AlF_3包覆锂离子电池正极材料Li_(1.2)(Mn_(0.54)Ni_(0.16)Co_(0.08))O_2的制备、表征及电化学性能(英文)

采用溶胶-凝胶法合成锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2,并用Al F3对这种材料进行表面包覆改性。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)等表征材料的结构和形貌。结果表明,合成的Li1.2(Mn0.54Ni0.16Co0.08)O2具有典型的层状α-Na Fe O2结构,AlF3均匀包覆在Li1.2(Mn0.54Ni0.16Co0.08)O2材料表面,包覆层厚度为5~7 nm。电化学测试表明,包覆Al F3后材料的电化学性能得到提高,在1C倍率下,包覆的AlF3材料的首次放电容量为208.2 m A·h/g,50次循环后容量保持率为72.4%,而未包覆AlF3的材料的首次放电容量和容量保持率分别为191.7 m A·h/g和51.6%。     

AlF3包覆锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2的制备、表征及电化学性能（英文）

采用溶胶-凝胶法合成锂离子电池正极材料Li1.2(Mn0.54Ni0.16Co0.08)O2,并用Al F3对这种材料进行表面包覆改性。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电子显微镜(HRTEM)等表征材料的结构和形貌。结果表明,合成的Li1.2(Mn0.54Ni0.16Co0.08)O2具有典型的层状α-Na Fe O2结构,AlF3均匀包覆在Li1.2(Mn0.54Ni0.16Co0.08)O2材料表面,包覆层厚度为5~7 nm。电化学测试表明,包覆Al F3后材料的电化学性能得到提高,在1C倍率下,包覆的AlF3材料的首次放电容量为208.2 m A·h/g,50次循环后容量保持率为72.4%,而未包覆AlF3的材料的首次放电容量和容量保持率分别为191.7 m A·h/g和51.6%。     

正极材料Li（Ni1／3Co1／3-xMn1／3）MxO2（M=Ti，Mg）的合成及性能

采用草酸盐前驱体合成Ti4+、Mg2+掺杂正极材料Li(Ni1/3Co1/3-xMn1/3)MxO2(M=Ti, Mg).利用XRD和SEM对其结构和形貌进行表征,并采用循环伏安、交流阻抗、恒流/恒压充放电测试其电化学性能.结果表明:Ti4+、Mg2+掺杂后晶胞体积增大,大倍率充放电时LiNi1/3Co1/3Mn1/3O2的电化学反应阻抗Rct降低,其大倍率充放电性能得到改善,Ti4+掺杂效果更好;当掺杂量x＝0.025时,材料晶型完整,具有单一的a-NaFeO2层状结构;1C倍率时Li(Ni1/3Co1/3-0.025Mn1/3)Ti0.025O2的第二循环放电容量为143.2 mA-h/g,2C时为128.0 mA-h/g,经100次循环后容量分别为132.5和115.8 mA-h/g,容量保持率为92.53%和90.47%.     

Zn掺杂对LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2结构与电化学性能的影响

用溶胶凝胶法制备了Li Ni1/3Co1/3-x Mn1/3Znx O2(x=0,1/24,2/24,4/24)锂离子电池正极材料。由X射线衍射和扫描电镜对其分析结果表明,Zn掺杂不改变Li Ni1/3Co1/3Mn1/3O2的α-Na Fe O2层状结构,当掺杂量达到4/24时,杂相产生。电化学研究表明,当Zn掺杂量为2/24时,Li Ni1/3Co1/3Mn1/3O2首次放电容量由未掺杂的169.2 m Ah·g-1降低为160.1m Ah·g-1,但循环性能明显提高,30次循环后的容量保持率由未掺杂的89.2%升至97%。并且在20、40、60和80 m A·g-1不同的电流密度下继续循环20次后,当再次恢复到20 m A·g-1的电流密度时,放电容量可恢复到150.3 m Ah·g-1。     

层状LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料的多元掺杂改性

采用共沉淀法制备锂离子电池掺杂型层状LiNi1/3Co1/3Mn1/3-xMxO2(M=Mg、Al、Cr)正极材料。采用X射线衍射、扫描电镜、充放电实验和交流阻抗实验对LiNi1/3Co1/3Mn1/3-xMxO2正极材料的结构、形貌、电化学性能以及动力学参数进行表征。结果表明:当掺杂量x=0.05时,Mg2+、Al3+掺杂的正极材料在2.8～4.3V、0.1C下的首次放电比容量分别为139.2、151.6mA·h/g,20次循环后的容量保持率分别为98.8%和96.7%;掺杂Mg2+或Al3+均能提高LiNi1/3Co1/3Mn1/3O2的交换电流密度和锂离子扩散系数。结合实验结果和掺杂离子的离子半径和化学稳定性,解释了掺杂离子在LiNi1/3Co1/3Mn1/3O2晶格中的占位及其在充放电过程中的作用。     

Li掺杂对AB5型稀土贮氢合金相结构和电化学性能的影响

采用粉末烧结法,制备了一系列掺杂Li的AB5型稀土贮氢合金,并研究了Li掺杂量对贮氢合金MlNi3.55Mn0.40Al0.30Co0.70Lix相结构和电化学性能影响.结果表明:随Li掺杂量的增加,合金的晶胞参数c、c/a和晶胞体积V也随之增大;适量Li(x≤0.20)掺杂对合金的电化学容量有所提高,MlNi3.55 Mn0.40 Al0.30 Co0.70 Li0.20合金的0.2C放电容量达到273.53 mA·h/g;掺杂Li能改善合金的高倍率放电性能,当Li的含量为0.20～0.30时,合金的高倍率放电性能最好;掺杂Li能不同程度地提高贮氢合金的充放电循环稳定性,当x=0.20时,其循环性能最好,MlNi3.55Mn0.40Al0.30Co0.70Li0.20合金200次循环的电容与最大电容的比率(S200)达86.2%,但当Li掺杂量大于0.50时,合金的循环性能反而下降.     

锂离子电池富锂材料Li[Li0.2Ni0.2Mn0.6]O2的制备及掺杂改性

以乙酸盐为原料,采用喷雾干燥法制备层状α-NaFeO2结构的富锂正极材料Li[Li0.2Ni0.2Mn0.6]O2及掺杂Cr的Li[Li0.2Ni0.15Cr0.1Mn0.55]O2。采用X射线衍射、扫描电镜、半电池充放电和电化学阻抗谱等方法研究材料的物相、结构、形貌及电化学性能。结果表明:Cr掺杂使材料的颗粒变粗,但不改变材料的结构,而使材料的层状特征更为明显;Cr掺杂后材料的电化学性能得到明显改善,电荷转移阻抗Rct从275.0降低到105.0,循环稳定性和倍率性能均有所改善,Li[Li0.2Ni0.15Cr0.1Mn0.55]O2材料1C倍率下的放电比容量为140.0 mA.h/g,循环50次后放电比容量为133.7 mA.h/g,远高于未掺杂Cr材料的比容量,未掺杂Cr材料在1C倍率下放电比容量为107.1mA.h/g,循环50次后放电比容量为102.1 mA.h/g。     

锰掺杂对锂离子电池正极材料Li3V2（PO4）3/C性能的影响（英文）

采用溶胶-凝胶法合成Li3V2-2/3xMnx(PO4)3(0≤x≤0.12)。采用XRD、SEM、XPS、恒流充放电和电化学阻抗谱(EIS)研究Mn掺杂对Li3V2(PO4)3/C结构和电化学性能的影响。XRD研究表明:掺杂少量的Mn2+不会影响材料的结构,所有样品均具有单一相态的单斜结构(P21/n空间群)。XPS分析表明:在Li3V1.94Mn0.09(PO4)3/C中,V和Mn的化合价分别为+3和+2,原料中的柠檬酸在煅烧过程中分解成C而残留在Li3V1.94Mn0.09(PO4)3/C中。电化学测试表明:掺杂Mn改善了电极材料的循环性能和倍率性能,正极材料Li3V1.94Mn0.09(PO4)3/C表现出最好的循环稳定性和倍率性能。在40mA/g的放电电流密度下,循环100次后,Li3V1.94Mn0.09(PO4)3/C的放电容量从158.8mA·h/g衰减到120.5mA·h/g,容量保持率为75.9%,而未掺杂样品的放电容量从164.2mA·h/g衰减到72.6mA·h/g,容量保持率为44.2%。当放电电流密度增加到1C时,Li3V1.94Mn0.09(PO4)3/C的初始放电容量仍能达到146.4mA·h/g,循环100次后,放电容量保持为107.5mA·h/g。EIS测试表明,掺杂适量的Mn2+减小了电荷转移阻抗,这有利于Li+的脱嵌。     

V~(3+)掺杂Li_2FeSiO_4正极材料的制备与电化学性能

采用机械-固相烧结法制备了V3+掺杂的锂离子正极材料Li2Fe(1-x)VxSi O4(其中x=0.05,0.1,0.15)。通过X射线衍射、扫描电镜、恒流充放电测试及EIS测试等方法研究了所制备样品的结构、形貌及电化学性能。结果表明:掺杂V3+进入了Li2Fe Si O4晶格内部,材料的粒径分布在200~500 nm;恒流充放电测试显示,随掺钒量增加,样品的放电平台有所下降,这说明材料的阻抗有所增加,这与EIS的测试结果相一致;样品的放电平台随掺钒量的增加而更加的明显和平坦,稳定的放电平台有利于锂离子电池的实际应用。     

锂离子电池正极材料LiCo0.3Ni0.7-xSrxO2的合成及其电化学性能

在空气气氛中合成了LiCo0.3Ni0.7-xSrxO2二元掺杂锂离子电池正极材料,研究了不同掺Sr2 量对材料的结构与电化学性能的影响,用XRD、SEM及电性能测试考察了材料的结构、形貌及其电化学性能.结果表明:Sr2 的掺入量对材料的结构与电化学性能影响较大,随着掺Sr2 量的增加,X射线衍射图中材料的特征峰向低角度飘移,晶胞参数a和c增大,晶胞体积增大; 电性能测试结果表明:适量的掺Sr2 有利于提高材料中Li 的扩散能力,抑制John-Teller效应,降低阳离子混排现象,提高材料的电化学稳定性,当x=0.003,LiCo0.3Ni0.697-Sr0.003O2显示出较优的电化学性能,首次放电容量为162mA·h·g-1,首次放电效率为90.6%; 40次循环后其放电容量仍为153mA·h·g-1,容量损失为7%,显示出较好的循环稳定性.     

Structural characterization of layered LiNi0.85−xMnxCo0.15O2 with x = 0, 0.1, 0.2 and 0.4 oxide electrodes for Li batteries

We report the synthesis of LiNi_0.85−xCo_0.15Mn_xO₂ positive electrode materials from Ni_0.85−xCo_0.15Mn_x(OH)₂ and Li₂CO₃. XRD and XPS are used to study the effect of Mn-doping on the microstructures and oxidation states of the LiNi_0.85−xCo_0.15Mn_xO₂ materials. The analysis shows that Mn-doping promotes the formation of a single phase. With increasing substitution of Mn ions for Ni ions, the lattice parameter a decreases, while the lattice parameters c and c/a increase. XPS revealed that the oxidation states of Ni, Co and Mn in LiNi_0.85−xCo_0.15Mn_xO₂ compounds (where x = 0.1, 0.2 and 0.4) were +2/+3, +3 and +4. The substitution of Mn ions for Ni ions induces a decrease in the average oxidation state of Ni. Because the substitution of Mn for Ni ions is complex, the extent of the changes between the lattice parameter and L_M-O differ. The occupation of Ni in Li sites is affected by the ordering of Mn⁴⁺ with Ni²⁺ and Mn⁴⁺ with Li⁺.     

Enhanced cycling stability of Mg–F co-modified LiNi0.6Co0.2Mn0.2–yMgyO2–zFz for lithium-ion batteries

The layered LiNi_0.6Co_0.2Mn_0.2–yMg_yO_2–zF_z (0≤y≤0.12, 0≤z≤0.08) cathode materials were synthesized by combining co-precipitation method and high temperature solid-state reaction, with the help of the ball milling, to investigate the effects of F–Mg doping on LiNi_0.6Co_0.2Mn_0.2O₂. Compared with previous studies, this doping treatment provides substantially improved electrochemical performance in terms of initial coulombic efficiency and cycle performance. The LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 electrode delivers an high capacity retention of 98.6% during the first cycle and a discharge capacity of 189.7 mA·h/g (2.8–4.4 V at 0.2C), with the capacity retention of 96.3% after 100 cycles. And electrochemical impedance spectroscopy(EIS) results show that Mg–F co-doping decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance. It is demonstrated that LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 is a promising cathode material for lithium-ion batteries for excellent electrochemical properties.     

Phase transition of lithiated-spinel Li2Mn2O4 at high temperature

1 Introduction Lithium manganese oxides are the most attractive cathode materials for rechargeable lithium-ion batteries because of their low-cost and less toxicity when compared with either cobaltates or nickelates[1?3]. Among these oxides, the spinel-fr…     

Effect of the impurity LixNi1−xO on the electrochemical properties of 5 V cathode material LiNi0.5Mn1.5O4

The formation of impurity Li_xNi_1−xO when synthesizing spinel LiNi_0.5Mn_1.5O₄ using solid state reaction method, and its influence on the electrochemical properties of product LiNi_0.5Mn_1.5O₄ were studied. The secondary phase Li_xNi_1−xO emerges at high temperature due to oxygen deficiency for LiNi_0.5Mn_1.5O₄ and partial reduction of Mn⁴⁺ to Mn³⁺ in LiNi_0.5Mn_1.5O₄. Annealing process can diminish oxygen deficiency and inhibit impurity Li_xNi_1−xO. The impurity reduces the specific capacity of product, but it does not have obvious negative effect on cycle performance of product. The capacity of LiNi_0.5Mn_1.5O₄ that contains Li_xNi_1−xO can deliver about 120 mAh g⁻¹.     

Effect of lithium content on electrochemical property of Li1+x(Mn0.6Ni0.2Co0.2)1-xO2 (0≤x≤0.3) composite cathode materials for rechargeable lithium-ion batteries

In order to confirm the optimal Li content of Li-rich Mn-based cathode materials (a fixed mole ratio of Mn to Ni to Co is 0.6:0.2:0.2), Li_1+x(Mn_0.6Ni_0.2Co_0.2)_1-xO₂ (x=0, 0.1, 0.2, 0.3) composites were obtained, which had a typical layered structure with and C2/m space group observed from X-ray powder diffraction (XRD). Electron microscopy micrograph (SEM) reveals that the particle sizes in the range of 0.4-1.1 μm increase with an increase of x value. Li_1.2(Mn_0.6Ni_0.2Co_0.2)_0.8O₂ sample delivers a larger initial discharge capacity of 275.7 mA·h/g at the current density of 20 mA/g in the potential range of 2.0–4.8 V, while Li_1.1(Mn_0.6Ni_0.2Co_0.2)_0.9O₂ shows a better cycle performance with a capacity retention of 93.8% at 0.2C after 50 cycles, showing better reaction kinetics of lithium ion insertion and extraction.     

一步双修饰策略提高富镍层状氧化物正极材料的电化学性能（英文）

提出一种从表面到体相的一步整体改性策略,同步合成Nb掺杂和LiNbO₃包覆的LiNi_0.83Co_0.12Mn_0.05O₂(NCM)正极材料。LiNbO₃包覆层可以调控界面并促进锂离子扩散;更强的Nb—O键能有效抑制Li⁺/Ni²⁺阳离子混排,提高晶体结构稳定性,从而有助于缓解Li⁺脱出/嵌入过程中晶格参数的各向异性变化。结果表明:双修饰材料表现出较好的结构稳定性和优异的电化学性能。最佳样品NCM-Nb2在2.7～4.3 V之间以1C循环100次后,容量保持率为90.78%,而原始样品容量保持率仅为67.90%;同时,在10C下具有149.1 mA·h/g的更高倍率性能,这些结果突显了一步双修饰策略协同提高富镍层状氧化物正极材料电化学性能的可行性。     

不同锂源对高温固相法制备NCM811正极材料储锂性能的影响

采用4种不同的锂盐(LiOH.H₂O、Li₂CO₃、LiNO₃、CH₃COOLi),以高温固相法制备了LiNi_0.8Co_0.1Mn_0.1O₂正极材料。利用X射线粉末衍射(XRD)和场发射电子显微镜(FESEM)对所制LiNi_0.8Co_0.1Mn_0.1O₂材料的微观结构进行了表征,发现所有合成的LiNi_0.8Co_0.1Mn_0.1O₂样品尺寸均为微米级大小,具有层状结构(R-3m空间群)。电化学测试结果表明采用不同锂源制备的LiNi_0.8Co_0.1Mn_0.1O₂样品的电化学性能差别很大。其中采用LiOH?H₂O为锂源,经500 °C预烧结6 h后,在800 °C下烧结16 h获得的样品锂镍混排程度最低,电化学性能最佳。例如,在0.1 C(1 C=180 mA/g)倍率下其可逆比容量高达206.2 mA.h/g,在10 C大倍率下,其可逆比容量仍保持有80.9 mA.h/g;在0.5 C倍率下100次充放电循环过程中,最高放电比容量为176.2 mA.h/g,平均放电比容量为140.1 mA.h/g。动力学及电极稳定性分析发现,LiOH?H₂O制备的样品的电化学可逆性最好,Li^₊扩散系数最大,充放电循环过程中结构稳定性最好。     

Enhanced cycling stability of La modified LiNi0.8–xCo0.1Mn0.1LaxO2 for Li-ion battery

A series of layered LiNi_0.8–xCo_0.1Mn_0.1La_xO₂ (x=0, 0.01, 0.03) cathode materials were synthesized by combining co-precipitation and high temperature solid state reaction to investigate the effect of La-doping on LiNi_0.8Co_0.1Mn_0.1O₂. A new phase La₂Li_0.5Co_0.5O₄ was observed by XRD, and the content of the new phase could be determined by Retiveld refinement and calculation. The cycle stability of the material is obviously increased from 74.3% to 95.2% after La-doping, while the initial capacity exhibits a decline trend from 202 mA·h/g to 192 mA·h/g. The enhanced cycle stability comes from both of the decrease of impurity and the protection of newly formed La₂Li_0.5Co_0.5O₄, which prevents the electrolytic corrosion to the active material. The CV measurement confirms that La-doped material exhibits better reversibility compared with the pristine material.     

Effects of Na+ doping on crystalline structure and electrochemical performances of LiNi0.5Mn1.5O4 cathode material

Pristine LiNi_0.5Mn_1.5O₄ and Na-doped Li_0.95Na_0.05Ni_0.5Mn_1.5O₄ cathode materials were synthesized by a simple solid-state method. The effects of Na⁺ doping on the crystalline structure and electrochemical performance of LiNi_0.5Mn_1.5O₄ cathode material were systematically investigated. The samples were characterized by XRD, SEM, FT-IR, CV, EIS and galvanostatic charge/discharge tests. It is found that both pristine and Na-doped samples exhibit secondary agglomerates composed of well-defined octahedral primary particle, but Na⁺ doping decreases the primary particle size to certain extent. Na⁺ doping can effectively inhibit the formation of Li_xNi_1–xO impurity phase, enhance the Ni/Mn disordering degree, decrease the charge-transfer resistance and accelerate the lithium ion diffusion, which are conductive to the rate capability. However, the doped Na⁺ ions tend to occupy 8a Li sites, which forces equal amounts of Li⁺ ions to occupy 16d octahedral sites, making the spinel framework less stable, therefore the cycling stability is not improved obviously after Na⁺ doping.