Characteristics of LiCoO2, LiMn2O4 and LiNi0.45Co0.1Mn0.45O2 as cathodes of lithium ion batteries

LiNi_0.45Co_0.10Mn_0.45O₂ was synthesized from Li₂CO₃ and a triple oxide of nickel, cobalt and manganese at 950 °C in air. The structures and characteristics of LiNi_0.45Co_0.10Mn_0.45O₂, LiCoO₂ and LiMn₂O₄ were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi_0.45Co_0.10Mn_0.45O₂ has a layered structure with hexagonal lattice. The commercial LiCoO₂ has sphere-like appearance and smooth surfaces, while the LiMn₂O₄ and LiNi_0.45Co_0.10Mn_0.45O₂ consist of cornered and uneven particles. LiNi_0.45Co_0.10Mn_0.45O₂ has a large discharge capacity of 140.9 mA · h/g in practical lithium ion battery, which is 33.4% and 2.8% above that of LiMn₂O₄ and LiCoO₂, respectively. LiCoO₂ and LiMn₂O₄ have higher discharge voltage and better rate-capability than LiNi_0.45Co_0.10Mn_0.45O₂. All the three cathodes have excellent cycling performance with capacity retention of above 89.3% at the 250th cycle. Batteries with LiMn₂O₄ or LiNi_0.45Co_0.10Mn_0.45O₂ cathodes show better safety performance under abusive conditions than those with LiCoO₂ cathodes. Foundation item: Project(50302016) supported by the National Natural Science Foundation of China; Project(2005037698) supported by the Postdoctoral Science Foundation of China     

不同污泥龄厌氧氨氧化菌的脱氮效能及其动力学特性

为研究不同污泥龄(SRT)条件下厌氧氨氧化菌的脱氮效能和动力学特性,采用一组SBR反应器研究梯度降低污泥龄过程中系统的NO2--N去除负荷(Nr)和NO2--N污泥负荷(Ns),并对各阶段厌氧氨氧化过程动力学特性进行分析.结果表明,污泥龄由21 d梯度降低到12 d,Nr由0.590 kg/(m3·d)降低到0.493 kg/(m3·d),单位MLVSS Ns由0.178 kg/(kg·d)提升到0.297 kg/(kg·d),系统整体的脱氮性能有所下降,但单位质量的厌氧氨氧化菌脱氮效率显著提升;采用莫诺(Monod)模型可以较好地模拟不同污泥龄运行阶段厌氧氨氧化菌的动力学行为,动力学分析表明,随着污泥龄的降低,NO2--N的最大比降解速率vmax由0.406 d-1提高到0.826 d-1,半饱和常数Ks由23.3 mg/L增加到95.3 mg/L,梯度降低污泥龄能够筛选纯化生长速率较快的厌氧氨氧化菌菌种,提升NO2--N的最大比降解速率,但厌氧氨氧化菌对底物的亲和性会逐渐变差,稳定性降低.     

LiNi0.4Co0.2Mn0.4O2与LiMn2O4共混正极材料电化学性能

为开发具有优良循环性能和安全性能的大型锂离子电池的正极材料,将不同比例的LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2和Li Mn2O4材料进行共混,研究了LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2和Li Mn2O4共混以及共混比例(10∶0、8∶2、7∶3、6∶4、5∶5、0∶10)对锂离子电池的首次放电性能、循环性能和倍率性能以及交流阻抗和循环伏安曲线的影响,并采用扫描电镜对电极材料进行了表征.研究结果表明,共混比例会影响材料的电化学性能,8∶2,7∶3和6∶4配比的混合材料的体积比容量、循环性能和倍率性能要好于纯LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2和Li Mn2O4材料.其中,8∶2配比的材料性能最好.     

BaZr0.9Y0.1O2.95/Na2SO4 composite with enhanced protonic conductivity

Heterogeneous composite BaZr_0.1Y_0.9O_2.95/Na₂SO₄ was designed and fabricated with Y-doped BaZrO₃ as matrix and Na₂SO₄ as dispersant by conventional powder processing to improve the total conductivity of barium zirconate. The electrical conduction of the composite was studied by electrical and electrochemical methods. Microstructure of the heterogeneous composite was examined by SEM. The experimewtal results show that the protonic conductivity of Y-doped BaZrO₃ is greatly improved upon incorporating Na₂SO₄ in the material. Microstructure observation indicates that a multiphase structure with Na₂SO₄ disperses at the grain boundaries of BaZr_0.1Y_0.9O_2.95. Electromotive force (EMF) measurements under fuel cell conditions reveal that the total ionic transport number of the composite is more than 0.9 at 750 °C. Funded by the National natural Science Foundation of China(No. 50872090)     

Self-Propagating High-Temperature Reduetive Synthesis of TiB2-Al2O3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis（SHS） method with reductive process from B2O3-TiO2-AI system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy （TEM） and high resolution electron microscopy （HREM） observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Effect of La doping on microstructure and ferroelectric properties of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films prepared by sol-gel method

The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.     

Preparation and characterization of Bi4Ti3O12 platelets by a novel low-temperature molten salt system

Bismuth titanate (Bi₄Ti₃O₁₂) platelets were prepared by molten salt method in a new salt system of CaC_l2-NaCl at 650–750 °C, using bismuth nitrate pentahydrate (Bi(NO₃)₃―H₂O) and titanium butoxide (Ti (OC₄H₉)₄) as raw materials. The synthesis temperature of Bi₄Ti₃O₁₂ platelets was decreased to 650 °C from 900–1100 °C. The phase compositions and crystalline morphology of Bi₄Ti₃O₁₂ platelets were investigated by XRD and SEM. The experimental results indicate that Bi₄Ti₃O₁₂ platelets containing tetragonal and orthorhombic phase with the size of 1–3 μm can be synthesized at 650 °C for 2 h, and the orthorhombic phase becomes the dominant phase at 750 °C for 5 h. The size and proportion of Bi₄Ti₃O₁₂ platelets increase with the increment of the calcining temperature and holding time. The proportion of platelets increases to about ninety percent, and the platelets grow up to about 3–10 μm at 750 °C for 5 h from 1–2 μm at 650 °C for 2 h. This technical route provides a new low-temperature molten salt system for preparing platelets by molten salt methods.     

Nanocomposite films of V<Subscript>2</Subscript>O<Subscript>5</Subscript>−MoO<Subscript>3</Subscript> xerogel with poly ethylene oxide intercalation

Poly ethylene oxide (PEO)_x−V₂O₅−V₂O₅−MoO₃ (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD, TG-DTA, FTIR, etc. The results show that V₂O₅−MoO₃ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement indicates that the intercalation of PEO improves insertion/extration properties of Li⁺ ions in the interlayer. ZHENG Jin-xia: Born in 1976 Funded by the National Natural Science Foundation of China (No. 50172036) and Natural Science Foundation of Hubei Province(No. 2001ABB083)     

Molar heat capacities of La2Mo2O9 and La1.9Sr0.1MO209-δ

The molar heat capacities of La2Mo209 and La1.9Sr0.1MO209-δ were obtained using the differential scanning calorimetry （DSC） technique in a temperature range from 298 to 1473 K. The DSC curve of La2Mo209 showed an endothermal peak around 834 K corresponding to a first-order monoclinic-cubic phase transition, and the enthalpy change accompanying this phase transition is 5.99 kJ/mol. No evident endothermal peak existed in the DSC curve of La1.9Sr0.1MO209-δ, but a broad thermal anomaly existed in its heat capacity curve at around 832 K. In addition, the heat capacity values of La2Mo209 and La1.9Sr0.1MO209-δ began to decrease at 1196 and 1330 K, respectively. The non-transitional heat capacity values of La2Mo209 and La1.9Sr0.1MO209-δ were formulated using multiple regression analysis in two temperature ranges.     

Synthesis and characterization of (PEO)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>−(V<Subscript>0.85</Subscript>Mo<Subscript>0.15</Subscript>)<Subscript>2</Subscript>O<Subscript>5</Subscript> nanocomposite films

(PEO) _x −(V_0.85Mo_0.15)₂O₅(x=0,0.5,1.0) nanocomposite films were prepared by a modified sol-gel method. The structure of the films was analyzed by XRD, and the DC electrical conductivity. Cyclic voltammogram and optical spectral transmittance were investigated. The results show that the (V_0.85Mo_0.15)₂O₅ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1.7897 nm at x=1.0. The introduction of MoO₃ improved the DC electrical conductivities of the films due to the generation of V₄₊ to maintain the electrical neutrality of the oxides. PEO intercalated in the interlayer of (V_0.85Mo_0.15)₂O₅ oxides has interaction with the oxides, enhancing the amount of Li⁺ ions inserted into the interlayer of the oxides. Moreover, the intercalation of PEO into the interlayer of (V_0.85Mo_0.15)₂O₅ oxides improved the cathodic electrochromic property in near ultraviolet region and anodic electrochromic property in visible range. JIANG Cong-sheng: Born in 1963 Supported by the Science Foundation of Hubei Province (Grant No. 2001ABB083)     

Luminescent properties of BaO-La2O3-B2O3 glasses with dopant

The luminescent properties of glasses synthesized in air atmosphere by conventional high temperature process were stud{ed. The emissions spectra of Eu^2 and Eu^3 were observed in BaO-La2O3-B2O3-Eu2O3 glasses.The results show that the broad emission peaks at 430 nm correspond to 5d→4f emission transition of Eu^2 , the sharp emission peaks at 592, 616, 650 and 250 nm correspond to 5^D0→1Fj(j=1--4) emission transition of Eu^3 ,respectively, which indicates that the BaO-La2O3a-B2O3-Eu2O3 glass can convert ultraviolet and green omponents of sunlight into blue and red light so as to increase the intensity of blue and red light, respectively. The luminescent in--tensity of Eu^2 increases with increasing the molar ratio of Tb^3 in BaO-La2O3-B2O3-Eu2O3a-Tb4O3 glasses, whereas the luminescent intensity of Eua^3 decreases. So the luminescent intensity of Eu(Ⅲ,Ⅱ) is influenced by Tb^3 .These phenomena can be explained by electron transfer mechanism; Eu^3 (4f6) Tb^3 (4f^8)→Eu^2 (4f′) Tb^4 (4f′). Taking advantage of the luminescent properties of BaO-La2O3-B2O3-Eu2O3 glasses, light-conversion glass for agriculture can be produced.     

Dielectric Properties of B2O3 Doped MgTiO3-CaTiO3 System Ceramics

The dielectric ceramics with a main crystal phase of MGTiO3 and additional crystal phase of CaTiO3 were prepared by the conventional electronic ceramics technology .the strucures of MgTiO3 are ilmenitetype,and belong to hexagonal syngony.the ratio of MgTiO3 to Ca TiO3 doping on the dielectric properties of MGTiO3-CaTiO3(MCT)ceranics were inrestigated.the addition of B2O3 decreases the sintering temperatnre and results in rapid desification without obrious negative effect on the Q values of the system(Q=1/tan ).B2O3 exists as liquid phase in the sintering process,promoting the reactions as a singering agent.     

Orientation of Bi<Subscript>3.2</Subscript>La<Subscript>0.8</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> ferroelectric thin films with different annealing schedules

Fatigue-free Bi_3.2La_0.8Ti₃O₁₂ ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of the films without the preannealing.     

Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating

LiCo_1/3Ni_1/3Mn_1/3O₂ was coated by a layer of 1.0 wt% CeO₂ via sol-gel method. The bared and coated LiMn_1/3Co_1/3Ni_1/3O₂ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure, only coating on the surface; the 1.0 wt% CeO₂-coated LiCo_1/3Ni_1/3Mn_1/3O₂ exhibits better discharge capacity and cycling performance than the bared LiCo_1/3Ni_1/3Mn_1/3O₂. The discharge capacity of 1.0 wt% CeO₂-coated cathode is 182.5 mAh·g⁻¹ at a current density of 20 mA·g⁻¹, in contrast to 165.8 mAh·g⁻¹of the bared sample. The discharge capacity retention of 1.0 wt% CeO₂-coated sample after 12 cycles reaches 93.2%, in comparison with 86.6% of the bared sample. CV results show that the CeO₂ coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte, thus enhance the electrochemical performance of the coated material.     

Synthesis and characterization of Mg3(PO4)2-coated Li1.05Ni1/3Mn1/3Co1/3O2 cathode material for Li-ion battery

Mg₃(PO₄)₂-coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode materials were synthesized via co-precipitation method. The morphology, structure, electrochemical performance and thermal stability were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), charge/discharge cycling and differential scanning calorimeter (DSC). SEM analysis shows that Mg₃(PO₄)₂-coating changes the morphologies of their particles and increases the grains size. XRD and CV results show that Mg₃(PO₄)₂-coating powder is homogeneous and has better layered structure than the bare one. Mg₃(PO₄)₂-coating improved high rate discharge capacity and cycle-life performance. The reason why the cycling performance of Mg₃(PO₄)₂-coated sample at 55 °C was better than that of room temperature was the increasing of lithium-ion diffusion rate and charge transfer rate with temperature rising. Mg₃(PO₄)₂-coating improved the cathode thermal stability, and the result was consistent with thermal abuse tests using Li-ion cells: the Mg₃(PO₄)₂ coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cells containing the bare Li_1.05Ni_1/3Mn_1/3Co_1/3O₂. Funded by the National Natural Science Foundation of China (No. 20273047)     

Structure and electrochemical properties of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>−<Emphasis Type="Italic">x</Emphasis>F<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

LiMn₂O₄−_xF_x prepared by the sol-gel method has a perfect crystal formation. The crystal particle size of the material was medium and distributed uniformly. The substitution of F for O increased the specific capacity of the material at the cost of the cycleability. The explanation of this results is that the F decreases the valence of Mn, that is, more Mn³⁺ and less Mn⁴⁺ exist in the material. The increase of Mn³⁺ will improve the initial specific capacity and Mn³⁺ is the original reason for Jahn-Teller effect that caused the poor cycleability of the cathode material by the micro-distortion of the crystal structure. In addition, the expanded measurement of the crystal lattice is also the reason for the poor cycleability. Therefore, the results of F-substitution and cation-substitution are opposite. If the two methods are combined, they can compensate the inability each other and the satisfactory results may be obtained. XIA Jun-lei: Born in 1977 Funded by the National Natural Science Foundation of China (No. 59972026)     

Preparation and microstructure of glass-ceramics and ceramic composite materials

The technology and microstructure of glass-ceramics and ceramic composite materials were studied. A suitable ceramic body was chosen on the basis of the sintering temperature of CaO-Al2O3-SiO2 system glass-ceramics. According to the expansion coefficient of the ceramic body, that of CaO-Al2O3-SiO2 system glass-ceramics was adjusted, fl-wollastonite was found present as the major crystalline phase in glass- ceramic. The CaO-Al2O3-SiO2 system glass-ceramic layer and ceramic body could be sintered together by adjusting the sintering period. The compositions of glass-ceramic layer and ceramic body diffuse mutually at 1 100 ℃, resulting in an interface between them. To achieve good sintered properties of glass-ceramics and the chosen ceramic body, at least a four-hour sintering time is used.     

基于双金属MOFs 制备Co3O4/In2O3 复合物及其气敏性能的研究

以硝酸铟(In(NO₃)₃·xH₂O)、对苯二甲酸(H₂BDC)、六水合硝酸钴(Co(NO₃)· 6H₂O) 为原料, 首先采用一锅油浴法合成了含有Co²⁺ 的铟基金属有机框架材料(MOFs) Co²⁺/CPP-3(In) 材料, 然后在450 ℃ 下焙烧制备Co₃O₄/In₂O₃ 复合物气敏材料, 将Co₃O₄/In₂O₃ 复合物的粉体制作成传感器, 并对其气敏性能进行研究。利用扫描电子显微镜和X 射线衍射仪(XRD) 对双金属MOFs Co²⁺/CPP-3(In) 材料和Co₃O₄/In₂O₃ 复合物进行表征, 采用静态配气法测试其气敏性能。结果表明, Co₃O₄/In₂O₃(n_Co : n_In = 0.4 : 1) 样品的形貌保留了其MOFs 前驱体的棒状结构, 棱柱形框架更为突出, 表面呈凹陷状, 棒体中间粗两边细, 六角截面和棒体均布满了孔洞。结合EDX 和XRD 表征结果, Co²⁺/CPP-3(In) MOFs 前驱体完全转化成Co₃O₄/In₂O₃ 复合物; Co₃O₄/In₂O₃(n_Co : n_In = 0.4 : 1) 复合物在 70 ℃ 下对5×10^-6 H₂S 的气敏性能最优, 响应值达到153, 是同条件下纯备In₂O₃对H₂S 响应值的5 倍, 并且有较好的重复性、选择性和稳定性。     

Nonselective etching of GaN/AlGaN heterostructures by Cl<Subscript>2</Subscript>/Ar/BCl<Subscript>3</Subscript> inductively coupled plasmas

A systematic study of the nonselective and smooth etching of GaN/AlGaN heterostructures was performed using Cl₂/Ar/BCl₃ inductively coupled plasmas (ICP). Nonselective etching can be realized by adjusting the BCl₃ ratio in the Cl₂/Ar/BCl₃ mixture (20%–60%), increasing the ICP power and dc bias, and decreasing the chamber pressure. Surface morphology of the etched heterostructures strongly depends on the gas chemistry and the chamber pressure. Specifically, with the addition of 20% BCl₃ to Cl₂/Ar (4∶1) gas mixture, nonselective etching of GaN/Al_0.28Ga_0.72N heterostructures at high etch rate is maintained and the surface root-mean-square (rms) roughness is reduced from 10.622 to 0.495 nm, which is smoother than the as-grown sample. Auger electron spectroscopy (AES) analysis shows that the effective removal of residual oxygen from the surface of AlGaN during the etching process is crucial to the nonselective and smooth etching of GaN/AlGaN herterostructures at high etch rate.     

Synthesis and characterization of hydroxylated fullerene epoxide—an intermediate for forming fullerol

A new C₆₀ derivative—hydroxylated fullerene epoxide [C₆₀ (OH) _x (O) _y ] was prepared by the reaction of C₆₀ benzene solution with aqueous NaOH and H₂O₂ in the presence of tetrabutylammonium hydroxide (TBAH) as the catalyzer. The structure of hydroxylated fullerene epoxide was characterized by FT-IR, NMR and MS, and it was found that it is easy to hydrolyze to fullerol. Project supported by the Nonferrous Metals Industrial Corporation of China Synopsis of the first author Li Tianbao, doctoral student, born in 1965, major in Fullerence Chemistry and Materials.