An Advanced MoS2/Carbon Anode for High‐Performance Sodium‐Ion Batteries

Molybdenum disulfide (MoS₂) is a promising anode for high performance sodium‐ion batteries due to high specific capacity, abundance, and low cost. However, poor cycling stability, low rate capability and unclear electrochemical reaction mechanism are the main challenges for MoS₂ anode in Na‐ion batteries. In this study, molybdenum disulfide/carbon (MoS₂/C) nanospheres are fabricated and used for Na‐ion battery anodes. MoS₂/C nanospheres deliver a reversible capacity of 520 mAh g^?1 at 0.1 C and maintain at 400 mAh g^?1 for 300 cycles at a high current density of 1 C, demonstrating the best cycling performance of MoS₂ for Na‐ion batteries to date. The high capacity is attributed to the short ion and electron diffusion pathway, which enables fast charge transfer and low concentration polarization. The stable cycling performance and high coulombic efficiency (～100%) of MoS₂/C nanospheres are ascribed to (1) highly reversible conversion reaction of MoS₂ during sodiation/desodiation as evidenced by ex‐situ X‐ray diffraction (XRD) and (2) the formation of a stable solid electrolyte interface (SEI) layer in fluoroethylene carbonate (FEC) based electrolyte as demonstrated by fourier transform infrared spectroscopy (FTIR) measurements.     

3D Interconnected and Multiwalled Carbon@MoS2@Carbon Hollow Nanocables as Outstanding Anodes for Na‐Ion Batteries

Currently, the specific capacity and cycling performance of various MoS₂/carbon‐based anode materials for Na‐ion storage are far from satisfactory due to the insufficient structural stability of the electrode, incomplete protection of MoS₂ by carbon, difficult access of electrolyte to the electrode interior, as well as inactivity of the adopted carbon matrix. To address these issues, this work presents the rational design and synthesis of 3D interconnected and hollow nanocables composed of multiwalled carbon@MoS₂@carbon. In this architecture, (i) the 3D nanoweb‐like structure brings about excellent mechanical property of the electrode, (ii) the ultrathin MoS₂ nanosheets are sandwiched between and doubly protected by two layers of porous carbon, (iii) the hollow structure of the primary nanofibers facilitates the access of electrolyte to the electrode interior, (iv) the porous and nitrogen‐doping properties of the two carbon materials lead to synergistic Na‐storage of carbon and MoS₂. As a result, this hybrid material as the anode material of Na‐ion battery exhibits fast charge‐transfer reaction, high utilization efficiency, and ultrastability. Outstanding reversible capacity (1045 mAh g^?1), excellent rate behavior (817 mAh g^?1 at 7000 mA g^?1), and good cycling performance (747 mAh g^?1 after 200 cycles at 700 mA g^?1) are obtained.     

Hierarchical TiO2/SnO2 Hollow Spheres Coated with Graphitized Carbon for High‐Performance Electrochemical Li‐Ion Storage

A self‐templated strategy is developed to fabricate hierarchical TiO₂/SnO₂ hollow spheres coated with graphitized carbon (HTSO/GC‐HSs) by combined sol–gel processes with hydrothermal treatment and calcination. The as‐prepared mesoporous HTSO/GC‐HSs present an approximate yolk‐double–shell structure, with high specific area and small nanocrystals of TiO₂ and SnO₂, and thus exhibit superior electrochemical reactivity and stability when used as anode materials for Li‐ion batteries. A high reversible specific capacity of about 310 mAh g^?1 at a high current density of 5 A g^?1 can be achieved over 500 cycles indicating very good cycle stability and rate performance.     

Mesoporous Hollow Sb/ZnS@C Core–Shell Heterostructures as Anodes for High‐Performance Sodium‐Ion Batteries

Combining the advantage of metal, metal sulfide, and carbon, mesoporous hollow core–shell Sb/ZnS@C hybrid heterostructures composed of Sb/ZnS inner core and carbon outer shell are rationally designed based on a robust template of ZnS nanosphere, as anodes for high‐performance sodium‐ion batteries (SIBs). A partial cation exchange reaction based on the solubility difference between Sb₂S₃ and ZnS can transform mesoporous ZnS to Sb₂S₃/ZnS heterostructure. To get a stable structure, a thin contiguous resorcinol‐formaldehyde (RF) layer is introduced on the surface of Sb₂S₃/ZnS heterostructure. The effectively protective carbon layer from RF can be designed as the reducing agent to convert Sb₂S₃ to metallic Sb to obtain core–shell Sb/ZnS@C hybrid heterostructures. Simultaneously, the carbon outer shell is beneficial to the charge transfer kinetics, and can maintain the structure stability during the repeated sodiation/desodiation process. Owing to its unique stable architecture and synergistic effects between the components, the core–shell porous Sb/ZnS@C hybrid heterostructure SIB anode shows a high reversible capacity, good rate capability, and excellent cycling stability by turning the optimized voltage range. This novel strategy to prepare carbon‐layer‐protected metal/metal sulfide core–shell heterostructure can be further extended to design other novel nanostructured systems for high‐performance energy storage devices.     

Chemically Prelithiated Hard‐Carbon Anode for High Power and High Capacity Li‐Ion Batteries

Hard carbons (HC) have potential high capacities and power capability, prospectively serving as an alternative anode material for Li‐ion batteries (LIB). However, their low initial coulombic efficiency (ICE) and the resulting poor cyclability hinder their practical applications. Herein, a facile and effective approach is developed to prelithiate hard carbons by a spontaneous chemical reaction with lithium naphthalenide (Li‐Naph). Due to the mild reactivity and strong lithiation ability of Li‐Naph, HC anode can be prelithiated rapidly in a few minutes and controllably to a desirable level by tuning the reaction time. The as‐formed prelithiated hard carbon (pHC) has a thinner, denser, and more robust solid electrolyte interface layer consisting of uniformly distributed LiF, thus demonstrating a very high ICE, high power, and stable cyclability. When paired with the current commercial LiCoO₂ and LiFePO₄ cathodes, the assembled pHC/LiCoO₂ and pHC/LiFePO₄ full cells exhibit a high ICE of >95.0% and a nearly 100% utilization of electrode‐active materials, confirming a practical application of pHC for a new generation of high capacity and high power LIBs.     

Novel Carbon‐Encapsulated Porous SnO2 Anode for Lithium‐Ion Batteries with Much Improved Cyclic Stability

Porous SnO₂ submicrocubes (SMCs) are synthesized by annealing and HNO₃ etching of CoSn(OH)₆ SMCs. Bare SnO₂ SMCs, as well as bare commercial SnO₂ nanoparticles (NPs), show very high initial discharge capacity when used as anode material for lithium‐ion batteries. However, during the following cycles most of the Li ions previously inserted cannot be extracted, resulting in considerable irreversibility. Porous SnO₂ cubes have been proven to possess better electrochemical performance than the dense nanoparticles. After being encapsulated by carbon shell, the obtained yolk–shell SnO₂ SMCs@C exhibits significantly enhanced reversibility for lithium‐ions storage. The reversibility of the conversion between SnO₂ and Sn, which is largely responsible for the enhanced capacity, has been discussed. The porous SnO₂ SMCs@C shows much increased capacity and cycling stability, demonstrating that the porous SnO₂ core is essential for better lithium‐ion storage performance. The strategy introduced in this paper can be used as a versatile way to fabrication of various metal‐oxide‐based composites.     

SiOx Encapsulated in Graphene Bubble Film: An Ultrastable Li‐Ion Battery Anode

SiO_x is proposed as one of the most promising anodes for Li‐ion batteries (LIBs) for its advantageous capacity and stable Li uptake/release electrochemistry, yet its practical application is still a big challenge. Here encapsulation of SiO_x nanoparticles into conductive graphene bubble film via a facile and scalable self‐assembly in solution is shown. The SiO_x nanoparticles are closely wrapped in multilayered graphene to reconstruct a flake‐graphite‐like macrostructure, which promises uniform and agglomeration‐free distribution of SiO_x in the carbon while ensures a high mechanical strength and a high tap density of the composite. The composites present unprecedented cycling stability and excellent rate capabilities upon Li storage, rendering an opportunity for its anode use in the next‐generation high‐energy LIBs.     

FeP@C Nanotube Arrays Grown on Carbon Fabric as a Low Potential and Freestanding Anode for High‐Performance Li‐Ion Batteries

An anode of self‐supported FeP@C nanotube arrays on carbon fabric (CF) is successfully fabricated via a facile template‐based deposition and phosphorization route: first, well‐aligned FeOOH nanotube arrays are simply obtained via a solution deposition and in situ etching route with hydrothermally crystallized (Co,Ni)(CO₃)_0.5OH nanowire arrays as the template; subsequently, these uniform FeOOH nanotube arrays are transformed into robust carbon‐coated Fe₃O₄ (Fe₃O₄@C) nanotube arrays via glucose adsorption and annealing treatments; and finally FeP@C nanotube arrays on CF are achieved through the facile phosphorization of the oxide‐based arrays. As an anode for lithium‐ion batteries (LIBs), these FeP@C nanotube arrays exhibit superior rate capability (reversible capacities of 945, 871, 815, 762, 717, and 657 mA h g⁻¹ at 0.1, 0.2, 0.4, 0.8, 1.3, and 2.2 A g⁻¹, respectively, corresponding to area specific capacities of 1.73, 1.59, 1.49, 1.39, 1.31, 1.20 mA h cm⁻² at 0.18, 0.37, 0.732, 1.46, 2.38, and 4.03 mA cm⁻², respectively) and a stable long‐cycling performance (a high specific capacity of 718 mA h g⁻¹ after 670 cycles at 0.5 A g⁻¹, corresponding to an area capacity of 1.31 mA h cm⁻² at 0.92 mA cm⁻²).     

A Salt‐Templated Strategy toward Hollow Iron Selenides‐Graphitic Carbon Composite Microspheres with Interconnected Multicavities as High‐Performance Anode Materials for Sodium‐Ion Batteries

In this work, a facile salt‐templated approach is developed for the preparation of hollow FeSe₂/graphitic carbon composite microspheres as sodium‐ion battery anodes; these are composed of interconnected multicavities and an enclosed surface in‐plane embedded with uniform hollow FeSe₂ nanoparticles. As the precursor, Fe₂O₃/carbon microspheres containing NaCl nanocrystals are obtained using one‐pot ultrasonic spray pyrolysis in which inexpensive NaCl and dextrin are used as a porogen and carbon source, respectively, enabling mass production of the composites. During post‐treatment, Fe₂O₃ nanoparticles in the composites transform into hollow FeSe₂ nanospheres via the Kirkendall effect. These rational structures provide numerous conductive channels to facilitate ion/electron transport and enhance the capacitive contribution. Moreover, the synergistic effect between the hollow cavities within FeSe₂ and the outstanding mechanical strength of the porous carbon matrix can effectively accommodate the large volume changes during cycling. Correspondingly, the composite microsphere exhibits high discharge capacity of 510 mA h g^?1 after 200 cycles at 0.2 A g^?1 with capacity retention of 88% when calculated from the second cycle. Even at a high current density of 5.0 A g^?1, a high discharge capacity of 417 mA h g^?1 can be achieved.     

Designed Formation of Hybrid Nanobox Composed of Carbon Sheathed CoSe2 Anchored on Nitrogen‐Doped Carbon Skeleton as Ultrastable Anode for Sodium‐Ion Batteries

Research on sodium‐ion batteries (SIBs) has recently been revitalized due to the unique features of much lower costs and comparable energy/power density to lithium‐ion batteries (LIBs), which holds great potential for grid‐level energy storage systems. Transition metal dichalcogenides (TMDCs) are considered as promising anode candidates for SIBs with high theoretical capacity, while their intrinsic low electrical conductivity and large volume expansion upon Na⁺ intercalation raise the challenging issues of poor cycle stability and inferior rate performance. Herein, the designed formation of hybrid nanoboxes composed of carbon‐protected CoSe₂ nanoparticles anchored on nitrogen‐doped carbon hollow skeletons (denoted as CoSe₂@C∩NC) via a template‐assisted refluxing process followed by conventional selenization treatment is reported, which exhibits tremendously enhanced electrochemical performance when applied as the anode for SIBs. Specifically, it can deliver a high reversible specific capacity of 324 mAh g^?1 at current density of 0.1 A g^?1 after 200 cycles and exhibit outstanding high rate cycling stability at the rate of 5 A g^?1 over 2000 cycles. This work provides a rational strategy for the design of advanced hybrid nanostructures as anode candidates for SIBs, which could push forward the development of high energy and low cost energy storage devices.