Metal Selenides Research Articles

Superhydrophilic and Underwater Superaerophobic Dual-Function Peony-Shaped Selenide Micro-nano Array Self-Supported Electrodes for High-Efficiency Overall Water Splitting Driven by Renewable Energy.

With the intensification of global environmental pollution and resource scarcity, hydrogen has garnered significant attention as an ideal alternative to fossil fuels due to its high energy density and nonpolluting nature. Consequently, the urgent development of electrocatalytic water-splitting electrodes for hydrogen production is imperative. In this study, a superwetting selenide catalytic electrode with a peony-flower-shaped micronano array (MoS2/Co0.8Fe0.2Se2/NixSey/nickel foam (NF)) was synthesized on NF via a two-step hydrothermal method. The optimal catalytic activity of cobalt-iron selenide was achieved by adjusting the Co/Fe ratio. The intrinsic catalytic activity of the electrodes was enhanced by incorporating transition metal selenides, which then served as a precursor for the subsequent loading of MoS2 nanoflowers on the surface to fully expose the active sites. Furthermore, the superwetting properties of the electrode accelerated electrolyte penetration and electron/mass transfer, while also facilitating bubble detachment from the electrode surface, thereby preventing "bubble shielding effect". This resulted in superior oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance, as well as overall water splitting capabilities. In a 1.0 M KOH solution, the electrode required only 166 and 195 mV overpotential to achieve a current density of 10 mA cm-2 for OER and HER, respectively. When functioning as a bifunctional catalytic electrode, only 1.60 V of voltage was necessary to drive the electrolyzer to reach a current density of 10 mA cm-2. Moreover, laboratory simulations of wind and solar energy-driven water splitting validated the feasibility of establishing a sustainable energy-to-hydrogen production chain. This work provides new insights into the preparation of low-overpotential, high-catalytic-activity superhydrophilic and underwater superaerophobic catalytic electrodes by rationally adjusting elemental ratios and exploring changes in electrode surface wettability.

Amorphous/polycrystalline NiMn selenide for high-performance supercapacitors.

Transition-metal selenides have been extensively studied as promising electrode materials for supercapacitors. Engineering amorphous/crystalline heterostructures is an effective strategy to improve rich active sites for accelerating redox reaction kinetics but still lacks exploration. In this study, an amorphous/crystalline heterostructure was designed and constructed by selenizing the self-sacrificial template NiMnS to generate amorphous Mn/polycrystalline Ni0.85Se-NiSe2 heterophase via the phase transformation from metal sulfide into metal selenide. The synergy of the complementary multi-components and amorphous/polycrystalline heterophase could enrich electron/ion-transport channels and expose abundant active sites, which accelerated electron/ion transfer and Faradaic reaction kinetics during charging/discharging. As expected, the optimal NiMnSe exhibited a high specific charge (1389.1 C g-1 at 1Ag-1), a good rate capability, and an excellent lifespan (88.9% retention). Moreover, the fabricated NiMnSe//activated carbon device achieved a long cycle life and energy density of 48.0Whkg-1 at 800Wkg-1, shedding light on the potential for use in practical applications, such as electrochemical energy-storage devices.

2D Se-Rich ZnSe/CoSe2@C Heterostructured Composite as Ultrastable Anodes for Alkaline-Ion Batteries.

2D transitional metal selenide heterostructures are promising electrode materials for potassium-ion batteries (PIBs) owing to the large surface area, high mechanical strength, and short diffusion pathways. However, the cycling performance remains a significant challenge, particularly concerning the electrochemical conversion reaction. Herein, 2D Se-rich ZnSe/CoSe2@C heterostructured composite is fabricated via a convenient hydrothermal approach followed by selenization process, and then applied as high-performance anodes for PIBs. For example, the capacity delivered by the heterostructured composite is mainly contributed to the synergistic effect of conversion and alloy/de-alloy processes aroused by K+, where K+ may highly insert or de-insert into Se-rich ZnSe/CoSe2@C. The obtained electrode delivers an outstanding reversible charge capacity of 214mA h g-1 at 1 A g-1 after 4000 cycles for PIBs, and achieves 262 mAh g-1 when coupled with a PTCDA cathode in the full cell. The electrochemical conversion mechanism of the optimized electrode during cycling is investigated through in situ XRD, Raman, and ex situ HRTEM. In addition, the heterostructured composite as anodes also displays excellent electrochemical performances for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). This work opens up a new window for investigating novel electrode materials with excellent capacity and long durability.

Regulating the microstructure and catalytic activity of metal selenides via calcination strategy for lithium-sulfur battery

Metal selenides obtain a series of advantages such as high electronic conductivity, excellent catalytic activity and facile fabrication approach, which are considered as promising catalysts in lithium sulfur (Li-S) battery. Traditional research based on metal selenides focuses on designing novel/complex microstructures or composites, however, the catalytic ability can be greatly affected by internal properties such as defect or vacancy. In this work, hollow nickel-cobalt layered double hydroxide (NiCo-LDH) is first fabricated and applied as a precursor to fabricate NiCoSe, and Se vacancy accompanied with crystal phase, microstructure and catalytic activity can be regulated by simply adjusting selenization atmosphere and temperature. Involving the application of NiCoSe in Li-S battery, the optimum fabrication parameter is perform the selenization at 600 °C under argon/5 % hydrogen, and the battery can exhibit a high discharge specific capacity of 1042.8 mAh g−1, excellent cycling performance of 500 cycles with a decay rate of 0.083 % at 1 C. This work highlights the importance of calcination process and also provides reference for further modifying the microstructure and performance of metal selenides in Li-S battery.

Unraveling the phase transition and electrochemical application of MoSe2 material for energy conversion and storage devices

Layered transition metal selenides have garnered widespread attention as the potential non-noble metal-based materials to cater to diverse energy conversion and storage aspects. Therefore, we have implemented an integrated experimental and theoretical methodology to explore the application of molybdenum diselenide (MoSe2) for HER, OER, and supercapacitor avenues via employing nanostructural and surface engineering performance enhancement strategy. Herein, we have demonstrated the successful execution of a laboratory-scale electrolyzer for water splitting with a low cell voltage of 1.54 V at 10 mA cm−2 and 1.74 V at 50 mA cm−2 current rate for 50 h. This was accomplished using synthesized exfoliated conductive carbon enwrapped MoSe2-E/C material. Further, the DFT calculations revealed the origin of better electrochemical performance on MoSe2-E (103) plane. Moreover, MoSe2-E/C showcased a high capacitance of 734 F g−1 (@ 1 A g−1) and 472 F g−1 (@ 20 A g−1) in a three-electrode setup and symmetric cell configuration respectively along with capacity retention of 95.02 % at a current density of 10 A g−1 after 2000 cycles. Hence, the prepared material exhibited its pertinence for rendering distinctive energy-related challenges owing to its unique structural arrangement.

CoSe2-Modified multidimensional porous carbon frameworks as high-Performance anode for fast-Charging sodium-Ion batteries

Transition metal selenides (TMSs) possess relatively high theoretical capacity and unique structures emerge as promising anode materials for sodium-ion batteries (SIBs). However, TMSs anode materials suffer from challenges such as substantial volume expansion, undesired side reactions, and poor active reaction dynamics. Herein, we propose a novel synthesis method that integrates metal salt-assisted polymer-blowing technique with in situ selenization strategy to fabricate multidimensional porous 3D carbon nanosheet frameworks modified by cobalt diselenide nanoparticles (CoSe2-CNF). Such unique architecture bestows intimate structural interconnectivity with high mechanical strength and abundant ion diffusion channels on CoSe2-CNF, exhibiting remarkable reversible capacity and fast-charging capability within diverse electrolyte systems. For instance, the CoSe2-CNF anode in ether electrolyte exhibits prominent rate performance of 349 mAh/g at 15 A/g. Sodium storage mechanism and fast electrochemical kinetics in the discharge/charge processes are investigated by in situ XRD and in situ EIS techniques. Additionally, DFT calculations are utilized to analyze the electrochemical differences observed in various electrolyte systems. When coupled with Na3V2(PO4) (NVP) cathodes, the full batteries also afford enhanced reversible capacity of 105 mAh/g over 100 cycles. The proposed structural engineering for CoSe2-CNF is beneficial for designing fast-charging energy storage devices.

Mangenese Copper Selenide Nanosheet Arrays Derived from Metal-Organic Frameworks for Efficient Solid-State Asymmetric Supercapacitors

Metal chalcogenide nanostructures, particularly metal selenides, have unique properties, such as high electrical conductivity, large specific surface area, exclusive porous networks, and exceptional electrochemical properties compared to traditional nanostructures.1 2 A novel strategy is proposed to design and fabricate hierarchical Manganese copper selenide nanosheet (MnCuSe NS) arrays from metal-organic frameworks (MOFs). The hierarchical MnCuSe NS arrays can deliver enriched electroactive sites and shorten the ion/electron diffusion pathways. When evaluated as positive electrodes for supercapacitor (SC), the MnCuSe NS electrode displayed remarkable electrochemical properties with ultra-high specific capacity of ≈350.4 mA h g− 1 and an areal capacity of ≈0.94 mA h cm− 2 at a current density of 3 mA cm− 2, exceptional rate capability (≈79.5% of the capacity retention at a higher current density of 50 mA cm− 2), and outstanding cyclic stability (≈95.4 % of capacity retention after 10 000 cycles). Most importantly, the assembled MnCuSe NS//FeMnO/NG solid-state asymmetric SC exhibited a wide operating potential window of 1.6 V with an ultra-high volumetric capacity of ≈2.4 mA h cm− 3 at a current density of 3 mA cm− 2, an excellent energy density of ≈71.6 Wh Kg− 1 at a power density of ≈794 W Kg− 1, and ultra-long cycle life (≈93.4 % of capacity retention after 10 000 cycles). This proposed method provides a general protocol to design and fabricate metal selenide nanosheet arrays with superior electrochemical energy storage properties and exceptional cyclic stability, holding significant potential for future energy storage devices in commercial aspects. Keywords: Hierarchical, Metal-organic frameworks, Metal chalcogenide, Energy density, Asymmetric supercapacitorsReference:(1) Han, J. H.; Kwak, M.; Kim, Y.; Cheon, J. Recent Advances in the Solution-Based Preparation of Two-Dimensional Layered Transition Metal Chalcogenide Nanostructures. Chem. Rev. 2018, 118 (13), 6151–6188. https://doi.org/10.1021/acs.chemrev.8b00264.(2) Karuppasamy, K.; Vikraman, D.; Hussain, S.; Kumar Veerasubramani, G.; Santhoshkumar, P.; Lee, S.-H.; Bose, R.; Kathalingam, A.; Kim, H.-S. Unveiling a Binary Metal Selenide Composite of CuSe Polyhedrons/CoSe2 Nanorods Decorated Graphene Oxide as an Active Electrode Material for High-Performance Hybrid Supercapacitors. Chemical Engineering Journal 2022, 427, 131535. https://doi.org/10.1016/j.cej.2021.131535.

In Situ Construction of (NiCo)3Se4 Nanobeads Embedded in N-Doped Carbon 3D Interconnected Networks for Enhanced Sodium Storage.

Transition metal selenides, boasting remarkable specific capacity, have emerged as a promising electrode material. However, the substantial volume fluctuations during sodium ion insertion and extraction result in inadequate cyclic stability and rate performance, impeding their practical utility. Here, we synthesized N-doped carbon three-dimensional (3D) interconnected networks encapsulating (NiCo)3Se4 nanoparticles, denoted as ((NiCo)3Se4/N-C), exhibiting a bead-like structure and carbon confinement through electrospinning and subsequent thermal treatment. The N-doped carbon 3D interconnected networks possess high porosity and ample volume buffering capacity, enhance conductivity, shorten ion diffusion paths, and mitigate mechanical stress induced by volume changes during cycling. The uniformly distributed (NiCo)3Se4 nanoparticles, featuring a stable structure, demonstrate rapid electrochemical kinetics and numerous available active sites. The distinctive structure and composition of the optimized (NiCo)3Se4/N-C material showcase a high specific capacity (656.2 mAh g-1 at 0.1 A g-1) and an outstanding rate capability. A kinetic analysis confirms that (NiCo)3Se4/N-C stimulates the pseudocapacitive Na+ storage mechanism with capacitance contributing up to 89.2% of the total capacity. This unique structure design and doping approach provide new insights into the design of electrode materials for high-performance batteries.

Iron-nickel-cobalt selenide nanoparticles as an efficient and transparent counter electrode for dye-sensitized solar cells

In this study, we developed a quaternary metal selenide (Fe0.35Ni0.11Co0.19Se) counter electrode (CE) material, grown onto fluorine-doped tin oxide, for dye-sensitized solar cells (DSSCs) using the potential-reversal electrochemical deposition technique at ambient conditions. Under optimized conditions, the Fe0.35Ni0.11Co0.19Se CE exhibited excellent electrocatalytic activity in the I-/I3- redox reaction with the average transmittance of 78.85 %. The additional valence states of Fe in the Ni0.3Co0.3Se electrode material further enhanced the catalytic activity during the electrochemical redox process. The DSSC employing this electrocatalytically active CE realized a power conversion efficiency of 7.73 %, surpassing the efficiency of both Pt and Ni0.3Co0.3Se CEs-based DSSCs (7.23 % and 7.23 %, respectively). This electro-preparation method offers a simpler and more cost-effective fabrication process for CE design, demonstrating a good potential for replacing expensive platinum CEs in DSSCs.

Controllable preparation of polymetallic selenides and their application in high-performance supercapacitors

Transition metal selenides (TMSes) have garnered considerable interest as potential electrode materials for supercapacitors owing to their promising electrochemical properties, but the fabrication of intricate nanostructured electrodes utilizing these compounds still poses a formidable challenge. In this study, a ternary transition metal selenide nanomaterial Cu2MnSnSe4, which has rarely been reported, was successfully synthesized on nickel foam (NF) by a simple solvothermal method, and its electrochemical properties have not been concern by researchers. We systematically studied the electrochemical properties of the materials synthesized under different solvothermal reaction times, and discussed the relationship between reaction time and electrochemical properties. The unique porous surface architecture of the sea urchin-like nanosphere configuration in Cu2MnSnSe4 material grants it a significantly enhanced specific surface area and a proliferation of electrochemically active sites, surpassing those of other comparable materials. According to the synthesis reaction time from short to long, the materials were named Cu2MnSnSe4-1 (20h), Cu2MnSnSe4-2 (25h) and Cu2MnSnSe4-3 (30h), among which Cu2MnSnSe4-2 showed better electrochemical performance than the other two. Electrochemical results show that the prepared Cu2MnSnSe4-2 electrode possesses an outstanding specific capacitance of 930.6 mF cm−2 at 2 mA cm−2, good rate performance (92 %), and a capacitance retention rate is 67.57 % after 3000 cycles of charging and discharging. The asymmetric supercapacitor (ASC) exhibits a voltage window spanning 0–1.6 V, reaching an outstanding energy density of 0.076 mWh cm−2 at 1.47 mW cm−2. Remarkably, it maintains 129.63 % cycling stability even after enduring 5000 charge-discharge cycles. From the above results, it can be seen that Cu2MnSnSe4 material may be a promising electrode material with broad application prospects in the practical application of supercapacitors.

Self-assembled 3D CoSe-based sulfur host enables high-efficient and durable electrocatalytic conversion of polysulfides for flexible lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation energy storage systems. However, the commercial applications are severely limited by the sluggish kinetics and shuttling effect. Herein, we have designed an integrated free-standing functional CoSe-CNF-GO-MXene (CCGM) sulfur host with a “point-line-plane” 3D porous structure for Li-S batteries. The two-dimensional (2D) graphene, MXene and one-dimensional (1D) nanocellulose fibers combined with zero-dimensional (0D) transition metal selenide (CoSe) shows good electrical conductivity and enhanced catalytic performance, respectively. Additionally, the rationally designed porous structure (from 0D to 3D) demonstrates well-connected ion/electron transport channels, conferring the good kinetic performance. Electrochemical tests show that CoSe catalytic materials with moderate adsorption energies can catalyse both precipitation and dissolution processes of Li2S, enabling fast conversion kinetics. The density functional theory (DFT) calculations show that the synergistic effect of CoSe, Ti3C2Tx, and graphene can improve the chemisorption and catalytic performance. As a result, the 3D porous S@CCGM cathode exhibits a high initial discharge capacity of 1205.1 mAh g−1 at 0.2C and good long-term cycling performance with a low decay rate of 0.055 % per cycle at 1C. Furthermore, the gel electrolyte Li-S pouch cell successfully passes the 0–180° bending test, nailing test, and cutting test. Such design offers a new perspective for the commercialization of safe and flexible electrochemical energy-storage devices especially in Li-S batteries.

Exploring Selenide Synthesis Pathways for Optimizing Energy Conversion.

This study investigated the structural and electrochemical characteristics of binary and quaternary systems comprising nickel, cobalt, and iron selenides. The powders were obtained via a solvothermal route. X-ray diffraction (XRD) and Raman spectroscopy revealed significant phase diversity. It was observed that increasing the proportion of d-block metals in quaternary systems enhances structural entropy, potentially leading to more homogeneous and stable structures dominated by energetically preferred components such as nickel. The electrochemical analysis indicated that the binary system exhibited a reversible redox reaction, with nickel selenide-based samples demonstrating the highest electrochemically active surface area. Quaternary systems display varying degrees of electrochemical stability. An equal contribution of nickel, cobalt, and iron appears beneficial in achieving stable electrodes. This research contributes to understanding the relationship between transition metal selenides' structural, morphological, and electrochemical properties, providing insights into their potential applications in hydrogen generation.

Fabrication of a Stable and Highly Effective Anode Material for Li-Ion/Na-Ion Batteries Utilizing ZIF-12.

Transition metal selenides (TMSs) are receiving considerable interest as improved anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) due to their considerable theoretical capacity and excellent redox reversibility. Herein, ZIF-12 (zeolitic imidazolate framework) structure is used for the synthesis of Cu2Se/Co3Se4@NPC anode material by pyrolysis of ZIF-12/Se mixture. When Cu2Se/Co3Se4@NPC composite is utilized as an anode electrode material in LIB and SIB half cells, the material demonstrates excellent electrochemical performance and remarkable cycle stability with retaining high capacities. In LIB and SIB half cells, the Cu2Se/Co3Se4@NPC anode material shows the ultralong lifespan at 2000 mAg-1, retaining a capacity of 543 mAhg-1 after 750 cycles, and retaining a capacity of 251 mAhg-1 after 200 cycles at 100 mAg-1, respectively. The porous structure of the Cu2Se/Co3Se4@NPC anode material can not only effectively tolerate the volume expansion of the electrode during discharging and charging, but also facilitate the penetration of electrolyte and efficiently prevents the clustering of active particles. In situ X-ray difraction (XRD) analysis results reveal the high potential of Cu2Se/Co3Se4@NPC composite in building efficient LIBs and SIBs due to reversible conversion reactions of Cu2Se/Co3Se4@NPC for lithium-ion and sodium-ion storage.

Hierarchical porous 3D NiCoZn-se heterojunction nanosheets for high-performance flexible supercapacitor

Transition metal selenides have attracted much attention as an electrode material with an ideal composition. However, there is still a lack of in-depth research on the design of its microstructure. In this paper, porous folded nickel‑cobalt‑zinc-selenide electrode materials were obtained by using hydrothermal method with annealing. This structure provides a large number of active sites and shortens the ion diffusion pathway, thus facilitating the enhancement of electrochemical processes. The finite element analysis shows that the pleated structure has more excellent mechanical properties. Therefore, it was used as an electrode material, exhibiting an area specific capacitance of 2475 mF cm−2 at a current density of 2 mA cm−2. The capacity retention rate of the electrode is still as high as 81.0 % after 5000 cycle tests. To further validate its practical application, an asymmetric supercapacitor (ASC) consisting of NiCoZn-Se electrodes and activated carbon (AC) electrodes was fabricated. The device exhibited an area specific capacitance of 950 mF cm−2 at 4 mA cm−2 and still had 82 % of the initial capacity after 8000 cycles. In addition, the flexibility test shows that the device still maintains good electrochemical performance at different bending angles. These findings indicate that this electrode material has significant potential for application.

Dandelion-like VSe2-embellished CuSe-Co3Se4 hollow nanotube clusters as bifunctional catalysts for high-performance alkaline hydrogen evolution and solar cells

Among the various non-precious metal catalysts that drive hydrogen evolution reactions (HERs) and dye-sensitized solar cells (DSSCs), transition metal selenides (TMSs) stand out due to their unique electronic properties and tunable morphology. Herein, the multicomponent selenide CuSe-Co3Se4@VSe2 was successfully synthesized by doping with metal element vanadium and selenization on the copper-cobalt carbonate hydroxide (CuCo-CH) template. CuSe-Co3Se4@VSe2 exhibited the dandelion-like cluster structure composed of hollow nanotubes doped with VSe2 nanoparticles. Due to the unique structure and the synergistic effect of various elements, CuSe-Co3Se4@VSe2 showed excellent alkaline HER and DSSC performances. The DSSC based on CuSe-Co3Se4@VSe2 exhibited an impressive power conversion efficiency (PCE) of 9.64 %, which was much higher than that of Pt (8.39 %). Besides, it possessed a low HER overpotential of 76 mV@10 mA cm−2 and a small Tafel slope of 88.9 mV dec−1 in 1.0 M KOH.

The Preparation of N, P-Doped NiSe Nanorod Electrode Materials on Nickel Foam Using the Microwave Method for High-Performance Supercapacitors.

Transition metal selenides have the leading position in the field of energy storage and conversion due to their high theoretical capacity, good electrical conductivity, and cycling stability. Nickel is widely used for the construction of positive electrodes in devices due to its good conductivity, variable valence state, and ideal redox activity. NiSe materials have high internal resistance and are prone to volume change during charging and discharging, thus affecting the practical application of this electrode material, and the reported NiSe materials have not achieved a more desirable capacity value. Therefore, in this study, N, P-NiSe nanoelectrode materials were prepared using nickel foam as the nickel source and hexachlorocyclotriphonitrile as the nitrogen and phosphorus dopant using an efficient, energy-saving, and simple microwave method. It was also characterised by XRD and XPS to confirm the successful preparation of N, P-NiSe materials. In addition, the material yielded a high capacitance value (3184 F g-1) and good cycling stability (72% of the initial capacitance value was retained after 4000 cycles) in electrochemical tests. To demonstrate its excellent suitability for practical applications, an asymmetric supercapacitor was assembled using N, P-NiSe as the anode and activated carbon as the cathode. At an operating voltage of 1.6 V, the device achieved an energy density of 289.06 Wh kg-1 and a power density of 799.26 W kg-1 and retained 80% of its initial capacity after 20,000 cycles.

Constructing interfacial chemical interaction of dual-carbon protected cobalt diselenide anode for sodium storage

Transition metal selenides are attracting enormous attention due to their high theoretical capacity and appropriate working potential for sodium storage, while their intrinsic low electronic conductivity and large volume expansion during the cycling processes inevitably result in inadequate rate performance and inferior cycling stability. Herein, cobalt diselenide-based hollow sugarloaf-like self-supporting fiber membranes with strong interfacial chemical (Co-C) bonds have been reported for sodium-ion batteries (SIBs) via the dual-carbon protection strategy. Based on X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) combined with density functional theory (DFT), A built-in electric field is generated at the interface between CoSe2/C and CNFs, which provides a strong driving force for electron transfer and ion migration, making the optimal CoSe2/C−0.3@CNFs anode over 67.8 % of capacity retention from 0.1 to 5 A/g and maintained about 269.5 mAh/g of discharge capacity at 5 A/g. The strong interfacial Co-C bonds in CoSe2/C@CNFs enhance the interfacial affinity between CoSe2/C and CNFs, making it easier for CoSe2/C to trap sodium ions and effectively resist the volume expansion during cycling, thus showing excellent cyclic stability with a reversible capacity of 247.6 mA h g−1 at 1.0 A/g after 2600 cycles. The sodium storage mechanism of CoSe2/C−0.3@CNFs electrode in SIBs is systematically analyzed via in-situ XRD and in-situ Raman spectra. This study provides an effective approach to constructing heterostructured composites with strong chemical bonds and built-in electric field characteristics for high-rate capability and long-cycle stability SIBs. Moreover, the sodium ion diffusion kinetics in the CoSe2/C−0.3@CNFs anode is also revealed.

High-entropy selenides derived from Prussian blue analogues as electrode materials for sodium-ion batteries

Transition metal selenides (TMS) have received much attention as anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacity and excellent redox reversibility. However, their further development is constrained by the dissolution of transition metal ions and substantial volume changes experienced during cycling. Herein, the high-entropy Prussian blue analogues were selenized by the vapor infiltration method, resulting in the formation of a core–shell structured high-entropy selenides (HESe-6). The core–shell structure with voids and abundant selenium vacancies on the surface effectively mitigates bulk expansion and enhances electronic conductivity. Furthermore, the high-entropy property endows an ultra-stable crystal structure and inhibits the dissolution of metal ions. The ex-situ EIS and in-situ XRD results show that HESe-6 is able to be reversibly transformed into highly conductive ultrafine metal particles upon Na+ embedding, providing more Na+ reactive active sites. In addition, despite the incorporation of up to seven different elements, it exhibits minimal phase transitions during discharge/charge cycles, effectively mitigating stress accumulation. HESe-6 could retain an ultralong-term stability of 765.83 mAh g−1 after 1000 loops even at 1 A g−1. Furthermore, when coupled with the Na3V2(PO4)2O2F cathode, it maintains a satisfactory charge energy density of 303 Wh kg−1 after 300 cycles, which shows promising application prospect in the future.

Engineering FeSe2 encapsulated within carboxymethylcellulose-derived porous carbon for enhanced surface reaction kinetics in Li-ion half/full battery anodes

Encapsulation of transitional metal selenides within the porous nanocarbon network has been regarded as a highly advantageous strategy for improving anode performance in terms of capacity, cycle-to-cycle stability, and operational durability for Li+ storage. Herein, a mildly sol-gel process and in-situ self-transformation strategy were employed to fabricate FeSe2 encapsulated within eco-friendly carboxymethylcellulose (CMC)-derived porous carbon, achieving a feasible capacity and relatively durable structure. The FeSe2@PC anode with square-built Li+/e− diffusion pathway exhibits a comparatively high reversible capacity of up to 758 mAh g−1 at 0.1 A g−1 and relatively good cycling stability, with a capacity retention of 83% after 500 cycles at 1 A g−1 in half cells. Furthermore, FeSe2@PC//LiMn2O4 full cells also demonstrate relatively outstanding electrochemical performance when paired with a LiMn2O4 cathode. The nanoconfinement electrode configuration, featuring interconnected external/internal carbon shell/FeSe2 nanoparticles, not only provides good electrical conductivity and buffering capacity for volume changes but also facilitates electrolyte infiltration and surface/near-surface interactions between electroactive FeSe2 and Li+. Kinetic analysis through cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy indicates exceptional Li+/e− transport kinetics. Employing green and eco-friendly materials in energy storage is crucial for advancing sustainable energy technologies, and the engineered FeSe2@PC nanocomposite demonstrated in this study offers promising potential towards this objective.

Transition Metal Selenide-Based Anodes for Advanced Sodium-Ion Batteries: Electronic Structure Manipulation and Heterojunction Construction Aspect.

In recent years, sodium-ion batteries (SIBs) have gained a foothold in specific applications related to lithium-ion batteries, thanks to continuous breakthroughs and innovations in materials by researchers. Commercial graphite anodes suffer from small interlayer spacing (0.334 nm), limited specific capacity (200 mAh g-1), and low discharge voltage (<0.1 V), making them inefficient for high-performance operation in SIBs. Hence, the current research focus is on seeking negative electrode materials that are compatible with the operation of SIBs. Many studies have been reported on the modification of transition metal selenides as anodes in SIBs, mainly targeting the issue of poor cycling life attributed to the volume expansion of the material during sodium-ion extraction and insertion processes. However, the intrinsic electronic structure of transition metal selenides also influences electron transport and sodium-ion diffusion. Therefore, modulating their electronic structure can fundamentally improve the electron affinity of transition metal selenides, thereby enhancing their rate performance in SIBs. This work provides a comprehensive review of recent strategies focusing on the modulation of electronic structures and the construction of heterogeneous structures for transition metal selenides. These strategies effectively enhance their performance metrics as electrodes in SIBs, including fast charging, stability, and first-cycle coulombic efficiency, thereby facilitating the development of high-performance SIBs.