Vesicular lithium vanadium phosphate/carbon hollow mesoporous microspheres were fabricated using a facile polyvinylpyrrolidone-assisted aerosol-spray-assisted method and subsequent heat-treatment. While changing the c...Vesicular lithium vanadium phosphate/carbon hollow mesoporous microspheres were fabricated using a facile polyvinylpyrrolidone-assisted aerosol-spray-assisted method and subsequent heat-treatment. While changing the content of polyvinylpyrrolidone, we found that carbon content was adjustable on the surface of lithium vanadium phosphate. By optimizing the carbon content among the composites, the electrochemical performance can be enhanced significantly. The results of electrochemical performance tests suggested that the samples exhibited good cycle performance and high discharge capability in the voltages between 3.0-4.8 V. The observed excellent electrochemical performances could be attributed to the proper content of carbon coating and the vesicular hollow mesoporous microsphere structure, increasing the transmission rate of lithium ions and reducing the structural change during charging and discharging effectively.展开更多
Porous hollow Co3O4 microspheres have been synthesized from a mixed cobalt nitrate and urea solution through spray pyrolysis followed by calcination at 600 ℃ in air. This porous hollow Co3O4 is assembled by nanoparti...Porous hollow Co3O4 microspheres have been synthesized from a mixed cobalt nitrate and urea solution through spray pyrolysis followed by calcination at 600 ℃ in air. This porous hollow Co3O4 is assembled by nanoparticles and exhibits variable porosity depending on the amount of gas in the system. In pyrolysis process, urea continuously decomposes into gaseous components, which act as a template to control the porous structure. The amount of gas escaping from precursor droplets can directly influence the porosity of the microspheres and the size of the nanoparticles controlled by the ratio of urea to cobalt nitrate. Electrochemical measurements show that the performance of the porous hollow Co3O4 microspheres is related to the porosity and size of the nanopartides. The sample with optimal porosity delivers a high first charge capacity of 1,417.9 mAh·g^-1 at 0.2C （1C = 890 mA·g^-1）, and superior charge cycle performance of 1,012.7 mAh.g-1 after 100 cycles. In addition, the optimized material displays satisfactory rate performance of 1,012.4 mAh.g-1 at 1C after 50 cycles and 881.3 mAh·g^-1 at 2C after 300 cycles. Superior charge/discharge capacity, excellent rate performance and high yield achieved in this study is promising for the development of high-performance Co3O4 anode materials for lithium-ion batteries.展开更多
基金supported by the National Natural Science Foundation of China (Nos.21871005 and 21471006)the Recruitment Program for Leading Talent Team of Anhui Province, the Program for Innovative Research Team of Anhui Education Committee, the Research Foundation for Science and Technology Leaders and Candidates of Anhui Province, the programs for Science and Technology Development of Anhui Province (No.1501021019)Anhui Normal University talent training program (No.2014rcpyl2).
文摘Vesicular lithium vanadium phosphate/carbon hollow mesoporous microspheres were fabricated using a facile polyvinylpyrrolidone-assisted aerosol-spray-assisted method and subsequent heat-treatment. While changing the content of polyvinylpyrrolidone, we found that carbon content was adjustable on the surface of lithium vanadium phosphate. By optimizing the carbon content among the composites, the electrochemical performance can be enhanced significantly. The results of electrochemical performance tests suggested that the samples exhibited good cycle performance and high discharge capability in the voltages between 3.0-4.8 V. The observed excellent electrochemical performances could be attributed to the proper content of carbon coating and the vesicular hollow mesoporous microsphere structure, increasing the transmission rate of lithium ions and reducing the structural change during charging and discharging effectively.
基金This work was supported by the National Natural Science Foundation of China （NSFC） （Nos. 21471006 and 21271009）, the Programs for Science and Technology Development of Anhui Province （No. 1501021019）, the Recruitment Program for Leading Talent Team of Anhui Province, the Program for Innova- tive Research Team of Anhui Education Committee, and the Research Foundation for Science and Technology Leaders and Candidates of Anhui Province.
文摘Porous hollow Co3O4 microspheres have been synthesized from a mixed cobalt nitrate and urea solution through spray pyrolysis followed by calcination at 600 ℃ in air. This porous hollow Co3O4 is assembled by nanoparticles and exhibits variable porosity depending on the amount of gas in the system. In pyrolysis process, urea continuously decomposes into gaseous components, which act as a template to control the porous structure. The amount of gas escaping from precursor droplets can directly influence the porosity of the microspheres and the size of the nanoparticles controlled by the ratio of urea to cobalt nitrate. Electrochemical measurements show that the performance of the porous hollow Co3O4 microspheres is related to the porosity and size of the nanopartides. The sample with optimal porosity delivers a high first charge capacity of 1,417.9 mAh·g^-1 at 0.2C （1C = 890 mA·g^-1）, and superior charge cycle performance of 1,012.7 mAh.g-1 after 100 cycles. In addition, the optimized material displays satisfactory rate performance of 1,012.4 mAh.g-1 at 1C after 50 cycles and 881.3 mAh·g^-1 at 2C after 300 cycles. Superior charge/discharge capacity, excellent rate performance and high yield achieved in this study is promising for the development of high-performance Co3O4 anode materials for lithium-ion batteries.
