Excitation energy dependence for the Li 1s X-ray photoelectron spectra of LiMn2O4.

The Li 1s XPS (X-ray Photoelectron Spectroscopy) spectra of LiMn2O4, which is one of the major positive-electrode materials in lithium-ion rechargeable batteries, and MnO2 as a reference material, were measured by a laboratory-type XPS spectrometer. The Li 1s peak was not observed in the spectra excited by the Mg Kalpha line (1253.6 eV), because the Li 1s peak overlapped the background of the Mn 3p peak of LiMn2O4. The photoionization cross section of Mn 3p was larger than that of Li 1s for Mg Kalpha excitation. Therefore, the XPS measurement of LiMn2O4 by soft X-ray synchrotron excitation was carried out at beamline BL-7B on NewSUBARU synchrotron facility. Excitation energies of 110, 120, 130, 140, 150 and 151.4 eV were selected. The Li 1s peak was clearly observed in these XPS spectra. In order to investigate the excitation energy dependence, the area ratio of the Li 1s and Mn 3p peaks in the XPS spectra was plotted against the excitation energy. As a result, when the excitation energy was 110 eV, the area ratio had the maximum value.     

Effect of silver coating on electrochemical performance of 0.5Li2MnO3.0.5 LiMn1/3Ni1/3Co1/3O2 cathode material for lithium-ion batteries

Journal of Solid State Electrochemistry - In this work, a Li-rich layered 0.5Li2MnO3.0.5LiMn1/3Ni1/3Co1/3O2 (LMNCO) pristine cathode material synthesized with a glycine-nitrate combustion method is...     

A time-resolved quadrupole mass spectrometric study on 355 nm laser ablated species ejected from LiMn2O4

Mass, velocity and angle distributions of the ablated species generated from 355 nm pulsed laser ablation of a LiMn2O4 target were investigated with an angle- and time-resolved mass spectrometric technique. Both neutral and ionic species of Li, O, LiO, LiO2, Mn, Li2, Li4, Li6, LiMn, MnO and MnO2 were observed at the laser fluence of 0.8 J · cm-2. The yield and variety of the ablated species increase with increasing the laser fluence. The time-of-flight spectra of ablated species can be fitted by a Maxwell-Boltzmann distribution with a center-of-mass velocity. There exist laser fluence thresholds for the ablated LiMn, Li2O and LiO2 species, and the fluence threshold of ionic species is higher than that of neutral species. The angular distributions of the ionic and neutral ablated species can be simulated by a cosnθor a bicosine function αcosθ+(1- α)cos"θ. In addition, the ablation mechanism of LiMn2O4 by a 355 nm pulsed laser is discussed.     

长寿命、高倍率(Li4Ti5O12-AC)/( LiMn2O4-AC)电池电容的制备及性能研究

以商业微米级锰酸锂(LiMn2O4)为正极,钛酸锂(Li4Ti5O12)为负极,分别与商业活性炭(AC)复合,组装成软包装电池电容样品并进行电化学测试。测试结果表明：当样品正负极均复合AC时,其电化学性能要优于只有正极复合AC和未复合AC的样品。其中,正负极活性炭复合比例为5 wt.%,负极与正极的理论容量比(N/P)为1.01时,电池电容样品拥有良好的倍率性能,且其在0.5 C时的放电比容量为56.4 mAh/g,5 C时的容量保持率为0.5 C的72.2%。此外,与未复合AC的样品相比,单体在5 C倍率下经2000次循环后的容量保持率仍有77.5%,远高于前者的30.4%。     

合成条件对尖晶石LiMn_2O_4的电化学性能的影响

以Li2 CO3、LiOH、LiNO3以及电解MnO2 (EMD)作原料 ,用固相反应法合成了尖晶石LiMn2 O4 .结果表明 ,反应物种类及合成条件对LiMn2 O4 的电化学性质有很大的影响 .其中以LiNO3和EMD为合成原料制得的LiMn2 O4 性能最佳 .其制备条件分两步 :先在 2 80℃加热 6h ,使熔融的LiNO3渗入EMD微孔 ,然后在 75 0℃下焙烧合成     

High-energy 'composite' layered manganese-rich cathode materials via controlling Li2MnO3 phase activation for lithium-ion batteries

The 'composite' layered materials for lithium-ion batteries have recently attracted great attention owing to their large discharge capacities. Here, the 0.5Li(2)MnO(3)·0.5LiMn(0.42)Ni(0.42)Co(0.16)O(2)'composite' layered manganese-rich material is prepared and characterized by the synchrotron X-ray powder diffraction (SXPD). The relationship between its electrochemical performance and its 'composite' components, the Li(2)MnO(3) phase activation process during cycling and the cycle stability of this material at room temperature are elucidated based on its kinetic controlled electrochemical properties, dQ/dV curves and Raman scattering spectroscopies associated with different initial charge-discharge current densities (5 mA g(-1), 20 mA g(-1) and 50 mA g(-1)), cut-off voltages (4.6 V and 4.8 V) and cycle numbers (50 cycles and 150 cycles). Furthermore, its reaction pathways are tracked via a firstly introduced integrated compositional phase diagram of four components, Li(2)MnO(3), LiMn(0.42)Ni(0.42)Co(0.16)O(2), MO(2) (M = Mn(1-α-β)Ni(α)Co(β); 0 ≤α≤ 5/12, 0 ≤β≤ 1/6) and LiMnO(2), which turns out to be a very important guiding tool for understanding and utilizing this 'composite' material.     

Enhanced high power and long life performance of spinel LiMn2O4 with Li2MnO3 coating for lithium-ion batteries

Journal of Solid State Electrochemistry - Li2MnO3 coated spinel lithium manganese oxide (LiMn2O4) materials have been successfully synthesized by a sol-gel method. Scanning electron microscopy...     

锂离子交换剂制备及交换反应动力学

通过XRD分析、Li＋抽出率βLi及Mn2＋溶出率γMn的计算，考察了不同焙烧温度及抽锂剂对前驱体锂锰氧化物LiMn2O4结构及稳定性的影响.结果表明, 750 ℃下焙烧2 h，并使用过硫酸铵(NH4)2S2O8作抽锂剂，制备的Li＋交换剂MnO2(Li)对Li＋的交换容量αLi较大.另外，通过Li＋在固液两相间分配系数的测定及交换反应动力学实验，对离子交换反应机理进行了研究，并建立了有限浴条件下MnO2(Li)离子交换反应动力学模型.结果表明,该离子交换过程近似符合颗粒扩散控制；交换反应主要发生在交换剂颗粒外层；提出的动力学模型与实验结果符合较好.     

锂嵌脱化合物LiMn2O4的微波烧结研究

本文用微波烧结法合成锂嵌脱材料ＬｉＭｎ２Ｏ４，研究了微波烧结功率，时间的固态产物相的影响，对ＬｉＭｎ２Ｏ４单相多晶粉末进行了ＸＲＤ，ＩＲＭ，ＸＰＳ，等离子体发射光谱及氧化还原等测试。     

Sc3+ 掺杂的尖晶石型LiMn2 O4 正极材料制备及性质

A series of Sc3+-doped spinel lithium manganese oxides Li1+xScyMn2-yO4（y=0.01, 0.02, 0.06, and 0.10）were synthesized by solid state reaction using LiOH·H2O, MnO2, and Sc2O3 as starting materials. The results of powder X-ray diffraction indicated that the doped Li1+xScyMn2-yO4 maintain the cubic structure of spinel phase Fd3m. The electrochemical properties were characterized by electrochemical methods. The initial discharge capacity reached 135 mAh/g and the capacity fading rate was less than 2% after 40 cycles. The spinel phase was well preserved after 40 cycles. The doping of Sc3+ effectively improved the cycleability of spinels, and was a promising way for the improvement of spinel LiMn2O4 cathode materials.     

锂离子筛的制备及其交换性能研究

用浓度为0.5mol/L的盐酸对高温固相合成的前体LiMn2O4进行酸洗脱锂,制得锂离子筛HMn2O4,并在不同pH值和温度下进行了Li 交换性能的研究,同时运用XRD和TEM进行了相应表征。结果表明,锂离子筛吸附交换前后晶体结构只发生了细微变化,但都仍为尖晶石型结构;交换反应在前10min速率最快,约20min就趋于平衡;Li 交换总量随pH值增大而升高,其中pH=7时交换容量为18.5526mg/g;Li 交换量和交换选择性随温度的升高而显著增强。     

工艺参数对o-LiMnO2相纯度及Li1.6Mn1.6O4合成的影响及作用（英文）

以MnSO4,KMnO4及LiOH为原料,经水热处理后得到LiMnO2,再由固相焙烧得到尖晶石相Li1.6Mn1.6O4,酸洗处理后得到锂离子筛。研究了水热温度,氧气和MnO4-/Mn2+的物质的量之比(nMnO4∶nMn^2+)对所得LiMnO2的组成及相应前驱体Li1.6Mn1.6O4酸处理中Mn溶损率的影响。开路电势测量及化学分析表明,氧气会参与反应。若按照理论氧化剂用量nMonO4∶nMn^2+=1∶4进行水热反应会导致杂质Li2MnO3和LiMn2O4的生成。若控制水热温度为160℃,nMnO4∶nMn^2+=1∶6时可得到纯相正交LiMnO2(o-LiMnO2)。所得离子筛在高镁锂比盐湖卤水中Li+吸附容量可达42.87 mg·g^-1,且对Li+具有优异的选择吸附性并遵循化学吸附过程。经过5个循环后吸附容量保持在37.21 mg·g^-1,锰溶损率降至0.34%。     

Cu-Sn-P-LiMn2O4纳米复合材料镀层的XPS和AES研究

采用化学复合镀技术，在Q₂₃₅碳钢片表面制备了Cu-Sn-P-LiMn₂O₄纳米复合材料镀层。用扫描电子显微镜(SEM)观察外貌；称重法测定厚度；通过5% NaCl溶液、1% H₂S气体加速腐蚀试验、抗粘性试验及室温氧化试验等多种手段测定其性能。用X-射线光电子能谱(XPS)及俄歇电子能谱(AES)测定其价态及组成。结果表明:Cu-Sn-P-LiMn₂O₄纳米复合材料镀层的性     

正尖晶石LiMn_2O_4电化学性能研究

采用高温固相反应合成了尖晶石LiMn2 O4 锂离子电池正极材料 ,并对其性能进行研究 .综合考察了影响材料电化学性能的主要因素 ,诸如原材料的选择、合成温度、Li/Mn比以及添加金属元素Co等 .研究了材料在高温下的电化学性能和影响因素 ,并分析了LiMn2 O4 在电解质中的溶解和引起容量衰减的原因     

Short- and long-range order in the positive electrode material, Li(NiMn)0.5O2: a joint X-ray and neutron diffraction, pair distribution function analysis and NMR study

The local environments and short-range ordering of LiNi(0.5)Mn(0.5)O(2), a potential Li-ion battery positive electrode material, were investigated by using a combination of X-ray and neutron diffraction and isotopic substitution (NDIS) techniques, (6)Li Magic Angle Spinning (MAS) NMR spectroscopy, and for the first time, X-ray and neutron Pair Distribution Function (PDF) analysis, associated with Reverse Monte Carlo (RMC) calculations. Three samples were studied: (6)Li(NiMn)(0.5)O(2), (7)Li(NiMn)(0.5)O(2), and (7)Li(NiMn)(0.5)O(2) enriched with (62)Ni (denoted as (7)Li(ZERO)Ni(0.5)Mn(0.5)O(2)), so that the resulting scattering length of Ni atoms is null. LiNi(0.5)Mn(0.5)O(2) adopts the LiCoO(2) structure (space group Rm) and comprises separate lithium layers, transition metal layers (Ni, Mn), and oxygen layers. NMR experiments and Rietveld refinements show that there is approximately 10% of Ni/Li site exchange between the Li and transition metal layers. PDF analysis of the neutron data revealed considerable local distortions in the layers that were not captured in the Rietveld refinements performed using the Bragg diffraction data and the LiCoO(2) structure, resulting in different M-O bond lengths of 1.93 and 2.07 Angstroms for Mn-O and Ni/Li-O, respectively. Large clusters of 2400-3456 atoms were built to investigate cation ordering. The RMC method was then used to improve the fit between the calculated model and experimental PDF data. Both NMR and RMC results were consistent with a nonrandom distribution of Ni, Mn, and Li cations in the transition metal layers; both the Ni and Li atoms are, on average, close to more Mn ions than predicted based on a random distribution of these ions in the transition metal layers. Constraints from both experimental methods showed the presence of short-range order in the transition metal layers comprising LiMn(6) and LiMn(5)Ni clusters combined with Ni and Mn contacts resembling those found in the so-called "flower structure" or structures derived from ordered honeycomb arrays.     

The effects of crystal structure of the precursor MnO2 on electrochemical properties of spinel LiMn2O4

Journal of Solid State Electrochemistry - The spinel LiMn2O4 samples for lithium-ion battery have been synthesized through one-step solid-state method using four different polymorphs of MnO2, e.g.,...     

尖晶石LiMn2O4锂充放电池的电化学研究

本文报导尖晶石型ＬｉＭｎ２Ｏ４化合物的制备方法，用循环伏安法和交流阻抗技术研究了Ｌｉ／有机电解液／ＬｉＭｎ２Ｏ４电池的电化学行为，用分形理论首次考察和进一步讨论电极材料的阻抗行为随锂离子嵌入或脱嵌电极时的变化。     

Li_3PO_4包覆LiMn_2O_4正极材料的结构表征和电化学性能

采用共沉淀法在尖晶石LiMn2O4颗粒表面包覆Li3PO4.XRD、SEM研究结果表明,包覆后的材料仍为尖晶石结构,粒径均匀.电化学性能测试表明,Li3PO4包覆层的存在,减少了正极材料与电解液的直接接触,抑制了高温下电解液对LiMn2O4材料的侵蚀,从而有效改善了高温下材料的循环性能.在40℃时,包覆样品的比容量衰减率都低于未包覆样品,其中包覆1%Li3PO4的样品的初始比容量为110.4mAh/g,50次循环后比容量为84.1mAh/g.     

锂离子电池LiMn2O4薄膜电极的制备研究进展

尖晶石ＬｉＭｎ２Ｏ４是最有希望替ＬｉＣｏＯ２的新一代锂离子电池阴极材料。高能、轻量、超薄将是未来锂离子电池一个十分重要的发展方向。本文对尖晶石ＬｉＭｎ２Ｏ４的晶体结构作了简要介绍。综述了近年来在ＬｉＭｎ２Ｏ４薄膜电极制备方面的研究进展,包括静电喷雾沉积（ＥＳＤ）、静脉激光沉积（ＰＬＣ）、射频磁溅射（ＲＦＭＳ）等等,并对今后的研究方向进行了展望。     

The impact of upper cut-off voltages on the electrochemical behaviors of composite electrode 0.3Li(2)MnO(3)·0.7LiMn(1/3)Ni(1/3)Co(1/3)O(2)

This work has initiated an investigation on the electrochemical behaviors and the structure changes of the composite electrode 0.3Li(2)MnO(3)·0.7LiMn(1/3)Ni(1/3)Co(1/3)O(2) when charged with different cut-off voltages. It is found that the charge cut-off voltages could not only affect the capacity property and coulombic efficiency, but also alter the electrode kinetics of the composite. As a consequence, the electrochemical activation of the composite electrode is highly dependent on the charge cut-off voltages: when the charge cut-off voltage is higher than 4.5 V, the inert component Li(2)MnO(3) in the composite electrode is completely activated. At the meanwhile, there occurred an irreversible oxygen loss during the initial charge process, which yielded a hollow sphere in the electrode. Regardless of charge voltages, Mn ions in the composite electrode were presented in an oxidation state of +4, while Co(2+) ions were detected at the surface of the electrode when cycled at low voltages. Ni ions in the composite could react with organic or inorganic species and then cover the surface of the cycled electrode.