Ultrathick GeP Anode To Balance the Extreme Load and Compliance for High Areal Capacity Flexible Sodium-Ion Batteries

The ever-growing application of miniaturized electric devices calls for the manufacturing of energy storage systems with a high areal energy density. Thick electrode design is a promising strategy to acquire high areal energy density by enhancing active mass loading and minimizing inactive components. However, the sluggish reaction kinetics and poor electrode mechanical stability that are accompanied by the increased electrode thickness remain unsolved problems. Herein, for the first time, we propose a novel chemical cross-linking strategy to fabricate GeP thick electrodes with adjustable electrode thicknesses and active mass loadings for high areal capacity sodium-ion batteries (SIBs). The chemical cross-linking between carboxylic multiwalled carbon nanotubes (CNTs) and pyrolysis cellulose nanofibers (CNFs) forms a 3D network that encloses GeP nanoparticles, which guarantees fast charge transfer, efficient stress relief, and alleviated volume expansion/shrinkage of the electrode. The hierarchical porous structure generates numerous interconnected channels for unfettered Na+ diffusion, ensuring uncompromised reaction kinetics as the electrode thickness increases. As a result, the ultrathick 1031 μm GeP@C-CNTs-CNFs electrode featuring a mass loading of 18.3 mg cm-2 delivers an ultrahigh areal capacity of 10.58 mAh cm-2 accompanied by superior cycling stability, which outperforms all reported Ge-based electrodes (generally below 1.5 mAh cm-2). This work sheds insightful light on designing high areal capacity flexible thick electrodes for the applications of miniaturized electric devices.

Perspective on Iron-Based Phosphate Cathode for Commercial Sodium-Ion Cells

Sodium (Na)-ion batteries (SIBs) have been considered as a potential device for large-scale energy storage. To date, some start-up companies have released their first-generation SIBs cathode materials. Among them, phosphate compounds, particularly iron (Fe)-based mixed phosphate compounds, present great potential for commercial SIBs owing to its low cost, environment friendly. In this perspective, a brief historical retrospect is first introduce to the development of Fe-based mixed phosphate cathodes in SIBs. Then, the recent development about this kind of cathode has been summarized. One of the iron-based phosphate materials, Na3 Fe2 (PO4 )P2 O7 , is used as an example to roughly calculate the energy density and estimate the cost at the cell level to highlight their advantages. Finally, some strategies are put up to further increase the energy density of SIBs. This timely perspective aims to educate the community on the critical benefits of the Fe-based mixed phosphate cathode and provide an up-to-date overview of this emerging field.

A Conformal Protective Skin Producing Stable Cathode-Electrolyte Interface for Long-Life Potassium-Ion Batteries

The development of K-based layered oxide cathodes is essential for boosting the competitiveness of potassium-ion batteries (PIBs) in grid-scale energy storage. However, their service life is dramatically limited by interfacial instability issues, which is still poorly understood. In this work, amorphous FePO4 (a-FP) is built on K0.5 Ni0.1 Mn0.9 O2 (KNMO) as the protective skin, whose elasticity for strain relaxation and the K-conducting nature guarantee its integrity during fast and constant K-ion insertion/extraction. The conformal coating leads to a robust interphase on the cathode surface, which qualifies excellent K-transport ability and significantly suppresses the mechanical cracking and transition metal dissolution. Breakthrough in cycle life of the K-based layered cathodes is therefore achieved, which of the amorphous FePO4 coated K0.5 Ni0.1 Mn0.9 O2 (KNMO@a-FP) reaches 2500 cycles. The insights gained from the surface protection layer construction and the in-depth analysis of its working mechanism pave the way for further development of K-based layered cathodes with both bulk structural and interfacial stability.

Turbulence induced shear controllable synthesis of nano FePO4 irregularly-shaped particles in a counter impinging jet flow T-junction reactor assisted by ultrasound irradiation

FePO4 (FP) particles with a mesoporous structure amalgamated by nanoscale primary crystals were controllably prepared using an ultrasound-intensified turbulence T-junction microreactor (UTISR). The use of this type of reaction system can effectively enhance the micro-mixing and remarkably improve the mass transfer and chemical reaction rates. Consequently, the synergistic effects of the impinging streams and ultrasonic irradiation on the formation of mesoporous structure of FP nanoparticles have been systematically investigated through experimental validation and CFD simulation. The results revealed that the FP particles with a mesoporous structure can be well synthesised by precisely controlling the operation parameters by applying ultrasound irradiation with the input power in the range of 0-900 W and the impinging stream volumetric flow rate in the range of 17.15-257.22 mL·min-1. The findings obtained from the experimental observation and CFD modelling has clearly indicated that there exists a strong correlation between the particle size, morphology, and the local turbulence shear. The application of ultrasonic irradiation can effectively intensify the local turbulence shear in the reactor even at low Reynolds number based on the impinging stream diameter (Re < 2000), leading to an effective reduction in the particle size (from 273.48 to 56.1 nm) and an increase in the specific surface area (from 21.97 to 114.97 m2·g-1) of FP samples. The FPirregularly-shaped particles prepared by UTISR exhibited a mesoporous structure with a particle size of 56.10 nm, a specific surface area of 114.97 m2·g-1and a total pore adsorption volume of 0.570 cm3·g-1 when the volumetric flow rate and ultrasound power are 85.74 mL·min-1and 600 W, respectively.

Implanting CuS Quantum Dots into Carbon Nanorods for Efficient Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) are emerging as potential next-generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template-based strategy is proposed to successfully fabricate metal-organic framework-derived in-situ porous carbon nanorod-encapsulated CuS quantum dots (CuS-QD@C nanorods) via a two-step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS-QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g-1 at 100 mA g-1 after 100 cycles, excellent long-term cycling stability (98.5 mAh g-1 after 1000 cycles at 1.0 A g-1 ), and satisfying rate performance (111.8 mA g-1 at 1.0 A g-1 ).

Synthesis of F-doped materials and applications in catalysis and rechargeable batteries

Elemental doping is one of the most essential techniques for material modification. It is well known that fluorine is considered to be a highly efficient and inexpensive dopant in the field of materials. Fluorine is one of the most reactive elements with the highest electronegativity (χ = 3.98). Compared to cationic doping, anionic doping is another valuable method for improving the properties of materials. Many materials have physicochemical limitations that affect their practical application in the field of catalysis and rechargeable ion batteries. Many researchers have demonstrated that F-doping can significantly improve the performance of materials for practical applications. This paper reviews the applications of various F-doped materials in photocatalysis, electrocatalysis, lithium-ion batteries, and sodium-ion batteries, as well as briefly introducing their preparation methods and mechanisms to provide researchers with more ideas and options for material modification.

Vapor-phase derived ultra-fine Bismuth nanoparticles embedded in carbon nanotube networks as anodes for sodium and potassium ion batteries

Bismuth (Bi) is a promising material as the anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its characteristics such as reasonable price and high theoretical volumetric capacity (3800 mAh cm^-3). Nevertheless, considerable drawbacks have hindered the practical applications of Bi, including its relatively low electrical conductivity and inevitable volumetric change during the alloying/dealloying processes. To solve these problems, we proposed a novel design:Bi nanoparticles were synthesized via a single-step low-pressure vapor-phase reaction and embedded onto the surfaces of multi-walled carbon nanotubes (MWCNTs). After being vaporized at 650℃ and 10^-5 Pa, Bi nanoparticles less than 10 nm were uniformly distributed in the three-dimensional (3D) MWCNT networks to form a Bi/MWNTs composite. In this unique design, the nanostructured Bi can reduce the risk of structural rupture during cycling, and the structure of the MWCMT network is beneficial in shortening the electron/ion transport path. In addition, MWCNTs can improve the overall conductivity of the Bi/MWCNTs composite and prevent particle aggregation, thus improving the cycling stability and rate performance. As an anode material for SIB, the Bi/MWCNTs composite has demonstrated excellent fast charging performance with a reversible capacity of 254 mAh/g at 20 A/g. A capacity of 221mAhg^-1 after cycling at 10 A/g for 8000 cycles has also been achieved for SIB. As an anode material for PIB, the Bi/MWCNTs composite has delivered excellent rate performances with a reversible capacity of 251 mAh/g at 20 A/g. A specific capacity of 270mAhg^-1 after cycling at 1Ag^-1 for 5000 cycles has also been achieved for PIB.

An ultrastable sodium-ion battery anode enabled by carbon-coated porous NaTi2(PO4)3 olive-like nanospheres

NaTi₂(PO₄)₃ (NTP) is a promising anode material for sodium-ion batteries (SIBs). It has drawn wide attention because of its stable three-dimensional NASICON-type structure, proper redox potential, and large accommodation space for Na⁺. However, the inherent low electronic conductivity of the phosphate framework reduces its charge transfer kinetics, thus limiting its exploitation. Therefore, this paper proposes a material with carbon-coated porous NTP olive-like nanospheres (p-NTP@C) to tackle the issues above. Based on experimental data and theoretical calculations, the porous structure of the material is found to be able to provide more active sites and shorten the Na⁺ diffusion distance. In addition, the carbon coating can effectively improve the electron and Na⁺ diffusion kinetics. As the anode material for SIBs, the p-NTP@C olive-like nanospheres exhibit a high reversible capacity (127.3 mAh g^-1 at 0.1 C) and ultrastable cycling performance (84.8% capacity retention after 10,000 cycles at 5 C). Furthermore, the sodium-ion full cells, composed of p-NTP@C anode and Na₃V₂(PO₄)₂F₃@carbon cathode, also deliver excellent performance (75.7% capacity retention after 1000 cycles at 1 C). In brief, this nanostructure design provides a viable approach for the future development of long-life and highly stable NASICON-type anode materials.

Flexible Ammonium-Ion Pouch Cells Based on a Tunneled Manganese Dioxide Cathode

Aqueous ammonium-ion (NH₄⁺) batteries are becoming the competitive energy storage candidate on account of their safety, affordability, sustainability, and intrinsically peculiar properties. Herein, an aqueous NH₄⁺-ion pouch cell is investigated based on a tunneled manganese dioxide (α-MnO₂) cathode and a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) anode. The MnO₂ electrode possesses a high specific capacity of ∼190 mA h g^-1 at 0.1 A g^-1 and displays excellent long cycling performance after 50,000 cycles in 1 M (NH₄)₂SO₄, which outperforms the most reported ammonium-ion host materials. Besides, a solid-solution behavior is revealed about the migration of NH₄⁺ in the tunnel-like α-MnO₂. The battery displays a splendid rate capacity of 83.2 mA h g^-1 even at 10 A g^-1. It also exhibits a high energy density of ∼78 W h kg^-1 as well as a high power density of ∼8212 W kg^-1 (based on the mass of MnO₂). What is more, the flexible MnO₂//PTCDA pouch cell based on the hydrogel electrolyte shows excellent flexibility and good electrochemical properties. The topochemistry results of MnO₂//PTCDA point to the potential practicability of ammonium-ion energy storage.

Recent advances in epitaxial heterostructures for electrochemical applications

Construction of epitaxial heterostructures is crucial for boosting the electrochemical properties of various materials, however a review dedicated to this attractive topic is still lacking. In this Minireview, a timely summary on the achievements of epitaxial heterostructure design for electrochemical applications is provided. We first introduce the synthesis strategies to provide fundamental understanding on how to create epitaxial interfaces between different components. Secondly, the superiorities of epitaxial heterostructures in electrocatalysis, supercapacitors and batteries are highlighted with the underlying structure-property relationship elucidated. Finally, a discussion on the challenges and future prospects of this field is presented.

Thermodynamic Transformation of Crystalline Organic Hybrid Iron Selenide to FexSey@CN Microrods for Sodium Ion Storage

Carbon-coated metal chalcogenide composites have been demonstrated as one type of promising anode material for sodium-ion batteries (SIBs). However, combining carbon materials with micronanoparticles of metal chalcogenide always involve complicated processes, such as polymer coating, carbonization, and sulfidation/selenization. To address this issue, herein, we reported a series of carbon-coated FexSey@CN (FexSey = FeSe2, Fe3Se4, Fe7Se8) composites prepared via the thermodynamic transformation of a crystalline organic hybrid iron selenide [Fe(phen)2](Se4) (phen = 1,10-phenanthroline). By pyrolyzing the bulk crystals of [Fe(phen)2](Se4) at different temperatures, FexSey microrods were formed in situ, where the nitrogen-doped carbon layers were coated on the surface of the microrods. Moreover, all the as-prepared FexSey@CN composites exhibited excellent sodium-ion storage capabilities as anode materials in SIBs. This work proves that crystalline organic hybrid metal chalcogenides can be used as a novel material system for the in situ formation of carbon-coated metal chalcogenide composites, which could have great potential in the application of electrochemical energy storage.

Vanadium dissolution at 30 °C and its suppression at a low temperature of -20 °C for a Na3V1.5Cr0.5(PO4)3 cathode

Na₃V_1.5Cr_0.5(PO₄)₃ cycled at 30 °C shows fast capacity decay, due to the migration of V ions into the electrolyte and the loss of V³⁺/V⁴⁺ redox. A low temperature of -20 °C attenuates V-ion dissolution, retains V³⁺/V⁴⁺ redox and improves the electrochemical performance, favorable for use in cold climates and high-altitude drones.

Synthesis of Nanostructured Bismuth Sulfide with Controllable Morphology for Advanced Lithium/Sodium-Ion Storage

Rational design of electrode materials with an excellent structure and morphology is crucial for improving electrochemical properties. Herein, various unique nanostructured Bi₂S₃ materials with controllable morphology were obtained through a simple and efficient oil bath reaction strategy. Bi₂S₃ with different morphologies can be obtained by regulating the polarity of solvent, and the lattice spacing can also be adjusted. The Bi₂S₃ nanomaterials obtained with ethanol as solvent (BS-3) show a three-dimensional nanoflower-like structure assembled with porous layers. The unique structure facilitates the transport of ions and accommodates the volume variation of Bi₂S₃ during energy storage. Consequently, BS-3 nanoflowers exhibited superior cycling stability and excellent high-rate capability for lithium storage (maintained a high capacity of 923.8 mA h g^-1 after 950 cycles at 1.0 A g^-1) and excellent sodium storage. We provide guidance for precise synthesis and energy storage application of Bi₂S₃ nanomaterials.

A high-capacity self-sacrificial additive based on electroactive sodiated carbonyl groups for sodium-ion batteries

A new type of high-capacity sacrificial additive (Na₄C₆O₆) is proposed to replenish the sodium loss in sodium ion full-cells. The HC//Na₃V₂(PO₄)₂F₃ full-cells demonstrate significantly enhanced energy density after introducing an appropriate amount of additive.

Stability of FeF3-Based Sodium-Ion Batteries in Nonflammable Ionic Liquid Electrolytes at Room and Elevated Temperatures

Iron trifluoride (FeF3), a conversion-type cathode for sodium-ion batteries (SIBs), is based on cheap and abundant Fe and provides high theoretical capacity. However, the applications of FeF3-based SIBs have been hindered by their low-capacity utilization and poor cycling stability. Herein, we report greatly enhanced performance of FeF3 in multiple types of ionic liquid (IL) electrolytes at both room temperature (RT) and elevated temperatures. The Pyr1,4FSI electrolyte demonstrated the best cycling stability with an unprecedented decay rate of only ∼0.023% per cycle after the initial stabilization and an average coulombic efficiency of ∼99.5% for over 1000 cycles at RT. The Pyr1,3FSI electrolyte demonstrated the best cycling stability with a capacity decay rate of only ∼0.25% per cycle at 60 °C. Cells using Pyr1,3FSI and EMIMFSI electrolytes also showed promising cycling stability with capacity decay rates of ∼0.039% and ∼0.030% per cycle over 1000 cycles, respectively. A protective and ionically conductive cathode electrolyte interphase (CEI) layer is formed during cycling in ILs, diminishing side reactions that commonly lead to gassing and excessive CEI growth in organic electrolytes, especially at elevated temperatures. Furthermore, the increased ionic conductivity and decreased viscosity of ILs at elevated temperatures help attain higher accessible capacity. The application of ILs sheds light on designing a protective CEI for its use in stable SIBs.

Synthesis of KVPO4F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

With high theoretical capacity and operating voltage, KVPO₄F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium-oxalate-phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO₄F nanoplates. It is found that the V-F-C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO₄F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO₄F. The as-synthesized KVPO₄F/C cathode delivers a reversible capacity of 106.5 mAh g^-1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g^-1 at the ultrahigh current density of 100 C. In addition, a KVPO₄F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg^-1.

In Situ Fabrication of Porous Cox P Hierarchical Nanostructures on Carbon Fiber Cloth with Exceptional Performance for Sodium Storage

Superior high-rate performance and ultralong cycling life have been constantly pursued for rechargeable sodium-ion batteries (SIBs). In this work, a facile strategy is employed to successfully synthesize porous Co_x P hierarchical nanostructures supported on a flexible carbon fiber cloth (Co_x P@CFC), constructing a robust architecture of ordered nanoarrays. Via such a unique design, porous and bare structures can thoroughly expose the electroactive surfaces to the electrolyte, which is favorable for ultrafast sodium-ion storage. In addition, the CFC provides an interconnected 3D conductive network to ensure firm electrical connection of the electrode materials. Besides the inherent flexibility of the CFC, the integration of the hierarchical structures of Co_x P with the CFC, as well as the strong synergistic effect between them, effectively help to buffer the mechanical stress caused by repeated sodiation/desodiation, thereby guaranteeing the structural integrity of the overall electrode. Consequently, Co_x P@CFC as an anode shows a record-high capacity of 279 mAh g^-1 at 5.0 A g^-1 with almost no capacity attenuation after 9000 cycles.

Realizing outstanding electrochemical performance with Na3V2(PO4)2F3 modified with an ionic liquid for sodium-ion batteries

Na₃V₂(PO₄)₂F₃ is a typical NASICON structure with a high voltage plateau and capacity. Nevertheless, its applications are limited due to its low conductivity and poor rate performance. In this study, nitrogen-boron co-doped carbon-coated Na₃V₂(PO₄)₂F₃ (NVPF-CNB) was prepared by a simple sol-gel method using an ionic liquid (1-vinyl-3-methyl imidazole tetrafluoroborate) as a source of nitrogen and boron for the first time. The morphology and electrochemical properties of NVPF-CNB composites were investigated. The results show that a nitrogen-boron co-doped carbon layer could increase the electron and ion diffusion rate, reduce internal resistance, and help alleviate particle agglomeration. NVPF-CNB-30 exhibited better rate performance under 5C and 10C charge/discharge with initial reversible capacities of 99 and 90 mA h g^-1, respectively. Furthermore, NVPF-CNB-30 illustrates excellent cyclic performance with the capacity retention rate reaching 91.9% after 500 cycles at 5C, as well as a capacity retention rate of about 95.5% after 730 cycles at 10C. The evolution of the material's structure during charge/discharge processes studied by in situ X-ray diffraction confirms the stable structure of nitrogen-boron co-doped carbon-coated Na₃V₂(PO₄)₂F₃. Co-doping of nitrogen and boron also provides more active sites on the surface of Na₃V₂(PO₄)₂F₃, revealing a new strategy for the modification of sodium-ion batteries.

Self-Sacrifice Template Construction of Uniform Yolk-Shell ZnS@C for Superior Alkali-Ion Storage

Secondary batteries have been widespread in the daily life causing an ever-growing demand for long-cycle lifespan and high-energy alkali-ion batteries. As an essential constituent part, electrode materials with superior electrochemical properties play a vital role in the battery systems. Here, an outstanding electrode of yolk-shell ZnS@C nanorods is developed, introducing considerable void space via a self-sacrificial template method. Such carbon encapsulated nanorods moderate integral electronic conductivity, thus ensuring rapid alkali-ions/electrons transporting. Furthermore, the porous structure of these nanorods endows enough void space to mitigate volume stress caused by the insertion/extraction of alkali-ions. Due to the unique structure, these yolk-shell ZnS@C nanorods achieve superior rate performance and cycling performance (740 mAh g^-1 at 1.0 A g^-1 after 540 cycles) for lithium-ion batteries. As a potassium-ion batteries anode, they achieve an ultra-long lifespan delivering 211.1 mAh g^-1 at 1.0 A g^-1 after 5700 cycles. The kinetic analysis reveals that these ZnS@C nanorods with considerable pseudocapacitive contribution benefit the fast lithiation/delithiation. Detailed transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses indicate that such yolk-shell ZnS@C anode is a typical reversible conversion reaction mechanism accomplished by alloying processes. This rational design strategy opens a window for the development of superior energy storage materials.

MoP Quantum Dot-Modified N,P-Carbon Nanotubes as a Multifunctional Separator Coating for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have the advantages of high energy density and low cost and are considered promising next-generation energy storage systems, but the shuttle effect and slow sulfur redox kinetics severely limit their practical applications. Herein, MoP quantum dot-modified N,P-doped hollow PPy substrates are adopted as separator modification coatings for LSBs. The MoP quantum dots exhibit excellent chemisorption and catalytic conversion capabilities for polysulfides, while the N,P-doped PPy substrates can provide flexible channels for Li⁺/electron transport and act as a physical barrier to suppress the shuttle effect. As a result, LSBs assembled with modified separators exhibit excellent rate capability (739 mAh/g at 3 C) and cycle performance (600 mAh/g at 1 C after 600 cycles, 0.052% decay per cycle). Moreover, even under a high sulfur loading of 3.68 mg/cm², areal capacities of 3.58 and 2.92 mAh/cm² for the 1st cycle and 110th cycle are achieved. In addition, according to density functional theory calculations, MoP quantum dots have large adsorption energy for S₈ and Li₂S_n, which further confirms the possibility of lowering the initial nucleation energy barrier of Li₂S and helps to improve the kinetics of the subsequent Li₂S reaction. This study proposes a novel method for using transition-metal phosphides as catalysts in high-performance LSBs.

In Situ Growth of CoS2/ZnS Nanoparticles on Graphene Sheets as an Ultralong Cycling Stability Anode for Potassium Ion Storage

Metal sulfides are promising anodes for potassium-ion batteries (PIBs) due to their high theoretical capacity and abundant active sites; however, their intrinsic low conductivity and poor cycling stability hampered their practical applications. Given this, the rational design of hybrid structures with high stability and fast charge transfer is a critical approach. Herein, CoS₂/ZnS@rGO hybrid nanocomposites were demonstrated with stable cubic phases. The synergistic effect of the obtained bimetallic sulfide nanoparticles and highly conductive 2D rGO nanosheets facilitated excellent long-term cyclability for potassium ion storage. Such hybrid nanocomposites delivered remarkable ultrastable cycling performances in PIBs of 159, 106, and 80 mA h g^-1 at 1, 1.5, and 2 A g^-1 after 1800, 2100, and 3000 cycles, respectively. Moreover, the full-cell configuration with a perylene tetracarboxylic dianhydride organic cathode (CoS₂/ZnS@rGO∥PTCDA) exhibited a better electrochemical performance. Besides, when the CoS₂/ZnS@rGO nanocomposites were applied as an anode for sodium-ion batteries, the electrode demonstrated a reversible charge capacity of 259 mA h g^-1 after 600 cycles at 2 A g^-1. In situ X-ray diffraction and ex situ high-resolution transmission electron microscopy characterizations further confirmed the conversion reactions of CoS₂/ZnS during insertion/desertion processes. Our synthesis strategy is also a general route to other bimetallic sulfide hybrid nanocomposites. This strategy opens up a new roadmap for exploring hybrid nanocomposites with feasible phase engineering for achieving excellent electrochemical performances in energy storage applications.

Sponge-like hierarchical porous carbon decorated by Fe atoms for high-efficiency sodium storage and diffusion

Hierarchical pores with accessible active sites in carbon are highly desired for enhancing sodium storage in sodium ion batteries (SIBs). However, it is still challenging to construct such materials with tunable architectures. Herein, a sponge-like 3D hierarchical porous Fe-doped carbon (Fe@NCS) was successfully assembled from an energetic framework. The continuous distribution of micro/meso/macro-pores in the range of 5 nm-2 μm and homogenously decorated Fe atoms were achieved, which greatly enhanced the storage and diffusion of Na⁺ ions and displayed brilliant high-rate capability and cycling stability.

Mg2+-Doping Constructed a Continuous and Homogeneous Cathode-Electrolyte Interphase Film on Na3.12Fe2.44(P2O7)2 with Superior and Stable High-Temperature Performance for Sodium-Ion Storage

Sodium-ion batteries (SIBs) are on the verge of achieving practical applications, and the key is to find suitable electrode materials. The polyanionic iron-based material Na_3.12Fe_2.44(P₂O₇)₂ (NFPO) possesses an open three-dimensional framework structure with good thermal stability and is regarded as an outstanding cathode material for SIBs. Nevertheless, its poor electrical conductivity, problems with erosion of electrolytes, and structural deterioration during cycling still need to be urgently addressed. Here, we first design a Mg²⁺-doped NFPO (NFPO-Mg) material with a dual-action effect. On the one hand, Mg²⁺ improves the intrinsic conductivity of the NFPO material, and on the other hand, Mg²⁺ promotes the formation of a homogeneous and stable cathode-electrolyte interphase film during the cycling process, which results in a superior rate performance and cycling stability. A capacity of 68.6 mAh g^-1 was achieved at 50C (1C = 117.4 mAh g^-1), and a capacity retention of 79.1% was maintained after 3000 cycles at 20C. More impressively, NFPO-Mg exhibits outstanding high-temperature electrochemical performance, with a capacity retention of 95.3% after 400 cycles at 10C at 60 °C (much higher than the 54.2% for the NFPO). This paper explores an effective method for improving the electrochemical performance of cathode materials, which may prove instrumental in guiding the design of more high-performance cathode materials in the future.

Enhancing the Areal Capacity and Stability of Cu2ZnSnS4 Anode Materials by Carbon Coating: Mechanistic and Structural Studies During Lithiation and Delithiation

The widespread use of energy storage technologies has created a high demand for the development of novel anode materials in Li-ion batteries (LIBs) with high areal capacity and faster electron-transfer kinetics. In this work, carbon-coated Cu₂ZnSnS₄ with a hierarchical 3D structure (CZTS@C) is used as an anode material for LIBs. The CZTS@C microstructures with enhanced electrical conductivity and improved Li-ion diffusivity exhibit high areal and gravimetric capacities of 2.45 mA h/cm² and 1366 mA h/g, respectively. The areal capacity achieved in the present study is higher than that of previously reported CZTS-based materials. Moreover, in situ X-ray diffraction results show that lithium ions are stored in CZTS through the insertion reaction, followed by the alloying and conversion reactions at ∼1 V. The structural evolution of Li₂S and Cu-Sn/Cu-Zn alloy phases occurs during the conversion and alloying reactions. The present work provides a cost-effective and simple method to prepare bulk CZTS and highlights the conformal carbon coating over CZTS, which can enhance the electrical and ionic conductivities of CZTS materials and increase the mass loading (1-2.3 mg/cm²). The improved stability and rate capability of CZTS@C anode materials can therefore be achieved.

Sodium-Ion Battery with a Wide Operation-Temperature Range from -70 to 100 °C

Sodium-ion batteries (SIBs), as one of the potential candidates for grid-scale energy storage systems, are required to tackle extreme weather conditions. However, the all-weather SIBs with a wide operation-temperature range are rarely reported. Herein, we propose a wide-temperature range SIB, which involves a carbon-coated Na₄ Fe₃ (PO₄ )₂ P₂ O₇ (NFPP@C) cathode, a bismuth (Bi) anode, and a diglyme-based electrolyte. We demonstrate that solvated Na⁺ can be directly stored by the Bi anode via an alloying reaction without the de-solvent process. Furthermore, the NFPP@C cathode exhibits a high Na⁺ diffusion coefficient at low temperature. As a result, the Bi//NFPP@C battery exhibits perfect low-temperature behavior. Even at -70 °C, this battery still delivers 70.19 % of the room-temperature capacity. Furthermore, benefitting from the high boiling point of the electrolyte, this battery also works well at a high temperature of up to 100 °C. These results are encouraging for the further exploration of wide-temperature range SIBs.

Graphene-Supported Naphthalene-Based Polyimide Composite as a High-Performance Sodium Storage Cathode

Electroactive acid anhydride with multicarbonyl is highly promising for electrochemical energy storage because of its high specific capacity and environmental benignity. Its low electrical conductivity and high dissolution in organic electrolyte, however, result in poor cycling and rate capabilities. Here, we report a naphthalene polyimide derivative (NPI) synthesized by using anhydride under condensation polymerization conditions, along with its composite with graphene (NPI-G) fabricated via in situ polymerization. The composite delivers a high reversible capacity and outstanding cycling stability and rate capability as a cathode for sodium-ion batteries (SIBs) owing to the formation of a polymer, the improvement in the electrical conductivity brought about by the highly dispersed graphene sheets, and the enhancement of structural stability resulting from the π-π stacking interaction between the phenyl groups of NPI and the six-member carbon rings of graphene. This investigation sheds light on the development, design, and screening of next-generation organic electrode materials with high performance for SIBs.

Co-Construction of Solid Solution Phase and Void Space in Yolk-Shell Fe0.4Co0.6S@N-Doped Carbon to Enhance Cycling Capacity and Rate Capability for Aluminum-Ion Batteries

Rechargeable aluminum-ion batteries (AIBs), using low-cost and inherent safety Al metal anodes, are regarded as promising energy storage devices next to lithium-ion batteries. Currently, one of the greatest challenges for AIBs is to explore cathodes suitable for feasible Al³⁺ insertion/extraction with high structure stability. Herein, a facile co-engineering on solid solution phase and cavity structure is developed via Prussian blue analogues by a simple and facile sulfidation strategy. The obtained uniform yolk-shell Fe_0.4Co_0.6S@N-doped carbon nanocages (y-s Fe_0.4Co_0.6S@NC) display a high reversible capacity of 141.3 mA h g^-1 at 500 mA g^-1 after 100 cycles and a good rate capability of 100.9 mA h g^-1 at 1000 mA g^-1. The improved performance can be mainly ascribed to the dual merits of the composite; that is, more negative Al³⁺ formation energy and improved Al³⁺ diffusion kinetics favored by the solid solution phase and Al³⁺ insertion/extraction accommodable space stemmed from the yolk-shell structure. Moreover, the reaction mechanism study discloses that the reaction involves the intercalation of Al³⁺ ions into Fe_0.4Co_0.6S to generate Al_lFe_mCo_nS and elemental Fe and Co.

Dual-Type Carbon Confinement Strategy: Improving the Stability of CoTe2 Nanocrystals for Sodium-Ion Batteries with a Long Lifespan

Sodium-ion batteries have great potential to become large-scale energy storage devices due to their abundant and low-cost resources. However, the lack of anode and cathode materials with both high energy density and long-term cycling performance significantly affects their commercial applications. In this work, uniform CoTe₂ nanoparticles are generated from the tellurization of Co nanoparticles, which were coated with polyvinylpyrrolidone in a three-dimensional (3D) porous carbon matrix (CoTe₂@3DPNC). Finally, a dual-type carbon confinement structure is formed after tellurization during which citric acid is adopted as the source of the inner carbon scaffold. The hierarchical carbon matrix not only builds a robust and fast ion/electronic conductive 3D architecture but also mitigates the volume expansion and aggregation of CoTe₂ during sodium insertion/extraction. Remarkably, the CoTe₂@3DPNC electrode displays a high reversible capacity (216.5 mAh g^-1/627.9 mAh cm^-3 at 0.2 A g^-1 after 200 cycles) and outstanding long-term cycling performance (118.1 mAh g^-1/342.5 mAh cm^-3 even at 5.0 A g^-1 after 2500 cycles). Kinetics tests and capacitance calculations clearly reveal a battery-capacitive dual-model Na-storage mechanism. Furthermore, ex situ XRD/SEM/TEM demonstrate superior stability during sodium insertion/extraction. This work provides a valuable strategy for the rational structural design of long-life electrodes for advanced rechargeable batteries.

Heterostructure engineering of ultrathin SnS2/Ti3C2Tx nanosheets for high-performance potassium-ion batteries

Layered metal sulfides are considered as promising candidates for potassium ion batteries (KIBs) owing to the unique interlayer passages for ion diffusion. However, the insufficient electronic conductivity, inevitable volume expansion, and sulfur loss hinder the promotion of K-ion storage performance. Herein, few-layered Ti₃C₂T_x nanosheets were selected as the multi-functional substrate for cooperating few-layered SnS₂ nanosheets, constructing SnS₂/Ti₃C₂T_x hetero-structural nanosheets (HNs) with the thickness as thin as about 5 nm. In this configuration, the formed Ti-S bonds provide robust interaction between SnS₂ and Ti₃C₂T_x nanosheets, which hinders the agglomeration of SnS₂ and the restack of Ti₃C₂T_x, endowing the hybrid material with robust nanostructure. Thus, the shortcomings of the SnS₂ anode are muchly relieved. In this way, the as-prepared SnS₂/Ti₃C₂T_x HNs electrode delivers reversible capacities of 462.1 mAh g^-1 at 0.1 A g^-1 and 166.1 mAh g^-1 at 2.0 A g^-1, respectively, and a capacity of 85.5 mAh g^-1 is remained even after 460 cycles at 2.0 A g^-1. These results are superior to those of the counterpart electrode, confirming aggressive promotion of K-ion storage performance of SnS₂ anode brought by the cooperation of Ti₃C₂T_x, and presenting a reliable strategy to improve the electrochemical performance of sulfide anodes.

Phosphorus–carbon covalent bond induced kinetics modulation of vanadium diphosphide for room- and high-temperature sodium-ion batteries

The electrochemical kinetics of vanadium diphosphide is regulated by the phosphorus–carbon covalent bond to boost the sodium storage performance.

Phosphorus Doping Induced the Co-Construction of Sulfur Vacancies and Heterojunctions in Tin Disulfide as a Durable Anode for Lithium/Sodium-Ion Batteries

The reasonable design of electrode materials with heterojunction and vacancy is a promising strategy to elevate its electrochemical performances. Herein, tin-based sulfide composites with heterojunction and sulfur vacancy encapsulated by...

Investigation of pyrolysed anthracite as an anode material for sodium ion batteries

Due to the increasingly serious problems of the greenhouse effect and environmental pollution caused by the continuous consumption of traditional fossil energy, renewable and clean energy (such as solar energy and wind energy) is facing new opportunities and challenges.

Nickel Ferrocyanides for Aqueous Ammonium Ion Batteries

In this report, we design a structural optimization in Ni2Fe(CN)6 through a partial substitution of nickel by sodium, and investigate the electrochemical performance of a series of Na2xNi2-xFe(CN)6 (x =...

Cotton textile inspires MoS2@reduced graphene oxide anodes towards high-rate capability or long-cycle stability sodium/lithium-ion batteries

Textile-based electrodes show superior energy storage performances, including high-rate capability for Na-ion batteries and long-cycling stability for Li-ion batteries, as elucidated by morphology differences that sodiation/desodiation brings intense nanomachine effect.

Manipulating the Phase Compositions of Na3(VO1-xPO4)2F1+2x (0 ≤ x ≤ 1) and Their Synergistic Effects with Reduced Graphene Oxide toward High-Rate Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have aroused intense research and academic interest due to the natural abundance and cost-effectiveness of sodium resources. Presently, cathode materials based on the Na₃(VO_1-xPO₄)₂F_1+2x (0 ≤ x ≤ 1, NVPF_1+2x) polyanionic framework show intriguing electrochemical performances toward practical and advanced SIBs due to its high operating voltage (>3.9 V) and high energy density (>500 Wh kg^-1). Different from conventional approaches focusing on delicate morphology design, metal ion substitution, and the conductive matrix's incorporation to overcome the low intrinsic electrical conductivity, here we adopt a one-step microwave-assisted hydrothermal approach to optimize the electrochemical performances of NVPF_1+2x via manipulating its phase compositions with different vanadium sources and distinguishing the tetragonal (I4/mmm) symmetry of the Na₃(VOPO₄)₂F phase from the orthorhombic symmetry (Amam) of the Na₃V₂(PO₄)₂F₃ phase. The introduction of the conductive reduced graphene oxide (rGO) framework and its impacts on the phase compositions were systematically investigated. The rGO framework with different calcination temperature can alter the phase composition and the electrical conductivity of NVPF_1+2x cathodes significantly, thus having a great impact on their electrochemical performances. Galvanostatic charge/discharge, cyclic voltammetry, electrochemical impedance spectroscopy, and the galvanostatic intermittent titration technique are adopted to compare their electrode polarization and kinetics difference and show that NVPF@rGO-600 °C possesses a high rate, small polarization, and fast kinetics electrochemical properties. This work provides new insights into manipulating phase compositions of the NVPF_1+2x cathode by modulating the synthesis conditions and revealing their synergistic effect with a rGO conductive framework toward a superior rate capability and more realistic practical applications for SIBs.