Using THF and water as solvent, piperazine as a template, a novel two dimensional layered zinc phosphate 1.5[Zn2(PO4)(HPO4)2]·H2O has been prepared solvothermally, and its structure is determined at 293K by Sieme...Using THF and water as solvent, piperazine as a template, a novel two dimensional layered zinc phosphate 1.5[Zn2(PO4)(HPO4)2]·H2O has been prepared solvothermally, and its structure is determined at 293K by Siemens Smart 1000 CCD diffractometer monoclinic, P21/c, a=0.81244(3)nm, b=2.61706(12)nm, c=0.83775(3)nm, β=110.981(2)°, V=1.66313(11)nm3, Z=4, R=0.0285, wR=0.0719. The structure con sists of vertex sharing ZnO4, HPO4, and PO4 tetrahedra, and double protonated organic cations, which results in formation of undulating 4 ring chains and 12 ring sheets. A network of hydrogen bonds involving both layer to layer and layer to amine interaction holds the phosphate layer together. CCDC: 200374.展开更多
Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O（s）were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurr...Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O（s）were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurred in the temperature range of T=368-374 K.The peak temperature of the dehydration was observed to be TD=（371.828±0.146）K by means of the heat-capacity measurement.The molar enthalpy and entropy of the dehydration were ΔDHm=（18.571±0.142）kJ/mol and ΔDSm=（49.946±0.415）J/（K·mol）,respectively.The experimental values of heat capacities for the solid（Ⅰ）and the solid-liquid mixture（Ⅱ）were respectively fitted to two polynomial equations by the least square method.The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.展开更多
LiFePO4 cathode material is synthesized by a simple solid-state reaction method with FePO42H20 as iron source and citric acid as reductive agent and carbon source. This study examines the effects of different oxidatio...LiFePO4 cathode material is synthesized by a simple solid-state reaction method with FePO42H20 as iron source and citric acid as reductive agent and carbon source. This study examines the effects of different oxidation routes to prepare FePO4＂2H20 on the electrochemical performance of as-synthesized LiFePO4. Iron phosphate was prepared by two routes from FeSO4＇7H20. One is the formation of Fe3（PO4）2 precipitate in the first step and subsequent oxidation to FePO4 precipitate. The other is the oxidation of ferrous to ferric ion firstly, and then to form FePO4 precipitate directly. The results indicate that substantial differences in the structure and electrochemical properties of LiFePO4 depend on the behavior of FePO4. Iron phosphate obtained through one step precipitation has a smaller particle size and more uniform particle distribution, which is demonstrated to be more applicable as the iron source to synthesize LiFePO4/C. As-prepared LiFePO4/C shows an excellent rate capability and cycle performance. The initial discharge capacities of 160.6 mAh/g and 107 mAh/g are achieved at 0.1 C and 10 C, respectively. The good capacity retention of 97% after 300 cycles is maintained at the rate of 5 C.展开更多
文摘Using THF and water as solvent, piperazine as a template, a novel two dimensional layered zinc phosphate 1.5[Zn2(PO4)(HPO4)2]·H2O has been prepared solvothermally, and its structure is determined at 293K by Siemens Smart 1000 CCD diffractometer monoclinic, P21/c, a=0.81244(3)nm, b=2.61706(12)nm, c=0.83775(3)nm, β=110.981(2)°, V=1.66313(11)nm3, Z=4, R=0.0285, wR=0.0719. The structure con sists of vertex sharing ZnO4, HPO4, and PO4 tetrahedra, and double protonated organic cations, which results in formation of undulating 4 ring chains and 12 ring sheets. A network of hydrogen bonds involving both layer to layer and layer to amine interaction holds the phosphate layer together. CCDC: 200374.
基金Supported by the National Natural Science Foundation of China(No.20673050).
文摘Low-temperature heat capacities of the solid compound NaCuAsO4·1.5H2O（s）were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K.A dehydration process occurred in the temperature range of T=368-374 K.The peak temperature of the dehydration was observed to be TD=（371.828±0.146）K by means of the heat-capacity measurement.The molar enthalpy and entropy of the dehydration were ΔDHm=（18.571±0.142）kJ/mol and ΔDSm=（49.946±0.415）J/（K·mol）,respectively.The experimental values of heat capacities for the solid（Ⅰ）and the solid-liquid mixture（Ⅱ）were respectively fitted to two polynomial equations by the least square method.The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.
基金supported by a project issued by the National Key Technologies R&D Program of China (2009BAG19B00)National High Technology Research and Development Program of China (SS2012AA110301)
文摘LiFePO4 cathode material is synthesized by a simple solid-state reaction method with FePO42H20 as iron source and citric acid as reductive agent and carbon source. This study examines the effects of different oxidation routes to prepare FePO4＂2H20 on the electrochemical performance of as-synthesized LiFePO4. Iron phosphate was prepared by two routes from FeSO4＇7H20. One is the formation of Fe3（PO4）2 precipitate in the first step and subsequent oxidation to FePO4 precipitate. The other is the oxidation of ferrous to ferric ion firstly, and then to form FePO4 precipitate directly. The results indicate that substantial differences in the structure and electrochemical properties of LiFePO4 depend on the behavior of FePO4. Iron phosphate obtained through one step precipitation has a smaller particle size and more uniform particle distribution, which is demonstrated to be more applicable as the iron source to synthesize LiFePO4/C. As-prepared LiFePO4/C shows an excellent rate capability and cycle performance. The initial discharge capacities of 160.6 mAh/g and 107 mAh/g are achieved at 0.1 C and 10 C, respectively. The good capacity retention of 97% after 300 cycles is maintained at the rate of 5 C.
