Synthesis of LiNi1/3Co1/3Mn1/3O2−zFz cathode material from oxalate precursors for lithium ion battery

The layered LiNi_1/3Co_1/3Mn_1/3O_2−zF_z (0 ≤ z ≤ 0.12) cathode materials were synthesized from oxalate precursors by a simple self-propagating solid-state metathesis method with the help of the ball milling and the following calcination. Li(Ac)·2H₂O, Ni(Ac)₂·4H₂O, Co(Ac)₂·4H₂O, Mn(Ac)₂·4H₂O(Ac = acetate), LiF and excess H₂C₂O₄·2H₂O were used as starting materials without any solvent. The structural and electrochemical properties of the prepared LiNi_1/3Co_1/3Mn_1/3O_2−zF_z were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and electrochemical measurements, respectively. The XRD patterns indicate that all samples have a typical hexagonal structure with a space group of . The FESEM images show that the primary particle size of LiNi_1/3Co_1/3Mn_1/3O_2−zF_z gradually increases with increasing fluorine content. Though the fluorine-substituted LiNi_1/3Co_1/3Mn_1/3O_2−zF_z have lower initial discharge capacities, a small amount of fluorine-substituted LiNi_1/3Co_1/3Mn_1/3O_2−zF_z (z = 0.04 and 0.08) exhibit excellent cycling stability and rate capability compared to fluorine-free LiNi_1/3Co_1/3Mn_1/3O₂.     

Li4Mn5O12包覆对三元正极材料结构和性能的影响

LiNi(1/3)Mn(1/3)Co(1/3)O2具有很高的理论比容量,但是三元正极材料在高电压下长循环时,其表面结构发生较大的衰退,导致电池的循环性能和倍率性能变差。本文采用耐高电压且结构稳定的富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2可以有效改善材料的电化学性能。通过XRD、SEM、XPS和TEM等手段对包覆后的材料进行分析,证实了在LiNi(1/3)Mn(1/3)Co(1/3)O2的表面形成了10nm厚的均匀Li4Mn5O(12)的包覆层;在循环100圈后,包覆后的LiNi(1/3)Mn(1/3)Co(1/3)O2仍具有179.5m Ah/g的放电比容量和88.6%容量保持率,明显高于未包覆的LiNi(1/3)Mn(1/3)Co(1/3)O2的78.3%容量保持率。因此,利用富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2为实现更高能量密度的锂离子电池提供了新的途径。     

Effects of complexants on [Ni1/3Co1/3Mn1/3]CO3 morphology and electrochemical performance of LiNi1/3Co1/3Mn1/3O2

LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials for the application of lithium ion batteries were synthesized by carbonate co-precipitation routine using different ammonium salt as a complexant. The structures and morphologies of the precursor [Ni_1/3Co_1/3Mn_1/3]CO₃ and LiNi_1/3Co_1/3Mn_1/3O₂ were investigated through X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The electrochemical properties of LiNi_1/3Co_1/3Mn_1/3O₂ were examined using charge/discharge cycling and cyclic voltammogram tests. The results revealed that the microscopic structures, particle size distribution, and the morphology properties of the precursor and electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ were primarily dependent on the complexant. Among all as-prepared LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials, the sample prepared from Na₂CO₃–NH₄HCO₃ routine using NH₄HCO₃ as the complexant showed the smallest irreversible capacity of 19.5 mAh g⁻¹ and highest discharge capacity of 178.4 mAh g⁻¹ at the first cycle as well as stable cycling performance (98.7% of the initial capacity was retained after 50 cycles) at 0.1 C (20 mA g⁻¹) in the voltage range of 2.5–4.4 V vs. Li⁺/Li. Moreover, it delivered high discharge capacity of over 135 mAh g⁻¹ at 5 C (1,000 mA g⁻¹).     

Electrochemical behavior of spherical LiNi1/3Co1/3Mn1/3O2 as cathode material for aqueous rechargeable lithium batteries

Spherical LiNi_1/3Co_1/3Mn_1/3O₂ powders have been synthesized from co-precipitated spherical metal hydroxide. The electrochemical performances of the LiNi_1/3Co_1/3Mn_1/3O₂ electrodes in 1 M LiNO₃, 5 M LiNO₃, and saturated LiNO₃ aqueous electrolytes have been studied using cyclic voltammetry and ac impedance tests in this work. The results show that LiNi_1/3Co_1/3Mn_1/3O₂ electrode in saturated LiNO₃ electrolyte exhibits the best electrochemical performance. An aqueous rechargeable lithium battery containing LiNi_1/3Co_1/3Mn_1/3O₂ cathode, LiV_2.9Ni_0.050Mn_0.050O₈ anode, and saturated LiNO₃ electrolyte is fabricated. The battery delivers an initial capacity of 98.2 mAh g⁻¹ and keeps a capacity of 63.9 mAh g⁻¹ after 50 cycles at a rate of 0.5 C (278 mA g⁻¹ was assumed to be 1 C rate).     

Synthesis and surface treatment of LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion batteries

In order to shorten process time and possibly reduce synthesis cost of LiNi_1/3Co_1/3Mn_1/3O₂, the cathode material was prepared by solution combustion and microwave synthesis routes with reduced duration of calcination. The products were also surface-modified with Al₂O₃ by a mechano-thermal coating process to enhance cyclability. The structure and morphology of the bare and the surface-modified LiNi_1/3Co_1/3Mn_1/3O₂ samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, and differential scanning calorimetry techniques. At a 0.1-C rate and between 4.6 and 2.5 V, the products delivered a first-cycle discharge capacity of as much as 195 mA h/g. Surface modification of LiNi_1/3Co_1/3Mn_1/3O₂ with alumina resulted in improved cyclability.     

锂离子电池镍掺杂尖晶石LiMn2O4正极材料的电子结构

采用密度泛甬平面波赝势方法对LiMn2O4和LiNi0.5Mn1.5O4的几何结构进行了优化,并计算了相应的电子结构.计算的结果表明:在Li 脱嵌前后,LiMn2O4和LiNi0.5Mn1.5O4均为导体,且锂元素主要以离子形式存在于两种材料中,O2p轨道与Mn(Ni)的3d轨道形成了较强的共价键.Li 嵌入导致Mn(Ni)3d轨道的态密度峰发生移动.Ni的掺杂导致Mn(Ni)和O2p轨道的成键作用得以加强,电子在Mn(Ni)3d轨道的填充发生变化,从而提高了电池的充放电电压.     

氨蒸发诱导法制备纳米结构LiNi1/3Co1/3Mn1/3O2及其作为高功率型锂离子电池正极材料的性能

采用氨蒸发诱导法成功制备出纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料,借助X射线衍射（XRD）分析、扫描电镜（SEM）、透射电镜（TEM）、高分辨率透射电镜（HRTEM）、能量分散谱（EDS）和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能. 研究表明该方法制备出的材料具有良好的α-NaFeO₂层状结构,阳离子混排程度低. 纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道. 在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16 和131.23mAh·g^-1. 说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中.     

Effect of lithium boron oxide glass coating on the electrochemical performance of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript>

The effect of the lithium boron oxide glass coating on the electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ has been investigated via solution method. The morphology, structure, and electrochemical properties of the bare and coated LiNi_1/3Co_1/3Mn_1/3O₂ are characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and charge–discharge tests. The results showed that the lattice structure of LiNi_1/3Co_1/3Mn_1/3O₂ is not changed after coating. The coating sample shows good high-rate discharge performance (148 mAh g⁻¹ at 5.0 C rate) and cycling stability even at high temperature (with the capacities retention about 99% and 87% at room and elevated temperature after 50 cycles). The Li⁺ diffusion coefficient is also largely improved, while the charge transfer resistance, side reactions within cell, and the erosion of Hydrofluoric Acid all reduced. Consequently, the good electrochemical performances are obtained.     

Improvement of high-voltage cycling behavior of Li(Ni1/3Co1/3Mn1/3)O2 cathodes by Mg, Cr, and Al substitution

To improve the electrochemical properties of Li[Ni_1/3Co_1/3Mn_1/3]O₂ at high charge end voltage (4.6 V), a series of the mixed transition metal compounds, Li(Ni_1/3Co_{1/3 − x} Mn_1/3M _x )O₂ (M = Mg, Cr, Al; x = 0.05), were synthesized via hydroxide coprecipitation method. The effects of doping Mg, Cr, and Al on the structure and the electrochemical performances of Li[Ni_1/3Co_1/3Mn_1/3]O₂ were compared by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge–discharge tests, and electrochemical impedance spectroscopy. The XRD results show that all the samples keep layered structures with R3m space group as the Li[Ni_1/3Co_1/3Mn_1/3]O₂. SEM images show that all the compounds have spherical shapes and the Cr-doped sample has the largest particle size. Furthermore, galvanostatic charge–discharge tests confirm that the Cr-doped electrode shows improved cycling performance than the undoped material. The capacity retention of Li(Ni_1/3Co_{1/3 − 0.05}Mn_1/3Cr_0.05)O₂ is 97% during 50 cycles at 2.8∼4.6 V. The improved cycling performance at high voltage can be attributed to the larger particle size and the prevention of charge transfer resistance (R _ct) increase during cycling.     

Synthesis of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> nanoparticles by modified Pechini method and their enhanced rate capability

Layered LiNi_1/3Co_1/3Mn_1/3O₂ nanoparticles were prepared by modified Pechini method and used as cathode materials for Li-ion batteries. The pyrolytic behaviors of the foamed precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). Structure, morphology and electrochemical performance characterization of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron macroscopy(SEM), Brunauer-Emmett-Teller (BET) specific surface area and charge–discharge tests. The results showed that the samples prepared by modified Pechini method caclined at 900 °C for 10 h were indexed to pure LiNi_1/3Co_1/3Mn_1/3O₂ with well hexagonal structure. The particle size was in a range of 100–300 nm. The specific surface area was larger than that of the as-obtained sample by Pechini method. Initial discharge capacity of 163.8 mAh/g in the range 2.8–4.4 V (vs. Li/Li⁺) and at 0.1C for LiNi_1/3Co_1/3Mn_1/3O₂ prepared by modified Pechini method was obtained, higher than that of the sample prepared by Pechini method (143.5 mAh/g). Moreover, the comparison of electrochemical results at different current rates indicated that the sample prepared by modified Pechini method exhibited improved rate capability.     

A study on carbon-coated LiNi1/3Mn1/3Co1/3O2 cathode material for lithium secondary batteries

The surface of LiNi_1/3Mn_1/3Co_1/3O₂ was coated with amorphous carbon to enhance the conductivity of the material. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. When carbon was coated on the surface, the LiNi_1/3Mn_1/3Co_1/3O₂ cathode material showed an improved rate capability, thermal stability, and cycle performance.     

Comparison of structure and electrochemical properties for 5 V LiNi0.5Mn1.5O4 and LiNi0.4Cr0.2Mn1.4O4 cathode materials

Spinel LiNi_0.5Mn_1.5O₄ and LiMn_1.4Cr_0.2Ni_0.4O₄ cathode materials have been successfully synthesized by the sol–gel method using citric acid as a chelating agent. The structure and electrochemical performance of these as-prepared powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the galvanostatic charge–discharge test in detail. XRD results show that there is a small Li _y Ni_1-y O impurity peak placed close to the (4 0 0) line of the spinel LiNi_0.5Mn_1.5O₄, and LiMn_1.4Cr_0.2Ni_0.4O₄ has high phase purity, and the powders are well crystallized. SEM indicates that LiMn_1.4Cr_0.2Ni_0.4O₄ has a slightly smaller particle size and a more regular morphological structure with narrow size distribution than those of LiNi_0.5Mn_1.5O₄. Galvanostatic charge–discharge testing indicates that the initial discharge capacities of LiMn_1.4Cr_0.2Ni_0.4O₄ and LiNi_0.5Mn_1.5O₄ cycled at 0.15 C are 129.6 and 130.2 mAh g⁻¹, respectively, and the capacity losses compared to the initial value, after 50 cycles, are 2.09% and 5.68%, respectively. LiMn_1.4Cr_0.2Ni_0.4O₄ cathode has a higher electrode coulombic efficiency than that of the LiNi_0.5Mn_1.5O₄ cathode, implying that Ni and Cr dual substitution is beneficial to the reversible intercalation and de-intercalation of Li⁺.     

Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Synthesis conditions, crystal structures, and magnetic properties of quasi-one-dimensional complex oxides Ca₃CuMnO₆ (space group P-1, z=4, triclinic cell) and Ca₃Co_1+xMn_1−xO₆ with x=0, 0.25, 1.0 (structural type K₄CdCl₆, space group R-3c, z=6) are presented. The crystal structures of Ca₃CoMnO₆ and Ca₃CuMnO₆ were refined using neutron and combined X-ray and neutron diffraction analysis, respectively. The interatomic distances in oxygen polyhedra were found. In contrast to ferromagnetic Ca₃Co₂O₆ (T_c=24 K), manganese-containing phases Ca₃Co_1+xMn_1−xO₆ are characterized by antiferromagnetic interactions with Neel temperatures 18 K (x=0.25) and 13 K (x=0). For Ca₃CuMnO₆T_N was established to be 6 K.     

Ge4+、Sn4+掺杂尖晶石LiMn2O4的合成与电化学表征

使用Ge⁴⁺、Sn⁴⁺作为掺杂离子, 通过高温固相法制备四价阳离子掺杂改性的尖晶石LiMn₂O₄材料. X射线衍射(XRD)和扫描电子显微镜(SEM)分析表明, Ge⁴⁺离子取代尖晶石中Mn⁴⁺离子形成了LiMn_2-xGe_xO₄ (x=0.02,0.04, 0.06)固溶体; 而Sn⁴⁺离子则以SnO₂的形式存在于尖晶石LiMn₂O₄的颗粒表面. Ge⁴⁺离子掺入到尖晶石LiMn₂O₄材料中, 抑制了锂离子在尖晶石中的有序化排列, 提高了尖晶石LiMn₂O₄的结构稳定性; 而在尖晶石颗粒表面的SnO₂可以减少电解液中酸的含量, 抑制酸对LiMn₂O₄活性材料的侵蚀. 恒电流充放电测试表明, 两种离子改性后材料的容量保持率均有较大幅度的提升, 有利于促进尖晶石型LiMn₂O₄锂离子电池正极材料的商业化生产.     

Determination of lithium and transition metals in Li1Ni1/3Co1/3Mn1/3O2 (NCM) cathode material for lithium‐ion batteries by capillary electrophoresis

In this work, we present a novel electrophoretic method that was developed for the determination of lithium and transition metals in LiNi_1/3Co_1/3Mn_1/3O₂ cathode material after microwave digestion. The cations in the digested LiNi_1/3Co_1/3Mn_1/3O₂ material were separated by CE and the element content was determined by UV/Vis detection. To characterize the precision of the measurements, the RSDs and concentrations were calculated and compared to those obtained with ICP‐optical emission spectrometry (ICP‐OES). Furthermore, a certified reference material (BCR 176R —fly ash) was investigated for all techniques. For active material components, the LOD and LOQ were determined. The LODs and LOQs for the metals determined by CE were as follows: lithium (LOD/LOQ): 17.41/62.70 μg/L, cobalt (LOD/LOQ): 348.4/1283 μg/L, manganese (LOD/LOQ): 540.2/2095 μg/L, and nickel (LOD/LOQ): 838.0/2982 μg/L. Recovery rates for lithium were in the range of 95–103%. It could be proven that with the new technique, the results for the determination of the lithium content of active material were comparable with those obtained by ICP‐OES and ion chromatography. Furthermore, the recovery rates of the transition metals were determined to be between 96 and 110% by CE and ICP‐OES.     

Synthesis and characterization of LiNi1/3Co1/3Mn1/3O2 cathode material for rechargeable lithium batteries by polyacrylic acid-assisted sol–gel method

Nanocrystalline LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials are synthesized by sol–gel method using polyacrylic acid as a chelating agent. The effects of the calcination temperature and calcination time on the structure, morphology, and electrochemical performances of the LiNi_1/3Co_1/3Mn_1/3O₂ electrode materials are investigated by X-ray diffraction, scanning electron microscopy and charge–discharge cycling test, respectively. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performance. The results show that the nanocrystalline LiNi_1/3Co_1/3Mn_1/3O₂ with a particle size of 80 nm sintered at 700 °C for 2 h presents good α-NaFeO₂ layer structure and the best electrochemical performance. When it is discharged between 4.4 and 2.8 V at 20 mAg^?1, the initial specific capacity of the LiNi_1/3Co_1/3Mn_1/3O₂ obtained at 700 °C for 2 h is 169.2 mAhg^?1. The investigated electrode materials retain 151 mAhg^?1 after 30 cycles when cycled at 20 mAg^?1.     

碳酸盐共沉淀法可控制备超高倍率锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2

采用碳酸盐共沉淀法通过调节NH₃·H₂O用量来实现可控制备超高倍率纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料。NH₃·H₂O用量会对颗粒的形貌、粒径、晶体结构以及材料电化学性能产生较大的影响。X射线衍射（XRD）分析和扫描电镜（SEM）结果表明,随着NH₃·H₂O用量的降低,一次颗粒形貌由纳米片状逐渐过渡到纳米球状,且n_NH3·H2O：（n_Ni+n_Co+n_Mn）=1：2样品晶体层状结构最完善、Li⁺/Ni²⁺阳离子混排程度最低。电化学性能测试结果也证实了n_NH3·H2O：（n_Ni+n_Co+n_Mn）=1：2样品具有最优异的循环稳定性和超高倍率性能。具体而言,在2.7~4.3 V,1C下循环300次后的放电比容量为119 mAh·g^-1,容量保持率为81%,中值电压基本无衰减（保持率为97%）。在100C（18 Ah·g^-1）的超高倍率下,放电比容量还能达到56 mAh·g^-1,具有应用于高功率型锂离子电池的前景。此NH₃·H₂O比例值对于共沉淀法制备其他高倍率、高容量的正/负极氧化物材料具有一定的工艺参考价值。     

Insulator–metal transition in Nd0.8Na0.2Mn(1−x)CoxO3 perovskites

The electric and magnetic properties of the perovskites Nd_0.8Na_0.2Mn_(1−x)Co_xO₃ (0x0.2) prepared by the usual ceramic procedure were investigated. The insulator-to-metal-like (IM) transition, closely related to a ferromagnetic arrangement, was revealed for the composition of x=0.04 and a similar tendency was detected for x=0. The insulating behavior persists down to low temperatures for higher contents of cobalt ions in spite of the transition to the bulk ferromagnetism. The properties are interpreted in terms of the steric distortion, tilting of the Mn(Co)O₆ octahedra and the double-exchange interactions of the type Mn³⁺–O²⁻–Mn⁴⁺and Mn^3.5+δ–O²⁻–Co²⁺, respectively. Presence of antiferromagnetic domains in the ferromagnetic matrix for the most of cobalt-substituted samples is supposed.     

钠离子电池正极材料NaNi1/3Co1/3Mn1/3O2高压衰减机理

首次通过简单的固相反应合成了NaNi_1/3Co_1/3Mn_1/3O₂材料,并对其合适的电化学工作条件进行了探索。在此基础上对其在高充电电压下的衰减机理进行了研究。通过非原位XRD分析结构的变化,同时结合电化学阻抗谱等电化学手段综合分析材料在高压下的充放机理。     

Origin of the irreversible plateau (4.5 V) of Li[Li0.182Ni0.182Co0.091Mn0.545]O2 layered material

Layered LiNi_0.4Co_0.2Mn_0.4O₂, Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂, Li[Li_1/3Mn_2/3]O₂ powder materials were prepared by rheological phase method. XRD characterization shows that these samples all have analogous structure to LiCoO₂. Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ can be considered to be the solid solution of LiNi_0.4Co_0.2Mn_0.4O₂ and Li[Li_1/3Mn_2/3]O₂. Detailed information from XRD, ex situ XPS measurement and electrochemical analysis of these three materials reveals the origin of the irreversible plateau (4.5 V) of Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ electrode. The irreversible oxidation reaction occurred in the first charging above 4.5 V is ascribed to the contribution of Li[Li_1/3Mn_2/3]O₂ component, which maybe extract Li⁺ from the transition layer in Li[Li_1/3Mn_2/3]O₂ or Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂ through oxygen release. This step also activates Mn⁴⁺ of Li[Li_1/3Mn_2/3]O₂ or Li[Li_0.182Ni_0.182Co_0.091Mn_0.545]O₂, it can be reversibly reduced/oxidized between Mn⁴⁺ and Mn³⁺ in the subsequent cycles.