Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries（LIBs）. However,the large volume changes upon repeated cycling always cause the pulverization of the e...Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries（LIBs）. However,the large volume changes upon repeated cycling always cause the pulverization of the electrode materials. Herein,we report the fabrication of uniform SnS_2@C hollow microspheres from hydrothermally prepared SnO_2@C hollow microspheres by a solid-state sulfurization process. The as-prepared hollow SnS_2@C microspheres with unique carbon shell,as electrodes in LIBs,exhibit high reversible capacity of 814 mA h g^（-1） at a current density of 100 mA g^（-1）,good cycling performance（783 mA h g^（-1） for 200 cycles maintained with an average degradation rate of 0.02% per cycle） and remarkable rate capability（reversible capabilities of 433 mA h g^（-1）at 2C）. The hollow space could serve as extra space for volume expansion during the charge-discharge cycling,while the carbon shell can ensure the structural integrity of the microspheres. The preeminent electrochemical performances of the SnS_2@C electrodes demonstrate their promising application as anode materials in the next-generation LIBs.展开更多
The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most ...The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most expensive component due to the use of a Pt catalyst. Apart from the ORR itself, the species transport to and from the reactive sites determines the performance of the PEFC. The effective transport properties of the species in the CCL depend on its nanostructure. Therefore a three-dimensional reconstruction of the CCL is required. A series of two-dimensional images was obtained from focused ion beam- scanning electron microscope （FIB-SEM） imaging and a segmentation method for the two-dimensional images has been developed. The pore size distribution （PSD） was calculated for the three-dimensional geometry. The influence of the alignment and the anisotropic pixel size on the PSD has been investigated. Pores were found in the range between 5 nm and 205 nm. Evaluation of the Knudsen number showed that gas transport in the CCL is governed by the transition flow regime. The liquid water transport can be described within continuum hydrodynamics by including suitable slip flow boundary conditions.展开更多
It is a great challenge to finely tune the morphology of iron oxides for energy storage. In this work, we introduced a facile hydrothermal method to obtain single crystalline hematite （α-Fe2O3） nano-coffee beans （...It is a great challenge to finely tune the morphology of iron oxides for energy storage. In this work, we introduced a facile hydrothermal method to obtain single crystalline hematite （α-Fe2O3） nano-coffee beans （NCBs） with the assistance of acetic acid. Interestingly, α-Fe2O3 nanos- tructures with this special morphology were formed under the effect of Ostwald ripening and oriented etching of H^＋ ions along [001] direction, which could be proved by the scanning electron microscope/transmission electron microscope and X-ray diffraction. After calcination at high temperature, the as-prepared α-Fe2O3 NCBs were used as potential anode ma- terials, showing a very high reversible capacity of 810 mA h g^-1 （0.2 C）, excellent cycling stability, and high-rate performance for lithium storage. Hence, in virtue of the good performances, the structural design of nanomaterials would be promoted in the fabrication of electrode materials for lithiumion batteries.展开更多
基金supported by the National Natural Science Foundation of China (51302323)the Program for New Century Excellent Talents in University (NCET-13-0594)the Innovationdriven Project of Central South University (2017CX001)
文摘Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries（LIBs）. However,the large volume changes upon repeated cycling always cause the pulverization of the electrode materials. Herein,we report the fabrication of uniform SnS_2@C hollow microspheres from hydrothermally prepared SnO_2@C hollow microspheres by a solid-state sulfurization process. The as-prepared hollow SnS_2@C microspheres with unique carbon shell,as electrodes in LIBs,exhibit high reversible capacity of 814 mA h g^（-1） at a current density of 100 mA g^（-1）,good cycling performance（783 mA h g^（-1） for 200 cycles maintained with an average degradation rate of 0.02% per cycle） and remarkable rate capability（reversible capabilities of 433 mA h g^（-1）at 2C）. The hollow space could serve as extra space for volume expansion during the charge-discharge cycling,while the carbon shell can ensure the structural integrity of the microspheres. The preeminent electrochemical performances of the SnS_2@C electrodes demonstrate their promising application as anode materials in the next-generation LIBs.
文摘The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most expensive component due to the use of a Pt catalyst. Apart from the ORR itself, the species transport to and from the reactive sites determines the performance of the PEFC. The effective transport properties of the species in the CCL depend on its nanostructure. Therefore a three-dimensional reconstruction of the CCL is required. A series of two-dimensional images was obtained from focused ion beam- scanning electron microscope （FIB-SEM） imaging and a segmentation method for the two-dimensional images has been developed. The pore size distribution （PSD） was calculated for the three-dimensional geometry. The influence of the alignment and the anisotropic pixel size on the PSD has been investigated. Pores were found in the range between 5 nm and 205 nm. Evaluation of the Knudsen number showed that gas transport in the CCL is governed by the transition flow regime. The liquid water transport can be described within continuum hydrodynamics by including suitable slip flow boundary conditions.
基金supported by the National Natural Science Foundation of China (21671096 and 21603094)the Natural Science Foundation of Guangdong Province (2016A030310376)+3 种基金Shenzhen Key Laboratory Project (ZDSYS201603311013489)the Natural Science Foundation of Shenzhen (JCYJ20150630145302231 and JCYJ20150331101823677)the 61~(th) China Postdoctoral Science Foundation (2017M610485)the Innovative Entrepreneurship Training Program of Southern University of Science and Technology (2016S14 and 2017X07)
文摘It is a great challenge to finely tune the morphology of iron oxides for energy storage. In this work, we introduced a facile hydrothermal method to obtain single crystalline hematite （α-Fe2O3） nano-coffee beans （NCBs） with the assistance of acetic acid. Interestingly, α-Fe2O3 nanos- tructures with this special morphology were formed under the effect of Ostwald ripening and oriented etching of H^＋ ions along [001] direction, which could be proved by the scanning electron microscope/transmission electron microscope and X-ray diffraction. After calcination at high temperature, the as-prepared α-Fe2O3 NCBs were used as potential anode ma- terials, showing a very high reversible capacity of 810 mA h g^-1 （0.2 C）, excellent cycling stability, and high-rate performance for lithium storage. Hence, in virtue of the good performances, the structural design of nanomaterials would be promoted in the fabrication of electrode materials for lithiumion batteries.
