Superior Na-ion storage properties of high aspect ratio SnSe nanoplates prepared by a spray pyrolysis process

Black phosphorene/SnSe van der Waals heterostructure as a promising anchoring anode material for metal-ion batteries

Black phosphorene (BP) is a glowing two-dimensional semiconducting layer material for cutting-edge microelectronics, with high carrier mobility and thickness-dependent band gap. Here, based on van der Waals (vdW)-corrected first-principles approaches, we investigated stacked BP/tin selenide (BP/SnSe) vdW heterostructure as an anode material for metal ion batteries, which exhibits a significant theoretical capacity, along with relatively durable binding strength compared to the constituent BP and SnSe monolayers. Our calculations demonstrated that the Li/Na adatom favors insertion into the interlayer region of BP/SnSe vdW heterostructure owing to synergistic interfacial effect, resulting in comparable diffusivity to the BP and SnSe monolayers. Subsequently, the theoretical specific capacities for Li/Na are found to be as high as 956.30 mAhg-1and 828.79 mAhg-1, respectively, which could be attributed to the much higher storage capacity of Li/Na adatoms in the BP/SnSe vdW heterostructure. Moreover, the electronic structure calculations reveal that a large amount of charge transfer assists in semiconductor-to-metallic transition upon lithiation/sodiation, ensuring good electrical conductivity. These simulations verify that the BP/SnSe vdW heterostructure has immense potential for application in the design of metal-ion battery technologies.

Optimized crystal orientation for enhanced reaction kinetics and reversibility of SnSe/NC hollow nanospheres towards high-rate and long-term lithium/sodium storage

The development of anode materials with high theoretical capacity and cycling stability is very important for the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, SnSe/NC hollow nanospheres with different crystal orientations were prepared by regulating the high-temperature selenization of the PDA@SnO2 precursor for lithium/sodium storage. In SnSe/NC hollow nanospheres, the physical buffering and chemical bonding of the nitrogen carbon matrix and SnSe nanoparticles could inhibit volume expansion and polyselenide loss, thus maintaining long-term structural stability. More importantly, electrochemical tests and DFT calculations show that the diffusion energy barrier of Li+/Na+ is significantly reduced at the SnSe (400) rather than the usual (111) facet, which is conducive to the uniformity of ion insertion into SnSe, thus effectively enhancing the reaction kinetics and reversibility of lithium/sodium storage. Therefore, SnSe/NC hollow nanospheres with rich SnSe (400) and good dispersion formed at 550 °C delivered the best reversible specific capacity and rate performance. After a long period of 900 cycles, the capacity retention of lithium/sodium ion batteries is close to 84.88% and 77.05%, respectively. Our findings provide valuable insights into the design of metal selenides for advanced LIBs/SIBs.

SnSe Nanosheet Array on Carbon Cloth as a High-Capacity Anode for Sodium-Ion Batteries

Binder-free electrodes offer a great opportunity for developing high-performance sodium-ion batteries (SIBs) aiming at the application in energy storage devices. Tin selenide (SnSe) is considered to be a promising anode material for SIBs owing to its high theoretical capacity (780 mA h g-1). In this work, a SnSe nanosheet array (SnSe NS) on a carbon cloth is prepared using a vacuum thermal evaporation method. The as-prepared SnSe NS electrode does not have metal current collectors, binders, or any conductive additives. In comparison with the electrode of SnSe blocky particles (SnSe BP), the SnSe NS electrode delivers a higher initial charge capacity of 713 mA h g-1 at a current density of 0.1C and maintains a higher charge capacity of 410 mA h g-1 after 50 cycles. Furthermore, the electrochemical behaviors of the SnSe NS electrode are determined via pseudocapacitance and electrochemical impedance spectroscopy measurements, indicating a faster kinetic process of the SnSe NS electrode compared to that of the SnSe BP. Operando X-ray diffraction measurements prove that the SnSe NS exhibits better phase reversibility than the SnSe BP. After the cycles, the SnSe NS electrode still maintains its particular structure. This work provides a feasible method to prepare SnSe nanostructures with high capacity and improved sodium ion diffusion ability.

Advances and challenges in metal selenides enabled by nanostructures for electrochemical energy storage applications

The development of nanomaterials and their related electrochemical energy storage (EES) devices can provide solutions for improving the performance and development of existing EES systems owing to their high electronic conductivity and ion transport and abundant embeddable sites. Recent progress has demonstrated that metal selenides are attracting increasing attention in the field of EES because of their unique structures, high theoretical capacities, rich element resources, and high conductivity. However, there are still many challenges in their application in EES, and thus the use of nanoscale metal selenide materials in commercial devices is limited. In this review, we summarize recent advances in the nanostructured design of metal selenides (e.g., zero-, one-, two-, and three-dimensional, and self-supported structures) and present their advantages in terms of EES performance. Moreover, some remarks on the potential challenges and research prospects of nanostructured metal selenides in the field of EES are presented.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Conversion-Alloying Anode Materials for Sodium Ion Batteries

The past decade has witnessed a rapidly growing interest toward sodium ion battery (SIB) for large-scale energy storage in view of the abundance and easy accessibility of sodium resources. Key to addressing the remaining challenges and setbacks and to translate lab science into commercializable products is the development of high-performance anode materials. Anode materials featuring combined conversion and alloying mechanisms are one of the most attractive candidates, due to their high theoretical capacities and relatively low working voltages. The current understanding of sodium-storage mechanisms in conversion-alloying anode materials is presented here. The challenges faced by these materials in SIBs, and the corresponding improvement strategies, are comprehensively discussed in correlation with the resulting electrochemical behavior. Finally, with the guidance and perspectives, a roadmap toward the development of advanced conversion-alloying materials for commercializable SIBs is created.

Research Progress of Single-Crystal Nickel-Rich Cathode Materials for Lithium Ion Batteries

Single-crystal nickel-rich cathode materials (SC-NRCMs) are the most promising candidates for next-generation power batteries which enable longer driving range and reliable safety. In this review, the outstanding advantages of SC-NRCMs are discussed systematically in aspects of structural and thermal stabilities. Particularly, the intergranular-crack-free morphology exhibits superior cycling performance and negligible parasitic reactions even under severe conditions. Besides, various synthetic methods are summarized and the relation between precursor, sintering process, and final single-crystal products are revealed, providing a full view of synthetic methods. Then, challenges of SC-NRCMs in fields of kinetics of lithium diffusion and the one particularly occurred at high voltage (intragranular cracks and aggravated parasitic reactions) are discussed. The corresponding mechanism and modifications are also referred. Through this review, it is aimed to highlight the magical morphology of SC-NRCMs for application perspective and provide a reference for following researchers.

Yolk-Shell-Structured Nanospheres with Goat Pupil-Like S-Doped SnSe Yolk and Hollow Carbon-Shell Configuration as Anode Material for Sodium-Ion Storage

Rationally nanostructured electrode materials exhibit excellent sodium-ion storage performance. In particular, yolk-shell configurations of metal chalcogenide@void@C are introduced in various synthetic strategies for use as superior anode materials. Herein, yolk-shell-structured nanospheres, with goat pupil-like configuration of S-doped SnSe yolks and hollow carbon shells, are synthesized by salt-infiltration and a simple post-treatment procedure. Impressively, the co-infiltration of thiourea and selenium oxide enables the doping of sulfur into SnSe (SnSeS) and carbon shells, as well as the formation of a goat pupil-like yolk-shell architecture. High-reactivity thiourea-derived H₂ S gas forms nanocrystals inside the carbon nanospheres. The nanocrystals act as seeds for the crystal growth of SnSeS through Ostwald ripening. The unique yolk-shell structure and composition with a heterointerface provide not only structural stability but also fast electrode reaction kinetics during repeated cycling. The SnSeS@C electrode shows an excellent cycle life (186 mA h g^-1 for 1000 cycles at 0.5 A g^-1 ) and rate capability (112 mA h g^-1 at 5.0 A g^-1 ).

SeC Bonding Promoting Fast and Durable Na+ Storage in Yolk-Shell SnSe2 @SeC

Tin-based compounds have received much attention as anode materials for lithium/sodium ion batteries owing to their high theoretical capacity. However, the huge volume change usually leads to the pulverization of electrode, giving rise to a poor cycle performance, which have severely hampered their practical application. Herein, highly durable yolk-shell SnSe₂ nanospheres (SnSe₂ @SeC) are prepared by a multistep templating method, with an in situ gas-phase selenization of the SnO₂ @C hollow nanospheres. During this process, Se can be doped into the carbon shell with a tunable amount and form SeC bonds. Density functional theory calculation results reveal that the SeC bonding can enhance the charge transfer properties as well as the binding interaction between the SnSe₂ core and the carbon shell, favoring an improved rate performance and a superior cyclability. As expected, the sample delivers reversible capacities of 441 and 406 mAh g^-1 after 2000 cycles at 2 and 5 A g^-1 , respectively, as the anode material for a sodium-ion battery. Such performances are significantly better than the control sample without the SeC bonding and also other metal selenide-based anodes, evidently showing the advantage of Se doping in the carbon shell.

Dynamic Epitaxial Crystallization of SnSe2 on the Oxidized SnSe Surface and Its Atomistic Mechanisms

Surface oxidation of SnSe sharply reduces its thermoelectric properties though the bulk single-crystalline materials of SnSe claim the record high zT values. Investigation on the oxidation behaviors of SnSe together with the subsequent phase transition and element migration is fundamentally important to maintaining the ultrahigh zT values, with a potential for further improvement. In this work, we disclose the dynamic epitaxial crystallization of SnSe2 on the amorphous surface of partially oxidized SnSe crystals and the corresponding atomistic mechanisms via transmission electron microscopy (TEM). It is revealed that the thermally annealed amorphous surface crystallized to SnO2 and SnSe2 in the outermost and secondary layers, respectively, forming distinctive SnSe/SnSe2/SnO2 multilayer heterostructures with specific orientation relationships between the two selenides. By means of in situ scanning TEM (STEM), the dynamic epitaxial crystallization process of SnSe2 was revealed when the oxidized SnSe surface was subjected to electron beam irradiation. Through the atomic-scale characterization and modeling analysis, we find that the exposed dangling Se diatoms on the SnSe surface serve as nucleation sites for lateral epitaxial crystallization of SnSe2. The same valence and similar coordination configuration of Se atoms in these two phases are supposed to facilitate the sharing of Se atoms, with lattice distortions in the SnSe2/SnSe interface. These findings are valuable for understanding the surface oxidation behavior of SnSe and revealing the interface structures of SnSe2/SnSe heterojunctions and also offering new routes for SnSe-related multilayer or heterostructure system design.

A highly-effective nitrogen-doped porous carbon sponge electrode for advanced K–Se batteries

A rechargeable K–Se battery is emerging as an energy storage system because of its much higher specific capacity than that of the traditional alkali metal-ion batteries, but is facing some critical issues and challenges.

Sn-C and Se-C Co-Bonding SnSe/Few-Layered Graphene Micro-Nano Structure: Route to a Densely Compacted and Durable Anode for Lithium/Sodium-Ion Batteries

Developing anodes with a high and stable energy density for both gravimetric and volumetric storage is vital for high-performance lithium/sodium-ion batteries. Herein, an SnSe/few-layered graphene (FLG) composite with a high tap density (2.3 g cm^-3) is synthesized via the plasma-milling method, in which SnSe nanoparticles are strongly bound with the FLG matrix, owing to both Sn-C and Se-C bonds, to form nanosized primary particles and then assemble to microsized secondary granules. The FLG can effectively alleviate the large stress generated from the volume expansion of SnSe during cycling based on its superstrength. Furthermore, as demonstrated by the density-functional theory calculations, the Sn-C and Se-C co-bonding benefitting from the formation of substantial vacancy defects on the P-milling-synthesized FLG enables strong affinity between SnSe nanoparticles and the FLG matrix, preventing SnSe from aggregating and detaching even after long-term cycling. As an anode for lithium-ion batteries, it exhibits high gravimetric and volumetric capacities (864.8 mAh g^-1 and 1990 mAh cm^-3 at 0.2 A g^-1), a high rate (612.6 mAh g^-1 even at 5.0 A g^-1), and the longest life among the reported SnSe-based anodes (capacity retention of 92.8% after 2000 cycles at 1.0 A g^-1). Subsequently, an impressive cyclic life (capacity retention of 91.6% after 1000 cycles at 1.0 A g^-1) is also achieved for sodium-ion batteries. Therefore, the SnSe/FLG composite is a promising anode for high-performance lithium/sodium-ion batteries.

Advances in nanostructures fabricated via spray pyrolysis and their applications in energy storage and conversion

This review provides insight into various nanostructures designed by spray pyrolysis and their applications in energy storage and conversion.

Yolk–shell structured SnSe as a high-performance anode for Na-ion batteries

Yolk–shell structured SnSe nanoparticles have been investigated as anode materials in Na-ion batteries for the first time, and exhibit excellent Na⁺ storage performance.

Three-dimensional hierarchical Ni3Se2 nanorod array as binder/carbon-free electrode for high-areal-capacity Na storage

A three-dimensional hierarchical Ni3Se2 nanorod array (NA) grown in situ on foam Ni is the first to act as a carbon/binder-free electrode of SIBs via a one-step reversible conversion reaction. By a special decomposition-fusion process, the morphology and composition of the NA are regulated to obtain ultrahigh areal capacity, which is three times greater than that reported for other metal selenides.

Lithium-ion storage performances of sunflower-like and nano-sized hollow SnO2 spheres by spray pyrolysis and the nanoscale Kirkendall effect

Nanostructured metal selenides with a variety of morphologies are crucial for fabricating porous, hollow metal-oxide nanomaterials by nanoscale Kirkendall diffusion. Herein, SnSe-SnO2 composite powders and SnSe nanospheres were synthesized via one-pot spray pyrolysis by optimizing the concentration of the Se precursor in the spray solution; these were then used to fabricate sunflower-like SnO2 and hollow SnO2 nanospheres, respectively, via nanoscale Kirkendall diffusion. Post-treatment of the SnSe-decorated SnO2 under air produced sunflower-like SnO2, in which ray and disk florets consisting of hollow nanoplates and dense nanospheres, respectively, were present. The mean diameter of the homogeneous hollow SnO2 nanospheres was 150 nm. The hollow morphology shortens the diffusion length, increasing the contact area between the electrolyte and voids and buffering large volume changes during repeated cycling. As anode materials for lithium-ion batteries, the hollow SnO2 nanospheres showed excellent cycling and rate performances. The discharge capacity of the hollow SnO2 nanospheres, after 500 cycles from 0.001 V to 3.0 V, was 1043 mA h g-1, at a current density of 3.0 A g-1. The hollow SnO2 nanospheres showed a high reversible capacity of 638 mA h g-1, even at current density as high as 10 A g-1.

The State and Challenges of Anode Materials Based on Conversion Reactions for Sodium Storage

Sodium-ion batteries (SIBs) have huge potential for applications in large-scale energy storage systems due to their low cost and abundant sources. It is essential to develop new electrode materials for SIBs with high performance in terms of energy density, cycle life, and cost. Metal binary compounds that operate through conversion reactions hold promise as advanced anode materials for sodium storage. This Review highlights the storage mechanisms and advantages of conversion-type anode materials and summarizes their recent development. Although conversion-type anode materials have high theoretical capacities and abundant varieties, they suffer from multiple challenging obstacles to realize commercial applications, such as low reversible capacity, large voltage hysteresis, low initial coulombic efficiency, large volume changes, and low cycling stability. These key challenges are analyzed in this Review, together with emerging strategies to overcome them, including nanostructure and surface engineering, electrolyte optimization, and battery configuration designs. This Review provides pertinent insights into the prospects and challenges for conversion-type anode materials, and will inspire their further study.

A Dealloying Synthetic Strategy for Nanoporous Bismuth-Antimony Anodes for Sodium Ion Batteries

Metal-based anodes have recently aroused much attention in sodium ion batteries (SIBs) owing to their high theoretical capacities and low sodiation potentials. However, their progresses are prevented by the inferior cycling performance caused by severe volumetric change and pulverization during the (de)sodiation process. To address this issue, herein an alloying strategy was proposed and nanoporous bismuth (Bi)-antimony (Sb) alloys were fabricated by dealloying of ternary Mg-based precursors. As an anode for SIBs, the nanoporous Bi₂Sb₆ alloy exhibits an ultralong cycling performance (10 000 cycles) at 1 A/g corresponding to a capacity decay of merely 0.0072% per cycle, due to the porous structure, alloying effect and proper Bi/Sb atomic ratio. More importantly, a (de)sodiation mechanism ((Bi,Sb) ↔ Na(Bi,Sb) ↔ Na₃(Bi,Sb)) is identified for the discharge/charge processes of Bi-Sb alloys by using operando X-ray diffraction and density functional theory calculations.

Tin Selenide (SnSe): Growth, Properties, and Applications

The indirect bandgap semiconductor tin selenide (SnSe) has been a research hotspot in the thermoelectric fields since a ZT (figure of merit) value of 2.6 at 923 K in SnSe single crystals along the b-axis is reported. SnSe has also been extensively studied in the photovoltaic (PV) application for its extraordinary advantages including excellent optoelectronic properties, absence of toxicity, cheap raw materials, and relative abundance. Moreover, the thermoelectric and optoelectronic properties of SnSe can be regulated by the structural transformation and appropriate doping. Here, the studies in SnSe research, from its evolution to till now, are reviewed. The growth, characterization, and recent developments in SnSe research are discussed. The most popular growth techniques that have been used to prepare SnSe materials are discussed in detail with their recent progress. Important phenomena in the growth of SnSe as well as the problems remaining for future study are discussed. The applications of SnSe in the PV fields, Li-ion batteries, and other emerging fields are also discussed.

Multi-Layer SnSe Nanoflake Field-Effect Transistors with Low-Resistance Au Ohmic Contacts

We report p-type tin monoselenide (SnSe) single crystals, grown in double-sealed quartz ampoules using a modified Bridgman technique at 920 °C. X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) measurements clearly confirm that the grown SnSe consists of single-crystal SnSe. Electrical transport of multi-layer SnSe nanoflakes, which were prepared by exfoliation from bulk single crystals, was conducted using back-gated field-effect transistor (FET) structures with Au and Ti contacts on SiO₂/Si substrates, revealing that multi-layer SnSe nanoflakes exhibit p-type semiconductor characteristics owing to the Sn vacancies on the surfaces of SnSe nanoflakes. In addition, a strong carrier screening effect was observed in 70-90-nm-thick SnSe nanoflake FETs. Furthermore, the effect of the metal contacts to multi-layer SnSe nanoflake-based FETs is also discussed with two different metals, such as Ti/Au and Au contacts.

Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high-energy SIBs. In this review, the recent research progress of alloy-type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy-based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed.

Ultrathin Layered SnSe Nanoplates for Low Voltage, High-Rate, and Long-Life Alkali-Ion Batteries

2D electrode materials with layered structures have shown huge potential in the fields of lithium- and sodium-ion batteries. However, their poor conductivity limits the rate performance and cycle stability of batteries. Herein a new colloid chemistry strategy is reported for making 2D ultrathin layered SnSe nanoplates (SnSe NPs) for achieving more efficient alkali-ion batteries. Due to the effect of weak Van der Waals forces, each semiconductive SnSe nanoplate stacks on top of each other, which can facilitate the ion transfer and accommodate volume expansion during the charge and discharge process. This unique structure as well as the narrow-bandgap semiconductor property of SnSe simultaneously meets the requirements of achieving fast ionic and electronic conductivities for alkali-ion batteries. They exhibit high capacity of 463.6 mAh g^-1 at 0.05 A g^-1 for Na-ion batteries and 787.9 mAh g^-1 at 0.2 A g^-1 for Li-ion batteries over 300 cycles, and also high stability for alkali-ion batteries.

One-step synthesis of SnCo nanoconfined in hierarchical carbon nanostructures for lithium ion battery anode

A new strategy for the one-step synthesis of a 0D SnCo nanoparticles-1D carbon nanotubes-3D hollow carbon submicrocube cluster (denoted as SnCo@CNT-3DC) hierarchical nanostructured material was developed via a simple chemical vapor deposition (CVD) process with the assistance of a water-soluble salt (NaCl). The adopted NaCl not only acted as a cubic template for inducing the formation of the 3D hollow carbon submicrocube cluster but also provides a substrate for the SnCo catalysts impregnation and CNT growth, ultimately leading to the successful construction of the unique 0D-1D-3D structured SnCo@CNT-3DC during the CVD of C₂H₂. When utilized as a lithium-ion battery anode, the SnCo@CNT-3DC composite electrode demonstrated an excellent rate performance and cycling stability for Li-ion storage. Specifically, an impressive reversible capacity of 826 mA h g^-1 after 100 cycles at 0.1 A g^-1 and a high rate capacity of 278 mA h g^-1 even after 1000 cycles at 5 A g^-1 were achieved. This remarkable electrochemical performance could be ascribed to the unique hierarchical nanostructure of SnCo@CNT-3DC, which guarantees a deep permeation of electrolytes and a shortened lithium salt diffusion pathway in the solid phase as well as numerous hyperchannels for electron transfer.

MoSe2 Embedded CNT-Reduced Graphene Oxide Composite Microsphere with Superior Sodium Ion Storage and Electrocatalytic Hydrogen Evolution Performances

Highly porous MoSe₂-reduced graphene oxide-carbon nanotube (MoSe₂-rGO-CNT) powders were prepared by a spray pyrolysis process. The synergistic effect of CNTs and rGO resulted in powders containing ultrafine MoSe₂ nanocrystals with a minimal degree of stacking. The initial discharge capacities of MoSe₂-rGO-CNT, MoSe₂-CNT, MoSe₂-rGO, and bare MoSe₂ powders for sodium ion storage were 501.6, 459.7, 460.2, and 364.0 mA h g^-1, respectively, at 1.0 A g^-1. The MoSe₂-rGO-CNT composite powders had superior cycling and rate performances compared with the MoSe₂-CNT, MoSe₂-rGO composite, and bare MoSe₂ powders. The electrocatalytic activity of MoSe₂-rGO-CNT in the hydrogen evolution reaction (HER) was also compared with that of MoSe₂-CNT, MoSe₂-rGO, and bare MoSe₂. MoSe₂-rGO-CNT composite powders exhibited an overpotential of 0.24 V at a current density of 10 mA cm^-2, which was less than that of MoSe₂-CNT (0.26 V at 10 mA cm^-2), MoSe₂-rGO (0.32 V at 10 mA cm^-2), and bare MoSe₂ (0.33 V at 10 mA cm^-2). Tafel slopes for the MoSe₂-rGO-CNT, MoSe₂-CNT, MoSe₂-rGO, and bare MoSe₂ powders were 53, 76, 86, and 115 mV dec^-1, respectively. Because a large electrochemical surface area and ultrafine MoSe₂ nanocrystals, the MoSe₂-rGO-CNT composite possesses more active sites than the MoSe₂-CNT, MoSe₂-rGO composite, and bare MoSe₂ powders with extensive stacking and large crystalline size, which provide greater catalytic HER activity.

NiSe2 Nanooctahedra as an Anode Material for High-Rate and Long-Life Sodium-Ion Battery

In this article, we report NiSe₂ nanooctahedra as a promising anode material for sodium-ion batteries (SIBs). They exhibit outstanding long-term cyclic stability (313 mAh/g after 4000 cycles at 5 A/g) and excellent high-rate capability (175 mAh/g at 20 A/g). Besides, the initial Coulombic efficiency of NiSe₂ is also very impressive (over 90%). Such remarkable performances are attributed to good conductivity, structural stability, and the pseudocapacitive behavior of the NiSe₂. Furthermore, the sodium ion storage mechanism of NiSe₂ is first investigated by in situ XRD and ex situ XRD. These highlights give NiSe₂ a competitive strength for rechargeable SIBs.

Improved sodium-ion storage properties by fabricating nanoporous CuSn alloy architecture

A CuSn alloy with nanoporous structure has been developed for use as the anode in sodium-ion batteries.