Orthorhombic LiMnO2 cathode materials were synthesized successfully at lower temperature by sol-gel method. When LiMnO2 precursor prepared by sol-gel method was fired in air, the product was a mixture of spinel struct...Orthorhombic LiMnO2 cathode materials were synthesized successfully at lower temperature by sol-gel method. When LiMnO2 precursor prepared by sol-gel method was fired in air, the product was a mixture of spinel structure LiMn2O4 and rock-salt structure Li2MnO3, whereas in argon single-phase orthorhombic LiMnO2 could obtain at the range of 750℃ to 920℃. The substitution of Mn by Zn2+ or Co3+ in LiMnO2 led to the structure of LiMnO2 transiting to Qα-LiFeO2. The results of electrochemical cycles indicated that the discharged capacity of orthorhombic-LiMnO2 was smaller at the initial stages, then gradually increased with the increasing of cycle number, finally the capacity stabilized to certain value after about 10th cycles. This phenomenon reveals that there is an activation process for orthorhombic LiMnO2 cathode materials during electrochemical cycles, which is a phase transition process from orthorhombic LiMnO2 to tetragonal spinel Li2Mn2O4. The capacity of orthorhombic LiMnO2 synthesized at lower temperature is larger than that synthesized at high temperature.展开更多
Nanosized orthorhombic LiMnO2 was successfully synthesized using Mn2O3 and LiOH.H2O as starting materials.Not only the reaction temperature was lower, but the reaction time for synthesizing was notably shortened to 1 ...Nanosized orthorhombic LiMnO2 was successfully synthesized using Mn2O3 and LiOH.H2O as starting materials.Not only the reaction temperature was lower, but the reaction time for synthesizing was notably shortened to 1 h.In this hydrothermal process, the cations of the starting materials were capable of mixing and interacting in ionic scale, which resulted in the rapid formation of o-LiMnO2 powders at relatively low temperature. The particle size conformed by transmission electron microscopy is around 50-150 nm. Benefiting from its small particle size and good uniformity, the obtained o-LiMnO2 can reach the maximum discharge capacity of 163 mA-h.g^-1 at 0.1 C rate after several cycles. X-ray diffraction data and electrochemical properties suggested the phase transformation from orthorhombic LiMnO2 to defect-type spinel LiMn204 with minor Li2MnO3, which resulted in the capacity fading during cycling.展开更多
Two structure types of LiMnO 2 were synthesized by sol gel method and ion exchange method respectively.The results indicate that orthorhombic phase LiMnO 2 is more stable than layered LiMnO 2,o LiMnO 2 can be s...Two structure types of LiMnO 2 were synthesized by sol gel method and ion exchange method respectively.The results indicate that orthorhombic phase LiMnO 2 is more stable than layered LiMnO 2,o LiMnO 2 can be synthesized directly by sol gel methods followed by heat treated in argon,but layered LiMnO 2 was obtained only by indirect methods such as ion exchange method.In this paper,we first synthesized layered NaMnO 2 by the sol gel method,and then obtained layered LiMnO 2 by the ion exchange method.The phase constitution,chemical composition,and images of the products were tested by XRD,AAS (atomic absorption spectroscopy) and SEM.The electrochemical performances of the two structural types of LiMnO 2 are obviously different during the initial few cycles,but later they both have a good capacity retaining ability.The capacity of layered structure LiMnO 2 is higher than that of o LiMnO 2.展开更多
基金supported by the National Natural Science Foundation of China under grant No.59972026.
文摘Orthorhombic LiMnO2 cathode materials were synthesized successfully at lower temperature by sol-gel method. When LiMnO2 precursor prepared by sol-gel method was fired in air, the product was a mixture of spinel structure LiMn2O4 and rock-salt structure Li2MnO3, whereas in argon single-phase orthorhombic LiMnO2 could obtain at the range of 750℃ to 920℃. The substitution of Mn by Zn2+ or Co3+ in LiMnO2 led to the structure of LiMnO2 transiting to Qα-LiFeO2. The results of electrochemical cycles indicated that the discharged capacity of orthorhombic-LiMnO2 was smaller at the initial stages, then gradually increased with the increasing of cycle number, finally the capacity stabilized to certain value after about 10th cycles. This phenomenon reveals that there is an activation process for orthorhombic LiMnO2 cathode materials during electrochemical cycles, which is a phase transition process from orthorhombic LiMnO2 to tetragonal spinel Li2Mn2O4. The capacity of orthorhombic LiMnO2 synthesized at lower temperature is larger than that synthesized at high temperature.
基金supported by the National Natural Science Foundation of China under grant No.50372058.
文摘Nanosized orthorhombic LiMnO2 was successfully synthesized using Mn2O3 and LiOH.H2O as starting materials.Not only the reaction temperature was lower, but the reaction time for synthesizing was notably shortened to 1 h.In this hydrothermal process, the cations of the starting materials were capable of mixing and interacting in ionic scale, which resulted in the rapid formation of o-LiMnO2 powders at relatively low temperature. The particle size conformed by transmission electron microscopy is around 50-150 nm. Benefiting from its small particle size and good uniformity, the obtained o-LiMnO2 can reach the maximum discharge capacity of 163 mA-h.g^-1 at 0.1 C rate after several cycles. X-ray diffraction data and electrochemical properties suggested the phase transformation from orthorhombic LiMnO2 to defect-type spinel LiMn204 with minor Li2MnO3, which resulted in the capacity fading during cycling.
文摘Two structure types of LiMnO 2 were synthesized by sol gel method and ion exchange method respectively.The results indicate that orthorhombic phase LiMnO 2 is more stable than layered LiMnO 2,o LiMnO 2 can be synthesized directly by sol gel methods followed by heat treated in argon,but layered LiMnO 2 was obtained only by indirect methods such as ion exchange method.In this paper,we first synthesized layered NaMnO 2 by the sol gel method,and then obtained layered LiMnO 2 by the ion exchange method.The phase constitution,chemical composition,and images of the products were tested by XRD,AAS (atomic absorption spectroscopy) and SEM.The electrochemical performances of the two structural types of LiMnO 2 are obviously different during the initial few cycles,but later they both have a good capacity retaining ability.The capacity of layered structure LiMnO 2 is higher than that of o LiMnO 2.
