Confined Amorphous Red Phosphorus in MOF‐Derived N‐Doped Microporous Carbon as a Superior Anode for Sodium‐Ion Battery

Red phosphorus (P) has attracted intense attention as promising anode material for high‐energy density sodium‐ion batteries (NIBs), owing to its high sodium storage theoretical capacity (2595 mAh g^?1). Nevertheless, natural insulating property and large volume variation of red P during cycling result in extremely low electrochemical activity, leading to poor electrochemical performance. Herein, the authors demonstrate a rational strategy to improve sodium storage performance of red P by confining nanosized amorphous red P into zeolitic imidazolate framework‐8 (ZIF‐8) ‐derived nitrogen‐doped microporous carbon matrix (denoted as P@N‐MPC). When used as anode for NIBs, the P@N‐MPC composite displays a high reversible specific capacity of ≈600 mAh g^?1 at 0.15 A g^?1 and improved rate capacity (≈450 mAh g^?1 at 1 A g^?1 after 1000 cycles with an extremely low capacity fading rate of 0.02% per cycle). The superior sodium storage performance of the P@N‐MPC is mainly attributed to the novel structure. The N‐doped porous carbon with sub‐1 nm micropore facilitates the rapid diffusion of organic electrolyte ions and improves the conductivity of the encapsulated red P. Furthermore, the porous carbon matrix can buffer the volume change of red P during repeat sodiation/desodiation process, keeping the structure intact after long cycle life.     

Multichannel Porous TiO2 Hollow Nanofibers with Rich Oxygen Vacancies and High Grain Boundary Density Enabling Superior Sodium Storage Performance

TiO₂ as an anode for sodium‐ion batteries (NIBs) has attracted much recent attention, but poor cyclability and rate performance remain problematic owing to the intrinsic electronic conductivity and the sluggish diffusivity of Na ions in the TiO₂ matrix. Herein, a simple process is demonstrated to improve the sodium storage performance of TiO₂ by fabricating a 1D, multichannel, porous binary‐phase anatase‐TiO₂–rutile‐TiO₂ composite with oxygen‐deficient and high grain‐boundary density (denoted as a‐TiO_2?x /r‐TiO_2?x ) via electrospinning and subsequent vacuum treatment. The introduction of oxygen vacancies in the TiO₂ matrix enables enhanced intrinsic electronic conductivity and fast sodium‐ion diffusion kinetics. The porous structure offers easy access of the liquid electrolyte and a short transport path of Na⁺ through the pores toward the TiO₂ nanoparticle. Furthermore, the high density of grain boundaries between the anatase TiO₂ and rutile TiO₂ offer more interfaces for a novel interfacial storage. The a‐TiO_2?x /r‐TiO_2?x shows excellent long cycling stability (134 mAh g^?1 at 10 C after 4500 cycles) and superior rate performance (93 mAh g^?1 after 4500 cycles at 20 C) for sodium‐ion batteries. This simple and effective process could serve as a model for the modification of other materials applied in energy storage systems and other fields.     

Hierarchical Interconnected Expanded Graphitic Ribbons Embedded with Amorphous Carbon: An Advanced Carbon Nanostructure for Superior Lithium and Sodium Storage

Carbon materials have attracted considerable attention as anodes for lithium‐ion and sodium‐ion batteries due to their low cost and environmental friendliness. This work reports an advanced carbon nanostructure that takes advantage of the chelation effect of glucose and metal ions, which ensures the uniform dispersion of metal in the precursor. Thus, an effective catalytic conversion from sp³ to sp² carbon occurs, enabling simultaneously formation of pores with catalyzed graphitic structures. Due to the low carbonization temperature and short carbonization time as well as the different catalytic degree of various metals, a series of expanded graphitic layers from 0.34 to 0.44 nm with defects and amorphous carbon structure are obtained. The structure not only offers accessible graphitic spacings for reversible lithium/sodium ion insertion, but also provides abundant active sites for lithium/sodium ion adsorption in the defects and amorphous structure. Moreover, the hierarchical interconnected porous structure combining graphitic ribbons is beneficial for fast electronic/ionic transport and favorable electrolyte permeation. More importantly, such advanced carbon materials prove their feasibility for balancing the pore structure and degree of graphitization. When serving as the electrode material for lithium‐ion and sodium‐ion batteries, excellent electrochemical performance along with fast kinetics and long cycle life is achieved.     

Ultrafast Sodium/Potassium‐Ion Intercalation into Hierarchically Porous Thin Carbon Shells

The large‐scale application of sodium/potassium‐ion batteries is severely limited by the low and slow charge storage dynamics of electrode materials. The crystalline carbons exhibit poor insertion capability of large Na⁺/K⁺ ions, which limits the storage capability of Na/K batteries. Herein, porous S and N co‐doped thin carbon (S/N@C) with shell‐like (shell size ≈20–30 nm, shell wall ≈8–10 nm) morphology for enhanced Na⁺/K⁺ storage is presented. Thanks to the hollow structure and thin shell‐wall, S/N@C exhibits an excellent Na⁺/K⁺ storage capability with fast mass transport at higher current densities, leading to limited compromise over charge storage at high charge/discharge rates. The S/N@C delivers a high reversible capacity of 448 mAh g^‐1 for Na battery, at the current density of 100 mA g^‐1 and maintains a discharge capacity up to 337 mAh g^‐1 at 1000 mA g^‐1. Owing to shortened diffusion pathways, S/N@C delivers an unprecedented discharge capacity of 204 and 169 mAh g^‐1 at extremely high current densities of 16 000 and 32 000 mA g^‐1, respectively, with excellent reversible capacity for 4500 cycles. Moreover, S/N@C exhibits high K⁺ storage capability (320 mAh g^‐1 at current density of 50 mA g^‐1) and excellent cyclic life.     

Metal Cation‐Assisted Synthesis of Amorphous B,N Co‐Doped Carbon Nanotubes for Superior Sodium Storage

Nearly inexhaustible sodium sources on earth make sodium ion batteries (SIBs) the best candidate for large‐scale energy storage. However, the main obstacles faced by SIBs are the low rate performance and poor cycle stability caused by the large size of Na⁺ ions. Herein, a universal strategy for synthesizing amorphous metals encapsulated into amorphous B, N co‐doped carbon (a‐M@a‐BCN; M = Co, Ni, Mn) nanotubes by metal cation‐assisted carbonization is explored. The methodology allows tailoring the structures (e.g., length, wall thickness, and metals doping) of a‐M@a‐BCN nannotubes at the molecular level. Furthermore, the amorphous metal sulfide encapsulated into a‐BCN (a‐MS_x@a‐BCN; MS_x: CoS, Ni₃S₂, MnS) nanotubes are obtained by one‐step sulfidation process. The a‐M@a‐BCN and a‐MS_x@a‐BCN possess the larger interlayer spacing (0.40 nm) amorphous carbon nanotube rich in heteroatoms active sites, making them exhibit excellent Na⁺ ions diffusion kinetics and capacitive storage behavior. As SIBs anodes, they show high capacity, excellent rate performance, and long cycle stability.     

红磷/碳复合材料的制备及电化学性能研究

对比研究了不同制备方法、电解液组成和碳结构对红磷/碳复合材料电化学性能的影响。利用球磨法制备了红磷/活性炭(AC)复合材料, 其较差的首次库伦效率和循环容量表明活性物质红磷没有得到有效利用。对多种电解液进行了优选, 得到最优电解液为1 mol/L LiPF₆的EC/EMC/DMC (1: 1: 1 V/V)酯类电解液。通过气相沉积法制备了红磷/导电碳黑(BP2000)和红磷/活性炭两种复合材料。利用热重分析(TGA)、X射线衍射分析(XRD)、扫描电子显微镜(SEM)、BET比表面分析和循环伏安法(CV)对上述复合材料的形貌、结构和电化学性能进行了研究。结果表明: 含磷量为45%的红磷/活性炭复合材料充放电平台分别为1.0 V和0.75 V, 具有良好的可逆性。首次放电比容量和充电比容量分别为1500和1200 mAh/g, 库伦效率为82.5%。随后循环中库伦效率超过了97.5%。其1200 mAh/g的循环容量对应于2.8个电子的可逆反应。以第二次的稳定放电容量计算, 50次循环后容量保持率为75.0%。该复合材料较高的循环容量和良好的循环稳定性受益于无定形的活性物质红磷在活性炭导电基底孔结构中, 特别是微孔中的均匀分布。     

Superior Sodium Storage in 3D Interconnected Nitrogen and Oxygen Dual‐Doped Carbon Network

Carbonaceous materials have attracted immense interest as anode materials for Na‐ion batteries (NIBs) because of their good chemical, thermal stabilities, as well as high Na‐storage capacity. However, the carbonaceous materials as anodes for NIBs still suffer from the lower rate capability and poor cycle life. An N,O‐dual doped carbon (denoted as NOC) network is designed and synthesized, which is greatly favorable for sodium storage. It exhibits high specific capacity and ultralong cycling stability, delivering a capacity of 545 mAh g^?1 at 100 mA g^?1 after 100 cycles and retaining a capacity of 240 mAh g^?1 at 2 A g^?1 after 2000 cycles. The NOC composite with 3D well‐defined porosity and N,O‐dual doped induces active sites, contributing to the enhanced sodium storage. In addition, the NOC is synthesized through a facile solution process, which can be easily extended to the preparation of many other N,O‐dual doped carbonaceous materials for wide applications in catalysis, energy storage, and solar cells.     

Porous Carbon Nanofibers Encapsulated with Peapod‐Like Hematite Nanoparticles for High‐Rate and Long‐Life Battery Anodes

Fe₂O₃ is regarded as a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe₂O₃ anodes, leading to rapid fading of the capacity. Herein, a novel peapod‐like nanostructured material, consisting of Fe₂O₃ nanoparticles homogeneously encapsulated in the hollow interior of N‐doped porous carbon nanofibers, as a high‐performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea‐like Fe₂O₃ nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na‐ions. As a consequence, this peapod‐like structure exhibits a stable discharge capacity of 1434 mAh g^?1 (at 100 mA g^?1) and 806 mAh g^?1 (at 200 mA g^?1) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g^?1 after 1000 cycles and 396 mAh g^?1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g^?1. This study provides a promising strategy for developing long‐cycle‐life LIBs and SIBs.     

生物质玉米秸秆衍生碳材料的制备及其储钠性能

当代农业产生大量农作物秸秆残渣,对环境和生活产生极大影响,尤其是大量的焚烧。因此,农作物残渣的有效利用受到广泛关注。利用玉米秸秆茎髓为碳源,通过简单的高温碳化和化学膨化处理成功地合成了性能优异的碳片。物性结构研究表明,得到的碳材料呈现出天然蜂窝状截面和中空管状阵列结构的纵截面,并具有丰富的孔洞,有利于钠离子传输和扩散。(002)晶面表明,碳片的层间距为0.376nm(石墨为0.335nm),这有利于钠离子的脱嵌,从而提高电池的电化学性能。经1 200℃碳化合成的茎髓碳片(SPCS-1200)比900℃碳化合成的碳材料(SPC-900)表现出更好的储钠性能。在50mA·g-1电流密度下,循环100圈后SPCS-1200可以提供稳定的可逆比容量(203mAh·g-1),而SPC-900的可逆比容量仅为173mAh·g-1。此外,SPCS-1200也显示出优异的倍率性能,在1 000mA·g-1电流密度下比容量为100.7mAh·g-1,在2 000mA·g-1电流密度下表现出65.9mAh·g-1的比容量。然而,在相应的电流密度下,SPC-900分别表现出45.7mAh·g-1和31.2mAh·g-1的比容量。     

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).     

Fe2VO4 Hierarchical Porous Microparticles Prepared via a Facile Surface Solvation Treatment for High‐Performance Lithium and Sodium Storage

Preventing the aggregation of nanosized electrode materials is a key point to fully utilize the advantage of the high capacity. In this work, a facile and low‐cost surface solvation treatment is developed to synthesize Fe₂VO₄ hierarchical porous microparticles, which efficiently prevents the aggregation of the Fe₂VO₄ primary nanoparticles. The reaction between alcohol molecules and surface hydroxy groups is confirmed by density functional theory calculations and Fourier transform infrared spectroscopy. The electrochemical mechanism of Fe₂VO₄ as lithium‐ion battery anode is characterized by in situ X‐ray diffraction for the first time. This electrode material is capable of delivering a high reversible discharge capacity of 799 mA h g^?1 at 0.5 A g^?1 with a high initial coulombic efficiency of 79%, and the capacity retention is 78% after 500 cycles. Moreover, a remarkable reversible discharge capacity of 679 mA h g^?1 is achieved at 5 A g^?1. Furthermore, when tested as sodium‐ion battery anode, a high reversible capacity of 382 mA h g^?1 can be delivered at the current density of 1 A g^?1, which still retains at 229 mA h g^?1 after 1000 cycles. The superior electrochemical performance makes it a potential anode material for high‐rate and long‐life lithium/sodium‐ion batteries.     

Efficient Sodium Storage in Rolled‐Up Amorphous Si Nanomembranes

Alloying‐type materials are promising anodes for high‐performance sodium‐ion batteries (SIBs) because of their high capacities and low Na‐ion insertion potentials. However, the typical candidates, such as P, Sn, Sb, and Pb, suffer from severe volume changes (≈293–487%) during the electrochemical reactions, leading to inferior cycling performances. Here, a high‐rate and ultrastable alloying‐type anode based on the rolled‐up amorphous Si nanomembranes is demonstrated. The rolled‐up amorphous Si nanomembranes show a very small volume change during the sodiation/desodiation processes and deliver an excellent rate capability and ultralong cycle life up to 2000 cycles with 85% capacity retention. The structural evolution and pseudocapacitance contribution are investigated by using the ex situ characterization techniques combined with kinetics analysis. Furthermore, the mechanism of efficient sodium‐ion storage in amorphous Si is kinetically analyzed through an illustrative atomic structure with dangling bonds, offering a new perspective on understanding the sodium storage behavior. These results suggest that nanostructured amorphous Si is a promising anode material for high‐performance SIBs.     

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.