Mesoporous and Nanostructured TiO2 layer with Ultra‐High Loading on Nitrogen‐Doped Carbon Foams as Flexible and Free‐Standing Electrodes for Lithium‐Ion Batteries

A simple and green method is developed for the preparation of nanostructured TiO₂ supported on nitrogen‐doped carbon foams (NCFs) as a free‐standing and flexible electrode for lithium‐ion batteries (LIBs), in which the TiO₂ with 2.5–4 times higher loading than the conventional TiO₂‐based flexible electrodes acts as the active material. In addition, the NCFs act as a flexible substrate and efficient conductive networks. The nanocrystalline TiO₂ with a uniform size of ≈10 nm form a mesoporous layer covering the wall of the carbon foam. When used directly as a flexible electrode in a LIB, a capacity of 188 mA h g^?1 is achieved at a current density of 200 mA g^?1 for a potential window of 1.0–3.0 V, and a specific capacity of 149 mA h g^?1 after 100 cycles at a current density of 1000 mA g^?1 is maintained. The highly conductive NCF and flexible network, the mesoporous structure and nanocrystalline size of the TiO₂ phase, the firm adhesion of TiO₂ over the wall of the NCFs, the small volume change in the TiO₂ during the charge/discharge processes, and the high cut‐off potential contribute to the excellent capacity, rate capability, and cycling stability of the TiO₂/NCFs flexible electrode.     

In Situ Encapsulating α‐MnS into N,S‐Codoped Nanotube‐Like Carbon as Advanced Anode Material: α → β Phase Transition Promoted Cycling Stability and Superior Li/Na‐Storage Performance in Half/Full Cells

Incorporation of N,S‐codoped nanotube‐like carbon (N,S‐NTC) can endow electrode materials with superior electrochemical properties owing to the unique nanoarchitecture and improved kinetics. Herein, α‐MnS nanoparticles (NPs) are in situ encapsulated into N,S‐NTC, preparing an advanced anode material (α‐MnS@N,S‐NTC) for lithium‐ion/sodium‐ion batteries (LIBs/SIBs). It is for the first time revealed that electrochemical α → β phase transition of MnS NPs during the 1st cycle effectively promotes Li‐storage properties, which is deduced by the studies of ex situ X‐ray diffraction/high‐resolution transmission electron microscopy and electrode kinetics. As a result, the optimized α‐MnS@N,S‐NTC electrode delivers a high Li‐storage capacity (1415 mA h g^?1 at 50 mA g^?1), excellent rate capability (430 mA h g^?1 at 10 A g^?1), and long‐term cycling stability (no obvious capacity decay over 5000 cycles at 1 A g^?1) with retained morphology. In addition, the N,S‐NTC‐based encapsulation plays the key roles on enhancing the electrochemical properties due to its high conductivity and unique 1D nanoarchitecture with excellent protective effects to active MnS NPs. Furthermore, α‐MnS@N,S‐NTC also delivers high Na‐storage capacity (536 mA h g^?1 at 50 mA g^?1) without the occurrence of such α → β phase transition and excellent full‐cell performances as coupling with commercial LiFePO₄ and LiNi_0.6Co_0.2Mn_0.2O₂ cathodes in LIBs as well as Na₃V₂(PO₄)₂O₂F cathode in SIBs.     

Graphene Aerogels with Anchored Sub‐Micrometer Mulberry‐Like ZnO Particles for High‐Rate and Long‐Cycle Anode Materials in Lithium Ion Batteries

Graphene aerogels (GAs) anchoring hierarchical, mulberry‐like ZnO particles are fabricated in situ using a one‐step solvothermal reaction. The resulting composites can function as anodes in lithium ion batteries, where they exhibit a high capacity and cyclic stability. The reversible capacities obtained are 365, 320, and 230 mA h g^?1 at current densities of 1, 2, and 10 A g^?1. Their high reversible capacity is 445 mA h g^?1 at a current density of 1.6 A g^?1; this value is maintained even after the 500th cycle, The excellent electrochemical performance is attributed to strong oxygen bridges between ZnO and graphene, where C–O–Zn linkages provide a good pathway for electron transport during charge/discharge cycles. Additionally, the hierarchical structure of the ZnO microballs suppresses stacking among the graphene layers, allowing the GAs to accelerate the transport of lithium ions. Furthermore, the GA framework enhances the electrical conductivity and buffer any volume expansion.     

Hierarchically Porous Fe2CoSe4 Binary‐Metal Selenide for Extraordinary Rate Performance and Durable Anode of Sodium‐Ion Batteries

Owing to high energy capacities, transition metal chalcogenides have drawn significant research attention as the promising electrode materials for sodium‐ion batteries (SIBs). However, limited cycle life and inferior rate capabilities still hinder their practical application. Improvement of the intrinsic conductivity by smart choice of elemental combination along with carbon coupling of the nanostructures may result in excellence of rate capability and prolonged cycling stability. Herein, a hierarchically porous binary transition metal selenide (Fe₂CoSe₄, termed as FCSe) nanomaterial with improved intrinsic conductivity was prepared through an exclusive methodology. The hierarchically porous structure, intimate nanoparticle–carbon matrix contact, and better intrinsic conductivity result in extraordinary electrochemical performance through their synergistic effect. The synthesized FCSe exhibits excellent rate capability (816.3 mA h g^?1 at 0.5 A g^?1 and 400.2 mA h g^?1 at 32 A g^?1), extended cycle life (350 mA h g^?1 even after 5000 cycles at 4 A g^?1), and adequately high energy capacity (614.5 mA h g^?1 at 1 A g^?1 after 100 cycles) as anode material for SIBs. When further combined with lab‐made Na₃V₂(PO₄)₃/C cathode in Na‐ion full cells, FCSe presents reasonably high and stable specific capacity.     

Mesoporous NiS2 Nanospheres Anode with Pseudocapacitance for High‐Rate and Long‐Life Sodium‐Ion Battery

It is of great importance to exploit electrode materials for sodium‐ion batteries (SIBs) with low cost, long life, and high‐rate capability. However, achieving quick charge and high power density is still a major challenge for most SIBs electrodes because of the sluggish sodiation kinetics. Herein, uniform and mesoporous NiS₂ nanospheres are synthesized via a facile one‐step polyvinylpyrrolidone assisted method. By controlling the voltage window, the mesoporous NiS₂ nanospheres present excellent electrochemical performance in SIBs. It delivers a high reversible specific capacity of 692 mA h g^?1. The NiS₂ anode also exhibits excellent high‐rate capability (253 mA h g^?1 at 5 A g^?1) and long‐term cycling performance (319 mA h g^?1 capacity remained even after 1000 cycles at 0.5 A g^?1). A dominant pseudocapacitance contribution is identified and verified by kinetics analysis. In addition, the amorphization and conversion reactions during the electrochemical process of the mesoporous NiS₂ nanospheres is also investigated by in situ X‐ray diffraction. The impressive electrochemical performance reveals that the NiS₂ offers great potential toward the development of next generation large scale energy storage.     

Ultrathin Nitrogen‐Doped Carbon Layer Uniformly Supported on Graphene Frameworks as Ultrahigh‐Capacity Anode for Lithium‐Ion Full Battery

The designable structure with 3D structure, ultrathin 2D nanosheets, and heteroatom doping are considered as highly promising routes to improve the electrochemical performance of carbon materials as anodes for lithium‐ion batteries. However, it remains a significant challenge to efficiently integrate 3D interconnected porous frameworks with 2D tunable heteroatom‐doped ultrathin carbon layers to further boost the performance. Herein, a novel nanostructure consisting of a uniform ultrathin N‐doped carbon layer in situ coated on a 3D graphene framework (NC@GF) through solvothermal self‐assembly/polymerization and pyrolysis is reported. The NC@GF with the nanosheets thickness of 4.0 nm and N content of 4.13 at% exhibits an ultrahigh reversible capacity of 2018 mA h g^?1 at 0.5 A g^?1 and an ultrafast charge–discharge feature with a remarkable capacity of 340 mA h g^?1 at an ultrahigh current density of 40 A g^?1 and a superlong cycle life with a capacity retention of 93% after 10 000 cycles at 40 A g^?1. More importantly, when coupled with LiFePO₄ cathode, the fabricated lithium‐ion full cells also exhibit high capacity and excellent rate and cycling performances, highlighting the practicability of this NC@GF.     

MOF‐Derived CuS@Cu‐BTC Composites as High‐Performance Anodes for Lithium‐Ion Batteries

The CuS(x wt%)@Cu‐BTC (BTC = 1,3,5‐benzenetricarboxylate; x = 3, 10, 33, 58, 70, 99.9) materials are synthesized by a facile sulfidation reaction. The composites are composed of octahedral Cu₃(BTC)₂·(H₂O)₃ (Cu‐BTC) with a large specific surface area and CuS with a high conductivity. The as‐prepared CuS@Cu‐BTC products are first applied as the anodes of lithium‐ion batteries (LIBs). The synergistic effect between Cu‐BTC and CuS components can not only accommodate the volume change and stress relaxation of electrodes but also facilitate the fast transport of Li ions. Thus, it can greatly suppress the transformation process from Li₂S to polysulfides by improving the reversibility of the conversion reaction. Benefiting from the unique structural features, the optimal CuS(70 wt%)@Cu‐BTC sample exhibits a remarkably improved electrochemical performance, showing an over‐theoretical capacity up to 1609 mAh g^?1 after 200 cycles (100 mA g^?1) with an excellent rate‐capability of ≈490 mAh g^?1 at 1000 mA g^?1. The outstanding LIB properties indicate that the CuS(70 wt%)@Cu‐BTC sample is a highly desirable electrode material candidate for high‐performance LIBs.     

Hierarchically Nanoporous 3D Assembly Composed of Functionalized Onion‐Like Graphitic Carbon Nanospheres for Anode‐Minimized Li Metal Batteries

Despite the recent attention for Li metal anode (LMA) with high theoretical specific capacity of ≈ 3860 mA h g^?1, it suffers from not enough practical energy densities and safety concerns originating from the excessive metal load, which is essential to compensate for the loss of Li sources resulting from their poor coulombic efficiencies (CEs). Therefore, the development of high‐performance LMA is needed to realize anode‐minimized Li metal batteries (LMBs). In this study, high‐performance LMAs are produced by introducing a hierarchically nanoporous assembly (HNA) composed of functionalized onion‐like graphitic carbon building blocks, several nanometers in diameter, as a catalytic scaffold for Li‐metal storage. The HNA‐based electrodes lead to a high Li ion concentration in the nanoporous structure, showing a high CE of ≈ 99.1%, high rate capability of 12 mA cm^?2, and a stable cycling behavior of more than 750 cycles. In addition, anode‐minimized LMBs are achieved using a HNA that has limited Li content ( ≈ 0.13 mg cm^?2), corresponding to 6.5% of the cathode material (commercial NCM622 ( ≈ 2 mg cm^?2)). The LMBs demonstrate a feasible electrochemical performance with high energy and power densities of ≈ 510 Wh kg_electrode^?1 and ≈ 2760 W kg_electrode^?1, respectively, for more than 100 cycles.     

Synthesis of MoS2@C Nanotubes Via the Kirkendall Effect with Enhanced Electrochemical Performance for Lithium Ion and Sodium Ion Batteries

A MoS₂@C nanotube composite is prepared through a facile hydrothermal method, in which the MoS₂ nanotube and amorphous carbon are generated synchronically. When evaluated as an anode material for lithium ion batteries (LIB), the MoS₂@C nanotube manifests an enhanced capacity of 1327 mA h g^?1 at 0.1 C with high initial Coulombic efficiency (ICE) of 92% and with capacity retention of 1058.4 mA h g^?1 (90% initial capacity retention) after 300 cycles at a rate of 0.5 C. A superior rate capacity of 850 mA h g^?1 at 5 C is also obtained. As for sodium ion batteries, a specific capacity of 480 mA h g^?1 at 0.5 C is achieved after 200 cycles. The synchronically formed carbon and stable hollow structure lead to the long cycle stability, high ICE, and superior rate capability. The good electrochemical behavior of MoS₂@C nanotube composite suggests its potential application in high‐energy LIB.     

Bimetal‐Organic‐Framework Derivation of Ball‐Cactus‐Like Ni‐Sn‐P@C‐CNT as Long‐Cycle Anode for Lithium Ion Battery

Metal phosphides are a new class of potential high‐capacity anodes for lithium ion batteries, but their short cycle life is the critical problem to hinder its practical application. A unique ball‐cactus‐like microsphere of carbon coated NiP₂/Ni₃Sn₄ with deep‐rooted carbon nanotubes (Ni‐Sn‐P@C‐CNT) is demonstrated in this work to solve this problem. Bimetal‐organic‐frameworks (BMOFs, Ni‐Sn‐BTC, BTC refers to 1,3,5‐benzenetricarboxylic acid) are formed by a two‐step uniform microwave‐assisted irradiation approach and used as the precursor to grow Ni‐Sn@C‐CNT, Ni‐Sn‐P@C‐CNT, yolk–shell Ni‐Sn@C, and Ni‐Sn‐P@C. The uniform carbon overlayer is formed by the decomposition of organic ligands from MOFs and small CNTs are deeply rooted in Ni‐Sn‐P@C microsphere due to the in situ catalysis effect of Ni‐Sn. Among these potential anode materials, the Ni‐Sn‐P@C‐CNT is found to be a promising anode with best electrochemical properties. It exhibits a large reversible capacity of 704 mA h g^?1 after 200 cycles at 100 mA g^?1 and excellent high‐rate cycling performance (a stable capacity of 504 mA h g^?1 retained after 800 cycles at 1 A g^?1). These good electrochemical properties are mainly ascribed to the unique 3D mesoporous structure design along with dual active components showing synergistic electrochemical activity within different voltage windows.     

Solvent‐Free Synthesis of Uniform MOF Shell‐Derived Carbon Confined SnO2/Co Nanocubes for Highly Reversible Lithium Storage

Tin dioxide (SnO₂) has attracted much attention in lithium‐ion batteries (LIBs) due to its abundant source, low cost, and high theoretical capacity. However, the large volume variation, irreversible conversion reaction limit its further practical application in next‐generation LIBs. Here, a novel solvent‐free approach to construct uniform metal–organic framework (MOF) shell‐derived carbon confined SnO₂/Co (SnO₂/Co@C) nanocubes via a two‐step heat treatment is developed. In particular, MOF‐coated CoSnO₃ hollow nanocubes are for the first time synthesized as the intermediate product by an extremely simple thermal solid‐phase reaction, which is further developed as a general strategy to successfully obtain other uniform MOF‐coated metal oxides. The as‐synthesized SnO₂/Co@C nanocubes, when tested as LIB anodes, exhibit a highly reversible discharge capacity of 800 mAh g^?1 after 100 cycles at 200 mA g^?1 and excellent cycling stability with a retained capacity of 400 mAh g^?1 after 1800 cycles at 5 A g^?1. The experimental analyses demonstrate that these excellent performances are mainly ascribed to the delicate structure and a synergistic effect between Co and SnO₂. This facile synthetic approach will greatly contribute to the development of functional metal oxide‐based and MOF‐assisted nanostructures in many frontier applications.     

In Situ Fabrication of Branched TiO2/C Nanofibers as Binder‐Free and Free‐Standing Anodes for High‐Performance Sodium‐Ion Batteries

Herein, 1D free‐standing and binder‐free hierarchically branched TiO₂/C nanofibers (denoted as BT/C NFs) based on an in situ fabrication method as an anode for sodium‐ion batteries are reported. The in situ fabrication endows this material with large surface area and strong structural stability, providing this material with abundant active sites and smooth channels for fast ion transportation. As a result, BT/C NFs with the character of free‐standing membranes are directly used as binder‐free anode for sodium‐ion batteries, delivering a capacity of 284 mA h g^?1 at a current density of 200 mA g^?1 after 1000 cycles. Even at a high current density of 2000 mA g^?1, the reversible capacity can still achieve as high as 204 mA h g^?1. By means of kinetic analysis, it is demonstrated that the remarkable surface pseudocapacitive behavior is also a major factor to achieve excellent performance. The rationally designed structure coupled with the inherent pseudocapacitive behavior gives this material potential for sodium‐ion batteries.     

Novel 2D Layered Molybdenum Ditelluride Encapsulated in Few‐Layer Graphene as High‐Performance Anode for Lithium‐Ion Batteries

Molybdenum ditelluride nanosheets encapsulated in few‐layer graphene (MoTe₂/FLG) are synthesized by a simple heating method using Te and Mo powder and subsequent ball milling with graphite. The as‐prepared MoTe₂/FLG nanocomposites as anode materials for lithium‐ion batteries exhibit excellent electrochemical performance with a highly reversible capacity of 596.5 mAh g^?1 at 100 mA g^?1, a high rate capability (334.5 mAh g^?1 at 2 A g^?1), and superior cycling stability (capacity retention of 99.5% over 400 cycles at 0.5 A g^?1). Ex situ X‐ray diffraction and transmission electron microscopy are used to explore the lithium storage mechanism of MoTe₂. Moreover, the electrochemical performance of a MoTe₂/FLG//0.35Li₂MnO₃·0.65LiMn_0.5Ni_0.5O₂ full cell is investigated, which displays a reversible capacity of 499 mAh g^?1 (based on the MoTe₂/FLG mass) at 100 mA g^?1 and a capacity retention of 78% over 50 cycles, suggesting the promising application of MoTe₂/FLG for lithium‐ion storage. First‐principles calculations exhibit that the lowest diffusion barrier (0.18 eV) for lithium ions along pathway III in the MoTe₂ layered structure is beneficial for improving the Li intercalation/deintercalation property.     

Hierarchical Composite of Rose‐Like VS2@S/N‐Doped Carbon with Expanded (001) Planes for Superior Li‐Ion Storage

In the present work, a hierarchical composite of rose‐like VS₂@S/N‐doped carbon (VS₂@SNC) with expanded (001) planes is successfully fabricated through a facile synthetic route. Notably, the d‐spacing of (001) planes is expanded to 0.92 nm, which is proved to dramatically reduce the energy barrier for Li⁺ diffusion in the composite of VS₂@SNC by density functional theory calculation. On the other hand, the S/N‐doped carbon in the composite greatly promotes the electrical conductivity and enhances the structural stability. In addition, the hierarchical structure of VS₂@SNC facilitates rapid electrolyte diffusion and increases the contact area between the electrode and electrolyte simultaneously. Benefiting from the merits mentioned above, the VS₂@SNC electrode exhibits excellent electrochemical properties, such as a large reversible capacity of 971.6 mA h g^?1 at 0.2 A g^?1, an extremely high rate capability of 772.1 mA h g^?1 at 10 A g^?1, and a remarkable cycling stability up to 600 cycles at 8 A g^?1 with a capacity of 684.5 mA h g^?1, making it a promising candidate as an anode material for lithium‐ion batteries.     

Flexible and Binder‐Free Electrodes of Sb/rGO and Na3V2(PO4)3/rGO Nanocomposites for Sodium‐Ion Batteries

Flexible power sources have shown great promise in next‐generation bendable, implantable, and wearable electronic systems. Here, flexible and binder‐free electrodes of Na₃V₂(PO₄)₃/reduced graphene oxide (NVP/rGO) and Sb/rGO nanocomposites for sodium‐ion batteries are reported. The Sb/rGO and NVP/rGO paper electrodes with high flexibility and tailorability can be easily fabricated. Sb and NVP nanoparticles are embedded homogenously in the interconnected framework of rGO nanosheets, which provides structurally stable hosts for Na‐ion intercalation and deintercalation. The NVP/rGO paper‐like cathode delivers a reversible capacity of 113 mAh g^?1 at 100 mA g^?1 and high capacity retention of ≈96.6% after 120 cycles. The Sb/rGO paper‐like anode gives a highly reversible capacity of 612 mAh g^?1 at 100 mA g^?1, an excellent rate capacity up to 30 C, and a good cycle performance. Moreover, the sodium‐ion full cell of NVP/rGO//Sb/rGO has been fabricated, delivering a highly reversible capacity of ≈400 mAh g^?1 at a current density of 100 mA g^?1 after 100 charge/discharge cycles. This work may provide promising electrode candidates for developing next‐generation energy‐storage devices with high capacity and long cycle life.     

A Novel High‐Capacity Anode Material Derived from Aromatic Imides for Lithium‐Ion Batteries

A novel anode material for lithium‐ion batteries derived from aromatic imides with multicarbonyl group conjugated with aromatic core structure is reported, benzophenolne‐3,3′,4,4′‐tetracarboxylimide oligomer (BTO). It could deliver a reversible capacity of 829 mA h g^?1 at 42 mA g^?1 for 50 cycles with a stable discharge plateaus ranging from 0.05–0.19 V versus Li⁺/Li. At higher rates of 420 and 840 mA g^?1, it can still exhibit excellent cycling stability with a capacity retention of 88% and 72% after 1000 cycles, delivering capacity of 559 and 224 mA h g^?1. In addition, a rational prediction of the maximum amount of lithium intercalation is proposed and explored its possible lithium storage mechanism.     

Facile Synthesis of Ultrasmall CoS2 Nanoparticles within Thin N‐Doped Porous Carbon Shell for High Performance Lithium‐Ion Batteries

Cobalt sulfide (CoS₂) is considered one of the most promising alternative anode materials for high‐performance lithium‐ion batteries (LIBs) by virtue of its remarkable electrical conductivity, high theoretical capacity, and low cost. However, it suffers from a poor cycling stability and low rate capability because of its volume expansion and dissolution of the polysulfide intermediates in the organic electrolytes during the battery charge/discharge process. In this study, a novel porous carbon/CoS₂ composite is prepared by using nano metal–organic framework (MOF) templates for high‐preformance LIBs. The as‐made ultrasmall CoS₂ (15 nm) nanoparticles in N‐rich carbon exhibit promising lithium storage properties with negligible loss of capacity at high charge/discharge rate. At a current density of 100 mA g^?1, a capacity of 560 mA h g^?1 is maintained after 50 cycles. Even at a current density as high as 2500 mA g^?1, a reversible capacity of 410 mA h g^?1 is obtained. The excellent and highly stable battery performance should be attributed to the synergism of the ultrasmall CoS₂ particles and the thin N‐rich porous carbon shells derieved from nanosized MOF precusors.     

Collaborative Design of Hollow Nanocubes,In Situ Cross‐Linked Binder,and Amorphous Void@SiOx@C as a Three‐Pronged Strategy for Ultrastable Lithium Storage

Although silicon‐based materials are ideal candidate anodes for high energy density lithium‐ion batteries, the large volumetric expansion seriously damages the integrity of the electrodes and impedes commercial processes. Reasonable electrode design based on adjustable structures of silicon and strong binders prepared by a facile method is still a great challenge. Herein, a three‐pronged collaborative strategy via hollow nanocubes, amorphous Void@SiO_x@C, and in situ cross‐linked polyacrylic acid and d ‐sorbitol 3D network binder (c‐PAA‐DS) is adopted to maintain structural/electrode integrality and stability. The all‐integrated c‐PAA‐DS/Void@SiO_x@C electrode delivers excellent mechanical property, which is attributed to ductility of the c‐PAA‐DS binder and high adhesion energy between Void@SiO_x@C and c‐PAA‐DS calculated by density functional theory. Benefiting from the synergistic effect of accommodation of the hollow structure, protection of outer carbon shell, amorphous Void@SiO_x@C, and strong adhesive c‐PAA‐DS binder, c‐PAA‐DS/Void@SiO_x@C shows excellent electrochemical performance. Long cycling stability with a reversible capacity of 696 mAh g^?1 is obtained, as well as tiny capacity decay after 500 cycles at 0.5 A g^?1 and high‐rate performance. The prelithiated Void@SiO_x@C||LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) full cell is also assembled and shows a reversible capacity of 157 mAh g^?1 at 0.5 C, delivering an excellent capacity retention of 94% after 160 cycles.     

Extremely Small Pyrrhotite Fe7S8 Nanocrystals with Simultaneous Carbon‐Encapsulation for High‐Performance Na–Ion Batteries

Na/FeS_x batteries have remarkable potential applicability due to their high theoretical capacity and cost‐effectiveness. However, realization of high power‐capability and long‐term cyclability remains a major challenge. Herein, ultrafine Fe₇S₈@C nanocrystals (NCs) as a promising anode material for a Na–ion battery that addresses the above two issues simultaneously is reported. An Fe₇S₈ core with quantum size (≈10 nm) overcomes the kinetic and thermodynamic constraints of the Na‐S conversion reaction. In addition, the high degree of interconnection through carbon shells improves the electronic transport along the structure. As a result, the Fe₇S₈@C NCs electrode achieves excellent power capability of 550 mA h g^?1 (≈79% retention of its theoretical capacity) at a current rate of 2700 mA g^?1. Furthermore, a conformal carbon shell acts as a buffer layer to prevent severe volume change, which provides outstanding cyclability of ≈447 mA h g^?1 after 1000 cycles (≈71% retention of the initial charge capacity).     

MOF‐Derived Hollow Co9S8 Nanoparticles Embedded in Graphitic Carbon Nanocages with Superior Li‐Ion Storage

Novel electrode materials consisting of hollow cobalt sulfide nanoparticles embedded in graphitic carbon nanocages (HCSP?GCC) are facilely synthesized by a top‐down route applying room‐temperature synthesized Co‐based zeolitic imidazolate framework (ZIF‐67) as the template. Owing to the good mechanical flexibility and pronounced structure stability of carbon nanocages‐encapsulated Co₉S₈, the as‐obtained HCSP?GCC exhibit superior Li‐ion storage. Working in the voltage of 1.0?3.0 V, they display a very high energy density (707 Wh kg^?1), superior rate capability (reversible capabilities of 536, 489, 438, 393, 345, and 278 mA h g^?1 at 0.2, 0.5, 1, 2, 5, and 10C, respectively), and stable cycling performance (≈26% capacity loss after long 150 cycles at 1C with a capacity retention of 365 mA h g^?1). When the work voltage is extended into 0.01–3.0 V, a higher stable capacity of 1600 mA h g^?1 at a current density of 100 mA g^?1 is still achieved.