Hu Guorong

Influence of Ti4+ doping on electrochemical properties of LiFePO4/C cathode material for lithium-ion batteries

To improve the performance of LiFePO4, single phase Li(subscript 1-4x)Ti(subscript x)FePO4/C(x=0,0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti(superscript 4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti(superscript 4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7mA•h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti(superscript 4+).

Preparation and electrochemical performance of tantalum-doped lithium titanate as anode material for lithium-ion battery

Abstract The electrochemical performance of Ta-doped Li 4 Ti 5 O 12 in the form of Li 4 Ti 4.95 Ta 0.05 O 12 was characterized. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the structure and morphology of Li 4 Ti 4.95 Ta 0.05 O 12 . Ta-doping does not change the phase composition and particle morphology, while improves remarkably its cycling stability at high charge/discharge rate. Li 4 Ti 4.95 Ta 0.05 O 12 exhibits an excellent rate capability with a reversible capacity of 116.1 mA·h/g at 10 C and even 91.0 mA·h/g at 30 C . The substitution of Ta for Ti site can enhance the electronic conductivity of Li 4 Ti 5 O 12 via the generation of mixing Ti 4+ /Ti 3+ , which indicates that Li 4 Ti 4.95 Ta 0.05 O 12 is a promising candidate material for anodes in lithium-ion battery application.

Synthesis and characterization of layered Li(Ni1/3Mn1/3Co1/3)O2 cathode materials by spray-drying method

Spherical Li(Ni(subscript 1/3)Mn(subscript 1/3)Co(subscript 1/3))O2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1000℃ for 10h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni(subscript 1/3)Mn(subscript 1/3)Co(subscript 1/3))O2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900℃, Li(Ni(subscript 1/3)Mn(subscript 1/3)Co(subscript 1/3))O2 attains a reversible capacity of 153 mA•h/g between 3.00 and 4.35V at 0.2C rate with excellent cyclability.

Synthesis of spherical CoAl2O4 pigment particles with high reflectivity by polymeric-aerosol pyrolysis

Abstract Spherical cobalt blue particles with good reflectivity characteristics were synthesized by spray pyrolysis. Two different spray solutions were prepared to investigate the differences in the morphology and the reflectivity properties of cobalt blue particles. One was an aqueous solution, and the other was a polycation solution that was obtained by chemically modifying the aqueous solution with NH4OH. The cobalt blue particles prepared with the aqueous solution had an irregular morphology after heat treatment at 1000°C for 2 h. On the contrary, spherical and dense particles were obtained from the polycation solution. The spherical and dense cobalt blue particles showed remarkable improvement in reflectivity compared with that of irregular morphology particles as well as the commercial.

Preparation and property of spinel LiMn2O4 material by co-doping anti-electricity ions

Abstract LiMn2−xMxO4−yFy(x=0.05; y=0.05; M=Al, Co, Cr and Mg, separately), as the cathode material, was synthesized by the method of high temperature solid-state reaction in laboratory. The results of charge-discharge test show that the properties of LiMn1.95M0.05O3.95F0.05(M= Al, Mg) are obviously superior to those of LiMn2O4. Through the condition experiments on sintering temperature, it is found that the materials present the integrate crystal structure and favorable cycle performance at 800 °C. The research on the effects of different Mg2+ sources on the properties of LiMn2−xMgxO4−yFy shows that, with Mg(OH)2 and LiF as the reagents respectively offering Mg2+ and F−, LiMn1.95Mg0.05O3.95F0.05 synthesized has integrate crystal structure and its capacity hardly fades. The results of cyclic voltammetry indicate that the shape of two couples of redox peaks of the material synthesized by co-doping anti-electricity ions is more integrate and symmetrical than that of pure spinel LiMn2O4, which reveals that the co-doping material possesses preferable electrochemical reversibility.

Preparation of high active Pt/C cathode electrocatalyst for direct methanol fuel cell by citrate-stabilized method

Platinum nanoparticles supported on carbons (Pt/C, 60%, mass fraction) electrocatalysts for direct methanol fuel cell (DMFC) were prepared by citrate-stabilized method with different reductants and carbon supports. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization, and the form of carbon support has a great influence on electrocatalytic activity of catalysts. The citrate-stabilized Pt nanoparticles supported on BP2000 carbon, which was reduced by formaldehyde, exhibit the best performance with about 2 nm in diameter and 66.46 m^2/g(Pt) in electrocatalytic active surface (EAS) area. Test on single DMFC with 60% (mass fraction) Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm^2.

A Facile Route for Synthesis of LiFePO4/C Cathode Material with Nano-sized Primary Particles

Abstract A facile and practical route was introduced to prepare LiFePO4/C cathode material with nano-sized primary particles and excellent electrochemical performance. LiH2PO4 was synthesized by using H3PO4 and LiOH as raw materials. Then, as-prepared LiH2PO4, reduced iron powder and a-D-glucose were ball-milled, dried and sintered to prepare LiFePO4/C. X-ray diffractometry was used to characterize LiH2PO4, ball-milled product and LiFePO4/C. Differential scanning calorimeter-thermo gravimetric analysis was applied to investigate possible reactions in sintering and find suitable temperature for LiFePO4 formation. Scanning electron microscopy was employed for the morphology of LiFePO4/C. As-prepared LiH2PO4 is characterized to be in P21cn(33) space group, which reacts with reduced iron powder to form Li3PO4, Fe3(PO4)2 and H2 in ball-milling and sintering. The appropriate temperature for LiFePO4/C synthesis is 541.3-976.7 °C. LiFePO4/C prepared at 700 °C presents nano-sized primary particles forming aggregates. Charge-discharge examination indicates that as-prepared LiFePO4/C displays appreciable discharge capacities of 145 and 131 mA·h·g−1 at 0.1 and 1 C respectively and excellent discharge capacity retention.

微波合成法制备锂离子电池正极材料Li 2 FeSiO 4

We report a novel synthetic route for the preparation of the Li2FeSiO4 cathode material by microwave processing. The Li2FeSiO4 material was synthesized using mechanical ball-milling and subsequent microwave processing. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical methods. Properties of the prepared materials and electrochemical characteristics of the samples were investigated and compared to samples prepared by the conventional solid-state reaction. The obtained results indicated that highly pure Li2FeSiO4 material with uniform and fine particle size was quickly and successfully synthesized by microwave (MW) heating at 650 ℃ for 12 min. This compound showed high specific capacity and good cycle ability. The initial discharge capacity of the sample obtained by MW heating delivered 119.5 mAh•g^(-1) at 60 ℃ at a current density of C/20 rate (1C=160 mA•g^(-1)). After 10 cycles the discharge capacity maintained 116.2 mAh•g^(-1). The Li2FeSiO4 material displayed higher phase purity, better microstructure, and better electrochemical properties than the sample prepared by the conventional solid-state method.

Effect of electrolytic MnO2 pretreatment on performance of as-prepared LiMn2O4

To investigate the effect of electrolytic MnO2 (EMD) on the performance of LiMn2O4, several pretreatment methods, such as acid treating, presintering and impregnating with chromic salt, were used. The pretreated EMD and prepared LiMn2O4 were characterized by X-ray diffraction and inductively coupled plasma emission spectrometry. Charge and discharge tests of Li/LiMn2O4 batteries were also employed to evaluate electrochemical performance. The experimental results show that inorganic impurity contents in EMD decrease remarkably after acid treating; presintering EMD can remove adsorbent water and organic impurity, enlarge pore space and increase active reaction sites; pre-doping chromium in EMD can form more homogenous compound substance LiCr0.05Mn1.95O4, which shows better structural stability and capacity retention.

Preparation and Effects of Modoping on the Electrochemical Properties of Spinel Li 4 Ti 5 O 12 as Anode Material for Lithium Ion Batterylithiumion batteries; lithium titanate; anode materials; doping: Preparation and Effects of Modoping on the Electrochemical Properties of Spinel Li 4 Ti 5 O 12 as Anode Material for Lithium Ion Batterylithiumion batteries; lithium titanate; anode materials; doping

以硝酸铜、钼酸钠及氢氧化钠为原料,采用简单的水相沉淀法,在60℃下合成出钼铜矿（Cu3（MoO4）2（OH）2）.通过X射线衍射、扫描电镜、透射电镜、热重与差热分析、红外光谱及荧光光谱等测试手段对材料的微观结构、形貌、热稳定性及谱学特性进行表征分析.结果显示,制备的产物为结晶性良好的、至少一维是纳米的片状结构材料,属于单斜型（晶胞参数a=0.53863 nm,b=1.40006 nm,c=0.56003 nm）,其元素摩尔含量比约为3：2：10,与推测的分子式完全吻合.热重与差热分析数据表明Cu3（MoO4）2（OH）2纳米晶具有很好的热稳定性且起始分解温度为320℃.通过软件测得的d（021）面与d（ī21）面的晶间面距分别为0.435 nm与0.358 nm,与理论值基本相符.经测量,Cu3（MoO4）2（OH）2纳米晶具有强的荧光性质,在激发波长369 nm的作用下在530 nm表现为强发射峰.此外,还探讨了Cu3（MoO4）2（OH）2纳米晶的形成机理.