Direct soft-chemical synthesis of chalcogen-doped manganese oxide 1D nanostructures: influence of chalcogen doping on electrode performance

We have developed a direct nonhydrothermal route to nanostructured chalcogen-doped manganese oxides; K(x)MnO(2)Q(y) (Q = S, Se, and Te). According to combinative diffraction and microscopic analyses, the S- and Se-doped manganese oxides exhibit 1D nanowire-type morphology with layered delta-MnO(2)- and alpha-MnO(2)-structures, respectively, whereas the Te-doped compound consists of 3D nanospheres that are amorphous according to X-ray diffraction. X-ray absorption and X-ray photoelectron spectroscopy analyses clearly demonstrate that the doped chalcogen ions exist in the form of hexavalent chalcogenate clusters mainly on the sample surface or grain boundary. According to electrochemical and ex situ X-ray absorption spectroscopy investigations, the Se-doped manganate nanowires show higher structural stability and better electrode performance with excellent rate characteristics compared to the S-/Te-doped and undoped manganate nanostructures. This is attributed to the presence of chemically stable SeO4(2-) species, leading to enhanced stability of the manganate lattice through the prevention of structural deformation during cycling and/or to the improvement of Li(+) ion transport through the maintenance of intercrystallite voids. Based on the present experimental findings, we are able to conclude that the present one-pot soft-chemical route with chalcogen dopants can provide a simple method not only to economically synthesize 1D nanostructured manganese oxides but also to finely control their electrode performance, crystal structure and morphology, and lattice stability.     

Effect of copper doping on the crystal structure and morphology of 1D nanostructured manganese oxides

We have tried to control the aspect ratio and physicochemical properties of 1D nanostructured manganese oxides through copper doping. Copper-doped manganese oxide nanostructures have been synthesized by one-pot hydrothermal treatment for the mixed solution of permanganate anions and copper cations. According to powder X-ray diffraction and electron microscopic analyses, all the present materials commonly crystallize with alpha-MnO2-type structure but their aspect ratio decreases significantly with increasing the content of copper. Such a variation of crystallite dimension is attributable to the limitation of crystal growth by the incorporation of copper ions. X-ray absorption spectroscopic studies at Mn K- and Cu K-edges clearly demonstrate that the average oxidation state of manganese ions is increased by the substitution of divalent copper ions. Electrochemical measurements reveal the improvement of the electrode performance of nanostructured manganate upon copper doping, which can be interpreted as a result of the decrease of aspect ratio and the increase of Mn valence state. From the present experimental findings, it becomes certain that the present Cu doping method can provide an effective way of controlling the crystal dimension and electrochemical property of 1D nanostructured manganese oxide.     

富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的Zn2+掺杂改性

采用高温固相合成法制备富锂锰基正极材料Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54-x)Zn_xO_2(x=0,0.03,0.06,0.10),Zn~(2+)掺杂对Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2的表面特性和电化学性能都有影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼光谱分析、充放电测试、倍率特性测试、循环性能测试,分析了该合成材料的晶体结构、形貌特征、微观结构和电化学性能。富锂锰基正极材料为a-NaFeO_2层状结构,R-3m空间群,结晶度高,结构稳定性好,其中Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.48)Zn_(0.06)O_2的电化学性能较好。掺杂Zn~(2+)可以提高富锂锰基正极材料的充放电比容量、倍率性能、循环性能等电化学性能。     

基于从头算法的TM金属共掺杂的ZnO基稀磁半导体的磁性研究(英文)

本文采用从头计算的方法研究了基于过渡性金属共掺杂Ⅱ-Ⅵ族稀释半导体的磁性和电子结构.并系统的研究了氧化锌基的稀释半导体铁磁态的稳定性和对其材料设计.在所有的共掺杂体系中,发现(Mn,Co),(Co,Ni)和(Mn,Ni)共掺杂体系是铁磁态的,而(Fe,Ni)共掺杂体系是自旋玻璃态.另一方面,Fe-,Co-和Ni掺杂ZnO基系统的稳态是铁磁态.同时,本文研究了ZnO基稀释半导体的载流子传导铁磁性,计算分析了电子态密度,铁磁态的稳定性.结合双交换和超交换理论解释共掺杂稀释半导体的磁性机理.     

Nano/micro lithium transitionmetal (Fe, Mn, Co and Ni) silicate cathode materials for lithium ion batteries

Lithium transitionmetal (Fe, Mn, Co, Ni) silicate cathode materials are new promising substituting cathode materials for lithium ion batteries. They had caught the researchers' eyes in the past several years. Nowadays, there are growing interests for silicate cathode materials in the field of lithium ion batteries. Among the silicate cathode materials, Li2FeSiO4 is the most promising cathode materials because of its high structure stability, high reversible capacity, high electronic conductivity and the abundant resource of iron and silicon. Although Li2MnSiO4 and Li2CoSiO4 have much higher theoretic specific capacity than Li2FeSiO4, they all have inferior electrochemical behaviours due to different reasons. There are only calculation results about Li2NiSiO4 till now. This brief critical review firstly discussed some papers about the first-principle calculation of Li2MSiO4 (M=Fe, Mn, Co Ni), and then collects and discusses relevant papers and recent patents about the fabrication, structure, particle size and electrochemical performance of nano/micro Li2MSiO4 (M=Fe, Mn, Co Ni) and their composites. Finally, the future challenges of Li2FeSiO4 are also discussed.     

锂离子电池正极梯度材料的制备及电性能研究

采用金属离子混合硫酸盐溶液分次共沉淀法制备前躯体,混锂后通过高温固相反应得到具有镍、钴和锰浓度梯度的层状LiNi0.56Co0.22Mn0.22O2锂离子电池正极材料。通过x射线衍射(XRD)、扫描电子显微镜(SEM)及恒电流充放电测试对合成的材料进行了表征。结果表明,750～900℃焙烧15h下合成的产物均具有典型的α-NaFeO2型层状结构特征,晶型结构完整,粒度均匀。800℃合成的正极材料具有较好的电化学性能。在充放电倍率0.4C、2.75-4.2V电压范围内,材料的首次充放电比容量分别为170.0mAh/g和131.8mAh/g,放电效率为77.5%;第51次循环的充放电比容量分别为131.3mAh/g和130.5mAh/g,放电效率为99.4%,容量保持率达到99.0%。     

锂离子电池正极材料LiM0.1Ni0.4Mn1.5O4(M:Co,Cr,Fe)纳米纤维的制备与电化学性能

利用高压静电纺丝技术与溶胶凝胶法相结合制备出了锂离子电池正极材料LiM_(0.1)Ni_(0.4)Mn_(1.5)O_4(M:Co,Cr,Fe)纳米纤维。采用X射线衍射(XRD)、场发射扫描电镜(FESEM)对材料的晶体结构和表面形貌进行了表征,并采用恒流充放电手段研究了材料在室温下的循环稳定性和倍率特性。结果表明:LiFe_(0.1)Ni_(0.4)Mn_(1.5)O_4材料以0.5C充放电循环100周后容量保持率高达95.5%,显示了良好的循环稳定性;而LiCr_(0.1)Ni_(0.4)Mn_(1.5)O_4材料以10C放电比容量仍高达120mAh/g,显示出了极好的倍率特性。     

Über die systeme BaRu1−xMxO3−y (M = Rh,Ir, Mn,Fe, Co,Ni)

In the systems BaRu_1?xM_xO_3?y (M = Rh, Ir, Mn, Fe, Co, Ni) several perovskite stacking polytypes are present. The influence of the crystal structure and Ru/M-ratio on the electrical conductivity and catalytic activity is investigated.     

Key Properties of Ni?Mn?Ga Based Single Crystals Grown with the SLARE Technique

Magnetic shape memory alloys (MSMAs), exhibit large strains and hence are materials, which could substitute giant magnetostrictive and piezoelectrical materials in actuating devices. The actuation stress needed to induce the strain is much lower than in other actuator materials. Since the strain can be induced without phase transformation by a magnetic field, the development of actuators with high working frequencies is possible. However, for reasonable applications, large strains have to be induced with small magnetic fields. Up to now repeatable magnetically induced strains of 5–10% in magnetic fields of less than 500 mT have been achieved only in single crystals. The production of Ni? Mn? Ga based single crystals is difficult and time consuming. The crystal quality is affected by porosity and impurities. With the Bridgeman based method called Slag Remelting and Encapsulation (SLARE) single crystalline ingots of Ni? Mn? Ga, Ni? Mn? Ga? Fe, and Ni? Mn? Ga? Co of high quality were grown and characterized. The results show that MSMA properties depend on the position within the single crystalline rods due to a composition gradient. The influence of surface treatment demonstrates that the decrease of surface roughness leads to a decrease of twinning stress. MSMAs with twinning stresses above 1 MPa show a magnetic field induced strain (MFIS) when tilting is not restricted by constraints. Softer samples can adapt to constraints much better and show large MFIS. Substituting Ni by Fe and Co, shifted the phase transitions successfully to higher temperatures. Ni? Mn? Ga alloyed with up to 6 at.% Co showed three different martensite structures: a non‐modulated tetragonal structure, a modulated tetragonal structure, showing the same behavior as Ni? Mn? Ga with identical structures and a non‐modulated orthorhombic structure with a stress–strain‐behavior explainable by the double twinning mechanism.     

Crystal structure and formation mechanism of the secondary phase in Heusler Ni-Mn-Sn-Co materials

In the present work,crystal structure and formation mechanism of the secondary phase in Heusler NiMn-Sn-Co materials were investigated using X-ray diffraction,scanning/transmission electron microscopy and selected-area electron diffraction techniques.Experimental results showed that the secondary phase presented in both Ni_(44.1)Mn_(35.1)Sn_(10.8)Co_(10) as-cast bulk alloy and melt-spun ribbon,possessing a face-centered cubic(fcc) Ni_(17)Sn_3-type structure.The secondary phase in the as-cast bulk alloy was resulted from a eutectic reaction after the formation of a primary dendritic β phase during cooling.However in the melt-spun rapidly solidified ribbon,the secondary phase was largely suppressed as nano-precipitates distributed along the grain boundaries,which was attributed to a divorced eutectic reaction.The secondary phase exhibited partial amorphous state due to high local cooling rate.     

Li(Ni,Co,Mn)O_2合成过程中的结构变化

根据Li(Ni,Co,Mn)O2晶体中Li+和Ni2+的阳离子混排占位模型进行模拟计算,建立了(I003/I104)1/2、(I101/I012)1/2(、I101/I104)1/2等特征衍射线强度比与混排占位参数x的线性方程式。结合实验测得的X-射线衍射谱和混排占位模型研究了Li(Ni,Co,Mn)O2合成过程中的结构演变过程。     

Novel active heterogeneous Fenton system based on Fe3-xMxO4 (Fe, Co, Mn, Ni): the role of M2+ species on the reactivity towards H2O2 reactions

In this work, the effect of incorporation of M2+ species, i.e. Co2+, Mn2+ and Ni2+, into the magnetite structure to increase the reactivity towards H2O2 reactions was investigated. The following magnetites Fe3-xMnxO4, Fe3-xCoxO4 and Fe3-xNixO4 and the iron oxides Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 were prepared and characterized by M?ssbauer spectroscopy, XRD, BET surface area, magnetization and chemical analyses. The obtained results showed that the M2+ species at the octahedral site in the magnetite strongly affects the reactivity towards H2O2, i.e. (i) the peroxide decomposition to O2 and (ii) the oxidation of organic molecules, such as the dye methylene blue and chlorobenzene in aqueous medium. Experiments with maghemite, gamma-Fe2O3 and hematite, alpha-Fe2O3, showed very low activities compared to Fe3O4, suggesting that the presence of Fe2+ in the oxide plays an important role for the activation of H2O2. The presence of Co or Mn in the magnetite structure produced a remarkable increase in the reactivity, whereas Ni inhibited the H2O2 reactions. The obtained results suggest a surface initiated reaction involving Msurf2+ (Fe, Co or Mn), producing HO radicals, which can lead to two competitive reactions, i.e. the decomposition of H2O2 or the oxidation of organics present in the aqueous medium. The unique effect of Co and Mn is discussed in terms of the thermodynamically favorable Cosurf3+ and Mnsurf3+ reduction by Femagnetite2+ regenerating the active species M2+.     

过渡金属离子掺杂对磷酸铁锂性能的影响

以碳酸锂、草酸亚铁、磷酸二氢铵、葡萄糖为原料,添加不同的过渡金属乙酸盐(乙酸锰、乙酸钴、乙酸镍、乙酸锌),在氩气保护下采用高温固相法制备LiFePO4/C复合材料.采用X射线衍射、扫描电子显微镜、同步热分析、恒电流充放电、电化学阻抗、循环伏安等方法研究掺杂金属离子及掺杂量对LiFePO4/C晶体结构和电化学性能的影响.结果表明,LiFe0.9M0.1PO4/C(M=Mn、Co、Ni、Zn)样品的晶体结构均与橄榄石型LiFePO4相同.掺杂过渡金属阳离子可以提高LiFeP04/C的还原电位,降低氧化电位,缩小氧化还原峰间距,提高化学反应的可逆性.掺杂后的样品在5C下的放电性能较好,以LiFe0.9Ni0.1PO4/C的放电容量最高,达到89 mAh/g.     

Electrochemical and thermal behaviour of Li[Li(x)(Ni0.3Co0.1Mn0.6)1 - x]O2 (x = 0.09, 0.11) cathode Materials for lithium rechargeable batteries

High rate capable Mn-rich layered Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, 0.11) cathode materials that are fully charged are investigated with respect to stability. Differential scanning calorimetry is used to determine the thermal stability of cathode material compositions together with PVdF binder and a conductive agent by heating from 30 degrees C to 400 degrees C at 10 degrees C/min. In the Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, x = 0.11) cathode materials, the exothermic reaction started at 100 degrees C. Due to thermal runway, a sharp peak was observed at 279.25 degrees C for the material of x = 0.09 with exothermic heat generation of 168.4 J/g. For the Mn-rich cathode material, where x = 0.11, two relatively smaller peaks appeared at 250.72 degrees C and 268.60 degrees C with heat evolution of 71.49 J/g and 93.67 J/g, respectively. These layered cathode materials are thermally stable. The x = 0.09 composition shows huge heat flow occurrence when compared to the x = 0.11. It is concluded from a heat generation analysis that the two Mn-rich cathode materials are thermally stable for lithium rechargeable batteries.     

LiNi₁/₃Co₁/₃Mn₁/₃O₂-graphene composite as a promising cathode for lithium-ion batteries

The use of graphene as a conductive additive to enhance the discharge capacity and rate capability of LiNi(1/3)Co(1/3)Mn(1/3)O(2) electrode material has been demonstrated. LiNi(1/3)Co(1/3)Mn(1/3)O(2) and its composite with graphene (90:10 wt %) were prepared by microemulsion and ball-milling techniques, respectively. The structural and morphological features of the prepared materials were investigated with powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Characterization techniques depict single-phase LiNi(1/3)Co(1/3)Mn(1/3)O(2) with particle sizes in the range of 220-280 nm. Electrochemical studies on LiNi(1/3)Co(1/3)Mn(1/3)O(2) and LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene were conducted using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy methods by constructing a lithium half-cell. Cyclic voltammograms show the well-defined redox peaks corresponding to Ni(2+)/Ni(4+). Charge-discharge tests were performed at different C rates: 0.05, 1, and 5 between 2.5 and 4.4 V. The results indicate the better electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite in terms of high discharge capacity (188 mAh/g), good rate capability, and good cycling performance compared to LiNi(1/3)Mn(1/3)Co(1/3)O(2). The improved electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite is attributed to a decrease in the charge-transfer resistance.     

阴离子（NO3－／Cl －／SO2－4）对 Ni（OH）2晶型及其结构稳定性的影响

采用超声波辅助沉淀法分别在单元掺杂、二元掺杂和不掺杂三种情况下制备了三种不同镍源的纳米氢氧化镍,研究三种阴离子（NO3－,Cl－,SO2－4）对产物晶相结构及稳定性的影响。结果表明：未掺杂时,半径较大的SO2－4离子有利于α‐Ni（OH）2的形成;在单掺杂Co（Ni2＋∶Co2＋＝1∶0．20）时,NO3－离子不仅有利于α‐Ni（OH）2的形成,而且可以使α‐Ni（OH）2在碱液中保持较高的稳定性;当复合掺杂Co／Cu（Ni2＋∶Co2＋∶Cu2＋＝1∶0．15∶0．05）时,三种镍源制得的样品均为纯α‐Ni（OH）2结构,但以Ni（NO3）2为镍源的α‐Ni（OH）2在碱液中结构稳定性较高,NiCl2次之,NiSO4较差。可见,α‐Ni（OH）2结构及稳定性既与掺杂情况有关,也与阴离子密切相关。     

Study on adsorption of Co(II) and Ni(II) onto mesoporous Ti-containing MCM-48

Ti-containing MCM-48 (Ti-MCM-48) material with mesoporous structure was synthesized and characterized, and the absorption processes of Co(II) and Ni(II) on the material were investigated in detail in the present study. The Ti- MCM-48 was synthesized by hydrothermal reaction and characterized by XRD, FT-IR and nitrogen sorption methods. Optimum pH value for maximum adsorption rate is 8.0, and the saturated adsorption capacities of Ti-MCM-48 for Co(II) and Ni(II) are 9.870 and 22.94 mg g(-1) respectively, which are greater than those of the reported materials Adsorption isotherms of Co(II) and Ni(II) on Ti-MCM-48 accord well with the Langmuir adsorption models. Kinetic data of adsorption reactions and the adsorption equilibrium parameters were also determined, and the obtained data correlated linearly with the pseudo-second order equation.     

新一代高比能量锂离子电池富锂氧化物正极材料的研究进展

富锂氧化物xLi_2MnO_3·(1-x)LiMO_2(M为Co、Ni、Mn等)的比容量可达250~300mAh/g,是高比能量锂离子电池正极材料的首选之一。介绍了材料的晶体结构、嵌/脱锂机制和充放电过程中发生的结构相变,分析讨论了材料出现首次不可逆容量大、电压和容量衰减快、倍率性能和低温性能较差等问题的原因,阐述了材料的合成方法及改性技术,如表面包覆、离子掺杂、形貌和晶面调控以及合成层状相-尖晶石相共生结构的异质材料等。最后从基础研究和应用研究两个方面展望了富锂氧化物材料的发展前景。     

Characterization of Co-doped birnessites and application for removal of lead and arsenite

Nanostructured Co-doped birnessites were successfully synthesized, and their application for the removal of Pb(2+) and As(III) from aquatic systems was investigated. Powder X-ray diffraction, chemical analysis, nitrogen physical adsorption, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure, chemical composition, micromorphologies and surface properties of the birnessites. Doping cobalt into the layer of birnessite had little effect on its crystal structure and micromorphology. Both chemical and XPS analyses showed that the manganese average oxidation state (Mn AOS) decreased after cobalt doping. The Co dopant existed mainly in the form of Co(III)OOH in the birnessite structure. Part of the doped Co(3+) substituted for Mn(4+), resulting in the gain of negative charge of the layer and an increase in the content of the hydroxyl group, which accounted for the improved Pb(2+) adsorption capacity. The maximum capacity of Pb(2+) adsorption on HB, CoB5, CoB10 and CoB20 was 2538 mmol kg(-1), 2798 mmol kg(-1), 2932 mmol kg(-1) and 3146 mmol kg(-1), respectively. The total As(III) removal from solution was 94.30% for CoB5 and 100% for both CoB10 and CoB20, compared to 92.03% for undoped HB, by oxidation, adsorption and fixation, simultaneously.     

掺钴MnO2电极的电化学电容行为研究

采用化学共沉淀法制备了超级电容器电极材料化学掺杂Co的MnO2电极,借助XRD测试对电极材料进行了物理结构表征,表明掺Co量影响材料的晶体结构和活性。电化学测试结果得出化学掺杂的配比对电化学性能影响很大,掺杂量为n(Co)：n(Co Mn)大于或小于0．1时,其循环伏安、充放电和电容特性较差。而适量的掺入Co,改善了电极的电容性能,降低了电极内阻,提高了活性物质的利用率,并使得电极能够在大电流下进行充放电。经1000次循环,适量掺杂的MnO2电极比未掺杂的MnO2电极具有更高的电容性能,掺杂的MnO2电极循环性能相对较差,但是其比电容仍然大干未掺杂MnO2电极。