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).     

湿化学法合成LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2及其表征(英文)

利用琥珀酸为鳌合剂的湿化学法成功合成了一系列锂离子电池正极材料LiNi1/3Mn1/3Co1/3O2,在合成过程中改变琥珀酸与金属离子摩尔比(R)并研究了这一参数对合成LiNi1/3Mn1/3Co1/3O2材料物理及电化学性质的影响.采用热重、X射线衍射、Rietveld精修、扫描电镜以及超导量子干涉仪对反应机理、材料的结构、形貌以及磁学性质进行了详细表征.得到最佳合成条件为R=1,此时LiNi1/3Mn1/3Co1/3O2的阳离子混排度最低.此外,通过Rietveld精修得到该材料阳离子混排度的结果与通过磁学方法得到的结果定量相符,如对于在R=1条件下合成的样品,Rietveld精修结果显示其阳离子混排度为1.85%,而超导量子干涉仪的测试结果为1.80%.当充放电区间为3.0-4.3V,电流密度为0.2C(1C=160mA·g-1)时,该样品的首次放电容量为161mAh·g-1,库仑效率为93.1%,经过50次循环后,容量保持率可达91.3%.     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺,在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3.采用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析.结果表明,Y2O3包覆并没有改变LiCO1/3Ni1/3Mn1/3O2的晶体结构,只存在于LiCo1/3Ni1/3Mn1/3O2的表面;与未包覆的材料相比,Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量.CV测试表明,包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

纳米MgO掺杂改善LiNi1/3Co1/3Mn1/3O2正极材料

将氢氧化物共沉淀法制备的(Ni_1/3Co_1/3Mn_1/3)（OH）₂在500℃热处理5 h得到具有尖晶石结构、纳米尺寸的氧化物M₃O₄(M=Ni_1/3Co_1/3Mn_1/3).将其与LiOH及不同量的纳米MgO混合均匀,并在850℃热处理24 h制备了Li(Ni_1/3Co_1/3Mn_1/3)_1/xMg_xO₂（x=0,0.01,0.02,0.03,0.04,0.05）正极村料.随着Mg掺杂量的增大,正极材料的晶胞参数增大;少量的Mg掺杂增大了锂离子的扩散系数,而过度掺杂却使锂离子扩散系数有所降低,其中Li(Ni_1/3Co_1/3Mn_1/3)_0.98Mg_0.02O₂的锂离子扩散系数最大,其脱出和嵌入扩散系数分别为D_Li-dein=29.20×10^-11cm²·S^-1和D_Li-in=4.760×10^-11cm²·s^-1;其以3C倍率充放电的平均放电比容量为139.3 mAh·g^-1,比未掺杂的原粉约高9.5 mAh·g^-1;另外其循环性能也得到了大幅度改善.     

TiO2包覆对LiCO1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3MnO2的循环件能,采用浸渍-水解法对其进行TiO2包覆.用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流允放电测试研究包覆材料的结构和电化学性能.TiO2仅在材料表面形成包覆层,并未改变材料的结构.TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能,TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%,而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%.包覆后的材料在2.0C下循环12周后的容最没有衰减,而未包覆的材料容量保持率仅为94.4%.EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高.循环后材料的XRD和ICP-OES测试表明,包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

CoAl2O4包覆LiNi1/3Co1/3Mn1/3O2的电化学性能

通过共沉淀法制得类球形锂离子电池正极材料LiNi_1/3Co_1/3Mn_1/3O₂,并用非水相共沉法对其进行CoAl₂O₄包覆得到LNCMO(x). 采用X射线衍射（XRD）、扫描电子显微术（SEM）和透射电子显微术（TEM）测试材料的结构和观察材料形貌. 结果表明,CoAl₂O₄在材料表面形成8 nm均匀包覆层,未改变主体材料的结构. 电化学性能测试表明,1%（by mass）CoAl₂O₄包覆量的LiNi1/3Co1/3Mn1/3O2材料（LNCMO(1)）高充电电压（3.0 ~ 4.6 V,150 mA·g^-1）100周期循环放电容量保持率为93.7%（无包覆LNCMO(0)保持率为74.4%）;55 °C高温100周期循环容量保持率为77%（无包覆LNCMO(0)保持率17%）. XRD和电感耦合等离子体原子发射光谱（ICP-AES）测试表明,CoAl₂O₄包覆的LNCMO(x)材料可有效地减缓材料中Mn离子在电解液的溶解,提高材料结构稳定性和热稳定性.     

锂离子电池正极材料LiCo1/3 Ni1/3Mn1/3O2

镍钴锰三元材料作为锂二次电池正极材料是目前国内外研究热点。综述了三元材料近几年国内外的研究状况,重点介绍了LiCo1/3Ni1/3Mn1/3O2材料的结构与电化学性能的内在联系,探讨了不同制备方法及不同元素的掺杂改性对材料的影响,讨论了LiCo1/3Ni1/3Mn1/3O2正极材料的应用前景。     

ZnO包覆LiNi1/3Co1/3Mn1/3O2的表面结构和电化学性能

在LiNi_1/3Co_1/3Mn_1/3O₂正极材料表面包覆ZnO,通过X射线衍射（XRD）和光电子能谱（XPS）分析包覆层对正极材料表面状态的改变,并考察了改性后材料的放电容量、首次不可逆容量等电化学性能变化. 结果表明：ZnO主要存在于材料表面并影响着材料表面组成和电化学性质,材料表面镍和锰的含量随着包覆量的增加而增大;400 ^oC热处理可使过渡金属与锌在材料表面形成复合氧化物,过渡金属的结合能增大;包覆2%（by mass,下同）的ZnO可有效抑制55 ^oC下充放电时3.6 V附近的不可逆反应,提高了材料的首次库仑效率;包覆2% ZnO的电池材料在55 ^oC/0.5C的放电比容量和循环寿命最佳.     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的低温性能及动力学分析

通过高温烧结制备了锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2,并用XRD、SEM和恒流充放电对材料的结构、形貌和低温电性能进行了表征,通过线性极化、GITT和EIS等手段研究分析了低温下LiNi1/3Co1/3Mn1/3O2性能变差的原因.结果表明,-20℃时,LiNi1/3Co1/3Mn1/3O2材料的0.1、0.2、1和5 C倍率放电比容量依次为25℃时同倍率下放电比容量的83.2%、68.4%、57.2%和34.1%,放电中值电压比25℃时依次降低了0.049、0.125、0.364和0.531 V.低温充放电过程表现出明显的极化现象,其中最显著的极化来自锂离子穿过活性物质/电解液界面过程以及电荷转移过程,而非锂离子在电极材料内部的扩散过程.     

Reversible Anionic Redox Activities in Conventional LiNi1/3Co1/3Mn1/3O2 Cathodes

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium‐excessive layered‐oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi_1/3Co_1/3Mn_1/3O₂. The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high‐capacity lithium‐ion batteries.     

LiOH-LiNO3低共熔混合锂盐体系合成LiNi1/3Co1/3Mn1/3O2

The powder of LiNi1/3Co1/3Mn1/3O2 were prepared directly without artificial grinding and washing by a eutectic molten-salt mixture (0.38LiOH·H2O-0.62LiNO3) method. According to this method, the eutectic molten-salt mixture was self-mixed with precursor thoroughly at low temperature, and then sintered at a certain temperature. The tap-density of the powder obtained was 2.87 g·cm-3. The well-layered 琢-NaFeO2 structure and regular morphology were confirmed by X-ray diffraction (XRD) and scanning electronmicroscopy (SEM).XPSstudies showed that the predominant oxidation states of Ni, Co, andMn in the compound were 2+, 3+, and 4+, respectively. Cathodic behaviour was examined by charge-discharge cycling. The synthesized powder showed a reversible capacity of 160 mAh·g -1 at a specific current of 0.2C in the rang 3.0-4.3 V up to 50 cycles without noticeable capacity-fading.     

X-ray diffraction study of ceramic samples of SrCu1/3Nb1/3O3

Ceramic samples of SrCu_1/3Nb_2/3O₃, obtained either by slow cooling or by quenching from 1200°C, were studied by X-ray diffraction using the Rietveld method. The slow-cooled SrCu_1/3Nb_2/3O₃ samples contain one phase with a perovskite structure (R _B = 4.14%, tetragonal crystal symmetry, space group P4/mmm, Z = 1, a = 3.935 ?, c = 4.124 ?), its diffraction peaks being considerably broadened. The samples quenched from 1200°C contain two SrCu_1/3Nb_2/3O₃ forms with a perovskite structure: one of them is oxygen deficient (R _B = 3.37%, tetragonal crystal symmetry, space group P4/mmm, Z = 1, a = 3.9687 ?, c = 4.0718 ?), and the other has no oxygen deficiency (R _B = 3.20%, tetragonal crystal symmetry, space group P4/mmm, Z = 1, a = 3.95307 ?, c = 4.08935 ?).     

锌掺杂提高LiNi1/3Co1/3Mn1/3O2正极材料的电化学稳定性

通过共沉淀法与固相法相结合制备了掺锌的高稳定性Li(Ni_1/3Co_1/3Mn_1/3)_1-xZn_xO₂ (x=0, 0.02, 0.05)正极材料. 循环伏安(CV)曲线表明Zn掺杂使氧化峰与还原峰的电势差减小到0.09 V, 电化学阻抗谱(EIS)曲线表明Zn掺杂使电极的阻抗从266 Ω减小到102 Ω. Li⁺嵌入扩散系数从1.20×10^-11 cm²·s^-1增大到 2.54×10^-11 cm²·s^-1. Li(Ni_1/3Co_1/3Mn_1/3)_0.98Zn_0.02O₂正极材料以0.3C充放电在较高的截止电压(4.6 V)下比其他两种材料的电化学循环性能更稳定, 其第二周的放电比容量为176.2 mAh·g^-1, 循环100周后容量几乎没衰减; 高温(55 °C)下充放电循环100周, 其放电比容量平均每周仅衰减0.20%, 远小于其他两种正极材料(LiNi_1/3Co_1/3Mn_1/3O₂平均每周衰减0.54%; Li(Ni_1/3Co_1/3Mn_1/3)_0.95Zn_0.05O₂平均每周衰减0.38%). Li(Ni_1/3Co_1/3Mn_1/3)_0.98Zn_0.02O₂正极材料以3C充放电时其放电比容量可达142 mAh·g^-1, 高于其他两种正极材料. 电化学稳定性的提高归因于Zn掺杂后减小了电极的极化和阻抗, 增大了锂离子扩散系数.     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2在不同电解液中的性能研究

应用低热固相合成法制备锂离子电池正极材料L iCo1/3N i1/3Mn1/3O2.研究该材料的结构与形貌,并比较它在商品L iPF6盐和在实验室合成的L iBOB(L iB(C2O4)2)盐电解液中的电化学性能.在L iPF6/EC+DMC+DEC电解液中,该材料表现出优良的电化学性能,其于0.5C、1C、1.5C、2C、3C放电倍率的初始比容量依次为167、163、163、157、147mAh/g,电池的循环性能也较好,说明低热固相合成的材料的有较好的高倍率性能.在L iBOB/EC+DEC+DE电解液中,0.5C倍率下比容量为160 mAh/g,较之L iPF6盐电解液的相差不大,但在高倍率下的比容量有所下降.     

Effect of Various Synthesis methods on the Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2

Layered LiNi1/3Co1/3Mn1/3O2 has the isostructure of α-NaFeO2 and shows high rate capacity with stable cycleability. Furthermore, the thermal behavior of this material is milder than that of lithium nickel oxide and lithium cobalt oxide. In addition, it is expected to be stable at elevated temperatures. Therefore LiNi1/3Co1/3Mn1/3O2 may be the most promising cathode materials of lithium-ion secondary battery.In this research, LiNi1/3Co1/3Mn1/3O2 was prepared by solid-state reaction, sol-gel method and mixed hydroxide method. The influences of synthesis method on the physical and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge cycling cyclic voltammetry and differential scanning calorimetry (DSC). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the LiNi1/3Co1/3Mn1/3O2 compound are 2+, 3+ and 4+. From the voltage profile and cyclic voltammetry, the redox processes occurring at ～3.8V and ～4.5V are assigned to the Ni2+/Ni3+ and Co3+/Co4+ couples, respectively. Different preparation methods result in the difference in morphology (shape, particle size and specific surface area) and electrochemical behaviors. A sample prepared by solid-state reaction has the worst electrochemical performance among these three methods. Sample synthesized by mixed hydroxide method displays the better rate capacity than that prepared by sol-gel method, while the capacity retention of sample prepared by sol-gel method is superior to that synthesized by mixed hydroxide method.     

TiO2包覆对LiCo1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3Mn1/3O2的循环性能, 采用浸渍-水解法对其进行TiO2包覆. 用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流充放电测试研究包覆材料的结构和电化学性能. TiO2仅在材料表面形成包覆层, 并未改变材料的结构. TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能, TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%, 而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%. 包覆后的材料在2.0C下循环12周后的容量没有衰减, 而未包覆的材料容量保持率仅为94.4%. EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高. 循环后材料的XRD和ICP-OES测试表明, 包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

Li[Ni1/3Mn1/3Co1/3]O2掺杂Mo研究

采用高温固相合成法制备了Li[Ni_(1－x)/3Mn_(1－x)/3Co_(1－x)/3Mo_x]O₂ (x＝0, 0.005, 0.01, 0.02). 对它们进行了XRD, SEM, 循环伏安及充放电容量测试, 结果发现, 掺杂x＝0.01 Mo的样品具有较高的嵌锂容量和良好的循环稳定性, 在20 mA/g放电电流密度和2.3～4.6 V的电压范围内具有211.6 mAh/g的首次放电比容量, 循环50周后放电比容量仍能达到185.9 mAh/g, 容量损失为12.1%.     

Thermal Behavior Investigation of LiNi1/3Co1/3Mn1/3O2-Based Li-ion Battery under Overcharged Test

Thermal behavior of its components such as separator, electrolyte, cathode, anode, and each binder were investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG) to explain thermal runaway mechanism of Li‐ion battery under overcharged test. DSC results indicated the decomposition reaction temperature of SEI (solid electrolyte interface) layer in anode was at about 126°C. It was found that heat generation in anode under normal charged state increased obviously with the increasing of charged voltage. When the battery was overcharged to 4.6 V or 5.0 V, the onset temperature and heat generation of thermal reaction in anode changed a little, while those in cathode had large increase. It was proposed that thermal behavior in cathode mainly caused by the reaction of electrolyte with evolutional oxygen played a key role to thermal runaway for the studied Li‐ion battery under overcharged test.     

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.