Co3O4 Hollow Nanoparticles Embedded in Mesoporous Walls of Carbon Nanoboxes for Efficient Lithium Storage

Confining nanostructured electrode materials in porous carbon represents an effective strategy for improving the electrochemical performance of lithium-ion batteries. Herein, we report the design and synthesis of hybrid hollow nanostructures composed of highly dispersed Co₃O₄ hollow nanoparticles (sub-20 nm) embedded in the mesoporous walls of carbon nanoboxes (denoted as H-Co₃O₄@MCNBs) as an anode material for lithium-ion batteries. The facile metal–organic framework (MOF)-engaged strategy for the synthesis of H-Co₃O₄@MCNBs involves chemical etching-coordination and subsequent two-step annealing treatments. Owing to the unique structural merits including more active interfacial sites, effectively alleviated volume variation, good and stable electrical contact, and easy access of Li⁺ ions, the H-Co₃O₄@MCNBs exhibit excellent lithium-storage performance in terms of high specific capacity, excellent rate capability, and cycling stability.     

多级结构还原氧化石墨烯包覆的钴铁氧体的合成及电化学性能

以水滑石为前驱体合成微米花/纳米片多级结构过渡金属复合氧化物CoFe2O4,一种高性能锂离子电池负极材料。 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对其进行结构表征,发现得到的复合氧化物为单一晶相,且具有多级结构。 电化学性能测试表明,得到的负极材料具有高比容量和倍率性能。 通过还原氧化石墨烯(rGO)对CoFe2O4进行表面包覆制备CoFe2O4/rGO,其循环稳定性得到大幅度提高。     

Hierarchical Tubular Structures Composed of Co3O4 Hollow Nanoparticles and Carbon Nanotubes for Lithium Storage

Hierarchical tubular structures composed of Co₃O₄ hollow nanoparticles and carbon nanotubes (CNTs) have been synthesized by an efficient multi‐step route. Starting from polymer‐cobalt acetate (Co(Ac)₂) composite nanofibers, uniform polymer‐Co(Ac)₂@zeolitic imidazolate framework‐67 (ZIF‐67) core–shell nanofibers are first synthesized via partial phase transformation with 2‐methylimidazole in ethanol. After the selective dissolution of polymer‐Co(Ac)₂ cores, the resulting ZIF‐67 tubular structures can be converted into hierarchical CNTs/Co‐carbon hybrids by annealing in Ar/H₂ atmosphere. Finally, the hierarchical CNT/Co₃O₄ microtubes are obtained by a subsequent thermal treatment in air. Impressively, the as‐prepared nanocomposite delivers a high reversible capacity of 1281 mAh g^?1 at 0.1 A g^?1 with exceptional rate capability and long cycle life over 200 cycles as an anode material for lithium‐ion batteries.     

Hierarchical Nanotubes Constructed by Co9S8/MoS2 Ultrathin Nanosheets Wrapped with Reduced Graphene Oxide for Advanced Lithium Storage

Nanostructured hybrid metal sulfides have attracted intensive attention due to their fascinating properties that are unattainable by the single‐phased counterpart. Herein, we report an efficient approach to construct cobalt sulfide/molybdenum disulfide (Co₉S₈/MoS₂) wrapped with reduced graphene oxide (rGO). The unique structures constructed by ultrathin nanosheets and synergetic effects benefitting from bimetallic sulfides provide improved lithium ions reaction kinetics, and they retain good structural integrity. Interestingly, the conductive rGO can facilitate electron transfer, increase the electronic conductivity and accommodate the strain during cycling. When evaluated as anode materials for lithium‐ion batteries (LIBs), the resultant reduced graphene oxide‐coated cobalt sulfide/molybdenum disulfide (Co₉S₈/MoS₂@rGO) nanotubes deliver high specific capacities of 1140, 948, 897, 852, 820, 798 and 784 mAh g^?1 at the various discharging current densities of 0.2, 0.5, 1, 2, 3, 4 and 5 A g^?1, respectively. In addition, they can maintain an excellent cycle stability with a discharge capacity of 807 mAh g^?1 at 0.2 A g^?1 after 70 cycles, 787 mAh g^?1 at 1 A g^?1 after 180 cycles and 541 mAh g^?1 at 2 A g^?1 after 200 cycles. The proposed method may offer fundamental understanding for the rational design of other hybrid functional composites with high Li‐storage properties.     

双金属有机骨架衍生的Fe-CrSe/C负极材料制备及储锂性能

为了开发电化学性能优异的新型金属有机骨架基衍生材料,以对苯二甲酸、三氯化铬和九水合硝酸铁作为原料,通过微波法合成了双金属有机骨架材料（Fe-Cr-MOF）。在氮气保护下,对Fe-Cr-MOF进行高温硒化得到纳米颗粒状Fe-CrSe/C复合材料,用作锂离子电池负极。结果表明,在100 mA·g^-1的电流密度下,Fe-CrSe/C电极的首圈可逆比容量达到958.4 mAh·g^-1,循环150圈后比容量还能维持891.6 mAh·g^-1。     

Low‐Temperature Synthesis of Honeycomb CuP2@C in Molten ZnCl2 Salt for High‐Performance Lithium Ion Batteries

Phosphorus‐rich metal phosphides have very high lithium storage capacities, but they are difficult to prepare. A low‐temperature phosphorization method based on Mg reducing PCl₃ in ZnCl₂ molten salt at 300 °C is developed to synthesize phosphorus‐rich CuP₂@C from a Cu‐MOF derived Cu@C composite. Abnormal oxidation of Cu by Zn²⁺ in the molten salt is observed, which leads to the porous honeycomb nanostructure and homogeneously distributed ultrafine CuP₂ nanocrystals. The honeycomb CuP₂@C exhibits excellent lithium storage performance with high reversible capacity (1146 mAh g^?1 at 0.2 A g^?1) and superior cycling stability (720 mAh g^?1 after 600 cycles at 1.0 A g^?1), showing the promising application of P‐rich metal phosphides in lithium ion batteries.     

磷酸铁锂电池低温性能的改性方法简述

LiFePO₄电极材料具有比容量高、工作电压稳定、成本低及环境友好等优点,被视为理想的锂离子电池正极材料,是目前电动汽车主要正极材料之一。 然而在低温下LiFePO₄电池性能显著降低,限制了其在冬季和高寒地区中的使用。 研究人员分析了低温下磷酸铁锂电池性能快速下降的原因,并提出解决办法。 本文概述了提高磷酸铁锂电池低温性能的4个方法:1)脉冲电流;2)电解液添加剂;3)表面包覆;4)体相掺杂。     

Structural and Electrochemical Study of Vanadium‐Doped TiO2 Ramsdellite with Superior Lithium Storage Properties for Lithium‐Ion Batteries

Titanium‐oxide‐based materials are considered attractive and safe alternatives to carbonaceous anodes in Li‐ion batteries. In particular, the ramsdellite form TiO₂(R) is known for its superior lithium‐storage ability as the bulk material when compared with other titanates. In this work, we prepared V‐doped lithium titanate ramsdellites with the formula Li_0.5Ti_1?xV_xO₂ (0≤x≤0.5) by a conventional solid‐state reaction. The lithium‐free Ti_1?xV_xO₂ compounds, in which the ramsdellite framework remains virtually unaltered, are easily obtained by a simple aqueous oxidation/ion‐extraction process. Neutron powder diffraction is used to locate the Li channel site in Li_0.5Ti_1?xV_xO₂ compounds and to follow the lithium extraction by difference‐Fourier maps. Previously delithiated Ti_1?xV_xO₂ ramsdellites are able to insert up to 0.8 Li⁺ per transition‐metal atom. The initial gravimetric capacities of 270 mAh g^?1 with good cycle stability under constant current discharge conditions are among the highest reported for bulk TiO₂‐related intercalation compounds for the threshold of one e^? per formula unit.     

Unusual Formation of CoSe@carbon Nanoboxes,which have an Inhomogeneous Shell,for Efficient Lithium Storage

Hybrid hollow nanostructures with tailored shell architectures are attractive for electrochemical energy storage applications. Starting with metal–organic frameworks (MOFs), we demonstrate a facile formation of hybrid nanoboxes with complex shell architecture where a CoSe‐enriched inner shell is intimately confined within a carbon‐enriched outer shell (denoted as CoSe@carbon nanoboxes). The synthesis is realized through manipulation of the template‐engaged reaction between Co‐based zeolitic imidazolate framework (ZIF‐67) nanocubes and Se powder at elevated temperatures. By virtue of the structural and compositional features, these unique CoSe@carbon nanoboxes manifest excellent lithium‐storage performance in terms of high specific capacity, exceptional rate capability, excellent cycling stability, and high initial Coulombic efficiency.     

锂离子电池正极材料LiMn_(2-2x)Sm_xSr_xO_4的合成及电化学性能

采用高温固相反应合成了一系列的LiMn2-2xSmxSrxO4正极材料(0≤x≤0.1);采用X射线衍射仪分析了合成产物的晶体结构;利用充放电试验测定了产物的电化学性能,利用电化学阻抗谱分析了产物的电化学循环机理.结果表明,所合成的LiMn2-2xSmxSrxO4(x=0,0.01,0.02,0.03,0.04,0.05)样品均保持尖晶石相,属于Fd3m空间群.LiMn1.9Sm0.05Sr0.05O4的电化学性能最佳,首次放电容量为96.8 mAh/g,在3.0~4.4 V区间内50次循环后容量保持率超过96%.与此同时,LiMn2O4和LiMn1.90Sm0.05Sr0.05O4的电极阻抗变化不同,进而影响其电化学性能.     

晶态Li12Si7锂离子电池负极材料的电化学性能研究

通过加热摩尔比为12:7的LiH/Si球磨混合物,避免了Li与Si之间巨大的熔点差异,成功制备了晶态Li₁₂Si₇合金,研究了其电化学性能和储锂机制. 发现Li₁₂Si₇在0.02 ~ 0.6 V的嵌脱锂过程中,只发生晶胞体积的变化,而不产生相变,呈现出明显的固溶储锂机制. 该固溶储锂机制的存在,有效抑制了Si基负极材料嵌脱锂过程中由于相变导致的体积效应,使得晶态Li₁₂Si₇在0.02 ~ 0.6 V电压范围内具有显著改善的电化学性能,其首次库伦效率高达100%,30次循环后的可逆容量保持率约为74%,分别优于相同条件下原始Si电极的55%和37%.     

Wintersweet‐Flower‐Like CoFe2O4/MWCNTs Hybrid Material for High‐Capacity Reversible Lithium Storage

CoFe₂O₄/multiwalled carbon nanotubes (MWCNTs) hybrid materials were synthesized by a hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy analysis confirmed the morphology of the as‐prepared hybrid material resembling wintersweet flower “buds on branches”, in which CoFe₂O₄ nanoclusters, consisting of nanocrystals with a size of 5–10 nm, are anchored along carbon nanotubes. When applied as an anode material in lithium ion batteries, the CoFe₂O₄/MWCNTs hybrid material exhibited a high performance for reversible lithium storage. In particular, the hybrid anode material delivered reversible lithium storage capacities of 809, 765, 539, and 359 mA h g^?1 at current densities of 180, 450, 900, and 1800 mA g^?1, respectively. The superior performance of CoFe₂O₄/MWCNTs hybrid materials could be ascribed to the synergistic pinning effect of the wintersweet‐flower‐like nanoarchitecture. This strategy could also be applied to synthesize other metal oxide/CNTs hybrid materials as high‐capacity anode materials for lithium ion batteries.     

Formation of CoS2 Nanobubble Hollow Prisms for Highly Reversible Lithium Storage

Metal–organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy‐related applications. Herein we report a facile two‐step diffusion‐controlled strategy to generate novel MOFs derived hierarchical hollow prisms composed of Nanosized CoS₂ bubble‐like subunits. Uniform zeolitic imidazolate framework‐67 (ZIF‐67) hollow prisms assembled by interconnected nanopolyhedra are first synthesized via a transformation process. Afterwards, these ZIF‐67 building blocks are converted into CoS₂ bubble‐like hollow particles to form the complex hollow prisms through a sulfidation reaction with an additional annealing treatment. When evaluated as an electrode material for lithium‐ion batteries, the as‐obtained CoS₂ nanobubble hollow prisms show remarkable electrochemical performance with good rate capability and long cycle life.     

花球状二硫化钒的制备及其储锂研究

采用一步水热法并添加表面活性剂聚乙二醇400制备出花球状二硫化钒,利用X射线粉末衍射仪、场发射扫描电子显微镜等方法对产物的物相和形貌进行了表征. 观测生长过程发现花球状二硫化钒由若干六边形二硫化钒纳米片堆叠穿插组成,该花球状结构使材料拥有较高的比表面积及出色的结构稳定性. 将花球状二硫化钒用于锂离子电池正极材料测试,结果表明花球状二硫化钒在电压区间为1 ~ 3 V,电流密度为200 mA·g^-1时具有出色的循环稳定性且循环50周之后容量可达450 mAh·g^-1.     

Synthesis of 2D/2D Structured Mesoporous Co3O4 Nanosheet/N‐Doped Reduced Graphene Oxide Composites as a Highly Stable Negative Electrode for Lithium Battery Applications

Mesoporous Co₃O₄ nanosheets (Co₃O₄‐NS) and nitrogen‐doped reduced graphene oxide (N‐rGO) are synthesized by a facile hydrothermal approach, and the N‐rGO/Co₃O₄‐NS composite is formulated through an infiltration procedure. Eventually, the obtained composites are subjected to various characterization techniques, such as XRD, Raman spectroscopy, surface area analysis, X‐ray photoelectron spectroscopy (XPS), and TEM. The lithium‐storage properties of N‐rGO/Co₃O₄‐NS composites are evaluated in a half‐cell assembly to ascertain their suitability as a negative electrode for lithium‐ion battery applications. The 2D/2D nanostructured mesoporous N‐rGO/Co₃O₄‐NS composite delivered a reversible capacity of about 1305 and 1501 mAh g^?1 at a current density of 80 mA g^?1 for the 1st and 50th cycles, respectively. Furthermore, excellent cyclability, rate capability, and capacity retention characteristics are noted for the N‐rGO/Co₃O₄‐NS composite. This improved performance is mainly related to the existence of mesoporosity and a sheet‐like 2D hierarchical morphology, which translates into extra space for lithium storage and a reduced electron pathway. Also, the presence of N‐rGO and carbon shells in Co₃O₄‐NS should not be excluded from such exceptional performance, which serves as a reliable conductive channel for electrons and act as synergistically to accommodate volume expansion upon redox reactions. Ex‐situ TEM, impedance spectroscopy, and XPS, are also conducted to corroborate the significance of the 2D morphology towards sustained lithium storage.     

Nanostructure Sn/C Composite High-Performance Negative Electrode for Lithium Storage

Tin-based nanocomposite materials embedded in carbon frameworks can be used as effective negative electrode materials for lithium-ion batteries (LIBs), owing to their high theoretical capacities with stable cycle performance. In this work, a low-cost and productive facile hydrothermal method was employed for the preparation of a Sn/C nanocomposite, in which Sn particles (sized in nanometers) were uniformly dispersed in the conductive carbon matrix. The as-prepared Sn/C nanocomposite displayed a considerable reversible capacity of 877 mAhg⁻¹ at 0.1 Ag⁻¹ with a high first cycle charge/discharge coulombic efficiency of about 77%, and showed 668 mAh/g even at a relatively high current density of 0.5 Ag⁻¹ after 100 cycles. Furthermore, excellent rate capability performance was achieved for 806, 697, 630, 516, and 354 mAhg⁻¹ at current densities 0.1, 0.25, 0.5, 0.75, and 1 Ag⁻¹, respectively. This outstanding and significantly improved electrochemical performance is attributed to the good distribution of Sn nanoparticles in the carbon framework, which helped to produce Sn/C nanocomposite next-generation negative electrodes for lithium-ion storage.     

锂离子电池正极材料的晶体结构及电化学性能

正极材料是锂离子电池的重要组成部分。作为提供自由脱嵌锂离子的正极材料,其晶体结构的特点决定了锂离子脱嵌路径方式的不同,并对锂离子电池的电化学性能等产生明显影响。本文根据正极材料的晶体结构和锂离子“脱嵌/嵌入”路径方式的不同,重点讨论了一维隧道结构、二维层状结构和三维框架结构正极材料的晶体结构特点、锂离子“脱嵌/嵌入”路径和其电化学性能之间的关系,主要包括一维隧道结构正极材料LiFePO₄,二维层状结构正极材料LiMO₂(M=Co, Ni, Mn)、Li_1+xV₃O₈和Li₂MSiO₄ (M=Fe, Mn) 以及三维框架结构正极材料LiMn₂O₄和Li₃V₂(PO₄)₃。揭示了目前锂离子电池正极材料的研究现状和存在问题,并对今后的发展方向进行了评述。     

Porous Co3O4 Nanosheets with Extraordinarily High Discharge Capacity for Lithium Batteries

Cobalt and battery charge : Porous Co₃O₄ with a hexagonal sheetlike structure has been synthesized through precursor Co(OH)₂ hexagonal nanosheets (see figure). The as‐prepared nanosheets exhibit excellent Li‐battery performance with a good cycle life and high capacity (1450 mAh g^?1).