CoSe2 Nanoparticles Encapsulated by N-Doped Carbon Framework Intertwined with Carbon Nanotubes: High-Performance Dual-Role Anode Materials for Both Li- and Na-Ion Batteries

Heterogeneous bimetallic selenides encapsulated within graphene aerogel as advanced anodes for sodium ion batteries

Metal selenides are promising anode candidates for sodium ion batteries (SIBs) because of their high theoretical capacity, low cost, and environmental friendship. However, the low rate capability at high current density due to its inherent low electrical conductivity and poor cycle stability caused by inevitable volume variations during cycling frustrate its practical applications. Herein, we have developed a simple metallic-organic frameworks (MOFs)-derived selenide strategy to synthesize a series of heterogeneous bimetallic selenides encapsulated within graphene aerogels (GA) as anodes for SIBs. The bimetallic selenides/GA composites have unique structural characteristics that can shorten the migration path for Na+/electrons and accommodate the volume variations via additional void space during cycling. The built-in electric fields induced at the heterointerfaces can greatly reduce the activation energy for rapid charge transfer kinetics and promote the diffusion of Na+/electrons. GA is also beneficial for accommodating the volume variations during cycling and improving conductivity. As an advanced anode for SIBs, the MoSe2-Cu1.82Se@GA with a special porous octahedron can deliver the highest capacity of 444.8 mAh/g at a high rate of 1 A/g even after 1000 cycles among the bimetallic selenides/GA composites.

ZCNC Beaded Heterostructure toward High-Performance Aluminum Batteries

We designed and prepared the ZnSe/CoSe2@NC/CNTs (ZCNC) cathode material for aluminum batteries (ABs). The ZCN (ZnSe/CoSe2@NC) is connected by the interwoven carbon nanotube (CNT) conductive network to form a beaded structure. CNTs and the carbon formed by carbonization of organic ligands is beneficial to improving the electrical conductivity of the material and reducing structural damage during cycling. The internal electric field generated at the interface of heterostructures can promote the transfer of electrons/ions. This special structure promotes ZCNC excellent electrochemical properties. At 100 mA/g, the specific capacity of the first discharge reaches 338 mAh/g, while the specific capacity after 500 cycles still reaches 217 mAh/g. Compared with ZCN and CN(CoSe2@NC), it demonstrates a great advantage.

Nanostructured Transition Metal Oxides on Carbon Fibers for Supercapacitor and Li-Ion Battery Electrodes: An Overview

Nowadays, owing to the new technological and industrial requirements for equipment, such as flexibility or multifunctionally, the development of all-solid-state supercapacitors and Li-ion batteries has become a goal for researchers. For these purposes, the composite material approach has been widely proposed due to the promising features of woven carbon fiber as a substrate material for this type of material. Carbon fiber displays excellent mechanical properties, flexibility, and high electrical conductivity, allowing it to act as a substrate and a collector at the same time. However, carbon fiber's energy-storage capability is limited. Several coatings have been proposed for this, with nanostructured transition metal oxides being one of the most popular due to their high theoretical capacity and surface area. In this overview, the main techniques used to achieve these coatings-such as solvothermal synthesis, MOF-derived obtention, and electrochemical deposition-are summarized, as well as the main strategies for alleviating the low electrical conductivity of transition metal oxides, which is the main drawback of these materials.

Infectious and Inflammatory Microenvironment Self-Adaptive Artificial Peroxisomes with Synergetic Co-Ru Pair Centers for Programmed Diabetic Ulcer Therapy

Complex microenvironments with bacterial infection, persistent inflammation, and impaired angiogenesis are the major challenges in chronic refractory diabetic ulcers. To address this challenge, a comprehensive strategy with highly effective and integrated antimicrobial, anti-inflammatory, and accelerated angiogenesis will offer a new pathway to the rapid healing of infected diabetic ulcers. Here, inspired by the tunable reactive oxygen species (ROS) regulation properties of natural peroxisomes, this work reports the design of infectious and inflammatory microenvironments self-adaptive artificial peroxisomes with synergetic Co-Ru pair centers (APCR) for programmed diabetic ulcer therapy. Benefiting from the synergistic Co and Ru atoms, the APCR can simultaneously achieve ROS production and metabolic inhibition for bacterial sterilization in the infectious microenvironment. After disinfection, the APCR can also eliminate ROS to alleviate oxidative stress in the inflammatory microenvironment and promote wound regeneration. The data demonstrate that the APCR combines highly effective antibacterial, anti-inflammatory, and provascular regeneration capabilities, making it an efficient and safe nanomedicine for treating infectious and inflammatory diabetic foot ulcers via a programmed microenvironment self-adaptive treatment pathway. This work expects that synthesizing artificial peroxisomes with microenvironments self-adaptive and bifunctional enzyme-like ROS regulation properties will provide a promising path to construct ROS catalytic materials for treating complex diabetic ulcers, trauma, or other infection-caused diseases.

A Universal In-Situ Interfacial Growth Strategy for Various MXene-Based van der Waals Heterostructures with Uniform Heterointerfaces: The Efficient Conversion from 3D Composite to 2D Heterostructures

Two-dimensional (2D) van der Waals heterostructures endow individual 2D material with the novel functional structures, intriguing compositions, and fantastic interfaces, which efficiently provide a feasible route to overcome the intrinsic limitations of single 2D components and embrace the distinct features of different materials. However, the construction of 2D heterostructures with uniform heterointerfaces still poses significant challenges. Herein, a universal in-situ interfacial growth strategy is designed to controllably prepare a series of MXene-based tin selenides/sulfides with 2D van der Waals homogeneous heterostructures. Molten salt etching by-products that are usually recognized as undesirable impurities, are reasonably utilized by us to efficiently transform into different 2D nanostructures via in-situ interfacial growth. The obtained MXene-based 2D heterostructures present sandwiched structures and lamellar interlacing networks with uniform heterointerfaces, which demonstrate the efficient conversion from 3D composite to 2D heterostructures. Such 2D heterostructures significantly enhance charge transfer efficiency, chemical reversibility, and overall structural stability in the electrochemical process. Taking 2D-SnSe2/MXene anode as a representative, it delivers outstanding lithium storage performance with large reversible capacities and ultrahigh capacity retention of over 97% after numerous cycles at 0.2, 1.0, and 10.0 A g-1 current density, which suggests its tremendous application potential in lithium-ion batteries.

One-step growth of ultrathin CoSe2 nanobelts on N-doped MXene nanosheets for dendrite-inhibited and kinetic-accelerated lithium-sulfur chemistry

The practical application of lithium-sulfur (Li-S) batteries is inhibited by the shuttle effect of lithium polysulfides (LiPSs) and slow polysulfide redox kinetics on the S cathode as well as the uncontrollable growth of dendrites on the Li metal anode. Therefore, both cathode and anode sides must be considered when modifying Li-S batteries. Herein, two-dimensional (2D) ultrathin CoSe2 nanobelts are in situ grown on 2D N-doped MXene nanosheets (CoSe2@N-MXene) via one-step solvothermal process for the first time. Owing to its unique 2D/2D structure, CoSe2@N-MXene can be processed to crumpled nanosheets by freeze-drying and flexible and freestanding films by vacuum filtration. These crumpled CoSe2@N-MXene nanosheets with abundant active sites and inner spaces can act as S hosts to accelerate polysulfide redox kinetics and suppress the shuttle effect of LiPSs owing to their strong adsorption ability and catalytic conversion effect with LiPSs. Meanwhile, the CoSe2@N-MXene film (CoSe2@NMF) can act as a current collector to promote uniform Li deposition because it contains lithiophilic CoSe2 and N sites. Under the systematic effect of CoSe2@N-MXene on S cathode and Li metal anode, the electrochemical and safety performance of Li-S batteries are improved. CoSe2@NMF also shows excellent storage performances in flexible energy storage devices.

Strategy for the Preparation of ZnS/ZnO Composites Derived from Metal-Organic Frameworks toward Lithium Storage

The synergistic effect between multicomponent electrode materials often makes them have better lithium storage performance than single-component electrode materials. Therefore, to enhance surface reaction kinetics and encourage electron transfer, using multicomponent anode materials is a useful tactic for achieving high lithium-ion battery performance. In this article, ZnS/ZnO composites were synthesized by solvothermal sulfidation and calcination, with the utilization of metal-organic frameworks acting as sacrificial templates. From the point of material design, both ZnS and ZnO have high theoretical specific capacities, and the synergistic effect of ZnS and ZnO can promote charge transport. From the perspective of electrode engineering, the loose porous carbon skeleton that results from the calcination of metal-organic frameworks can enhance composite material conductivity as well as full electrolyte penetration and the area of contact between the electrolyte and active material, all of which are beneficial to enhancing lithium storage performance. As expected, ZnS/ZnO anode materials displayed remarkably high specific capacities and outstanding performance at different rates. Combining material design and electrode engineering, this paper provides another idea for preparing anode materials with excellent lithium storage properties.

Recent Progress of Transition Metal Selenides for Electrochemical Oxygen Reduction to Hydrogen Peroxide: From Catalyst Design to Electrolyzers Application

Hydrogen peroxide (H2O2) is a highly value-added and environmental-friendly chemical with various applications. The production of H2O2 by electrocatalytic 2e- oxygen reduction reaction (ORR) has emerged as a promising alternative to the energy-intensive anthraquinone process. High selectivity Catalysts combining with superior activity are critical for the efficient electrosynthesis of H2O2. Earth-abundant transition metal selenides (TMSs) being discovered as a classic of stable, low-cost, highly active and selective catalysts for electrochemical 2e- ORR. These features come from the relatively large atomic radius of selenium element, the metal-like properties and the abundant reserves. Moreover, compared with the advanced noble metal or single-atom catalysts, the kinetic current density of TMSs for H2O2 generation is higher in acidic solution, which enable them to become suitable catalyst candidates. Herein, the recent progress of TMSs for ORR to H2O2 is systematically reviewed. The effects of TMSs electrocatalysts on the activity, selectivity and stability of ORR to H2O2 are summarized. It is intended to provide an insight from catalyst design and corresponding reaction mechanisms to the device setup, and to discuss the relationship between structure and activity.

Metal-Organic Framework-Based Materials for Advanced Sodium Storage: Development and Anticipation

As a pioneering battery technology, even though sodium-ion batteries (SIBs) are safe, non-flammable, and capable of exhibiting better temperature endurance performance than lithium-ion batteries (LIBs), because of lower energy density and larger ionic size, they are not amicable for large-scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal-organic frameworks (MOFs) would offer enormous opportunities for next-generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for effective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF-based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipated.

Metal-organic frameworks-derived MCo2O4 (M = Zn, Ni, Cu) two-dimensional nanosheets as anodes materials to boost lithium storage

Transition metal oxides (TMOs) have received significant consideration. Because of their enormous theoretical capacity, cheap, and less toxicity. Notably, cobalt-based materials hold promises as negative electrode materials for batteries, but they suffer from less electrical conductivity and significant volume changes during operation. In order to address these challenges, sacrificial templating techniques at the nanoscale offer a potential solution for improving the electrochemical stability and rate performance of these materials. More specifically, these tactics have proven popular for designing Li-ion storages. To ascertain the impact of multiple metal ions on the electrochemical capacity, metal organic frameworks (MOFs) derived MCo2O4-MOF (M = Zn, Ni, Cu) were developed. Among these, ZnCo2O4 showed the best electrochemical performance (927.2 mAh g-1 at 0.1 A g-1 after 250 cycles). Furthermore, calculations based on density functional theory (DFT) revealed that ZnCo2O4 had the lowest Li+ adsorption energy, with a minimum value of -1.61 eV. Moreover, this research aims to design controllable nanostructures in order to enhance the design of transition bimetallic oxide composites for energy storage applications.

Multilevel spatial confinement of transition metal selenides porous microcubes for efficient and stable potassium storage

Recently, potassium-ion batteries (PIBs) have been considered as one of the most promising energy storage systems; however, the slow kinetics and large volume variation induced by the large radius of potassium ions (K⁺) during chemical reactions lead to inferior structural stability and weak electrochemical activity for most potassium storage anodes. Herein, a multilevel space confinement strategy is proposed for developing zinc-cobalt bimetallic selenide (ZnSe/Co_0.85Se@NC@C@rGO) as high-efficient anodes for PIBs by in-situ carbonizing and subsequently selenizing the resorcinol-formaldehyde (RF)-coated zeolitic imidazolate framework-8/zeolitic imidazolate framework-67 (ZIF-8/ZIF-67) encapsulated into 2D graphene. The highly porous carbon microcubes derived from ZIF-8/ZIF-67 and carbon shell arising from RF provide rich channels for ion/electron transfer, present a rigid skeleton to ensure the structural stability, offer space for accommodating the volume change, and minimize the agglomeration of active material during the insertion/extraction of large-radius K⁺. In addition, the three-dimensional (3D) carbon network composed of graphene and RF-derived carbon-coated microcubes accelerates the electron/ion transfer rate and improves the electrochemical reaction kinetics of the material. As a result, the as-synthesized ZnSe/Co_0.85Se@NC@C@rGO as the anode of PIBs possesses the excellent rate capability of 203.9 mA h g^-1 at 5 A g^-1 and brilliant long-term cycling performance of 234 mA h g^-1 after 2,000 cycles at 2 A g^-1. Ex-situ X-ray diffraction (Ex-situ XRD) diffraction reveals that the intercalation/de-intercalation of K⁺ proceeds through the conversion-alloying reaction. The proposed strategy based on the spatial confinement engineering is highly effective to construct high-performance anodes for PIBs.

Trapping Lithium Selenides with Evolving Heterogeneous Interfaces for High-Power Lithium-Ion Capacitors

Transition metal selenides anodes with fast reaction kinetics and high theoretical specific capacity are expected to solve mismatched kinetics between cathode and anode in Li-ion capacitors. However, transition metal selenides face great challenges in the dissolution and shuttle problem of lithium selenides, which is the same as Li-Se batteries. Herein, inspired by the density functional theory calculations, heterogeneous can enhance the adsorption of Li₂ Se relative to single component selenide electrodes, thus inhibiting the dissolution and shuttle effect of Li₂ Se. A heterostructure material (denoted as CoSe₂ /SnSe) with the ability to evolve continuously (CoSe₂ /SnSe→Co/Sn→Co/Li₁₃ Sn₅ ) is successfully designed by employing CoSnO₃ -MOF as a precursor. Impressively, CoSe₂ /SnSe heterostructure material delivers the ultrahigh reversible specific capacity of 510 mAh g^-1 after 1000 cycles at the high current density of 4 A g^-1 . In situ XRD reveals the continuous evolution of the interface based on the transformation and alloying reactions during the charging and discharging process. Visualizations of in situ disassembly experiments demonstrate that the continuously evolving interface inhibits the shuttle of Li₂ Se. This research proposes an innovative approach to inhibit the dissolution and shuttling of discharge intermediates (Li₂ Se) of metal selenides, which is expected to be applied to metal sulfides or Li-Se and Li-S energy storage systems.

Terminal Group-Oriented Self-Assembly to Controllably Synthesize a Layer-by-Layer SnSe2 and MXene Heterostructure for Ultrastable Lithium Storage

Heterostructured materials integrate the advantages of adjustable electronic structure, fast electron/ions transfer kinetics, and robust architectures, which have attracted considerable interest in the fields of rechargeable batteries, photo/electrocatalysis, and supercapacitors. However, the construction of heterostructures still faces some severe problems, such as inferior random packing of components and serious agglomeration. Herein, a terminal group-oriented self-assembly strategy to controllably synthesize a homogeneous layer-by-layer SnSe₂ and MXene heterostructure (LBL-SnSe₂ @MXene) is designed. Benefitting from the abundant polar terminal groups on the MXene surface, Sn²⁺ is induced into the interlayer of MXene with large interlayer spacing, which is selenized in situ to obtain LBL-SnSe₂ @MXene. In the heterostructure, SnSe₂ layers and MXene layers are uniformly intercalated in each other, superior to other heterostructures formed by random stacking. As an anode for lithium-ion batteries, the LBL-SnSe₂ @MXene is revealed to possess strong lithium adsorption ability, the small activation energy for lithium diffusion, and excellent structure stability, thus achieving outstanding electrochemical performance, especially with high specific capacities (1311 and 839 mAh g^-1 for initial discharge and charge respectively) and ultralong cycling stability (410 mAh g^-1 at 5C even after 16 000 cycles). This work conveys an inspiration for the controllable design and construction of homogeneous layered heterostructures.

Metal-organic framework derived bimetallic selenide embedded in nitrogen-doped carbon hierarchical nanosphere for highly reversible sodium-ion storage

Bimetallic selenides with various valence transitions and high theoretical capacities are extensively studied as anodes for sodium-ion-batteries (SIBs), but their huge volume changes and poor capacity retention limit their practicality. Herein, a facile and controllable strategy using a binary Ni-Co metal-organic framework (MOF) precursors followed by the selenization process, which produced a cobalt nickel selenide/N-doped carbon composite ((CoNi)Se₂/NC) that maintained the hierarchical nanospheres structure. Such a distinctive structure affords both Na⁺ and electron diffusion pathways in the electrochemical reactions as well as high electrical conductivity, thus leading to superior electrochemical performance when the designed composite is utilized as an anode in SIBs. The resulting nanospheres-like (CoNi)Se₂/NC hierarchical structure exhibits a high specific capacity of 526.8 mA h g^-1 at 0.2 A/g over 100 cycles, a stable cycle life with no obvious capacities loss at 1.0 and 3.0 A/g after 500 cycles, and exceptional rate capability of 322.9 mA h g^-1 at 10.0 A/g.

Controllable Synthesis of Carbon Yolk-Shell Microsphere and Application of Metal Compound-Carbon Yolk-Shell as Effective Anode Material for Alkali-Ion Batteries

Recently, nanostructured carbon materials, such as hollow-, yolk-, and core-shell-configuration, have attracted attention in various fields owing to their unique physical and chemical properties. Among them, yolk-shell structured carbon is considered as a noteworthy material for energy storage due to its fast electron transfer, structural robustness, and plentiful active reaction sites. However, the difficulty of the synthesis for controllable carbon yolk-shell has been raised as a limitation. In this study, novel synthesis strategy of nanostructured carbon yolk-shell microspheres that enable to control morphology and size of the yolk part is proposed for the first time. To apply in the appropriate field, cobalt compounds-carbon yolk-shell composites are applied as the anode of alkali-ion batteries and exhibit superior electrochemical performances to those of core-shell structures owing to their unique structural merits. Co₃ O₄ -C hollow yolk-shell as a lithium-ion battery anode exhibits a long cycling lifetime (619 mA h g^-1 for 400 cycles at 2 A g^-1 ) and excellent rate capability (286 mA h g^-1 at 10 A g^-1 ). The discharge capacities of CoSe₂ -C hollow yolk-shell as sodium- and potassium-ion battery anodes at the 200th cycle are 311 mA h g^-1 at 0.5 A g^-1 and 268 mA h g^-1 at 0.2 A g^-1 , respectively.

Rapid Amorphization in MOF/Metal Selenite Nanocomposites for Enhanced Capacity in Supercapacitors

MOF/inorganic nanocomposites combine the advantages of each component. Herein, two MOF/metal selenite nanocomposites, Co-NH₂-BDC/CoSeO₃·H₂O and Co-BDC/CoSeO₃·H₂O, are prepared on nickel foam through a facile two-step hydrothermal method, which inherit the 2D morphology and porosity properties of their MOF precursors. Furthermore, during the electrochemical activation process, the crystallized nanocomposites can easily transform into amorphous structures in a short time of 20 min in the presence of an electric field, similar to CoSeO₃·H₂O. Due to amorphization, the electrochemical performance of the two nanocomposites is much enhanced relative to that of their MOF precursors. Specifically, the areal capacitances of Co-NH₂-BDC/CoSeO₃·H₂O and Co-BDC/CoSeO₃·H₂O are 5.35 and 10.65 F·cm^-2 at 2 mA·cm^-2, respectively. The assembled asymmetric supercapacitor (ASC) using Co-NH₂-BDC/CoSeO₃·H₂O as positive electrodes delivers an energy density of 0.207 mWh·cm^-2 at a power density of 0.799 mW·cm^-2 with outstanding cycling stability (93% capacity retention after 5000 cycles). Using Co-BDC/CoSeO₃·H₂O as positive electrodes, the ASC can reach a high energy density of 0.483 mWh·cm^-2 at a power density of 0.741 mW·cm^-2 and 84% capacity retention after 5000 cycles. This work provides an efficient strategy for constructing MOF/metal selenite nanocomposites for energy storage and conversion.

Metal Selenides Anode Materials for Sodium Ion Batteries: Synthesis, Modification, and Application

The powerful and rapid development of lithium-ion batteries (LIBs) in secondary batteries field makes lithium resources in short supply, leading to rising battery costs. Under the circumstances, sodium-ion batteries (SIBs) with low cost, inexhaustible sodium reserves, and analogous work principle to LIBs, have evolved as one of the most anticipated candidates for large-scale energy storage devices. Thereinto, the applicable electrode is a core element for the smooth development of SIBs. Among various anode materials, metal selenides (MSe_x ) with relatively high theoretical capacity and unique structures have aroused extensive interest. Regrettably, MSe_x suffers from large volume expansion and unwished side reactions, which result in poor electrochemistry performance. Thus, strategies such as carbon modification, structural design, voltage control as well as electrolyte and binder optimization are adopted to alleviate these issues. In this review, the synthesis methods and main reaction mechanisms of MSe_x are systematically summarized. Meanwhile, the major challenges of MSe_x and the corresponding available strategies are proposed. Furthermore, the recent research progress on layered and nonlayered MSe_x for application in SIBs is presented and discussed in detail. Finally, the future development focuses of MSe_x in the field of rechargeable ion batteries are highlighted.

Interface engineering in NiSe2/Ni2Co/CoSe2 heterostructures encapsulated in hollow carbon shells for high-rate Li-Se batteries

The sluggish conversion reaction and the accompanying huge volume fluctuation greatly hinder the application of lithium-selenium (Li-Se) batteries. Therefore, reasonably constructing stable carbonaceous hosts with efficient electrochemically active sites is particularly essential for promoting the development of Se cathodes. Herein, a metal-organic solid derived carbon host with multiple heterogeneous NiSe₂/Ni₂Co/CoSe₂ interfaces was fabricated via in situ selenization. The formation of multiple heterointerfaces introduced subtle atomic array distortions, which provided additional electrochemically active sites compared with single heterointerfaces. Besides, the establishment of a built-in electric field was favorable for electron transfer and the absorption of Li⁺, thereby accelerating the reaction kinetics. Depending on the hollow structure and the heterogeneous catalysts, Li-Se batteries with NiSe₂/Ni₂Co/CoSe₂@Se cathodes delivered reversible capacities of 503 and 324 mA h g^-1 after 900 and 2200 cycles at 1 and 12 C, respectively. This work revealed the synergistic mechanism of multiple heterostructures composed of a Ni₂Co alloy and in situ derived bimetallic selenides for Se cathodes and provided new insights into the exploitation of energy storage materials.

Insights into Electrochemical Processes of Hollow Octahedral Co3Se4@rGO for High-Rate Sodium Ion Storage

Sodium ion batteries (SIBs), as an alternative and promising energy storage system, have attracted considerable attention due to the abundant reserves and low cost of sodium. However, it remains a great challenge to achieve high capacity and rate capability required for practical applications. Herein, hollow octahedral Co₃Se₄ particles encapsulated in reduced graphene oxide (Co₃Se₄@rGO) were designed and synthesized and exhibited excellent electrochemical performances as anodes of SIBs, especially rate capability. Sodiation/desodiation processes and involved mechanisms were investigated by using in situ TEM and in situ XRD. During sodiation, a crystalline Na₂Se layer with numerous amorphous fine Co nanoparticles dispersed on it was observed to appear on the surface of the original Co₃Se₄@rGO particles, and the movable Co-Na₂Se composites further migrated to the rGO network with high electron/ion dual conductivity, resulting in ultrafast sodium storage kinetics and remarkable rate performance of the Co₃Se₄@rGO anode evidenced by delivering a discharge capacity of 229.3 mAh g^-1 at a large current density of 50 A g^-1. Our findings reveal the fundamental mechanism behind the enhanced performance of the Co₃Se₄@rGO anode and offer valuable insights into the rational design of electrode materials for high-performance SIBs.

Zeolite Imidazolate Frameworks (ZIFs) Derived Nanomaterials and their Hybrids for Advanced Secondary Batteries and Electrocatalysis

Zeolite imidazolate frameworks (ZIFs), as a typical class of metal-organic frameworks (MOFs), have attracted a great deal of attention in the field of energy storage and conversation due to their chemical structure stability, facile synthesis and environmental friendliness. Among of ZIFs family, the zinc-based imidazolate framework (ZIF-8) and cobalt-based imidazolate framework (ZIF-67) have considered as promising ZIFs materials, which attributed to their tunable porosity, stable structure, and desirable electrical conductivity. To date, various ZIF-8 and ZIF67 derived materials, including carbon materials, metal oxides, sulfides, selenides, carbides and phosphides, have been successfully synthesized using ZIFs as templates and evaluated as promising electrode materials for secondary batteries and electrocatalysis. This review provides an effective guide for the comprehension of the performance optimization and application prospects of ZIFs derivatives, specifically focusing on the optimization of structure and their application in secondary batteries and electrocatalysis. In detail, we present recent advances in the improvement of electrochemical performance of ZIF-8, ZIF-67 and ZIF-8@ZIF-67 derived nanomaterials and their hybrids, including carbon materials, metal oxides, carbides, oxides, sulfides, selenides, and phosphides for high-performance secondary batteries and electrocatalysis.

Electrochemical performance of CoSe2 with mixed phases decorated with N-doped rGO in potassium-ion batteries

Potassium-ion batteries (PIBs) have received much attention as next-generation energy storage systems because of their abundance, low cost, and slightly lower standard redox potential than lithium-ion batteries (LIBs). Nevertheless, they still face great challenges in the design of the best electrode materials for applications. Herein, we have successfully synthesized nano-sized CoSe₂ encapsulated by N-doped reduced graphene oxide (denoted as CoSe₂@N-rGO) by a direct one-step hydrothermal method, including both orthorhombic and cubic CoSe₂ phases. The CoSe₂@N-rGO anodes exhibit a high reversible capacity of 599.3 mA h g⁻¹ at 0.05 A g⁻¹ in the initial cycle, and in particular, they also exhibit a cycling stability of 421 mA h g⁻¹ after 100 cycles at 0.2 A g⁻¹. Density functional theory (DFT) calculations show that CoSe₂ with N-doped carbon can greatly accelerate electron transfer and enhance the rate performance. In addition, the intrinsic causes of the higher electrochemical performance of orthorhombic CoSe₂ than that of cubic CoSe₂ are also discussed.

Potassium-ion batteries (PIBs) have received much attention as next-generation energy storage systems because of their abundance, low cost, and slightly lower standard redox potential than lithium-ion batteries (LIBs).

Dual Carbon Design Strategy for Anodes of Sodium-Ion Battery: Mesoporous CoS2/CoO on Open Framework Carbon-Spheres with rGO Encapsulating

Transition metal sulfides and oxides with high theoretical capacities have been regarded as promising anode candidates for a sodium-ion battery (SIB); however, they have critical issues including sluggish electrochemical kinetics and poor long-term stability. Herein, a dual carbon design strategy is proposed to integrate with highly active heterojunctions to overcome the above issues. In this new design, CoS₂/CoO hollow dodecahedron heterojunctions are sandwiched between open framework carbon-spheres (OFCs) and a reduced graphene oxide (rGO) nanomembrane (OFC@CoS₂/CoO@rGO). The CoS₂/CoO heterojunctions effectively promote electron transfer on their surface and provide more electrochemical active sites through their hierarchical hollow structures assembled by nanodots. Meanwhile, the dual-carbon framework forms a highly conductive network that enables a better rate capability. More importantly, the dual carbon can greatly buffer volume expansion and stable reaction interfaces of electrode material during the charge/discharge process. Benefitting from their synergistical effects, the OFC@CoS₂/CoO@rGO electrode achieves a high reversible capacity of 460 mAh g^-1 at 0.05 A g^-1 and still maintains 205.3 mAh g^-1 even when current density is increased by 200 times when used as an anode material for SIBs. Their cycling property is also remarkable with a maintained capacity of 161 mAh g^-1 after 3500 charging/discharging cycles at a high current density of 1 A g^-1. The dual-carbon strategy is demonstrated to be effective for enhanced reaction kinetics and long-term cycling property, providing siginificant guidance for preparing other high-performance electrode materials.

Innovative Materials for Energy Storage and Conversion

The metal chalcogenides (MCs) for sodium-ion batteries (SIBs) have gained increasing attention owing to their low cost and high theoretical capacity. However, the poor electrochemical stability and slow kinetic behaviors hinder its practical application as anodes for SIBs. Hence, various strategies have been used to solve the above problems, such as dimensions reduction, composition formation, doping functionalization, morphology control, coating encapsulation, electrolyte modification, etc. In this work, the recent progress of MCs as electrodes for SIBs has been comprehensively reviewed. Moreover, the summarization of metal chalcogenides contains the synthesis methods, modification strategies and corresponding basic reaction mechanisms of MCs with layered and non-layered structures. Finally, the challenges, potential solutions and future prospects of metal chalcogenides as SIBs anode materials are also proposed.

Doping-Induced Electronic/Ionic Engineering to Optimize the Redox Kinetics for Potassium Storage: A Case Study of Ni-Doped CoSe2

Heteroatom doping effectively tunes the electronic conductivity of transition metal selenides (TMSs) with rapid K⁺ accessibility in potassium ion batteries (PIBs). Although considerable efforts are dedicated to investigating the relationship between the doping strategy and the resulting electrochemistry, the doping mechanisms, especially in view of the ion and electronic diffusion kinetics upon cycling, are seldom elucidated systematically. Herein, the crystal structure stability, charge/ion state, and bandgap of the active materials are found to be precisely modulated by favorable heteroatom doping, resulting in intrinsically fast kinetics of the electrode materials. Based on the combined mechanisms of intercalation and conversion reactions, electron and K⁺ ion transfer in Ni-doped CoSe₂ embedded in carbon nanocomposites (Ni-CoSe₂ @NC) can be significantly enhanced via electronic engineering. Benefiting from the synthetic controlled Ni grains, the heterointerface formed by the intermediate products of electrochemical reactions in Ni-CoSe₂ @NC strengthens the conversion kinetics and interdiffusion process, developing a low-barrier mesophase with optimized potassium storage. Overall, an electronic tuning strategy can offer deeper atomic insights into the conversion reaction of TMSs in PIBs.

Porous Microspheres Comprising CoSe2 Nanorods Coated with N-Doped Graphitic C and Polydopamine-Derived C as Anodes for Long-Lived Na-Ion Batteries

Metal-organic framework-templated nitrogen-doped graphitic carbon (NGC) and polydopamine-derived carbon (PDA-derived C)-double coated one-dimensional CoSe₂ nanorods supported highly porous three-dimensional microspheres are introduced as anodes for excellent Na-ion batteries, particularly with long-lived cycle under carbonate-based electrolyte system. The microspheres uniformly composed of ZIF-67 polyhedrons and polystyrene nanobeads (ϕ = 40 nm) are synthesized using the facile spray pyrolysis technique, followed by the selenization process (P-CoSe₂@NGC NR). Further, the PDA-derived C-coated microspheres are obtained using a solution-based coating approach and the subsequent carbonization process (P-CoSe₂@PDA-C NR). The rational synthesis approach benefited from the synergistic effects of dual carbon coating, resulting in a highly conductive and porous nanostructure that could facilitate rapid diffusion of charge species along with efficient electrolyte infiltration and effectively channelize the volume stress. Consequently, the prepared nanostructure exhibits extraordinary electrochemical performance, particularly the ultra-long cycle life stability. For instance, the advanced anode has a discharge capacity of 291 (1000th cycle, average capacity decay of 0.017%) and 142 mAh g^-1 (5000th cycle, average capacity decay of 0.011%) at a current density of 0.5 and 2.0 A g^-1, respectively.

Achieving Uniform Li Plating/Stripping at Ultrahigh Currents and Capacities by Optimizing 3D Nucleation Sites and Li2 Se-Enriched SEI

Lithium (Li) has garnered considerable attention as an alternative anodes of next-generation high-performance batteries owing to its prominent theoretical specific capacity. However, the commercialization of Li metal anodes (LMAs) is significantly compromised by non-uniform Li deposition and inferior electrolyte-anode interfaces, particularly at high currents and capacities. Herein, a hierarchical three-dimentional structure with CoSe₂ -nanoparticle-anchored nitrogen-doped carbon nanoflake arrays is developed on a carbon fiber cloth (CoSe₂ -NC@CFC) to regulate the Li nucleation/plating process and stabilize the electrolyte-anode interface. Owing to the enhanced lithiophilicity endowed by CoSe₂ -NC, in situ-formed Li₂ Se and Co nanoparticles during initial Li nucleation, and large void space, CoSe₂ -NC@CFC can induce homogeneous Li nucleation/plating, optimize the solid electrolyte interface, and mitigate volume change. Consequently, the CoSe₂ -NC@CFC can accommodate Li with a high areal capacity of up to 40 mAh cm^-2 . Moreover, the Li/CoSe₂ -NC@CFC anodes possess outstanding cycling stability and lifespan in symmetric cells, particularly under ultrahigh currents and capacities (1600 h at 10 mA cm^-2 /10 mAh cm^-2 and 5 mA cm^-2 /20 mAh cm^-2 ). The Li/CoSe₂ -NC@CFC//LiFePO₄ full cell delivers impressive long-term performance and favorable flexibility. The developed CoSe₂ -NC@CFC provides insights into the development of advanced Li hosts for flexible and stable LMAs.

Heterojunction-Promoted Sodium Ion Storage of Bimetallic Selenides Encapsulated in a Carbon Sheath with Boosted Ion Diffusion and Stable Structure

Although metallic chalcogenides are deemed as attractive sodium anode materials recently, the electrochemical performance is severely confined by the liability of structural collapse and sluggish ion diffusion kinetics. Herein a composite of carbon-encapsulated bimetallic selenides MoSe₂-Sb₂Se₃ was prepared by a hydrothermal method on the basis of abundant reaction sites, high activity, an extra built-in electric field generated from heterointerfaces, and synergistic effects between the different components. Equally important, the carbon coating is effective to support the structural stability by restraining the vast volumetric variation to achieve the purpose of improving the cycling performance. The density functional theory calculation results indicate that the band gap is narrowed and that the work function is decreased on the interface of the MoSe₂-Sb₂Se₃ heterojunction, leading to an additional driving force stemming from the introduction of the built-in electric field and the formation of the Sb-Se (Se from MoSe₂) bond. Therefore, the resultant composite presents increased reaction kinetics and good electrochemical properties by acquiring a capacity of 376.0 mA h g^-1 over 580 cycles at 2.0 A g^-1 for the half-cell and 276 mA h g^-1 over 750 cycles at 2 A g^-1 for the full-cell. This work highlights bimetallic selenides with facilitated ion transferability with high performance.

Recent advances of metal telluride anodes for high-performance lithium/sodium-ion batteries

Metal tellurides (MTs) have emerged as highly promising candidate anode materials for state-of-the-art lithium-ion batteries (LIBs) and sodium ion batteries (SIBs). This is owing to the unique crystal structure, high intrinsic conductivity, and high trap density of such materials. The present work delivers a detailed discussion on the latest research and progress associated with the use of MTs for LIBs/SIBs with a focus on reaction mechanisms, challenges, electrochemical performance, and synthesis strategies. Further, the prospects and future development of MT anode materials are discussed in terms of strategies to overcome the existing limitations. This review provides both an in-depth understanding of MTs and provides the driving force for expanding research on MTs for energy storage and conversion applications.

Polysulfide Catalytic Materials for Fast-Kinetic Metal-Sulfur Batteries: Principles and Active Centers

Benefiting from the merits of low cost, ultrahigh-energy densities, and environmentally friendliness, metal-sulfur batteries (M-S batteries) have drawn massive attention recently. However, their practical utilization is impeded by the shuttle effect and slow redox process of polysulfide. To solve these problems, enormous creative approaches have been employed to engineer new electrocatalytic materials to relieve the shuttle effect and promote the catalytic kinetics of polysulfides. In this review, recent advances on designing principles and active centers for polysulfide catalytic materials are systematically summarized. At first, the currently reported chemistries and mechanisms for the catalytic conversion of polysulfides are presented in detail. Subsequently, the rational design of polysulfide catalytic materials from catalytic polymers and frameworks to active sites loaded carbons for polysulfide catalysis to accelerate the reaction kinetics is comprehensively discussed. Current breakthroughs are highlighted and directions to guide future primary challenges, perspectives, and innovations are identified. Computational methods serve an ever-increasing part in pushing forward the active center design. In summary, a cutting-edge understanding to engineer different polysulfide catalysts is provided, and both experimental and theoretical guidance for optimizing future M-S batteries and many related battery systems are offered.

Topological transformation construction of CoSe2/N-doped carbon heterojunction with three-dimensional porous structure for high-performance sodium-ion half/full batteries

Transition metal selenides have been widely used as anode materials for sodium-ion batteries (SIBs) because of their considerable theoretical capacity and good conductivity. Nevertheless, the volume expansion is a serious...

In situ integration of cobalt diselenide nanoparticles on CNTs realizing durable hydrogen evolution

Cobalt diselenide (CoSe₂) is considered to be a promising economical and efficient electrocatalyst for the hydrogen evolution reaction (HER). Here carbon nanotubes (CNTs) were employed as a conductive skeleton to optimize the electrocatalytic performance of CoSe₂ through a simple one-step hydrothermal method. Beyond the expected, the introduction of CNTs not only accelerates electron transportation and ion diffusion, but also improves the reaction kinetics for HER by forming a CoSe₂/CNT heterointerface. Consequently, the CoSe₂/CNTs composite exhibits an optimal overpotential of 153 mV with a weight ratio of 10 : 1, and sustains a long period of 48 hours with an negligible overpotential deterioration. In addition, a Faraday efficiency of 97.67% is achieved with a H₂/O₂ molar ratio of 2 : 1. Therefore, these results open up further opportunities for yielding efficient and durable hydrogen evolving electrocatalysts from low-cost transition metal compounds.

The CoSe₂/CNT composites are integrated as electrocatalysts for the hydrogen evolution reaction, providing a new way to construct durable electrocatalysts from transition metal compounds.

Rational Design of Yolk-Shell ZnCoSe@N-Doped Dual Carbon Architectures as Long-Life and High-Rate Anodes for Half/Full Na-Ion Batteries

Transition-metal selenides (TMSs) have emerged as prospective anode materials for sodium ion batteries (SIBs), owing to their considerable theoretical capacity and intrinsic high electronic conductivity. Whereas, TMSs still suffer from poor rate capability and inferior cycling stability induced by sluggish kinetics and severe volume changes during de/sodiation processes. Herein, a hierarchical composite consisting of a zinc-cobalt bimetallic selenide yolk and nitrogen-doped double carbon shell (denoted as ZnCoSe@NDC) is engineered and fabricated successfully. The architecture of the as-fabricated material improves the Na-ion storage performance via increasing the electron transfer kinetics, accommodating volume expansion, and mitigating the generation of by-products. As expected, the ZnCoSe@NDC electrode delivers superior sodium storage performance with long cycling stability (344.5 mAh g^-1 at 5.0 A g^-1 over 2000 long-term cycles) and high-rate performance (319.2 mAh g^-1 at 10.0 A g^-1 ). Meanwhile, the NVP@C//ZnCoSe@NDC full SIB cells are constructed successfully, retaining 96.3% of its initial capacity at 0.5A g^-1 after 200 loops. The outstanding electrochemical performance and the construction of hybrid SIBs will have far-reaching influences on the development of the various rechargeable batteries.

Co0.85Se particles encapsulated in the inner wall of nitrogen-doped carbon matrix nanotubes with rational interfacial bonds for high-performance lithium-ion batteries

Cobalt selenides based on the conversion reaction have been widely applied in lithium-ion batteries (LIBs) due to their high conductivity and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se/Co dissolution and serious volume change during the cycling process is still a challenge. Herein, a facile and efficient self-generated sacrificial template method is used to prepare Co_0.85Se nanoparticles encapsulated in the inner wall of N-doped carbon matrix nanotubes (Co_0.85Se@NCMT). In this strategy, the formation of stable Co-N/C and Se-C as well as enhancing the mechanical strength between active materials and N-doped carbon matrix nanotubes can critically affect the performance through suppressing the dissolution of Se/Co, decreasing energy band, promoting the shuttling of the ions/e^- moving and mitigating the volume expansion during the charge-discharge process, which play a key role in improving the structure stability and electrochemical performance. Besides, Co_0.85Se nanoparticles encapsulated in the robust carbon matrix inner wall can ensure good electron transfer and prevent the aggregation of nanoparticles, leading to superior electrochemical reversibility. Finally, carbon matrix nanotubes can provide sufficient space to effectively accommodate the volume changes of encapsulated Co_0.85Se nanoparticles, thereby improving the cyclic stability. Based on the above advantages, as expected, the electrochemical investigations exhibited that the Co_0.85Se@NCMT anode performs a stable reversible capacity of 462.9 mA h g^-1 at a large current density of 5 A g^-1 and a remarkable capacity retention of 99.5% after 800 cycles, suggesting its promising potential for the anode of LIBs.

Controllable Heterojunctions with a Semicoherent Phase Boundary Boosting the Potassium Storage of CoSe2 /FeSe2

Heterostructure construction is an efficient method for reinforcing K⁺ storage of transition metal selenides. The spontaneously developed internal electric fields give a strong boost to charge transport and significantly reduce the activation energy. Nevertheless, perfection of the interfacial region based on the energy level gradient and lattice matching degree is still a great challenge. Herein, rich vacancies and ultrafine CoSe₂ -FeSe₂ heterojunctions with semicoherent phase boundary are simultaneously obtained, which possess unique electronic structures and abundant active sites. When employed as anodes for potassium-ion batteries (PIBs), CoSe₂ -FeSe₂ @C composites display a reversible potassium storage of 401.1 mAh g^-1 at 100 mA g^-1 and even 275 mAh g^-1 at 2 A g^-1 . Theoretical calculation also reveals that the potassium-ion diffusion can be dramatically promoted by the controllable CoSe₂ -FeSe₂ heterojunction.

Robust Pseudocapacitive Sodium Cation Intercalation Induced by Cobalt Vacancies at Atomically Thin Co1-x Se2 /Graphene Heterostructure for Sodium-Ion Batteries

Electronic structure engineering on electrode materials could bring in a new mechanism to achieve high energy and high power densities in sodium ion batteries. Herein, we design and create Co vacancies at the interface of atomically thin CoSe₂ /graphene heterostructure and obtain Co_1-x Se₂ /graphene heterostructure electrode materials that facilitate significant Na⁺ intercalation pseudocapacitance. Density functional theory (DFT) calculation suggests that the Na⁺ adsorption energy is dramatically increased, and the Na⁺ diffusion barrier is remarkably reduced due to the introduction of Co vacancy. The optimized electrode delivers a superior capacity of 673.6 mAh g^-1 at 0.1 C, excellent rate capability of 576.5 mAh g^-1 at 2.0 C and ultra-long life up to 2000 cycles. Kinetics analysis indicates that the enhanced Na⁺ storage is mainly attributed to the intercalation pseudocapacitance induced by Co vacancies. This work suggests that the creation of cation vacancy could bestow heterostructured electrode materials with pseudocapacitive Na⁺ intercalation for high-capacity and high-rate energy storage.

Metal-Organic Framework-Derived ZnSe- and Co0.85Se-Filled Porous Nitrogen-Doped Carbon Nanocubes Interconnected by Reduced Graphene Oxide for Sodium-Ion Battery Anodes

Transition-metal selenides have been considered as one of the most promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacity and excellent rate performance. However, rapid capacity decay and poor cycling stability limit their practical application as the anode for SIBs. Carbon coating is one of the most effective ways to solve the above problems, but the thickness and uniformity of the coating layer are difficult to control. Herein, we successfully synthesize metal-organic framework (MOF)-derived porous N-doped carbon nanocubes homogeneously filled with ZnSe and Co_0.85Se and interconnected by reduced graphene oxide (ZCS@NC@rGO). ZCS@NC@rGO with more active sites and the synergistic effect of the ZnSe and Co_0.85Se heterojunction can enhance the sodium storage performance. The porous carbon nanocubes effectively prevent the agglomeration of active particles, and the rGO acting as a carbon network can significantly buffer the inevitable volume changes. At the same time, carbon nanocubes and the rGO are interconnecting to form a conductive network to accelerate electron transfer. Based on the aforementioned advantages, the ZCS@NC@rGO electrode shows an excellent sodium storage performance. Our investigation opens up a new horizon for the rational design of transition-metal selenide anodes for SIBs with a unique structure.

Fabrication of CoSe@NC nanocubes for high performance potassium ion batteries

Potassium-ion batteries (PIBs) are considered as a promising candidate for large-scale energy storage. While exploring suitable anode materials are of vital need for the practical applications of PIBs. Herein, a well-designed heterostructured anode material CoSe nanocubes wrapped by N-doped carbon (CoSe@NC), has been successfully fabricated by simple annealing ZIF-67 nanocubes followed by in-situ selenization process. It is noted that ZIF-67 nanocubes are used as an effective template for the formation of porous structure, which can facilitate the construction of heterogeneous interface between CoSe and N-doped carbon (NC), effectively stabilizing CoSe with conversion reaction product Co⁰, increasing the diffusion mobility of electrons and K⁺-ions, and alleviating huge volume change. As expected, the heterostructured CoSe@NC nanocubes exhibit excellent K⁺-storage performance, which can display a rather high initial charge capacity (388.7 mAh g^-1 at 0.1 A g^-1 with the columbic efficiency of 70%), superior cyclic stability (309.6 mA h g^-1 after 500 cycles at 2 A g^-1), and exceptional rate capability (365.9 mAh g^-1 at 2 A g^-1). In terms of the low-cost and facile production approach for CoSe@NC, which makes the CoSe@NC a promising anode material for PIBs.

Flower-like Spherical α-Ni(OH)2 Derived NiP2 as Superior Anode Material of Sodium-Ion Batteries

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions result in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, NiP₂ nanoparticles encapsulated in three-dimensional graphene (NiP₂ @rGO) were obtained from the flower-like spherical α-Ni(OH)₂ by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, the NiP₂ @rGO composite shows an excellent cycling performance (117 mA h g^-1 at 10 A g^-1 after 8000 cycles). The outstanding electrochemical performance of NiP₂ @rGO is ascribed to the synergistic effect of the rGO and NiP₂ . The rGO wrapped on the NiP₂ nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP₂ nanoparticles with graphene greatly reduces the aggregation and pulverization of NiP₂ nanoparticles during the discharge/charge process. This study may shed light on the construction of high-performance anode materials for sodium-ion batteries and to other electrode materials.

Yolk-shell structured CoSe2/C nanospheres as multifunctional anode materials for both full/half sodium-ion and full/half potassium-ion batteries

Transition metal selenides (TMSs) are suitable for SIBs and PIBs owing to their satisfactory theoretical capacity and superior electrical conductivity. However, the large radius of Na+/K+ easily leads to sluggish kinetics and poor conductivity, which hinder the development of SIBs and PIBs. Structure design is an effective method to solve these obstacles. In this study, Co2+ ions combined with glycerol molecules to form self-assembled nanospheres at first, and then they were in situ converted into CoSe2 nanoparticles embedded in a carbon matrix during the selenization process. This structure has three-dimensional ion diffusion channels that can effectively hamper the aggregation of metal compound nanoparticles. Meanwhile, the CoSe2/C of the yolk-shell structure and a large number of pores help alleviate volume expansion and facilitate electrolyte wettability. These structural advantages of CoSe2/C endow it with remarkable electrochemical performances for full/half SIBs and full/half PIBs. The obtained CoSe2/C exhibits superior stability and excellent performance (312.1 mA h g-1 at 4 A g-1 after 1600 cycles) for SIBs. When it is used as an anode material for PIBs, 369.2 mA h g-1 can be retained after 200 cycles at 50 mA g-1 and 248.1 mA h g-1 can be retained after 200 cycles at 500 mA g-1; in addition, CoSe2/C also shows superior rate capacity (186.4 mA h g-1 at 1000 mA g-1). A series of ex situ XRD measurements were adapted to explore the possible conversion mechanism of CoSe2/C as the anode for PIBs. It is worth noting that the full-cell of CoSe2/C//Na3V2(PO4)3@rGO for SIBs and the full-cell of CoSe2/C//PTCDA-450 for PIBs were successfully assembled. The relationship between the structure and performance of CoSe2/C was investigated through density functional theory (DFT).

Self-assembly of carbon nanotubes on a hollow carbon polyhedron to enhance the potassium storage cycling stability of metal organic framework-derived metallic selenide anodes

Potassium-ion batteries (PIBs) is increasingly studied because of their suitable redox potential and high natural abundance. However, potential anode materials with long-term cycling stability are still in high demand because of the large radius of K⁺. Herein, an MOF-derived hierarchical carbon structure and the self-assembly of CNTs on hollow carbon polyhedrons are used as carbon matrices to disperse and stabilize metal selenides(Co-Se@CNNCP). When the hybrid is utilized in PIBs, it displays a specific capacity of 410 mA h g^-1 at 0.1 A g^-1 after 80 cycles and 253 mA h g^-1 at 0.5 A g^-1 after 200 cycles with a capacity retention of 100%, while the metal selenides dispersed on hollow carbon polyhedrons without CNTs (Zn-Co-Se@NCP) lose 86% of their capacity after 200 cycles. The superior cycling stability of the hybrid is mainly attributed to the large amounts of CNTs suppressing the agglomeration of the metal selenide nanoparticles on the surface, and the hollow carbon polyhedrons cause a high structural integrity during the repreated K⁺ insertion and extraction process. This work offers a feasible route to design a hierarchical carbon matrix for use as the anode materials of PIBs with long-term cycling stability.