Advanced Li-Ion Batteries with High Rate,Stability, and Mass Loading Based on Graphene Ribbon Hybrid Networks

To optimize the cycle life and rate performance of lithium-ion batteries (LIBs), ultra-fine Fe₂O₃ nanowires with a diameter of approximately 2 nm uniformly anchored on a cross-linked graphene ribbon network are fabricated. The unique three-dimensional structure can effectively improve the electrical conductivity and facilitate ion diffusion, especially cross-plane diffusion. Moreover, Fe₂O₃ nanowires on graphene ribbons (Fe₂O₃/GR) are easily accessible for lithium ions compared with the traditional graphene sheets (Fe₂O₃/GS). In addition, the well-developed elastic network can not only undergo the drastic volume expansion during repetitive cycling, but also protect the bulk electrode from further pulverization. As a result, the Fe₂O₃/GR hybrid exhibits high rate and long cycle life Li storage performance (632 mAh g⁻¹ at 5 A g⁻¹, and 471 mAh g⁻¹ capacity maintained even after 3000 cycles). Especially at high mass loading (≈4 mg cm⁻²), the Fe₂O₃/GR can still deliver higher reversible capacity (223 mAh g⁻¹ even at 2 A g⁻¹) compared with the Fe₂O₃/GS (37 mAh g⁻¹) for LIBs.     

Pseudocapacitive Lithium Storage of Cauliflower-Like CoFe2O4 for Low-Temperature Battery Operation

Binary transition-metal oxides (BTMOs) with hierarchical micro–nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe₂O₄ (cl-CoFe₂O₄) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro–nano-structure can promote fast ion transport and stable electrode–electrolyte interfaces. As a result, the cl-CoFe₂O₄ can deliver a high specific capacity (1019.9 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate capability (626.0 mAh g⁻¹ at 5 A g⁻¹), and good cyclability (675.4 mAh g⁻¹ at 4 A g⁻¹ for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and −25 °C, the cl-CoFe₂O₄ anode can deliver high capacities of 907.5 and 664.5 mAh g⁻¹ at 100 mA g⁻¹, respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO₄ cathode exhibits a high rate performance (214.2 mAh g⁻¹ at 5000 mA g⁻¹) and an impressive cycling performance (612.7 mAh g⁻¹ over 140 cycles at 300 mA g⁻¹) in the voltage range of 0.5–3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe₂O₄ is dominated by pseudocapacitive behavior, leading to fast Li⁺ insertion/extraction and good cycling life.     

Carbonyl-rich Poly(pyrene-4,5,9,10-tetraone Sulfide) as Anode Materials for High-Performance Li and Na-Ion Batteries

Organic carbonyl electrode materials are widely employed for alkali metal-ion secondary batteries in terms of their sustainability, structure designability and abundant resources. As a typical redox-active organic electrode materials, pyrene-4, 5, 9, 10-tetraone (PT) shows high theoretical capacity due to the rich carbonyl active sites. But its electrochemical behavior in secondary batteries still needs further exploration. Herein, PT-based linear polymers (PPTS) is synthesized with thioether bond as bridging group and then employed as an anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As expected, PPTS shows improved conductivity and insolubility in the non-aqueous electrolyte. When used as an anode material for LIBs, PPTS delivers a high reversible specific capacity of 697.1 mAh g⁻¹ at 0.1 A g⁻¹ and good rate performance (335.4 mAh g⁻¹ at 1 A g⁻¹). Moreover, a reversible specific capacity of 205.2 mAh g⁻¹ at 0.05 A g⁻¹ could be obtained as an anode material for SIBs.     

Scalable Synthesis of One-Dimensional Mesoporous ZnMnO3 Nanorods with Ultra-Stable and High Rate Capability for Efficient Lithium Storage

The cost-efficient ZnMnO₃ has attracted increasing attention as a prospective anode candidate for advanced lithium-ion batteries (LIBs) owing to its resourceful abundance, large lithium storage capacity and low operating voltage. However, its practical application is still seriously limited by the modest cycling and rate performances. Herein, a facile design to scalable synthesize unique one-dimensional (1D) mesoporous ZnMnO₃ nanorods (ZMO-NRs) composed of nanoscale particles (≈11 nm) is reported. The 1D mesoporous structure and nanoscale building blocks of the ZMO-NRs effectively promote the transport of ions/electrons, accommodate severe volume changes, and expose more active sites for lithium storage. Benefiting from these appealing structural merits, the obtained ZMO-NRs anode exhibits excellent rate behavior (≈454 mAh g⁻¹ at 2 A g⁻¹) and ultra-long term cyclic performance (≈949.7 mAh g⁻¹ even over 500 cycles at 0.5 A g⁻¹) for efficient lithium storage. Additionally, the LiNi_0.8Co_0.1Mn_0.1O₂//ZMO-NRs full cell presents a practical energy density (≈192.2 Wh kg⁻¹) and impressive cyclability with approximately 91 % capacity retention over 110 cycles. This highlights that the ZMO-NRs product is a highly promising high-rate and stable electrode candidate towards advanced LIBs in electronic devices and sustainable energy storage applications.     

Two-Dimensional Germanium Sulfide Nanosheets as an Ultra-Stable and High Capacity Anode for Lithium Ion Batteries

Lithium ion batteries (LIBs) at present still suffer from low rate capability and poor cycle life during fast ion insertion/extraction processes. Searching for high-capacity and stable anode materials is still an ongoing challenge. Herein, a facile strategy for the synthesis of ultrathin GeS₂ nanosheets with the thickness of 1.1 nm is reported. When used as anodes for LIBs, the two-dimensional (2D) structure can effectively increase the electrode/electrolyte interface area, facilitate the ion transport, and buffer the volume expansion. Benefiting from these merits, the as-synthesized GeS₂ nanosheets deliver high specific capacity (1335 mAh g⁻¹ at 0.15 A g⁻¹), extraordinary rate performance (337 mAh g⁻¹ at 15 A g⁻¹) and stable cycling performance (974 mAh g⁻¹ after 200 cycles at 0.5 A g⁻¹). Importantly, our fabricated Li-ion full cells manifest an impressive specific capacity of 577 mAh g⁻¹ after 50 cycles at 0.1 A g⁻¹ and a high energy density of 361 Wh kg⁻¹ at a power density of 346 W kg⁻¹. Furthermore, the electrochemical reaction mechanism is investigated by the means of ex-situ high-resolution transmission electron microscopy. These results suggest that GeS₂ can use to be an alternative anode material and encourage more efforts to develop other high-performance LIBs anodes.     

Hierarchical Hollow-Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved-Performance Lithium-Ion Batteries

Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS₂/MoO₃ nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO₃/MoS₂ composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO₃/MoS₂ composites. According to Raman spectroscopy results, as-obtained defect-rich MoS₂ is confirmed to be a metallic 1T-phase MoS₂. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g⁻¹ and up to 1720.6 mAh g⁻¹ after 317 cycles under a current density of 0.2 A g⁻¹). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g⁻¹ at 2 A g⁻¹ after 700 cycles and 584.8 mAh g⁻¹ at 5 A g⁻¹ after 800 cycles). Moreover, at a rate of 1 A g⁻¹, the average specific capacity is maintained at 661 mAh g⁻¹. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.     

One-Step Calcination Synthesis of Bulk-Doped Surface-Modified Ni-Rich Cathodes with Superlattice for Long-Cycling Li-Ion Batteries

Nickel-rich (Ni≥90 %) layered cathodes are critical materials for achieving higher-energy-density and lower-cost next-generation Li-ion batteries (LIBs). However, their bulk and interface structural instabilities significantly impair their electrochemical performance, thus hindering their widespread adoption in commercial LIBs. Exploiting Ti and Mo diffusion chemistry, we report one-step calcination to synthesize bulk-to-surface modified LiNi_0.9Co_0.09Mo_0.01O₂ (NCMo90) featuring a 5 nm Li₂TiO₃ coating on the surface, a Mo-rich Li⁺/Ni²⁺ superlattice at the sub-surface, and Ti-doping in the bulk. Such a multi-functional structure effectively maintains its structural integrity upon cycling. As a result, such NCMo90 exhibits a high initial capacity of 221 mAh g⁻¹ at 0.1 C, excellent rate performance (184 mAh g⁻¹ at 5 C), and high capacity retention of 94.0 % after 500 cycles. This work opens a new avenue to developing industry-applicable Ni-rich cathodes for next-generation LIBs.     

Synthesis of Co3O4/Carbon Heteroaerogels with Ultrahigh Capacitance via Polyethyleneimine Intercalation of Co2BIM4 Nanosheets

The development of metal–organic frameworks (MOFs)-based supercapacitors have attracted intense concentration in recent years due to their regularly arranged porous and tunable pore sizes. However, the performance of the MOFs-derived supercapacitors is also low because of their poor electrical conductivity and rarely accessible active sites. In the present work, we developed a Co-MOF (namely Co₂BIM₄, BIM=benzimidazole) nanosheets derived Co₃O₄/nitrogen-doped carbon (Co₂BIM₄-Co₃O₄/NC) heteroaerogel as a novel supercapacitor electrode. The 3D Co₂BIM₄-Co₃O₄/NC heteroaerogels were obtained by directly intercalating polyethyleneimine (PEI) into the interlayers of Co₂BIM₄ nanosheets and following by carbonizing the resulting Co₂BIM₄/PEI composite. The Co₂BIM₄-Co₃O₄/NC electrode possessed 3D conductive framework with an overlapped hetero-interface and expanded interlayers, leading to fast and stable charge transfer/diffusion and an enhanced pseudocapacitance performance. Therefore, the Co₂BIM₄-Co₃O₄/NC electrode showed ultrahigh capacitance of 2568 F g⁻¹ at 1 A g⁻¹, 1747 F g⁻¹ at 10 A g⁻¹, and excellent long cycling time with a capacitance preservation of 92.7 % following 10000 cycles at 10 A g⁻¹, which is very promising for applications in supercapacitors and other energy storage devices.     

Enhanced Supercapacitor Performance Using a Co3O4@Co3S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co₃O₄ and Co₃S₄ on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co₃O₄@Co₃S₄ nanocomposite, the nanostructure of Co₃S₄ was fabricated from Co₃O₄ nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm⁻² (5651.24 F g⁻¹) at a current density of 6 mA cm⁻² compared to the Co₃O₄/rGO/NF electrode with a capacitance of 3.06 F cm⁻² (1230.77 F g⁻¹) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg⁻¹, specific power density of 6048.03 W kg⁻¹ and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s⁻¹). Finally, by using Co₃O₄ @Co₃S₄/rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm⁻² at the applied current density of 1 mA cm⁻², and delivered an energy density of 0.143 Wh kg⁻¹ at the power density of 5.42 W kg⁻¹.     

Self-Assembly of Polyoxometalate-Resorcin[4]arene-Based Inorganic-Organic Complexes: Metal Ion Effects on the Electrochemical Performance of Lithium Ion Batteries

With their adjustable structures and diverse functions, polyoxometalate (POM)-resorcin[4]arene-based inorganic–organic complexes are a kind of potential multifunctional material. They have potential applications for lithium ion batteries (LIBs). However, the relationship between different coordinated metal ions and electrochemical performance has rarely been investigated. Here, three functionalized POM-resorcin[4]arene-based inorganic–organic materials, [Co₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 2 EtOH ⋅ 4.5 H₂O ( 1 ), [Ni₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 4 EtOH ⋅ 13 H₂O ( 2 ), and [Zn₂(TMR4 A)₂(H₂O)₁₀][SiW₁₂O₄₀] ⋅ 2 EtOH ⋅ 2 H₂O ( 3 ), have been synthesized. Furthermore, to enhance the conductivities of these compounds, 1–3 were doped with reduced graphene oxide (RGO) to give composites 1 @RGO- 3 @RGO, respectively. As anode materials for LIBs, 1 @RGO- 3 @RGO can deliver very high discharge capacities (1445.9, 1285.0 and 1095.3 mAh g⁻¹, respectively) in the initial run, and show discharge capacities of 898, 665 and 651 mAh g⁻¹, respectively, at a current density of 0.1 A g⁻¹ over 100 runs. More importantly, the discharge capacities of 319, 283 and 329 mAh g⁻¹ were maintained for 1 @RGO- 3 @RGO even after 400 cycles at large current density (1 A g⁻¹).     

Hermetically Coated and Well‐Separated Co3O4 Nanophase within Porous Graphitic Carbon Nanosheets: Synthesis,Confinement Effect,and Improved Lithium‐Storage Capacity and Durability

Considerable lithium‐driven volume changes and loss of crystallinity on cycling have impeded the sustainable use of transition metal oxides (MOs) as attractive anode materials for advanced lithium‐ion batteries that have almost six times the capacity of carbon per unit volume. Herein, Co₃O₄ was used as a model MO in a facile process involving two pyrolysis steps for in situ encapsulation of nanosized MO in porous two‐dimensional graphitic carbon nanosheets (2D‐GCNs) with high surface areas and abundant active sites to overcome the above‐mentioned problems. The proposed method is inexpensive, industrially scalable, and easy to operate with a high yield. TEM revealed that the encaged Co₃O₄ is well separated and uniformly dispersed with surrounding onionlike graphitic layers. By taking advantage of the high electronic conductivity and confinement effect of the surrounding 2D‐GCNs, a hierarchical GCNs‐coated Co₃O₄ (Co₃O₄@GCNs) anode with 43.5 wt % entrapped active nanoparticles delivered a remarkable initial specific capacity of 1816 mAh g^?1 at a current density of 100 mA g^?1. After 50 cycles, the retained capacity is as high as 987 mAh g^?1. When the current density was increased to 1000 mA g^?1, the anode showed a capacity retention of 416 mAh g^?1. Enhanced reversible rate capability and prolonged cycling stability were found for Co₃O₄@GCN compared to pure GCNs and Co₃O₄. The Co₃O₄@GCNs hybrid holds promise as an efficient candidate material for anodes due to its low cost, environmentally friendly nature, high capacity, and stability.     

Biomimetic Straw-Like Bundle Cobalt-Doped Fe2O3 Electrodes towards Superior Lithium-Ion Storage

Biomimetic straw-like bundles of Co-doped Fe₂O₃ (SCF), with Co²⁺ incorporated into the lattice of α-Fe₂O₃, was fabricated through a cost-effective hydrothermal process and used as the anode material for lithium-ion batteries (LIBs). The SCF exhibited ultrahigh initial discharge specific capacity (1760.7 mA h⁻¹ g⁻¹ at 200 mA g⁻¹) and cycling stability (with the capacity retention of 1268.3 mA h⁻¹ g⁻¹ after 350 cycles at 200 mA g⁻¹). In addition, a superior rate capacity of 376.1 mA h⁻¹ g⁻¹ was obtained at a high current density of 4000 mA g⁻¹. The remarkable electrochemical lithium storage of SCF is attributed to the Co-doping, which increases the unit cell volume and affects the whole structure. It makes the Li⁺ insertion–extraction process more flexible. Meanwhile, the distinctive straw-like bundle structure can accelerate Li ion diffusion and alleviate the huge volume expansion upon cycling.     

Perovskite SrCo0.9Nb0.1O3−δ as an Anion‐Intercalated Electrode Material for Supercapacitors with Ultrahigh Volumetric Energy Density

We have synthesized and characterized perovskite‐type SrCo_0.9Nb_0.1O_3−δ (SCN) as a novel anion‐intercalated electrode material for supercapacitors in an aqueous KOH electrolyte, demonstrating a very high volumetric capacitance of about 2034.6 F cm⁻³ (and gravimetric capacitance of ca. 773.6 F g⁻¹) at a current density of 0.5 A g⁻¹ while maintaining excellent cycling stability with a capacity retention of 95.7 % after 3000 cycles. When coupled with an activated carbon (AC) electrode, the SCN/AC asymmetric supercapacitor delivered a specific energy density as high as 37.6 Wh kg⁻¹ with robust long‐term stability.     

Catalytically Active CoSe2 Supported on Nitrogen-Doped Three Dimensional Porous Carbon as a Cathode for Highly Stable Lithium-Sulfur Battery

Lithium-sulfur batteries are promising secondary energy storage devices that are mainly limited by its unsatisfactory cyclability owing to inefficient reversible conversion of sulfur and lithium sulfide on the cathode during the discharge/charging process. In this study, nitrogen-doped three-dimensional porous carbon material loaded with CoSe₂ nanoparticles (CoSe₂-PNC) is developed as a cathode for lithium-sulfur battery. A combination of CoSe₂ and nitrogen-doped porous carbon can efficiently improve the cathode activity and its conductivity, resulting in enhanced redox kinetics of the charge/discharge process. The obtained electrode exhibits a high discharge specific capacity of 1139.6 mAh g⁻¹ at a current density of 0.2 C. After 100 cycles, its capacity remained at 865.7 mAh g⁻¹ thus corresponding to a capacity retention of 75.97 %. In a long-term cycling test, discharge specific capacity of 546.7 mAh g⁻¹ was observed after 300 cycles performed at a current density of 1 C.     

Hybrid Sub-1 nm Nanosheets of Co-assembled MnZnCuOx and Polyoxometalate Clusters as Anodes for Li-ion Batteries

Transition metal oxide (TMO) anode materials in lithium-ion batteries (LIBs) usually suffer from serious volume expansion leading to the pulverization of structures, further giving rise to lower specific capacity and worse cycling stability. Herein, by introducing polyoxometalate (POM) clusters into TMOs and precisely controlling the amount of POMs, the MnZnCuO_x-phosphomolybdic acid hybrid sub-1 nm nanosheets (MZC-PMA HSNSs) anode is successfully fabricated, where the special electron rich structure of POMs is conducive to accelerating the migration of lithium ions on the anode to obtain higher specific capacity, and the non-covalent interactions between POMs and TMOs make the HSNSs possess excellent structural and chemical stability, thus exhibiting outstanding electrochemical performance in LIBs, achieving a high reversible capacity (1157 mAh g⁻¹ at 100 mA g⁻¹) and an admirable long-term cycling stability at low and high current densities.     

Bimetal‐organic Framework‐derived Co9S8/ZnS@NC Heterostructures for Superior Lithium‐ion Storage

Heterostructure engineering of electrode materials, which is expected to accelerate the ion/electron transport rates driven by a built‐in internal electric field at the heterointerface, offers unprecedented promise in improving their cycling stability and rate performance. Herein, carbon nanotubes with Co₉S₈/ZnS heterostructures embedded in a N‐doped carbon framework (Co₉S₈/ZnS@NC) have been rationally designed via an in‐situ vapor chemical transformation strategy with the aid of thiophene, which not only acted as carbon source for the growth of carbon nanotubes but also as sulfur source for the sulfurization of metal Zn and Co. Density functional theory (DFT) calculation shows an about 3.24 eV electrostatic potential difference between ZnS and Co₉S₈, which results in a strong electrostatic field across the interface that makes electrons transfer from Co₉S₈ to the ZnS side. As expected, a stable cycling performance with reversible capacity of 411.2 mAh g^?1 at 1000 mA g^?1 after 300 cycles, excellent rate capability (324 mAh g^?1 at 2000 A g^?1) and a high percentage of pseudocapacitance contribution (87.5% at 2.2 mv/s) for lithium‐ion batteries (LIBs) are achieved. This work provides a possible strategy for designing multicomponent heterostructural materials for application in energy storage and conversion fields.     

金属有机框架衍生的高性能锂离子电池负极Co3O4/C复合材料

为克服Co_3O_4负极材料导电率低、循环稳定性差的缺点,选择Co_2(NDC)_2DMF_2(NDC=1,4-萘二甲酸根)为前驱体采用两步煅烧工艺,制备了具有高碳含量的Co_3O_4/C复合材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和拉曼光谱对样品进行了表征。采用热重分析法(TGA)测定了Co_3O_4/C中非晶态碳的含量。作为锂离子电池的负极材料,Co_3O_4/C具有高的可逆比容量、优异的循环性能(在200 m A·g~(-1)的电流密度下,循环200圈后放电比容量稳定保持在1 000 mAh·g~(-1))和良好的倍率性能(在100、200、500、1 000和2 000 mA·g~(-1)的电流密度下,放电比容量为分别1 076.3、976.2、872.9、783.6和670.1 mAh·g~(-1))。材料优异的电化学性能归结为有机配体衍生的高含量非晶态碳的导电和缓冲作用有利于电子的快速传递并有效减缓了金属氧化物充放电过程中的体积膨胀。     

Formation of NiCo2V2O8 Yolk–Double Shell Spheres with Enhanced Lithium Storage Properties

Complex nanostructures with multi‐components and intricate architectures hold great potential in developing high‐performance electrode materials for lithium‐ion batteries (LIBs). Herein, we demonstrate a facile self‐templating strategy for the synthesis of metal vanadate nanomaterials with complex chemical composition of NiCo₂V₂O₈ and a unique yolk–double shell structure. Starting with the Ni‐Co glycerate spheres, NiCo₂V₂O₈ yolk–double shell spheres are synthesized through an anion‐exchange reaction of Ni‐Co glycerate templates with VO₃⁻ ions, followed by an annealing treatment. By virtue of compositional and structural advantages, these NiCo₂V₂O₈ yolk–double shell spheres manifest outstanding lithium storage properties when evaluated as anodes for LIBs. Impressively, an extra‐high reversible capacity of 1228 mAh g⁻¹ can be retained after 500 cycles at a high current density of 1.0 Ag⁻¹.     

Mixed Cu2Se Hexagonal Nanosheets@Co3Se4 Nanospheres for High-Performance Asymmetric Supercapacitors

Rational designing and constructing multiphase hybrid electrode materials is an effective method to compensate for the performance defects of the single component. Based on this strategy, Cu₂Se hexagonal nanosheets@Co₃Se₄ nanospheres mixed structures have been fabricated by a facile two-step hydrothermal method. Under the synergistic effect of the high ionic conductivity of Cu₂Se and the remarkable cycling stability of Co₃Se₄, Cu₂Se@Co₃Se₄ can exhibit outstanding electrochemical performance as a novel electrode material. The as-prepared Cu₂Se@Co₃Se₄ electrode displays high specific capacitance of 1005 F g⁻¹ at 1 A g⁻¹ with enhanced rate capability (56 % capacitance retention at 10 A g⁻¹), and ultralong lifespan (94.2 % after 10 000 cycles at 20 A g⁻¹). An asymmetric supercapacitor is assembled applying the Cu₂Se@Co₃Se₄ as anode and graphene as cathode, which delivers a wide work potential window of 1.6 V, high energy density (30.9 Wh kg⁻¹ at 0.74 kW kg⁻¹), high power density (21.0 Wh kg⁻¹ at 7.50 kW kg⁻¹), and excellent cycling stability (85.8 % after 10 000 cycles at 10 A g⁻¹).     

Porous ZnO/Co3O4/N‐doped carbon nanocages synthesized via pyrolysis of complex metal–organic framework (MOF) hybrids as an advanced lithium‐ion battery anode

Metal oxides have a large storage capacity when employed as anode materials for lithium‐ion batteries (LIBs). However, they often suffer from poor capacity retention due to their low electrical conductivity and huge volume variation during the charge–discharge process. To overcome these limitations, fabrication of metal oxides/carbon hybrids with hollow structures can be expected to further improve their electrochemical properties. Herein, ZnO‐Co₃O₄ nanocomposites embedded in N‐doped carbon (ZnO‐Co₃O₄@N‐C) nanocages with hollow dodecahedral shapes have been prepared successfully by the simple carbonizing and oxidizing of metal–organic frameworks (MOFs). Benefiting from the advantages of the structural features, i.e. the conductive N‐doped carbon coating, the porous structure of the nanocages and the synergistic effects of different components, the as‐prepared ZnO‐Co₃O₄@N‐C not only avoids particle aggregation and nanostructure cracking but also facilitates the transport of ions and electrons. As a result, the resultant ZnO‐Co₃O₄@N‐C shows a discharge capacity of 2373 mAh g^?1 at the first cycle and exhibits a retention capacity of 1305 mAh g^?1 even after 300 cycles at 0.1 A g^?1. In addition, a reversible capacity of 948 mAh g^?1 is obtained at a current density of 2 A g^?1, which delivers an excellent high‐rate cycle ability.