form the built-in electric field to accelerate the charge transport, and the formation of anionic Se vacancies induced by electronegativity in situ can provide more active sites for enhancing sodium storage. The presence of external carbon and graphene can act as buffer layers to suppress the volume expansion of MoSe2-x/CoSe2 heterogeneous, and on the other hand, form a conductive network externally to improve electrode conductivity. As anticipated, the MCCR electrode demonstrates superior reversible specific capacity (446 mAh g-1 after 100 cycles) and substantial pseudocapacitance contribution, excellent rate performance in SIB half and full cells. In addition, system electrochemical analysis of multiple ex-situ characterizations elucidates the electrochemical reaction kinetics and transformation mechanism of MCCR electrodes during charging and discharging in depth. When coupled with activated carbon (AC), the MCCR//AC SIHC full hybrid capacitors exhibit impressive cycling stability over 2500 cycles at 1 A g-1 and excellent rate performance, demonstrating their widespread application in energy storage.

Hollow Porous Co0.85Se/ZnSe@MXene Anode with Multilevel Built-in Electric Fields for High-Performance Sodium Ion Capacitors

Sodium ion capacitors (SICs) are promising candidates in energy storage for their remarkable power and energy density. However, the inherent disparity in dynamic behavior between the sluggish battery-type anodes and the rapid capacitor-type cathodes constrained their performance. To address this, we fabricated a hollow porous Co0.85Se/ZnSe@MXene anode featuring multiheterostructure, utilizing facile etching and electrostatic self-assembly strategies. The hollow porous structure and multiple heterointerfaces stabilize the anode by mitigating the volume changes. Density functional theory (DFT) calculations further revealed that induced multilevel built-in electric fields facilitate the formation of rapid ion diffusion pathways and reduce the Na+ adsorption energy, thereby boosting Na+/electron transport kinetics. The fabricated TA-Co0.85Se/ZnSe@MXene anode demonstrates outstanding long-term cycling stability of 406 mA h g-1 after 1000 cycles at 1 A g-1, with an ultrahigh rate performance of 288 mA h g-1 at 10 A g-1. When paired with the active carbon (AC) cathode, the SICs deliver extraordinary energy/power densities of 144 W h kg-1 and 12000 W kg-1, maintaining over 80% capacity retention at 1 A g-1 after 10000 cycles. This innovative strategy of engineering multiheterostructured anode with the induced multilevel built-in electric fields holds significant promise for advancing high-energy and high-power energy storage systems.

Efficient Sodium Storage in Cu1.96S@NC Anode Achieved by Robust S─C Bonds and Current Collector Self-Induced Forming Cu2S Quantum Dots

Transition metal sulfides are investigation hotspots of anode material for sodium-ion batteries (SIBs) due to their structural diversity and high storage capacity. However, they are still plagued by inevitable volume expansion during sodiation/desodiation and an unclear energy storage mechanism. Herein, a one-step sulfidation-carbonization strategy is proposed for in situ confined growth of Cu1.96S nanoparticles in nitrogen-doped carbon (Cu1.96S@NC) using octahedral metal-organic framework (Cu-BTC) as a precursor and investigate the driving effect of Cu current collector on its sodium storage. The generation of S─C bonds in Cu1.96S@NC avoids the volume change and structural collapse of Cu1.96S nanoparticles during the cycling process and improves the adsorption and transport capacity of the material for Na+. More exciting, the Cu species in the Cu current collector are self-induced forming Cu2S quantum dots to enter the original anode material during the initial few charging and discharging cycles, which unique small-size effect and abundant edge-active sites enhance the energy storage capacity of Cu1.96S. Thus, the Cu1.96S@NC exhibits a superior first discharge capacity of 608.56 mAh g-1 at 0.2 A g-1 with an initial Coulomb efficiency (ICE) of 75.4%, as well as provides excellent rate performance and long cycle durability up to 2000 cycles.

Carbon-Coated MOF-Derived Porous SnPS3 Core-Shell Structure as Superior Anode for Sodium-Ion Batteries

Metal thiophosphites have recently emerged as a hot electrode material system for sodium-ion batteries because of their large theoretical capacity. Nevertheless, the sluggish electrochemical reaction kinetics and drastic volume expansion induced by the low conductivity and inherent conversion-alloying reaction mechanism, require urgent resolution. Herein, a distinctive porous core-shell structure, denoted as SnPS3@C, is controllably synthesized by synchronously phosphor-sulfurizing resorcinol-formaldehyde-coated tin metal-organic framework cubes. Thanks to the 3D porous structure, the ion diffusion kinetics are accelerated. In addition, SnPS3@C features a tough protective carbon layer, which improves the electrochemical activity and reduces the polarization. As expected, the as-prepared SnPS3@C electrode exhibits superior electrochemical performance compared to pure SnPS3, including excellent rate capability (1342.4 and 731.1 mAh g-1 at 0.1 and 4 A g-1, respectively), and impressive long-term cycling stability (97.9% capacity retention after 1000 cycles at 1 A g-1). Moreover, the sodium storage mechanism is thoroughly studied by in-situ and ex-situ characterizations. This work offers an innovative approach to enhance the energy storage performance of metal thiophosphite materials through meticulous structural design, including the introduction of porous characteristics and core-shell structures.

Stress-Dispersed Nanoconstruction of CoMoP Anode: Improved Na-Storage Stability and Reversibility

Metal phosphide anode materials encounter poor reversibility of the discharge product (metal and Na3P) and large volume variation, resulting in low initial Coulombic efficiency (ICE) and severe capacity degradation. Herein, a bimetallic phosphide (CoMoP) with three-dimensional ordered porous (3DOP) nanoconstruction was fabricated, which presents a reduced Gibbs free energy change (ΔG) of redox reaction between Co-Mo/Na3P and CoMoP and improved conductivity compared to CoP and MoP. Additionally, the 3DOP architecture could disperse stress and reduce strain during cycling, thus improving structural stability of CoMoP. In situ and ex situ characterizations and electrochemical measurements suggest that 3DOP CoMoP exhibits highly reversible sodium storage with an ICE of 58% at 0.1 A g-1, enhanced reaction dynamics, and good cycling stability with around 0.04% capacity decay per cycle at 1 A g-1 after 1000 cycles. Consequently, this work offers a new perspective to solve issues of reversibility of redox chemistry and volume expansion for secondary batteries.

Heterostructured MnSe/FeSe nanorods encapsulated by carbon with enhanced Na+ diffusion as anode materials for sodium-ion batteries

The natural abundance of sodium has fostered the development of sodium-ion batteries for large-scale energy storage. However, the low capacity of the anodes hinders their future application. Herein, carbon-encapsulated MnSe-FeSe nanorods (MnSe-FeSe@C) have been fabricated by the in-situ transformation from polydopamine-coated MnO(OH)-Fe2O3. The heterostructure constructed by MnSe and FeSe nanocrystals induces the formation of built-in electric fields, accelerating electron transfer and ion diffusion, thereby improving reaction kinetics. In addition, carbon enclosure can buffer the volumetric stress and enhance the electrical conductivity. These aspects cooperatively endow the anode with superior cycling stability and distinguished rate performance. Specifically, the discharge capacity of MnSe-FeSe@C reaches 414.3 mA h g-1 at 0.1 A g-1 and 388.8 mA h g-1 even at a high current density of 5.0 A g-1. In addition, it still retains a high reversible capacity of 449.2 mA h g-1 after 700 long cycles at 1.0 A g-1. Further, the ab initio calculation has been employed to authenticate the existence of the built-in electric field by Bader charge, indicating that 0.24 electrons in MnSe were transferred to FeSe. The in-situ XRD has been used to evaluate the phase transition during the charging/discharging process, revealing the sodium ion storage mechanism. The construction of heterostructure material paves a new way to design performance-enhanced anode materials for sodium-ion batteries.

Heterogeneous MoS2 Nanosheets on Porous TiO2 Nanofibers toward Fast and Reversible Sodium-Ion Storage

2D layered molybdenum disulfide (MoS2) has garnered considerable attention as an attractive electrode material in sodium-ion batteries (SIBs), but sluggish mass transfer kinetic and capacity fading make it suffer from inferior cycle capability. Herein, hierarchical MoS2 nanosheets decorated porous TiO2 nanofibers (MoS2 NSs@TiO2 NFs) with rich oxygen vacancies are engineered by microemulsion electrospinning method and subsequent hydrothermal/heat treatment. The MoS2 NSs@TiO2 NFs improves ion/electron transport kinetic and long-term cycling performance through distinctive porous structure and heterogeneous component. Consequently, the electrode exhibits excellent long-term Na storage capacity (298.4 mAh g-1 at 5 A g-1 over 1100 cycles and 235.6 mAh g-1 at 10 A g-1 over 7200 cycles). Employing Na3V2(PO4)3 as cathode, the full cell maintains a desirable capacity of 269.6 mAh g-1 over 700 cycles at 1.0 A g-1. The stepwise intercalation-conversion and insertion/extraction endows outstanding Na+ storage performance, which yields valuable insight into the advancement of fast-charging and long-cycle life SIBs anode materials.

Pomegranate Peel-Derived Hard Carbons as Anode Materials for Sodium-Ion Batteries

Exploring high-performance carbon anodes that are low-cost and easily accessible is the key to the commercialization of sodium-ion batteries. Producing carbon materials from bio by-products is an intriguing strategy for sodium-ion battery anode manufacture and for high-value utilization of biomass. Herein, a novel hard carbon (PPHC) was prepared via a facile pyrolysis process followed by acid treatment using biowaste pomegranate peel as the precursor. The morphology and structure of the PPHC were influenced by the carbonization temperature, as evidenced by physicochemical characterization. The PPHC pyrolyzed at 1100 °C showed expanded interlayer spacing and appropriate oxygen group content. When used as a sodium ion battery anode, the PPHC-1100 demonstrated a reversible capacity of up to 330 mAh g-1, maintaining 174 mAh g-1 at an increased current rate of 1 C. After 200 cycles at 0.5 C, the capacity delivered by PPHC-1100 was 175 mAh g-1. The electrochemical behavior of PPHC electrodes was investigated, revealing that the PPHC-1100 possessed increased capacitive-controlled energy storage and improved ion transport properties, which explained its excellent electrochemical performance. This work underscores the feasibility of high-performance sodium-ion battery anodes derived from biowaste and provides insights into the sodium storage process in biomass-derived hard carbon.

Microfluidic Synthesis of Multifunctional Micro-/Nanomaterials from Process Intensification: Structural Engineering to High Electrochemical Energy Storage

Multifunctional micro-/nanomaterials featuring functional superiority and high value-added physicochemical nature have received immense attention in electrochemical energy storage. Microfluidic synthesis has become an emergent technology for massively producing multifunctional micro-/nanomaterials with tunable microstructure and morphology due to its rapid mass/heat transfer and precise fluid controllability. In this review, the latest progresses and achievements in microfluidic-synthesized multifunctional micro-/nanomaterials are summarized via reaction process intensification, multifunctional micro-/nanostructural engineering and electrochemical energy storage applications. The reaction process intensification mechanisms of various micro-/nanomaterials, including quantum dots (QDs), metal materials, conducting polymers, metallic oxides, polyanionic compounds, metal-organic frameworks (MOFs) and two-dimensional (2D) materials, are discussed. Especially, the multifunctional structural engineering principles of as-fabricated micro-/nanomaterials, such as vertically aligned structure, heterostructure, core-shell structure, and tunable microsphere, are introduced. Subsequently, the electrochemical energy storage application of as-prepared multifunctional micro-/nanomaterials is clarified in supercapacitors, lithium-ion batteries, sodium-ion batteries, all-vanadium redox flow batteries, and dielectric capacitors. Finally, the current problems and future forecasts are illustrated.

Micro-mesoporous cobalt phosphosulfide (Co3S4/CoP/NC) nanowires for ultrahigh rate capacity and ultrastable sodium ion battery

The construction of heterostructure materials has been demonstrated as the promising approach to design high-performance anode materials for sodium ion batteries (SIBs). Herein, micro-mesoporous cobalt phosphosulfide nanowires (Co3S4/CoP/NC) with Co3S4/CoP hetero-nanocrystals encapsulating into N-doped carbon frameworks were successfully synthesized via hydrothermal reaction and subsequent phosphosulfidation process. The obtained micro-mesoporous nanowires greatly improve the charge transport kinetics from the facilitation of the charge transport into the inner part of nanowire. When evaluated as SIBs anode material, the Co3S4/CoP/NC presents outstanding electrochemical performance and battery properties owing to the synergistic effect between Co3S4 and CoP nanocrystals and the conductive carbon frameworks. The electrode material delivers outstanding reversible rate capacity (722.33 mAh/g at 0.1 A/g) and excellent cycle stability with 522.22 mAh/g after 570 cycles at 5.0 A/g. Besides, the Ex-situ characterizations including XRD, XPS, and EIS further revealed and demonstrated the outstanding sodium ion storage mechanism of Co3S4/CoP/NC electrode. These findings pave a promising way for the development of novel metal phosphosulfide anodes with unexpected performance for SIBs and other alkali ion batteries.

Regulating nitrogen/sulfur terminals on 3D porous Ti3C2 MXene with enhanced reaction kinetics toward high-performance alkali metal ion storage

In this paper, we have developed a simple and efficient sulfur-amine chemistry strategy to prepare a three-dimensional (3D) porous Ti3C2Tx composite with large amounts of N and S terminal groups. The well-designed 3D macroporous architecture presents enlarged interlayer spacing, large specific surface area, and unique porous structure, which successfully solves the re-stacking issue of MXene during storage and electrode fabrication. It is the amount of concentrated hydrochloric acid added to the S-EDA (ethylenediamine)/MXene colloidal suspension that is critical to the formation of 3D morphology. In addition, N and S terminals on MXene could improve the adsorption ability of K+. Owing to the synergistic effect of the structure design and terminal modification, the N, S codoped three-dimensional porous Ti3C2Tx (3D-NSPM) material shows a high surface capacitive contribution and rapid diffusion kinetics for K+ and Na+. As a result, the as-prepared 3D-NSPM delivers high reversible capacity (237 and 273 mAh g-1 at 0.1 A g-1 for PIBs and SIBs, respectively), superb cycling stability (84.9% capacity retention after 10,000 cycles at 1 A g-1 in PIBs and 74.0% capacity retention after 2200 cycles at 1 A g-1 in SIBs), and excellent rate capability (111 and 196 mAh g-1 at 5 A g-1 for PIBs and SIBs, respectively), which are superior to other MXene-based anodes for PIBs and SIBs. Moreover, the described strategy provides a new insight for constructing the 3D porous structure from 2D building blocks beyond MXene.

Restraining the shuttle effect of polyiodides and modulating the deposition of zinc ions to enhance the cycle lifespan of aqueous Zn-I2 batteries

The boom of aqueous Zn-based energy storage devices, such as zinc-iodine (Zn-I2) batteries, is quite suitable for safe and sustainable energy storage technologies. However, in rechargeable aqueous Zn-I2 batteries, the shuttle phenomenon of polyiodide ions usually leads to irreversible capacity loss resulting from both the iodine cathode and the zinc anode, and thus impinges on the cycle lifespan of the battery. Herein, a nontoxic, biocompatible, and economical polymer of polyvinyl alcohol (PVA) is exploited as an electrolyte additive. Based on comprehensive analysis and computational results, it is evident that the PVA additive, owing to its specific interaction with polyiodide ions and lower binding energy, can effectively suppress the migration of polyiodide ions towards the zinc anode surface, thereby mitigating adverse reactions between polyiodide ions and zinc. Simultaneously, the hydrogen bond network of water molecules is disrupted due to the abundant hydroxyl groups within the PVA additive, leading to a decrease in water activity and mitigating zinc corrosion. Further, because of the preferential adsorption of PVA on the zinc anode surface, the deposition environment for zinc ions is adjusted and its nucleation overpotential increases, which is favorable for the dense and uniform deposition of zinc ions, thus ensuring the improvement of the performance of the Zn-I2 battery. This investigation has inspired the development of a user-friendly and high-performance Zn-I2 battery.

A Two-dimensional Metal-Organic Framework as Promising Cathode for Advanced Lithium Storage

Anthraquinone electrode materials are promising candidates for lithium-ion batteries (LIBs) due to the abundance of anthraquinone and the high theoretical capacity, and good reversibility of the anthraquinone electrodes. However, the active anthraquinone materials are soluble in organic electrolytes, resulting in a sharp decay of capacity during the charge and discharge processes. Herein, we report on a two-dimensional calcium anthraquinone 2,3-dicarboxy metal-organic framework (2D CaAQDC MOF) fabricated using a simple hydrothermal method. The 2D CaAQDC MOF not only effectively inhibits the dissolution of active electrode substances into the electrolyte, but also promotes the diffusion of lithium ion into the pores of the MOF. When used as a cathode for the LIBs, the resulting CaAQDC electrode delivers a high specific capacity of ~100 mAh g-1 at a current density of 50 mA g-1 after 200 cycles, demonstrating its good cycle stability. Even at a high current density of 200 mA g-1 , the CaAQDC electrode exhibits a specific capacity of ~60 mAh g-1 . The fabricated 2D coordination polymers effectively restrains the dissolution of anthraquinone into the organic electrolyte and enhances the structural stability, which greatly improves the electrochemical performance of anthraquinone. These research results offer a rational molecular design strategy to address the dissolution of this and other active organic electrode materials.