Characterization and optimized electrochemical performances of LiFe(1-2x)ZrxPO4/C nanocomposites as cathode materials for lithium-ion batteries

A series of nanocomposite LiFe(1-2x)ZrxPO4/C (x = 0.01,0.02, 0.03, 0.04, 0.06) were prepared by carbon thermal reduction method. With this strategy, the Li3PO4 impurity phase can be obviously reduced in the Zr-doped samples and the electrochemical performance is obviously improved by Zr doping compared with the undoped one. The best electrochemical performances were observed in LiFe(0.92)Zr(0.04)PO4/C as well as good cycle stability.     

锂离子电池LiFe0.7Mn0.3PO4-C复合正极材料的制备与表征

采用固相反应法制备了LiFe0.7Mn0.3PO4-C复合材料。用x射线衍射、扫描电镜和电化学测试对符合材料的结构、形貌和电化学性能进行了研究。结果表明，LiFe0.7Mn0.3PO4-C具有单一的橄榄石结构,碳的加入影响了LiFe0.7Mn0.3O4的表面形貌。LiFe0.7Mn0.3PO4-C复合材料的颗粒大小在100-200nm之间，碳均匀地包覆在LiFe0.7Mn0.3O4颗粒的表面．与LiFe0.7Mn0.3O4相比，LiFe0.7Mn0.3PO4-C复合材料具有更高的可逆比容量、更好的循环性能：0.1C放电时LiFe0.7Mn0.3O4-C复合材料的可逆容量达到141mAh／g，60次循环后平均每次循环的容量损失只有0．19％，而相同条件下60次循环后LiFe0.7Mn0.3O4平均每次循环的容量损失为0．53％，表明碳的加入有效地改善了LiFe0.7Mn0.3O4的电化学性能。     

碳含量对LiFe0.3Mn0.6Co0.1PO4/C材料电化学性能的影响

详细研究了原材料中蔗糖添加量对LiFe0.3Mn0.6Co0.1PO4/C复合材料电化学性能的影响。成品材料中碳掺杂量过多,会导致碳层锂离子扩散速度减慢,从而限制材料的容量;成品材料中碳含量太少,不仅材料的电子导电性不足,而且颗粒偏大,也不利于电化学性能。研究证实,原材料中最佳蔗糖添加量为8%(质量分数)。     

无钴镍基正极材料LiNi_(0.7)Mn_(0.3)O_2制备及性能研究

采用共沉淀-高温固相法合成正极材料LiNi0.7Mn0.3O2,利用X射线衍射分析(XRD)表征其结构、扫描电子显微镜(SEM)表征其形貌、X射线光电子能谱(XPS)表征其价态,最终确定了该材料最佳烧成温度为820℃。研究表明,该温度下合成的Li Ni0.7Mn0.3O2具有典型的α-NaFeO2型层状结构,颗粒形貌呈类球形且分布均匀;XPS数据表明,LiNi0.7Mn0.3O2中的Ni主要以+3价形态存在,Mn主要以+4价形态存在。室温条件下以0.2 C倍率在2.75~4.35 V的电压范围内充放电,首次放电比容量高达188.9 m Ah/g,70次循环后容量保持率为95.2%。     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2的合成及性能研究

以氢氧化钠为沉淀剂,采用共沉淀法合成了Ni1/3Co1/3Mn1/3(OH)2前驱体,前驱体和LiOH·H2O充分混合高温烧结制备了锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学性能测试对LiNi1/3Co1/3Mn1/3O2正极材料的结构、微观形貌及电化学性能进行了表征.XRD结果表明,所合成的LiNi1/3Co1/3Mn1/3O2物相单一无杂相,具有标准的α-NaFeO2型层状结构.SEM测试显示,颗粒粒度均一,粒径大约在0.5μm,粒径分布窄.以20mA/g电流密度放电,充放电电压在2.8～4.4 V之间,首次放电比容量达到181mAh/g,80次循环之后放电比容量仍然保持在172mAh/g;循环伏安测试显示,LiNi1/3Co1/3Mn1/3O2反应中主要是Ni2 /Ni4 、Co3 /Co4 2个电对在起作用,锰的价态保持不变,起到支撑结构的作用.     

Novel synthesis and electrochemical investigations of ZnO/C composites for lithium-ion batteries

For the first time, ZnO/C composites were synthesized using zinc glycerolate as a precursor through one-step calcination under a nitrogen atmosphere. The effect of the heat treatment conditions on the structure, composition, morphology as well as on the electrochemical properties regarding application in lithium-ion batteries are investigated. The products obtained by calcination of the precursor in nitrogen at 400—800 °C consist of zinc oxide nanoparticles and amorphous carbon that is in-situ generated from organic components of the glycerolate precursor. When used as anode material for lithium-ion batteries, the as-prepared ZnO/C composite synthesized at a calcination temperature of 700 °C delivers initial discharge and charge capacities of 1061 and 671 mAh g^?1 at a current rate of 100 mA g^?1 and hence 1.5 times more than bare ZnO, which reaches only 749/439 mAh g^?1. The native carbon improves the conductivity, allowing efficient electronic conductivity and Li-ion diffusion. By means of ex-situ XRD studies a two-step storage mechanism is proven.

     

石墨烯改善锂离子电池正极材料LiCoO_2电化学性能的研究

采用改性Hummers法制备了氧化石墨烯和通过化学还原法还原氧化石墨制得石墨烯,及以石墨烯作为正极材料LiCoO2的导电剂,并研究它们对锂离子电池电化学性能的影响。扫描电镜(SEM)和透射电镜(TEM)结果表明,石墨烯的表面褶皱使其能有效地包裹LiCoO2颗粒,形成面接触的导电界面,从而显著提高了导电性。充放电实验表明,石墨烯的加入有利于提高LiCoO2的电化学反应活性、放电容量和高倍率循环性能。相对于传统的炭黑,LiCoO2的放电容量在0.2 C下提高了10 m Ah/g。石墨烯/LiCoO2电池在1C倍率下,循环300次后,放电容量由145.0 m Ah/g衰减到137.8 m Ah/g,放电容量能保持初始容量的95.1%。石墨烯/LiCoO2电池在20 C倍率下的放电容量达到132.1 m Ah/g,是1 C放电容量的91.1%。     

Electrospinning synthesis of novel lithium-rich 0.4Li2MnO3·0.6LiNi1/3Co1/3Mn1/3O2 nanotube and its electrochemical performance as cathode of lithium-ion battery

In this study, a lithium-rich layered 0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂ nanotube cathode synthesized by novel electrospinning is reported, and the effects of temperature on the electrochemical performance and morphologies are investigated. The crystal structure is characterized by X-ray diffraction patterns, and refined by two sets of diffraction data (R-3m and C2/m). Refined crystal structure is 0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂ composite. The inductively coupled plasma optical emission spectrometer and thermogravimetric and differential scanning calorimetry analysis measurement supply reference to optimize the calcination temperature and heat-treatment time. The morphology is characterized by scanning and highresolution transmission electron microscope techniques, and the micro-nanostructured hollow tubes of Li-rich 0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂ composite with outer diameter of 200-400 nm and the wall thickness of 50-80 nm are synthesized successfully. The electrochemical evaluation shows that 0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂ sintered at 800 ℃ for 8 h delivers the highest capacity of the first discharge capacity of 267.7 mAh/g between 2.5 V and 4.8 V at 0.1C and remains 183.3 mAh/g after 50 cycles. The electrospinning method with heat-treatment to get micro-nanostructured lithium-rich cathode shows promising application in lithium-ion batteries with stable electrochemical performance and higher C-rate performance for its shorter Li ions transfer channels and stable designed structure.     

LiNi1/3Co1/3Mn1/3O2正极材料的合成及电化学性能研究

通过固相自引发基团置换反应——流变相法制备出层状LiNi1/3Co1/3Mn1/3O2正极材料,研究了不同烧结温度对材料的结构特性、微观形貌以及电化学性能的影响。结果表明,850℃煅烧20h的样品具有最佳的二维层状结构和阳离子有序度,产物颗粒呈球形,分布均匀,平均粒径约250nm。在2.8～4.3V区间,以80mA/g充放电,首次放电比容量为169mAh/g,30次循环后容量保持率为82.6%。将充电截止电压提高至4.4V,材料的前几次放电容量明显提高,以32mA/g充放电,10次循环后的放电比容量为174mAh/g,其后容量衰减加快,循环稳定性变差。     

Effects of MoS2 doping on the electrochemical performance of FeF3 cathode materials for lithium-ion batteries

Orthorhombic structure FeF₃ was synthesized by a liquid-phase method. The FeF₃/MoS₂ for the application of cathode material of lithium-ion battery was prepared through mechanical milling with molybdenum bisulfide. The structure and morphology of the FeF₃/MoS₂ were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of FeF₃/MoS₂ was studied by charge/discharge, cyclic voltammetry and electrochemical impedance spectra measurements. The results show that the prepared FeF₃/MoS₂ was typical orthorhombic structure, uniform surface morphology, better particle-size distribution and excellent electrochemical performances. The initial discharge capacity of FeF₃/MoS₂ was 169.6 mAh·g^− 1 in the voltage range of 2.0-4.5 V, at room temperature and 0.1 C charge-discharge rate. After 30 cycles, the capacity retention is still 83.1%.     

碳质材料对磷酸铁锂正极材料物理和电化学性能的影响

通过综述碳质材料对磷酸铁锂(LiFePO4)电极材料物理和电化学性能的影响,评述了碳质材料在不同LiFePO4/C复合电极材料中的作用及其优缺点.指出:炭膜的原位包覆和模板炭的引入,限制了LiFePO4晶粒的生长,进而提高了电极材料的电导率;而导电炭和石墨烯的引入,则是直接提高了电极材料的电导率;有机结合这两种碳质材料的复合方式将会极大改善电极材料的电化学性能.但是,为了提高电极材料的体积能量密度及其振实密度,应该最大限度地降低碳质材料在LiFePO4/C复合电极材料中的含量.     

LiFePO4-LiNi1/3Co（1/3）Mn1/3O2混合材料对锂离子电池性能的影响

通过流变相辅助高温固相碳热还原法及碳酸共沉淀法合成了LiFePO4/C复合材料及三元系锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2。将二者按一定比例经强力搅拌混合均匀,获得均匀的共混锂离子电池用正极材料。通过循环充放电测试、交流阻抗测试等研究了混合比例对混合材料电化学性能的影响。实验结果表明LiFePO4与LiNi1/3Co1/3Mn1/3O2通过混合,二者之间产生较强的协同作用,从而实现二者之间的优势互补。并且当混合比例为1∶2时,混合电极具有较好的低温性能、倍率性能及循环稳定性和较高的平均放电平台电压及比能量密度。     

LiFePO_4/graphene锂离子电池复合正极材料的制备与性能

通过溶胶-凝胶烧结法制备了LiFePO4/graphene锂离子电池复合正极材料。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、循环伏安(CV)以及各种电化学检测技术对合成材料的结构、形貌进行了表征。LiFePO4/graphene复合材料的表面上和其中的LiFePO4微小颗粒之间都有石墨烯,说明石墨烯与LiFePO4已很好地融合在一起,形成了具有三维空间结构的立体导电网络,大大地提高了复合材料的电子导电性能及减少了电荷转移电阻,从而充分发挥了活性材料的全部潜力。电化学测量表明LiFePO4/graphene的电化学性能比LiFePO4/C更好。LiFePO4/graphene具有较高的比容量和优良的大倍率性能,在0.1和5C电流充放时,LiFePO4/graphene的比容量分别为163.81和101.57 mAh/g,而LiFePO4/C仅为146.05和54.67mAh/g。LiFePO4/graphene也具有优良循环性能,0.5C循环100次,容量保持率为98.48%。     

Li2ZrO3包覆锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的制备及其电化学性能

富锂锰基材料因其具有较高的充放电比容量而备受关注。针对其首次库仑效率低、循环和倍率性能差的问题,将具有三维Li^+通道的锂离子导体Li2ZrO3引入至富锂锰基正极材料Li[Li0.2Ni0.2Mn0.6]O2的表面对其进行包覆改性研究。通过XRD,TEM,SEM,EDS综合分析可知:Li2ZrO3成功包覆到样品表面。包覆层厚度为3 nm(包覆量1%,质量分数)时复合材料的电化学性能得到显著提升。0.1 C(1 C=200 mAh·g^-1)倍率下首次放电比容量可达271.5 mAh·g^-1,库仑效率为72.4%,降低了首次不可逆容量损失;0.5 C下循环100周次后放电比容量为191.5 mAh·g^-1,容量保持率为89.5%,5 C倍率放电比容量为75 mAh·g^-1,倍率性能提升。适当厚度的均匀Li2ZrO3包覆层可在样品表面形成核壳结构使样品更稳定,减少表面副反应,阻止生成较厚SEI膜,这得益于Li2ZrO3本身的高电导率、高电化学稳定性和较好的锂离子传导性。     

Investigation of structural and electrochemical properties of Na2Mn2(SO4)3 cathode for sodium-ion batteries

Journal of Materials Science: Materials in Electronics - Electrode materials with the benefits of high working voltage, low cost, and environmental benign are needed for the realization of...     

锂离子电池正极材料LiNi0.5Mn1.5O4的研究现状

锂离子二次电池的研究不断深入,高电位正极材料的研究正日益受到重视。新型锂离子电池正极材料LiNi0.5Mn1.5O4嵌锂电位高达4.7V,能量效率高,循环性能好,在电动汽车、航空航天等领域具有良好的发展前景。综述了LiNi0.5Mn1.5O4的制备方法及近年来在提高其电化学性能方面的研究进展。     

Synthesis and electrochemical performance of LiV3O8/carbon nanosheet composite as cathode material for lithium-ion batteries

To improve the rate capability and cyclability of LiV₃O₈ cathode for Li-ion batteries, LiV₃O₈ was modified by forming LiV₃O₈/carbon nanosheet composite. The LiV₃O₈/carbon nanosheet composite was successfully achieved via a hydrothermal route followed by a carbon coating process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). TEM observations demonstrated that LiV₃O₈/carbon composite has a very flat sheet-like morphology, with each nanosheet having a smooth surface and a typical length of 400-700 nm, width of 200-350 nm, and thickness of 10-50 nm. Each sheet was surrounded by a thick layer of amorphous carbon. Electrochemical tests showed that the LiV₃O₈/carbon composite cathode features long-term cycling stability (194 mAh g⁻¹ at 0.2 C after 100 cycles) and excellent rate capability (110 mAh g⁻¹ at 5 C, 104 mAh g⁻¹ at 10 C, and 82 mAh g⁻¹ at 20 C after 250 cycles). Electrochemical impedance spectra (EIS) indicated that the LiV₃O₈/carbon composite electrode has very low charge-transfer resistance compared with pristine LiV₃O₈, indicating the enhanced ionic conductivity of the LiV₃O₈/carbon composite. The enhanced cycling stability is attributed to the fact that the LiV₃O₈/carbon composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact.     

锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2的制备与表征

以乙酸锂、硝酸镍、硝酸钴和乙酸锰为原料,通过高温固相法,分别采用一次烧结和二次烧结合成了LiNi1/3Co1/3Mn1/3O2。采用X射线衍射、扫描电镜分析以及电化学测试等手段对LiNi1/3Co1/3Mn1/3O2的微观结构、表面形貌和电化学性能进行了研究。结果表明,高温固相法能得到结晶良好的LiNi1/3Co1/3Mn1/3O2,但二次烧结提高了材料的I(003)/I(104)值,降低了c/a值,得到的LiNi1/3Co1/3Mn1/3O2具有更完善的层状结构和更优良的电化学性能。     

Synthesis and characterization of a new inverse spinel LiNi1/3Co1/3Mn1/3VO4 for lithium-ion batteries

An electrochemically active LiNi_1/3Co_1/3Mn_1/3VO₄ cathode material was synthesized by a citric acid:polyethylene glycol (CA:PEG) polymeric method, followed by calcination at 723 K for 5 h in air. X-ray diffraction (XRD) patterns showed the complete formation of a crystalline phase occurred when heated at 723 K. Scanning electron microscope (SEM) micrographs showed the various stages of morphology for the polymeric intermediates of the LiNi_1/3Co_1/3Mn_1/3VO₄ compound. Transmission electron microscope (TEM) imaging exposed that particle size ranged from ∼170 to 190 nm. The cells using LiNi_1/3Co_1/3Mn_1/3VO₄ as a cathode could be cycled between 2.8 and 4.9 V (vs. Li) at a current rate of 0.15C. The galvanostatic cycling study suggests that cycle stability and capacity retention were enhanced for LiNi_1/3Co_1/3Mn_1/3VO₄ prepared with a CA:PEG ratio of 3 : 1. The dQ/dV vs. voltage plots revealed the redox potentials and slower impedance growth for the synthesized LiNi_1/3Co_1/3Mn_1/3VO₄ cathode material.     

Synthesis and electrochemical properties of Nb-doped Li3V2(PO4)3/C cathode materials for lithium-ion batteries

Li₃V_2−xNb_x(PO₄)₃/C cathode materials were synthesized by a sol-gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li₃V₂(PO₄)₃, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li₃V_2−xNb_x(PO₄)₃/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li₃V_1.85Nb_0.15(PO₄)₃/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li₃V_2−xNb_x(PO₄)₃/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li₃V₂(PO₄)₃ system by enhancing structural stability and electrical conductivity.