Synthesis and enhanced electrochemical properties of LiNi0.6Co0.2Mn0.2O2 cathode materials via SDBS-assisted hydrothermal method

Journal of Solid State Electrochemistry - LiNi0.6Co0.2Mn0.2O2 (NCM622) materials with shuttle-like hierarchical micro architecture are prepared by sodium dodecyl benzene sulfonate (SDBS) assisted...     

Synthesis and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 as a concentration-gradient cathode material for lithium batteries

A well-ordered and spherical LiNi0.6Co0.2Mn0.2O2 cathode material was successfully synthesized from Ni and Mn concentration-gradient precursors via co-precipitation. The crystal structure, morphology and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and charge-discharge tests. The material delivered an initial discharge capacity of 174.3 mAh/g at 180 mA/g （1 C rate） between 2.8 and 4.3 V and more than 93.1% of that was retained after 100 cycles. In addition, it also exhibited excellent rate capability, high cut-off voltage and temperature performance.     

La0.8Sr0.2Ga0.8Mg0.2O2.8的电化学性质及其在SOFC中的应用

采用凝胶浇注法制备具有较高氧离子电导率的固体电解质La0.8Sr0.2Ga0.8Mg0.2O2.8粉料.X射线衍射结果表明,于1400℃焙烧后即形成了钙钛矿结构,无杂相存在.探讨了粉料压制坯体的致密化和导电性能在1450℃下与烧结时间的关系,发现烧结时间为18h时其相对密度达98.3%,而在24h的情况下,样品具有最佳的氧离子导电性.采用Ni-Ce0.8Gd0.2O1.9作为阳极,La0.8Sr0.2Ga0.6Ni0.4O2.7作为阴极,组装了平板型固体氧化物燃料电池(SOFC).阳极和阴极分别通入含3%H2O的氢气和空气,750℃时的开路电压为1.04V,最大输出功率密度(P)达252mW/cm2(U=0.48V,J=525mA/cm2).     

高比容量锂离子电池正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)的制备及性能北大核心CSCD

以LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)为研究对象,通过共沉淀法制备了不同F物质的量分数(0%、1%、3%、5%)的LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)三元正极材料(NCM),通过对NCM材料的晶格结构、微观形貌、电化学性能进行分析,结果表明:F掺杂后提高了NCM材料的结晶度,降低了阳离子混乱程度,适量的F掺杂有助于减小NCM三元正极材料的尺寸和提高均匀性,F的掺杂还能够降低NCM三元正极材料的极化现象,初始放电比容量随着F的掺杂含量升高呈现出先升高后降低的趋势,循环性能随着F的掺杂得到了提高,F掺杂物质的量分数为3%的NCM三元正极材料初始放电比容量167.2 mA·h/g,容量保持率达到98.5%,阻抗较小,电化学性能最优。     

La0.8Sr0.2Ga0.8Mg0.2O3与La0.8Sr0.2Ga0.8Mg0.15Co0.05O3电导的对比

采用固相合成法制备了La0.8Sr0.2Ga0.8Mg0.2O3(LSGM8282)和La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5), 利用四电极交流阻抗法和Hebb-Wagner 极化法对比研究了两种材料的总电导率和电子电导率. 实验结果表明, LSGM8282 的总电导率与氧分压无明显依赖关系, 而LSGMC5 的总电导率在高氧分压区随氧分压降低而增加,在中等氧分压区域基本保持不变. 在973-1173 K的温度范围内, LSGM8282的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和1/4.在1073-1173 K的温度范围内, LSGMC5的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和约为1/8, 表明LSGMC5的空穴产生机制可能与LSGM8282不同. LSGM8282 的氧离子电导率与氧分压无关, 而LSGMC5 的氧离子电导率在高氧分压区随氧分压的减小而增加.     

Novel core-shell-structured Li[(Ni0.8Co0.2)0.8(Ni0.5Mn0.5)0.2]O2 via coprecipitation as positive electrode material for lithium secondary batteries

We have successfully synthesized a spherical core-shell structure based on Li[(Ni0.8Co0.2)0.8(Ni0.5Mn0.5)0.2]O2 via a coprecipitation route. According to the careful examination by scanning electron microscopy (SEM), transmission electron microscopy energy-dispersive spectroscopy (TEM-EDS), and X-ray diffraction (XRD), it was found that the core-shell particle consisted of Li[Ni0.8Co0.2]O2 as the core and Li[Ni0.5Mn0.5]O2 as the shell, of which the thickness was estimated to be 1 to approximately 1.5 microm. Both the core and shell were dense as confirmed by SEM. Though the core-shell-structured Li[(Ni0.8Co0.2)0.8(Ni0.5Mn0.5)0.2]O2 delivered a slightly reduced initial discharge capacity, the capacity retention and thermal stability were significantly improved relative to those of the Li[Ni0.8Co0.2]O2 electrode without the Li[Ni0.5Mn0.5]O2 shell. The carbon/Li[Ni0.8Co0.2]O2 pouch cell underwent an explosive ignition during the nail penetration test, whereas the carbon/Li[(Ni0.8Co0.2)0.8(Ni0.5Mn0.5)0.2]O2 cell remained stable, demonstrating the superior thermal stability of the core-shell electrode. As a new positive electrode material, the core-shell-structured Li[(Ni0.8Co0.2)0.8(Ni0.5Mn0.5)0.2]O2 is a significant breakthrough in the development of high-capacity lithium secondary batteries.     

高首效富镍正极材料LiNi0.6Co0.2Mn0.2O2的合成及电化学性能研究

采用共沉淀-高温固相烧结的方法合成了富镍正极材料LiNi_0.6Co_0.2Mn_0.2O₂(简称NCM622),通过X射线粉末衍射（XRD）/Rietveld精修法、扫描电子显微镜（SEM）及电化学测试,对不同温度下合成材料的结构、形貌、电化学性能进行表征. 结果表明,800℃下,NCM622阳离子混排程度最低(~1.97%),首圈库伦效率高达92.2%,100圈容量保持率为81.4%.     

Operando Observation of Structural Evolution and Kinetics of Li[Ni0.6Co0.2Mn0.2]O2 at Elevated Temperature

Li[Ni_0.6Co_0.2Mn_0.2]O₂(NCM622) is one of the best commercialized cathodes in the battery field. However, poor cyclability at relatively high temperature hinders its multiple usages. Here, operando tests were performed to investigate the phase transitions and electron/ion transfer process of layered NCM622 at 25 and 55℃. The identified spinel structure resulting in the poor cyclability at 55℃ guides the commercialization of batteries at high temperature.     

Mg1.8La0.2Ni-xNi nanocomposites for electrochemical hydrogen storage

Mg1.8La0.2Ni hydrogen storage alloy was ball-milled with Ni powder, leading to the formation of a nanocrystalline and amorphous microstructure with particle sizes less than 50 nm in diameter. Each sample was examined by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This structure was beneficial for the reduction of electrochemical impedance, as well as significant improvement of its discharge capacity, cycle life, and rate capability for electrochemical hydrogen storage in an alkaline solution. When the molar ratio (x) of Ni over Mg1.8La0.2Ni was equal to 2, the dehydriding capacity reached 2.55 wt % from electrochemical pressure-temperature isotherms (P-C-T). It was in good agreement with its initial discharge capacity, 716 mA*h/[g of (Mg1.8La0.2Ni)], observed from the electrochemical charge and discharge process. After 50 cycles, its discharge capacity still reached 381 mA*h/[g of (Mg1.8La0.2Ni)]. Further results showed that this composite had a promising high rate capability. At the current density of 1200 mA/g its discharge capacity reached 48% of its initial capacity.     

La0.8Sr0.2Ga0.8Mg0.2O3－α陶瓷的质子导电性能研究

采用溶胶-凝胶法合成了La_0.8Sr_0.2Ga_0.8Mg_0.2O_3－a陶瓷样品, 用XRD, DSC-TGA, SEM, 交流阻抗谱, 气体浓差电池及气体电化学透过等方法对样品的结构和性质进行了表征和测试. 首次对该样品的质子导电性能进行了研究. 该陶瓷样品具有良好的微观结构, 相对密度达95.1%; 氢浓差电池电动势的实测值与理论值吻合, 离子迁移数为1; 在干燥的氧气气氛中是一个纯的氧离子导体; 氢的电化学透过速率的实测值与理论值吻合, 证明该样品在氢气气氛中几乎是一个纯的质子导体, 质子电导率在1000 ℃时高达0.14 S•cm^－1.     

Chemical and physical properties of complex perovskites in the La0.8Sr0.2MnO3−δ–La0.8Sr0.2CuO2.4+δ–La0.8Sr0.2FeO3−δ system

Perovskites resulting from discrete changes in composition within the quasi-ternary system La_0.8Sr_0.2MnO_3−δ–La_0.8Sr_0.2CuO_2.4+δ–La_0.8Sr_0.2FeO_3−δ were investigated under constant experimental conditions with the objective of obtaining an overview of the variation of the properties relevant for possible future applications. Nineteen nominal perovskite compositions within this system were systematically selected and synthesized under identical conditions by the Pechini method. The experimental data obtained on quantitative chemical analysis, powder X-ray diffraction, electrical conductivity and thermal expansion are presented collectively for the first time to facilitate comparisons. The formation and distribution of the different crystallographic phases at 950 °C within this quasi-ternary system are shown. The DC electrical conductivity is strongly influenced by the Cu content and increases up to 276 S cm⁻¹ for La_0.8Sr_0.2CuO_2.4+δ. The thermal expansion is dominated by the Cu/Mn ratio and is almost independent of the Fe content.     

Ce0.8Gd0.2-xPrxO1.9固溶体的合成与表征

利用X射线衍射(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和交流阻抗谱对溶胶-凝胶法制备的稀土双掺杂固溶体Ce0.8Cd0.2-xPrxO1.9(x=0,0.02,0.10)的结构和导电性进行了研究.XRD结果表明,经800℃焙烧所得样品都形成了单相立方萤石结构,平均晶粒尺寸在23～30 nm之间;X...     

Na+掺杂锂离子电池正极材料LiNi0.6 Co0.2 Mn0.2 O2的制备及电化学性能

采用草酸盐共沉淀法制备了钠掺杂改性的Li_0.98Na_0.02Ni_0.6Co_0.2Mn_0.2O₂正极材料,借助X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、能量分散谱（EDS）、感应耦合等离子体原子发射光谱（ICP-AES）、电化学阻抗谱（EIS）和恒电流充放电测试等手段对材料的颗粒形貌、晶体结构和电化学性能进行了研究.结果表明,掺钠后的材料具有更完善的α-NaFeO₂结构（空间群为+/Ni²⁺阳离子混排和更大的Li层间距,易于Li⁺在晶格中的快速脱嵌迁移.电化学性能测试结果证实掺钠样品具有优异的循环稳定性和高倍率性能,在2.7~4.3 V,1C下循环100次后,放电比容量仍为146 mA·h/g（容量保持率为95.4%）,在0.1C,0.2C,0.5C,1C,3C,5C,10C和20C时的放电比容量分别为181,168,162,155,143,136,126和113 mA·h/g.     

锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的酸浸改性研究

为提高锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的首次充放电效率,对固相法合成的该材料进行了酸浸的改性研究。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构、形貌进行了表征。结果表明,Li[Li0.2Ni0.2Mn0.6]O2经过酸处理后,首次放电效率得到了较大的提高,但是放电中值电压明显下降。其中,0.5 mol.L-1的硝酸浸泡5 h的效果最佳,首次放电效率达到了86.7%,同时放电容量达到最大值的循环次数大大减少。酸浸改性的原因被归结于材料表面出现了富锂尖晶石结构Li4Mn5O12相。     

CTAB辅助水热合成高镍三元材料LiNi0.6Co0.2Mn0.2O2及其高低温性能研究

以醋酸盐为原料, 以十六烷基三甲基溴化铵(CTAB)为分散剂, 通过水热合成-高温烧结的方法制备高镍三元正极材料LiNi_0.6Co_0.2Mn_0.2O₂. 结果表明, 适量分散剂CTAB的加入可有效调节材料的颗粒形貌尺寸, 降低锂镍混排, 改善材料的电化学性能. 加入2%(质量分数) CTAB时, 制备的电池材料具有完整有序的层状结构, 且颗粒均匀分散, 具有最佳的循环性能和高低温性能. 该材料在室温及倍率1C下循环100次后, 容量保持率为88.5%. 在?20, 25和55 ℃条件下及倍率0.1C充放电时, 首次放电比容量分别为60.3, 168.5和207.2 mA·h/g.     

Synthesis of Li[Li0.2Ni0.2Mn0.6]O2 by radiated polymer gel method and impact of deficient Li on its structure and electrochemical properties

Layered Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li[Li_0.2Ni_0.2Mn_0.6]O₂ compounds were successfully synthesized by radiated polymer gel (RPG) method. The effect of deficient Li on the structure and electrochemical performance was investigated by means of X-ray diffraction, X-ray absorption near-edge spectroscopy and electrochemical cell cycling. The reduced Ni valence in Li[Li_0.16Ni_0.21Mn_0.63]O₂ leads to a higher capacity owing to faster Li⁺ chemical diffusivity relative to the baseline composition Li[Li_0.2Ni_0.2Mn_0.6]O₂. Cyclic voltammograms (CV) and a simultaneous direct current (DC) resistance measurement were also performed on Li/Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li/Li[Li_0.2Ni_0.2Mn_0.6]O₂ cells. Li[Li_0.16Ni_0.21Mn_0.63]O₂ shows better electrochemical performance with a reversible capacity of 158 mA hg⁻¹ at 1C rate at 20 °C.     

亲锂电解液在LiNi0.6Mn0.2Co0.2O2／Li二次锂金属电池中的电化学性能

金属锂电池被认为是具有良好前景的下一代高能量密度电池。然而,传统的碳酸酯类电解液与锂的亲和性差,在循环过程中由于锂枝晶的生长和固体电解质膜（SEI）的不稳定导致金属锂电池性能快速衰减。采用1.2 mol／L六氟磷酸锂（LiPF₆）／二氟草酸硼酸锂（LiDFOB）／氟代碳酸乙烯酯（FEC）／碳酸二乙酯（DEC）,并添加了双三氟甲磺酰亚胺锂（LiTFSI）作为电解液,对其在LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li（单位面积上负／正极材料的实际容量的比N／P＝2.85）电池中的电化学性能进行了研究。LiNi_0.6Mn_0.2Co_0.2O₂／40 μm-Li电池表现出优异的循环稳定性（循环120圈后,容量保持率>93%）和倍率性能（3C倍率下放电比容量为110 mA·h／g）。良好的电化学性能主要归因于该电解液可以在金属锂表面形成致密且稳定的SEI,并抑制锂枝晶的产生。     

Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9Co0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane

Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9Co0.1O3 perovskite oxides as oxygen cartier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction. Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox re-action decreased over La0.8Sr0.2Fe0.9Co0.1O3 oxide, while LaFeO3 and Lao.sSro.2FeO3 exhibited excellent structural stability and continuous oxygen supply.     

钙钛矿型La0.2Pb0.4Sr0.4FeO3的制备及其气敏性

采用溶胶-凝胶法首次制备出平均粒径为22.3 nm的La0.2Pb0.4Sr0.4FeO3的晶体,这种复合晶体是正交的钙钛矿型结构.通过对其导电性和气敏性的研究,发现La0.2Pb0.4Sr0.4FeO3材料是一种p型半导体材料,并且在175℃下对甲醛具有很好的气敏性.     

LiNi0.8Co0.2O2/CNTs Composite used as the Materials for Supercapacitor Electrodes

Stupercapacitors or electrochemical capacitors(ECs) have attracted considerable attentionas an intermediate power source between conventional capacitors and batteries since they possesshigh power density and energy density, exhibit excellent reversibility, and have long cycle life1.Conductive polymers2, electrically conductive metal oxide3,4, activated carbon5 and carbonnanotubes(CNTs) 6-9 have been used as supercapacitor electrode materials. LiNi0.sCo0.2O2 is apromising lithium battery material because it has some advantages of both LiNiO2 and LiCoO2besides its low cost and high power10.In this paper, the electrochemical properties of supercapacitors based on LiNi0.8Co0.2O2/carbonnanotubes composite and LiNi0.8Co0.2O2/acetylene black composite and CNTs in 1 mol/LLiClO4/EC+DEC [V(EC):V(DEC)=1:1] electrolyte have been investigated by means of constantcharge/discharge current tests. The experiment results show that the LiNi0.8Co0.2O2/carbon nanotubescomposite has better properties than others, and the maximun specific capacitance of thesupercapacitor can reach 284.88F/g, while the energy density is up to 158.27Wh/Kg.That discharge capacities, coulombic efficiencies and energy densities at the first cycle and themaximum value and capacity retention at the 100th cycle for supercapacitors using differentelectrode materials (A) LiNi0.8Co0.2O2/acetylene black, (B) LiNi0. 8Co0.2O2/CNTs, (C) CNTs is listedin table 1*Capacity retention rate obtained by dividing the discharge capacity at the 100th cycle by themaximum valueFrom above, the LiNi0. 8Co0.2O2/carbon nanotubes composite should be a good candidatesupercapacitor electrode material.