Nanocaging Silicon Nanoparticles into a Porous Carbon Framework toward Enhanced Lithium-Ion Storage

Silicon (Si) shows overwhelming promise as the high-capacity anode material of Li-ion batteries with high energy density. However, Si-based anodes are subjected to a limited electrochemical cycling lifetime due to their large volume change. Herein, a honeycomb-like biomass-derived carbon nanosheet framework is reported to encapsulate Si nanoparticles via a facile molten salt templating method. The carbon framework provides sufficient void space for effectively accommodating the large volume expansion of Si upon Li⁺ insertion. Moreover, the interconnected carbon skeletons afford fast electron/ion transport pathways for improving the reaction kinetics. Consequently, the porous Si/carbon composite could exhibit a high and stable Li storage capacity of 1022 mAh g⁻¹ at 0.2 A g⁻¹ over 100 cycles along with superior rate capability (555 mAh g⁻¹ at 5 A g⁻¹). This study demonstrates an effective structural design strategy for Si-based anodes toward stable lithium energy storage.     

Insert Zn Nanoparticles into the 3D Porous Carbon Ultrathin Films as a Superior Anode Material for Lithium Ion Battery

A flexible strategy is exploited to insert Zn nanoparticles into the pores of highly stable 3D network of carbon ultrathin films (P‐Zn/C) that can effectively localize the postformed Zn nanoparticles, thereby solving the problem of structural degradation, and thus achieve improved anode performance. A maximum capacity of 657.3 mA h g⁻¹ at a current density of 200 mA g⁻¹ after 50 cycles is achieved for P‐Zn/C. Even at a high current density of 2 A g⁻¹, a capacity of 653 mA h g⁻¹ is maintained after 1000 cycles, indicating that it could be a promising anode for lithium ion batteries. By comparing the capacitive and diffusion contribution qualitatively and quantitatively, the result reveals that the enhanced electrochemical performance mainly originates from the pseudocapacitance storage mechanism.     

Ge Nanoparticles Encapsulated in Interconnected Hollow Carbon Boxes as Anodes for Sodium Ion and Lithium Ion Batteries with Enhanced Electrochemical Performance

A carbothermal reaction route to Ge nanoparticle homogeneously encapsulated hollow carbon boxes from NH₄H₃Ge₂O₆/resorcinol formaldehyde precursors is designed, using NH₄H₃Ge₂O₆ as a Ge precursor from commercial GeO₂ and NH₄OH. The Ge/C hybrid anode for sodium ion battery displays a higher Na⁺ storage capacity of 346 mA h g^?1 after 500 cycles at a current density of 100 mA h g^?1, almost approaching the theoretical capacity of Ge. Furthermore, Ge/C anode shows significantly improved electrochemical performance for Li⁺ storage, showing a higher initial Coulombic efficiency of 85.1% and a superior reversible capacity of 1336 mA h g^?1 at a high current density of 200 mA g^?1 after 150 cycles. An excellent rate capability with a capacity of 825 mA h g^?1 at a current density of 4.0 A g^?1 can be obtained based on Ge/C anodes. The enhanced electrochemical performance can be attributed to the unique microstructures of Ge/C hybrid anode. The internal void space of hollow carbon boxes can accommodate the volume expansion of Ge during lithiation or sodiation process, thus preserving the structural integrity of electrode material. The interconnected carbon shell can increase the electronic conductivity of the electrode, resulting in the high rate capability and cycling stability.     

Encapsulating Tin Dioxide@Porous Carbon in Carbon Tubes: A Fiber‐in‐Tube Hierarchical Nanostructure for Superior Capacity and Long‐Life Lithium Storage

A novel fiber‐in‐tube hierarchical nanostructure of SnO₂@porous carbon in carbon tubes (SnO₂@PC/CTs) is creatively designed and synthesized though a carbon coating on scalable electrospun hybrid nanofibers template and a post‐etching technique. This 1D nanoarchitecture consists of double carbon‐buffering matrixes, i.e., the external carbon tubular shell and the internal porous carbon skeleton, which can work synergistically to address the various issues of SnO₂ nanoanode operation, such as pulverization, particle aggregation, and vulnerable electrical contacts between the SnO₂ nanoparticles and the carbon conductors. Thus, the as‐obtained SnO₂@PC/CTs nanohybrids used as a lithium‐ion‐battery anode exhibits a higher reversible capacity of 1045 mA h g^?1 at 0.5 A g^?1 after 300 cycles as well as a high‐rate cycling stability after 1000 cycles. The enhanced performance can be attributed to the wonderful merits of the external carbon protective shell for preserving the integrity of the overall electrode, and the internal porous carbon skeleton for inhibiting the aggregation and electrical isolation of the active particles during cycling.     

Epitaxial Growth of Urchin‐Like CoSe2 Nanorods from Electrospun Co‐Embedded Porous Carbon Nanofibers and Their Superior Lithium Storage Properties

A facile synthesis of porous graphitic carbon nanofibers (CNFs) with encapsulated Co nanoparticles (denote as Co@CNFs) via electrospinning and subsequent annealing is reported. The in situ generated Co nanoparticles (NPs) promote the CNF graphitization under a low temperature of 700 °C, which simultaneously results in the porous structure of the Co@CNFs with a large surface area (416 m² g^?1). Furthermore, urchin‐like CoSe₂ nanorods are epitaxially grown from the Co@CNFs via a facile hydrothermal selenation, in which the embedded Co NPs serve as directing seeds and sacrificial Co‐source, and CoSe₂ nanorods are rooted into the CNFs (denote as CoSe₂@CNFs). When used as anode materials for lithium ion batteries, the CoSe₂@CNFs demonstrate superior lithium storage properties, delivering a high reversible capacity of 1405 mA h g^?1 after 300 cycles at a current density of 200 mA g^?1. The enhanced lithium storage performance can be attributed to the novel hybrid structure, namely, the porous and graphitic CNFs can not only facilitate the charge/ion transfer but also buffer the volume changes of the electrode during lithiation/delithiation processes. More importantly, a general strategy is provided to graphitize amorphous carbon materials via the use of in situ generated transition metal nanoparticles as catalyst.     

Facile Synthesis of Porous MnO Microspheres for High‐Performance Lithium‐Ion Batteries

Manganese oxide is a highly promising anode material of lithium‐ion batteries (LIBs) for its low insertion voltage and high reversible capacity. Porous MnO microspheres are prepared by a facile method in this work. As an anode material of LIB, it can deliver a high reversible capacity up to 1234.2 mA h g^?1 after 300 cycles at 0.2 C, and a capacity of 690.0 mA h g^?1 in the 500th cycle at 2 C. The capacity increase with cycling can be attributed to the growth of reversible polymer/gel‐like film, and the better cycling stability and the superior rate performance can be attributed to the featured structure of the microspheres composed of nanoparticles with a short transport path for lithium ions, a large specific surface, and material/electrolyte contact area. The results suggest that the porous MnO microspheres can function as a promising anode material for high‐performance LIBs.     

A Facile Method for Synthesis of Porous NiCo2O4 Nanorods as a High‐Performance Anode Material for Li‐Ion Batteries

Porous electrode materials with large specific surface area, relatively short diffusion path, and higher electrical conductivity, which display both better rate capabilities and good cycle lives, have huge benefits for practical applications in lithium‐ion batteries. Here, uniform porous NiCo₂O₄ nanorods (PNNs) with pore‐size distribution in the range of 10–30 nm and lengths of up to several micrometers are synthesized through a convenient oxalate co‐precipitation method followed by a calcining process. The PNN electrode exhibits high reversible capacity and outstanding cycling stability (after 150 cycles still maintain about 650 mA h g^?1 at a current density of 100 mA g^?1), as well as high Coulombic efficiency (>98%). Moreover, the PNNs also exhibit an excellent rate performance, and deliver a stable reversible specific capacity of 450 mA h g^?1 even at 2000 mA g^?1. These results demonstrate that the PNNs are promising anode materials for high‐performance Li‐ion batteries.     

Highly Dispersed ZnSe Nanoparticles Embedded in N‐Doped Porous Carbon Matrix as an Anode for Potassium Ion Batteries

Advanced nanostructured functional materials obtained from the precursors of metal–organic frameworks show several unique advantages, including plentiful porous structures and large specific surface areas. Based on this, designed and constructed are highly dispersed ZnSe nanoparticles anchored in a N‐doped porous carbon rhombic dodecahedron (ZnSe@NDPC) by a sequential high‐temperature pyrolysis and selenization method. The specific synthesis process involves a two‐step heat treatment of the template‐engaged reaction between zinc‐based zeolitic imidazolate framework (ZIF‐8) and selenium power. By optimizing the calcination temperature, the as‐synthesized ZnSe@NDPC‐700 as an advanced anode of potassium ion batteries demonstrates the best electrochemical performance, including a high capacity (262.8 mA h g^?1 over 200 cycles at 100 mA g^?1) and a good rate capability (109.4 mA h g^?1 at 2000 mA g^?1 and 52.8 mA h g^?1 at 5000 mA g^?1). Moreover, the capacitance and diffusion mechanisms are also investigated by the qualitative and quantitate analysis, finally accounting for the superior K storage.     

Electrospinning Synthesis of Porous NiCoO2 Nanofibers as High‐Performance Anode for Lithium‐Ion Batteries

Nanostructured ternary/mixed transition metal oxides have attracted considerable attentions because of their high‐capacity and high‐rate capability in the electrochemical energy storage applications, but facile large‐scale fabrication with desired nanostructures still remains a great challenge. To overcome this, a facile synthesis of porous NiCoO₂ nanofibers composed of interconnected nanoparticles via an electrospinning–annealing strategy is reported herein. When examined as anode materials for lithium‐ion batteries, the as‐prepared porous NiCoO₂ nanofibers demonstrate superior lithium storage properties, delivering a high discharge capacity of 945 mA h g^?1 after 140 cycles at 100 mA g^?1 and a high rate capacity of 523 mA h g^?1 at 2000 mA g^?1. This excellent electrochemical performance could be ascribed to the novel hierarchical nanoparticle‐nanofiber assembly structure, which can not only buffer the volumetric changes upon lithiation/delithiation processes but also provide enlarged surface sites for lithium storage and facilitate the charge/electrolyte diffusion. Notably, a facile synthetic strategy for fabrication of ternary/mixed metal oxides with 1D nanostructures, which is promising for energy‐related applications, is provided.     

Hollow Silica Spheres Embedded in a Porous Carbon Matrix and Its Superior Performance as the Anode for Lithium‐Ion Batteries

Silica (SiO₂) is regarded as one of the most promising anode materials for lithium‐ion batteries due to the high theoretical specific capacity and extremely low cost. However, the low intrinsic electrical conductivity and the big volume change during charge/discharge cycles result in a poor electrochemical performance. Here, hollow silica spheres embedded in porous carbon (HSS–C) composites are synthesized and investigated as an anode material for lithium‐ion batteries. The HSS–C composites demonstrate a high specific capacity of about 910 mA h g^?1 at a rate of 200 mA g^?1 after 150 cycles and exhibit good rate capability. The porous carbon with a large surface area and void space filled both inside and outside of the hollow silica spheres acts as an excellent conductive layer to enhance the overall conductivity of the electrode, shortens the diffusion path length for the transport of lithium ions, and also buffers the volume change accompanied with lithium‐ion insertion/extraction processes.     

Graphene Nanosheets Suppress the Growth of Sb Nanoparticles in an Sb/C Nanocomposite to Achieve Fast Na Storage

Presently, graphene incorporation is one of the most effective strategies to develop superior electrode materials for sodium‐ion batteries (SIBs). Herein, it is excitingly found that an incorporated graphene nanosheet in the preparation processes can not only completely protect all the Sb nanoparticles in an Sb/C composite from being inactivated, but also suppresses their growth to undesirable micrometer size. While there are still many exposed Sb particulates on the surface of pristine Sb/C microplates, the graphene‐incorporated Sb/C/G nanocomposite consists of uniform Sb nanoparticles of 20–50 nm, all of which have been protected by and wrapped in the mixed carbon network. When used as anode materials for SIBs, the Sb/C/G nanocomposite exhibits the best Na‐storage properties in terms of the highest reversible capacity (650 mA h g^?1 at 0.025 A g^?1), fastest Na‐storage ability (290 mA h g^?1 at a high current density of 8 A g^?1), and optimal cycling performance (no capacity decay after 200 cycles), in comparison to pristine Sb/C and pure Sb. It is further revealed that the much enhanced performance should originate from the improvement of Na‐storage kinetics and increase of electronic conductivity via comparing the electrochemical impedance spectra, and cyclic voltammetry profiles, as well as the polarization variation along with current densities.     

Encapsulation of SnO2/Sn Nanoparticles into Mesoporous Carbon Nanowires and its Excellent Lithium Storage Properties

A peculiar nanostructure of encapsulation of SnO₂/Sn nanoparticles into mesoporous carbon nanowires (CNWs) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), X‐ray diffraction (XRD), BET, energy‐dispersive X‐ray (EDX) spectrometer, and X‐ray photoelectron spectroscopy (XPS) characterizations. The 1D mesoporous CNWs effectively accommodate the strain of volume change, prevent the aggregation and pulverization of nanostructured SnO₂/Sn, and facilitate electron and ion transport throughout the electrode. Moreover, the void space surrounding SnO₂/Sn nanoparticles also provides buffer spaces for the volumetric change of SnO₂/Sn during cycling, thus resulting in excellent cycling performance as potential anode materials for lithium‐ion batteries. Even after 499 cycles, a reversible capacity of 949.4 mAh g^?1 is retained at 800 mA g^?1. Its unique architecture should be responsible for the superior electrochemical performance.     

Graphene‐Based Phosphorus‐Doped Carbon as Anode Material for High‐Performance Sodium‐Ion Batteries

Graphene‐based phosphorus‐doped carbon (GPC) is prepared through a facile and scalable thermal annealing method by triphenylphosphine and graphite oxide as precursor. The P atoms are successfully doped into few layer graphene with two forms of P–O and P–C bands. The GPC used as anode material for Na‐ion batteries delivers a high charge capacity 284.8 mAh g^?1 at a current density of 50 mA g^?1 after 60 cycles. Superior cycling performance is also shown at high charge?discharge rate: a stable charge capacity 145.6 mAh g^?1 can be achieved at the current density of 500 mA g^?1 after 600 cycles. The result demonstrates that the GPC electrode exhibits good electrochemical performance (higher reversible charge capacity, super rate capability, and long‐term cycling stability). The excellent electrochemical performance originated from the large interlayer distance, large amount of defects, vacancies, and active site caused by P atoms doping. The relationship of P atoms doping amount with the Na storage properties is also discussed. This superior sodium storage performance of GPC makes it as a promising alternative anode material for sodium‐ion batteries.     

Carbon‐Encapsulated Tube‐Wire Co3O4/MnO2 Heterostructure Nanofibers as Anode Material for Sodium‐Ion Batteries

This study presents a general approach for the synthesis of carbon‐encapsulated wire‐in‐tube Co₃O₄/MnO₂ heterostructure nanofibers (Co₃O₄/MnO₂@C) via electrospinning followed by calcination. The as‐synthesized Co₃O₄/MnO₂@C is investigated as the sodium‐ion batteries anode material, which not only exhibits a high reversible capacity of 306 mAh g⁻¹ at 100 mA g⁻¹ over 200 cycles, but also shows a cycling stability of 126 mAh g⁻¹ after 1000 cycles at a high current density of 800 mA g⁻¹. The excellent electrochemical performance can be ascribed to the contribution from carbon‐encapsulated outer‐tube Co₃O₄ and inner‐wire MnO₂ heterostructures, which offer a large internal space and good electrical conductivity. The present work can be helpful in providing new insights into heterostructures for sodium‐ion batteries and other applications.     

Ultrathin MnO2 nanosheets grown on hollow carbon spheres with enhanced capacitive performance

Ultrathin MnO₂ nanosheets grown on the surface of hollow carbon spheres (MnO₂/HCSs) were fabricated by the redox reaction between carbon spheres with KMnO₄ in aqueous solution. Due to the porous structure and large amounts of active sites, MnO₂/HCSs exhibit excellent capacitive performance with 227.5 F g⁻¹ at 1 A g⁻¹. After 5000 cycles, the capacity retention of MnO₂/HCSs remains 96%, indicating its good cycling stability. These results demonstrate that MnO₂/HCSs are promising supercapacitor electrode material and this work provide a facile method for growth of ultrathin MnO₂ nanosheets on carbon substrate.     

Synthesis of Porous NiO Nanorods as High‐Performance Anode Materials for Lithium‐Ion Batteries

1D nanostructured metal oxides with porous structure have drawn wide attention to being used as high‐performance anode materials for lithium‐ion batteries (LIBs). This study puts forward a simple and scalable strategy to synthesize porous NiO nanorods with the help of a thermal treatment of metal‐organic frameworks in air. The NiO nanorods with an average diameter of approximately 38 nm are composed of nanosized primary particles. When evaluated as anode materials for LIBs, an initial discharge capacity of 743 mA h g^?1 is obtained at a current density of 100 mA g^?1, and a high reversible capacity is still maintained as high as 700 mA h g^?1 even after 60 charge–discharge cycles. The excellent electrochemical performance is mainly ascribed to the 1D porous structure.     

Carbon-coated silicon/crumpled graphene composite as anode material for lithium-ion batteries

Silicon is a promising anode material for high-capacity Li-ion batteries (LIBs). However, its insulating property and large volume change during the lithiation/delithiation process result in poor cycling stability and in pulverization of Si. In this work, glucose-derived carbon-coated Si nanoparticles (C–Si NPs) are in conjunction with crumpled graphene (cGr) particles by a spray-drying method to prepare a novel composite (C–Si/cGr) material. The prepared C–Si NPs are uniformly embedded in the ridges of the cGr particles. The carbon layer of C–Si can make a good contact with the graphene sheet, resulting in enhanced electrical conductivity and fast charge transfer. In addition, the unique crumpled structure of the cGr can buffer the large volume change upon cycling process and facilitate the diffusion of electrolyte into the composite material. When employed as an anode electrode of LIBs, the C–Si/cGr composites deliver enhanced electrochemical performance, including stable cycling with a discharge capacity of 790 mAh·g⁻¹ after 100 cycles and a rate capability of 654 mAh·g⁻¹ at 2C. The synergistic effect of the carbon layer coating of Si NPs and the crumpled structure of the cGr particles results in a composite with improved the electrochemical performance, which is likely related to its high electrical conductivity and good mechanical stability of composite material.     

Sulfur Immobilized in Hierarchically Porous Structured Carbon as Cathodes for Lithium–Sulfur Battery with Improved Electrochemical Performance

In order to overcome the main obstacles for lithium–sulfur batteries, such as poor conductivity of sulfur, polysulfide intermediate dissolution, and large volume change generated during the cycle process, a hard‐template route is developed to synthesize large‐surface area carbon with abundant micropores and mesopores to immobilize sulfur species. The microstructures of the C/S hybrids are investigated using field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherms, and electrochemical impedance spectroscopy techniques. The large surface and porous structure can effectively alleviate large strain due to the lithiation/delithiation process. More importantly, the micropores can effectively confine small molecules of sulfur in the form of S_2–4, avoiding loss of active S species and dissolution of high‐order lithium polysulfides. The porous C/S hybrids show significantly enhanced electrochemical performance with good cycling stability, high specific capacity, and rate capability. The C/S‐39 hybrid with an optimal content of 39 wt% S shows a reversible capacity of 780 mA h g^?1 after 100 cycles at the current density of 100 mA g^?1. Even at a current density of 5 A g^?1, the reversible capacity of C/S‐39 can still maintain at 420 mA h g^?1 after 60 cycles. This strategy offers a new way for solving long‐term reversibility obstacle and designing new cathode electrode architectures.     

Nitrogen-Doped Porous Graphene Coated with Fe3O4 Nanoparticles for Advanced Supercapacitor Electrode Material with Improved Electrochemical Performance

With the increasing demand for high-performance energy storage devices, single materials of ordinary structures for electrode materials have become increasingly difficult to meet people's needs. Therefore, composites of inimitable structures have drawn considerable attention. In this work, nitrogen-doped porous graphene coated with Fe₃O₄ nanoparticles (NPGF) is prepared by an efficient and green pyrolysis method. Structural and compositional characterizations confirm that the NPGF nanohybrids possess uniformly distributed pore structure and quite pure composition which is free of any impurities. In addition, electrochemical characterization verifies the excellent electrochemical performance, such as high-specific capacitance (713 F g⁻¹ at 1 A g⁻¹), prominent rate capability (capacitance retention of 77.3% and 67.9% when the current density is increased respectively from 1 to 10 and 20 A g⁻¹), and outstanding cycling stability (capacitance retention of 94.3% after 3000 cycles). Such promising results suggest that the NPGF nanohybrids have great application prospects in future high-performance supercapacitors.     

3D Array of Bi2S3 Nanorods Supported on Ni Foam as a Highly Efficient Integrated Oxygen Electrode for the Lithium‐Oxygen Battery

Bismuth sulfide nanorod array is directly grown on nickel foam (R‐Bi₂S₃/NF) to serve as a completely carbon and binder‐free 3D porous oxygen electrode material for lithium‐oxygen (Li‐O₂) batteries. The synergistic effect of the fast kinetics of electron transport and gas and electrolyte diffusion provided by the continuous free‐standing network structure and the excellent electrocatalytic activity of the bismuth sulfide nanorod array enables outstanding performance of the oxygen electrode. Li‐O₂ battery with the free‐standing R‐Bi₂S₃/NF oxygen electrode exhibits high energy efficiency (78.7%), good rate capability (4464 mA h g⁻¹ at 1500 mA g⁻¹), as well as excellent cyclability (146 cycles) while maintaining a moderate specific capacity of 1000 mA h g⁻¹. The effect of cathodes with different reactant (O₂) and intermediate (LiO₂) adsorbability on the product (Li₂O₂) growth model is studied by first‐principle calculations. The strong O₂ adsorption and weak LiO₂ adsorption on Bi₂S₃ drives the growth of large‐size Li₂O₂ particles via solution growth model. Remarkably, the large‐area pouch‐type Li‐O₂ battery delivers an energy density of 330 Wh kg⁻¹. The present results open up a promising avenue toward developing novel electrode architecture for high‐performance Li‐O₂ batteries through controlling morphology and functionality of porous electrodes.