FePO_4-coated Li[Li_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)]O_2 with improved cycling performance as cathode material for Li-ion batteries

Li[Li_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)]O_2 cathode materials were synthesized by carbonate-based co-precipitation method, and then, its surface was coated by thin layers of FePO_4. The prepared samples were characterized by X-ray diffraction(XRD), field emission scanning electron microscope(FESEM), energy-dispersive spectroscopy(EDS), and transmission electron microscopy(TEM). The XRD and TEM results suggest that both the pristine and the coated materials have a hexagonal layered structure, and the FePO_4 coating layer does not make any major change in the crystal structure. The FePO_4-coated sample exhibits both improved initial discharge capacity and columbic efficiency compared to the pristine one. More significantly, the FePO_4 coating layer has a much positive influence on the cycling performance. The FePO_4 -coated sample exhibits capacity retention of 82 % after 100 cycles at 0.5 ℃ between 2.0 and 4.8 V, while only 28 % for the pristine one at the same charge-discharge condition. The electrochemical impedance spectroscopy(EIS) results indicate that this improved cycling performance could be ascribed to the presence of FePO_4 on the surface of Li[Li_(0.2)Ni_(0.13)Co_(0.13)Mn_(0.54)]O_2 particle, which helps to protect the cathode from chemical attacks by HF and thus suppresses the large increase in charge transfer resistance.     

Structural evolution of mesoporous graphene/LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 composite cathode for Li-ion battery

Layered LiMO_2(M=Ni,Co,and Mn) is a type of promising cathode materials for high energy density and high work voltage lithium-ion batteries.However,the poor rate performance and low power density hinder its further applications.The capacity fade is related to the structural transformation in the layered LiMO_2.In this work,the structural changes of bi-material cathode composed of mesoporous graphene and layered LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2(NCM) were studied via in situ X-ray diffraction(XRD).During different C-rate charge-discharge test at the voltage range of 2.5-4.1 V,the composite cathode of NCM-graphene(NCM-G) reveals better rate performances than pure NCM cathode.The NCM-G composite electrode displays a higher rate capability of 76.7 mAh·g~(-1) at 5 C rate,compared to the pure NCM cathode of 69.8 mAh·g~(-1)discharge capacity.The in situ XRD results indicate that a reversible phase transition from hexagonal H1 to hexagonal H2 occurs in layered NCM material during 1 C chargedischarge process.With the current increasing to 2 C/5 C,the structure of layered NCM material for both electrodes reveals few changes during charge and discharge processes,which indicates the less utilization of NCM component at high C-rates.Hence,the improved rate performance for bi-material electrode is attributed to the highly conductive mesoporous graphene and the synergistic effect of mesoporous graphene and NCM material.     

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%。     

Electrochemical characterization of AlPO_4 coated LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode materials for high temperature lithium battery application

Aluminum phosphate(AlPO_4) was used to modify the surface of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2(NCM) cathode material.The surface structure and electrochemical properties of the coated materials were investigated by X-ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS).The results confirm the formation of aluminum-containing solid solution on the surface of NCM particles.An aluminum phosphate coating blocks the Li~+ insertion-extraction process in cells charged at high rates at room temperature,increasing surface film resistance and decreasing discharge capacity.However,an aluminum phosphate aids the formation of a stable solid electrolyte interface film on NCM surface and stabilizes the R_(ct) of cell as samples electrochemically cycled at 55℃.The electrochemical studies suggest that the initial columbic efficiency is significantly enhanced.An NCM sample coated with 1.0 wt% AlPO_4 delivers a higher discharge capacity and shows excellent capacity retention ability.     

锂离子电池正极材料LiNi_(0.5)Co_(0.5)O_2制备与电化学性能

采用球磨湿混和旋转合成相结合的新工艺制备了锂离子电池正极材料LiNi0.5Co0.5O2,并对材料进行了粒度、化学成分以及电化学性能测试。球磨湿混工艺能将原料混合均匀,并能有效地使粒度细化。旋转合成工艺能使混合料在均匀的温度场中进行反应,并使反应产物粒度均匀和成分均匀。制备的LiNi0.5Co0.5O2为单一的α-NaFeO2层状结构,粉末粒度分布范围窄,平均粒径约为8μm-10μm。电化学性能测试结果表明,在0．2mA/cm^2充放电流密度和3．0V－4．2V电压范围内,首次充电容量为173mAh/g,放电容量为148mAh/g。循环次数达30次时, 放电容量还有129mAh/g,循环稳定性良好。球磨湿混和旋转合成相结合的固相合成新工艺能制备出电化学性能良好的LiNi0.5Co0.5O2正极材料。     

Development of lithium-free P2-type high-sodium content cathode materials with enhanced cycle and air stability for sodium-ion batteries

The effect of partial substitution of Mg for Ni on a high-sodium and lithium-free layered P2-type Na_45/54Mg₆/₅₄Ni_12/54Mn_34/54O₂ cathode with high initial Coulombic efficiency and excellent cyclic stability has been investigated in this study.Based on the crystal structural analysis,the Mg doping can retain the P2 structure up to 4.3 V,thus restraining the detrimental phase transformation of P2-02during the Na-ion intercalation/dei...     

锂离子电池正极材料LiNi_(0.5)Co_(0.5)O_2制备与电化学性能

采用球磨湿混和旋转合成相结合的新工艺制备了锂离子电池正极材料 L i Ni0 .5Co0 .5O2 ,并对材料进行了粒度、化学成分以及电化学性能测试。球磨湿混工艺能将原料混合均匀 ,并能有效地使粒度细化。旋转合成工艺能使混合料在均匀的温度场中进行反应 ,并使反应产物粒度均匀和成分均匀。制备的 L i Ni0 .5Co0 .5O2 为单一的 α- Na Fe O2 层状结构 ,粉末粒度分布范围窄 ,平均粒径约为 8μm～ 10μm。电化学性能测试结果表明 ,在 0 .2 m A/cm2 充放电流密度和 3 .0 V～ 4 .2 V电压范围内 ,首次充电容量为 173 m Ah/g,放电容量为 14 8m Ah/g。循环次数达 3 0次时 ,放电容量还有 12 9m Ah/g,循环稳定性良好。球磨湿混和旋转合成相结合的固相合成新工艺能制备出电化学性能良好的L i Ni0 .5Co0 .5O2 正极材料。     

Electrochemical performance of LiNi_(0.5)Mn_(0.5)O_2 with different synthesis methods

Li Ni0.5Mn0.5O2 as a cathode material for Li-ion battery was prepared by the metal acetate decomposition method, sol–gel method, and carbonate co-precipitation method, respectively. The influences of synthesis methods on the physical and electrochemical behaviors of Li Ni0.5Mn0.5O2 were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrochemical tests. XRD patterns show that both the sol–gel and carbonate co-precipitation methods can form single phase of layered structure, while a trace of Ni O impurity is observed via the metal acetate decomposition method. SEM results show the as-prepared carbonate particle has a spherical morphology with an average diameter of 10 lm, consisted of primary nano-sized particles with particle diameter of200 nm. The sample prepared by the carbonate co-precipitation method exhibits the highest discharge specific capacity and the best cycling stability, which results from the steady homogeneity of precursor constant by the fixation of CO2-3group. It can deliver an initial discharge specific capacity of 186.3 m Ahág-1, and retain 170 m Ahág-1after100 cycles at a current rate of 20 m Aág-1in the voltage range of 2.5–4.7 V at 25 °C. Moreover, even at the high temperature of 55 °C, it still delivers a reversible specific capacity of 222.6 m Ahág-1with little capacity loss after 30 cycles.     

高振实密度球形LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2粉末的合成及性能

以共沉淀法制备的球形Ni_(0.5)Co_(0.3)Mn_(0.2)CO_3粉末为前驱体,按一定的比例将碳酸锂与前驱体混合,然后采用高温固相法合成高振实密度球形LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2正极材料.该材料的振实密度达到2.60 g/cm~3,与商品化LiCoO_2的密度相当.SEM分析表明, LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2正极材料与前驱体形貌有良好的继承性,均为理想的球形.XRD物相分析表明,在不同合成温度下的Li Ni_(0.5)Co_(0.3) Mn_(0.2)O_2产物均为具有α-NaFeO_2层状结构的纯相物质,在较高合成温度下所得材料的结晶度较高.电化学性能研究表明,在2.7～4.3 V的电压范围内,电池的放电比容量在0.2C倍率下为168.1 mA-h/g,在1C倍率下为157.6 mA-h/g;经50次循环后,两种放电条件下的电池容量保持率分别为95.1%和97.2%,显示出良好的电化学性能.     

快速共沉淀过程pH值对Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_2及LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2性能的影响

采用快速共沉淀法制备Ni0.8Co0.1Mn0.1(OH)2前驱体,利用前驱体与LiOH.H2O的高温固相反应得到锂离子电池层状正极材料LiNi0.8Co0.1Mn0.1O2,探讨pH值对材料结构和电化学性能的影响。通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对合成样品进行表征。结果表明,pH值为11.00~12.00时,合成的Ni0.8Co0.1Mn0.1(OH)2前驱体均无杂相;pH值为11.50时,合成的前驱体制备出的正极材料具有良好的电化学性能,0.1C倍率下首次放电比容量为192.4 mA.h/g;经过40次循环,容量保持率为91.56%。     

Synthesis and electrochemical performances of high-voltage LiNi_(0.5)Mn_(1.5)O_4 cathode materials prepared by hydroxide co-precipitation method

Spherical cathode material LiNi_(0.5)Mn_(1.5)O_4 for lithium-ion batteries was synthesized by hydroxide coprecipitation method. X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrochemical measurements were carried out to characterize prepared LiNi_(0.5)Mn_(1.5)O_4 cathode material. SEM images show that the LiNi_(0.5)Mn_(1.5)O_4 cathode material is constituted by micro-sized spherical particles(with a diameter of around 8 μm). XRD patterns reveal that the structure of prepared LiNi_(0.5)Mn_(1.5)O_4 cathode material belongs to Fd3m space group. Electrochemical tests at 25 °C show that the LiNi_(0.5)Mn_(1.5)O_4 cathode material prepared after annealing at 600 °C has the best electrochemical performances. The initial discharge capacity of prepared cathode material delivers 113.5 mAh·g~(-1) at 1C rate in the range of 3.50–4.95 V, and the sample retains 96.2%(1.0C) of the initial capacity after 50 cycles. Under different rates with a cutoff voltage range of 3.50–4.95 V at 25 °C, the discharge capacities of obtained cathode material can be kept at about 145.0(0.1C), 126.8(0.5C), 113.5(1.0C)and 112.4 mAh·g~(-1)(2.0C), the corresponding initial coulomb efficiencies retain above 95.2%(0.1C), 95.0%(0.5C), 92.5%(1.0C) and 94.8%(2.0C), respectively.     

Synthesis and electrochemical performance of La-doped Li3V2-xLax（PO4）3 cathode materials for lithium batteries

La-doped Li3V2-xLax(PO4)3 (x=0.01,0.02,and 0.03) cathode materials for lithium ion batteries were synthesized by the microwave-assisted carbothermal reduction method (MW-CTR).The structures and properties of the prepared samples were investigated by X-ray diffraction (XRD) and electrochemical measurements.The results showed that all the three Li3V2-xLax(PO4)3 samples had the same monoclinic structures and sharper diffraction peaks of the crystal plane compared with those of the undoped Li3V2(PO4)3.The initial charge/discharge specific capacity,coulomb efficiency,and discharge decay rate of all the three Li3V2-xLax(PO4)3 samples were superior to those of the undoped Li3V2(PO4)3 sample,and the Li3V1.98La0.02(PO4)3 sample exhibited the best features among the three La-doped Li3V2-xLax(PO4)3 samples.Electrochemical impedance spectroscopy (EIS) demonstrated that the Li3V1.98La0.02(PO4)3 sample had a lower charge transfer resistance and a higher Li ion diffusion coefficient compared with the undoped Li3V2(PO4)3 sample.     

LiOH-Li_2CO_3低共熔混合锂盐体系合成LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2

利用低共熔组成的0.24LiCO3-0.76LiOH混合锂盐体系,与钴、镍、锰的球形氢氧化物按1.1:1混合,无需前期球磨,直接经二段控温程序制备出锂离子正极材料LiNi1/3Co1/3Mn1/3O2。X射线衍射分析表明合成的Li(Ni1/3Co1/3Mn1/3)O2结晶度高,具有规整的层状α-NaFeO2结构,扫描电镜显示产物颗粒均匀,振实密度高达2.89g·cm-3,显著高于用单一锂盐制备的同样产品(2.4g·cm-3)。充放电测试表明,材料具有良好的电性能,首次充放电容量为176和166mhA·g-1,循环50次后,材料的电性能没有明显的衰减。     

Synthesis and electrochemical performance of YF<Subscript>3</Subscript>-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials for Li-ion batteries

Spinel LiMn₂O₄ cathodes were coated with 1 mol% YF₃. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn₂O₄ crystal. Transmission electron microscopy (TEM) showed that a compact YF₃ layer of 5–20 nm in thickness was coated onto the surface of LiMn₂O₄ particles. Scanning electron microscopy (SEM) observation showed that the YF₃ coating caused the agglomeration of LiMn₂O₄ particles. The cycling test demonstrated that the YF₃ coating can improve the electrochemical performance of LiMn₂O₄ at both 20 and 55°C. Moreover, YF₃-coated LiMn₂O₄ exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF₃-coated LiMn₂O₄ is more erosion resistant than the uncoated one.     

Electrochemical performance of SrF2-coated LiMn2O4 cathode material for Li-ion batteries

SrF2-coated LiMn2O4 powders with excellent electrochemical performance were synthesized. The electrochemical performance of SrF2-coated LiMn2O4 electrodes was studied as function of the level of SrF2 coating. With increasing the amount of the coated-SrF2 to 2.0% （molar fraction）, the discharge capacity of LiMn2O4 decreases slightly, but the cycleability of LiMn2O4 at elevated temperature is improved obviously. In view of discharge capacity and cycleability, the 2.0% （molar fraction） coated sample shows optimum cathodic behaviors. When being cycled at 55 ℃, as-repared LiMn2O4 remains only 79% of its initial capacity after 20 cycles, whereas the 2.0% （molar fraction） coated sample shows initial discharge capacity of 108 mA-h/g, and 97% initial capacity retention.     

Electrochemical performance of Li-rich cathode material,0.3Li_2MnO_3-0.7LiMn_(1/3)Ni_(1/3)Co_(1/3)O_2 microspheres with F-doping

Layered F-doped cathode materials 0.3 Li_2 MnO_3-0.7 LiMn_(1/3)Ni_(1/3)CO_(1/3))O_(2-x)F_x(x = 0, 0.01, 0.02, 0.03, 0.04,0.05) microspheres made up of nanosized primary grains were prepared through co-precipitation method. The sample of x = 0.02 demonstrates a large discharge capacity of226 mAh g~(-1) over 100 cycles at 0.1 C and excellent rate performance with discharge capacity of 96 mAh g-1 at 5.0 C and room temperature. Particularly, this material shows much enhanced electrochemical performances even at high temperature of 55 ℃. It delivers a quite high discharge capacity of 233.7 mAh·g~(-1) at 1.0 C with capacity retention as high as 97.9% after 100 cycles. The results demonstrate that the fluorine incorporation stabilizes the cathode structure and maintains stable interfacial resistances.     

新型锂离子电池正极材料Li3V2(PO4)3的合成及其性能

以LiOH·H2O、V2O5和NH4H2PO4为原料,C为还原剂,采用高温固相法合成了锂离子电池正极材料磷酸钒锂(Li3V2(PO4)3).考察了合成温度等条件对产物组成和晶相的影响.结果表明:随着焙烧温度的升高,杂相的衍射峰相对强度逐渐减弱,当煅烧温度达到800℃时,杂相衍射峰消失,所得样品为纯相的Li3V2(PO4)3样品;按Li、V、P的摩尔比为3:2:3将原料在800℃下焙烧24 h,合成得到正极材料.该材料在0.1 C充放电制度下,首次充电比容量达到135 mA·h/g,首次放电比容量130 mA·h/g,充放电效率达96.3%;经过20次循环后,放电容量仍然高达110 mA·h/g.对经过20次循环后的样品进行了X射线衍射分析,结果发现,经过20次循环后样品仍然具有单斜晶体结构,样品各主要衍射峰强度都急剧减弱,说明样品在充放电过程中晶体结构发生了变化;采用最小二乘法对样品充放电前后的晶胞参数进行了计算,发现样品在经过充放电循环后晶胞参数都有不同程度的增加,晶胞体积增大0.6%左右.     

对羟基苯甲酸酯的合成

以固载杂多酸盐TiSiW12O40／TiO2为多相催化剂，对以乙醇、丙醇、丁醇和对羟基苯甲酸为原料合成对羟基苯甲酸酯的反应条件进行了研究。实验表明：TiSiW12O40／TiO2是合成对羟基苯甲酸酯的良好催化剂，最佳反应条件为：醇酸摩尔比为4：1，催化剂用量为反应物料总量的2％，反应时间为2h。上述条件下，对羟基苯甲酸乙酯的产率为87．5％，对羟基苯甲酸丙酯的产率为89．2％，对羟基苯甲酸丁酯的产率为91．1％。     

Synthesis and properties of Na_(0.8)Ni_(0.4)Mn_(0.6)O_2 oxide used as cathode material for sodium ion batteries

A new P2-structured oxide Na_(0.8)Ni_(0.4)Mn_(0.6)O_2 was synthesized using a solid reaction method in which Na_2 CO_3, MnO_2 and NiO were used as starting materials.This oxide has a high amount of electrochemically active Ni and exhibits good electrochemical intercalation behavior of Na ions, including good rate capability and good cycle performance at both room temperature and elevated temperature. It displays two apparent voltage plateaus at about 3.6 and 3.3 V, and its discharge capacity reaches92 mAh·g~(-1) at 0.1 C in the voltage range of 2.0-4.0 V. At1.0 C, its discharge capacity reaches 85.3 mAh·g~(-1). After80 cycles at different current rates, the as-prepared sample exhibits good capacity retention. At elevated temperature of 55 ℃, the discharge capacity remains the same at low current rate of 0.1 C, but at high current rate of 1.0 C, the discharge capacity is a little lower than that at room temperature.