MnO octahedral nanocrystals and MnO@C core-shell composites: synthesis, characterization, and electrocatalytic properties

We present a simple and facile synthesis of MnO octahedral nanocrystals and MnO@C core-shell composite nanoparticles. The synthesis is accomplished by a single-step direct pyrolysis of cetyltrimethylammonium permanganate in specially made Let-lock union cells. The products are characterized by HRSEM, HRTEM, Raman spectroscopy, and cyclic voltammetry (CV). The product consists mainly of octahedral MnO nanocrystals and MnO coated with carbon (MnO@C). The core-shell particles are observed only when the core size is smaller than 150 nm. The shape of the nanocrystals can be controlled by varying parameters such as reaction temperature and duration. As the temperature increases from 600 to 800 degrees C, the octahedral MnO crystals observed are without any carbon shell. The effect of time and temperature on the octahedral MnO nanocrystal formation is described. The electrocatalytic activities of the products are studied for oxygen reduction reaction in aqueous basic medium and are compared with bulk MnO. The MnO nanocrystals and core-shell composites exhibit higher activity than that of bulk MnO.     

The design and fabrication of Co_3O_4/Co_3V_2O_8/Ni nanocomposites as high-performance anodes for Li-ion batteries

The Co_3O_4/Co_3V_2O_8/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) Co_3O_4 nanowire arrays directly grew on Ni foam, whereas the 1D Co_3V_2O_8 nanowires adhered to parts of Co_3O_4 nanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of Co_3O_4/Co_3V_2O_8/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such Co_3O_4/Co_3V_2O_8/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.     

常压回流掺钴钙锰矿锂离子电池正极材料

常压回流法制备掺杂钴离子的钙锰矿,X-射线衍射(XRD)、热重(TG)、化学分析等测试表明:钙锰矿均为单一相,组成为MgxCoyMnOz·nH2O,其中0.18≤x≤0.22、0≤y≤0.24、2.10≤z≤2.53、0.35≤n≤0.73.以掺钴钙锰矿作锂离子二次电池正极材料,组成为Tod-Co10%(10%Co的Mg0.18Co0.12MnO2.19·0.45H2O)电极放电性能最佳,其首次放电比容量为219mAh/g,100次循环充放电仍有102mAh/g.对比之下,未掺钴的Tod-Co0%电极(钙锰矿)首次放电比容量为211mAh/g,30次循环后为37mAh/g.     

Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide

Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40?mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100?m(2) g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167?F?g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210?F?g(-1) with good cyclability of around 95-97?% up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials.     

五氧化二钒空心球制备及其作为镁二次电池正极材料

利用碳球作为模板,通过与异丙醇氧钒的溶剂热反应制备了五氧化二钒(V₂O₅)空心球。 采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对V₂O₅空心球进行了表征。 实验结果表明,V₂O₅空心球的直径约为1.5 μm,壁厚约100 nm。 将V₂O₅空心球作为镁二次电池的正极,在0.2 C充放电条件下,材料的首次放电比容量达140 mA·h/g,经20次循环后容量为110 mA·h/g。     

Li-ion charge storage performance of wood-derived carbon fibers@MnO as a battery anode

Wood-derived carbons have been demonstrated to have large specific capacities as the anode materials of lithium-ion batteries(LIBs). However, these carbons generally show low tap density and minor volumetric capacity because of high specific surface area and pore volume. Combination with metal oxide is one of the expected methods to alleviate the obstacles of wood-derived carbons. In this work, the composites of Mn O loaded wood-derived carbon fibers(CF@Mn O) were prepared via a simple and envir...     

MnO2/C复合材料的电化学电容特性研究

应用乙炔黑直接还原高锰酸钾制备MnO2/C复合材料.样品结构及性能由XRD和SEM表征.研究了MnO2/C电极(正极)在不同电解液中的法拉第"准电容行为",及其循环伏安、交流阻抗与恒电流充放电等性能.实验表明,MnO2/C复合材料具有良好的电化学电容特性.在1 mol/L的KOH电解液中和电流密度为5 mA/cm2下,MnO2/C复合材料的比电容量可达258 F/g,并表现出良好的循环性能.     

锂离子电池正极材料xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2的制备及表征

以过渡金属乙酸盐和乙酸锂为原料,柠檬酸为螯合剂,通过溶胶-凝胶法结合高温煅烧法制备了锂离子电池富锂锰基正极材料xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2,采用X射线衍射(XRD),扫描电子显微镜(SEM)和电化学性能测试对所得样品的结构,形貌及电化学性能进行了表征.结果表明:x=0.5时,在900°C下煅烧12h得到颗粒均匀细小的层状xLi2MnO3·(1-x)Li[Ni1/3Mn1/3Co1/3]O2材料,并具有良好的电化学性能,在室温下以20mA·g-1的电流密度充放电,2.0-4.8V电位范围内首次放电比容量高达260.0mAh·g-1,循环40次后放电比容量为244.7mAh·g-1,容量保持率为94.12%.     

二氧化锰微米球制备及其于超级电容器的应用

利用KMnO4氧化MnCO3微米球前躯体制备MnO2微米球.X射线衍射(XRD)、扫描电子显微镜(SEM)、循环伏安(CV)法等测试表明:该MnO2微米球由弱结晶α-MnO2构成,粒径为0.5~2μm.测试样品的MnO2微米球载量为5 mg.cm-2时,在2 mol.L-1(NH4)2SO4溶液中表现出良好的电容性能:其于2 mV.s-1的扫速下比电容达到了135.6 F.g-1;即使是100 mV.s-1的高扫速,比电容仍保持为118.8 F.g-1.500次循环过程中充放电效率保持在87.8%以上.第500次循环的比电容为110.5 F.g-1.     

γ-Ray Irradiation-Derived MnO/rGO Composites for High Performance Lithium Ion Batteries

We report a γ-ray irradiation reduction method to prepare MnO/reduced graphene oxide (rGO) nanocomposite for the anode of lithium ion batteries. γ-Ray irradiation provides a clean way to generate homogeneously dispersed MnO nanoparticles with finely tuned size on rGO surface without the use of surfactant. The MnO/rGO composite enables a fully charge/discharge in 2 min to gain a reversible specific capacity of 546 (mA·h)/g which is 45% higher than the theoretical value of commercial graphite anode.     

掺杂λ-MnO2的制备及其在KOH水溶液中的电化学性质

电化学性能;碱性溶液;掺杂λ-MnO2的制备及其在KOH水溶液中的电化学性质     

锂离子电池MnO/TiN负极研究

以乙酸锰和钛酸四丁酯为原料,柠檬酸为络合剂,采用溶胶-凝胶法制备钛酸锰（MnTiO3）粉体,而后将其粉体高温氨气氮化,可得到MnO/TiN复合材料. 使用X射线衍射（XRD）、X射线能量色散谱（EDS）和场发射扫描电子显微镜（FESEM）表征材料的物相结构与组分、观察其形貌. 采用循环伏安、恒流充放电和电化学阻抗方法测试电极电化学性能. 结果表明,MnO/TiN电极在100 mA?g-1和1 A?g-1倍率放电下,比容量分别为394 mAh?g-1和146 mAh?g-1,均高于单纯MnO电极比容量和倍率性能,这归因于复合材料中的TiN提供了导电网络,并有效地抑制了电极在充放电过程中的体积膨胀效应.     

Graphdiyne Hybrid Nanowall Arrays for High-capacity Aqueous Rechargeable Zinc Ion Battery

Development of aqueous rechargeable zinc ion battery is an important direction towards grid energy storage sought in various applications.At present,the efficient utilization of aqueous rechargeable zinc ion batteries has been seriously affected due to the defects nature of the cathode materials,such as poor capacity,limited rate performance,and limited cycle stability.Therefore,the search for high-performance cathode materials is a main challenge in this field.Herein,we in-situ prepared graphdiyne-wrapped K0.25·MnO2(K0.25·MnO2@GDY)hybrid nanowall arrays as the cathode of aqueous rechargeable zinc ion battery.The hybridnanowall arrays have obviously alleviated the pulverization and sluggish kinetic process of MnO2 cathode materials and shown high specific capacity(520 mA·h/g at a current density of 55 mA/g),which is near-full two-electron capacity.The high specific capacity was resulted from more than one Zn2+(de)intercalation process occurring per formula unit,in which we observed a structural evolution that partially stemmed from ion exchange between the intercalated K+and Zn2+ions during the discharge process.The present investigation not only provides a new material for the aqueous rechargeable Zn ion batteries,also contributes a novel route for the development of next generation aqueous rechargeable Zn ion batteries with high capacity.     

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium‐Ion Batteries

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO₃ precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li₂O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries.     

纳米MnO锂离子电池负极材料的制备与性能

以高锰酸钾和抗坏血酸合成的MnC₂O₄·2H₂O为前驱体, 通过固相烧结制备了纳米MnO材料. 分别采用X射线衍射(XRD)、扫描电子显微镜(SEM)和恒电流充放电技术考察了其晶相结构、颗粒形貌和电化学性能.分析结果表明, 该纳米MnO具有面心立方的岩盐结构, 结晶度良好. 其颗粒是由粒径为50-100 nm的一次颗粒结合而成的二次颗粒, 大小约为400-600 nm. 当充放电电流密度为46.3 mA·g^-1时, 纳米MnO的首次库仑效率可达68.9%, 可逆比容量为679.7 mAh·g^-1. 在141.1 mA·g^-1的电流密度下循环50圈后, 比容量由584.5mAh·g^-1降至581.5 mAh·g^-1, 容量保持率高达99.5%, 表现出优异的循环性能. 此外, 当电流密度增加到494.7 mA·g^-1 (~2C)时, 其比容量依然可达290 mAh·g^-1, 表现出较好的倍率性能和快速充放电能力. 因此, 纳米MnO具有比容量高、循环稳定、倍率性能好和安全环保等优点,是一种非常有前景的锂离子电池负极材料.     

二氧化锰/球形活性炭复合材料在有机系超级电容器中的应用

以Mn(NO3)2和中间相炭微球基球形活性炭（MSAC）为原料,采用热分解的方法成功制备了一种新型超级电容器用MnO2/MSAC球形复合材料。 通过X射线衍射、扫描电子显微镜和透射电子显微镜对比分析了该复合材料的结构和形貌,并采用循环伏安、恒流充放电、电化学阻抗（EIS）、循环充放电研究了电极的电化学性能。 结果表明,MnO2/MSAC球形复合物中的MnO2粒径为100~160 nm;在1 mol/L的LiPF6/(DMC+EC)（EC：乙烯碳酸酯;DMC：碳酸二甲酯) 有机电解液中MnO2/MSAC复合材料所组装的电容器的工作电压可达3.0 V,在0.002 A/cm2电流密度下,MnO2/MSAC球形复合材料的电容器和单纯MSAC材料的电容器的首次循环比容量分别为186和167 F/g,在循环过程中,MnO2/MSAC球形复合材料的电容器循环200次后充放电的库仑效率基本保持在95%以上。 此外,MnO2/MSAC球形复合材料的充放电曲线表现出典型的电容行为;循环伏安曲线也表现出良好矩型特征,同时具有较高的能量密度和良好的功率性能。     

TiO2@MWNTs纳米复合材料的制备及其储锂性能

以TiOSO4为钛源,多壁碳纳米管(MWNTs)为载体,溶剂热法制备了多壁碳纳米管/二氧化钛纳米复合材料(TiO2@MWNTs),并利用XRD,SEM,TEM,N2吸附-脱附和TG-DSC等测试手段对合成产物的结构和形貌进行表征,用恒流充放电测试研究TiO2@MWNTs纳米复合材料的储锂性能.N2吸附-脱附曲线和孔径分布曲线证实TiO2@MWNTs存在多级孔道结构以及较大的比表面积.电化学测试结果表明,与纯TiO2颗粒相比,TiO2@MWNTs纳米复合材料具有更好的容量保持率和倍率性能.在1 C倍率下,复合材料的可逆容量为200 mAh?g-1,循环100圈后容量仍达182 mAh?g-1,即使在10 C大倍率下,容量约为100 mAh?g-1左右.     

Functional Properties of Extruded Nanocomposites Based on Cassava Starch,Polyvinyl Alcohol and Montmorillonite

Summary: The objectives of this work were to produce expanded nanocomposites based on cassava starch, polyvinyl alcohol (PVA) and sodium montmorillonite (Na-MMT). The nanocomposites were characterized according to their expansion index (EI), density, water absorption capacity (WAC), mechanical properties and crystallinity. The nanocomposites were prepared in a single-screw extruder using different starch contents (97.6–55.2 g/100 g formulation), PVA (0–40 g/100 g formulation) and Na-MMT (0–4.8 g/100 g formulation). Glycerol (20 g/100 g formulation) was used as plasticizer. The addition of Na-MMT and PVA resulted in an increase of EI and mechanical strength of the foams. Na-MMT and PVA addition resulted in less WAC of the samples. The studied processing conditions resulted in a good nanoclay dispersion, leading to the formation of an intercalated structure.     

MnO@Carbon Core–Shell Nanowires as Stable High‐Performance Anodes for Lithium‐Ion Batteries

A facile method is presented for the large‐scale preparation of rationally designed mesocrystalline MnO@carbon core–shell nanowires with a jointed appearance. The nanostructures have a unique arrangement of internally encapsulated highly oriented and interconnected MnO nanorods and graphitized carbon layers forming an external coating. Based on a comparison and analysis of the crystal structures of MnOOH, Mn₂O₃, and MnO@C, we propose a sequential topotactic transformation of the corresponding precursors to the products. Very interestingly, the individual mesoporous single‐crystalline MnO nanorods are strongly interconnected and maintain the same crystallographic orientation, which is a typical feature of mesocrystals. When tested for their applicability to Li‐ion batteries (LIB), the MnO@carbon core–shell nanowires showed excellent capacity retention, superior cycling performance, and high rate capability. Specifically, the MnO@carbon core–shell nanostructures could deliver reversible capacities as high as 801 mA h g^?1 at a high current density of 500 mA g^?1, with excellent electrochemical stability after testing over 200 cycles, indicating their potential application in LIBs. The remarkable electrochemical performance can mainly be attributed to the highly uniform carbon layer around the MnO nanowires, which is not only effective in buffering the structural strain and volume variations of anodes during repeated electrochemical reactions, but also greatly enhances the conductivity of the electrode material. Our results confirm the feasibility of using these rationally designed composite materials for practical applications. The present strategy is simple but very effective, and appears to be sufficiently versatile to be extended to other high‐capacity electrode materials with large volume variations and low electrical conductivities.     

纳米电极材料的制备及其电化学性质研究(Ⅲ)——微乳液中通氧气制备MnO_2及其性能

本文采用锰盐微乳液中通氧气法成功制备了超细粉末ＭｎＯ２,对所得样品进行了化学分析,ＸＲＤ,ＴＥＭ测试,证明为γ ＭｎＯ２,平均粒径在纳米级范围内．再经恒电流放电,循环伏安,分形维数,交流阻抗等测试,发现在适当制备条件下所得纳米ＭｎＯ２具有良好的放电性能,并对此作了初步的理论探讨