锂离子电池正极材料层状LiMnO2的研究进展

对近年来圆外层状氧化锰锂正极材料的研究进展进行了综述。详细介绍了正交和单斜同质多晶层状氧化锰锂的晶体结构，合成方法及其电化学特性。开发新的合成方法以及多组分掺杂改性以提高英应用性仍是今后．层状氧化锰锂的研究发展方向。     

TiO2(B)表面修饰富锂层状氧化物Li(Li0.17Ni0.2Mn0.58Co0.05)O2正极材料

采用喷雾干燥法和沉淀法, 制备了表面修饰TiO₂(B) (2wt%、4wt%、6wt%和8wt%)的富锂层状氧化物Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂正极材料。X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)结构测试分析结果表明, 修饰TiO₂(B)后样品的体相结构仍然保持初始样品的层状结构, 仅氧化物颗粒表面附着有少量TiO₂(B)纳米晶。示差扫描量热测试(DSC)表明, 与初始样品比较, 修饰TiO₂(B)后样品的热稳定性得到明显改善。在2.0~4.8 V范围内进行恒流电化学性能测试。研究显示, 在0.1C(1C=300 mA/g)倍率下, 修饰4wt%TiO₂(B)样品的首次放电比容量可达296.4 mAh/g, 首次库伦效率则由初始样品的77.7%提升到修饰TiO₂(B)后样品的84.3%, 100周循环后电极容量保持率由初始样品的69.5%提升到修饰TiO₂(B)后样品的80.2%。即使在阶梯倍率的2C倍率下, 修饰4wt%TiO₂(B)的样品仍具有较高的电化学容量(166.5 mAh/g)。以上研究结果表明, 表面修饰TiO₂(B)纳米晶可以显著改善富锂层状氧化物Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂的热稳定性和电化学性能。     

SrF_2包覆锂离子电池用正极材料0.5Li_2MnO_3·0.5LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的电化学性能研究

采用化学沉淀法在富锂层状正极材料0.5Li2MnO3?0.5LiNi1/3Co1/3Mn1/3O2表面包覆一层SrF2薄膜。利用X射线衍射仪、扫描电子显微镜、透射电子显微镜和充放电测试技术研究SrF2包覆对正极材料的晶体结构、微观形貌和电化学性能的影响。结果表明,正极材料表面包覆了一层厚约20~30nm的SrF2膜。包覆SrF2后,材料的首次库仑效率从70.5%增加到72.7%,且包覆改善了材料的倍率性能和循环性能。随着充放电倍率的增大,包覆样与未包覆样的放电容量差值随之增大;包覆样循环40次后容量保持率为95.1%,高于未包覆样84.8%的容量保持率。     

Mg^2+掺杂对Li1.2Mn0.6Ni0.2O2正极材料性能的影响EI北大核心CSCD

采用燃烧合成法,制备Mg^2+掺杂的锂离子电池正极材料Li1.2Mn0.6Ni0.2O2。通过X射线衍射仪、拉曼光谱、扫描电子显微镜对所制备样品分别进行物相结构和形貌表征,并测试其电化学性能。结果表明:所制备样品具有良好的六方层状结构,粉体呈类球形形貌。通过Mg^2+掺杂,能够有效提高Li1.2Mn0.6Ni0.2O2材料的首次库仑效率、循环稳定性和高倍率容量。当Mg^2+掺杂量为0.02时,电池样品表现出良好的电化学性能。     

“锂离子电池正极材料锰酸锂的合成”项目通过鉴定

我国锰酸锂合成技术及用该技术生产的锰酸锂材料达到国际先进水平。这是以戴永年院士为组长的专家组对“锂离子电池正极材料锰酸锂的合成”项目鉴定后得出的一致结论。     

工艺条件对层状Li（Ni1／3Co1／3Mn1／3）O2的结构及电化学性能的影响

采用共沉淀法合成了均匀的N1/3Co1/3Mn1/3（OH）2前驱体，通过配锂煅烧制备出结晶良好的层状Li（Ni1／3Co1／3Mn1／3）O2正极材料。讨论了反应条件（如pH值、氨水浓度及烧结温度）对材料结构及性能的影响，确定了最佳的共沉淀反应合成工艺条件。应用XRD、SEM分析材料的组成及结构特点，采用电化学分析方法表征材料的性能。XRD结果表明，采用共沉淀法合成了结晶良好的层状Li（Ni1／3Co1／3Mn1／3）O2正极材料，且阳离子混排程度较小。SEM分析表明，合成的正极材料粒度均匀，形貌为球形。电化学测试结果表明，所合成的材料具有良好的电化学性能和循环性能，首次放电容量为162．32mAh／g（2.8-4.3V），循环100次后的可逆容量保持率达到90.23％。     

锂离子电池正极材料LiCo0.5 Ni0.5 O2的颗粒生长研究

用高温固相反应合成了性能优良的LiCo0.5Ni0.5O2,并研究了合成过程中LiCo0.5Ni0.5O2的颗粒生长过程.LiCo0.5Ni0.5O2的粒径随预热温度、锂用量、焙烧温度和时间的增加而增加,不同合成条件下材料的粒径与生长时间呈对数线性关系.     

锂离子电池正极材料LiFe_(1-2x)Mn_xMg_xPO_4/C的电化学性能研究

通过高温固相合成法以MnCO3为锰源、(MgCO3)4·Mg(OH)·5H2O为镁源,葡萄糖为碳源,在氩气气氛下合成二元掺杂Mn、Mg的LiFe0.8Mn0.1Mg0.1PO4/C和LiFePO4/C正极材料,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱仪(FT-IR)进行结构表征,通过恒电流充放电实验研究了LiFe0.8Mn0.1Mg0.1PO4/C和LiFePO4/C电化学性能。结果表明,二元掺杂Mn、Mg的LiFe0.8Mn0.1Mg0.1PO4/C呈现橄榄石结构,无杂质产生。与未掺杂的LiFePO4/C相比,掺杂后LiFe0.8Mn0.1Mg0.1PO4/C提高了电导率,0.1C倍率下放电可逆容量为131mAh/g,表现出良好的电化学性能。     

层状Li0.7CoxMn1-xO2正极材料的合成与电性能研究

通过离子交换法在空气气氛中合成了具有O2型结构特征的掺Co3+型层状正极材料Li0.7CoxMn1-xO2, 用XRD、SEM、粒度分析和电性能测试等手段研究了煅烧温度和掺钴量对前驱体碱锰青铜及目标正极材料性能的影响.在900℃煅烧16h合成的前驱体Na0.7Co0.2Mn0.8O2具有P2型层状碱锰青铜结构特征, XRD特征峰尖锐.样品Li0.7Co0.2Mn0.8O2 在2.25～4.20V首次放电容量为162mAh·g-1, 循环40次后, 容量保持率在90%以上; 充放电曲线光滑, 仅存在2.70～2.90V唯一充放电平台, 在循环过程中未发生可逆相变.     

锂离子电池正极材料Li1.07Ni0.4Mn0.53O2的合成及电化学性能

采用氢氧化物共沉淀法制备出Ni0.43Mn0.57(OH)2前驱体,与Li2CO3混合制备了锂离子电池正极材料Li1.07Ni0.4Mn0.53O2,利用SEM、XRD对所得试样的形貌和晶体结构进行了表征,并研究了材料的电化学性能。结果表明:950℃下保温16h所得Li1.07Ni0.4Mn0.53O2具有良好的倍率性能和循环稳定性,2.75~4.2V、90mA/g(0.5C)下Li1.07Ni0.4Mn0.53O2的首次放电比容量达到127.11mAh/g,100次循环后容量保持率为98.99%。     

Synthesis,Structure and Magnetic Properties of Layered Perovskite Sm1.5SrBa0.5Mn2O7

The layered perovskite oxide Sm_1.5SrBa_0.5Mn₂O₇ was synthesized by the conventional method of co-precipitation. Its structure has been solved by powder X-ray diffraction. The diffraction patterns are consistent with the I4/mmm symmetry, with tetragonal lattice parameters a=3.8398(7) Å and c=20.3814(5) Å. The structure of Sm_1.5SrBa_0.5Mn₂O₇ is similar to Sr₃Ti₂O₇. Magnetic measurements were also performed in the temperature range 2–360 K. They showed a strong presence of antiferromagnetic interactions below Neel temperature T _N=25 K. The variation of the magnetization with the magnetic field in a temperature of 5 K was also analyzed. No saturation was observed up to the high applied magnetic field of 10 T.     

Synthesis and Properties of Layered Oxides LiCo_(1-x)Ni_xO_2

The mechanism of LiCo1-xNixO2(x=0, 0.5, 1) synthesis from carbonates or hydrates was studied by thermogravimetric analysis and X-ray diffraction to identify the medium and final products. The synthesis process from carbonates can be divided into two steps. Below 300℃cobalt carbonate and/or nickel carbonate decompose forming oxides. Over 300℃ Li2CO3 decomposes and reacts with Co and/or Ni oxides gradually, as a result Co++ and/or Ni++ areoxidized to Co+++ and/or Ni+++, finally LiCo1-xNixO2 forms. The proportion of cobalt tonickel in the starting mixture and atmosphere during synthesis affects the structure of products.LiCo1-xNixO2(x≤0.5) can be synthesized in air or oxygen and characterized by solid solutionof LiCoO2 and LiNiO2. LiNiO2 can be obtained only from hydrates and in oxygen atmosphere.LiNiOz and LiCo0.5Ni0.5O2 have higher first charge capacity than that of LiCoO2. Their discharge capacity reaches a level with that of LiCoO2 and has reasonable reversibility.     

Structural, Magnetic, and Dielectric Properties of PEG Assisted Synthesis of Mn0.5Ni0.5Fe2O4 Nanoferrites

The Mn_0.5Ni_0.5Fe₂O₄ nanoferrites with different morphology were prepared using the PEG assisted coprecipitation method. The two different iron salts were used for preparing the Mn–Ni ferrites with different morphologies by the coprecipitation air oxygenation method. Spherical and acicular nanoparticles were obtained by the calcination of the precursor. The phase, morphology, and crystallite size of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Magnetic properties were measured by the vibrating sample magnetometer (VSM). The saturation magnetization (M _s ), coercivity (H _c ) and Bohr magneton (n _B ) were found to be increased with an increase in effective anisotropy. The dielectric properties were found to decrease with the increased heterogeneity in the samples. The dielectric constant (ε′) and dielectric loss (tanδ) measured from 20 Hz to 1 GHz and variation in magnitudes show dependence on morphology of the prepared samples. Impedance spectroscopic measurements revealed that the electrical conduction in ferrite ceramics is due to resistance of grains interior.     

LiLaPO4-coated Li[Ni0.5Co0.2Mn0.3]O2 and AlF3-coated Li[Ni0.5Co0.2Mn0.3]O2 blend composite for lithium ion batteries

A blended composite of LiLaPO₄-coated Li[Ni_0.5Co_0.2Mn_0.3]O₂ and AlF₃-coated Li[Ni_0.5Co_0.2Mn_0.3]O₂ was tested as the cathode of lithium secondary batteries. The rate capability, cyclic performance, and thermal stability of the blended electrode were characterized and compared with pristine, AlF₃-coated, and LiLaPO₄-coated electrodes. The blended sample showed good cyclic performance and thermal stability, which implies that blending these two cathode coatings were effective in obtaining their advantages and lessening their weaknesses.     

镍氢电池负极材料V2Ti0.5Cr0.5Ni1-xMox(x=0.02~0.08)的结构和电化学性能

为了改善镍氢电池负极材料的循环稳定性能, 采用真空感应电弧熔炼炉制备了V₂Ti_0.5Cr_0.5Ni_1-xMo_x (x=0.02~0.08)合金, 分析了不同含量的Mo替代Ni之后对合金电极的组织结构及电化学性能的影响。研究结果表明, 电极材料主要由BCC结构的V基固溶体主相和TiNi二次相组成, 随着合金中Mo替代Ni含量x由0.02增加到0.08, 合金电极的放电容量先增加后降低, 合金电极的循环稳定性能以及电化学动力学性能先得到改善而后降低, 合金电极的综合性能均在x=0.04时达到最好。