Formation of Hierarchical Cu-Doped CoSe2 Microboxes via Sequential Ion Exchange for High-Performance Sodium-Ion Batteries

Integrating anti-aggregation Ta-Se motifs into copper selenide for fast and robust sodium-ion storage

We report a novel bimetallic selenide Cu3TaSe4 anode for sodium-ion batteries synthesized via a one-step solid-state method. The integration of Ta-Se motifs into copper selenide forms a cubic grid structure that prevents copper atom aggregation and mitigates electrode failure. Cu3TaSe4 exhibits a high specific capacity of 305 mAh g-1 at 1 C, excellent rate performance of 286 mAh g-1 at 50 C, and superior cycling stability with 272 mAh g-1 after 3500 cycles at 20 C. This work demonstrates the potential of bimetallic selenides in enhancing sodium-ion battery performance.

Progress on Copper-Based Anode Materials for Sodium-Ion Batteries

Fossil fuels have clearly failed to meet people's growing energy needs due to their limited reserves, potential pollution of the environment, and high costs. The development of cleaner, renewable energy sources as well as secondary batteries for energy storage is imminent, in a modern society where energy demand is soaring. Sodium-ion batteries (SIBs) have become the focus of large-scale energy storage systems as a promising alternative to lithium-ion batteries. The development of SIBs relies on the construction of high performance electrode materials. The design of low cost and high performance anode materials is a key link in this regard. Copper-based anodes are characterized by high theoretical capacity, abundant reserves, low cost and environmental friendliness. A variety of copper-based anode materials, which include cobalt oxides, sulfides, selenides and phosphides, have been synthesized and evaluated in the scientific literature for sodium storage. In detail, the preparation methods, response mechanisms, strengths and weaknesses, the relationship between morphology structure and electrochemical performance are discussed, as well as highlighting strategies to improve the electrochemical performance of copper-based anode materials. Finally, we offer our perspective on the challenges and potential for the development of copper-based anodes as a means of developing practical and high performing SIBs.

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.

Trisodium Citrate as a Double-Edged Sword: Selective Etching Prussian Blue Analog Nanocubes into Orthogonal Frustums and Their Derivatives for Supercapacitors

The construction of novel structured Prussian blue analogs (PBAs) by chemical etching has attracted the most attention to PBA derivatives with outstanding performance. In this work, the unprecedented PBA orthogonal frustums are first prepared from nanocubes through a selective chemical etching approach using trisodium citrate as an etchant. The citrate ions can chelate with nickel species from the edges/corners of NiCo-PBA nanocubes and then disintegrate NiCo-PBAs resulting in the generation of NiCo-PBA orthogonal frustums. The derived CoNi2S4/Co0.91S composites still inherit the original orthogonal frustum structure and possess outstanding supercapacitor performance. This study develops a popularized method to construct novel structured PBAs and brings inspiration for designing PBA-based electrodes with advanced electrochemical performance.

From lab to field: Prussian blue frameworks as sustainable cathode materials

Prussian blue and Prussian blue analogues have attracted increasing attention as versatile framework materials with a wide range of applications in catalysis, energy conversion and storage, and biomedical and environmental fields. In terms of energy storage and conversion, Prussian blue-based materials have emerged as suitable candidates of growing interest for the fabrication of batteries and supercapacitors. Their outstanding electrochemical features such as fast charge-discharge rates, high capacity and prolonged cycling life make them favorable for energy storage application. Furthermore, Prussian blue and its analogues as rechargeable battery anodes can advance significantly by the precise control of their structure, morphology, and composition at the nanoscale. Their tunable structural and electronic properties enable the detection of many types of analytes with high sensitivity and specificity, and thus, they are ideal materials for the development of sensors for environmental detection, disease trend monitoring, and industrial safety. Additionally, Prussian blue-based catalysts display excellent photocatalytic performance for the degradation of pollutants and generation of hydrogen. Specifically, their excellent light capturing and charge separation capabilities make them stand out in photocatalytic processes, providing a sustainable option for environmental remediation and renewable energy production. Besides, Prussian blue coatings have been studied particularly for corrosion protection, forming stable and protective layers on metal surfaces, which extend the lifespan of infrastructural materials in harsh environments. Prussian blue and its analogues are highly valuable materials in healthcare fields such as imaging, drug delivery and theranostics because they are biocompatible and their further functionalization is possible. Overall, this review demonstrates that Prussian blue and related framework materials are versatile and capable of addressing many technical challenges in various fields ranging from power generation to healthcare and environmental management.

Revealing the Dynamic Lithiation Process of Copper Disulfide by in Situ TEM

Transition metal oxides, fluorides, and sulfides are extensively studied as candidate electrode materials for lithium-ion batteries driven by the urgency of developing next-generation higher energy density lithium batteries. These conversion-type electrode materials often require nanosized active materials to enable a "smooth" lithiation and de-lithiation process during charge/discharge cycles, determined by their size, structure, and phase. Herein, the structural and chemical changes of Copper Disulfide (CuS2) hollow nanoparticles during the lithiation process through an in situ transmission electron microscopy (TEM) method are investigated. The study finds the hollow structure of CuS2 facilitates the quick formation of fluidic Li2S "drops," accompanied by a de-sulfurization to the Cu7S4 phase. Meanwhile, the metallic Cu phase emerges as fine nanoparticles and grows into nano-strips, which are embedded in the Li2S/Cu7S4 matrix. These complex nanostructured phases and their spatial distribution can lead to a low de-lithiation barrier, enabling fast reaction kinetics.

Rod-like Ni-CoS2@NC@C: Structural design, heteroatom doping and carbon confinement engineering to synergistically boost sodium storage performance

Currently, conversion-type transition metal sulfides have been extensively favored as the anodes for sodium-ion batteries due to their excellent redox reversibility and high theoretical capacity; however, they generally suffer from large volume expansion and structural instability during repeatedly Na+ de/intercalation. Herein, spatially dual-confined Ni-doped CoS2@NC@C microrods (Ni-CoS2@NC@C) are developed via structural design, heteroatom doping and carbon confinement to boost sodium storage performance of the material. The morphology of one-dimensional-structured microrods effectively enlarges the electrode/electrolyte contact area, while the confinement of dual-carbon layers greatly alleviates the volume change-induced stress, pulverization, agglomeration of the material during charging and discharging. Moreover, the introduction of Ni improves the electrical conductivity of the material by modulating the electronic structure and enlarges the interlayer distance to accelerate Na+ diffusion. Accordingly, the as-prepared Ni-CoS2@NC@C exhibits superb electrochemical properties, delivering the satisfactory cycling performance of 526.6 mA h g-1 after 250 cycles at 1 A g-1, excellent rate performance of 410.9 mA h g-1 at 5 A g-1 and superior long cycling life of 502.5 mA h g-1 after 1,500 cycles at 5 A g-1. This study provides an innovative idea to improve sodium storage performance of conversion-type transition metal sulfides through the comprehensive strategy of structural design, heteroatom doping and carbon confinement.

Achieving High-Rate and Stable Sodium-Ion Storage by Constructing Okra-Like NiS2/FeS2@Multichannel Carbon Nanofibers

Transition metal sulfides (TMSs) are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, the relatively low electrical conductivity, large volume variation, and easy aggregation/pulverization of active materials seriously hinder their practical application. Herein, okra-like NiS2/FeS2 particles encapsulated in multichannel N-doped carbon nanofibers (NiS2/FeS2@MCNFs) are fabricated by a coprecipitation, electrospinning, and carbonization/sulfurization strategy. The combined advantages arising from the hollow multichannel structure in carbon skeleton and heterogeneous NiS2/FeS2 particles with rich interfaces can provide facile ion/electron transfer paths, ensure boosted reaction kinetics, and help maintain the structural integrity, thereby resulting in a high reversible capacity (457 mA h g-1 at 1 A g-1), excellent rate performance (350 mA h g-1 at 5 A g-1), and outstanding long-term cycling stability (93.5% retention after 1100 cycles). This work provides a facile and efficient synthetic strategy to develop TMS-based heterostructured anode materials with high-rate and stable sodium storage properties.

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.

Boosting Potassium Storage via Multifunctional Interface with High Lattice-Matching

Atomic-scale interface engineering is a prominent strategy to address the large volume expansions and sluggish redox kinetics for reinforcing K-storage. Here, to accelerate charge transport and lower the activation energy, dual carbon-modified interfacial regions are synthesized with high lattice-matching degree, which is formed from a CoSe2 /FeSe2 heterostructure coated onto hollow carbon fibers. State-of-the-art characterization techniques and theoretical analysis, including ex-situ soft X-ray absorption spectroscopy, synchrotron X-ray tomography, ultrasonic transmission mapping, and density functional theory, are conducted to probe local atomic structure evolution, mechanical degradation mechanisms, and ion/electron migration pathways. The results suggest that the heterostructure composed of the same crystal system and space group can sharply regulate the redox kinetics of transition metal selenium and dual carbon-modified approach can tailor physicochemical degradation. Overall, this work presents the design of a stable heterojunction synergistic superior hollow carbon substrate, inspiring a pathway of interface engineering strategy toward high-performance electrode.

Rational Design of Hollow Structural Materials for Sodium-Ion Battery Anodes

The development of sodium-ion battery (SIB) anodes is still hindered by their rapid capacity decay and poor rate capabilities. Although there have been some new materials that can be used to fabricate stable anodes, SIBs are still far from wide applications. Strategies like nanostructure construction and material modification have been used to prepare more robust SIB anodes. Among all the design strategies, the hollow structure design is a promising method in the development of advanced anode materials. In the past decade, research efforts have been devoted to modifying the synthetic route, the type of templates, and the interior structure of hollow structures with high capacity and stability. A brief introduction is made to the main material systems and classifications of hollow structural materials first. Then different morphologies of hollow structural materials for SIB anodes from the latest reports are discussed, including nanoboxes, nanospheres, yolk shells, nanotubes, and other more complex shapes. The most used templates for the synthesis of hollow structrual materials are covered and the perspectives are highlighted at the end. This review offers a comprehensive discussion of the synthesis of hollow structural materials for SIB anodes, which could be potentially of use to research areas involving hollow materials design for batteries.

Synergetic Sn Incorporation-Zn Substitution in Copper-Based Sulfides Enabling Superior Na-Ion Storage

Transition-metal sulfides have been regarded as perspective anode candidates for high-energy Na-ion batteries. Their application, however, is precluded severely by either low charge storage or huge volumetric change along with sluggish reaction kinetics. Herein, an effective synergetic Sn incorporation-Zn substitution strategy is proposed based on copper-based sulfides. First, Na-ion storage capability of copper sulfide is significantly improved via incorporating an alloy-based Sn element. However, this process is accompanied by sacrifice of structural stability due to the high Na-ion uptake. Subsequently, to maintain the high Na-ion storage capacity, and concurrently improve cycling and rate capabilities, a Zn substitution strategy (taking partial Sn sites) is carried out, which could significantly promote Na-ion diffusion/reaction kinetics and relieve mechanical strain-stress within the crystal framework. The synergetic Sn incorporation and Zn substitution endow copper-based sulfides with high specific capacity (≈560 mAh g-1 at 0.5 A g-1 ), ultrastable cyclability (80 k cycles with ≈100% capacity retention), superior rate capability up to 200 A g-1 , and ultrafast charging feature (≈4 s per charging with ≈190 mAh g-1 input). This work provides in-depth insights for developing superior anode materials via synergetic multi-cation incorporation/substitution, aiming at solving their intrinsic issues of either low specific capacity or poor cyclability.

Metal Selenides Find Plenty of Space in Architecting Advanced Sodium/Potassium Ion Batteries

The rapid evolution of smart grid system urges researchers on exploiting systems with properties of high-energy, low-cost, and eco-friendly beyond lithium-ion batteries. Under the circumstances, sodium- and potassium-ion batteries with the semblable work mechanism to commercial lithium-ion batteries, hold the merits of cost-effective and earth-abundant. As a result, it is deemed a promising candidate for large-scale energy storage devices. Exploiting appropriate active electrode materials is in the center of the spotlight for the development of batteries. Metal selenides with special structures and relatively high theoretical capacity have aroused broad interest and achieved great achievements. To push the smooth development of metal selenides and enhancement of the electrochemical performance of sodium- and potassium-ion batteries, it is vital to grasp the inherent properties and electrochemical mechanisms of these materials. Herein, the state-of-the-art development and challenges of metal selenides are summarized and discussed. Meanwhile, the corresponding electrochemical mechanism and future development directions are also highlighted.

Carboxyl and polyamine groups functionalized polyacrylonitrile fibers for efficient recovery of copper ions from solution

Heavy metals (e.g., Cu) in wastewater are attractive resources for diverse applications, and adsorption is a promising route to recovery of heavy metals from wastewater. However, high-performance adsorbents with high adsorption capacity, speed, and stability remain challenging. Herein, chelating fibers were prepared by chemically grafting amine and carboxyl groups onto the polyacrylonitrile fiber surface and used in the wastewater's adsorption of Cu2+. The adsorption behavior of Cu2+ on the fibers was systematically investigated, and the post-adsorption fibers were comprehensively characterized to uncover the adsorption mechanism. The results show that chelated fiber has a 136.3 mg/g maximum capacity for Cu2+ adsorption at pH = 5, and the whole adsorption process could reach equilibrium in about 60 min. The adsorption process corresponds to the quasi-secondary kinetic and Langmuir models. The results of adsorption, FTIR, and XPS tests indicate that the synergistic coordination of -COOH and -NH2 plays a leading role in the rapid capture of Cu2+. In addition, introducing hydrophilic groups facilitates the rapid contact and interaction of the fibers with Cu2+ in the solution. After being used five times, the fiber's adsorption capacity remains at over 90% of its original level.

Copper-doped layered Fe2VO4 nanorods for aqueous zinc-ion batteries

Zinc-ion batteries (ZIBs) have attracted an increasing attention as a potential low-cost, environmentally friendliness, and high-safety energy storage system. Among them, transition metal vanadates with high oxidation state vanadium have great potential in ZIBs cathode research due to their high theoretical capacity. However, many vanadate particles still inevitably suffer from low ion mobility, low electrical conductivity and stability. Cation doping or compositing is an effective pathway capable of enhancing electrical conductivity. In this work, layered Cu-Fe2VO4 porous nanorods are obtained by introducing Cu2+ into MIL-88A(Fe) (a metal-organic framework; MIL stands for materials from Institute Lavoisier) and further ion-exchanged with NH4VO3, exhibiting excellent zinc storage properties as an cathode. The existence of oxygen vacancies and the change of electronic structure caused by Cu2+ substituting part of Fe2+ enhanced the conductivity and electron transfer rate. It delivers a reversible discharge capacity of 237 mAh/g at 0.3 A/g and a satisfactory high rate capacity of 126 mAh/g after 30 cycles at 5 A/g, and stable cycling performance (198 mAh/g after 1000 cycles at 1 A/g). Furthermore, the energy density can reached to 230.97 Wh kg-1 at 208.6 W kg-1. The assembled quasi-solid-state ZIBs maintain a high capacitance retention of 75% after 8000 cycles at 1 A/g.

In-situ-grown multidimensional Cu-doped Co1-xS2@MoS2 on N-doped carbon nanofibers as anode materials for high-performance alkali metal ion batteries

Transition metal sulfides with the high theoretical capacity and low cost have been considered as advanced anode candidate for alkali metal ion batteries, but suffered from unsatisfactory electrical conductivity and huge volume expansion. Herein, a multidimensional structure Cu-doped Co1-xS2@MoS2 in-situ-grown on N-doped carbon nanofibers (denoted as Cu-Co1-xS2@MoS2 NCNFs) have been elaborately constructed for the first time. The bimetallic zeolitic imidazolate framework CuCo-ZIFs were encapsulated in the one-dimensional (1D) NCNFs through an electrospinning route and then on which the two-dimensional (2D) MoS2 nanosheets were in-situ grown via a hydrothermal process. The architecture of 1D NCNFs can effectively shorten ion diffusion path and enhance electrical conductivity. Besides, the formed heterointerface between MOF-derived binary metal sulfides and MoS2 can provide extra active centers and accelerate reaction kinetics, which guarantee a superior reversibility. As expected, the resulting Cu-Co1-xS2@MoS2 NCNFs electrode delivers excellent specific capacity of Na-ion batteries (845.6 mAh/g at 0.1 A/g), Li-ion batteries (1145.7 mAh/g at 0.1 A/g), and K-ion batteries (474.3 mAh/g at 0.1 A/g). Therefore, this innovative design strategy will bring a meaningful prospect for developing high-performance multi-component metal sulfides electrode for alkali metal ion batteries.

Porous prussian blue analogs derived nickel-iron bimetallic phosphide nanocubes on conductive hollow mesoporous carbon nanospheres for stable and flexible high-performance supercapacitor electrode

Nickel-iron bimetallic phosphide (Ni-Fe-P) is the ideal battery-type materials for supercapacitor in virtue of high theoretical specific capacitance. Nevertheless, its actual adhibition is astricted on account of inferior rate capability and cyclic stability. Herein, we constructed hierarchical core-shell nanocomposites with hollow mesoporous carbon nanospheres (HMCS) packaged via prussian blue analogs derived Ni-Fe-P nanocubes (Ni-Fe-P@HMCS), as a positive electrode for hybrid supercapacitor (HSC). Profiting from the cooperative effects of Ni-Fe-P nanocubes with small size and good dispersibility, and HMCS with continuously conductive network, the Ni-Fe-P@HMCS composite electrode with abundantly porous architectures presents an ultrahigh gravimetric specific capacity for 739.8 C g-1 under 1 A g-1. Specially, the Ni-Fe-P@HMCS electrode presents outstanding rate capability of 78.4% (1 A g-1 to 20 A g-1) and cyclic constancy for 105% after 5000 cycles. Density functional theory implies that the composite electrode possesses higher electrical conductivity than bare Ni-Fe-P electrode by reason of the incremental charge density, and the electrons transferring from NiFe3P4 to HMCS layers. Additionally, the assembled Ni-Fe-P@HMCS//HMCS HSC facility delivers the high energy density for 64.1 Wh kg-1, remarkable flexibility and mechanical stability. Thus, this work proffers a viable and efficacious measure to construct ultra-stability electrode for high-performance portable electronic facilities.

Unveiling the Nature of Superior Sodium Storage in the CoSe2/rGO Nanocomposite

Sodium-ion batteries (SIBs) are considered the most promising alternatives to lithium-ion batteries (LIBs) due to the abundant availability of sodium and their cost-effectiveness. Transition metal selenides (TMSes) are considered promising anodes for SIBs due to their economic efficiency and high theoretical capacity. Nevertheless, overcoming the challenges of sluggish reaction kinetics and severe structural damage is crucial to improving cycle life and rate capability. Herein, a simple microwave hydrothermal process was used to synthesize a nanocomposite of CoSe2 nanoparticles uniformly anchored on reduced graphene oxide nanosheets (CoSe2/rGO). The influences of rGO on the structure and electrochemical performance and Na+ diffusion kinetics are investigated through a series of characterization and electrochemical tests. The resulting CoSe2/rGO nanocomposite exhibits a remarkable initial specific capacity of 544 mAh g-1 at 0.5 A g-1, impressive rate capability (368 mAh g-1 at 20 A g-1), and excellent cycle life and maintains 348 mAh g-1 at 5 A g-1 over 1200 cycles. In addition, the in situ electrochemical impedance spectroscopy (EIS), ex situ X-ray diffraction (XRD), and transmission electron microscopy (TEM) tests are selected to further investigate the sodium storage mechanism.

Transition metal chalcogenides for next-generation energy storage

Transition-metal chalcogenide nanostructures provide a unique material platform to engineer next-generation energy storage devices such as lithium-ion, sodium-ion, and potassium-ion batteries and flexible supercapacitors. The transition-metal chalcogenide nanocrystals and thin films have enhanced electroactive sites for redox reactions and hierarchical flexibility of structure and electronic properties in the multinary compositions. They also consist of more earth-abundant elements. These properties make them attractive and more viable new electrode materials for energy storage devices compared to the traditional materials. This review highlights the recent advances in chalcogenide-based electrodes for batteries and flexible supercapacitors. The viability and structure-property relation of these materials are explored. The use of various chalcogenide nanocrystals supported on carbonaceous substrates, two-dimensional transition metal chalcogenides, and novel MXene-based chalcogenide heterostructures as electrode materials to improve the electrochemical performance of lithium-ion batteries is discussed. The sodium-ion and potassium-ion batteries offer a more viable alternative to lithium-ion technology as they consist of readily available source materials. Application of various transition metal chalcogenides such as MoS2, MoSe2, VS2, and SnSx, composite materials, and heterojunction bimetallic nanosheets composed of multi-metals as electrodes to enhance the long-term cycling stability, rate capability, and structural strength to counteract the large volume expansion during the ion intercalation/deintercalation processes is highlighted. The promising performances of layered chalcogenides and various chalcogenide nanowire compositions as electrodes for flexible supercapacitors are also discussed in detail. The review also details the progress made in new chalcogenide nanostructures and layered mesostructures for energy storage applications.

Advance of Prussian Blue-Derived Nanohybrids in Energy Storage: Current Status and Perspective

Great changes have occurred in the energy storage area in recent years as a result of rapid economic expansion. People have conducted substantial research on sustainable energy conversion and storage systems in order to mitigate the looming energy crisis. As a result, developing energy storage materials is critical. Materials with an open frame structure are known as Prussian blue analogs (PBAs). Anode materials for oxides, sulfides, selenides, phosphides, borides, and carbides have been extensively explored as anode materials in the field of energy conversion and storage in recent years. The advantages and disadvantages of oxides, sulfides, selenides, phosphides, borides, carbides, and other elements, as well as experimental methodologies and electrochemical properties, are discussed in this work. The findings reveal that employing oxides, sulfides, selenides, phosphides, borides, and other electrode materials to overcome the problems of low conductivity, excessive material loss, and low specific volume is ineffective. Therefore, this review intends to address the issues of diverse energy storage materials by combining multiple technologies to manufacture battery materials with low cost, large capacity, and extended service life.

Synergistically Achieving Superior Sodium Storage of Metal Selenides by Constructing N-Doped Carbon Foams and Utilizing Cu-Driven Replacement Reaction

Metal selenides are considered as one of the most promising anode materials for Na-ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na⁺ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical-blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N-doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high-efficiency utilization of active components and high structural stability. On the other hand, Cu-driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether-based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as-obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g^-1 up to 8 A g^-1 ) and excellent cycling stability (347.7 mAh g^-1 at 4.0 A g^-1 after 1200 cycles).

MOF-derived nitrogen-doped porous carbon nanofibers with interconnected channels for high-stability Li+/Na+ battery anodes

Heteroatom-doped porous carbon materials have been widely used as anode materials for Li-ion and Na-ion batteries, however, improving the specific capacity and long-term cycling stability of ion batteries remains a major challenge. Here, we report a facile based metal-organic framework (MOFs) strategy to synthesize nitrogen-doped porous carbon nanofibers (NCNFs) with a large number of interconnected channels that can increase the contact area between the material and the electrolyte, shorten the diffusion distance between Li+/Na+ and the electrolyte, and relieve the volume expansion of the electrode material during cycling; the doping of nitrogen atoms can improve the conductivity and increase the active sites of the carbon material, can also affect the microstructure and electron distribution of the electrode material, thereby improving the electrochemical performance of the material. As expected, the obtained NCNFs-800 exhibited excellent electrochemical performance with high reversible capacity (for Li+ battery anodes: 1237 mA h g-1 at 100 mA g-1 after 200 cycles, for Na+ battery anodes: 323 mA h g-1 at 100 mA g-1 after 150 cycles) and long-term cycling stability (for Li+ battery anodes: 635 mA h g-1 at 2 A g-1 after 5000 cycles, for Na+ battery anodes: 194 mA h g-1 at 2 A g-1 after 5000 cycles).

Rational Construction of C@Sn/NSGr Composites as Enhanced Performance Anodes for Lithium Ion Batteries

As a potential anode material for lithium-ion batteries (LIBs), metal tin shows a high specific capacity. However, its inherent "volume effect" may easily turn tin-based electrode materials into powder and make them fall off in the cycle process, eventually leading to the reduction of the specific capacity, rate and cycle performance of the batteries. Considering the "volume effect" of tin, this study proposes to construct a carbon coating and three-dimensional graphene network to obtain a "double confinement" of metal tin, so as to improve the cycle and rate performance of the composite. This excellent construction can stabilize the tin and prevent its agglomeration during heat treatment and its pulverization during cycling, improving the electrochemical properties of tin-based composites. When the optimized composite material of C@Sn/NSGr-7.5 was used as an anode material in LIB, it maintained a specific capacity of about 667 mAh g^-1 after 150 cycles at the current density of 0.1 A g^-1 and exhibited a good cycle performance. It also displayed a good rate performance with a capability of 663 mAh g^-1, 516 mAh g^-1, 389 mAh g^-1, 290 mAh g^-1, 209 mAh g^-1 and 141 mAh g^-1 at 0.1 A g^-1, 0.2 A g^-1, 0.5 A g^-1, 1 A g^-1, 2 A g^-1 and 5 A g^-1, respectively. Furthermore, it delivered certain capacitance characteristics, which could improve the specific capacity of the battery. The above results showed that this is an effective method to obtain high-performance tin-based anode materials, which is of great significance for the development of new anode materials for LIBs.

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.

Oxygen-Deficient α-MnO2 Nanotube/Graphene/N, P Codoped Porous Carbon Composite Cathode To Achieve High-Performing Zinc-Ion Batteries

A major drawback of α-MnO₂-based zinc-ion batteries (ZIBs) is the poor rate performance and short cycle life. Herein, an oxygen-deficient α-MnO₂ nanotube (V_O-α-MnO₂)-integrated graphene (G) and N, P codoped cross-linked porous carbon nanosheet (CNPK) composite (V_O-α-MnO₂/CNPK/G) has been prepared for advanced ZIBs. The introduction of V_O in MnO₂ can decrease the value of the Gibbs free energy of Zn²⁺ adsorption near V_O (ca. -0.73 eV) to the thermal neutral value. The thermal neutral value demonstrates that the Zn²⁺ adsorption/desorption process on V_O-α-MnO₂ is more reversible than that on α-MnO₂. The as-made Zn/V_O-α-MnO₂ battery is able to deliver a large capacity of 305.0 mAh g^-1 and high energy density up to 408.5 Wh kg^-1. The good energy storage properties can be attributed to V_O. Additionally, the V_O-α-MnO₂/CNPK/G composite possesses the structure of nanotube arrays, which results from the vertical growth of α-MnO₂ nanotubes on CNPK. This unique array structure helps to realize fast ion/electron transfer and stable microstructure. The electrochemical performance of V_O-α-MnO₂ has been comprehensively improved by compositing with G and CNPK. The V_O-α-MnO₂/CNPK/G can achieve capacity up to 405.2 mAh g^-1, energy density of 542.2 Wh kg^-1, and long cycle life (80% capacity retention after 2000 cycles).

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.

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.

Enhancing the bifunctional activity of CoSe2 nanocubes by surface decoration of CeO2 for advanced zinc-air batteries

The coupling of oxygen evolution and reduction reactions (OER and ORR) plays a key role in rechargeable Zn-air batteries (ZABs). However, both OER and ORR still suffer from sluggish kinetics, even when using the mainstream precious metal-based catalysts. Herein, oxygen vacancies-rich CeO₂ decorated CoSe₂ nanocubes are proposed as a novel air electrode to drive OER and ORR for ZABs. The resultant CeO₂ coupled CoSe₂ nanocubes (CeO₂@CoSe₂-NCs) catalyst exhibits a significantly enhanced bifunctional activity relative to the pristine CoSe₂-NCs and the pristine CeO₂. Moreover, an assembled ZABs using this CeO₂@CoSe₂-NCs electrode delivers a high output power density of 153 mW cm^-2 and a long-life stability over 400 cycles, superior to the benchmark Pt/C-IrO₂ electrode. Theoretical calculations reveal that the electronic interaction and oxygen vacancies in CeO₂@CoSe₂-NCs contribute to efficient oxygen electrocatalysis. This protocol provides a promising approach of constructing oxygen vacancies in hybrid catalysts for energy conversion and storage devices.

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.

KOH activated nitrogen and oxygen co-doped tubular carbon clusters as anode material for boosted potassium-ion storage capability

Carbon nanomaterials have become a promising anode material for potassium-ion batteries (KIBs) due to their abundant resources, low cost, and excellent conductivity. However, among carbon materials, the sluggish reaction kinetics and inferior cycle life severely restrict their commercial development as KIBs anodes. It is still a huge challenge to develop carbon materials with various structural advantages and ideal electrochemical properties. Therefore, it is imperative to find a carbon material with heteroatom doping and suitable nanostructure to achieve excellent electrochemical performance. Benefiting from a Na₂SO₄template-assisted method and KOH activation process, the KOH activated nitrogen and oxygen co-doped tubular carbon (KNOCTC) material with a porous structure exhibits an impressive reversible capacity of 343 mAh g^-1at 50 mA g^-1and an improved cyclability of 137 mAh g^-1at 2 A g^-1after 3000 cycles with almost no capacity decay. The kinetic analysis indicates that the storage mechanism in KNOCTC is attributed to the pseudocapacitive process during cycling. Furthermore, the new synthesis route of KNOCTC provides a new opportunity to explore carbon-based potassium storage anode materials with high capacity and cycling performance.

Nanostructure and Advanced Energy Storage: Elaborate Material Designs Lead to High-Rate Pseudocapacitive Ion Storage

The drastic need for development of power and electronic equipment has long been calling for energy storage materials that possess favorable energy and power densities simultaneously, yet neither capacitive nor battery-type materials can meet the aforementioned demand. By contrast, pseudocapacitive materials store ions through redox reactions with charge/discharge rates comparable to those of capacitors, holding the promise of serving as electrode materials in advanced electrochemical energy storage (EES) devices. Therefore, it is of vital importance to enhance pseudocapacitive responses of energy storage materials to obtain excellent energy and power densities at the same time. In this Review, we first present basic concepts and characteristics about pseudocapacitive behaviors for better guidance on material design researches. Second, we discuss several important and effective material design measures for boosting pseudocapacitive responses of materials to improve rate capabilities, which mainly include downsizing, heterostructure engineering, adding atom and vacancy dopants, expanding interlayer distance, exposing active facets, and designing nanosheets. Finally, we outline possible developing trends in the rational design of pseudocapacitive materials and EES devices toward high-performance energy storage.

Metal-organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries

Metal selenides, as potential alternative candidates for sodium storage, have promising applicability due to their high theoretical specific capacity. However, their huge volume change and sluggish electrode kinetics during sodium ion uptake and release processes can result in insufficient cycling life and inferior rate performance, hindering their practical application. Herein, nitrogen (N)-doped carbon-confined cobalt selenide anchored on multiwalled carbon nanotube networks (denoted as CoSe₂@NC/MWCNTs) was designed and successfully built through a selenization process with ZIF-67 MOF as the template. The existence of the interconnected MWCNT network plays a crucial role in not only enhancing the electronic conductivity and ion/electron-transfer efficiency but also ensuring structural stability. Consequently, the optimized CoSe₂@NC/MWCNTs composite delivers a high reversible capacity of 479.6 mA h g^-1 at a current rate of 0.2 A g^-1, accompanied by a 92.0% capacity retention over 100 cycles and a predominant rate performance of 227.4 mA h g^-1 even under 20 A g^-1 when examined as the anode in Na-ion batteries. Moreover, the kinetic behaviors were confirmed using CV profiles at various rates, as well as the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). Besides, the HRTEM images clearly reveal the sodium-ion storage mechanism of the CoSe₂ hybrid. These results make CoSe₂@NC/MWCNTs a prospective anode material in advanced sodium-ion batteries.

Bimetallic sulfide NiCo2S4 yolk-shell nanospheres as high-performance cathode materials for rechargeable magnesium batteries

Constructing bimetallic sulfides with ideal structures could effectively alleviate the poor cycling stability of rechargeable Mg batteries due to a bimetallic synergistic effect. An exquisite yolk-shell structured bimetallic sulfide NiCo₂S₄ synthesized via a two-step solvothermal hydrothermal method is investigated as a cathode material for rechargeable Mg batteries. With the bimetallic strategy and well-designed architecture, the as-synthesized yolk-shell NiCo₂S₄ exhibits outstanding Mg-storage performance, demonstrating a superior reversible capacity (270 mA h g^-1 at 50 mA h g^-1), a high rate capability, and a specific capacity retention of 91% over 400 cycles (2.2% capacity decay per cycle). The in-depth mechanism investigation reveals the two-step conversion reaction process and the bimetallic synergistic effect in the Mg-storage process. Based on DFT calculations and kinetic investigations, the bimetallic synergistic effect effectively alleviates the Jahn-Teller effect and distortion in the crystal lattices and increases active reaction sites, thus largely enhancing the electrochemical Mg-storage performance. The superior electrochemical performance of NiCo₂S₄ not only demonstrates the viability of the bimetallic strategy but also sheds light on the use of nanostructure design for high-performance cathode research.

Prussian-Blue Analogue-Derived Hollow Structured Co3 S4 /CuS2 /NiS2 Nanocubes as an Advanced Battery-Type Electrode Material for High-Performance Hybrid Supercapacitors

The facile and cost-effective fabrication of hybrid nanostructures comprised of hollow mixed metallic chalcogenides has attracted growing interest in the development of high-performance energy storage devices. Herein, multi-component (nickel-cobalt-copper-sulfides/selenides (NCCS/NCCSe)) hollow nanocubes (HNCs) are prepared via a single-step sulfurization/selenization process. The NCCS material shows interior HNCs, and the NCCSe material exhibits slightly formed porous cubes. Both the prepared materials demonstrate higher charge storage performance than the precursor NCC NCs owing to the improved surface morphology and addition of sulfur and selenium ions. Particularly, the NCCS HNCs electrode reveals superior specific capacity (capacitance) (70.32 mAh g^-1 (666.20 F g^-1 ) at 5 mA cm^-2 ) along with excellent cycling stability of 108.6% even after 10 000 cycles. Interestingly, the electrode delivers a good rate capability of 83.5% at a high current density of 20 mA cm^-2 . The feasibility of the battery-type NCCS HNCs as a positive electrode is explored by constructing an aqueous electrochemical hybrid capacitor (AEHC). The AEHC exhibits maximum energy and power densities of 23.15 Wh kg^-1 and 7899.08 W kg^-1 , respectively. Remarkably, it demonstrates superior long-life cycling stability even after 10 000 cycles (120.6% retention). The suitability of AEHC for practical application is also tested by driving electronic devices.

Constructing Heterostructured Bimetallic Selenides on an N-Doped Carbon Nanoframework as Anodes for Ultrastable Na-Ion Batteries

Transition-metal selenides have been recognized as a class of promising anode materials for sodium-ion batteries (SIBs) on account of their high capacity. Nevertheless, the sluggish conversion kinetics and rapid capacity decay caused by insufficient conductivity and volume change restrain their applications. Herein, hollow heterostructured bimetallic selenides embedded in an N-doped carbon nanoframework (H-CoSe₂/ZnSe@NC) were prepared via a facile template-engaged method. Benefiting from the rich defect at the phase boundary of the CoSe₂/ZnSe heterostructure, pre-reserved cavity, and enhanced structure rigidity, the abovementioned issues are resolved at once, and the accelerated charge transportation kinetics traced by spectroscopy techniques and theoretical calculations certify the interface effect in the capacity release. In addition, ex situ X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy all confirm the high-reversible electrochemical conversion mechanism in H-CoSe₂/ZnSe@NC. Together with a reasonable structural architecture and the highly reversible conversion reaction, H-CoSe₂/ZnSe@NC displays a prominent rate capacity (244.8 mA h g^-1 at 10 A g^-1) as well as an ultralong lifespan (10,000 cycles at 10 A g^-1), highlighting the significance of structure control in fabricating high-performance anodes for SIBs.

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...

Highly dispersive CoSe2 nanoparticles encapsulated in carbon nanotube-grafted multichannel carbon fibers as advanced anodes for sodium-ion half/full batteries

Highly dispersive CoSe2 nanoparticles encapsulated in carbon nanotube-grafted multichannel carbon fibers are synthesized through a confined-regulated interfacial engineering strategy, which delivers excellent electrochemical performance.

The rational design of nickel-cobalt selenides@selenium nanostructures by adjusting the synthesis environment for high-performance sodium-ion batteries

Different selenization products (from the perspectives of micromorphology and sodium storage performance) can be obtained via regulating the selenization environment.

Stabilizing V2O3 in carbon nanofiber flexible films for ultrastable potassium storage

Vanadium oxides, such as V2O3 and VO2, are expected to be potential anode materials for potassium-ion batteries (KIBs) on account of their high theoretical capacity, low price and natural abundance....

Interface-Driven Pseudocapacitance Endowing Sandwiched CoSe2/N-Doped Carbon/TiO2 Microcubes with Ultra-Stable Sodium Storage and Long-Term Cycling Stability

Cobalt diselenide (CoSe₂) has drawn great concern as an anode material for sodium-ion batteries due to its considerable theoretical capacity. Nevertheless, the poor cycling stability and rate performance still impede its practical implantation. Here, CoSe₂/nitrogen-doped carbon-skeleton hybrid microcubes with a TiO₂ layer (denoted as TNC-CoSe₂) are favorably prepared via a facile template-engaged strategy, in which a TiO₂-coated Prussian blue analogue of Co₃[Co(CN)₆]₂ is used as a new precursor accompanied with a selenization procedure. Such structures can concurrently boost ion and electron diffusion kinetics and inhibit the structural degradation during cycling through the close contact between the TiO₂ layer and NC-CoSe₂. Besides, this hybrid structure promotes the superior Na-ion intercalation pseudocapacitance due to the well-designed interfaces. The as-prepared TNC-CoSe₂ microcubes exhibit a superior cycling capability (511 mA h g^-1 at 0.2 A g^-1 after 200 cycles) and long cycling life (456 mA h g^-1 at 6.4 A g^-1 for 6000 cycles with a retention of 92.7%). Coupled with a sodium vanadium fluorophosphate (Na₃V₂(PO₄)₂F₃)@C cathode, this assembled full cell displays a specific capacity of 281 mA h g^-1 at 0.2 A g^-1 for 100 cycles. This work can be potentially used to improve other metal selenide-based anodes for rechargeable batteries.

General metal-organic framework-derived strategy to synthesize yolk-shell carbon-encapsulated nickelic spheres for sodium-ion batteries

Transition-metal compounds have attracted enormous attention as potential energy storage materials for their high theoretical capacity and energy density. However, the most present transition-metal compounds still suffer from severe capacity decay and limited rate capability due to the lack of robust architectures. Herein, a general metal-organic framework-derived route is reported to fabricate hierarchical carbon-encapsulated yolk-shell nickelic spheres as anode materials for sodium-ion batteries. The nickelic metal-organic framework (Ni-MOF) precursors can be in situ converted into hierarchical carbon-encapsulated Ni₂P (Ni₂P/C), NiS₂ (NiS₂/C) and NiSe₂ (NiSe₂/C) by phosphorization, sulfuration, and selenation reaction, respectively, and maintain their yolk-shell sphere-like morphology. The as-synthesized Ni₂P/C sample can deliver much lower polarization and discharge platform, smaller voltage gap, and faster kinetics in comparison with that of the other two counterparts, and thus achieve higher initial specific capacity (3222.1/1979.3 mAh g^-1) and reversible capacity of 765.4 mAh g^-1 after 110 cycles. This work should provide new insights into the phase and structure engineering of carbon-encapsulated transition-metal compound electrodes via MOFs template for advanced battery systems.