The electrochemical properties of Fe- and Ni-cosubstituted Li2MnO3 via combustion method

The Co-free Li_1.20Mn_0.54Ni _x Fe _y O₂ (x/y?=?0.5, 1.0, 2.0) materials were synthesized by combustion method. The effects of the preparation condition on the structure, morphology, and electrochemical performance were investigated by X-ray diffractometry, scanning electron microscopy, charge–discharge tests, and cyclic voltammetry (CV). The results indicate that the structure and electrochemical characteristics are sensitive to the preparation condition when a large amount of Fe is included. A pure layered α-NaFeO₂ structure with R-3m space group and the discharge capacities of over 200 mAh g^?1 were observed in some as-prepared cathode materials. Particularly, the Li_1.2Mn_0.54Ni_0.13Fe_0.13O₂ prepared by mixing an excess amount of lithium and by firing at 600 °C exhibits a second discharge capacity of 264 mAh g^?1 in the voltage range of 1.5–4.8 V under current density of 30 mA g^?1 at 30 °C and discharge capacity of 223 mAh g^?1 at 2.0–4.8 V. Nevertheless, an unpleasant capacity fading was observed and is primarily ascribed to transformation from a rock-layered structure into a spinel one according to CV testing.     

Relaxation electrochemical noise of Li/SOCl2 and Li/MnO2 primary batteries

Journal of Solid State Electrochemistry - Electrochemical noise measurements were carried out on commercially available Li/SOCl2 and Li/MnO2 primary batteries during relaxation following removal of...     

Measurement of electrochemical noise of a Li/MnO2 primary lithium battery

Journal of Solid State Electrochemistry - Electrochemical noise of a Li/MnO2 primary lithium battery was measured and analyzed during discharge process for the first time. The amplitude of the...     

Development of High NIR-Reflective Red Li2MnO3 Pigments

In this work, the development of a novel class of eco-friendly red pigments based on doped Li₂MnO₃ is reported. These new compounds offer red color values of a* > 34, which are recognizably higher than the red value provided by the commonly used red pigment iron oxide Bayferrox 4130. However, the real outstanding attribute of these novel substances is their strikingly high NIR-reflectance that gives promise for a new class of materials for the practical utilization as cool pigments in building components and ceramics. We have synthesized the inorganic pigments by conventional solid-state reactions at 900 °C and subsequently carried out the structural characterizations by X-ray powder diffraction (XRPD) and Rietveld analysis. We recorded the diffuse reflectance spectra of the obtained powders and determined the color properties by means of CIE L*a*b* coordinates. Finally, we measured the NIR reflectance and calculated the NIR solar reflection of these compounds affording values above 85 % in the range from 700 to 2500 nm.     

Surface activation of Li2MnO3 phase by glacial acetic acid induces spinel-like phase for higher electrochemical performance

Journal of Solid State Electrochemistry - The surface activation treatment of Li-rich materials with glacial acetic acid (GAA, a unitary organic weak acid) has been systematically investigated. The...     

Wide-frequency band measurement and analysis of electrochemical noise of Li/MnO2 primary battery

Journal of Solid State Electrochemistry - The electrochemical noise of a commercially produced Li/MnO2 primary battery was measured during discharge via a constant value resistor. Power spectral...     

Li2MnO3 content effects on thermal,structural, electrical and electrochemical properties of xLi2MnO3-(1-x)LiNi0.9Zn0.1O2 cathode materials

xLi₂MnO₃-(1-x)LiNi_0.9Zn_0.1O₂ (x = 0.1, 0.2 and 0.3) cathodes were prepared by two steps solid-state reaction method. Layered crystalline phases (space groups of C2/m for Li₂MnO₃ and R3m for LiNi_0.9Zn_0.1O₂) were detected in all cathodes. FTIR study also revealed the formation of the layered-type structures of all cathodes. The structural parameters were greatly influenced by the contents of Li₂MnO₃ in xLi₂MnO₃-(1-x)LiNi_0.9Zn_0.1O₂. The electrical conductivities were found in the range of 1.2 × 10^?6 to 2.7 × 10^?6 S/cm. The dielectric spectra revealed the interfacial polarization Maxwell–Wagner type dielectric dispersion existing in all samples. The cathodes delivered the discharge capacities of 149 (x = 0.1), 151 (x = 0.2) and 157 mAh/g (x = 0.3) with capacity retention between 94.6 and 96.8% when they were cycled from 3.0 to 4.5 V under 0.1C rate. The x = 0.3 cathode exhibited the highest cyclic performance (96.8%) after 10 cycles due to its lower cations disorder.     

The relation between structural features and electrochemical activity of MnO2 nanoparticles synthesized from a polyol-made Mn3O4 precursor

A simple hybrid synthesis processing method was developed to synthesize γ-MnO₂ nanocrystalline particles. The polyol method was modified by the addition of nitric acid in order to allow the synthesizing of single-phase Mn₃O₄ in a large scale. In the sequence, the acid digestion technique was used to transform Mn₃O₄ into γ-MnO₂. Structural and morphological characterization was carried out by X-ray diffractometry, Infrared and Raman spectroscopy, thermogravimetric analysis, nitrogen adsorption isotherm, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge–discharge measurements. The synthesized material exhibits a specific capacitance of 125.1 F?g^?1 at a mass loading of 0.98 mg?cm^?2. The relation between structural features and electrochemical activity is discussed by comparing the synthesized material with commercial electrolytic manganese dioxide.     

富锂层状正极材料Li2MnO3的表面改性及其电化学性能研究

Li₂MnO₃正极材料具有较高的理论容量（459 mAh·g ^-1）,不仅安全无毒还能够大大降低电池的制造成本,从而受到越来越多的关注. 然而,较低的首圈库仑效率和较差的循环性能妨碍了其在锂电池中的实际应用. 在此,作者研究了MgF₂涂层对Li₂MnO₃正极材料的电化学性能. 结果表明,MgF₂涂层诱导部分层状Li₂MnO₃向尖晶石相转化,从而降低了首圈不可逆容量,提高库仑效率. 重量比为0.5%、1.0%和2.0%的MgF₂涂层电极的初始库仑效率分别为70.1%、77.5%和84.9%,而原始电极仅为57.7%. 充放电曲线表明,1.0wt.%MgF₂涂层改性的Li₂MnO₃具有最高的充放电容量和最佳的循环稳定性. 40个循环后1.0wt.%MgF₂涂层样品的容量保持率为81%,远高于原始样品的容量保持率（53.6%）. 电化学阻抗谱结果表明MgF₂涂层减少了不利成分的快速沉积,并改善了电极的循环稳定性.     

Zum thermischen Verhalten von Li3MnO4. II [1, 2]. Über α- und β- Li2MnO3

Thermal Behaviour of Li₃MnO₄. II. α- and β-Li₂MnO₃ By thermal decomposition of Li₃MnO₄ we obtained two new forms of Li₂MnO₃: α-Li₂MnO₃ crystallizes due to Guinier-Simon photographs cubic face-centered with a = 4.09₂ Å, β-Li₂MnO₃ hexagonal with a = 4,93, c = 14.24 Å, c/a = 2.89. α-Li₂MnO₃ is paramagnetic with μ = 3,82 B.M. Below the Neel temperature (≈? 50 K) β-Li₂MnO₃ is antiferromagnetic. Effective Coordination Numbers, ECoN, are calculated and discussed.     

Boosting Li-ion storage in Li2MnO3 by unequal-valent Ti4+-substitution and interlayer Li vacancies building

Lithium rich layered oxide (LRLO) has been considered as one of the promising cathodes for lithium-ion batteries (LIBs). The high voltage and large capacity of LRLO depend on Li₂MnO₃ phase. To ameliorate the electrochemical performance of Li₂MnO₃, also written as Li(Li_1/3Mn_2/3)O₂, we propose a strategy to substitute Mn⁴⁺ and Li⁺ in Mn/Li transition metal layer with Ti⁴⁺, which can stabilize the structure of Li₂MnO₃ by inhibiting the excessive oxidation of O^2? above 4.5 V. More significantly, the unequal-valent substitution brings about the emergence of interlayer Li vacancies, which can promote the Li-ion diffusion based on the enlarged interlayer and increase the capacity by activating the Mn^3+/4+ redox. We designed Li_0.7[Li_1/3Mn_2/3]_0.7Ti_0.3O₂ with high interlayer Li vacancies, which presents a high capacity (290 mAh/g at 10 mA/g) and stable cycling performance (84% over 60 cycles at 50 mA/g). We predict that this strategy will be helpful to further improve the electrochemical performance of LRLOs.     

Molybdenum Substitution for Improving the Charge Compensation and Activity of Li2MnO3

Lithium‐rich layer‐structured oxides xLi₂MnO₃? (1?x)LiMO₂ (0<x<1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy‐density lithium ion batteries. However, the characteristic charge compensation contributed by O^2? in Li₂MnO₃ leads to the evolution of oxygen during the initial Li⁺ ion extraction at high voltage and voltage fading in subsequent cycling, resulting in a safety hazard and poor cycling performance of the battery. Molybdenum substitution was performed in this work to provide another electron donor and to enhance the electrochemical activity of Li₂MnO₃‐based cathode materials. X‐ray diffraction and adsorption studies indicated that Mo⁵⁺ substitution expands the unit cell in the crystal lattice and weakens the Li?O and Mn?O bonds, as well as enhancing the activity of Li₂MnO₃ by lowering its delithiation potential and suppressing the release of oxygen. In addition, the chemical environment of O^2? ions in molybdenum‐substituted Li₂MnO₃ is more reversible than in the unsubstituted sample during cycling. Therefore molybdenum substitution is expected to improve the performances of the Li₂MnO₃‐based lithium‐rich cathode materials.     

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...     

MnO2-embedded-in-mesoporous-carbon-wall structure for use as electrochemical capacitors

We present an in situ reduction method to synthesize a novel structured MnO(2)/mesoporous carbon (MnC) composite. MnO(2) nanoparticles have been synthesized and embedded into the mesoporous carbon wall of CMK-3 materials by the redox reaction between permanganate ions and carbons. Thermogravimetric analysis (TG), X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM), and cyclic voltammetry were employed to characterize these composite materials. The results show that different MnO(2) contents could be introduced into the pores of CMK-3 treated with different concentrations of potassium permanganate aqueous solution, while retaining the ordered mesostructure and larger surface area. Increasing the MnO(2) content did not result in a decrease in pore size from the data of nitrogen sorption isotherms, indicating that MnO(2) nanoparticles are embedded in the pore wall, as evidenced by TEM observation. We obtained a large specific capacitance over 200 F/g for the MnC composite and 600 F/g for the MnO(2), and these materials have high electrochemical stability and high reversibility.     

Thermal stability of Li2MnO3: from localized defects to the spinel phase

The thermal stability of Li(2)MnO(3) has been investigated by the means of coupled differential thermal analysis and thermogravimetric analysis associated with powder X ray diffraction. Various experiments performed in air and in argon allowed us to propose a mechanism of spinel-type defects formation in intergrowth with Li(2)MnO(3) when treated in air above 900 °C. The fidelity of the DIFFaX simulations performed led to the understanding of the influence of the existence of spinel type defects intergrowth on X ray and electron diffraction patterns. The formation of these defects occurs during cooling and is preceded by the formation of LiMnO(2) defects in heating. With sufficiently long thermal treatments, defects expand such that a spinel type phase can be observed after cooling.     

尖晶石结构材料Li_2MgTi_3O_8的制备及其电化学性能

以Li2CO3、MgO和TiO2为原料,采用高温固相法合成了具有尖晶石结构材料Li2MgTi3O8。采用X射线衍射(XRD)、傅里叶红外光谱(FTIR)等手段对材料的晶体结构进行了表征,材料的电化学性能通过恒流充放电、循环伏安(CV)进行测试。结果表明,材料具有优异的循环稳定性和良好的库伦效率。在室温下,充放电倍率为0.5C时,Li2MgTi3O8首次放电比容量为215.6mAh·g-1,100周循环后保持在225mAh·g-1。     

A hierarchical porous MnO2-based electrode for electrochemical capacitor

A hierarchical porous MnO₂-based electrode was prepared and its electrochemical performance for electrochemical capacitors was investigated. In this work, porous MnO₂ film with pore size of 2?C3?nm in diameter was deposited on a three-dimensional porous current collector by cathodic electrodeposition associated with subsequent controlled heat treatment at 200°C for 2?h. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the heat treatment has a great effect on the formation of the porous structure of MnO₂ layer, and the disordered porous structure was caused by dehydration during the heat treatment. Cyclic voltammetry and galvanostatic charge?Cdischarge tests showed that both energy and power densities are enhanced due to the unique hierarchical porous structure. The electrode delivers a high specific capacitance of 385?F?g^?1 at a high current density of 5?A?g^?1 within a potential window of ?0.05????0.85?V, and also exhibits excellent rate capability and electrochemical stability.     

Preparation of MnO2 and MnO2/carbon nanotubes nanocomposites with improved electrochemical performance for lithium ion batteries

Journal of Solid State Electrochemistry - Manganese dioxide (MnO2) nanomaterials and manganese dioxide/carbon nanotubes (MnO2/CNTs) nanocomposites were prepared by chemical precipitation and...     

Interface synthesis of mesoporous MnO2 and its electrochemical capacitive behaviors

Mesoporous MnO(2) has been synthesized by means of a novel, facile, and template-free method by virtue of a soft interface between CCl(4) and H(2)O without any surfactants or organometallic precursors or ligands. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, and an ASAP2010 autoadsorption analyzer were applied to investigate the composition and microstructure of the as-synthesized MnO(2). The structure characterizations indicated a good mesoporous structure for as-prepared MnO(2) with an adsorption average pore diameter of 9.7 nm, mesoporous volume of 0.58 cm(3) g(-1), and Brunauer-Emmett-Teller specific surface area of 239 m(2) g(-1). Electrochemical properties of the mesoporous MnO(2) were elucidated by cyclic voltammograms, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 1 M Na(2)SO(4) electrolyte. Electrochemical data analysis demonstrated that as-synthesized MnO(2) had good capacitive behavior due to its unique mesoporous structure. A specific capacitance of ca. 220 F g(-1) could still be delivered for the mesoporous MnO(2) even at a scan rate of 100 mV s(-1).     

电化学电容器电极材料超细MnO2的制备及表征

高性能的电化学电容器具有极其重要和广阔的应用前景(1)。以RuO2等贵重金属氧化物为电极材料的电化学电容器已应用于多个领域(2),但昂贵的价格限制了它们更加广泛的应用。有些廉价金属氧化物也具有一定的氧化还原准电容,如Co3O4、NiO和MnO2等(1,3 6)。二氧化锰价格低廉,资源丰富,电化学性能好,其作为电化学电容器的活性材料具有更大的应用前景和价值。本文采用K2S2O8氧化MnSO4·H2O制得超细MnO2,并通过XRD、TEM和SEM测试对其进行表征,并研究了其在0 5mol/LNa2SO4水溶液中的循环伏安性能、恒流充放性能以及电容稳定性能。1…